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How To Know

THE SEAWEEDS

An illustrated manual for identifying the more
common Marine Algae of both our Atlantic
and Pacific coasts with numerous aids for their
study.

E. YALE DAWSON. Ph.D.

WM. C. BROWN COMPANY PUBLISHERS

Dubuque. Iowa

Copyright © 1956 by
H. E. Jaques

Library of Congress Catalog Card Number 56-14426

SBN 697-04816-0 (Paper)
SBN 697-04817-9 (Cloth)

THE PICTURED-KEY NATURE SERIES

How To Know The-

AQUATIC PLANTS, Prescott, 1969

BEETLES, Jaques, 1951

BUTTERFLIES, Ehrlich, 1961

CACTI, Dawson, 1963

EASTERN LAND SNAILS, Burch, 1962

ECONOMIC PLANTS, Jaques, 1948, 1958

FALL FLOWERS, Cuthbert, 1948

FRESHWATER ALGAE, Prescott, 1954, 1970

FRESHWATER FISHES, Eddy, 1957, 1969

GRASSES, Pohl, 1953, 1968

GRASSHOPPERS, Heifer, 1963

IMMATURE INSECTS, Chu, 1949

INSECTS, Jaques, 1947

LAND BIRDS, Jaques, 1947

LICHENS, Hale, 1969

LIVING THINGS, Jaques, 1946

MAMMALS, Booth, 1949

MARINE ISOPOD CRUSTACEANS, Schultz, 1969

MOSSES AND LIVERWORTS, Conard, 1944, 1956

PLANT FAMILIES, Jaques, 1948

POLLEN AND SPORES, Kapp, 1969

PROTOZOA, Jahn, 1949

SEAWEEDS, Dawson, 1956

SPIDERS, Kaston, 1952

SPRING FLOWERS, Cuthbert, 1943, 1949

TAPEWORMS, Schmidt, 1970

TREES, Jaques, 1946

WATER BIRDS, Jaques-Ollivier, 1960

WEEDS, Jaques, 1959

WESTERN TREES, Baerg, 1955

Other subjects in preparation
Printed in United States of America

FOREWORD

HE most recent comprehensive monograph of the marine
algae of the combined Atlantic and Pacific coasts of
the United States is d splendid one, printed in quarto
and with some of the finest colored plates in the liter-
ature. The work is the more impressive when one
realizes that the author, W. H. Harvey, did his field
work without the aid of an automobile or a motor driven boat, made
his microscopic examinations without the aid of an electric light, and
made his own drawings on lithographic limestone. The time, — a cen-
tury ago. From the four hundred odd kinds of algae enumerated by
Harvey from the American shores the number of known species has
grown to about two thousand, with many still to be recognized and
named. Yet, with all of this expansion of knowledge there has come
no single modern monograph treating the North American seaweeds.
More conspicuous to many is the lack of any handbook designed to
aid, the amateur and the elementary student in identifying the com-
moner kinds of marine algae. It is toward filling a part of this need
that this little book is offered.

Inasmuch as the coasts of the United States are so very extensive
and the range of habitats and climates so varied, both on the Atlantic
and Pacific sides of the continent, a treatment of all of the species of
seaweeds in a small volume is impossible. Space does not permit
even a representative illustration for each of the many genera. How-
ever, our purpose is to provide a useful tool for the elementary stu-
dent of phycology, and with his needs in mind a selection has been
made of those plants which he is most likely to encounter wherever
he may be along the coasts of the United States. Algae which are
very small, or are of rare or localized occurrence, are omitted. Like-
wise, in the preparation of the key an effort has been made to present
those features which apply to the mature, well developed plants rather
than to juvenile or stunted forms which are not characteristic.

The author does not expect that the student will be completely
satisfied with the treatment, for occasionally there will be times when
the plant at hand is not to be found in this book, or when the illustra-
tion does not look very much like a particular specimen brought in
for study. On the other hand he does hope that this handbook will
serve the student in a large majority of cases to determine the names
of the seaweeds he has collected, wherever he lives or travels along
American Shores.

With few exceptions the illustrations have been drawn by the author
from actual specimens. The preparation of these was greatly facili-

tated by the herbarium material available at the Allan Hancock Founda-
tion, University of Southern California.

Los Angeles, California
October, 1955

^ ^^^ /C/^i.*^^^<i^>v^

Almost every one who walks along an ocean beach wonders about
the plant debris left by the waves. The need for a book offering
ready identification of the more evident species of marine algae is
apparent.

It is truly timely that Dr. Dawson, with his splendid experience
with these interesting plants, has given us this much-needed identifi-
cation manual.

Editor

CONTENTS

Page
The Vegetation of the Sea 1

How to Collect Seaweeds 6

Preservation of Seaweed Collections 10

What to Look For 16

Vegetative Structure 16

Reproductive Structure 20

Use of Pictured-Key 26

Additional References 27

Pictured-Key to the Common Genera of Macroscopic
Marine Algae of the United States 28

Marine Flowering Plants 180

Phylogenetic List of Genera and FamiHes 186

Index and Pictured-Glossary 192

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THE VEGETATION OF THE SEA

OUR-FIFTHS of the surface of our globe is covered by-
salt water, and since all of the multitudes of animal
inhabitants of this vast aquatic environment are ulti-
mately dependent upon the photosynthetic plants, we
may say that in one sense the marine plants are the
most important of all the groups of organisms on earth.

In the sea, extremes of climate are modulated by the water medium,
and the vastly predominant environment is one of monotonous dark-
ness and cold. Accordingly, the diversity of living things on the whole
is less than on the land, and while some groups are poorly repre-
sented, others are entirely lacking. Thus, whereas the highly devel-
oped mammals are sparsely represented in the sea and the insects
not at all, in the marine vegetation the seed plants and fungi are few
and the ferns and mosses absent. On the other hand, some of the
phyla of organisms present in the sea are absent on land, or much
less richly developed there. This is true of the several groups of plants
known as algae of which the great bulk of the marine vegetation is
composed.

With the exception of the bacteria and of a few parasitic and
saprophytic fungi, virtually all of the marine plants are autophytic, that
is to say, independent and capable of providing their own food by
means of photosynthesis. To do this they need two primary raw ma-
terials, namely, water, which is seldom in short supply, and CO^.
Energy for the process of photosynthesis must be suppHed by sunlight
which, however, is largely absent in the sea. Most of the marine en-
vironment is totally lacking in sunlight which penetrates, even in the
most exceptionally clear water, only to as much as three or four hun-
dred feet. Accordingly, these autophytic plants are restricted in the

IKTERTOAL PELAGIC

INFRATIDAL
J»7

'-]

0""^'°'' PHOTIC

ZONE

benthk: nvisoN

Fig. 1. Diagram of the general habitats of the plants of the sea.

HOW TO KNOW THE SEAWEEDS

immensity of the oceans to a relatively thin layer of illuminated sur-
face water and to the narrow intertidal and infratidal fringe within
this photic zone. In these places, however, they may be remarkably
abundant.

The general habitats of the plants af this illuminated portion of the
sea may be diagrammed as in Figure 1. The vegetable inhabitants of
the pelagic division, that is, of the water mass itself, are the phyto-
plankton, while those of the benlhic division, or the sea floor, are
what we may call the seaweeds, or attached algae.

The phytoplankton consists of free floating, unattached plants
which move about only as their water medium moves. With few
exceptions they are unicellular forms of microscopic size requiring
quite high magnification to render them visible (Fig. 2). Despite their
small size, their habitat in the surface waters of all of the oceans is
so vast and their numbers so great that they actually account for
more than 95% of the vegetation of the sea.

Several different kinds of or-
ganisms make up the phyto-
plankton (Fig. 2) of which may
be mentioned the diatoms, the
pigmented dinoflagellates, the
silicoflagellates, the coccohtho-
phores and a few blue-green
algae. Most abundant of these
constituents are the diatoms, of
which several million may
sometimes occur in a single
quart of sea water. These are
unicellular members of the
division Chrysophyta whose
protoplasm secretes a beauti-
fully sculptured, bivalved, si-
Hcious shell (Fig. 3). The shell
is basically Hke a pill-box in
structure, but often is marvel-
ously modified for flotation
where perpetuation of a species
depends upon the ability to re-
main in the photic zone.

Fig. 2.

Some representatives of the
phytoplankton.

A. A dinoflageiiate, Ceratium. B. A
diatom, Planktoniella. C. A coccolitho-
phore, Pontosphaera. D. A silicoflagellate,
Distephanus. All are drawn to the same
scale (X 225) and are shown against a
heavy outline which represents the point
of a dissecting needle.

HOW TO KNOW THE SEAWEEDS

Because of the tremendous
numbers of these tiny plants
in the sea, and of the per-
petual rain of their insoluble
silicious shells on the bot-
tom, great deposits accum-
ulate which may be hun-
dreds of feet deep. Some of
these deposits have been
raised above sea level and
form the beds of diatoma-
ceous earth such as occur
at Lompoc, California, and
are exploited commercially
for the making of fine scour-
ing compounds.

On account of the very
small size of the phytoplank-
ton organisms, the high mag-
nifications needed for view-
ing them, and the special
methods required in collect-
ing, preserving and exam-
ining them, they do not lend
themselves readily to study
by the amateur or elemen-
tary student and will not be
treated further in this ac-
count.

Fig. 3. Examples of two different forms of
plcnktonic diatoms.

A. Asterolampra, a broad, flot, disc-like
form. B. Chaetoceras, a very small-bodied
form with long hair-like modifications of
the silicious frustule to aid in flotation. Both
X 200.

HOW TO KNOW THE SEAWEEDS

Unlike the vegetation of the surface water masses of the oceans,
that of the illuminated sea floor and of the shore consists mostly of
readily visible plants of which some reach large size. Among these, to

be sure, there are mtiny
microscopic forms, includ-
ing littoral diatoms (Fig.
4) and minute blue-green
algae (Fig. 5) which some-
times form more or less
conspicuous macroscopic
colonies. These must be/
neglected here, however,
in favor of the three main
groups of seaweeds with
which we need be con-
cerned, namely, the Green
Algae (Chlorophyta), the
Brown Algae (Phaeophy-
ta) and the Red Algae
(Rhodophyta). The seed
plants, although of very
few kinds, are exceeding-
ly abundant in many
coastal habitats and will
be accounted for and il-

Fig. 4. Two examples of different forms of Instrated at the end of

littoral diatoms. lusiiaiea ui iiit? eiiu ui

A. An epiphytic, chain form, Grammatophora. thiS book.
B. A stalked form, Licmophora.

These three groups of algae which make up the vast majority of
the seaweeds are named because of the predominant colors which
their members commonly assume, and are technically distinguished
by the chemistry of their pigments. Thus, the Green Algae are char-
acteristically pigmented only by green chlorophyll, while the Brown
and Red Algae have their chlorophyll masked by other pigments. On
this account the Green Algae almost always appear green in color,
while the others may be neither brown nor red, depending upon the
relative dominance of the chlorophyll or of the masking pigments.
When the color is such as to leave one in doubt as to the group to
which a plant may belong, other characters must be taken into ac-
count in identification. Because of the difficulty experienced by most
students in recognizing according to color the main group to which
a seaweed belongs, the present key treats all of the Green, Brown

HOW TO KNOW THE SEAWEEDS

and Red Algae together, separating them from each other without par-
ticular regard to color.

c=

m

^

B

Fig. 5. Some examples of Blue-Green Algae.
A Lvngb/a sp. X 183. B. Oscillatoria sp., X 200. C. Brachytrichia sp., X 275.
D. Hormothamnion sp., X 330. E. Entophysalis sp., X 500. F. Calothnx sp., X 275.

HOW TO COLLECT SEAWEEDS

^ EA WEEDS rarely grow in the free floating state, but in-
stead are fixed firmly at their bases and remain station-
ary throughout life. Only in the Sargasso Sea north-
east of the Caribbean and in the Gulf of Thailand are
there sizable quantities of the brown alga Saiqassum.
(see Fig. 141) hving in the free floating state. Elsewhere
the seaweeds grow attached to the bottom or to each
other. Since an unstable bottom such as one of sand or mud is un-
favorable to the attachment of seaweeds, they are usually absent
from such substrates except in quiet bays and lagoons where agita-
tion is sUght. On surfy shores the algae are essentially confined to
rocky places where their firm attachments give them resistance *o
wave shock. This is especially true along the rugged, wave-swept
Pacific Coast where the collector rarely encounters the richly vege-
tated quiet bays or estuaries such as occur so frequently along the
Atlantic Coast.

The coasts of the United States offer a diversity of marine habitats
scarcely equalled by those of any other nation. This diversity is so
great that no single set of directions can be made suitable for a col-
lector among the Florida keys, another on Cape Cod and another on
Puget Sound. One can only make a few general remarks and sug-
gestions, leaving the rest to the adjustabiUty and ingenuity of the
American individual wherever he may be.

At the outset it is clear that one must get to the seashore to collect
seaweeds, but this is not always as simple as it may seem. Many of
our rocky shores abounding in algae ate subject to surf of varying
intensity whereby collecting is made difficult or impossible except at
times of lowest water. Accordingly, it is necessary to select a suitable
time for the collecting trip, depending upon the state of the tide. Tide
tables issued by the U. S. Coast and Geodetic Survey or by various
sporting goods houses for the use of fishermen should be consulted
for the times of suitable low water. The so called "minus tides" are
the best, but even with only moderately low water much can be done
if the surf is not too severe. The collector should plan to begin work
at the shore at least two hours before the time of low tide in order
to work the clearer water of the falHng tide and to select his material
successively from higher to lower levels while the plants are freshly
exposed and still wet and unshriveled from desiccation.

Collecting equipment on a rocky shore should consist of a pail or
two for carrying the specimens, a quantity of plastic bags for separating

Collecting Tools.

HOW TO KNOW THE SEAWEEDS

the larger species, and a number of small, screw-cap vials provided
with 3% formalin into which small but important specimens may-
be preserved from loss or mixing. For removing small plants from
rock surfaces a heavy knife or other scaping tool is used, while en-
crusting forms which adhere too
firmly may be obtained by using
a geologist's hammer for cracking
off pieces of the supporting rock.

At the upper levels one will find
a number of minute species on the
exposed rock surfaces, including
various crustose forms which the
initiate may overlook unless they
are pointed out to him. Lower
down, depending upon the amount
of exposure to desiccation, one
will encounter larger and smaller

fleshy, clumping forms grading into the densely matted turfs, or heavy,
continuous beds of algae at the lowest tide levels. It will not be enough
to look superficially over the array of seaweeds to outain a good col-
lection, for many species will be hidden under others or will occur only
in particular pools, in certain shaded crannies, along the edges of
surging tideways, or on the exposed faces of outermost rocks subject
to the heaviest surf. Many species will be found growing only as
epiphytes or as parasites on other, larger species and should be ob-
tained by selection of suitable portions of the host plants. Algal turfs
consisting of many species may be brought back as a mass to be
examined for their individual constituents in the laboratory. At low-
est water level the collector will profit by wading out (in hip boots
in cold areas) to look under overhanging rocks, in crannies and pools
for the various species which can endure only momentary exposure
to the atmosphere.

When the tide has begun to flow one must hasten to finish the
work at low levels before retracing steps inward. With the incoming
tide time may be taken to seek special pools and rocky habitats at
higher levels which have been passed over before, and there to find
additional species. Shaded cUffs subject to spray, the walls of sea
caves, the under edges of rocks in tide pools, high, warm pools pol-
luted by guano, and other such diverse habitats will all yield dif-
ferent species. Even pieces of dead shell or coral may exhibit a green-
ish cast indicating the presence of boring green algae.

After the selection of the attached algae from the intertidal rocks
has been completed there is yet another source of specimens which
should not be passed by. Especially at times of unfavorable tides one

HOW TO KNOW THE SEAWEEDS

may profit much from examining the beach drift which often accumu-
lates in quantity in coves or along sand beaches adjoining rocky areas.
It is among these cast specimens that many of the species of the
deeper, infratidal waters may be found and selected with much greater
ease than through the use of a boat and dredge. If driftweed is ex-
amined after a storm while the material is still fresh and has not been
exposed long to the bleaching and drying action of the sun and air,
many specimens in good condition may be selected.

Apart from rocky shore habitats the algologist finds many other
situations in which seaweeds may be found. Many areas in which
surf is light or absent, such as the sandy or muddy shores of bays,
lagoons and estuaries, will yield specimens. Such quiet habitats are
especially well populated in tropical regions, and within the range
of the mangrove the algal flora of its roots is an interesting one which
should not be overlooked. The piling of wharves and the rock or
concrete of artificial breakwaters will yield many species. Indeed,
along the vast sandy stretches of the Gulf of Mexico, these will be
the principal algal habitats. Even mobile objects may have their
seaweed floras. Thus, boat hulls will yield several species as may
also the backs of sea turtles and several kinds of crabs. Particular
species have even been found attached to the intersegmental grooves
of isopods parasitic on certain fishes.

Beyond the level of low tide, and apart from those cast ashore in
drift, the algae of infratidal waters must be obtained by means of
diving or by some manner of dredging. In very quiet, surfless waters
a collector may wade about observing the bottom by means of a glass-
bottom bucket and reaching specimens with ease. In depths of more
than three feet, observation is best afforded by a face plate and col-
lections made by placing specimens in a skiff as they are obtained
by the diver. In depths of more than ten feet the diver must be pro-
vided with breathing apparatus in order to spend the time below the
surface necessary for the selection of specimens. The "aqua-lung" has
recently become popular with skin-divers and its use may readily
be learned in most any area of warm, quiet water where these sports-
men thrive. In colder waters the diver must be provided with the
standard heavy diving suit and helmet. It is this heavy suit which is
normally used by the commercial seaweed collectors who harvest
Gelidium and other agar-yielding seaweeds from the infratidal beds
along the Pacific Coast.

Apart from those areas where skin-diving may be done comfort-
ably, the collecting of infratidal algae is best accomplished by the
use of a dredge handled by a powered winch on shipboard. The use
of various devices of this sort is described by Sverdrup, Johnson &

8

HOW TO KNOW THE SEAWEEDS

Fleming. The Oceans, Prentice-Hall, Inc., 1942, and may be observed
on ships operated by the several oceanographic institutions of the
country.

HARVESTING GELIDIUM.

PRESERVATION OF SEAWEED COLLECTIONS

HEN the day's collecting has been completed the speci-
mens should be preserved as quickly as possible to
prevent unnecessary deterioration. This is best ac-
compHshed at the shore by means of one or more
five-gallon tin cans. Sea water should be brought up
in a bucket and mixed with commercial 40% formal-
dehyde to obtain approximately a 3% solution. The
various plastic bags into which specimens have been separated may
then be partly filled with the preservative and tied. These bags, to-
gether with bulkier materials as well as small bottles of specimens
may all be placed in the can in preservative and provided with an
appropriate label. The tin of specimens may be closed and kept for
months without deterioration of the specimens or loss of color, while
the same specimens kept in glass jars exposed to hght would be
bleached and largely worthless in a few
days. The tin may, indeed, be sealed with
solder and boxed for shipment with ease
and without fear of damage to the con-
tents.

Of utmost importance in the preparation
of any collection is the provision of ade-
quate field data in the field collection
notebook, and the careful preparation of
labels. For this purpose all pertinent ob-
servations on the character of the habi-
tat, size and aspect of the various domi-
nant species, the major associations, water
temperature, substrate type, exposure, etc.,
should be recorded before leaving the field.
These data should be incorporated in the
permanent book of field notes, in which a
consecutive series of collection numbers is
tabulated.

Upon return to the laboratory the prep-
aration of specimens may begin at once,
although it is preferable to leave the ma-
terial in preservative for a few days time.
This applies particularly to certain species
which when fresh are damaged by being
immersed in tap water, but which are not

harmed by the same treatment after having remained a few days or
weeks in the formalin- sea water solution.

A Dredge.

10

HOW TO KNOW THE SEAWEEDS

It will be found most convenient to obtain one or more large por-
celain trays and a number of wide-mouthed jars of various sizes into
which to sort the specimens. After quickly washing with top water
the various species should be separated into the jars, each species
receiving a number which is Usted in the field notebook beneath the
field data previously recorded. Of each of the species, especially
the smaller or more delicate forms, appropriate portions should be
placed in small vials (4 dram shell vials) for future use in making
preparations for microscopic examination. These, of course, also re-
ceive in each case the same field number assigned to the remaining
material of a given species.

After the segregation of all of the species into separate containers
the drying may begin. Two methods may be employed depending
upon the nature of the specimens. Crustose specimens which have
been brought from the shore along with pieces of their substrate may
be dried directly in the air and preserved in the dry state in small
boxes of suitable size. Articulated, calcareous algae which are so
fragile and (or) so three dimensional as to suffer badly from pressing,
should be treated in the same way, or, preferably, soaked for several
days or weeks in a solution of about 40% glycerine in 3% formalin
before being dried and placed in the small boxes. Most of the re-
mainder of the algae may be dried in a standard plant press.

Inasmuch as the algal specimens should ultimately be mounted on
standard 11^2 by 16 Va herbarium paper,i whole sheets or suitably
sized pieces of this paper may be used for the next step which is the
backing of the specimen as it is floated out for drying.

Mounting may best be done in a broad, shallow tray large enough
to accommodate a full size herbarium sheet. The sheet of paper to be
used in each instance should be immersed in water in the bottom of
the tray. The water should be of the least depth suitable for floating
out the particular specimen at hand and spreading it on the paper.
After the plant has been spread out in a natural appearing manner on
its suitably sized sheet in the water tray, the sheet should be lifted
carefully from one side to allow the water to drain off gradually and
to leave the specimen spread out and undisturbed on the sheet. A
device for affecting this drainage may be made from a piece of gal-
vanized sheet metal by bending down the corners to form short legs.
These will permit the middle to be depressed shghtly for spreading a
specimen and released to allow the water to drain off evenly.

1. This and other herbarium supplies, press materials, paste, packets, etc., may
be obtained from herbarium supply houses such as Bonestell & Company, San Francisco,
California; General Biological Supply House, 8200 South Hayne Ave., Chicago 20, III.,
or Ward's Natural Science Establishment, 3000 Ridge Road East, Rochester 9, N. Y.

II

HOW TO KNOW THE SEAWEEDS

The sheet or card bearing the spread specimen may be placed
directly on a dry felt in the press and covered either with a piece
of cloth or a piece of waxed paper. Cloth will serve best for drying

coarse, succulent specimens, while
the waxed paper will prove more
satisfactory for smaller forms and
especially very lubricous or muci-
laginous ones. Very coarse speci-
mens need not be spread on pa-
per at all, but arranged between
cloths in the press. After drying
they may be mounted on the her-
barium sheets by means of straps.
Each specimen sheet should bear
the collection number assigned to
the particular species in the field
note book.

When the spreading has been
completed and the last felt drier
has been placed over a specimen,
the press should be strapped up
with the application of consider-
able pressure. It is necessary to
prevent the specimens from shrink-
ing or curling during the drying
process and to accomplish the dry-
ing in the shortest possible time.
This may best be done by frequent
changing of the driers, — at least
once a day. The specimens should not be subjected to heat, as by plac-
ing the press in an oven, but, rather, dehydrated by frequent replacement
of the wet driers with warm, dry ones. In changing the driers the first
wet one on top should be removed and a dry one placed over the speci-
men, then, by insertion of one hand beneath the next lower wet felt
while the other is placed on top, the whole layer may be Hfted and
turned upside down without disturbing the specimens or the cloth or
waxed paper covering them. If this process is repeated quickly for
each sheet and the pressure promptly reapplied in the press, good
specimens will result in which a large proportion will adhere to the
paper satisfactorily by means of their own mucilage. Drying will usu-
ally take from two days for delicate specimens to a week for coarse
ones. It will usually be more quickly and satisfactorily accomplished
after kilhng the specimens in formaHn than otherwise. Care must be
taken to be sure the drying is complete before removal of specimens
from the press, for otherwise shrinkage of the specimen and conse-
quent wrinkhng and curling of the paper backing will result.

A Finished Herbarum Sheet.

12

HOW TO KNOW THE SEAWEEDS

In the preparation of the marine algae herbarium it will be found
necessary to provide for the storage of several different kinds of
preservations. The fleshy species which lend themselves to pressing
and mounting on herbarium sheets may be handled in the same way
as are terrestrial plants. Those which have adhered well to backing
sheets during the drying process may be mounted by pasting to stan-
dard herbarium sheets. Tin paste or standard herbarium paste should
be used. Rubber cement, plastic cement, staples, etc., are not satis-
factory. Coarser specimens which are dried free of backing may be
fixed to herbarium sheets by means of paste or by strips of gummed
cloth. When the herbarium label, (Fig. 6) properly inscribed, has been
pasted to the lower right hand corner of the sheet the plant is ready
for filing. If portions of the specimen have been retained in Hquid
preservative, this should be indicated somewhere on the sheet for fu-
ture reference.

MARINE ALGAE OF CALIFORNIA

Locality: La Jolla, California

June 1, 1946

Habitat: In deep shade at base of
boulders subjected to heavy
conditions. Temp. 18.8° C. at 5

Collected by E. Yale Dawson
det. by

clifTs
surf.
a.m.

on southwest
Essentially

side of bay,
sublittoral

No.

among
growth

Fig. 6. A Sample Algal Specimen Label.

Liquid preserved specimens usually may be kept in dilute formalin
for months or a few years without difficulty, but for long periods of
time 65 to 70% ethyl alcohol seems to be more satisfactory. A con-
venient procedure is to keep the small bits of preserved material in 4
dram shell vials in the one-gross boxes in which they are sold. They
may be cross-referenced (indexed) on the herbarium sheets by means
of reference to consecutive numbers written on the corks. More per-
manent filing of these is accomplished by placing them within air
tight, glass capped, pint mason jars.

13

HOW TO KNOW THE SEAWEEDS

Bulky specimens, especially calcareous forms and crustose species
adhering to rocks, shells, etc., may best be kept in small boxes fitting
into standardized cardboard trays. The trays may be numbered and
the labeled specimens referred to by means of cross-reference sheets
in the herbarium file.

Specimens which are too small for convenient mounting on her-
barium sheets may be placed in small packets affixed to the sheet,
or, if very small and delicate, mounted whole on sUdes and then
cross-indexed. Inasmuch as the preparation of sUdes for study and
reference is of great importance in algology, it seems well to explain
here an easy method suitable for the majority of cases.

Permanent slides may readily be made of most species and for
most general morphological purposes by using the ordinary crystal
clear variety of Karo corn syrup. Material preserved either in forma-
lin or alcohol may be prepared after washing in water. The specimen
is first stained either with anahn blue or acid fuchsin on a sUde by
adding a little aqueous stain, acidifying and then washing with a drop
or two of distilled water. After the excess water is drawn off with
blotting paper, Karo syrup, diluted to 50-60% with distilled water, is
appHed and the sHde left open to the air in a dust free place over
night. The next day, after the first drop of dilute Karo has dried down
so that excessive plasmolysis (shrinking) of the cells of the specimen
has been avoided, another drop of more concentrated Karo (about
80%) is added and the cover shp appUed to complete the preparation
which is self seaUng. The Karo dries around the edges within a few
days and although the sHde should not be allowed to stand on edge
for a considerably longer period, it may otherwise be handled with
ease. In the case of transections or of species with a dense structure
of small cells, plasmolysis is not appreciable, and these may be
mounted directly in 80% Karo. Very small bubbles usually will form
gradually under the cover sHp as the drying proceeds, but these rarely
affect the usefulness of the preparation. In the writer's experience
such slides have shown no appreciable deterioration after 15 years
of storage.

For making sections of many specimens a freezing microtome will
prove most desirable, but in the absence of such an instrument good
sections can be made by hand with a razor blade after a Httle practice.
This is most easily accomphshed by using dried specimens, for in the
majority of cases such sections will expand in a drop of water to
very nearly their normal size and shape. If they do not, a httle heat
usually helps. Stubborn cases usually respond to the addition of
potassium hydroxide and heat. The most convenient cutting method
is that whereby the specimen fragment is held with a finger on a

14

HOW TO KNOW THE SEAWEEDS

white card under a dissecting microscope of 6 to 10 power and sliced
with the blade against a finger nail for support and guide.

Calcareous algae present special difficulties in sectioning and must
be decalcified and dehydrated with alcohol, embedded in paraffin
and sectioned on a rotary microtome. Sectioning and staining proce-
dures may be found in accounts of botanical microtechnigue, such
as Johonsen's Plant Microtechnique, McGraw Hill & Co., 1940.

15

WHAT TO LOOK FOR

N beginning a study of the seaweeds the student usually
expresses surprise that the members of a single family
or genus appear to be entirely different from each other,
while, on the other hand, members of completely unre-
lated groups may look aUke. This is so because his su-
perficial examination of the plants has not permitted him to see the
features by which the plants may be related or distinguished. It must
be emphasized that for the beginner, who has as yet no acquaint-
anceship with the various forms, microscopic examination of the
vegetative structure and also of the reproductive organs of the plants
is essential to an understanding of them and to his success in the use
of the key which follows.

VEGETATIVE STRUCTURES

Among these macroscopic marine algae with which we are deal-
ing, the seaweeds, the protoplasm is always surrounded by a cell wall
which may assume a multitude of different forms and which may
range from thin to thick, and from rigid to gelatinous. In a great many
of the smaller algae, or even larger forms whose thalU are finely dis-
sected, much of the cellular structure may be observed simply by
making a whole mount of a piece of the thallus on a slide. The larger
and coarser forms, however, have such a dense structure that it is
impossible to make out details of cellular structure unless thin, trans-
parent sections are cut to show the organization of the cells in the
plane desired.

Many of the delicate forms will show under the microscope that
they are made up of a single row of cells constituting a uniseriate fila-
ment. Some such filaments are always unbranched, while others are
branched in various ways. The diagrams in Fig. 7 show several dif-
ferent manners of branching which may be encountered.

Among uniseriate filaments, some will be encountered which have
short cells, about as long as wide, while others will have elongated
cells (See Figs. 96 and 97). Still others will exhibit only occasional
cross walls, often only at the points of branching. These will be coe-
nocytic forms of marine green algae in which the cells are multinu-
cleate. Among these coenocytic green algae are a number of forms in
which cross walls are rare or entirely lacking in the filaments, so that
the entire plant consists of a variously ramified hollow tube. The fam-
ous Valonia ventricosa (See Fig. 13) consists essentially of a single
large, multinucleate cell which may become as large as a hen's egg.

16

HOW TO KNOW THE SEAWEEDS

\

\

^

B

D

\

/

\

\

/

N
\

\

H

Fig. 7. Some examples of different kinds of branching in the marine algae. A.
Unbranched (simple); B. Dichotomous C. Pinnate alternate; D. Pinnate opposite; E. Ver-
ticiHate; F. Multifarious; G. Pectinate, or secund; H. Monopodia!; I. Sympodial.

Other filamentous thalli will be found to be multiseriate, or made
up of several rows, tiers or layers of cells. Sometimes it will be pos-
sible to interpret the structure satisfactorily by focusing through the
more or less transparent external cells to observe the inner ones, but
if there are more than two or three layers of cells involved it usually
will require a cross section or longitudinal section to determine the
cell forms and relationships. Such sections will often result in the
discovery that the filament which appeared to be soHd is actually a
hollow tube, or that the central region contains a distinctive kind of
cell structure which was invisible from the outside.

Coarser thalH will be found to be made up in a variety of differ-
ent ways. Some quite large plants such as Codium fragile may con-
sist entirely of branched, unseptate, coenocytic filaments, while sUp-
pery or gelatinous plants such as ^Nemalion often are similarly com-
posed of branched filaments which are, however, regularly septate.
Others, such as Gracilaiia, show a firm, soUd, compact structure of
cells of increasing size from the outside inward. Many of the larger
thalh, either cyUndrical or flattened, show a differentiation of tissues
whereby a parenchymatous medulla is enclosed by a filamentous cor-
tex, or vice versa. In some of the giant kelps, such as Nereocystis, such
specialized structures as sieve tubes comparable to those of higher
plants occur.

17

HOW TO KNOW THE SEAWEEDS

It is often necessary to examine the apex of thallus branches to de-
termine the manner of growth. The apex, also, is often so relatively
deUcate that it permits observation of cellular structure which is ob-
scured in the denser, older parts of the thallus (See Fig. 18). Growth
may occur in a variety of ways. In some uniseriate filaments, growth
may proceed by intercalary division of cells in any part, or in a
special region of the filament (See Fig. 106). In trichothallic growth
such intercalary divisions occur in multiseriate thalli at the base of one
or more apical hairs (See Fig. 19 and glossary for explanation of these
terms). Apical growth may occur in other ways, namely, by means
of a single apical cell which cuts off new cells from below, or by a
small or large number of cells forming a "fountain type" of apical
meristem (See Fig. 20), each cutting off cells from lower sides. Still
another manner of growth is observed in many complanate thalli in
which the actively dividing, meristematic cells lie along the margin
so that growth proceeds by expansion of the niargins.

Fig. 8. Examples of various kinds of holdfasts. A. A simple, modified, basal cell
(Chaetomorpha); B. Unicellular rhizoids (Lophosiphonia); C. A solid basal disc (Grin-
nellia); D. Creeping stolons with adherent discs (Gelidium); E. A. horny cone (Sargassum).

18

HOW TO KNOW THE SEAWEEDS

It will be worth while for the student to take particular notice of
the apices of branches in the Red Algae, for in that group especially
the characteristics of the apex will provide important clues for identi-
fication. He will find, for example, that the presence of a single apical
cell is usually associated with the presence of a central axial filament
and that the recognition of these and of other such features may be
important in understanding the vegetative structure for the purpose of
interpreting correctly the steps in the key.

It will become evident as experience is gained in making cross
sections for the purpose of reveaUng the features of internal structure
that young portions of a plant are much more satisfactory for section-
ing than very old ones. The additional complications contributed by
secondary growth of certain tissues often obscure the important basic
features of structure. Accordingly, one should exercise some care in
the selection of a suitable fragment for sectioning, or should repeat the
operation on several different parts if difficulties are encountered in
the first interpretation.

The manner of attachment to the substrate differs widely in the
marine algae, from a holdfast consisting of a single modified basal
cell, to various kinds of penetrating or entangling rhizoids, multicel-
lular, adherent discs, creeping stolons, and massive clasping hapteres
(Fig. 8). In many instances the kind of attachment constitutes an im-
portant generic or specific character, and identification may be im-
possible without a knowledge of it. Accordingly, it is important for
the collector to obtain complete plants including the holdfast wherever
possible, even if this may require breaking the rock upon which a
specimen is growing.

REPRODUCTIVE STRUCTURES

NLIKE the several seed-bearing marine flowering plants
which are treated at the end of this book, the algae re-
produce, with few exceptions, by means of microsco-
pic spores. Although these spores themselves are very
small, the reproductive structures which produce them
are often large enough to be visible to the unaided
eye and are useful in providing distinctive characters for classifica-
tion purposes. For this reason the student should acquaint himself with
some of the more general aspects of algal reproduction before endeav-
oring to identify his specimens.

The widespread misconception that the algae are "just simple,
primitive plants" is quickly di-spelled when one studies their marvel-

19

HOW TO KNOW THE SEAWEEDS

ously varied life histories and often exceedingly complex reproductive
mechanisms. So varied are these that space is available here only
for the presentation of a few generalizations and examples under
each of the three major seaweed divisions. For more detailed infor-
mation the student is referred to G. M. Smith's Cryptogamic Botany,
Vol. 1, McGraw Hill & Co., and for a highly comprehensive account
with full bibhography, to F. E. Fritsch's The Structure and Reproduc-
tion of the Algae, Volumes 1-2, Cambridge University Press.

THE GREEN ALGAE

Only about 10% of the Chlorophyta are marine, but among these
a number of different orders are represented along with a consider-
able range in reproductive complexity. Both asexual and sexual repro-
duction occur. In some of the simpler filamentous forms reproduction

sporophyic
plan

^oospores

iion

germination

ga,metophyie
plants

C/ gametes

Fig. 9. Diagram of the Life Cycle of L//va.

20

HOW TO KNOW THE SEAWEEDS

may occur mostly by fragmentation of the filament, but more com-
monly some kind of spore is produced which may germinate to pro-
duce a new plant. Two common kinds are the motile, flagella-bearing
zoospore, and the non-motile aplanospore. These may be produced
simply by a differentiation of the contents of a vegetative cell, or, if
the structure producing the spores is in any way specialized and dif-
ferent from the ordinary vegetative cells, it is called a sporangium.

Sexual reproduction in the Green Algae involves a union of gametes
which may be motile or non-motile. In the great majority of marine
green algae the gametes are flagellated. When fusion occurs between
those which are of equal size the species is called isogamous, while
union of flagellated gametes of unequal size is characteristic of aniso-
gamous species.

A type of life history which may be considered fairly representa-
tive of the many larger marine green algae is exemplified by Ulva, the
sea lettuce. In Ulva, an alternation occurs between an asexual gen-
eration (sporophyte) producing quadri-flagellate zoospores, and a sexual
generation (gametophyte) producing bi-flagellate gametes. The alter-
nation is called isomorphic because the sporophyte plant (diploid gen-
eration) is essentially identical in external appearance with the game-
tophyte plant (haploid generation). The life cycle is diagrammed in
Fig. 9.

UnUke Ulva, some genera of marine green algae bear special struc-
tures (sporangia and gametangia) for the production of their reproduc-
tive cells, but students will find that most genera of green algae can
be recognized so readily from their vegetative form that reproductive
organs usually need not be present for identification to that point.
Specific identifications, on the other hand, may often require careful
study of the reproductive organs and of the Hfe history, sometimes
even to the point of culturing the plants to obtain Uving spores and
gametes for examination.

THE BROWN ALGAE

As a broad generalization it may be said that all the brown algae,
with the exception of the Fucales, have an alternation of sporophyte
and gametophyte generations, but among the greatly diversified forms
of this large marine assemblage a number of variations and compli-
cations in the Hfe histories are superimposed upon this fact. On the
other hand, the beginning student will be relieved to know that the
majority of the large brown, seaweeds have only one general kind
of Hfe cycle with which he needs first to become familiar. In this great
majority of instances the large, macroscopic plant which is collectable
in the field is the sporophyte generation which alternates with a micro-

21

HOW TO KNOW THE SEAWEEDS

scopic gametophyte generation. The microscopic sexual plants are
rarely detectable in nature and have been learned about through
laboratory culture studies. Thus, among the brown algae treated in
this account, with the exception of the orders Ectocarpales and Dictyo-
tales, the plants encountered in the field will be of only one genera-
tion, namely, the sporophyte.

The hfe cycle of Laminaria is presented as an example of this
prevalent heteromorphic type of alternation in which the two genera-
tions are dissimilar. Fig. 10.

sporophyte

A

sort of
unilocular

sporan(j/a.

6 gametophyte

sporophyte
deyelopment

ant hero-
joids

us/on

Fig. 10. Diagram of the Life Cycle of Laminaria.

Although in the order Fucales, which contains many of our com-
monest rock weeds such as Fucus, Pelvetia, Ascophyllum, etc., the
macroscopic plant of the field is the sporophyte generation, the life
cycle differs markedly from that of Laminaria in the elimination of the
gametophyte generation. The life cycle of Fucus is diagrammed in
Fig. 11. Note that the number of functional eggs in the macrosporan-
gium is a key character which is used in step 166 of the key.

Nothing has been said about the orders Ectocarpales and Dictyo-
tales in which the gametophyte plants are present and are usually
essentially like the sporophyte plants. At this point the student need

22

HOW TO KNOW THE SEAWEEDS

only be aware that he will encounter both asexual and sexual plants
of these groups in his collecting and that in most cases either will
serve equally well with regard to the use of this illustrated key.

conceptac/e

sporophyie

receptacle

macro-
sporantjiurri

micro-
sporancjiQ.

^oospores
(ant hero JO ids)

o

fertilisation ^

[aplarfospores]

Fig. 11. Diagram of Ihe Life Cycle of Fucus.

THE RED ALGAE .

The elementary student of phycology has long been perplexed by
the problem of recognition of various kinds of red algae in the field,
for many of them are not really red in color, but green, brown, purple
or even blackish in nature. He is further discouraged when told that
their primary morphological distinction from other algae is found in
the presence of non-motile male gametes which fuse with a special
female sex organ, the carpogonium. It is because of such situations
which often make it practically impossible for a beginning student to
place his specimens in the right algal division that the present arti-
ficial key is designed to key out all groups together without regard to
natural relationships.

Nevertheless, in the use of the key one will find frequent cause to
be acquainted with some of the fundamental aspects of reproduction
in the Red Algae, for in this group especially, the reproductive struc-
tures are often conspicuous and serve conveniently in the recognition
of a number of genera.

23

HOW TO KNOW THE SEAWEEDS

superficia.}

^sporangia, X x.^«

/) OJ) ^germination

teira,spores

carpospores

non-moiile
sperrnatioL

carpo^onia

branch

cijstocarp feriili-taiion

'^^^^^^ development ^^ •'

carposporophyte
in Q ^ametophyte

Fig. 12. Diagram of the life cycle of Gracilaria.

Again as a broad generalization it may be said that a large ma-
jority of the Red Algae have an alternation of not two, but three gen-
erations, namely a sporophyte and a gametophyte generation which
are isomorphic, and a carposporophyte generation which remains at-
tached to and, in a sense, parasitic on the gametophyte generation.
Briefly, a macroscopic sporophyte plant produces non-motile asexual
spores, usually tetraspores, which germinate to produce separate male
and female gametophyte plants. The male plants produce non-motile
sexual cells (spermatia) which are freed and lodge against and fuse
with the female sex organ (carpogonium) on the female plant. As a
result of gametic union which may occur in a variety of ways, a new
generation begins development in or on the female gametophyte. This

24

HOW TO KNOW THE SEAWEEDS

generation consists of a tissue called a gonimoblast which produces
carpospores in a number of ways, often within a special enveloping
structure called the cystocarp (See Figs. 38-39). The Hberation of the
carpospores and their germination begins the development of the sporo-
phyte generation again . whereby the cycle is repeated.

The genus Gracilaria may be used as an example of this kind of
life cycle (Fig. 12) which is characteristic of most of the red algae ex-
cept those of the orders Bangiales and Nemalionales,

25

USE OF THE PICTURED-KEY

HE success with which the following key may be used
will depend firstly, upon the adequacy of the speci-
mens for identification, secondly, upon the care with
which they are examined, and thirdly, upon the ac-
curacy with which terms in the key are interpreted. A
microscope is a prerequisite in this study, for many of the marine algae
can be identified only by observing certain features of reproduction or
of internal anatomy. However, in the present key an attempt has been
made to simplify the identification process so that, for the most part,
only relatively gross microscopical examinations are required. In-
deed, the student will find that a number of the larger algae, espe-
cially those bearing vesicles, veins or ribs, may be identified en-
tirely on macroscopic characters.

It cannot be overemphasized that the specimen must be adequate
before identification is attempted, for a juvenile, sterile, or fragmentary
algal specimen will often present the same difficulties with respect
to the use of a key as does a flowering plant for which only a leaf
or a piece of root has been collected. As more and more field ex-
perience is gained by the student, the problems of recognizing and
selecting suitable specimens will diminish.

The key treats of marine algae such as may be encountered on
any coast of the continental United States, and it will be noted that
in a good many instances a genus will occur on both Atlantic and
Pacific coasts. However, a rather large proportion of the algae ore
relatively localized, and for this reason an indication of the geographic
distribution is given in each case.

Of necessity, for lack of space, only the larger and commoner
marine algae are treated here, and in the majority of cases only as
to genus, although the full specific name is provided for most of the
habit illustrations. Thus, the student must be aware that some of the
genera of plants he collects in any given area may not be illustrated
in this brief account.

It should be pointed out here that the sequence in which the genera
appear in the key is entirely artificial and bears no necessary con-
nection with phylogenetic relationships. However, in order that the
student may orient himself as to the relationships of the various plants,
each is numbered in the index according to an appended list in which
they appear in the phylogenetic sequence ordinarily encountered in
the more modern taxonomic treatises.

26

ADDITIONAL REFERENCES

S the examination and identification of specimens pro-
gresses the student will find it desirable to supple-
ment the information found herein by using local flor-
istic accounts of the algae of his particular region.
There are several of these which are well illustrated
and will be useful, although by no means all of the
coastal areas of the United States are covered in detail. Unfortunately,
none of them contain a single comprehensive key to the genera which
they treat, and so will be most helpful in the making of specific identi-
fications after the genus has been determined by means of tho present
book. It is also in these special floristic accounts or in the literature to
which they provide references that the smaller, rarer, localized and
(or) less conspicuous plants may be sought.

Dawson, E. Y. 1945. An annotated list of the marine algae and marine
grasses of San Diego County, California Occas. Papers San Diego
Soc. Nat. Hist. (7): 1-87.

1961. A guide to the literature and distributions of Pacific

benthic algae from Alaska to the Galapagos Islands. Pacific Sci-
ence 15(3): 370-461.

Doty, M. S. 1947. The marine algae of Oregon, I-II. Farlowia 3: 1-65,
159-215, 14 pis.

Hoyt, W. D. 1920. Marine algae of Beaufort, N. C, and adjacent re-
gions. Bull. Bureau of Fisheries 36: 368-556, pis. 84-119.

Kylin, H. 1925. The marine red algae in the vicinity of the biological
station at Friday Harbor, Wash. Lunds Univ. Arsskr., N.F., 21(9):
1-87. 47 figs.

Setchell, W. A. and N. L. Gardner 1920. The marine algae of the
Pacific Coast of North America. Part 2, Chlorophyceae. Univ.
Calif. Pub. Bot. 8: 139-381. 25 pis.

1925. The marine algae of the Pacific Coast of North Ameri-
ca. Part 3, Melanophyceae. Ibid. 8: 383-898. 20 pis.

Smith, G. M. 1944. Marine algae of the Monterey Peninsula, California,
ix + 622 pp., 98 pis. Stanford Univ. Press.

Taylor, W. R. 1960. Marine algae of the eastern tropical and sub-
tropical coasts of the Americas, xii + 870 pp. Univ. Michigan
Press.

1937. Marine algae of the northeastern coast of North

America, i-vii + 427 pp., 60 pis. Univ. Michigan Press, Ann Arbor.

27

PICTURED-KEY TO THE COMMON GENERA OF
MACROSCOPIC MARINE ALGAE OF THE

UNITED STATES

la Thallus consisting of a single large, subspherical cell with basal
attachment. Fig. 13 124

Fig. 13. Valonia ventricosa J. Agardh

An entire plant showing the single large
spherical cell with basal rhizoids for attach-
ment, X 1.5.

Figure 1 3

lb Thallus consisting of more than one cell, or if coenocytic, at least
not subspherical in form 2

2a Thallus more or less calcareous, the calcium carbonate deposited
superficially in the outer tissues, in articulated segments, or through-
out the entire thallus 106

(If in doubt about the calcareous nature apply a little dilute acid
to a clean piece of thallus and watch for bubbles under a dissect-
ing microscope.)

2b Thallus not calcareous 3

28

HOW TO KNOW THE SEAWEEDS

3a Entire thallus hollow, subglobular to tubular, or the thallus with hol-
low, septate or unseptate branches, or provided with hollow blad-
ders, bulbs or vesicles. Fig. 14 82

Fig. 14. Several examples of hollow struc-
tures in the algae.

A. A hollow tubular thallus as in Enteio-
morpha. B. A hollow branch provided with
septation or diaphragms as in Gastrocloni-
um. C. A solitary, hollow vesicle as in
Botryocladia. D. A hollow vesicle (pneu-
matocyst) at the base of a vegetative blade
as in MacTOcystis.

Figure 14

3b Thallus without hollow structures or parts (except sometimes the
coarse stipe, as in Postelsia) 4

4a Thallus crustose, forming a thin, adherent expanse on the substrate,
or, prostrate and coarsely net-like 78

4b Thallus not crustose or net-like, free except for one or more basal
attachmentsi 5

5a Thallus consisting of one or more branched
or unbranched uniseriate filaments Fig. 15,
or consisting of a variously branched, free,
essentially cylindrical filament without cellu-
lar septations (coenocytic) (See Figs. 89-92)
58

Fig. 15. Two forms of uniseriate filaments. A.
An unbranched uniseriate filament as in
Chaetomorpha. B. A branched uniseriate
filament as in Callithamnion.

Figure 15

29

HOW TO KNOW THE SEAWEEDS

5b Thallus of various form and structure, but consisting neither of
one or more branched or imbranched uniseriate filaments, nor of
a branched, free, essentially cylindrical filament without cellular
septations. (Note that some young stages, such as in Bangia. may
be uniseriate; some Caulerpa species are coenocytic but not cylin-
drical; Codium is coenocytic but consists of interwined filaments
whose only free parts are the external utricles) 6

6a Thallus membranous, only 1-2 cells thick, at least at the margins.
Fig. 16 52

ooooooooo

ODOOOOOOO

Fig. 16. A cross section of a distromatic
thallus (2 cells thick) as occurs in Ulva.

Figure 16

6b Thallus cylindrical or flattened; if membranous, with more than
two layers of cells at the margins 7

7a Vegetative portions of thallus dominontly compressed, flattened, or
complanate. Fig. 17 125

C

D

B

Fig. 17, Cross sectional forms of (A.)
compressed, (B.) flattened, and (C.)
complanate thalli.

Figure 17

7b Vegetative portions of thallus dominantly of cylindrical form, or, if
compressed, only slightly so or only in restricted areas such as the
points of branching 8

30

HOW TO KNOW THE SEAWEEDS

8a Growing apices showing a single apical cell, although this some-
times sunken in an apical pit {Chondria, Laurencia) or obscured
by terminal branchlets (especially Dasya. Digenia, Wrangelia) Fig.
18 26

Fig. 18. Examples of apical cells.

A. As found on an acute apex. B. As
found on a blunt apex such as Gelidium
(seen in longitudinal section). C. Sunken
in an apical pit as in Laurencia. D. Some-
what obscured by terminal branchlets (or
trichoblasts or hairs) as in Polysiphonia.

In making observations of apical cells
one will usually have the best results
with young, actively growing vegetative
branch-tips rather than old or fertile ones.
In those plants in which the apex is ob-
scured by enveloping branchlets it may
be necessary to dissect away the very
tip of a yoimg branch and to crush it
under the cover slip on a sHde in order to force the surrounding branch-
lets away and to make the apical cell area visible.

Figure 18

8b. Growing apices without a single apical cell from which growth
takes place 9

9a Growth trichothallic. Fig. 19 24

Fig. 19. An example of trichothalUc growth
by means of a terminal hair with cell di-
vision at its base, as seen in the apex of
Haplogloia andersonii, X 300. Note that
the trichothalUc type of growth will be dif-
ficult to interpret in Heterochordana abieti-
na (See Fig. 42). Its distinctive habit should
be recognized.

Figure 19

31

HOW TO KNOW THE SEAWEEDS

9b Growth apical (terminal) or intercalary, but not trichothallic. Fig.
20 10

8

<>Q,

oo'QovsUOnnfl

^w^fWi II ^'

°1

Fig. 20. An example of terminal growth
by means of an apical meristem in
which there is no evidence of a single
apical cell, as seen in a longitudinal
section of the apex of Gracilaiia. This
is sometimes called the "fountain
type" of apical meristem.

Figure 20

10a Thollus a simple, unbranched filament 250 /x in diameter or less,
with intercalary growth, at first uniseriate Fig. 21, later becoming
multiseriate Bangia

mmmmom^^

mm

ouooyoM

B

Figure 21

Fig. 21. Bangia fuscopurpurea (Dillwyn) Lyngbye

A. A small portion of a young filament showing the uniseriate
character and flattened shape of the cells, X 190. B. An older part of
a filament showing the multiseriate condition, X 190. Growth is by in-
tercalary cell division. This dehcate but often abundant and conspicu-
ous plant occurs both on the Atlantic and Pacific coasts as a sHppery,
hairy covering on rocks and woodwork, the filaments sometimes reach-
ing 20 cm. in length. Several other minute epiphytic species of this
genus may be encountered.

10b Thallus more than 500 a in diameter, branched or unbranched. .11

32

HOW TO KNOW THE SEAWEEDS

11a Thallus usually of firm consistency, of more or less parenchymatous
type structure, at least in the cortical and outer medullary regions.
Fig. 22 18

iTSt^

Fig. 22. Part of a transverse section
of Giacilaria to show the paren-
chymatous type, large, relatively
thin-walled, more or less isodia-
metrical cells of the medulla. In
this instance there is a gradual
transition from the largest medul-
lary cells to the small cells of the
cortex.

Figure 22

lib Thallus not of parenchymatous type structure, soft or firm 12

12a Thallus wiry, rigid, cartilaginous, the medulla of densely packed
longitudinal filaments, the cortex of dense anticlinal cell rows.
Fig. 23 Ahnieltia

Fi'g. 23. Ahnieltia plicata (Hudson) Fries

A small portion of a plant to show the
cylindrical, regularly dichotomous branch-
es, X 1.5. This species occurs both in New
England and along the Pacific Coast. A.
concinna J. Agardh is a coarser species
of greater diameter which is found occa-
sionally along the Pacific Coast.

Figure 23

12b Thallus soft, spongy, or often gelatinous, (firm in Chordaria). con-
sisting of variously branched, interlaced or intertwined filaments
which may be more or less compacted in the medulla but are
externally free ^'^

33

HOW TO KNOW THE SEAWEEDS

13a Thollus fQaments without cross walls, ending at the surface in a

continuous layer of inflated utricles. Fig. 24 Codium

Fig. 24. Codium iiagile (Suringar) Harlot

A small group of utricles showing their
origin from the non-septate, branched fila-
ments making up the thallus. X 50. In
this species the utricles are pointed, but
in other species they are smooth. Several
kinds of Codium occur along the Pacific
Coast and along the Atlantic Coast from
North Carohna southward. The common-
est Atlantic species, C. dichofomum (Hud-
son) S. F. Gray and the common Pacific
one, C. fragile, are both erect, dichotom-
ously branched, cylindrical plants. Other
species are flattened at the points of
branching while still others are prostrate
and somewhat cushion-shaped or with
lobe-like branches.

Figure 24

13b Thallus filaments with cross walls; surface without inflated utricles
14

14a Brownish in color; axis with a solid medulla of compacted,
branched, longitudinal filaments 15

14b Reddish in color; medullary region not solid, the thallus filaments
nowhere compacted 1°

15a Thallus gelatinous; branching irregular; ultimate branches often
short. Fig. 25 Eudesme virescens

Fig. 25. Eudesme virescens (Carmichael)
J. Agardh

A small upper portion of a plant to show
the irregular short branches and the com-
pacted medulla which shows through the
looser, more gelatinous cortical region as
a denser core, X 1.5. This species is found
widely along the Atlantic Coast. It is the
only member of the genus in our flora. A
slender form commonly grows on the
leaves of Zostera.

Figure 25

34

HOW TO KNOW THE SEAWEEDS

15b Thallus firm; branching regular; ultimate branches long. Fig. 26
Chordaria

Fig. 26. Chordaria flagelliformis (Miiller) C.
Agardh

A small upper portion of a plant about 40
cm. long showing the smooth, slender, long
branches, X 0.6. Found on the New England
coast. C. dissessa Setchell & Gardner, a spe-
cies of somewhat irregular diameter and flat-
tening at the points of branching, occurs in
the Puget Sound area of Washington.

Ftgure 26

16a Thallus simple, or furcately branched. Fig. 27.
Nemalion

Fig. 27. Nemalion helminthoides (Velley) Batters

An entire plant, X 0.6. Frequent on rocks at
rather high int^rtidal levels along the Pacific
Coast. A similar but more abundantly branched
species occurs on exposed rocks along the New
England coast and is known as iV. multifidum
(Weber & Mohr) J. Agardh.

Figure 27

35

HOW TO KNOW THE SEAWEEDS
16b Thallus multiiariously branched 17

17a Thallus of several long axes bearing numerous short, mostly sim-
ple lateral branchlets. Fig. 28 Cumagloia andersonu

Fig. 28. Cumagloia andeisonii (Fallow) Setchell
& Gardner

An entire plant, X 0.6. On rocks at high in-
tertidal levels along the Pacific Coast.

Figure 28

17b Thallus irregularly and indeterminate-
ly branched in 1-3 orders. Fig. 29.
Helminthocladia californica

Fig. 29. Helminthocladia californica (J.
Agardh) Kylin

The upper part of a plant X 0.6. Occa-
sional in upper intertidal pools along south-
ern California.

Figure 29

18a Thallus solid and smooth, the cortex without a conspicuous super-
ficial layer of hairs and paraphyses 20

36

HOW TO KNOW THE SEAWEEDS

18b Cortex bearing conspicuous superficial hairs, filaments, or para-
physes. Fig. 30 19

Fig. 30. Chorda filum (Linnaeus) Lam-
ouroux

Part of a transaction of a thallus
to show the parenchymatous struc-
ture and the presence of conspicu-
ous superficial hairs. For habit and
other comments see Figure 32.

Figure 30

19a Thallus subdichotomously branched; cortex bearing arcuate fila-
ments in clumps. Fig. 31 Stilophora rhizoides

Fig. 31. Stilophora rhizoides (Ehrhart) J.
Agardh

The upper part of a plant to show the
rough surface due to clumps of hairs, and
the loose, remote branches, X 1.2. This
is the only species of the genus on our
coasts. It occurs in quiet bays from North
Carolina northward to New England.

Figure 31

37

HOW TO KNOW THE SEAWEEDS

19b Thallus whip-like, essentially unbranched; cortical hairs and para-
physes not in clumps. Fig. 30, 32 Chorda (in part)

Fig. 32. Chorda filum (Linnaeus) Lamouroux

An entire plant, X 0.3, showing the un-
branched, whip-like form. Young, growing plants
will show, when held in water, an outer cover-
ing of delicate, colorless hairs which fall away
with age. The terminal parts of old plants ore
usually partly decayed. This species which is
widespread on both sides of the north Atlantic
occurs commonly near low tide level and be-
low from New Jersey northward, usually at-
tached in groups on stones or shells. Another
species, C. tomentosum Lyngbye, is more dense-
ly covered with hairs and occurs north of Cape
Cod. Some adult forms of Chorda are more
or less hollow and will key out best under step
91b.

Figure 32

38

HOW TO KNOW THE SEAWEEDS

20a Medulla containing slender, more or less longitudinal filaments
aggregated in the center of a parenchymatous tissue. Fig. 33. . .21

iM^(

Fig. 33. Agardhiella coulteri (Har-
vey) Setchell

The inner medullary part of the
thallus as seen in cross section
showing the large, thin-walled,
parenchymatous cells surrounding
the central core of slender, elon-
gated, relatively thick-walled fila-
mentous cells.

Figure 33

20b Medulla entirely of more or less isodiametrical cells. (See Fig. 22)
22

21a Branches relatively slender, narrow at the base and gradually
tapering to the apex. Figs. 33, 34 Agardhiella

Fig. 34. Agardhiella tenera
(J. Agardh) Schmitz

A small mid-portion of a
plant, X 1.4. This species is
abundant below low water
level along the Atlantic
Coast south of Cape Cod
and along the Gulf of Mexi-
co. Another species of more
robust habit, A. coulteri (Har-
vey) Setchell, occurs along
the entire Pacific Coast.

Figure 34

39

HOW TO KNOW THE SEAWEEDS

21b Branches thick, not narrowed at the base, not attenuated. Fig.
35 Eucheuma (in part)

Fig. 35. Eucheuma isiforme (C. Agardh)
J. Agardh

Part of a plant such as may reach 30-
50 cm. in height, showing coarse, succu-
lent branches and warty surface, X 0.7.
This and other subcylindrical species may
be found in Florida and westward along
the Gulf coast. Other species are flattened
but are of infrequent occurence.

Figure 35

22a Branching dichotomous, at least in part, and mainly in one plane.
Fig. 36 Gymnogongrus gTiiiithsiae

Fig. 36. Gymnogongrus grifiithsiae (Tur-
ner) Martius

A small upper part of a plant to show
the dichotomous branching of the cyUn-
drical or somewhat compressed thallua,
X 2. Although several flat species of Gym
nogongrus occur in our flora and will be
accounted for farther along in the key
this is the only cyhndrical one on our
coasts. The densely bushy little plants
reach about 5 cm. in height and grow
just below low water mark along the en-
Figure 36 tire Atlantic Coast south of Massachusetts.

40

HOW TO KNOW THE SEAWEEDS

22b Branching not dichotomous, but multiiarious. Fig. 37

23

Figure 37

Fig. 37. Branching habit of Gracilariopsis

A. Part of a sterile plant of a Gracilariopsis species to show the
irregular, multifarious branching of the slender, cylindrical thallus,
X 1. B. Part of a fertile, cystocarpic plant of Gracilariopsis sjoestedtii
(Kylin) Dawson showing the cylindrical form, the protruding, subhemi-
spherical cystocarps, and the irregular, multifarious branching. See
also comments at Fig. 39.

41

HOW TO KNOW THE SEAWEEDS

23a Gonimoblast placenta of relatively large, vacuolate cells and with

nutritive filaments extending into the pericarp. Fig. 38

GracilaTia verrucosa

Figure 38

Fig. 38. Gracilaria sp.

A vertical section through a cystocarp showing the large-celled
central gonimoblast placenta from which nutritive filaments extend
out into the wall of the cystocarp (pericarp). The opening at the top
of the cystocarp is the ostiole. Carpospores are seen being produced
from the outer cells of the gonimoblast. Most of the species of Graci-
laria are more or less flattened (See Fig. 233) but one common cylindrical
one is G. verrucosa (Greville) Papenfuss which may be found both along
the Atlantic and Pacific coasts. It has been exploited commercially
as a source of agar although the product obtained is of a lower
quality than that obtained from species of Gelidium.

42

HOW TO KNOW THE SEAWEEDS

23b Gonimoblast placenta of small cells, without nutritive filaments
extending into the pericarp. Fig. 39 GracilaTiopsis

Figure 39

Fig. 39. Gracilariopsis sjoestedtii (Kylin) Dawson

A vertical section through a mature cystocarp showing the small-
celled, dense gonimoblast placenta and the absence of nutritive fila-
ments connecting with the pericarp. This species occurs along the
Pacific Coast from central Oregon southward and has been identi-
fied from North Carolina and Florida by the writer. It should be
pointed out that this plant and Gracilana venucosa are indistinguish-
able except with regard to the cystocarps and antheridia which in
the former are superficial and in the latter are produced in deep
pocket-hke cavities. One other species of Gracilariopsis occurs com-
monly along the southern California coast, G. andersonii (Grunow)
Dawson. It is relatively short and tufted.

43

HOW TO KNOW THE SEAWEEDS
24a Branching pinnate and opposite. Fig. 40 Desmarestia (in part)

Fig. 40. Desmarestia viridis (Miiller) Lam-
ouroux

A small portion of a plant to show the
opposite branching of the slender, cylin-
drical axes. Most of the species of Des-
marestia are flattened or complanate, but
this one which occurs to the north of New
Jersey, and is also reported from Cali^
fornia, is cylindrical. Two other cyhndrical
species (D. media (Agardh) Greville and
D. farcta Setchell & Gardner) occur in the
Puget Sound area of Washington, usually
in infratidal habitats.

Figure 40

24b Branching not pinnate 25

25a Branches all of irregular lengths, without the formation of very

distinct percurrent axes in the plant as a whole. Fig. 41

Haplogloia andersonii

Fig. 41. Haplogloia andersonii (Farlow) Lev-
ring

A small portion of the upper part of a
plant, X 1.5, to show the irregular multifari-
ous branching and the dense covering of fine
hairs over the whole surface of the thallus.
The structure of the growing apex of this
plant is shown in Fig. 19. Occasional at low
tide levels along the entire Pacific Coast. In
the middle parts of its range it is known to
begin its development late in the winter and
to mature and disappear again by the be-
ginning of summer.

Figure 4)

44

HOW TO KNOW THE SEAWEEDS

25b Thallus with more or less uniform, short, multifarious branchlets
borne on percurrent axes. Fig. 42 Heterochordaria abietina

Fig. 42. Heterochordaria abietina
(Ruprecht) Setchell & Gardner

Part of a group of erect axes, X 1.
A common species at middle tide
levels from central California north-
ward to Alaska. Plants reach 20-25
cm. in height. The axes and branch
es, which at first are solid, may later
become hollow but usually will not
give the impression of being hollow
unless sectioned.

Figure 42

45

HOW TO KNOW THE SEAWEEDS

26a Thallus more or less corticated, but ultimate branchlets either
strictly uniseriate or corticated only by bands. Fig. 43 27

kC3/

o

Figure 43

Fig. 43. Examples of small portions of three different Ceramium spe-
cies, (A. X 250; B-C. X 100) to show various kinds of cortical
bands encircling the relatively very large cells of the uniseriate
axes.

26b Ultimate branchlets neither uniseriate nor incompletely corticated
by cortical bands, but completely corticated and (or) with many
rows or layers of cells 32

27a Ultimate branchlets uniseriate but with cortical bands

28

27b Ultimate branchlets strictly uniseriate, without cortical bands ... 29

46

OOOOOOOC!)

HOW TO KNOW THE SEAWEEDS

28a Axes completely corticated, unlike the ultimate branchlets which

are uniseriate except for cortical bands. Fig. 44 Spyridia

Fig. 44. Spyridia tilamentosa
(Wulfen) Harvey
A small part of a completely
corticated axis and part of two
banded ultimate branchlets, X
80. This dehcately bushy httle
plant occurs widely along the
Atlantic coast and in southern-
most California. It is essential-
ly a tropical species which in-
habits protected, warm bays
and pools in the northern parts
of its range. Another species,
bearing spines on the upper
nodes, occurs in Florida (S. acu-
leata (Schimper) Kiitzing).

28b Axes and branches all similar, banded. Fig. 45

CeTamium (in part)

'Ooooooo

(poooo

ill.

Figure 44

Figure 45

Fig. 45. Ceramium avalonae Dawson

A small part of a plant to show the cortical bands, the caliper-like
tips characteristic of several species, and one manner of production of
tetrasporangia. The very fine lateral hairs are also present on a num-
ber of species. C. avalonae occurs in southern California.

The genus Ceramium is a large one containing many incomplete-
ly corticated as well as completely corticated species (See Figs. 43, 61).
The incompletely corticated ones are usually quite small species of
warm waters, while the heavily corticated ones are usually larger and
of more temperate distribution. Specific identifications in the genus
must be made through the use of the more comprehensive floristic
works. The writer has presented an illustrated analysis of the twenty-
nine species occurring on the Pacific Coast of North America in Far-
lowia, vol. 4, pp. 113-138.

47

HOW TO KNOW THE SEAWEEDS

29a Thallus showing a gradation from a multiseriate (polysiphonous)
condition to a uniseriate condition in the ultimate ranks of branches.
Figs. 46, 47 Heterosiphonia

Figure 46

Fig. 46. Heterosiphonia erecta Gardner, emend. Setchell & Gardner

A small upper part of a plant to show the uniseriate ultimate
branchlets arising from multiseriate branches of the prior order. Note
the pecuhar antheridial branchlets on this plant with their minute sper-
matic. This is a common small species along southern Cahfornia. The
only large, conspicuous member of this genus in the United States is
H. gihbesii (Fig. 47).

Fig. 47. Heterosiphonia gibbesii (Harvey)
Falkenberg

A small upper portion of a plant, X 1.25.
This is the largest species of the genus in
our flora, occurring in Florida and reach-
ing 10-20 cm. in height.

48

HOW TO KNOW THE SEAWEEDS

29b Thallus without such a gradation from a multiseriate to a uniser-
iate condition in the ultimate ranks of branches. Fig. 48 30

^

Figure 48

Fig. 48. Dasya sp.

A single lateral
branch as separated
from the corticated
main axis showing sev-
eral ranks of uniseri-
ate branchlets, and
several conical anthe-
ridial branchlets. These
uniseriate branchlets
are here much magni-
fied, and to the naked
eye appear as very-
fine hairs both in Da-
sya and in ^lanqelia.

30a Main axes corticated (at least to some extent in lower parts) by
means of the growth of filaments from cells at the nodes. Fig. 49;
branchlets arising only at points of junction of axial cells 31

Fig. 49. CaWiXhammon sp.

A small piece of a plant showing
branching from two nodes and an early
stage in development of cortication by
growth of descending filaments from
the nodal cells. X 85.

Figure 49

49

HOW TO KNOW THE SEAWEEDS

30b Main axes corticated just back of apices, not by filaments from
the nodes; uniseriate branchlets arising from all parts of the cor-
tical surface. Fig. 50 Dasya

Fig. 50. Dasya pedicellata (C.
Agardh) C. Agardh

A mid-portion of a plant
about 15 cm. high showing the
slender lateral branchlets aris-
ing from all parts of the surface
of the corticated axis. X 1.2.
The dark bodies represent cysto-
carps. Although a single Pa-
cific Coast species, Dasya paci-
hca Gardner, occurs abundant-
ly at La Jolla, Cahfornia dur-
ing the summer, this genus is
otherwise restricted in the Unit-
ed States to the Atlantic Coast.
D. pedicellata is the common
species there, occurring all the
way from Texas through Flori-
da to Massachusetts. It is usu-
ally found in protected waters
at depths of 3 to 12 feet below
low water level. There are sev-
eral other species known from
Florida, but they are of infre-
quent or rare occurrence.

Figure 50

50

HOW TO KNOW THE SEAWEEDS

31a Major branching mostly 2-ranked; ultimate branchlets more or
less verticUlate. Fig. 51 Wrangelia

Fig. 51. Wrangelia penicillata
C. Agardh

A small upper part of a plant
to show the branching in two
ranks and the tufted and some-
what verticillate manner of pro-
duction of the ultimate branch-
lets, X 5. This is the largest
of three species found in Flori-
da. It may reach a size of
10-20 centimeters.

Figure 51

31b Major branching distichous or multifarious; no order of branching
verticillate. Fig. 52 Callithamnion (in part); also Seirospora

Callithamnion is a rather large genus of quite delicate, often small
plants which may be either epiphytic or saxicolous and which may be
found along almost any part of our coasts. Some of them are com-
pletely without cortication and will be treated elsewhere in this key
(step 76b). Several other species are corticated only in lower parts,
while C. pikeanum is corticated almost to the apex. In all of them the
alternate arrangement of the uniseriate branchlets of the last orders
and the tetrahedrally divided sporangia are characteristic (See Fig.
108).

There is one plant of another genus which has these characters
and which will key out here. This is the Atlantic coastal Seirospora
griitithsiana Harvey (Fig. 53) which, however, is readily recognized by
its seirospores which are produced abundantly during the summer
in addition to the usual tetraspores.

51

HOW TO KNOW THE SEAWEEDS

Figure 52

Fig. 52. Callithamnion pikeanum Harvey

A portion of an axis with a single primary lateral branch. X 1.
This is the coarsest of our Callithamnion species and the only one
with such heavy cortication. It occurs commonly on rocks at middle
intertidal levels along the whole Pacific Coast except southernmost
California.

Figure 53

Fig. 53. Seirospora giiffithsiana Harvey

A small upper portion of a plant bearing seirospores. X 150.
Epiphytic on Zosteia and various algae from New Jersey to Cape Cod.

52

HOW TO KNOW THE SEAWEEDS

32a Thalli with typical, externally visible pericentral cells. Fig. 54 . . .
49

B

Figure 54

Fig. 54. Appearances of pericentral cells in two different plants.

A. The apex of a Polysiphonia species showing short pericentral
cells, scar-cells, trichoblasts and apical cells. X 100. B. A short piece
of a Lophosiphonia species with a large number of long pericentral
cells surrounding developing tetrasporangia, X 150. Lophosiphonia
is a small, inconspicuous plant not treated in the key.

32b Thalli without typical pericentral cells, or if present, these ob-
scured by cortication 33

53

HOW TO KNOW THE SEAWEEDS

33a Cylindrical axes more or less densely clothed with slender, bristle-
like lateral branchlets. Fig. 55 Digenia simplex

I

mm

Figure 55

Fig. 55. Digenia simplex (Wulfen) C. Agardh

A. An upper part of a plant of rather lax habit, X 0.8. B. A small
part of a single lateral, determinate branchlet to show the cortication,
X 80. Although it is difficult to observe the apical cell of main axes
because of the abundant lateral branchlets, the apical cells of the
determinate laterals are often readily observed. This is a common
tropical plant of Florida and the Gulf of Mexico to Texas. Under favor-
able conditions when the water is well protected the plants may be-
come luxuriantly developed and much-branched, up to 8 to 10 inches
high, while in rough, surfy locahties the plants are usually stubby,
dwarfish and httle-branched. They are commonly of unsightly appear-
ance because of multitudes of epiphytes which cover them.

33b Axes not clothed with slender, hair-like lateral branchlets (but
note also Odonthalia iloccosa. step 179) 34

54

HOW TO KNOW THE SEAWEEDS

34a Growing point sunken in an apical pit. Fig. 56, and surrounded
(at least when actively growing) by long or short hairs. (See Fig.
18c) 37

B

Figure 56

Fig. 56. Laurencia sp.

A cystocarpic branchlet (A.), and a tetrasporic branchlet (B.) to
show apical pit of mature branchlets after the hairs, which originally
surround the apical cell, have fallen away, X 23.

34b Growing point not sunken in an apical pit

35

55

HOW TO KNOW THE SEAWEEDS

35a Thallus showing a single axial filament of very large cells cov-
ered by a thin cortex of much smaller cells. Fig. 57 36

Fig. 57. Ceramium sp.

A longitudinal section through a node to
show two of the large central axial cells and
the thin cortex of small cells covering them,
X 65. This structural feature usually may be
discerned by obtaining a median optical focus
with the microscope using strong light.

Figure 57

35b Axial filament not as above; if present, borne within a medullary
tissue. Fig. 58 38

Fig. 58. Endocladia muiicata (Postels & Ruprecht)
J. Agardh

A cross section of a branch to show the con-
spicuous large axial filament and the radiating
medullary filaments, X 50.

Figure 58

38a Cortical cells in regular vertical rows; axes bearing whorls of 2-
celled spines at regular intervals. Fig. 59. .Centroceras clavulatuzn

Fig. 59. Centroceras clavulatum (C. Agardh) Montagne

A small part of a branch to show the regular ar-
rangement of the cortical cells and the whorls of
spines X 120. A common small plant of Florida,
the Gulf of Mexico and southern California, often
mixed with other small algae in tufts.

Figure 59

56

HOW TO KNOW THE SEAWEEDS

36b Cortical cells not in regular rows; axes without whorls of 2-celled
spines. Figs. 60, 61 Ceramiuni (in part)

Fig. 60. Ceramium pacificum (Collins) Ky-
lin

A very small part of a branch to show
the irregular arrangement of the cortical
cells over the large, subspherical cells of
the axial filament, X 190. A widely dis-
tributed species from southern California
to Vancouver Island.

VPo}

KV>

\€M

m

iS^t^^

p

Im

(0

BBm»,

oc^^'^ocyCP-

Figure 60

Figure 61

Fig. 61. Ceramium rubrum (Hudson) C.
Agardh

A small upper part of a plant, X 6.
This is the largest and commonest of the
completely corticated Ceramium species
of the Atlantic Coast, occurring from Flori-
da to Newfoundland. On the Pacific
Coast C. pacificum (Collins) Kylin and C.
eatonianum (Farlow) De Toni are similar,
while C. codicola J. Agardh is a common
epiphyte on Codium. For other, incom-
pletely corticated Ceramium species see
step 28b and Figs. 43, 45.

37a Branchlets contracted at the base, 500

fx or less in diameter. Fig. 62

Chondria (in part)

Fig. 62. Chondria sedifolia Harvey

A small upper part of a tetrasporic
plant, X 4. This is the only one of our
common Chondria species with depressed
apices. Plants reach 10-15 cm. in height
and occur along the whole Atlantic Coast
to as far north as Massachusetts.

Figure 62

57

HOW TO KNOW THE SEAWEEDS

37b Branchlets mostly not contracted at the base, 750 ix or more in
diameter. Figs. 63, 64 Laurencia (in part)

Figure 63

Fig. 63. Laurencia spp. (tetrasporangial branch apices)

Two examples of upper branches of tetrasporangial plants to
show the slight contraction at the base of branches compared to the
prominent contraction in Chondria. A. X 5; B. X 9.

Fig. 64. Laurencia spp. (habit)

A. Laurencia papillosa (Forskal) Greville. Habit of a portion of a
clumping plant, X 1.5. B. Laurencia ohtusa (Hudson) Lamouroux. Habit
of a portion of a clumping plant, X 1.5. Both of these species are com-
mon along the coasts of Florida and the Gulf of Mexico. Several other
cyhndrical species occur more or less commonly in Florida and also

58

HOW TO KNOW THE SEAWEEDS

along the California coast where L. pacifica KyUn is the most wide-
spread and abundant one. Flattened species of Lauiencia key out un-
der step 181a (See Fig. 226).

Figure 64

38a Thallus gelatinous and slippery; cortex of short, free filaments with
large terminal cells. Fig. 65 Sphaerotrichia divaricata

Fig. 65. Sphaerotrichia di-
varicata (C. Agardh)
KyUn

A. The apex of a plant
highly magnified to show
the enlarged apical cell,
X 560. B. A small portion
of a transection of a thal-
lus to show the free corti-
cal filaments with their
large terminal cells, X
200. The structural fea-
tures .of this plant and
other such gelatinous
forms are usually best ob-
served by crushing out terminal portions of branches on a sHde. Com-
monly epiphytic on larger algae during the summer from New Jersey
northward. Some forms tend to be hollow.

B

Figure ^5

59

HOW TO KNOW THE SEAWEEDS

38b Thallus not particularly gelatinous or slippery; cortex not as
above 39

39a Medulla of filaments radiating from the large, central axial fila-
ment. Figs. 58, 66 Endocladia muTicata

Fig. 66. Endocladia muricata (Postels
& Ruprecht) J. Agardh

A small portion of a clump to show
the spiny character of the branches,
X 5. A common, low, densely tufted
or matted plant on rocks at rather
high intertidal levels along the entire
Pacific Coast.

Figure 66

39b Medulla more or less parenchymatous. Fig. 67 40

Fig. 67. Hypnea sp.

A transection of a thallus to show the
parenchymatous type of structure, X 30.
Habit drawings of various Hypnea species
'^ are shown in figures 68 and 71.

Figure 67

40a Thallus bearing occasional conspicuous sickle-shaped (hamate)
structures 41

40b Thallus without sickle-shaped (hamate) parts 42

60

HOW TO KNOW THE SEAWEEDS

41a Hamate structures terminal on main branches; lateral branchlets
relatively sparse, irregular in length. Fig. 68. .Hypnea musciiormis

Fig. 68. Hypnea musciiormis (Wulfen) Lamour-
oux

A small upper part of a plant, X 1.5, show-
ing the hamate branch tips and the irregular,
unequal lateral branchlets. This tropical plant
ranges northward to Massachusetts in warm,
protected places. Other species of the genus
lack hamate tips and key out at step 43b.

Figure 68

41b Hamate structures lateral on main branches; lateral branchlets
relatively uniform in length. Fig. 69 . Bonnemaisonia

Fig. 69. Bonnemaisonia hamifera Hariot

A small part of a plant to show the lateral
hamate branch and the relatively uniform slen-
der, lateral branchlets, X 3.6. An occasional
to common epiphyte in spring in southern New
England and also in southern California. An-
other species, B. nootkana (Esper) Silva, occurs
from central California northward.

Figure 69

42a Thallus bearing short, simple or compound spine-like branchlets
43

42b Thallus smooth, without specialized spine-like branchlets 44

61

HOW TO KNOW THE SEAWEEDS

43a Short branchlets much reduced, compound but not forked or stel-
late. Fig. 70 Acanthophora spicifera

Fig. 70. Acanthophora spicifera (Vahl) Borgesen

A small portion of a densely branched form to
show the compound, short spine-hke branchlets,
X 5. This widely distributed tropical species has
been known in the Caribbean Sea since it was
described in 1799 from the Virgin Islands. It is com-
monly encountered in infratidal waters of Florida.
Another species occurs in the Florida keys, but is
rare.

Figure 70

43b Short branchlets sunple, forked or stellate. Fig. 71

Hypnea (in part)

Fig. 71. Hypnea spp.

A. Hypnea cornuta (Lamouroux)
]. Agardh. A small part of an axis
magnified X 6.4 to show the stel-
late branchlets. B. Hypnea cervi-
cornis ]. Agardh. Habit of a small
part of a matted plant showing
shell fragments attached by small
discs and simple, spine-like branch-
lets, X 2.4. Both of these are tro-
pical plants of Florida and the
Gulf Coast. Two or three other
species may be encountered in this
region as well as the distinctive
H. musciformis which appears in
the key at step 41a. Two other
species are frequent in southern
California during the summer.

Figure 71

62

HOW TO KNOW THE SEAWEEDS

44a Young growing points with short or long deciduous hairs around
the apical cell. Fig. 72 Chondria (in part)

Fig. 72. Chondria tenuissima (Goodenough &
Woodward) C. Agardh.

A small portion of a plant to show the
branched, deciduous hairs aggregated around
the growing apices and the spindle-shaped
branches. X 5. This is the coarser of the two
common species of Chondria with emergent
apices along the Atlantic coast as far north as
New England. Two other species occur north
of New Jersey, several to the south of North
Carohna, and two species are abundant in
southern California. They vary from quite deli-
cate plants with main axes less than V2 mm.
thick to quite large, coarse plants 25 cm. tall
with axes 2 mm. thick.

Figure 72

44b Young growing points without deciduous hairs especially aggre-
gated around the apical cell. Fig. 18b 45

45a Medulla, especially the outer medulla, with slender, rhizoidal

filaments packed between the larger medullary cells. Figs. 73,74.

Gelidium (in part)

B

Figure 73

Fig. 73. Gehdium crinale (Turner) Lamouroux

Transections of parts of two different plants to show (A.) the ag-
gregation of rhizoidal filaments in the central region of the medulla,
and (B.) the aggregation in the outer region of the medulla. The latter
is the more common situation encountered in Gehdium. This is a
rather small, tufted plant reaching 5-7 cm. in height along both the

63

HOW TO KNOW THE SEAWEEDS

Atlantic and Pacific coasts. Most of the species of Gelidium are flat-
tened (step 185b), but the southern CaUfornia G. nudifrons and some
of the larger forms of G. ciinale are only slightly compressed as in-
dicated in the figures.

Fig. 74. Gelidium nuditrons Gard-
ner

A small portion of a plant about
18 cm. high to show the slender,
subcylindrical form and the rather
remote branches, X 0.8. Frequent
in southern California and some-
times abundant enough in the sub-
httoral Gelidium beds to be used
supplementarily for the making of
agar.

Figure 74

45b Medulla without rhizoidal filaments 46

46a Branching distichous or more or less unilateral. Fig. 75

MicTOcladia

Fig. 75. MicTOcladia coulteri Harvey

A small upper portion of a plant show-
ing the distichous branching of the slight-
ly compressed axes, X 3.2. Common along
the entire Pacific Coast, often together
with similar M. calif ornica Farlow. A third
species with unilateral branching, M. bore-
alis Ruprecht, occurs from central Cali-
fornia northward.

Figure 75

64

HOW TO KNOW THE SEAWEEDS

46b Branching multifarious 47

47a Parenchymatous medulla with a central core of relatively slender,
longitudinal filaments. Fig. 76 Cystoclonium puTpureum

Fig. 76. Cystoclonium purpureum (Hudson) Bat-
ters

A small upper portion of a female plant
showing the multifarious branching and the
presence of swellings in some branches repre-
senting cystocarps, X 1.2. Grows attached to
shells and rocks at low tide level, New Jersey
and northward. Mature plants reach 10-50 cm.
in height.

Figure 76

47b Medulla parenchymatous in character throughout 48

48a Older parts of axes with a thin cortex; ultimate branches of vari-
able length, indeterminate. Fig. 77 Dictyosiphon (in part)

Fig. 77. Dictyosiphon foeniculaceus (Hudson) Gre-
ville

A small portion of a plant about 40 cm. high to
show the indeterminate character of the branches,
X 1.2. This is a widespread and variable species
throughout the entire north Atlantic area, having
been described from England nearly 200 years ago.
It is a common epiphyte on various algae, especially
Chordaria, and reaches its best development in sum-
mer, although it may be found throughout the year.
In our area it is most abundant in New England,
but occurs as^far south as New Jersey. Some forms
tend to be hollow and may key out best under
step 95a.

Figure 77

65

1\

HOW TO KNOW THE SEAWEEDS

48b Older parts of axes with a thick cortex; ultimate branches usually

of similar length, at least more or less determinate. Fig. 78 ... .

Rhodomela

Fig. 78.

Small portions of two species of Rhodo-
mela to show the production of determin-
ate ultimate branchlets from the cyUndrical
axes. A. Rhodomela subfusca (Woodward)
C. Agardh, the most widespread of the
three New England species. The spring
form is illustrated in which the tufted ap-
pearance of the tips is prominent. This
^ aspect may in part be lost later in the sea-
B f\^ son by the eroding away of some of these
small branchlets. B. Rhodomela larix (Tur-
ner) C. Agardh, the common Pacific Coast
species from central CaUfornia northward.
A young axis is represented in which the
ultimate branchlets are much less abund-
ant and congested than in older plants.
Both figures X 1.2.

Figure 78

49a Thalli creeping; indeterminate (compound) branchlets alternating
regularly with small series of determinate (simple) branches. Fig.

79 Herposiphonia

Fig. 79. Herposiphonia
tenella (C. Agardh) Am-
bronn

Part of a creeping axis
showing attachment rhi-
zoids and the series of
three simple, erect, de-
terminate branches alter-
nating with single short,
compound indeterminate
branches, X 50. This is
the commonest of four
species of this genus oc-
curring from North Caro-
lina through Florida. Sev-
eral other species occur
along the Pacific Coast.

Figure 79

They are usually quite small plants but may be conspicuous as epi-
phytes or in low algal mats or turfs.

66

HOW TO KNOW THE SEAWEEDS

49b Thalli erect; branching varied,

50

50a Branching multifarious. Fig. 80 Polysiphonia

'^^^

Figure 80

Fig. 80. A species of Polysiphonia with four pericentral cells (only two
of which are usually visible) and showing some short trichoblasts
from the scar-cells.

Polysiphonia is a very large genus of relatively small and (or)
delicate plants of which about 20 species may be encountered along
the Pacific Coast and at least as many along the Atlantic. Some have
only four pericentral cells like Figure 80, while others have five to
many. The plants may be epiphytic or saxicolous and from as much
as 30 cm. tall to as little as a few millimeters. See also Fig. 54A.

50b Branching distichous .51

51a Percurrent axes clearly developed. Fig. 81 Pterosiphonia

Fig. 81. Pterosiphonia dendroidea (Mon-
tagne) Falkenberg

A. An erect axis to show the percurrent
character and regular, alternate, pinnate
branching, X 3.5. B. Detail of a single
compound pinna, X 35. This is a com-
mon small saxicolous plant along the
whole Pacific Coast. Several other species
occur from southern California northward,
but apparently there are none on the At-
lantic Coast.

Figure 81

67

HOW TO KNOW THE SEAWEEDS

51b Percurrent axes not clearly developed. Fig. 82 Pterochondria

Fig. 82. Pterochondria woodii (Har-
vey) Hollenberg

A. A small part of a plant about
10 cm. high to show absence of a
distinct percurrent axis and the rela-
tively wide spacing of the branches
compared to Pterosiphonia in Fig. 81,
X 3.5. B. Detail of a compound ulti-
mate branchlet, X 16. A common
epiphyte on Cystoseira and other
large algae along the whole Pacific
Coast.

Figure 82

52a Thallus with midrib and (or) veins

53

52b Thallus without midrib or veins 55

53a Plants green, with palmate veins. Fig. 83 ... . Anadyomene stellata

Fig. 83. Anadyomene stel-
lata (Wulfen) J. Agardh

An entire small plant,
X 0.8, to show the pal-
mate veins and membran-
ous character. Blades may
reach a height or spread
of 5-7 cm. It is a tropical
plant of southern Florida.

Figure 83

68

HOW TO KNOW THE SEAWEEDS

53b Plants reddish, with a midrib 54

54a Thallus simple, without macroscopic lateral veins. Fig. 84

Grinnellia aznericana

Fig. 84. Grinnellia americana (C. Agardh)
Harvey

A single blade of an asexual plant to
show the simple, ruffled character, ab-
sence of lateral veins from the midrib,
and the small tetrasporangial sori, X 0.8.
This is an attractive plant of pleasing color
and form which is sure, to appear in sum-
mer collections from our north central At-
lantic Coast. It inhabits warm quiet water
in wading depths at low tide, maturing and
disappearing by late summer. It may be
encountered from South Carolina to as far
north as northern Massachusetts.

Figure 84

54b Thallus pinnately lobed; midrib with distinct, opposite lateral veins.
Fig. 85 Phycodrys

Fig. 85. Phycodrys rubens (Hudson)
Batters

A single blade to show lobing and
veination, X 1. This is the only spe-
cies of the genus on the Atlantic Coast,
occurring from New lersey northward,
especially north of Cape Cod. The
common Pacific species is P. setchellii
found in California and Oregon.

Figure 85

69

HOW TO KNOW THE SEAWEEDS

55a Thallus greenish 57

55b Thallus reddish or purplish 56

56a Thallus mono- to distromatic throughout, purplish; growth inter-
calary; reproductive structures in marginal areas, not forming
spots. Fig. 86 PoTphyra

Figure 86

Fig. 86. Porphyra perforata J. Agardh

An entire small plant to show the ruffled character resulting from
intercalary growth of the membranous blade, X 0.75. This monostro-
matic species is common on middle intertidal rocks along the whole
Pacific Coast. It is an edible species similar to the porphyras cultivated
for food in Japan. It has been extensively harvested in some parts of
CaUfornia, as much as 300,000 dry pounds being collected in a year.
Several other species of the genus occur as epiphytes or on rocks
along the Pacific and Atlantic coasts but must be identified specifically
by means of the various local floras.

70

HOW TO KNOW THE SEAWEEDS

56b Thallus monostromatic at the margins and of more than one cell
in thickness in older mid-parts and lower parts, reddish in color;
growth marginal; reproductive organs scattered over the blades
in small circular or elongate spots. Fig. 87 MyriogTamine

Fig. 87. Myriogiamme spectabilis (Eaton) Kylin

A single forked blade of a tetrasporangial
plant showing the elongated tetrasporangial
sori, X 0.6. This is our largest and common-
est species of Myriogramme. It normally grows
below low tide level along the California coast
and is to be looked for in beach drift. There
are several other localized species on the Pa-
cific Coast.

ooooooooop

0000000000

Figure 87

57a Thallus 2 cells thick. Fig. 88 A Ulva

57b Thallus 1 cell thick. Fig. 88 B Monos^roma

Fig. 88. Transections of Ulva
(A.) and of Monostioma (B.) to
show different appearance of
monostromatic and distromatic
structure.

A considerable number of spe-
cies of each of these genera oc-
curs both on the Atlantic and
Pacific coasts. The species are
widespread and in many cases
cosmopolitan. The best means of
identifying our Pacific species at
present is found in the volume
by Setchell and Gardner, 1920, while Taylor, 1937, treats most of the
Atlantic species. All of the members of each of these genera are thin,
expanded, membranous plants varying in size from a centimeter or
two up to more than two meters. In form they resemble the Porphyra
plant shown in Figure 86.

oooooooooo

B

Figure 88

71

HOW TO KNOW THE SEAWEEDS

58a Thallus of varied form and branching, but without cellular sep-

tation. Figs. 89, 90 59

Fig. 89. Caulerpa
tastigiata Mon-
tagne

Part of a plant
extracted from a
turf to show the
prostrate and
erect parts and
t h e descending
rhizoids, all with-
out cellular sep-
t a t i on , X 7.
Sandy places in
Florida.

Figure 89

Fig. 90. Caulerpa
species to show
varied form
and branching.

A. Cau i e r p a
verticillata J.
Agardh. A small
part of a plant,
X 5. B. Caulerpa
racemosa (Forsk-
al) J. Agardh. A
small portion of
a plant. X 1.5.
Both of these spe-
cies and about
eleven others are
to be found in
the warm waters
of the Florida
coasts. Some of
them are flat-
tened and either
subsimple or pin-

nately branched. These will be encountered farther on in the key at

steps 148 and 160.

Figure 90

72

HOW TO KNOW THE SEAWEEDS

58b Thallus regularly or irregularly septate.

60

59a Thallus traversed internally by a network of trabeculae. Figs.
89, 90, 91 Caulerpa (in part)

Fig. 91. Caulerpa sp.

Transection of an axis to show the internal
network of trabeculae, X 9.

Figure 91

59b Thallus not traversed internally by a network of trabeculae. Fig.
92 Bryopsis

Fig. 92. Bryopsis pennata Lamouroux

The terminal portion of a young axis, X
22. At least four species of this genus are
to be found along the. Atlantic coast, two of
them (B. hypnoides Lamouroux and B. plumosa
(Hudson) C. Agardh) extending as far north
as New England. Although no species of
Caulerpa is encountered on our Pacific Coast,
several kinds of Bryopsis may be found there
including the two New England species men-
tioned above. Both pinnate and multifari-
ous branching occur in the genus.

Figure 92

60a Branching radially symmetrical; branchlets whorled 61

73

iy

/•

HOW TO KNOW THE SEAWEEDS

60b Branched or unbranched; if branches present, these not whorled.62

61a Gametangia between (enclosed by) cells of secondary whorls.
Fig. 93 Dasycladus vermicularis

Fig. 93. Dasycladus vermicularis (Scopoli) Krasser

A single lateral branchlet showing the game-
tangium enclosed by cells of a secondary whorl,
X 17. Growing on shells, coral, etc., in Florida.

Figure 93

61b Gametangia outside of cells of secondary whorls. Fig. 94

Batophoia oerstedi

m

Fig. 94. Batophora oerstedi J.
Agardh

A. An entire plant of a dense-
ly branched form closely resem-
bling Dasycladus but showing
near the tip an indication of the
whorled arrangement of the later-
al branchlets, X 1.1. B. A single
lateral branch bearing three game-
tangia, X 17. Common in south-
ern Florida and west to Texas.

Figure 94

74

HOW TO KNOW THE SEAWEEDS

62a Branched filaments consisting of a very few large, vacuolate cells.
Fig. 95 Valonia (in part)

Fig. 95. Valonia aegagropila
C. Agardh

A small part of a matted
plant, X 3. Valonia is a tropi-
cal genus of several species
of variable form from single,
very large cells (See Fig. 163)
to clusters or coarse filaments
of large cells. Five species
may be encountered in Flori-
da.

Figure 95

62b Filaments branched or unbranched, of many cells 63

63a Filaments unbranched, rarely branched, or with few short, simple
branchlets 64

63b Filaments normally much-branched 68

64a Cells with a single parietal, bracelet-shaped chloroplast. Fig. 96.

Ulothrix

Figure 96

Fig. 96. Ulothrix implexa Kiitzing

A small portion of a filament to show cell shape and form of the
chloroplast, X 600 (Note the very small diameter).

Grows as soft, silky tufts on rocks or woodwork along both coasts.
There are three other species which may be encountered in our cooler,
northern waters.

75

HOW TO KNOW THE SEAWEEDS
64b Cells with greatly reticulate or fragmented chloroplasts 65

65a Filaments attached at the base

66

65b Filaments free, floating or entangled 67

66a Rhizoids, if present, produced only from the basal cell. Fig. 97 . .
Chaetomorpha (in part)

Fig. 97, Chaetomorpha antennina (Bory) Kiitzing

A. Part of a young plant to show basal attach-
ment and presence of rhizoids arising from the
basal cell, X 9. B. A portion of a tuft, X 1.5.
This is a southern CaUfornia representative of this
genus which occurs widely on exposed rocks along
both coasts. (See also Fig. 100.) It shows the tufted,
gregarious habit of the filaments of the basally at-
tached members of this genus of which C. aerea
(Dillwyn) Kiitzing is a more widespread but much
more slender species. C. melagonium (Weber &
Mohr) Kiitzing, from New England, is a similarly
coarse species.

Figure 97

76

HOW TO KNOW THE SEAWEEDS

66b Rhizoids produced from several cells near the base. Fig. 98

Uiospora

Fig. 98. Urospoia penicilliformis
(Roth) Areschoug

A. The basal part of a plant to
show the rhizoids arising from
several lower cells, X 220. B., C.
Two stages in the production of
zoospores in older parts of fila-
ments, X 300. This is perhaps
the commonest of several species
occurring in New England and
along the Pacific Coast from cen-
tral California northward. They
grow on rocks or woodwork as
fine, green, silky tufts up to 10
cm. long or more.

Figure 98

67a Filaments 70 ^ or less in diameter, unbranched, or with a few
short lateral branches. Fig. 99 Rhizocionium

DI

1

Figure 99

Fig. 99. Rhizocionium kerneri Stockmayer

A small part of a filament to show the diameter and cell shape,
X 235. This is one of several species which may be found widely
along any of our coasts.

77

HOW TO KNOW THE SEAWEEDS

67b Filaments 100-1000 a in diameter, unbranched. Fig. 100

Chaetomorpha (in part)

Fig. 100. Chaetomorpha hnum (Miiller)
Kiitzing

A small part of an entangled fila-
ment, X 4. One of three free, drifting
or entangled species occurring along
the Atlantic Coast. Others may be
found on Pacific shores of which one
of the most striking is the southern
CaHfornian C. torta (Farlow) McClatchie
which is very coarse (over 1 mm.) and
strongly coiled or twisted.

Figure 100

68a Color greenish, usually grass green

69

68b Color reddish or brownish, not grass green or greenish 71

69a Lower parts of plants held together by rhizoidal, hooked or spine-
like branchlets. Fig. 101 Spongomorpha

Fig. 101. Spongomorpha spp.

A. Spongomorpha coahta
(Ruprecht) CoUins. The end
of a branch showing a hook,
X 30. Central CaUfornia and
northward. B. Spongomorpha
arcta CDillwyn) Kiitzing. A
lower part of an axis showing
the production of descending,
entwining rhizoids, X 30. This
plant forms hemispherical tufts
on exposed rocks along the
New England coast. Several
other species occur along the
p. ,-,, northern shores of both coasts.

Figure 101

78

HOW TO KNOW THE SEAWEEDS

69b Filaments free, not held together by special hranchlets, although
sometimes somewhat twisted 70

70a Cell walls present at the base of each branch. Fig. 102

Cladophora

Fig. 102. Cladophora spp.

A. Cladophora trichoto-
ma (C. Agardh) Kiitzing.
A small upper, branched
portion of a plant, X 25.
A common, coarse, tufted
species along the Pacific
Coast. A dozen or more
other species may be en-
countered along the Pa-
cific and may be identi-
fied through the use of
keys in Setchell & Gard-
ner, 1920. B. Cladophora
cilbida (Hudson) Kiitzing.
A small portion of a
branched axis, X 50. This
is an example of one of
the several very delicate
forms which may be
found either along the
Atlantic or Pacific coasts.
This one, although so deli-
cate, may reach 10 cm.
in height.

Figure 102

79

HOW TO KNOW THE SEAWEEDS

70b Base of upper branches usually without a cross wall. Fig. 103...
Cladophoropsis membranacea

Fig. 103. Cladophoropsis membranacea
(C. Agardh) Bbrgesen

A small part of a plant, X 9.6. The
filaments are mostly 100 to 200 ^ in
diameter. Dry, pressed specimens will
appear rather lustrous against the pa-
per. This is a tropical plant which may
be found forming dense, soft patches
and tufts on rocks in rather quiet water
in Florida.

Figure 103

71a Thallus reddish in color; growth from an apical cell 74

71b Thallus brownish in color; growth intercalary, not from an apical
cell 72

72a Erect filaments all more or less alike; plants epiphytic or saxi-
calous < ' ^

80

HOW TO KNOW THE SEAWEEDS

72b Erect filaments of two kinds: crowded, short, moniliiorm filaments
below, and long, straight, free filaments extending above; plants
epiphytic. Fig. 104 Elachista

Fig. 104. Elachista fucicola (Velley) Areschoug

A very small bit of a sterile tuft showing the
two kinds of filaments, X 80. This is a common
epiphyte on coarse algae from New Jersey north-
ward and from central Oregon northward. Two
other species occur on the New England coast on
Chondrus, Ascophyllum, and other coarse algae.
The tufts are small, usually under 2 cm. high, but
are often abundant and conspicuous.

Figure 104

73a Reproductive organs in a series in the middle of a filament. Fig.
105 Pylaiella

Figure 105

Fig. 105. Pylaiella litoralis (Linnaeus) Kjellman

A small portion of a fertile filament showing the serial and inter-
calary production of unilocular sporangia, X 180. Commonly 5-25 cm.
long on various substrates from New Jersey northward and from cen-
tral California northward along the Pacific. Other species may occur,

but are rare or of local distribution.

J

81

HOW TO KNOW THE SEAWEEDS

73b Reproductive organs lateral or terminal on the filaments. Fig. 106.
Ectocarpus

Fig. 106. Ectocarpus spp.

Figure 106

Three different exam-
ples of types of plurilo-
cular sporangia charac-
teristic of Ectocarpus axe
shown (A-B. X 200; C, X
225). In C the stippled
cells indicate those in
which intercalary division
has most recently occur-
red. Ectocarpus is a large
genus of relatively small
plants. One or more spe-
cies may be found almost
anyvvhere, often as epi-
phytes, but except for a
few kinds they do not
reach conspicuous size.
The local floras must be
used for the identification
of species.

82

HOW TO KNOW THE SEAWEEDS

74a Branching opposite, at least in major part. Fig. 1Q7. . Antithamnion

Figure 107

Fig, 107. Antithamnion sp,

A small upper part of a fertile plant showing the opposite
branching and the position of tetrasporangia, X 80. This is a large
genus of very delicate, beautiful plants which are commonly epi-
phytic. Some species are quite small, while others reach 20 cm. in
height. They may be encountered on any part of our coasts and
must be identified specifically through the use of the various local
floras.

74b Branching alternate, dichotomous or irregular (sometimes partly
or wholly opposite in Spermothamnion turneri) 75

83

HOW TO KNOW THE SEAWEEDS

75a Branching regularly alternate, normally with a branch from each
cell of the main axis, at least above. Fig. 108 76

Figure 108

Fig. 108. Callithamnion rupicolum Anderson

A small upper portion of a fertile plant showing regular alternate
branching from each cell of the main axis and the production of tetra-
sporangia, X 120. A common small species along the Cahfornia coast.

This is a moderately large genus of deUcate plants of which one
or more species may be found along most any part of our coasts.
Some of the coarser and more or less corticated species will key out
under step 31b.

84

HOW TO KNOW THE SEAWEEDS

75b Branching not regularly alternate, or at least without a branch
from each cell of the main axis. Fig. 109 77

Fig. 109. Spermothamnion turneri
(Martens) Areschoug

A small upper portion of a fer-
tile plant showing multifarious
branching and presence of axial
cells without branches, X 75. This
is a common small epiphyte on
Chondrus and Phyllophora in in-
fratidal waters along the Atlantic
Coast south of Cape Cod. It may
be 2 to 5 cm, tall and is usually
found in summer in tetrasporic
condition. Note that another spe-
cies of Spermothamnion from the
Pacific Coast (See Fig. 112) has
distinctive polysporangia.

Figure 109

76a Asexual plants bearing tetrasporangia. (See Fig. 108)

Callithamnion

(In part; see also step 31b and Figure 52)

85

HOW TO KNOW THE SEAWEEDS

76b Asexual plants bearing polysporangia. Fig. 110. . . .Pleonosporium

Figure 1 10

Fig. 110. Pleonosporium dasyoides (J. Agardh) De Toni

A. A small upper part of a sterile plant showing the regular, alter-
nate branching, X 56. B. A polysporangium,. X 72. This is our larg-
est member of the genus, reaching 20 cm. in height along the central
Cahfornia coast. The somewhat smaller P. horreri (J. E. Smith) NdgeU
occurs from Florida to Cape Cod. Several other relatively local species
may be found along the Pacific Coast.

86

HOW TO KNOW THE SEAWEEDS

77a Branching more or less clearly dichotomous or trichotomous. the

cells large enough to be visible to the naked eye. Fig. Ill

Grifiithsia

Fig. 111. Grifiithsia pacifica Kylin

A small upper part of a male
plant, X 6.4, showing the large
cells and dichotomous branching.
This is the commonest and most
widespread species along the Pa-
cific Coast from Puget Sound to
southern California. G. globulifera
Harvey is common along the At-
lantic south of Cape Cod and has
cells up to 1.5 mm. in diameter.
G. tenuis C. Agardh, with the same
range, is 5-20 cm. tall but with
slender, elongate cells about 300
jji in diameter or less.

Figure 1 1 1

77b Branching irregular, unilateral, alternate, or sometimes opposite;
cells microscopic. Figs. 109, 112 SpeTmothamnion

Fig. 112. Spermothamnion snyderae Farlow

A small portion of a plant bearing poly-
sporangia, X 80. This is the only species of
the genus occurring along the Pacific Coast.
It is a small plant to 5 cm. high growing in
dense tufted masses on rocks from central to
southern Cahfornia. Unlike the Atlantic S. tur-
neri, it has polysporangia. S. humeri, our only
Atlantic species, is of similar stature, but is
epiphytic.

Figure 1 1 2

87

HOW TO KNOW THE SEAWEEDS

78a Thallas perforated, net-like. Fig. 113 HydToclathrus clathratus

Fig. 113. Hydroclathius clathra-
tus (Bory) Howe

A small portion of a reticulate
plant, X 1.5. This is a species
of wide tropical distribution
which may be encountered in
our area along the Florida coast
and occasionally in southern-
most California.

Figure 1 1 3

78b Thallus crustose, not perforated, not net-like

79

79a Thallus reddish to purplish when wet

80

79b Thallus dark brownish in color when wet, at least not reddish or
purplish 81

80a Thallus firmly adherent, composed of very small, cuboidal cells;
tetrasporangia irregularly zonate, borne in cavities. Fig. 114....
Hildenbrandia prototypus Nardo

Fig. 114. Hildenbrandia prototypus Nardo

A vertical section through a tetraspor-
angial conceptacle showing the arrange-
ment of the sporangia and the small,
cuboidal vegetative cells, X 150. Com-
mon along both coasts as a .red film on
intertidal rocks and on shells.

Note the absence of rhizoids from the
basal cell layer in comparing with Pey-
ssonelia below.

Figure 1 14

88

HOW TO KNOW THE SEAWEEDS

80b Thallus attached by rhizoids on the under side; cells not especially
small; tetrasporangia cruciate, borne in a superficial layer. Fig.
115 Peyssonelia

Fig. 115. Peyssonelia sp.

A vertical section through a tetraspor-
angia! thallus showing the rhizoids from
the basal cell layer and the position of
a tetrasporangium in a special, nemathe-
cial, superficial layer (nemathecium). Spe-
cies of this genus may be encountered en-
crusting rocks at low intertidal levels, or
infratidally, on either of our coasts.

ooooooooooooo
mOOQOOOOOOOO

Figure 1 1 5

81a Crusts relatively thin, firm, somewhat brittle or woody. Fig. 116.
Ralisia

Figure 1 16

Fig. 116. Ralisia sp.

An example of a loosely attached form
showing concentric lines of growth, X 1.
A number of species occur on rocks, some
of them very firmly attached and so flat,
thin, and dark that they may be mistaken
by the layman for patches of tar. Some
times they completely cover rock surfaces
to give the intertidal area a dark brown
color. They cne widespread along the whole
Pacific Coast and in the cooler northern
waters along the Atlantic. They are usually
at rather high intertidal levels and are re-
sistant to considerable desiccation.

89

HOW TO KNOW THE SEAWEEDS

81b Crusts thick, convoluted, spongy. Fig. 117. .Petrospongium rugosum

Fig. 117. Petrospongium rugosum (Oka-
mura) Setchell & Gardner

An entire plant showing the convoluted
appearance, X 1. Common on upper in-
tertidal rocks of central and southern Cali-
fornia.
Figure 1 1 7

82a Thallus not erect, but sub-spherical, hemispherical, or expanded
and convoluted; surface smooth or warty 83

82b Thallus not as above, erect

85

83a Thallus green, composed of macroscopic cells. Fig. 118

Dictyosphaeria cavernosa

B

Figure 1 1 8

Fig. 118. Dictyosphaeria cavernosa (Forskal) Borgesen

A. Habit of an entire small plant with a portion cut out to show
the hollow character, X 3.2. B. Detail of several of the macroscopic
cells, X 12.8.

Frequent on exposed rocks along the Florida coast.

90

HOW TO KNOW THE SEAWEEDS

83b Thallus brown 84

84a Thallus slippery, structurally composed of branched filaments.
Fig. 119 Leathesia

Fig. 119. Leathesia difformis (Linnaeus)
Areschoug

A small portion of the outer tissues of a
plant to show the filamentous structure
which includes vegetative filaments, para-
physes, gametangia and a hair, X 240.
This is a common, small, subspherical plant
on rocks and algae, especially on Coral-
lina. It occurs along the entire Pacific
Coast and in the cooler Atlantic waters
north of North Carolina. Only one other
local California species of the genus grows
within our area.

Figure 119

84b Thallus not slippery, crisp, structurally composed of parenchymat-
ous cells. Fig. 120 Colpoznenia sinuosa

Fig. 120. Colpomenia sinuosa
(Roth) Derbes & SoUer

Habit of a subspherical plant,
X 1.5. This plant may be en-
countered in Florida and in the
summer along most any part of
the Pacific Coast especially in
waters subject to marked warm-
ing. It is exceedingly variable,
from small, spherical epiphytic
plants to large, broad, prostrate
or floating ones in which the hol-
low form has reached a state of
collapse.

Figure 120

91

HOW TO KNOW THE SEAWEEDS

85a Thallus a simple sac to 3 cm. in diameter. Figs. 121, 122

86

85b Thallus not a simple sac

87

88a Plant saxicolous. Fig. 121 Halosaccion glandiiorme

Fig. 121. Halosaccion glandiiorme (Gmelin)
Ruprecht.

An entire medium size plant, X O-^S. Com-
mon on rocks along the Pacific Coast except
in southern CaUfornia. The large finger-
shaped sack is filled with water when the
plants are young and intact. When com-
pressed, however, the water spurts out from
microscopic openings near the tip in a num-
ber of very fine jets. Old plants become
eroded and the sack more or less filled with
sand. This curious alga, described from Kam-
schatka in 1768, was one of the first sea-
weeds recorded in the scientific literature from
the North Pacific.

Figure 121

92

HOW TO KNOW THE SEAWEEDS

86b Plants epiphytic; sacs sometimes so flattened as to appear blade-
like. Fig. 122 Coilodesme

Figure 122

Fig. 122. Coilodesme rigida Setchell & Gardner

Several plants growing on a piece of Halidrys, X 0.8 Five species
occur more or less locally along the Pacific Coast. This one is occa-
sional in southern California while the commonest and most wide-
spread one, C. califoTnica (Ruprecht) Kjellman occurs on Cystoseiia
from central CaHfornia northward.

87a Thallus hollow-tubular, at least in older parts, and of uniform
structure throughout. Fig. 124 88

87b Thallus not of uniform structure throughout, with differentiation
of parts 96

93

HOW TO KNOW THE SEAWEEDS

88a Thallus regularly constricted and with diaphragms at the con-
strictions. Fig. 123 Champia

Figure 1 23

Fig. 123. Champia parvula (C Agardh) Harvey

A portion of a plant of caespitose form showing the constrictions
of the thallus at the diaphragms, X 7. This species is frequent along
the Atlantic coast from Florida to Cape Cod, usually in dense tufts 3-7
cm. tall. The more strongly constricted C. salicornioides Harvey may
be found in Florida.

88b Thallus smooth, or if constricted, without diaphragms 89

94

HOW TO KNOW THE SEAWEEDS

89a Wall of tubular thallus only 1 cell thick (Fig. 124); color greenish.
Fig. 125 EnteromoTpha

Fig. 124. Enteromorpha sp.

A transection of an axis to show the
single layer of cells and the hollow struc-
ture.

Figure 124

Fig. 125. Enteromorpha
spp.

A. Enteromorpha tubu-
losa (Kiitzing) Kiitzing. A
portion of an unbranched,
hairlike filament, X 7.
B. Enteromorpha clathrata
(Roth) Greville. A small
part of an axis with sev-
eral uniseriate branchlets,
X 80. This genus con-
tains some of the most
widespread and cosmo-
politan of the marine al-
gae. Many species may
be found on either coast,
and in a great diversity
of habitats. Most of them
are exceedingly variable
in form and some are no-
toriously difficult to iden-
tify. E. hnza (Linnaeus) J.

Agardh is a species which is flattened in upper parts like Ulva, but

hollow at the base like Enteromorpha.

Figure 125

89b Wall of tubular thallus more than 1 cell thick; color brownish or
reddish 90

95

HOW TO KNOW THE SEAWEEDS

90a Thallus little or not at all branched except at the base

91

90b Thallus branched throughout 94

91a Plants less than V2 meter long; hairs, if present, in tufts,

92

91b Plants usually more than V2 meter long (1-5 meters); thallus sur-
face covered with fine hairs, at least on young parts. (See Fig.
32) Chorda (in part)

92a Thallus unconstricted; groups of sporangia and hairs appearing
as dark flecks. Fig. 126 Asperococcus echinatus

Fig. 126. Asperococcus echinatus (Martens)
Greville

An entire plant, X 1.5, showing the
abundant small tufts of hairs and sporan-
gia. This species will be encountered as a
common epiphyte on various species of
Fucus along the New England coasts. It
also occurs on other substrates in some-
what sheltered places below low tide level.
It will not be found throughout the year,
for the plants mature and fruit during the
spring and by midsummer have largely de-
cayed and disappeared.

Figure 126

92b Thallus constricted or unconstricted, without groups of sporangia
and hairs aggregated in tufts and appearing as dark flecks .... 93

96

HOW TO KNOW THE SEAWEEDS

93a Thallus commonly constricted, brown in color, totally unbranched.
Fig. 127 Scytosiphon lomentaria

Fig. 127. Scytosiphon lomentaria (Lyngbye) C.
Agardh

An entire plant of one of the larger, clearly
constricted forms, X 0.5. This is a common
plant along both the Pacific and Atlantic coasts,
and occurs in a variety of forms in different
habitats. Some forms, especially at high inter-
tidal levels may be unconstricted. Among these
there are both slender cylindrical forms and
some which are quite strongly flattened, al-
though hollow. The brown color and unbranched
habit are distinctive.

93b Thallus not constricted although often of
somewhat irregular diameter, reddish or
purplish in color, occasionally branched at
the base and sometimes proliferous above.
Fig. 128 Halosaccion Tamentaceum

Figure 127

Fig. 128. Halosaccion ramentaceum (Linnaeus) J.
Agardh

Part of a plant showing branching of lower
stipe part and the beginning of some prolifera-
tions from one tubular axis, X 0.8. Plants of this
species are gregarious on stones and shells near
low water mark from northern Massachusetts
through Maine. They may reach 30-40 cm. long.

Figure 128

97

HOW TO KNOW THE SEAWEEDS

94a Axes and (or) branches 2-5 mm. in diameter; cortex, as seen in
transection, composed of anticlinally arranged, branched filaments
of short cells. Fig. 129 Dumontia incrassata

Figure 129

Fig. 129. Dumontia incrassata (Miiller) Lamouroux

An entire, medium size plant, X 1, showing the hollow branches
of rather large diameter. Grows in tide pools or just below low tide
level along the New England coast from Rhode Island northward. The
species is especially interesting in that it apparently was introduced
to the New England coast and became estabUshed only a few decades
ago. The first collection was made at South Harpswell, Maine in June,
1913. Since then it has been found more and more commonly at a
number of locaUties from Rhode Island to Nova Scotia.

98

HOW TO KNOW THE SEAWEEDS

94b Axes and branches usually 1 mm. or less in diameter; cortex as
seen in transection composed of more or less isodiametrical cells
without evident arrangement in rows or filaments 95

95a Thallus brownish; percurrent axes evident; medulla only partially
hollow, or only in older parts. (See Fig. 77). . Dictyosiphon (in part)

95b Thallus reddish; percurrent axes usually not evident; medulla hol-
low throughout, although sometimes with filaments around the
cavity. Fig. 130 Lomentaria baileyanc

Figure 1 30

Fig. 130. Lomentaria haileyana (Harvey) Farlow

Part of a plant to show the slender form and lack of percurrent
axes, X 1.2. This species is usually loosely tufted, 3 to 7 cm. high,
in sheltered places from Cape Cod to Florida.

99

HOW TO KNOW THE SEAWEEDS

96a Thallus without flattened parts.

97

96b Thallus with both flattened and cylindrical parts,

98

97a Solid axes bearing hollow, subspherical, grape-like branchlets.
Pig. 131 BotTyocladia pseudodichotoma

Figure 131

Fig. 131. Botryocladia pseudodichotoma (Fallow) Kylin

Part of Q fertile, cystocarpic plant, X 1. Although usually of sub-
littoral occurrence, this plant may frequently be found in beach drift
along the entire Pacific Coast. It is conspicuous because of its pecuHar
form and bright red color, and has received the common name of
"Sea Grapes." In making pressed specimens the collector will do well
to puncture the hollow, turgid vesicles in order to allow them to flatten
in the press as their liquid contents are extruded. Otherwise they may
burst in the process to give an unnatural appearance to the dry
specimen.

100

HOW TO KNOW THE SEAWEEDS

97b Solid axes bearing hollow, cylindrical, constricted branchlets with
diaphragms at the constrictions. Fig. 132 .. Gasfrocionium coulteri

Fig. 132. Gastroclonium coulteri (Harvey) Ky-
lin

A small upper portion of a plant to show
the solid axis and the hollow, constricted, lat-
eral branchlets, X 1.6. Frequent on rocks
along virtually the entire Pacific Coast. The
degree of development of the hollow lateral
branchlets varies so that one should expect
occasionally to find specimens in which these
are scanty, much reduced, or otherwise in-
conspicuous. Close inspection, however, will
invariably reveal the transverse septa at the
constrictions in some of these hollow branch-
lets.

Figure 132

98a Thallus with a single large, hollow bulb (pneumatocyst) at the
end of a long, unbranched stipe (See Fig. 134) 99

98b Plants with more than one hollow structure,

100

101

HOW TO KNOW THE SEAWEEDS

99a Apex of pneumatocyst with four short, flattened branches which
are four to five times dichotomous. Fig. 133. .NeTeocystis luetkeana

Fig. 133. Nereocystis luetkeana (Martens) Pos-
tals & Ruprecht

A pnaumatocyst showing tha bulbous, tar,
minal swelling and four dichotomous, blade-
bearing branches, X 0.2. This is a giant kelp
which grows in great beds from rocks 30 to
50 feet below the surface, sending up the
pneumatocysts and blades which float out at
the surface. Common along the Pacific Coast
except in southernmost California.

Figure 1 33

99b Apex of pneumatocyst with a single large antler-like, forked
branch. Fig. 134 Pelagophycus porra

Fig. 134. Pelagophycus porra (Leman) Setchell

Habit of an entire plant, X 0.04, showing the holdfast, long, ris-
ing stipe and blade-bearing terminal pneumatocyst. This is probably
our most spectacular large Pacific coast kelp. It occupies habitats
outside the Macrocystis beds in somewhat deeper water and is avoided
by the commercial kelp cutters. Its range extends from Point Concep-
tion, CaUfornia southward into Mexico.

102

HOW TO KNOW THE SEAWEEDS

Figure 134

103

HOW TO KNOW THE SEAWEEDS

100a Vesicles produced by inflation of portions of flat, dichotomous
blades. Fig. 135 Fucus vesiculosus

Fig. 135. Fucus vesiculosus Lin-
naeus

An upper part of a plant to
show the dichotomous branching
and the vesicles which are usu-
ally paired, X 0.56. This is one
of the commonest of all the ma-
rine algae along the Atlantic
Coast from North Carolina north-
ward. Fucus evanescens C. Agardh
is a north Pacific coast species
having vesicles, but other mem-
bers of this common genus lack
vesicles and are treated elsewhere
in this key (See step 135).

Figure 135

100b Vesicles not produced in flat, dichotomous blades

101

101a Vesicles borne on either side of flat, ligulate, percurrent axes.
Fig. 136 Egregia

Fig. 136. Egregia laevigata Setchell

A. Habit of an entire plant, X 0.04. B. A small portion of one
of the flat axes bearing lateral blades many of which have vesicles at
their bases, X 0.5. This is one of the large brown algae of central
and southern California which attracts the most attention because of
its pecuHar form and its abundance along some bathing beaches.
It has been called the "Feather Boa." Another species, E. menziesii
(Turner) Areschoug, is similar in habit but occurs from central Cali-
fornia northward to Canada.

104

HOW TO KNOW THE SEAWEEDS

Figure 136

105

HOW TO KNOW THE SEAWEEDS
101b Vesicles not distichous 102

102a Vesicles borne in series 103

i02b Vesicles solitary 104

103a Seriate vesicles compressed. Fig. 137 Halidrys dioica

v:^>'^^?^ -^k.. A>^iw^-

Figure 137

Fig. 137. Halidrys dioica Gardner

A single series of vesicles showing the flattened character, X 1.8.
Note that some forms may have a less pronounced blade-like develop-
ment than is shown in the figure.

Halidrys is vegetatively similar to Cystoseira (See Fig. 138) and
may be confused with members of that genus in the absence of the
readily recognizable vesicles. The only species, H. dioica, is restricted
to southern Cahfornia, while species of Cystoseira extend farther north.

103b Seriate vesicles spherical and catenate. Fig. 138 Cystoseira

Fig. 138. Cystoseira osmundacea (Menzies) C. Agardh

Habit of a short, intertidal form of this species to show the hold-
fast, leaf-Hke blades, and catenate vesicles, X 0.5. This is the most
widespread of three species of this genus on our Pacific Coast, ex-
tending throughout CaHfornia to central Oregon. Many plants, espe-
cially infratidal ones, are much more lax in habit than the plant illus-
trated. Central California plants are reported to reach a length of 7.5
meters. Entangled pieces of Cystoseira are often found in drift along
California beaches.

106

HOW TO KNOW THE SEAWEEDS

Figure 138

107

HOW TO KNOW THE SEAWEEDS

104a Main axes here and there much inflated to form the float blad-
ders. Fig. 139 Ascophyllum nodosum

Fig. 139. Ascophyllum nodosum (Linnaeus) Le Jolis

An upper portion of a fertile plant showing hol-
low vesicles in the main axes and the stalked, club-
shaped, deciduous, receptacular branchlets, X 0.6.
A common plant on rocks along the Atlantic Coast
to the north of New Jersey.

104b Not as above; vesicles free, individually sti-
pitate 105

Figure 139

105a Vesicles large, each bearing an expanded
blade. Fig. 140 Macrocystis

Fig. 140. Macrocystis pyrifera (Linnaeus) C. Agardh

A. Habit of a sporophyte plant growing in posi-
tion, X 0.02. B. A blade with its basal pneumato-
cyst, X 0.5. This species grows along our entire
Pacific Coast, forming great "kelp beds" which
in southern California are so richly developed that
commercial exploitation is carried out on a large
scale for the production of the valuable phyco-

colloid aigin and its derivatives. Harvesting is accomplished by cut-
ting the floating parts of the kelp a few feet below the surface with
a large mowing machine installed on a barge upon which the cut
kelp is piled for transport to the factory.

Algin is an amazingly versatile, hydrophilic colloid which has re-
cently found numerous uses in industry. Large quantities are used in
stabiHzing ice cream, chocolate milk, syrups, icings, puddings, sauces,
salad dressings, etc. As emulsifying, stabiHzing and suspending agents
algin products serve in the manufacture of a great variety of products
such as tooth paste, lotions, pharmaceutical jelly, film em.ulsions, textile
sizings, paints, boiler compounds, brazing pastes, polishes, insecticides,
oil well drilling muds, battery plate separators, etc.

One other species, M. integrifolia Bory, distinguished by a flat-
tening of the holdfast parts, is present from central California north-
ward.

108

HOW TO KNOW THE SEAWEEDS

Figure 140

109

HOW TO KNOW THE SEAWEEDS

105b Vesicles small, usually not bearing a blade. Fig. 141 Sargassum

Fig. 141. Sargassum iilipendula C.
Agardh

A small upper portion of a plant to
show the leaf-like vegetative blades
and the small, subspherical, stipitate
vesicles, one of them bearing an abor-
tive blade, X 0.64. This is the com-
mon, attached Sargassum of the At-
lantic Coast from Florida to Cape Cod.
The floating species of the Sargasso
Sea which are commonly encountered
in drift along the south Atlantic and
Gulf coasts originate through the
movement of the Gulf stream. These
are of two kinds, S. iluitans Bdrgesen,
and S. natans (Linnaeus) J. Meyen.

On the Pacific Coast Sargassum oc-
curs only in southernmost Cahfornia
where a small, densely branched spe-
cies, S. agardhianum Farlow, grows
on rocky mainland shores while S.
palmeri Grunow inhabits the warmer
waters of the Channel Islands.

Figure 141

106a Thallus flexible, either by joints or because of incomplete calci-
fication. Fig. 142 109

Fig. 142. Bossea sp.

A small part of a plant, X 5, to
show the calcified segments (intergeni-
cula) and the short, uncalcified joints
(genicula) which provide for flexibility
of the thallus. Southern Cahfornia.

Figure 142

110

HOW TO KNOW THE SEAWEEDS

106b Thallus inflexible, hard and stony throughout.. Fig. 143 107

Figure 143

Fig. 143. Lithothamnium giganteum L. R. Mason

An entire plant, X 1.2. This species from southern Cahfornia is
an example of a crustose coralline in which prominent excrescences
are produced and in which growth may proceed as the plant, having
originated on a loose pebble or piece of shell, is tossed about in the
surf or rolls along the sea floor. Numerous other species grow firmly
attached to rocks and may have such surface outgrowths or may be
only warty or entirely smooth. This range of characters is common
also to the genera Lithophyllum and Goniolithon in which generic dis-
tinctions are based upon internal anatomy and reproduction. Although
species of Lithophyllum and Lithothamnium may be found along either
the Atlantic or Pacific coasts, Goniolithon is as yet recorded from the
United States only in the warm waters of Florida.

Ill

HOW TO KNOW THE SEAWEEDS

107a Tetrasporangial conceptacles with many small pores formed by
the transformation of rows of cells into gelatinous plugs in the roof
of the conceptacles. Figs. 143, 144 Lithothamnium

Fig. 144. Lithothamnium sp.

Diagrammatic represen-
tation of a tetrasporangial
conceptacle to show the
several pores in the roof
and the form and position
of the zonate tetrasporan-
gia, X 40.

Figure 144

107b Tetrasporangial conceptacles opening by a single, relatively large
pore. Fig. 145 108

108a Tetrasporangia borne over whole floor of conceptacle

Goniolifhon

108b Tetrasporangia marginal within the conceptacles, the central area
of the floor occupied by paraphyses. Fig. 145 Lithophyllum

Fig. 145. Lithophyllum sp.

Diagrammatic represen-
tation of a tetrasporangial
conceptacle to show the
single large pore in the
roof and the marginal posi-
tion of the zonate tetraspo-
rangia with a group of
paraphyses occupying the
central area of the con-
ceptacle floor, X 40.

Figure 145

112

HOW TO KNOW THE SEAWEEDS

109a Thallus distinctly segmented 1 10

109b Thcdlus not segmented 1 17

110a Each growing apex bearing a tuft of branched filaments. Fig. 146.
CymopoUa barbaia

Fig. 146. Cymopolia barbata (Linnaeus) Lam-
ouroux

A small upper portion of a plant to show
the segmented character and terminal tufts
of hairs, X 2. A common plant of shallow
water in southern Florida.

Figure 146

1 10b Apices without tufts of filaments HI

Ilia Base of plant with a fibrous holdfast which penetrates sand or
mud. Fig. 147 Halimeda

Fig. 147. Halimeda discoidea De-
caisne

A small plant showing the calci-
fied segments separated by fibrous,
flexible joints, and the fibrous hold-
fast, X 0.75. This is one of several
species, all of cactus-Uke form, which
.may be encountered in southern
Florida.

Figure 147

113

HOW TO KNOW THE SEAWEEDS

111b Base of plant solid, calcified, without penetrating filaments. (See
remark under Fig. 148) 112

112a Segments more than twice as broad as thick. Fig. 148 113

Figure 148

Fig. 148. Bossea sp.

A small upper part of a plant to show the broad, winged inter-
genicula more than twice as broad as thick. Close inspection of a
plant of Bossea, or of one of the other articulated coralline genera
treated below through step 116, will show that as it grows intact on
its rock, or in the case of Jania, its host plant, it consists of two parts.
The erect, jointed parts are conspicuous, but there is also a thin,
crustose film spreading over the rock and adhering completely to it.
This basal crust cannot usually be removed with the specimen unless
a piece of the rock is taken.

112b Segments cylindrical to compressed, mostly less than twice as
broad as thick IM

114

HOW TO KNOW THE SEAWEEDS

113a Conceptacles both on margins and on flattened faces of segments.
Fig. 149 Calliaitbron

Fig. 149. Calliarthron cheilosporioides
Manza

A few segments of a plant to show
the location of conceptacles both on
the margins and on the flattened faces
of the segments near the margins, X
4.3. This is one of several species
which occur at low tide level or below
along the California coast.

Figure 149

113b Conceptacles restricted to flattened faces of segments. Fig. 142,
148, 150 Bossea

Fig. 150. Bossea sp.

A small upper part of a plant show-
ing the position of the conceptacles
exclusively on the flattened faces of
the intergenicula, X 3.6. Although
no species of Bossea are known from
th^ Atlantic coast, a number of them
may be found along the Pacific,
sometimes several in a single local-
ity. They are usually at low levels
on surfy shores, and attached to solid
substrates.

Figure 150

115

HOW TO KNOW THE SEAWEEDS

114a Plants with terminal conceptacles. Fig. 151 A 115

1 14b Plant without terminal conceptacles 116

1 15a Branching dichotomous. Fig. 151 /

ania

Fig. 151. Jania tenella Kiitzing

A. Two kinds of terminal concep-
tacles: antheridial on the left, tetra-
sporangial on the right, X 18. B. A
small upper part of a plant showing
the subcylindrical segments and the
dichotomous branching, X 18. This
is a delicate but common epiphyte
of our warmer waters along southern
California. This and a number of
other species are found along the
Atlantic Coast from North Carolina
southward, but /. capiUacea Harvey
will most commonly be found. It is
a very delicate, regularly dichotom-
ous plant which is usually entangled
and mixed with other algae rather
than in pure growths. Its branches
may be as little as 50 to 100 yu. in
diameter.

Figure 151

116

HOW TO KNOW 'THE SEAWEEDS
115b Branching pinnate. Fig. 152 Corallina

Fig. 152. Corallina officinalis Linnaeus

Part of an example of the large ro-
bust Pacific coast form (var. chilensis),
X 1. Various environmental forms of
this species may be encountered along
the whole Pacific Coast and from Long
Island northward through New Eng-
land. At least three other species
may be found along the Pacific of
which the smaller and more densely
branched C. vancouveriensis Yendo is
the most abundant and widespread.

Figure 152

116a Segments very short; intergenicular medulla unizonal. Fig. 153.
Lithothrix aspergillum

Lithothrix aspergillum J. E. Gray

A small portion of a plant bearing a single lateral
conceptacle and showing the very short, cylindrical seg-
ments (intergenicula) X 5. The unizonal intergenicular
medulla can be observed by decalcifying a small piece
and crushing it out carefully on a slide so as to make
the elongate medullary cells visible.

A common tufted plant 3 to 12 cm. high on rocks and
in tide pools along the entire Pacific Coast.

Figure 153

117

HOW TO KNOW THE SEAWEEDS

116b Segments not particularly short; intergenicular medulla multizonal.
Fig. 154 Amphiroa

Figure 154

Fig. 154. Amphiroa iragilissima (Linnaeus) Lamouroux

A portion of a loosely branched plant showing the elongated in-
tergenicula separated by conspicuous genicula, X 3. This is the most
widespread of our species, occurring from North Carolina to Florida.
At least two other species, one of them quite strongly flattened, may
be found in Florida. A. zonata Yendo is frequent in southern Cali-
fornia.

1 17a Thallus fan-shaped 118

1 17b Thallus not fan-shaped 119

118

HOW TO KNOW THE SEAWEEDS

118a Thallus composed of filaments (Fig. 155), moderately calcified.
Fig. 156 Udotea

Fig. 155. Udotea sp.

The lower part of a small, delicate,
exotic species in which the filamentous
structure is evident, X 21.

Figure 155

Figure 156. Udotea ilabellum (So-
lander) Howe

An entire plant, X 0.7, showing
the fan-like form, the concentric
lines of growth and the sand-
penetrating holdfast. This species
may be found in quiet waters
from North Carolina southward.
Other species are confined to
Florida within our territory.

Figure 156

119

HOW TO KNOW THE SEAWEEDS

118b Thallus composed of parenchymatous cells, lightly calcified su-
perficially, or sometimes apparently uncalcified. Fig. 157. .Padina

Fig. 157. Padina vickeisiae
Hoyt

A portion of a plant show-
ing the irregularly split blade,
the imroUed margins, the con-
centric hair Unes and some
rows of sporangia, X 0.65.
This is a very lightly calcified
species found from North Caro-
Hna to Florida and Texas. P.
sanctae-crucis Borgesen, which
is strongly calcified on the un-
der side occurs in southern
Florida.

Figure 1 57

119a Thallus consisting of a simple stalk bearing a disc at the top.
Fig. 158 Acetabularia

Fig. 158. Acetabularia crenulata Lamour-
oux

Upper part of a plant, X 3. This is a
common and highly attractive green alga
on broken coral in quiet water in southern
Florida and west to Texas. Even a rusty
old coffee can may be found wonderfully
glamorized by these beautiful little um-
brella-like plants. Two or three other, less
conspicuous species may be encountered
in Florida.

Figure 158

120

HOW TO KNOW THE SEAWEEDS

119b Not as in 119a.

120

120a Thallus under 2 cm. talL simple. Fig. 159. . .

Fig. 159. Neomeris annulaia Dickie

The upper portion of an actively growing
specimen, X 8. Although the individual plants
are small they often grow in large numbers on
bits of coral and shell along the Florida coast
where they are conspicuous because of the bright
green tips of the white, calcified plants.

tieomens annulata

m^^

120b Thallus larger, branched 121

WW

}^:-^m

?^:

•■^^

-i5<'>'

Figure 159

121a Thallus irregularly to dichotombusly branched 123

121b Thallus consisting of a simple stalk with a terminal tuft of
branches 122

121

HOW TO KNOW THE SEAWEEDS
122a Terminal tuft consisting of free filaments. Fig. 160 PeniciJlus

Fig. 160. PeniciUus capitatus Lam-
arck

An entire plant, X l.L showing
the terminal tuft of free filaments
which gives this calcified alga the
common name of Neptune's Shav-
ing Brush. The mass of rhizoids
which anchor the plant in sandy
and muddy places is evident. Oc-
curs in warm quiet water, Florida.

Figure 160

122

HOW TO KNOW THE SEAWEEDS

122b Terminal tuft consisting of filaments which are united, at least in
part, into small blades. Fig. 161 Rhipocephalus

Fig. 161. Rhipocephalus phoenix (So-
lander) Kiitzing

An entire plant, X 1.2.

There are only two species of
this interesting genus which is con-
fined to the West Indian region. Both
of them occur in southern Florida in
the same kinds of sandy habitats oc-
cupied by Penicillus and Udotea. R.
phoenix is the more abundant and
widespread of the two, and it is for
its recognition that the union of the
filaments of the terminal tuft into
small, narrow, flabellate blades is
pointed out in the key. In the other
species, R. oblongus, these filaments
are united only in youth, and older,
well developed specimens may rather
closely resemble Penicillus capitatus.
Inasmuch as all of these plants may
be found growing together, one
should attempt to make series of
specimens of all sizes and ages in
order, by comparison, to distinguish
them clearly. One will note that
small plants of R. oblongatus often
have funnel-shaped or markedly
elongate heads. Also, if one looks
closely for specimens showing the
partial or evanescent union of the
filaments of the head, he will have
found the distinguishing character of
the genus Rhipocephalus.

Figure 161

123

HOW TO KNOW THE SEAWEEDS

123a Thallus firm to soft, but not mucilaginous; cortex more compact
than the medulla and variously modified. Fig. 162. . . .Galaxaura

Fig. 162. Galaxaura oblongata (Solander) La-
mouroux
A small upper part of a plant, X 1.2. This

is one of several species found in the tropical
waters of Florida. Most of the species are cylin-
drical, but G. marginata (Solander) Lamour-
oux is flat. Most of the species show some
indication of banding, whether smooth Uke G.
oblongata or covered with assimilative fila-
ments (superficial hairs) Hke G. subverticillata
Kjellman.

Figure 162

123b Thallus soft, usually somewhat mucilaginous, at least in the vicin-
ity of branch tips; cortex formed of branched lateral fascicles of
branches from the medullary filaments. Fig. 163 Liagora

Fig. 163. Liagora ceranoides Lamouroux

A small upper part of a plant showing
the irregularly dichotomous branching habit,
X 1.3. This is one of several species which
may be found in the tropical waters of
Florida. Some of them become quite heav-
ily calcified so that lower parts are rigid,
although the tips may remain soft. The
genus is represented on our Pacific Coast
by a single species, G. californica Zeh,
which is common at Catalina Island, near
Los Angeles.

Figure 163

124

HOW TO KNOW THE SEAWEEDS

124a Main cell attached by several small rhizoidal cells at the base.
Fig. 164 Valonia ventricosa

Fig. 164. Valonia ventricosa J. Agardh

Habit of a small plant showing the basal
rhizoidal organs attached to a sand grain,
and two very young thalli attached to the
base, X 4. Common in some quiet water
habitats in southern Florida. This is a
famous plant on account of the size to
which a single cell may grow (to 3.5 cm.)
and the physiological experiments which
have been conducted upon it.

Figure 164

124b Main cell attached to crustose corallines by a penetrating peg.
Fig. 165 Halicystis ovalis

Fig. 165. Halicystis ovalis (Lyngbye) Areschoug

Habit of a plant showing the characteristic,
penetrating, basal peg, X 3.2. Epiphytic on
crustose corallines at lowest tide levels from
southern California northward.

Figure 165

125a Thallus with a midrib, median stipe, and (or) other veins. . . . 126

125b Thallus without a midrib, median stripe or veins 143

126a Thallus simple or branched only at the base 127

125

HOW TO KNOW THE SEAWEEDS
126b Thallus branched above the base 131

127a Blades with a single median stripe which may be up to 4 cm.
broad 128

127b Blades with more veins than a single midrib 129

128a Blade perforated. Fig. 166 Agarum cribrosum

Figure 166

Fig. 166. Agarum cnbrosum (Martens) Bory

The lower part of a small plant showing the holdfast, midrib, and
perforations of the blade, X 0.5. This is a cold water plant occurring
in northern New England and also in the Puget Sound region of our
north Pacific Coast. It is normally found in deep water, but dwarfed
examples may be encountered intertidally. Another species, A. fim-
briatum Harvey, with fewer and less conspicuous perforations and
flattened rather than cylindrical stipe occurs abundantly in the lower
Puget Sound and sparingly in deep water along the southern CaU-
fomia coast.

126

HOW TO KNOW THE SEAWEEDS
128b Blade not perforated. Fig. 167 Pleurophycus gardneTi

-(

/

Fig. 167. Pleurophycus gardneri Setchell &
Saunders

An entire plant to show the unbranched
habit, the broad, flat "midrib," and ruffled
margins of the blade, X 0.1.

Although this species is reported in the
literature from Yakutat Bay, Alaska to as far
south as the mouth of Coos Bay, Oregon, it
may well extend on down the coast to Cali-
fornia. Its wide separation from Laminaria
in this key, because of its prominent, broad
"midrib," or fold, is quite artificial, for it seem-
ingly is closely related to that genus. This
solitary member of the genus Pleurophycus
was discovered at the end of the last century
almost simultaneously by two different work-
ers, one at Whidbey Island, Washington, the
other at Yakutat Bay, Alaska. In Washing-
ton it was growing just below low water
mark in places much exposed to the fury of
the waves, while in Alaska it appeared
abundantly in drift.

PJeurophycus apparently comes into repro-
ductive condition only once and then dies.
The zoosporangial sori are borne in narrow
areas on both surfaces of the broad "midrib."

Figure 1 67

127

HOW TO KNOW THE SEAWEEDS

129a Thallus simple, or lobed and deeply divided or lacerated; hold-
fast not dichotomous 130

129b Thallus consisting of several strap-shaped blades from a dicho-
tomously branched holdfast. Fig. 168. .Dic/yoneurum californicum

Fig. 168. Dicfyoneurum californicum Ru-
precht

Basal part of a plant to show the
dichotomous holdfast and the reticulate
venation of the Ugulate blades, X 0.5.

Frequent on surfy rocks along the
Pacific Coast from central CaHfornia
northward.

Figure 168

130a Blades reddish, with a network of veins. Fig. 169

Polyneura laiissima

Fig. 169. Poiyneura latissima
(Harvey) Kvlin

A lower portion of a plant
showing the small holdfast, the
deeply divided, lobed blade
and the network of anastomos-
ing veins, X 0.6. This plant oc-
curs on rocks at low intertidal
levels and below along virtu-
ally the entire Pacific Coast. In
southern CaUfomia it is infra-
tidal and will be encountered
only in drift or by dredging.

Figure 1 69

128

HOW TO KNOW THE SEAWEEDS

130b Blades brownish, with five percurrent ribs. Fig. 170

Costaria costaia

Fig. 170. Costaiia costata (Tur-
ner) Saunders

The lower part of a relatively-
small plant showing the holdfast
of branched hapteres, the simple
stipe and the five prominent ribs
of the blade, three on one side
and two on the other, X 0.7. This
species is variable in size and
shape. It may reach a height of
two meters and a breadth of 30
cm., the blade being either ovate
or narrowly lanceolate. It may he
found on rocks, wood, or other
large algae in the lower inter-
tidal and upper infratidal regions
along the whole Pacific Coast
from the Bering Sea to southern
California. In the southernmost
part of the range, however, plants
are usually confined to moderate-
ly deep water. The mature blades
fruit from midsummer until late
in the fall, the sporangial sori
largely covering the bullate, or
blistered portions of the surface.

Figure 170

There has long been a difference of opinion among phychologists
as to the number of species of Costaria that should be recognized.
The members of the genus as they are now known are confined to the
North Pacific Ocean. Four species and one variety have been referred
to Costaria on our North American Coast from one time to another,
but Setchell and Gardner in their 1925 monograph concluded that only
one exceedingly variable species, namely, C. costata, is present in
this area. More recently the Japqtnese have reached the same con-
clusion for their plants on the western side of the North Pacific.

129

HOW TO KNOW THE SEAWEEDS

131a Thallus with a coarse, dichotomously branched stipe, but the
slender, ligulate blades simple. Fig. 171 . . . .Lessoniopsis littoTalis

Figure 171

Fig. 171. Lessoniopsis littoral-
is (Fallow & Setchell, ex Til-
den) Reinke

The lower part of a young
plant showing the coarse,
forked stipe and Hgulate
blades, one of them intact,
X 0.52. Grows on rocks at
low tide level subject to heavy
surf, from central CaUfomia
northward. The ligulate blades
with midribs are always ster-
ile. Small fertile blades (spo-
rophylls) without midribs de-
velop year after year in lat-
eral pairs below the Ugulate
blades. This species and Pos-
telsia palmaefoTmis are among
the most striking of our Pa-
cific cumatophytes, or "surf-
loving plants" for there ap-
pears to be no limit to the
amount of wave shock they
can withstand. Lessoniopsis
grows at somewhat lower
levels than Postelsia, appar-
ently having less resistance
to desiccation which may oc-
casionally be prolonged dur-
ing calm weather coincident
with low tides.

130

HOW TO KNOW THE SEAWEEDS

131b Thallus branched throughout, or at least above a simple stipe. . 132

132a Branching dichotomous to palmate or ilabellate 133

132b Branching pinnate to irregular 139

133a Blades with only a rather coarse midrib. 134

133b Blades with delicate, dichotomous and sometimes anastomosing
veins; midrib, ii present, not percurrent 136

134a Blades with a distinct, regular row of cryptostomata (showing as

small tufts of hairs) on either side of the midrib. Fig. 172

Hesperophycus harveyanus

Fig. 172. Hesperophycus harvey-
anus (Decaisne) Setchell & Gard-
ner

Part of a vegetative plant to
show the midrib and the rows
of cryptostomata on either side,
X 1.0. This is a common plant
on the exposed tops of upper in-
tertidal rocks along the coast of
California to as far north as Mon-
terey Bay. It is easily obtained
at almost any low tide, for it
grows only a few feet below high-
est water levels and is markedly
resistant to desiccation. In south-
ern California it is often mistaken
for a species of the closely re-
lated genus Fucus, but inasmuch
as Fucus is confined on our Pa-
cific Coast to the region north
of Point Conception, California,
Hesperophycus cannot be con-
fused with it to the south. A dis-
tictive and readily recognizable
character is the presence on most
plants of abundant, extruded para-

physes from the rows of cryptostomata. These are usually whitish in

color and quite conspicuous.

Figure 172

131

HOW TO KNOW THE SEAWEEDS
134b Blades without such rows of cryptostomata 135

135a Holdfast stupose (felted, fibrous). Fig. 173 Diciyopteris

Fig. 173. Diciyopteris polypodioi-
des (Desfontaine) Lamouroux

Two young blades shown aris-
ing from the spongy, felted (stu-
pose) holdfast. X 0.75. This spe-
cies is occasional along the At-
lantic Coast from North CaroHna
southward. In Florida three other
species may be encountered of
which D. justii is the most spec-
tacular, being up to 40 cm. high
and with blades from IV2 to 4
cm. broad. The other two species,
D. delicatula and D. plagiogram-
ma, are smaller and distinguished
by the irregular, tangled, dicho-
tomous branching of the former
and the irregular, alternate branch-
ing of the latter with small lateral
veins leading out toward the mar-
gins.

In southern CaUfornia another
species, D. zonarioides, is a com-
mon inhabitant of rocky tide pools,
especially those which are some-
what shehered and well insolated at low tide. In such habitats it may
be a luxuriant and dominant member of the vegetation which cannot
help but attract attention when sunUght brings out the irridescent
highlights of its fronds.

Figure 173

132

HOW TO KNOW THE SEAWEEDS

135b Holdfast solid, not stupose. Fig. 174 Fucus (in part)

Fig. 174. Fucus edentatus De
la Pylaie

A fertile plant of a small
form of the species from
central Oregon showing the
simple, solid holdfast and
the swollen reproductive
parts (receptacles) at the
ends of the blades, X 0.6.

The genus Fucus is one
of the most prevalent inter-
tidal algae in the cooler
waters of our coasts. From
central California northward
one or more species may be
found at almost any station,
while the same is true on
the Atlantic Coast to the
north of New Jersey. F. eden-
tatus occurs widely on both
coasts. Some species of Fu-
cus have inflated vesicles
and may be noted elsewhere
in this key (See Step 10.0a).

Figure 174 I^ is to this genus that

many of the so-called "rock
weeds" belong which are of
such economic importance
to the people of north At-
lantic shores. It is these plants which first furnished the burned ash
or "kelp" for the manufacture of soda used in glass and pottery mak-
ing in 17th century France. The value of such "rock weeds" as fer-
tilizer has been known and exploited for centuries, and in some areas
of western Europe they have been, importantly used for stock feed.

133

HOW TO KNOW THE SEAWEEDS

136a Ultimate thallus parts fan -shaped, usually with some concentric
hair lines. Fig. 175 Zonaria

Fig. 175. Zonaria failowii Setchell
<St Gardner

A small terminal part of a plant
to show the fan-shaped ultimate
thallus parts, the curved hair lines,
and several irregular patches of
aplanospores, X 2.7. This is a
common plant of intertidal pools
in southern Cahfomia. At least
two other species may be en-
countered abundantly in some
locahties from North Carolina to
Florida.

Figure 175

136b Not as above, the whole thallus often flobellate in outline, but
not the individual iiltimate ports; concentric lines absent 137

137a Tetrasporangiol sori occurring on any part of the blade. Fig. 176.
Hymenena

Fig. 176. Hymenena tlabelligeTa (J.
Agardh) KyHn

A small, upper portion of a fertile,
asexual plant showing the system
of delicate veins and a number of
elongate tetrasporangiol sori, X 1.
This is one of several species which
occur at lowest intertidal levels and
below along the Pacific Coast from
central CaUfornia to Puget Sound.

Figure 176

134

HOW TO KNOW THE SEAWEEDS

137b Tetrasporangial sori restricted to the margins of the blades and
(or) to proliferous outgrowths along the margins 138

138a Blades densely fringed with small, flat or ruffled, overlapping
marginal outgrowths to which the tetrasporangia are restricted.
Fig. 177 Botryoglossum iarlowianum

Fig. 177. Botryoglossum tarlowianum
(J. Agardh) G. DeToni

A small terminal portion of a blade
showing the system of delicate veins
and the development of the dense,
marginal fringe of small, overlapping
outgrowths, X 1. This is a frequent
species on lowest intertidal rocks or
below along the entire Pacific Coast
except in southernmost California
where the plant is found at moderate
infratidal depths. It is the only mem-
ber of the genus recognized in our
area, but, inasmuch as Botryoglossum
was founded upon a species from
South Africa, there is some question
about the true generic identity of the
Pacific American plants. Our plant
is clearly of very close relationship
with Cryptopleura, and separated
rather unconvincingly. Fortimately, it
can be recognized specifically by the characters of the marginal out-
growths mentioned in the key, and also by its large size (to 35 cm.
tall) and broad upper blade segments (to 2 cm.).

Figure 177

135

HOW TO KNOW THE SEAWEEDS

138b Blades not so densely fringed with outgrowths, or these at least

not densely crowded and strongly overlapping. Fig. 178

CryptopleuTa

Fig. 178. Cryptopleura violacea (J. Agardh)
KyUn

A small terminal portion of a fertile asexua.
plant showing the system of deHcate veins,
the scattered small marginal outgrowths, and
a number of linear, marginal tetrasporangial
sori as well as small elUptical ones in some
of the marginal outgrowths, X 0.9. This is the
most common and widespread member of this
Pacific genus, occurring along the entire coast.
About seven other species may be found more
or less locally along California shores.

Figure 178

136

HOW TO KNOW THE SEAWEEDS

I39a Thallus pinnately branched only from the primary axis, the blades
being simple 140

139b Thallus with several orders of branches 141

140a Lateral blades smaller and shorter than terminal blade and usu-
ally of different shape. Fig. 179 Alalia

Fig. 179. Alaria marginata Postals & Ru-
precht

An entire small plant with some of the
lower pinnate blades (sporophylls) re-
moved, X 0.12. This species of northern
California and southern Oregon is one of
several kinds which occur in the colder
waters of both coasts. The alarias reach
their richest development along the Alaska
Coast, but four species occur from central
California northward and five others on
the Atlantic shores of northern Massachu-
setts and Maine. An Alaskan species, A.
fistulosa is one of our most massive giant
kelps, reaching lengths of more than 75
feet.

Figure 179

137

HOW TO KNOW THE SEAWEEDS

Figure 180

138

HOW TO KNOW THE SEAWEEDS

140b Lateral and terminal blades of similar shape and usually of simi-
lar size. Fig. 180 PterygophoTa calHornica

Fig. 180. Pterygophora calif ornica Ruprecht

An entire small intertidal plant, X 0.25. Occurs along the entire
Pacific Coast, mostly in infratidal beds where the plants reach a large
size of 8 feet or more in length. Intertidal specimens are smaller, more
scattered, and are absent in the southern part of the range although
the plant may commonly be found in driftweed. This species is a
perennial. Each winter the sporophylls, of which as many as 12 to 18
may mature in a season, disintegrate to leave scars on the stipe.
Some plants studied in northern Washington were estimated to be
thirteen years old from counts of the number of scars on the stipe.

141a Thallus brownish; growth trichothallic. (This must be observed in
young, growing tips.) Fig. 181 Desmarestia (in part)

Fig. 181. Desmarestia munda Setchell
& Gardner

A small mid-portion of a plant show-
ing the very slender, opposite veins
and opposite branches characteristic
of the flat, ligulate members of this
genus, X 0.6.

Several species occur more or less
widely along the Pacific Coast. The
only flattened Atlantic species, D. acu-
leata (Linnaeus) Lamouroux, is very
narrow and alternately branched, oc-
curring north of New Jersey. Cylin-
drical species of Desmarestia are treat-
ed under step 24a of this key.

Figure 181

Species of this genus are exceed-
ingly acid in character (pH 1.0) and
will damage other algae placed in
contact with them in field collections.

139

HOW TO KNOW THE SEAWEEDS
141b Thallus reddish; growth not trichothallic 142

142a Thallus provided with frequent small, hook-shaped branches; mid-
rib absent; microscopic veins present. Fig. 182

Acrosorium uncinatum

Fig. 182. AcTOSorium uncinatum (Turner)
KyHn

Part of a plant bearing several of the
characteristic hooked branches, X 1.3. The
_,^y^ delicate veins, which must be seen with a

lens, are not indicated in the figure.

This is a common, epiphytic plant of
southern California.

Figure 182

142b Thallus without hook-shaped branches; midrib present, at least in
lower parts. Fig. 183 Nienburgia

Fig. 183. Nienburgia andersoniana (J. Agardh) Ky-
Hn

A small upper branch showing the midrib in
lower parts and the dentate margins of the blade,
X 1.2. Common at low intertidal levels, often in
grottos, under overhanging rocks, or under other
algae and surf-grass, from southern California to
Oregon. Another species, N. borealis Kylin, oc-
curs in Puget Sound.

Figure 183

140

HOW TO KNOW THE SEAWEEDS

143a Blade saucer-shaped, attached near the center to a short stipe.
Fig. 184 Constantinea

Figure 184

Fig. 184. Constantinea simplex Setchell

An entire small plant, X 1.1. This is one of the most peculiarly
shaped of our Pacific Coast red algae. It occurs at low tide level from
central California to Washington. Another species inhabits the Puget
Sound region of Washington.

143b Blade not saucer-shaped 144

144a Thallus consisting of a single sessile or stipitate, fan-shaped pri-
mary blade (sometimes 2 or 3) which may be simple, divided or
lacerate; color brown or greenish 145

144b Thallus simple or variously branched; if simple and broadly ex-
panded, at least not fan-shaped; if branched and dichotomous or
subdichotomous, any resulting fan-like form arises from the branch-
ing; color brownish, greenish or reddish 147

141

HOW TO KNOW THE SEAWEEDS

145a Thallus usually under 20 cm. tall, greenish, spongy. Fig. 185....
AvTainvillea

i--'^*)^\S;'ff'?i^^i^&k V;

im^^mmM

~c ■>.'.'. y-'.

'^'.-^^^-WM

■M^'

Figure 185

Fig. 185. Avrainvillea sp.

An entire plant to show the flabellate form of the spongy thallus,
X 1. Several species may be found in quiet, shallow water on sandy
or muddy bottoms in southern Florida. They are not particularly
abundant, nor are the dark, often silt covered blades attractive. The
spongy thallus is made up of branched, interlaced filaments which
provide certain diagnostic characters for distinguishing species.

145b Thallus large, usually over 20 cm. tall, coarse, brown, firm. . . . 146

142

HOW TO KNOW THE SEAWEEDS
146a Thallus sessile. Fig. 186 Hedophyllum

Figure 186

Fig. 186. Hedophyllum sessile (C. Agardh) Seichell

A plant of moderate size showing the sessile, irregularly divided,
fan-shaped blade, X 0.32.

This genus is represented by two species occurring along the
colder, northern portions of our Pacific Coast all the way to the Ber-
ing Sea. H. sessile extends as far south as central Cahfornia.

143

HOW TO KNOW THE SEAWEEDS

146b Thallus stipitate. Fig. 187 Latninaria (in part)

Figure 187

Fig. 187. Laminaria digitata (Linnaeus) Edmonson

The lower part of a plant showing the holdfast, stipe and deeply
divided or lacerated, fan-shaped blade, X 0.32.

Laminaria is a large genus of medium to small size kelps of which
some have narrow, ligulate blades and some, Uke L. digitata, have
broad, fan-shaped blades. The former will be encountered a Httle far-
ther along in this key. All of the species of Laminaria are character-
istic of cool to cold waters. On the central and northern parts of the
Pacific Coast they may be found in almost any rocky area, but in
southern California are confined to infratidal areas of cold, upwelling
water. On the Atlantic Coast they are largely confined to the cold
waters north of Cape Cod and are best developed at some depth
below low tide level. About fifteen species may be found in the United
States. (See other comments at step 150b.)

147a Plants essentially simple, consisting of one or more entire or lobed
blades: branching mainly restricted to basal region although some-
times the blades proliferous from the flattened surfaces (Caulerpa),
or from the margins (Gigartina: Grateloupia) 148

147b Plants branched in upper ports.

160

144

HOW TO KNOW THE SEAWEEDS

1 48a Plants with sand-penetrating rhizoids and erect blades from creep-
ing, stoloniierous parts. Fig. 188 Caulerpa proUfera

imr0^*^

Fig. 188. Caulerpa pTolifera (For-
skal) Lamouroux

Part of a plant to show the creep-
ing, stolon part with sand-penetrat-
ing rhizoids, and the flat, erect
blades with proliferous branches, X
0.6. Grows in quiet waters of south
and west Florida. Other species of
this genus of varied morphology are
treated elsewhere in this key.

Figure 188

148b Holdfasts simple and discoid, or of coarse hapteres, without pene-
trating rhizoids 149

149a Blades from a prominent stipe several centimeters long 150

149b Blades estipitate, or from a very short stipe 151

145

HOW TO KNOW THE SEAWEEDS

150a Thallus with a disc-shaped holdfast. Fig. 189

Phyllaria dermatodea

Fig. 189. Phyllana dermatodea (De la Pylaie) Le
Jolis

The lower part of a plant showing the simple,
discoid holdfast and the entire, Ugulate blade,
X 0.22.

Found on surfy rocks at lowest tide levels and
below, from northern Massachusetts northward.

The form of the blade is Hke that of several
species of Laminaria, especially some of the nar-
row Pacific Coast forms.

150b Thallus with a holdfast of branched hapteres
Laminaria (in part)

Except for the type of holdfast, which is like
that in Fig. 187, the several species of Laminaria
which key out here are of the Ugulate, non-flabel-
late form shown in Fig. 189 for Phyllana. Such
forms are represented on the Atlantic Coast by
Laminaria agardhii Kjellman (from New Jersey to
Cape Cod) and by L. faeroensis Borgesen (Maine).
Several Pacific species are of this narrow form,
at least in young stages, but one will encounter
on either coast a range of variation among the
species extending from the narrow, Ugulate blade
to the broadly cordate or flabellate and lacerate
blade of Fig. 187.

Figure 189

146

HOW TO KNOW THE SEAWEEDS

151a Surface and margins of blade covered with small, wart-like or
tooth-like papil. Fig. 190 Gigartma (in part)

Fig, 190. Gigartina harveyana
(Kiitzing) Setchell & Gardner

Figure 190

A maturing cystocarpic plant,
X 0.8. This is a common one of
several simple, flat, ligulate to
broadly complanate species of this
genus on the Pacific Coast. It oc-
curs in California and Oregon.
One or more species of this gen-
eral form may be expected to oc-
cur at low levels on most any ex-
posed, rocky shore along the Pa-
cific. Many of the best specimens
may be found in drift where their
large, conspicuous, reddish blades
are sure to attract attention. The
characteristic wart-like outgrowths
on the blade surfaces provide for
an easy means of identification so
that the student of Pacific sea-
weeds quickly becomes familiar
with the broad forms of this genus.
There are other members of Gigar-
tina, however, of very different
form, and it is these smaller, much
branched subcyhndrical or com-
pressed species which usually puz-
zle the beginner. Some important
examples of these other forms of
Gigartina are treated under steps
168a and 187a.

147

HOW TO KNOW THE SEAWEEDS

151b Surface of blades smooth.

152

152a Thallus dark brown or yellowish-brown (as opposed to reddish,
purplish or greenish) 153

152b Thallus reddish, purplish, or sometimes greenish, but not brown
or yellowish-brown 154

153a Thallus several layers of cells thick, the medullary cells very dif-
ferent, especially in size, from the surface cells. Fig. 191

Ilea (Petalonia) fascia

Figure 191

Fig. 191. Ilea fascia (MUller) Fries

Part of a transection of a blade showing the difference in size be-
tween the medullary cells and the surface cells. The vertical rows of
small cells represent gametangia, X 150.

This is a common species along practically the entire Pacific and
Atlantic coasts. Its gross appearance is essentially like that shown for
Punctaiia in Fig. 193, but its structure is quite distinct from that genus.
In southern California it may be confused with Endarachne binghamiae
J. Agardh which is almost identical in external appearance. Again,
however, a transection readily distinguishes the two, for Endarachne
has a medulla of intertwined filaments.

148

HOW TO KNOW THE SEAWEEDS

153b Thallus thin, oi few cell layers, the surface cells little different
from those of the inner layers. Fig. 192, 193 Punctaria

&

O^QQQQ!

Fig. 192. Punctaria sp.

Part of a transection of a blade
showing the relatively uniform cell
structure compared to Ilea, X 125. A
gametangium and two (?) sporangia
are shown.

Figure 192

Fig. 193. Punctaria plantaginea (Roth) Greville

An entire young plant, X 0.5. This species,
and the somewhat more slender and delicate
P. latiiolia Greville, occur on stones or on algae
and Zosfera from New Jersey northward. On
the Pacific Coast four species occur between
central California and Puget Sound, Washing-
ton, but they are all of infrequent or geo-
graphically restricted occurrence.

Figure 193

149

HOW TO KNOW THE SEAWEEDS

154a Blades with proliferations from the margins. Fig. 194

Grateloupia (in part)

Fig. 194. Grateloupia schizophylla Kiitzing

A single blade of a young plant, X 0.48.
This is a common species along the entire
Pacific Coast, but its blades may be either
entire or proliferous, so that it may key out
under step 158a. Plants may reach a length
of three feet or more.

The genus contains species of varied sire
and morphology, some of local distribution and
some of very wide distribution. Abundantly
branched species Hke G. {ilicina key out at
step 188b, while broad, simple forms Hke G.
maxima key out at step 158a.

Figure 194

154b Blades without proliferations from the margins 155

155a Cortex with gland cells: Fig. 195 Schizymenia paciiica

Fig. 195. Schizymenia paciiica (Kylin) Ky-

Un

Part of a transection of a blade to show
the gland cells of the cortex and the slen-
der, interlaced filaments of the medulla,
X 224. This species is a frequent, broad,
membranous red alga along the entire
Pacific Coast. Its simple, or lobed, short-
stipitate blades do not show any external
characters satisfactory to distinguish the
plant from other similar membranous al-
gae such as Halymenia, Cryptonemia, Grjr-
teloupia, Rhodoglossum, etc., and it will be
found most practical to use the presence
of the usually conspicuous large gland
cells foj its recognition.

Figure 195

150

HOW TO KNOW THE SEAWEEDS

155b Cortex without gland cells 156

156a Transection showing many of the medullary filaments running
from cortex to cortex and more or less perpendicular to the sur-
face of the blade. Figs. 196, 197 Halymenia

r<n^A n^DQoDo 80Oo

Fig. 196. Halymenia sp.

Part of a transection of a tetrasporangial-
blade showing the medullary filaments
running from cortex to cortex, X 250.

Figure 196

Fig. 197. Halymenia gelin-
aria Collins & Howe

Habit of a small plant, X
0.5. This is one of several
species which occur in infra-
tidal waters from North Car-
olina to Florida and which
are quite often encountered
in beach drift. All are broad,
rather thin plants of slippery
texture. One or more spe-
cies may also be found in
drift along the California
coast. Of these, H. californi-
ca Smith & Hollenberg may
be recognized by its cross
section and broadly falcate
(sickle-shaped) blades.

Figure 197

156b Transection showing few or no medullary filaments running from
cortex to cortex and perpendicular to the blade surface 157

151

HOW TO KNOW THE SEAWEEDS

157a Tetrasporangia borne individually in the cortical tissue of the
blade, not touching each other or occurring in masses. Fig. 198. .
158

Fig. 198. Cryptonemia obovata J. Agardh

Part of a transection of a tetrasporic
blade showing an individual tetrasporon-
gium in the cortex, X 520. One of the
characteristic medullary filaments with
highly refractive contents is shown in
cross section.

Figure 198

157b Tetrasporangia borne in masses embedded deeply in the blade.
Fig. 199 159

Fig. 199. Iridophycus sp.

Part of a transection of a young tetra-
sporic blade to show the origin of the
sporangia (undivided) among the medul-
lary filaments well inside of the cortex
(Modified after Kylin).

^^'^^(J

4B ^ Ag^ "^

cPO ^

O Q^

p^^:g

Figure 199

158a Cortex composed of small cells arranged more or less clearly in
anticlinal rows; medulla without refractive filaments. Fig. 200. . .

Grateloupia (in part)

Fig. 200. Grateloupia maxi-
ma (Gardner) KyUn

Transection of a blade
through a cystocarp show-
ing cortical cell rows, espe-
cially on lower surface. X
200.

This is one of the broad
species with entire blades
which may be found along
the Cahfornia coast. Non-
prohferous sp6cimens of G.
schizophylla key out here (see Fig. 194). Such broad, membranous
species of Grateloupia do not occur along the Atlantic Coast

Figure 200

152

HOW TO KNOW THE SEAWEEDS

158b Cortex composed of cells usually showing little or no arrange-
ment in anticlinal rows; medulla with refractive filaments. Figs.
198, 201 Cryptonemia

Fig. 201. Cryptonemia obovata
J. Agardh

Habit of a young plant, X 0.36.
This is one of two species which
may be encountered frequently in
beach drift along the Pacific
Coast. Unhke Grateloupia or
Halymenia, the blades are not
sHppery in texture, but rather
firm and crisp. The blades are
reduced at the base to a very
slender, short stipe.

Figure 201

159a Tetrasporangia developing between the medullary filaments. Figs.
199, 202 hidophycus

Fig. 202. Ihdophycus ilacci-
dum Setchell & Gardner

Habit of a young plant,
X 0.32. This is a common
species of a genus of sever-
al species occurring from
central California northward.
hidophycus grows mostly at
low intertidal levels, and
sometimes in great abund-
ance. /. flaccidum and at
least one other species have
been harvested commercial-
ly in Oregon and northern
California for the production
of the phycocolloid Iridophy-
cin used in stabilizing choco-
late milk. As much as 400

Figure 202

pounds have been collected by one man at a single low tide.

153

HOW TO KNOW THE SEAWEEDS

159b Tetrasporangia developing from the innermost cortical cells. Fig.
203 Rhodoglossum (in part)

Fig. 203. Rhodoglossum sp.

Part of a transection of a tetrasporic
blade to show the origin of the tetraspor-
angia (undivided) from the inner corti-
cal cells (redrawn from Kylin).

Several species of Rhodoglossum oc-
cur along the Pacific coast which are
similar in habit to species of Iridophycus
(See Fig. 202). These unbranched forms
with entire blades will be somewhat dif-
Figure 203 ficult for the Student to recognize until

some experience is gained with them.
There are only four species, however, all confined to California except
one from Puget Sound. They usually will be less abundant than the
species of Iridophycus, and, apart from the tetrasporangial character
pointed out above, they may be distinguished in another way. Iridophy-
cus plants after drying will ordinarily disintegrate when soaked up in
fresh water, while specimens of Rhodoglossum will not respond in this
way.

Note that our commonest species of Rhodoglossum, R. affine, is
dichotomously branched and appears at step 170b in the key.

160a Erect blades pectinately branched from a creeping stolon with
sand-penetrating rhizoids. Fig. 204 Caulerpa crassifoUa

Fig. 204. Caulerpa crassifoUa (C.
Agardh) J. Agardh

A portion of a plant to show the
erect, pectinate, flattened blades and
sand-penetrating rhizoids from the
creeping stolon, X 0.7. This common
species of Florida keys out apart from
other species of the genus because of
the flattened character of the branched,
erect parts. Other species will be noted
under steps 59a and 148a.

'XTC^

Figure 204

154

HOW TO KNOW THE SEAWEEDS

160b Not as above; without sand-penetrating rhizoids from a stoloni-
f erous base , 161

161a Ligulate blades borne in a drooping bunch from the apex of a
stiffly erect, heavy stipe 162

161b Not as above; blades not borne in a drooping bunch 163

162a Apex of stipe strongly forked. Fig. 205 Eisenia arborea

Fig. 205. Eisenia arborea
Areschoug

A. A young plant show-
ing the beginning of ero-
sion of the apex of the
primary blade and the de-
velopment of the lateral
blades from the meriste-
matic area at the base of
the primary blade, X
0.32.

B. The lower part of an
older plant showing how
the stipe has elongated
and increased in thick-
ness while the primary
blade has eroded away
completely to its base to
produce an artificial fork-
ing at which the lateral
blades arise on either
side of the base of the
old primary blade, X
0.32.

This is a common plant
of low intertidal levels
and below on rocky
shores of southern Cali-
fornia. It is sometimes mistaken for Postelsia because of its habit, but
the ranges of these two plants do not overlap. Eisenia is one of the
principal components of the "submarine gardens" of Catahna Island,
California.

Figure 205

155

HOW TO KNOW THE SEAWEEDS
162b Apex of stipe not forked. Fig. 206 Postelsia palmaeioTinis

it-."

Figure 206

Fig. 206. Postelsia palmaeformis Ruprecht

Habit of a group of plants from a "grove," X 0.25. This plant
may commonly be observed on the Pacific Coast from central CaU-
fomia to Vancouver Island, B. C, but its habitat is such as to make
collection of specimens difficult. The "groves" occur on rocks at low
intertidal levels in places which are subjected to the full force of the
heaviest surf. Many of them are completely inaccessible on outlying
rocky ledges, but others may be reached at times of lowest tides in
calm weather. The heavy, elastic stipes are exceedingly well adapted
to the pounding surf conditions of Postelsia's habitat.

156

HOW TO KNOW THE SEAWEEDS

163a Thallus branched in the manner of an Opuntia cactus, the blades
or branches all more or less circular or elliptical in outline. Fig.
207 Opuntiella calUomica

Figure 207

Fig. 207. Opuntiella californica (Fallow) Kylin .

Habit of an entire plant, X 0.28. Grows on rocks at lowest tide
levels and below from central California northward, but usually as
isolated thalli. It is more frequently found in beach drift. It should be
pointed out that juvenile or poorly developed plants of this species will
be difficult to recognize, for the distinctive cactoid form will not neces-
sarily be evident.

163b Not as above; blades or branches not at all circular in shape. . 164

164a Primary branching of thallus dichotomous or subdichotomous, or
subpalmate to produce a flabellate form at least in upper parts. 165

164b Primary branching essentially in one plane, but not dichotomous,
subdichotomous or subpalmate. (But note dichotomous tendency
in Fig. 224) 178

157

HOW TO KNOW THE SEAWEEDS

165a Terminal portions of fertile dichotomies swollen and broader than
region below. Fig. 208 166

Figure 208

Fig, 208. Pelvetiopsis limitata (Setchell) Gardner

Habit of part of a plant, X 0.7, showing the swollen ends of the
branches (receptacles) containing the small, simken, fertile cavities
(conceptacles). This is a common species of middle and high inter-
tidal rocks from central CaHfornia northward.

Pelvetia fastigiata (J. Agardh) De Toni, which is similar in habit
and habitat, but much taller, occurs commonly along the entire Cali-
fornia coast to southern Oregon. In southern California it is the only
such olive-green, ribless species with swollen branch apices on the
high intertidal rocks.

165b Terminal portions of fertile dichotomies about the same width as
lower parts, or, if broader, at least not swollen 167

166a Thalli short, 4-15 cm. tall; macrosporangia (oogonia) with only
one fimctional spore. (See Figs. 208, 209A). . .Pelvetiopsis limitata

158

HOW TO KNOW THE SEAWEEDS

Pjgure 209

166b Thalli larger, 15-40 cm. tall; macrosporangla (oogonia) with two
functional spores. Fig. 209B Pelvetia iastigiata

Fig. 209.

Macrosporangia of two closely re-
lated genera: A, Pelvetiopsis, and B,
Pelvetia. These are shown removed
from the inner wall of the conceptacle
in which each was produced. In the
case of Pelvetiopsis a single functional
spore is seen, the remaining nuclei
from the divisions of the macrospor-
angium being separated off in a non-
functional mass below. In Pelvetia
two functional spores are seen with
the extruded nuclei between. Various stages in the development of
these macrospores as well as the microspores (antherozoids) may be
observed by cutting transections of receptacles bearing maturing con-
ceptacles.

See note regarding Pelvetia under Fig. 208.
167a Medulla composed mainly or entirely of large, parenchymatous
cells 171

167b Medulla not composed of large parenchymatous cells, but of
densely or loosely packed ramified filaments, mostly longitudi-
nally arranged 1^^

168a Flat surface of branches provided with small, wart-like or spine-
like papillae. Fig. 210 Gigartina (in part)

Fig. 210. Gigartina stellata Bat-
ters

An entire, maturing plant, X 1.
This species from the Atlantic
Coast, occurring from Rhode Is-
land northward, is illustrated as
an example of a rather diversified
group of Gigartina species which
. will best key out here. These are
all flattened, more or less clearly
dichotomously branched forms
bearing papillose or spinose out-
growths from the flattened sur-
faces of the broader blade parts.
About half a dozen Pacific Coast
species fall within this assem-
blage, of which G. cristata (Set-

Figure 210

159

HOW TO KNOW THE SEAWEEDS

chell) Setchell & Gardner is probably the most widespread. Smith's
(1944) illustrations of several California species are helpful to students
in learning to recognize these polymorphic gigartinas. The only avail-
able monographic treatment is Setchell and Gardner 1933, (Univ. Calif.
Publ. Bot. 17 (10):255-340) which contains numerous photographs.

Other species of this genus are treated in this key under steps
151a and 235a.

168b Flat surfaces of branches smooth,

169

169a Thallus normally with determinate secondary pinnate branches

from the primary dichotomous branches. Fig. 211

Zanardinula (in part)

Fig. 211. Zanardinula cornea (Okamura)
Dawson

A small upper portion of a plani aboui
20 cm. high to show the dichotomous
primary branching and determinate sec-
ondary pinnate branchlets, X 1.1. This is
a Pacific Coast genus of which one or
more of our half dozen species may be
found at almost any rocky intertidal sta-
tion from southern California to Washing-
ton. Z. cornea, found from central Oregon
southward, is one of three species which
will key out here because of the dicho-
tomous primary branching. The others will
not give the impression of being dicho-
tomous and will key out under step 188a.

Figure 21 1

169b Thallus normally without determinate secondary pinnate branches
170

160

HOW TO KNOW THE SEAWEEDS
170a Species of Atlantic Coast occurrence. Fig. 212. .Chondrus crispus

Fig. 212. Chondrus ciispus
(Linnaeus) Stackhouse

A portion of a plant re-
moved from a clump, X 0.8.
Although this species may not
readily be distinguished from
the Pacific Rhodoglossum af-
fine except through the study
of certain reproductive details,
the two need not be confused,
for their ranges on opposite
coasts do not overlap. C. cris-
pus occurs from New Jersey
northward and is the famous
Irish Moss which has been
collected commercially for over a century, especially around Scituate,
Massachusetts. It is the source of a phycocolloid called carrageenin
which is widely used as a stabihzer in chocolate milk, salad dressings,
tooth paste, lotions, syrups, etc. About a milUon pounds are produced
in a year.

Figure 212

170b Species of Pacific Coast occurrence. Fig. 213

Hhodogiossum affine

Figure 21 3

Fig. 213.
KyUn

Rhodoglossum afiine (Harvey)

A portion of a plant removed from
a clump, X 0.8. This is the only dicho-
tomous member of Rhodoglossum in
our territory. It is widespread along
the coast from central Oregon south-
ward. In central and southern Cah-
fornixt it is often dominant in some in-
tertidal, rocky shore areas. It is ex-
ceedingly variable in width of thallus
parts, in color, and in branch shape, so
that many specimens which may be
found will not appear to agree with the
illustration. The more or less clearly evident dichotomous branching,
the filamentous structure and smooth surfaces of the segments will dis-
tinguish it.

161

HOW TO KNOW THE SEAWEEDS

171a Medulla of middle parts of blades composed of a single, uniform
layer of large cells. Fig. 214 172

171b Medulla composed throughout of more than one layer of large
cells, or at least the medullary cells not uniform 173

172a Blades with both medulla and cortex monostromatic throughout.
Fig, 214 Dictyota

Fig. 214. Dictyota sp.

Transection of the margin of a
blade showing the monostromatic
cortex and monostromatic medul-
Figure 214 la. In the genus Pachydictyon

(Fig. 215) the medulla is distro-
matic at the margins and the cortex of two or more layers.

Dictyota is a warm water genus represented by one common spe-
cies, D. flabellata (Collins) Setchell & Gardner, in southern California,
and by several species in Florida. D. dichotoma (Hudson) Lamouroux,
which extends from North CaroHna southward, may be considered
the commonest Atlantic species. Although some of the species are
quite broad and resemble the figure of Pachydictyon (Fig. 215), others
are narrow and only 1 to 2 mm. broad. Altogether, about nine species
are known from our coasts.

172b Blades with distromatic medulla at the margins and di-polystro-
matic cortex at the margins. Fig. 215 Pachydictyon coriaceum

Fig. 215. Pachydictyon coriace-
um (Holmes) Okamura

The upper portion of a plant
to show the branching habit,
X 0.56. This is the only mem-
ber of this genus in our terri-
tory. It is common in southern
Cahfornia and is readily dis-
tinguished externally from the
similar Dictyota flabellata by
its coarser texture and usually
darker color.

Figure 215

162

HOW TO KNOW THE SEAWEEDS

173a Mediilla with small cells between the large ones. Fig. 216, 217.

Callophyllis

Fig. 216. Callophyllis sp.

Part of a transection of a blade
to show the structure of the medul-
la in which large and small cells
are intermixed.

Figure 216

Fig. 217. Callophyllis
marginihucta Setchell
& Swezy

A small upper portion
of a cystocarpic plant
to show the flabellate
branching habit and the
marginal cystocarps, X
1. This species, occur-
ring from central Ore-
gon to southern Cah-
fornia, is a member of
a common genus on our
Pacific Coast of which
seventeen species may
be collected in drift or
at low intertidal levels.
They are of moderate
size, up to 30 cm., and
vary widely within the
general pattern of dich-
otomo - flabellate form.
Most of them are bright reddish in color and may be made into some
of the most striking and attractive herbarium specimens. In most spe-
cies the cystocarps are not marginal, but are scattered over the flat
faces of the blades. Until recently it was virtually impossible for the
layman to identify the many species of Callophyllis, but now the writer
has published a series of illustrations of all of the Pacific Coast species
with which the student may quite readily identify many of his speci-
mens by the process of matching. (Marine Red Algae of Pacific Mexico.
A. Hancock Pacific Expeditions 17: 1-397. 1953-54.)

Figure 217

163

HOW TO KNOW THE SEAWEEDS

173b Medulla composed only of large, parenchymatous cells 174

174a Cortex of 2 to 3 tiers of small cells, not in vertical (anticlinal) rows
except sometimes in tetrasporangial sori. Fig. 218 175

Fig. 218. Rhodymenia sp.

Part of a transection of a blade

Figure 218

^(^ to show the way in which the cor-
tical cells do not present an ar-
rangement in anticlinal rows.

174b Cortex of more than 3 tiers of small cells arranged in anticlinal
rows. (This may be true in Phyllophora, step 177b only in older,
thicker parts of blades where secondary growth of the cortex oc-
curs.) 177

175a Cystocarps embedded in the medulla, arranged so as to form a

linear sorus resembling an interrupted midrib. Fig. 219

Stenogramme mterrupta

Fig. 219. Stenogramme inter-
rupta (C. Agardh) Montagne

An upper portion of a female
plant showing the appearance
of the cystocarps in linear sori,
X 0.8. Tetrasporic plants have
the sporangia in small, irregu-
larly shaped, nemathecial sori
scattered over the flat faces of
the blades. This is the only spe-
cies of the genus on our coasts.
It may be encountered in drift
or at low intertidal levels along
the entire Pacific shore.

Figure 219

164

HOW TO KNOW THE SEAWEEDS

175b Cystocarps protruding above the surface of the blade. Fig. 220.
176

Figure 220

Fig. 220. Rhodymenia sp.

A vertical section through a mature cystocarp to show its pro-
truding, dome-Uke, non-coronate form. The carpospores are produced
from a pedicellate gonimoblast. The ostiolar aperture is shown in
the top of the pericarp.

Rhodymenia is a world wide genus of some three score species,
mostly red in color and found in lower intertidal or in infratidal habi-
tats. The cystocarps are very uriiform in structure, and, although
infrequently found in some species, are of great aid in identifying
the genus. Specific characters are mostly found in the vegetative
thallus and in the manner iii which the asexual reproductive spores
(tetraspores) are produced. The genus is much more richly developed
along the Pacific than the Atlantic Coast. Most of the North Ameri-
can species are illustrated in the writer's "Review of the genus Rhody-
menia with descriptions of new species." (A. Hancock Pacific Expedi-
tions 3:123-181. 1941.)

165

HOW TO KNOW THE SEAWEEDS

176a Cystocarps coronate (Fig. 221 A); blades subdichotomous and of

more or less irregular palmate-ilabellate outline. Fig. 221

Fauchea

Fig. 221. Fauchea laciniata
Agardh

J.

A. A single coronate cystocarp,
X 12. B. A small, upper portion
of a large (15 cm.) cystocarpic plant
with relatively narrow blade-seg-
ments, X 0.8. This species may be
encountered frequently at lowest
intertidal levels in central and
southern California. Plants are of-
ten only 5 to 6 cm. wide or high
and broadly flabellate. We have
only one other species, F. fryeana
Setchell, in infratidal waters of
Puget Sound.

Figure 221

I76b Cystocarps not coronate (See Fig. 220); blades subsimple to sub-
dichotomous or regularly dichotomous. Figs. 218, 222 . Hhodymenia

Fig. 222. Rhodymenia pad-
iica Kylin

Part of a plant showing
dichotomous branching and
the production of stolons at
the base, X 0.72. This spe-
cies and several others of
dichotomous form and simi-
lar habit occur frequently
along the coast of California
and southern Oregon. In ad-
dition to these there are sev-
eral species with relatively
broad blades and somewhat
simpler branching habit. R.
palmata (Linnaeus) Greville is
a broad-bladed plant which is
subsimple below and dichotomous or palmately divided above. It oc-
curs along the New England coast as well as in the Puget Sound
region of Washington. This is the food-seaweed known as "dulse"

Figure 222

166

HOW TO KNOW THE SEAWEEDS

which is commercially employed as a thickener in soups, sauces, etc.,
and is eaten in the raw state or after drying as a salad or vegetable
relish.

Our most attractive Rhodymenia is R. pertusa (Postels & Ruprecht)
J. Agardh which occurs from central Oregon northward. It is broad,
usually simple, and has many perforations in the blade.

Rhodymenia may often be found without cystocarps, especially
the smaller, dichotomous forms occurring intertidally. They have a
coarser, more rigid texture than Fauchea, however, and lack the very
broadly flabellate form.

177a Thallus more or less regularly dichotomous. Fig. 223

Gymnogongrus (in part)

Figure 223

Fig. 223. Gymnogongrus line-
aris (Turner) J. Agardh

An upper portion of a ma-
ture plant to show the regu-
lar dichotomous branching, X
0.68. This species occurs from
central California to central
Oregon and is an example of
the coarse, broad forms of the
genus, of which G. platyphyl-
lus Gardner is another occur-
ring in CaUfornia, and G. nor-
vegicus (Gunner) J. Agardh in
New England. Beside the slen-
der, cylindrical G. griffithsiae
treated under step 22a, G. lep-
tophyllus J. Agardh is the only
slender, narrow species of our
territory. It is common along
California and Oregon.

167

HOW TO KNOW THE SEAWEEDS

177b Thalliis irregularly dichotomous or palmate, commonly prolifer-
ous. Fig. 224 Phyllophora m

Figure 224

Fig. 224. Portions of Fhyllophoia species: A, P. membranifolia (Good-
enough & Woodward) J. Agardh; B, P. brodiaei (Turner) J. Agardh,
both X 1.

These are the two common species of Phyllophora of our north-
eastern coast. Both are characteristic of fairly deep water, usually
well below tidal range, but the former comes into lowest tide pools.
Both may be found cast up in drift. They are exceedingly variable in
form, often highly irregular and proliferous from old, eroded or dam-
aged blades. Three species occur on the Cahfornia coast, but all are
relatively scarce, deep water forms which will not often be encountered
except in the dredge or at the hand of a deep diver. The recent rise
of the sport of aqua-lunging has, however, brought these plants to
some notice, for off Scripps Institution of Oceanography at La JoUa,
California where aqua-lung training is conducted, the regularly dicho-
tomous, broad-segmented Phyllophora clevelandii is one of the few
conspicuous algae encountered in the dim depths below 100 feet.

168

HOW TO KNOW 'THE SEAWEEDS

178a Branching opposite, but the two branches of each opposite pair

not alike. Fig. 225 Plumana

(also known in the literature under the name Ptilota)

Figure 225

Fig. 225. Plumana filicina (Fallow) Doty

A single primary lateral . branch showing the opposite pairs of
ultimate branchlets and their dissimilarity, X 5. This is one of the
commoner of seven species of this genus which may be encountered
along the Pacific Coast. Although more characteristic of the northern
parts of the coast, three of them extend southward through southern
Cahfornia. Two other species inhabit Atlantic shores from New Jersey
northward, namely P. pectinata (Gunner) Ruprecht and P. sericea (Har-
vey) Ruprecht.

The dissimilarity of ultimate branchlets should be observed in
young parts where the contrasts are usually more pronounced.

Specific characters are to be found in the nature of the margins
of the ultimate branchlets and in the curvature and length of these
branchlets. Thus, in P. filicina the branchlets are serrate on both mar-
gins, while in P. densa they are serrate only on one. Both P. californica
and P. hypnoides have smooth margined ultimate branchlets, but in the
former they curve upward toward the branch apex while in the latter
they do not. All of these four species are common in CaHfornia.

178b Branching alternate or irregular, or if opposite, the branches of
opposite pairs essentially alike 179

169

HOW TO KNOW THE SEAWEEDS

179a Ultimate flattened branches, especially of fertile plants, arranged
in clusters or fascicles along the major axes which are more or
less cylindrical. Fig. 226 Odonthalia

Figure 226

Fig. 226. Odonthalia Uoccosa (Esper) Falkenberg

A small part of a mature plant to show the fasciculate arrange-
ment of the ultimate, short, flattened, acute branchlets, X 1. This is
the most widespread of our species of this genus. It ranges from cen-
tral California northward. In the Puget Sound area of Washington
several other local or far northern species occur. They, however, are
more flattened, lack the fasciculate arrangement of the branches and
are regularly, alternately, distichously branched Some of them show
a more or less distinct development of a midrib.

On the Atlantic coast the odonthaUas occur north of Maine and
outside the scope of this book.

The student should note that this plant is keyed out here under
the flattened species on account of the flatness of the ultimate, acute
branchlets. but the often cylindrical character of the axes may at times
cause one to attempt to key it out among the cyUndrical ones in the
vicinity of step 33.

179b Ultimate branches not arranged in clusters,

180

180a Growth by means of a single apical cell

181

180b Growth apical from a many-celled meristem, not from a single
apical cell ^^^

170

HOW TO KNOW THE SEAWEEDS

181a Branches each with an apical pit (See Figs. 18C; 56) in which the
growing point is situated. Fig. 227 Laurencia (in part)

Figure- 227

Fig. 227. Two examples of flattened species of Laurencia: A, L. diego-
ensis Dawson, B, L. splendens Hollenberg, both occurring in south-
ern California, X 0.75.

Perhaps the commonest of the flattened laurencias within our ter-
ritory is L. spectabilis Postels & Ruprecht which is similar to L. diego-
ensis, reaches a height of 20 cm. or more, and occurs from central Cali-
fornia northward. No flattened species of this genus seem to occur
commonly along any part of the Atlantic coast, although cyHndrical
species may be found. See step 37b.

1811? Branches without an apical pit, although in Gelidium sometimes
the apex is somewhat indented 182

171

HOW TO KNOW THE SEAWEEDS

182a Branching sympodial, the branches of each order unilateral and
pectinate. Fig. 228 Plocamium

Fig. 228. Plocamium pacificum
KyUn

A portion of a plant, X 1.
This is a common and very at-
tractive, delicate red alga along
the Pacific Coast. Throughout
its range it is often accom-
panied by a smaller and more
purplish colored species, P. vio-
iaceum Farlow, which, however
does not at all compare in the
frequency with which it will be
noticed by either the casual ob-
server or the professional col-
lector. So handsome and of
such interesting geometric form
is Plocamium. that one finds
himself making extra speci-
mens simply for their esthetic
value. Indeed, it has been em-
ployed in the making of attrac-
tive, decorative greeting cards.

Although P. pacificum is oc-
Figure 228 cosionolly epiphytic, it is usu-

ally foimd massed on rocks at
low tide level and below, con-
spicuous by its rich rose-red
color, and often of moderate size, 10-25 cm. tall. It extends on down
into deeper water, becoming more laxly branched in depths of 20 to
25 feet, and even more brightly colored.

182b Branching monopodial, the branches not unilateral.

183

172

HOW TO KNOW THE SEAWEEDS

183a Thallus with a large, central axial filament running through the
medulla 184

183b Thallus without a large, central axial filament, but with very
slender, wire-like rhizoidal filaments packed in longitudinally be-
tween the large medullary cells (See Fig. 73) 185

184a The large central axial filament with one or more similar but
smaller fUaments on either side. Fig. 229 Pikea

Fig. 229. Pikea caliioinica
Harvey

Transection of a mature
part of a plant to show the
aspect of the central axial
filament and of the two simi-
lar filaments on either side,
X 55. This species occurs
along the entire Pacific
Coast and in southern Cali-
fornia is often accompanied
by P. pinnata Setchell. It is
often 10 to 20 cm. tall, and
its branching may be- described as repeatedly and rather densely and
irregularly alternate-pinnate. P. pinnata is more regularly pinnate with
all the branches in one plane.

Figure 229

173

HOW TO KNOW THE SEAWEEDS

184b The large, central axial filament solitary in the medulla. Fig.
230 Leptocladia binghamiae

Figure 230

Fig. 230. Leptocladia binghamiae J. Agardh

A. Transection of a mature axis to show the single large central
axial filament, X 46. B. A small upper portion of a plant to show
the very irregularly pinnate branching, X 2.7. This plant often re-
sembles coarse forms of Pikea californica^ but may readily be distin-
guished by the transection. It is common in southern California, espe-
cially in drift, and reaches 15 to 30 cm. in height.

It should be pointed out that the genus Farlowia is distinguished
from Leptocladia only by means of obscure reproductive characters
the examination of which cannot be undertaken by the beginning
student. However, as Leptocladia apparently does not occur in central
CaUfornia and northward, one may assume that plants keying out here
from those regions may well belong to Farlowia.

174

HOW TO KNOW THE SEAWEEDS

185a Rhizoidal filaments usually aggregated in the central part of the

medulla; cystocarps with only one ostiole. Figs. 231, 232

Pterocladia

Figure 231

Fig. 231. Pterocladia caloglossoides (Howe) Dawson

A small portion of a branch showing two uniostiolate cystocarps,
X 16. In Gelidium, an ostiole appears on both bulging sides of the
cystocarp.

Figure 232

Fig. 232. Pterocladia pyramidale
(Gardner) Dawson

A very small apical portion of
an axis to show the pinnate
branching and more or less pyra-
midal form, X 2.5. This is a com-
mon, intertidal plant of southern
California, often being a dominant
rock-cover alga. It is seasonally
variable in form, and old indi-
viduals often show much attenu-
ation of the ultimate branches
which become dense and some-
what matted. Other species of this
genus occur along the California
coast, but are small (P. caloglos-
soides) or scarce and local.

175

HOW TO KNOW THE SEAWEEDS

185b Rhizoidal filaments usually aggregated in the outer portion of the

medulla; cystocarps with two ostioles. Fig. 233

Gelidium (in part)

Figure 233

Fig. 233. Gelidium puipuiacens Gardner

A small portion of a tetrasporangial plant, X 8. This is only one
of several similar, moderate to large species of Gelidium inhabiting
rocky intertidal and infratidal areas along the Pacific Coast. They ore
usually strongly compressed in shape, but not very flat. (See also
step 45a) G. carfiiagineum variety robustum Gardner, which occurs
along the entire coast, but especially in California, is the largest and
most abundant. It has been harvested by diver in southern Cah-
fornia for the making of agar, especially during World War II when
the demand for domestic agar weeds was great and the Japanese
supply cut off. Currently, the high cost of harvesting by professional
diver in the United States has favored the importation of raw Gelidium
weed from Japan and from nearby Baja California, Mexico along whose
cool shores it grows profusely.

Among the other species of Gelidium which may be recognized
along the Pacific Coast are the polystichously branched G. poiysfichum
from the southern California Channel Islands, and G. papeniussii from
southern California which is distichous and distinguished by tetraspor-
angial branchlets with long, slender "stipes." G. pulchrum from south-
ern California is a rather delicate species with tetrasporangia borne
in short, clavate ultimate branchlets.

176

HOW TO KNOW THE SEAWEEDS

186a Medulla entirely composed of parenchyma type cells. Fig. 234. . .
GracilaTia foJii/era

Fig. 234. Gracilaria toliifera
(Forskal) Borgesen

An entire small plant
showing the irregular
branching in one plane,
X 0.64. This is a common
and exceedingly variable
plant ranging along the At-
lantic Coast from Florida to
Massachusetts in a variety
of habitats, often in quiet,
shallow water. It is our
only common and wide-
spread representative of a
varied assemblage of flat
species of Gracilaria, usu-
a 1 1 y of subdichotomous
branching. See step 23a
for comments on cylindri-
cal species of this genus.

Figure 234

186b Medulla composed of filamentous cells. Fig. 235 187

Fig. 235. Grateloupia sp.

A pojtion of a transection of a thallus
to show the structure of filamentous type
cells. The medullary cells are seen to be
slender, often branched filaments loose-
ly arranged in a jelly-like matrix.

Figure 235

177

HOW TO KNOW THE SEAWEEDS

187a Tetrasporangia borne in globose masses inside the cortex. Fig.
236 Gigartina (in part)

Fig. 236. Gigartina canaliculaia
Harvey-
Part of a cystocarpic plant ex-
tracted from a clump, X O-^- This
is one of the commonest inter-
tidal algae along the CaHfomia
coast, extending northward into
Oregon. It is often a dominant
member of rock-cover associations.

Another species which may best
key out here is the CaHfomian G.
leptorhynchos J. Agardh which is
of blackish color and provided
with abundant, small, slender,
spinose outgrowths on all sur-
faces.

For comments and illustrations
of other forms of Gigartina see
steps 151a and 168a.

I

J

Figure 236

187b Tetrasporangia not borne in globose masses inside the cortex but
scattered and more or less solitary, or in nemathecia. Fig. 237. . 188

Fig. 237. Grateloupia sp.

One of the soHtary. scattered tetrasporangia
as found in this genus in contrast to the glo-
bose masses occurring in Gigartina.

Figure 237

178

HOW TO KNOW THE SEAWEEDS

188a Tetrasporangia borne in nemathecia; medulla prominent, densely
stuffed with ramified filaments. Fig. 238 Zanardinula (in part)

Fig. 238. Zanardinula lanceolata (Harvey) J. De Toni

A small portion of an axis, X 0.8. This is per-
haps the commonest and most widespread of the
several species of this genus along the Pacific Coast.
It occurs from southern Cahfornia to northern Wash-
ington, and often reaches large, conspicuous size
(35 cm.). Other common, non-dichotomous species
from central California northward are Z. anderson-
iana (J. Agardh) Papenfuss and Z. lyallii (Harvey)
J. De Toni, both of which have much broader, more
Hgulate blades.

Figure 238

188b Tetrasporangia scattered in the
cortex (Fig. 237); medulla of loose
filaments in a soft jelly. Figs. 235,
239 GrafeJoupia iilicina

Fig. 239. Grateloupia filicina (Wulfen)
C. Agardh

An entire small plant of a rather
broad form, X 0.8. This is an exceed-
ingly variable species occurring in
warm seas in many parts of the world.
On our coasts it may be encoimtered
from North Carolina southward and
along the Gulf coast.

Figure 239

179

THE MARINE FLOWERING PLANTS

LTHOUGH the vast majority of seashore plants are algae,
there are many localities along both the Atlantic and the
Pacific coasts of the United States at which one will find
at least one kind of flowering plant growing under strictly
marine conditions in intertidal water or below. Some-
times these "sea grasses" may be so abundant as to form

great beds on sand, mud or rocks to the virtual exclusion of other

kinds of plants.

Inasmuch as there are only a tew kinds of these "sea grasses" a
key to them is unnecessary, and they may readily be identified by the
use of the illustrations and notes which follow. Each of the common
genera is illustrated. Only Halophila is omitted, for it may be en-
countered in quantity only in the Florida keys. Its species have small
elliptical, petiolate leaves.

Fig. 240. Zosfera marina Linnaeus (Eel Grass) A, B, C, X 0.5; D, X 1.

This is our most common and widespread marine flowering plant.
It occurs along the Atlantic Coast from southern North Carolina north-
ward, and, in favorable locahties, along the entire Pacific Coast of the
United States. It commonly lives on tidal mud flats and in bays and
estuaries from low tide level down to twenty feet or more. The illus-
trations marked "A, B, C" show three variants of this species of which
the narrow-leaf forms "A, B" are like those found along the Atlantic
Coast and in some sheltered bays and estuaries along the Pacific. The
large, broad-leaf form shown in "C" is known as Zostera marina var.
latifolia Morong, and is the commoner form of Pacific shores. Along
the open southern California coast it is often found on sandy bottoms
in depths of fifteen feet or more. Fragments of the plants are com-
monly cast up on sandy beaches.

The flowers and fruits of eelgrass are rather obscure. Part of a
fertile stem (spadix) is shown at "D," and two developing seeds are
visible where the enveloping spathe does not completely cover them.

Because eelgrass is an important food plant of birds and of many
marine animals along our coasts, it received a great deal of attention
about twenty years ago following its almost complete disappearance
from the Atlantic Coast in 1931-32. The importance of this destructive
"wasting disease" of Zostera led to much scientific research in an at-
tempt to determine its cause, and although not proved, the most likely
cause is now thought to have been a parasitic mycetozoan, Labyrinthula,
living within its leaves. It took about fifteen years for the eelgrass to
return to normal growth, apparently through the development of strains
more resistant to the parasite.

180

HOW TO KNOW THE SEAWEEDS

Figure 240

181

HOW TO KNOW THE SEAWEEDS

Fig. 241. Phyllospadix torreyi S.
Watson (Torrey's Surf Grass) X
0.4.

This is one of two species of
Surf Grass which occur widely
along our Pacific Coast. Unlike
Zostera, these plants normally
grow in rocky places from inter-
tidal levels down to as much as
50 feet along surfy shores. P. tor-
reyi has narrow, compressed,
somewhat wiry leaves and long
flowering stems bearing several
spadices as shown in the figure.
It occurs from northern California
southward. Phyllospadix scouleii
Hooker, our only other species,
has thinner, shorter leaves and
short, basal flowering stems bear-
ing only one or two spadices. It
is often exceedingly abundant,
forming extensive emerald green
masses on rocky reefs near mean
low tide line. It occurs along the
entire Pacific Coast from Vancou-
ver Island into Mexico. Both of
these plants are commonly mis-
taken by the layman for eelgrass.
The seaweed collector should not
overlook the fact that a number
of species of algae are to be found
hidden beneath the protecting lay-
er of surf grass leaves on the reefs.
If one simply spreads and opens
up the mantle of leaves to reveal
the inhabitants under them, he will
find many species which other-
wise might be passed over un-
seen.

Figure 241

182

HOW TO KNOW THE SEAWEEDS

Fig. 242. Thalassia testu-
dinum Koenig & Sims

(Turtle Grass), X 0.6.

This plant occurs in
vast submarine fields
around the Florida coasts,
from near low tide level
to as much as 35 feet. So
abundant is it that in
many places the leaves
are washed ashore in suf-
ficient quantities to be
gathered for fertilizer. The
rich vegetation of these
marine meadows provide
abundant food for marine
animals, and in former
times supported enorm-
ous numbers of sea tur-
tles. The broad, strap-
hke leaves distinguish it
from the other marine
seed plants of the Florida
area. It occurs outside
the range of Zostera, so
need not be confused with
that plant.

Figure 242

183

HOW TO KNOW THE SEAWEEDS

Fig. 243. Synngodium filitorme Kiitzing,
X 0.56.

This is the Manatee Grass, better known
in botanical literature, but incorrectly so,
as Cymodocea manatorum Ascherson. The
plant was first described by Kiitzing in
1863 from a specimen collected in the
Virgin Islands and apparently mistaken
for an alga. It occurs widely along the
Florida coasts and westward to Louisiana.
It often grows on infratidal sandy bot-
toms associated with Thalassia and Diplan-
thera, from which genera it is readily dis-
tinguished by its terete or semi-terete
leaves.

Figure 243

184

HOW TO KNOW THE SEAWEEDS

Fig. 244. Diplanthera wrightii (Asch-
erson) Ascherson, X 0.8.

This is another tropical species
largely confined in our territory to
the southern coasts of Florida. It oc-
curs ,in shallow, quiet, often stagnant
water, frequently in company with
Syringodium and Thalassia. Its nar-
row flat leaves are distinctively trun-
cate and toothed at the apex, as
shown in the small inset figure.

Figure 244

185

PHYLOGENETIC LIST OF GENERA
AND FAMILIES

GREEN ALGAE — CHLOROPHYTA

Ulotrichales

Ulotrichaceae

1. Ulothrix

p. 75, fig. 96

Ulvaceae

2. Monostioma
p. 71, fig. 88

3. Ulva

p. 71, fig. 88

4. Enteromorpha

p. 95, figs. 124, 125

Cladophorales

Cladophoraceae

5. Chaetomorpha

pp. 78, 78; figs. 97. 100

6. Uiospora

p. 77, fig. 98

7. Rhizoclonium
p. 77, fig. 99

8. Spongomorpha
p. 78, fig. 101

9. Cladophora

p. 79, fig. 102

Siphonales

Halicystidaceae

10. Halicystis

p. 125, fig. 165

Valoniaceae

1 1 . Valonia

pp. 28, 75, 125, figs. 13, 95,
164

12. Dictyosphaeria
p. 90, fig. 118

Siphonocladaceae

13. CladophoTopsis
p. 80. fig. 103

Anadyomenaceae

14. Anadyomene
p. 88, fig. 83

Caulerpaceae

15. Cauleipa

pp. 72, 73, 145, 154, figs.
89, 90, 91, 188. 204

Bryopsidaceae

16. Bryopsis

p. 73, fig. 92

Codiaceae

17. Codium

p. 34, fig. 24

18. Avrainvillea

p. 142, fig. 185

19. Halimeda

p. 113, fig. 147

20. Udotea

p. 119, figs. 155. 156

2 1 . Penicillus

p. 122, fig. 160

22. Rhipocephalus
p. 123, fig. 161

Dasycladaceae

23. Dasycladus
p. 74. fig. 93

24. Batopkora

p. 74. fig. 94

25. Acetabularia

p. 120. fig. 158

26. Neomeris

p. 121. fig. 159

27. Cymopolia

p. 113. fig. 146

186

HOW TO KNOW THE SEAWEEDS

BROWN ALGAE — PHAEOPHYTA

Ectocarpales

Ectocarpaceae

28. Ectocarpus

p. 82, fig. 106

29. Pylaiella

p. 81, fig. 105

Ralfsiaceae

30. Ralfsia

p. 89, fig. 116

Dictyotales

Dictyotaceae

31. Dictyota

p. 162. fig. 214

32. Dictyopteris

p. 132, fig. 173

33. Pachydictyon
p. 162, fig. 215

34. Padina

p. 120. fig. 157

35. Zonaria

p. 134, fig. 175

Chordariales

Elachistaceae

36. Elachista

p. 81. fig. 104

Corynophlaeaceae

37. Leathesia

p. 91. fig. 119

38. PetTOspongium
p. 90. fig. 117

Chordariaceae

39. Chordaria

p. 35, fig. 26

40. Haplogloia

p. 44. fig. 41

41. Heterochordaria
p. 45. fig. 42

42. Sphaerotrichia
p. 59. fig. 65

43. Eudesme

p. 34. fig. 25

Spermatochnaceae

44. Stilophoia

p. 37, fig. 31

Desmarestiales

Desmarestiaceae

45. Desmarestia

pp. 44, 139, figs. 40, 181

Dictyosiphonales

Punctariaceae

46. Asperococcus
p. 96, fig. 126

47. Colpomenia
p. 91, fig. 120

48. Hydroclathrus
p. 88, fig. 113

49. Ilea (Petalonia)
p. 148, fig. 191

50. Punctaria

p. 149, figs. 192, 193

51. Scytosiphon
p. 97, fig. 127

52. Endarachne
p. 148

Dictyosiphonaceae

53. Dictyosiphon
p. .65. fig. 77

54. Coilodesme

p. 93, fig. 122

Laminariales

Chordaceae

55. Chorda

pp. 37, 38, figs. 30, 32

Laminariaceae

56. Agarum

p. 126. fig. 166

57. Costaria

p. 129, fig. 170

58. Hedophyllum

p. 143, fig. 186

59. Laminaria

pp. 144, 146, fig. 187

60. Phyllaiia

p. 146, fig. 189

187

HOW TO KNOW THE SEAWEEDS

61. PleuTophycus

p. 127, fig. 167

Lessoniaceae

62. DictyoneuTum
p. 128, fig. 168

63. Lessoniopsis

p. 130, fig. 171

64. MacTOcystis

p. 108, fig. 140

65. Nereocystis

p. 102, fig. 133

66. Pelaqophycus
p. 102, fig. 134

67. Postelsia

p. 156, fig. 206

Alariaceae

68. Alalia

p. 137, fig. 179

69. Egregia

p. 104, fig. 136

70. Eisenia

p. 155, fig. 205

RED ALGAE

BANGIOIDEAE

Bangiales

Bangiaceae

80. Porphyra

p. 70, fig. 86

81. Bangia

p. 32, fig. 21

FLORIDEAE

Nemalionales

Helminthocladiaceae

82. Nemalion

p. 35, fig. 27

83. Cumagloia
p. 36. fig. 28

84. Helminthocladia
p. 36, fig. 29

85. Liagora

p. 124, fig. 163
Bonnemaisoniaceae

86. Bonnemaisonia
p. 61. fig. 69

71. Pterygophora

p. 139, fig. 180

Fucales

Fucaceae

72. Ascophyllum

p. 108, fig. 139

73. Fucus

pp. 104, 133, figs. 135, 174

74. Hesperophycus
p. 131, fig. 172

75. Pelvetia

pp. 158, 159, fig. 209

76. Pelvetiopsis

p. 158, fig. 208

Cystoseiraceae

77. Cystoseira

p. 106. fig. 138

78. Halidrys

p. 106, fig. 137

Sargassaceae

79. Sargassum

p. 110. fig. 141

RHODOPHYTA

Chaetangiaceae

87. Galaxauia

p. 124. fig. 162

Gelidiales

Gelidiaceae

88. Gelidium

pp. 63, 64, 176, figs. 73,
74, 233

89. Pterocladia

p. 175, figs. 231, 232

Cryptonemiales

Dumontiaceae

90. Dumontia

p. 98. fig. 129

91. Farlowia
p. 174

92. Pikea

■ p. 173. fig. 229

93. Constantinea
p. 141, fig. 184

188

HOW TO KNOW THE SEAWEEDS

94. Leptocladia

p. 174, iig. 230
Endocladiaceae

95. Endocladia

pp. 56, 60, figs. 58, 66

Squamariaceae

96. Peysonnelia
p. 89, fig. 115

Hildenbrandiaceae

97. Hildenhrandia
p. 88, fig. 114

Corallinaceae

98. Lithothamnium

pp. Ill, 112, figs. 143,
144

99. Goniolithon
p. 112

100. Lithophyllum

p. 112, fig. 145

101. Bossea

pp. 110, 114, 115, figs.
142, 148, 150

102. Calliarthron

p. 115, fig. 149

103. Jania

p. 116, fig. 151

104. Corallina

p. 117, fig. 152

105. Lithothrix

p. 117, fig. 153

106. Amphiroa

p. 118, fig. 154

Grateloupiaceae

107. Grateloupia

pp. 150, 152, 177, 178,
179, figs. 194, 200, 235,
237, 239

108. Halymenia

p. 151, figs. 196, 197

109. Zanardinula

pp. 160, 179, fig. 211,
238

110. Cryptonemia

pp. 152, 153, figs. 198,
201

Callymeniaceae

111. Callophyllis

' p. 163, Figs. 216, 217

Gigartinales

Nemastomaceae

112. Schizymenia

p. 150, fig. 195

Solieriaceae

113. Agardhiella
p. 39, iig. 34

114. Eucheuma
p. 40, fig. 35

115. Opuntiella

p. 157, fig. 207

Hypneaceae

116. Hypnea

pp. 60, 61, 62, figs. 67
68, 71

Rhodophyllidaceae

117. Cystoclonium
p. 65, fig. 76

Plocamiaceae

118. Plocamium

p. 172. fig. 228

Gracilariaceae

119. Gracilaria

■ pp. 42, 177, figs. 38.
234

120. Gracilariopsis

pp. 41, 43, figs. 37, 39

Phyllophoraceae

121. Gymnogongrus

pp. 40, 167, figs. 36.
223

122. Stenogramme
p. 164, fig. 219

123. Phyllophora

p. 168, fig. 224

124. Ahnfeltia

p. 33, fig. 23

Gigartinaceae

125. Gigaitina

pp. 147, 159, 178, figs.
190, 210, 236

189

HOW TO KNOW THE SEAWEEDS

126. Rhodoglossum

pp. 154, 161, figs. 203,
213

127. Iridophycus

pp. 152, 153. figs. 199.
202

128. Chondrus

p. 161. fig. 212

Rhodymeniales

Rhodymeniaceae

129. Halosaccion

pp. 92. 97. figs. 121,
128

130. Botryocladia
p. 100. fig. 131

131. Fauchea

p. 166. fig. 221

132. Rhodymenia

pp. 164-166. figs. 218.
220. 222

Champiaceae

133. Champia

p. 94. fig. 123

134. Lomentaiia

p. 99. fig. 130

135. Gastroclonium
p. 101. fig. 132

Ceramiales

Ceramiaceae

136. Spyridia

p. 47. fig. 44

137. Wrangelia

p. 51. fig. 51

138. Ceramium

pp. 46. 47. 56, 57. figs.
43. 45, 57. 60. 61

139. Centroceias
p. 56. fig. 59

140. Callithamnion

pp. 49. 51. 52. 84. 85,
figs. 49. 52, 108

141. Seirospora

pp. 51, 52, fig. 53

142. Antiihamnion
p. 83, fig. 107

143. PleonospoTium
p. 86. fig. 110

144. Griff ithsid

p. 87. fig. Ill

145. Speimothamnion

pp. 85. 87. figs. 109.
112

146. Plumaiia

p. 169. fig. 225

147. Microcladia
p. 64, fig. 75

Delesseriaceae

148. Grinnellia

p. 69, fig. 84

149. Phycodiys

p. 69. fig. 85

150. Myiiogramme
p. 71. fig. 87

151. Polyneura

p. 128. fig. 169

152. Hymenena

p. 134. fig. 176

153. Botryoglossum
p. 135. fig. 177

154. Cryptopleura
p. 136. fig. 178

155. AcTOSorium

p. 140. fig. 182

156. Nienhurgia

p. 140, fig. 183

Dasyaceae

157. Dasya

pp. 49. 50. figs. 48. 50

158. Heterosiphonia

p. 48. figs. 46. 47

Rhodomelaceae

159. Chondria

pp. 57. 63. figs. 62. 72

160. Laurencia

pp. 55, 58. 171, figs. 56.
63, 64, 227

161. Acanthophora
p. 62. fig. 70

190

HOW TO KNOW THE SEAWEEDS

162. Rhodomela

p. 66, fig. 78

163. Herposiphonia
p. 66, fig. 79

164. Lophosiphonia
p. 53, fig. 54

165. Polysiphonia

pp. 53, 67, figs. 54, 80

166. Pterosiphonia
p. 67, iig. 81

167. Pterochondna
p. 68, fig. 82

168. Odonthalia

p. 170, fig. 226

169. Digenia

p. 54, fig. 55

191

INDEX AND PICTURED-GLOSSARY

Note that the numbers within parentheses following the generic names refer to the
phylogenetic list of genera at which place the page and figure numbers are also given.

Avrainvillea (No. 18) 142

Acanthophora (No. 161) 62
spicifera 62

ACCESSORY NUTRITIVE
FILAMENTS: in the genus
Gracilaria, those filaments
which extend from the go-
nimoblost to the pericarp
and which apparently
serve as an accessory of
nourishing the developing
carpospores.

Acetabularia (No. 25) 120
crenulata 1 20

Acrosorium (No. 155) 140
uncinatum 1 40

Agardhiella (No. 113) 39
coulteri 39
tenera 39

Agarum (No. 56) 126
cribrosum 1 26
fimbriatum 1 26

Ahnfeltia (No. 124) 33
concinna 33
plicata 33

Alaria (No. 68) 137
fistulosa 1 37
marginata 1 37

Amphiroa (No. 106) 118
fragilissima 1 1 8
zonata 1 1 8

Anadyomene (No. 14) 68
stellata 68

ANASTOMOSING; running
together and fusing in
such a way that the con-
nections form a reticula-
tion.

ANISOGAMOUS: having un-
ion of flagellated gametes
of dissimilar size.

ANTICLINAL: perpendicular
to the surface, as in the
outer cortical cells in Fig.
245.

B

Figure 245

Antithamnion (No. 142) 83
APEX: (pi. APICES): the

top or terminal end.
APICAL: at the apex.
ARCUATE: curved or bowed.
Ascophyllum (No. 72) 108

nodosum 1 08
Asperococcus (No. 46) 96

echinatus 96

Bangia (No. 81) 32

fuscopurpurea 32
Batophora (No. 24) 74

oerstedi 74
BLADE: that part of a thol-

lus which is erect and

more or less flattened or

leaf-like.
Bonnemaisonia (No. 86) 61

hamifera 61

nootkana 61
Bossea (No. 101) 110, 114,

1 15
Botryocladia (No. 130) 100

pseudodichotomo 1 00
Botryoglossum (No. 153) 135

farlowianum 135
Bryopsis (No. 16) 73

hypnoides 73

pennata 73

plumosa 73

CALCAREOUS: impregnated
with calcium carbonate.

Calliarthron (No. 102) 115
cheilosporioides 1 1 5

Callithamnion (No. 140) 49,
51, 52, 84, 85
pikeanum 51
rupicolum 84

Callophyllis (No. Ill) 163
marginifructa 163

CARPOGONIUM: the female
sex organ in the Red Al-
gae. In Fig. 246 a car-
pogonial branch (shaded)
is shown from a cross sec-
tion of a thallus of the
Gracilariaceae. The car-
pogonium is the dilated
portion of the uppermost
cell. The slender, neck-
like part is called the
trichogyne.

Figure 246

CARPOSPOROPHYTE: that
phase of the life history
of a red alga arising di-
rectly or indirectly from
the carpogonium and

borne on the female ga-

metophyte. At maturity

carpospores are produced

from corposporangio on

gonimoblast filaments.
Caulerpa (No. 15) 72, 73,

145, 154

crassifolia 1 54

fastigiata 72

prolifera 145

racemosa 11

verticillata 72
Centroceras (No. 139) 56

clavulatum 56
Ceramium (No. 138) 46, 47,

56, 57

avalonae 47

codicola 57

eotonianum 57

pacificum 57

rubrum 57
Chaetorr.orpho (No. 5) 76,

78

aerea 76

antennina 76

linum 78

melagonium 76

torta 78
Champia (No. 133) 94

parvula 94

salicornioides 94

CHLOROPLAST: the green,

pigmented body or bodies

within the cells of green

algae.
Chondria (No. 159) 57, 63

sedifolia 57

tenuissima 63
Chondrus (No. 128) 161

crispus 1 6 1
Chorda (No. 55) 37, 38

filum 37, 38

tomentosum 38
Chordaria (No. 39) 35

dissessa 35

flagelliformis 35
Cladophora (No. 9) 79

albida 79

trichotoma 79
Cladophoropsis (No. 1 3) 80

membranacea 80
Codium (No. 17) 34

dichotomum 34

fragile 34

COENOCYTIC: consisting of
one or more multinucleate
cells. Coenocytic Green
Algae may have frequent
cell walls as in Chaeto-
morpha and Cladophora,
or may be variously
branched and ramified
without cross walls in the
filaments, as in Caulerpa
and Bryopsis.

Coilodesme (No. 54) 93
californica 93
rigida 93

Colpomenia (No. 47) 91
sinuosa 9 1

COMPLANATE: strongly flat-
tened and more or less
expanded.

192

HOW TO KNOW THE SEAWEEDS

COMPRESSED: somewhat
flattened.

CONCEPTACLE: a cavity
(either sunken or within
a raised dome) with one
or more openings to the
thallus surface and bear-
ing reproductive organs.
Usage in the Red Algae
is largely restricted to the
family Corallinaceae.

Constantinea (No. 93) 141
simplex 1 4 1

Corallina (No. 104) 117
officinalis 1 1 7
vancouveriensis 1 1 7

CORONATE: in the form of
a crown; provided with
a crown.

CORTEX: the outer tissue
of a thallus external to
the medulla and (or) the
central axial filament and
usually of smaller or
shorter cells, some of
which are pigmented. In
Fig. 247 a cross section
of a cylindrical red alga
is shown in which a cen-
tral axial filament is
present within a large-
celled medulla which in
turn is surrounded by a
small-celled cortex.

Figure 247

CORTICAL: pertaining to the
cortex.

CORTICATED: provided with
a cortex, often by second-
ary growth from the axis.

Costaria (No. 57) 129
costata 1 29

Cryptonemia (No. 110) 1 52,
153
obovata 1 52, 1 53

Cryptopleura (No. 154) 136
violacea 1 36

CRYPTOSTOMATA: sunken
cavities in a thallus (ap-
plied to certain Brown
Algae) containing only
hairs.

Cumagloia (No. 83)' 36
andersonii 36

Cymodocea 1 84
manatorum 1 84

Cymopolia (No. 27) 113
barbata 1 1 3

CYSTOCARP: the "female"
reproductive structure in
most Red Algae. It con-

sists in the Florideae of
carpospores and gonimo-
blast filaments, and, when
the cystocarp protrudes
from the surface of the
thallus, of a special peri-
carp. The cystocarp may
be deeply embedded in
the thallus (as in Fig. 248)
or emergent and protrud-
ing. One or more osti-
oles may be present.

Figure 248

Cystoclonium (No. 117)

purpureum 65
Cystoseira (No. 77) 106

osmundacea 1 06

65

Dasya (No. 157) 49, 50
pacifica 50
pedicellata 50

Dasycladus (No. 23) 74
vermicularis 74

DECIDUOUS: falling off af-
ter a time.

Desmarestia (No. 45) 44,
139

aculeata 139
farcta 44
media 44
munda 1 39
viridis 44

DETERMINATE BRANCHES:
branches having a more
or less definite limit to
their length of growth.

DIAPHRAGM: a cellular par-
tition across a hollow por-
tion of a thallus.

DICHOTOMOUS: forked (us-
ually repeatedly).

Dictyoneurum (No. 62) 128
californicum 1 28

Dictyopteris (No. 32) 132
delicatuia 132
justii 1 32
plagiogramma 1 32
polypodioides 1 32
zonarioides 1 32

Dictyosiphon (No. 53) 65
foeniculaceus 65

Dictyosphaeria (No. 12) 90
cavernosa 90

Dictyota (No. 31) 162
dichotoma 162
flabellata 162

Digenia (No. 169) 54
simplex 54

Diplanthera 185
wrightii 185

DIPLOID: the condition in
the life history of an alga
in which each cell has

double the haploid num-
ber of chromosomes

DISCOID: in the form of a
disc.

DISTICHOUS: in two ranks

DISTROMATIC: consisting of
two layers of cells.

Dumontia (No. 90) 98
incrasiata 98

Ectocarpus (No. 28) 82
Egregia (No. 69) 104

laevigata 1 04

menziesii 1 04
Eisenia (No. 70) 1 55

arborea 1 55
Elachista (No. 36) 81

fucicola 8 1
Endarachne (No. 52) 148

binghamiae 1 48
Endocladia (No. 95) 56, 60

muricata 56, 60
Enteromorpha (No. 4) 95

clathrata 95

linza 95

tubulosa 95
EPIPHYTIC: growing at-
tached to another plant.
ESTIPITATE: without a stipe.
Eucheuma (No. 114) 40.

isiforme 40
Eudesme (No. 43) 34

virescens 34

Farlowia (No. 91) 174
Fauchea (No. 131) 166
fryeana 1 66
laciniata 1 66
FILAMENTS (cell form): the
slender, elongated form
assumed by certain cells,
especially in the medulla
of many Red Algae, Fiq.
249.

Figure 249

FLABELLATE: shaped more
or less like a fan.

FLABELLUM: the fan-like
portion of a thallus.

FLAGELLATED: provided with
a flagellum.

FLAGELLUM: a whip - like
process of protoplasm
which provides locomo-
tion for a motile cell.

193

HOW TO KNOW THE SEAWEEDS

Fucus (No. 73) 22, 104, 133

edentatus 1 33

evanescens 1 04

ves/cu/osus 1 04
FURCATE: forked.

leptophyllus 167
linearis 1 67
norvegicus 1 67
platyphyllus 167

H

Ga/oxQuro (No. 87) 124
oblongata 1 24
marginata 1 24
subvert;ci//ata 1 24

GAMETANGIUM: a sexual
organ containing one or
more gametes.

GAMETOPHYTE: in the life
history of an alga, the
sexual generation which
usually consists of sepa-
rate male and female
plants and which produces
motile or non-motile ga-
metes.

Gastroclonium (No. 132) 101
coulteri 101

Gelidium (No. 88) 63, 64,

176

cartilagineum 1 76

crinale 63
nudifrons 64
papenfussii 1 76
polystichum 1 76
pulchrum 1 76
purpurascens 1 76

G;'gart/no (No. 125) 147,
159, 178
canaliculata 178
cristata 1 59
harveyana 1 47
leptorhynchos 178
stellata 159

GLAND CELL: a specialized,
non-pigmented cell, usu-
ally distinguished from
neighboring cells of a tis-
sue (in certain Red Al-
gae).

GONIMOBLAST: that portion
of the cystocarp which
produces the carposporan-

GON^MOBLAST PLACENTA:
in the Gracilariaceae, the
subparenchyrhatous cen-
tral part of the gonimo-
blast mass within the peri-

Goniohthon (No. 99) 112
Gracilaria (No. 119) 24, 42,

177

foliifera 1 77

verrucosa 42
Gracilariopsis (No. 120) 41,

43

andersonii 43

sjoestedtii 41. 43
Grateloupia (No. 107) 150,

152, 177, 178, 179

filicina 150, 179

maxima 1 52

schizophylla 150, 152
Griffithsia (No. 144) 87

globulifera 87

pacifica 87

tenuis 87
Grinnellia (No. 148) 69

americana 69
Gymnogongrus (No. 121) 40,
167

griff ithsine 40, 167

HAIR: a unicellular or mul-
ticellular filament growing
from the surface of a
thallus. Fig. 250 shows a
unicellular hair.

Figure. 250

Halicystis (No. 10) 125

ova lis 1 25
Halidrys (No. 78) 106

dioica 1 06
Halimeda (No. 19) 113

discoidea 1 1 3
Halophila 1 80
Halosaccion (No. 129) 92
97

glandiforme 92
ramentaceum 97
Halymenia (No. 108) 151
calif arnica 151
gelinaria 151
HAMATE: sickle-shaped.
Haplogloia (No. 40) 44

andersonii 44
HAPLOID: the condition in
the life history of an alga
in which each cell has
the number of chromo-
somes characteristic of a
gamete.
HAPTERON (pi. haptera): a
course, usually cylindrical,
branched basal organ of
attachment.
Hedophyllum (No. 58) 143

sessile 143
Helminthocladia (No. 84) 36

californica 36
Herposiphonia (No. 163) 66

tenella 66
Hesperophycus (No. 74) 131

harveyonus 1 3 1
Heterochordaria (No. 41) 45

abietina 45
HETEROMORPHIC (alterna-
tion of generations): dis-
similar in form and in es-
sential structure.
Heterosiphonia (No. 158) 48
erecta 48
gibbesii 48

Hildenbrandia (No. 97) 8

prototypus 88
Hydroclathrus (No. 48) 88

clathratus 88
Hymenena (No. 152) 134

flabelligera 1 34
Hypnea (No. 116) 60, 61, 62

cervicornis 62

cornuta 62

musciformis 61, 62

Ilea (No. 49) 148
fascia 1 48

INDETERMINATE BRANCH-
ES: branches having no
definite limitation on the
length to which they may
grow.

INDETERMINATELY: with-
out definite limitation of
growth.

INTERCALARY: inserted or
occurring between other
things or parts; not at
the apex or at the base.

INTERGENICULAR MEDUL-
LA: the central, internal
tissue of a calcified seg-
ment of a jointed coral-
line alga.

Iridophycus (No. 127) 152,
153
flaccidum 1 53

ISODIAMETRICAL: of ap-
proximately the same di-
ameter in all dimensions,
such as the large subcor-
tical cells in Fig. 251.

Figure 251

ISOGAMOUS: having union
of gametes which are cf
the same size.

ISOMORPHIC (alternation cf
gentrations): similar in
external form but not in
essential structure.

Jania (No. 103) 116
capillacea 1 16
tenella 1 16

194

HOW TO KNOW THE SEAWEEDS

Laminaria (No. 59) 22, 144,

146

agardhii 1 46

digitata 1 44

faeroensis 1 46
Laurencia (No. 160) 55, 58,

171

diegoensis 1 7 1

obtusa 58

pacifica 59

papulosa 58

spectabilis 1 7 1

splendens 1 7 1
Leathesia (No. 37) 91

difformis 91
Leptocladia (No. 94) 174

binghamiae 1 74
Lesson/'ops/'s (No. 63) 130

littoralis 1 30
Liagora (No. 85) 124

californica 1 24

ceranoides 1 24
LIGULATE: strap-shaped.
Lithophyllum (No. 100) 112
Lithothamnium (No. 98 111,

112

giganteum 1 1 1
Lithothrix (No. 105) 117

aspergillum 1 1 7
Lomentaria (No. 134) 99

baileyana 99
Lophosiphonia (No. 164) 53

M

MULTIZONAL: consisting of
more than one zone or
tier of cells.

Myr/ogromme (No. 150) 71
spectabilis 7 1

N

Nemalion (No. 82) 35
helminthoides 35
multifidum 35

NEMATHECIUM: a special-
ized form of tetrcsporan-
gial sorus which is usually
somewhat elevated above
the surface and in which
the cortex is modified to
produce elongated cells or
rows of cells (paraphyses)
among which the tetra-
sporangia are borne (Fig.
252). Usage is restricted
to the Florideae.

Macrocystis (No. 64) 108
integrifolia 1 08
pyrifera 1 08

MACROSPORANGIUM: the
sporangium producing the
larger of two dissimilar
sized spores, as in Pel-
vet ia.

MEDULLA: the central tis-
sue of the thallus beneath
the cortex and usually of
non-pigmented cells.

MEDULLARY: pertaining to
the medulla.

MEMBRANOUS: thin and
flat, like a membrane.

MERISTEM: a tissue of a
point or region in which
growth is initiated.

Microcladia (No. 147) 64
borealis 64
californica 64
coulteri 64

MIDRIB: a vein- or rib-like
structure running up the
middle of a blade.

MONILIFORM: in the form
of a string of beads.

MONOPODIAL: a method of
branching in which a main
axis produces lateral
branches subordinate to
itself.

Monostroma (No. 2) 71.

MONOSTROMATIC: consist-
ing of only one layer of
cells.

MULTIFARIOUS: in many
planes (branching).

MULTISERIATE: of several
or more rows or series of
cells.

Figure 252

121

102

Neomeris (No. 26)
annulata 121

Nereocystis (No. 65)
luetkeana 1 02

Nienburgia (No. 156) 140
andersoniana 1 40
borealis 1 40

NODES: the rings formed by
the junction of each suc-
cessive axial cell with the
next (as in CaUithamnion
and Wrangelia).

Odonthalia (No. 168) 170
floccosa 1 70

Opuntiella (No. 115) 157
californica 1 57

OSTIOLE: the^pore-like aper-
ture of a pericarp or of
a conceptacle.

PALMATE: diverging in the
manner of the fingers
from the palm of the
hand.

Pachydictyon (No. 33) 162
coriaceum 1 62

Padina (No. 34) 120
sanctae-crucis 1 20
vickersiae 1 20

PAPILLAE: nipple-like out-
growths from the surface
of a thallus.

PARAPHYSIS (pi. -SES): a
sterile filament produced
adjacent to or in con-
nection with the develop-
ment of a reproductive
organ.

PARENCHYMATOUS: a tis-
sue in which the cells are
relatively large, thin-
walled and more or less
isodiametrical.

PARIETAL: borne against
the cell wall on the in-
side of the cell.

Pelagophycus (No. 66) 102
porra 1 02

Pelvetia (No. 75) 158, 159
fastigiata 158, 159

Pelvetiopsis (No. 76) 158
limitata 158

Penicillus (No. 21) 122
capitatus 1 22

PERCURRENT: running
through to the end (as a
vein or midrib in a blade.
Fig. 253); extending
throughout the length (as
an axis of a thallus).

Figure 253

PERICARP: the sterile, en-
veloping wall surrounding

the gonimoblast in certain

red algae.
Petalonia, see Ilea (No. 49)

148
Petrospongium (No. 38) 90

rugosum 90
Peysonnelia (No. 96) 89
Phycodrys (No. 149) 69

rubens 69

setchellii 69
Phyllaria (No. 60) 146

dermatodea 1 46
P'hyllophora (No. 123) 168

brodiaei 1 68

clevelandii 1 68

membranifolia 168
Phyllospadix 1 82

scouleri 1 82

torreyi 182

195

HOW TO KNOW THE SEAWEEDS

Pikea (No. 92) 173
californica 173
pinnata 173

PINNATE: with the branches
in a rank on either side
of the axis.

PLASMOLYSIS: the contrac-
tion and shrinking of the
cytoplasm of a cell (and
sometimes the collapse of
the cell wall as well) as
a result of loss of water
through exosmosis.

Pleonosporium (No. 143) 86
borreri 86
dosyo/des 86

Pleurophycus (No. 61) 127
gardneri 1 27

Plocamium (No. 118) 172
pad fi cum 17?
violaceum 1 72

Plumana (No. 146) 169
californica 1 69
densa 1 69
filicina 169
hypnoides 1 69
pectinata 1 69
sericea 169

PNEUMATOCYST: an air
bladder or vesicle.

Polyneura (No. 151) 128
latissima 1 28

Polysiphonia (No. 165) 53
67

POLYSIPHONOUS: provided
with transverse tiers of
parallel, vertically elongat-
ed cells of approximately
equal length, Fig. 254.

sions produce more than
four spores (polyspores).
Fig. 255.

\OD00'
lOQDCD

inmrn

Figure 254

POLYSPORANGIUM: on asex-
ual reproductive structure
in the Red Algae (Flori-
deae) in which the divi-

Porphyra (No. 80) 70

perforata 70
Postelsia (No. 67) 156

palmaeformis 1 56
PROLIFEROUS: producing

outgrowths similar to the

original.
Pterochondria (No. 167) 68

wood a 68
Pterocladia (No. 89) 175

caloglossoides 175

pyramidale 175

I 67
139

Pterosiphonia (No. 166

dendroidea 67
Pterygophora (No. 71)

californica 1 39
Punctaria (No. 50) 149

lati folia 149

plantaginea 149
Pylaiella (No. 29) 81

litoralis 81

RADIALLY SYMMETRICAL:
having similar parts regu-
larly arranged about o
central axis.

Ralfsia (No. 30) 89

RECEPTACLE: in the Fucales
a fertile branch or branch
tip bearing reproductive
conceptacles.

RETICULATE:
form.

Rhipocephalus
oblongus 1 23
phoenix 1 23

Rhizoclonium (No. 7) 77
kerneri 77

RHIZOID: a unicellular or
uniseriate root-like fila-
ment serving for attach-
ment, Fig. 256.

of net-like
(No. 22) 123

RHIZOIDAL FILAMENT: a
very slender, long, thick-
walled cell with exceed-
ingly small cavity, found
in the medulla of certain
Gelidiaceoe. The cell walls
hove the form of the rub-
ber insulation of a heavy
duty electric wire.

Rhodoglossum (No. 126) 154
161
affine 154, 161

Rhodomela (No. 162) 66
larix 66
subfusca 66

Rhodymenia (No. 132) 164,
165, 166
pacifica 166
palmata 1 66
pertusa 167

Sargassum (No. 79) 110
agardhianum 1 1 6
filipendula 1 1
fluitans 1 10
natans 1 1
palmeri 1 1

SAXICOLOUS: growing at-
tached to rocks.

Schizymenia (No. 112) 150
pacifica 1 50

Scytosiphon (No. 51) 97
lomentaria 97

SEGMENTED: divided into
segments or joints; articu-
lated, as in Corallina sp.
Fig. 257.

Figure 257

Figure 256

SEGMENTS: the portions or
divisions of a thallus be-
tween points of branch-
ing; or, specifically in
articulated corallines, the
calcified portions (inter-
genicula) between the ar-
ticulations.

Seirospora (No. 141), 51, 52
griffithsiana 51, 52

SEPTATE: provided with
cross walls or partitions.

196

HOW TO KNOW THE SEAWEEDS

SESSILE: borne without o
stipe or stalk.

SIMPLE: unbranched.

SOLITARY: consisting of only
one; each one separate
by itself.

SORUS (pi. sori): an aggre-
gation of reproductive or-
gans in a particular re-
gion or associated with
some specilization of struc-
ture.

SPADIX: a kind of inflores-
cence in certain marine
seed plants.

SPATHE: a large bract en-
closing a spadix.

SPERMATIA: the non-motile
male gametes of the Red
Algae.

Spermothamnion (No. 145)
85, 87
snyderae 87
turneri 85, 87

Sphaerotrichia (No. 42) 59
divaricata 59

Spongomorpha (No. 8) 78
arcta 78
coalita 78

SPOROPHYTE: in the life
history of an alga, the
asexual generation which
produces diploid spores.

Spyridia (No. 136) 47
aculeata 47
filamentosa 47

STELLATE: provided with
points like a star.

Stenogramme (No. 122) 164
interrupta 1 64

Stilophora (No. 44) 37
rhizoides 37

STIPE: the basal, stem-like
part of a thallus beneath
an erect blade.

STIPITATE: Borne on a
stripe

STOLONIFEROUS: producing
stolons.

STUPOSE: consisting of or
provided with an abund-
ance of rhizoids or hairs
which may form a spongy
mass.

SUB-: a prefix denoting a
degree of, or an approach
to, some quality; some-
what.

SYMPODIAL: a method of
branching in which the
leading apex is regularly
and successively replaced
by a branch from below
which then assumes the
terminal position for a
time until in turn re-
placed.

Syringodium 1 84
filiforme 184

TERETE: circular in trans-
verse section.

TETRASPORANGIUM: an
asexual reproductive struc-

ture in the Red Algae
(Florideae) in which the
divisions produce four
spores (tetraspores). Fig.
258.

Figure 258

Thalassia 183
testudinum 1 83

THALLUS: the entire plant
body of an alga.

TRABECULAE: protuberances
from the inside of the
cell wall of species of
Caulerpa.

TRANSECTION: a section
cut crosswise.

TRICHOBLAST: a simple or
branched, uniseriate, hair-
like filament extending
from the surface (usually
at the tips) of certain red
algae.

TRICHOTHALLIC: a manner
of growth in which cell
division occurs at the base
of one or more apical
hairs.

TRUNCATE: as though cut
off at the end.

TUBERCULATE: warty.

U

Udotea (No. 20) 119
flabellum 1 1 9

Ulothrix (No. 1) 75
implexa 75

ULTIMATE: the last order.

Ulva (No. 3) 20, 21, 71

UNILATERAL: one-sided.

UNISERIATE: consisting of a
single row of cells, either
branched (Fig. 259), or
unbranched.

UNIZONAL: consisting of a
single zone or tier of
cells.

Urospora (No. 6) 77
penicilliformis 77

UTRICLE: a specialized, in-
flated, sac-like end of a
filament of Codium of
which the whole surface

layer of the thallus is
composed.

VACUOLATE: with scant

contents within the cell

cavity.
Valonia (No. 11) 28, 75,

125

aegagropila 75

ventricosa 28, 125
VERTICILLATE: whorled.
VESICLE: an air bladder or

float.

W

WHORLS: verticils or circles
of branches or organs
about an axis.

Wrangelia (No. 137) 51
penicillata 51

Zanardinula (No. 109) 160,

179

andersoniana 179

corne.a 1 60

lanceolata 1 79

Ivallii 179
Zonaria (No. 35) 134

far low a 1 34
Zostera 1 80

marina 180

marina var. latifolia 1 80

V-.

Figure 259

197

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