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NX. STATE UNIVERSITY D.H, HILL LIBRARY

S00275674 V

This book is due on the date indicated
below and is subject to an overdue fine
as posted at the Circulation Desk.

AMERICAN SCIENCE SERIES

ESSENTIALS OF

COLLEGE BOTANY

CHAELES E. BESSEY, Ph. D., LL. D.

HEAD PROFESSOR OP BOTANY IN THE UNIVERSITY OF NEBRASKA

AND

ERNST A. BESSEY, Ph. D.

PROFESSOR OP BOTANY IN THE MICHIGAN AGRICULTURAL. COLLEGE

EIGHTH EDITION OF "tHE ESSENTIALS OF BOTANY'
ENTIRELY REWRITTEN

With 206 Diagrammatic Illustrations

rJ . 0. UOLLEiJS OF A. & 1

,^:\^
t

NEW YORK
HENRY HOLT AND COMPANY

COPYRIGUT, 1914
BY

HENRY HOLT AND COMPANY

THE . MAPLE . PRESS • TOBK • PA

PREFACE

In offering this ])ook to college teachers it may not be
amiss to refer to the great change that has taken place
in the teaching of Botany in America since the prepara-
tion of its predecessor thirty-five years ago. Then
botanical laboratories were just coming into existence,
and for the first time students of Botany were able
to study protoplasm and cells and tissues and other
minute structures of plants. It is a matter of history
that half a dozen years later the publisher's objection
to the caption '' Laboratory Studies" for a new edition,
was able to bring about the substitution of ''Practical
Studies," as less likely to prejudice teachers against such
presentation of the subject. Looking back to that time
we realize what progress has been made in the teaching
of the science, for to-day every college has its laboratory for
the study of plant structure, and this change in teaching
has gone so far that it has invaded the secondary schools,
in which there are now many well-equipped botanical
laboratories.

Looking at the science from another standpoint it is
of interest to note that thirty-five years ago the number
of species of known plants was between 125,000 and
150,000, while to-day it has risen to more than 233,000.
Then the number of flowering plants was placed at a
little more than 100,000, while now it is about 133,000:
then the lower plants (''cryptogams") were thought to
number from 25,000 to 40,000, while now there are
more than 100,000 enumerated.

^\^^<

iv PREFACE

Another indication of the change that has taken place
in the science is suggested by the fact that then the
Plant Kingdom was divided into the ''Phaenogams"
and ''Cryptogams," and that the usual sequence of the
study was first proper "Botany" as a course in the
structure, reproduction and classification of the " Phaeno-
gams," with a possible Anhang of " Cryptogamic Botany"
for such students as wished to invade this mysterious
realm. How completely this has given way to a more
scientific conception of the Plant Kingdom is shown by
the practical disappearance of these terms from botanical
literature and their relegation to more or less popular
usage.

Again, it was formerly the very general practice of
teachers to present the subject of plant study beginning
with the higher plants, and indeed devoting the far
greater time to them, so that the sequence was from the
higher to the lower forms. However, with the more
complete acceptance of the doctrine of evolution the
opposite sequence from the lower forms to the higher
has become the general rule, since it permits greater
emphasis to be placed upon the progressive structural
changes by which higher organisms have been evolved
from lower.

In the earlier period there was not yet a general agree-
ment as to the nature of the fungi, and their relationship
to the algae. They were treated for the most part as a
group of quite isolated plants with only obscure if any
relationship with other groups. They were contrasted
Avith other groups, little attempt being made to empha-
size similarities in structure, or to suggest possible genetic
relationships. Today, on the contrary, we constantly
suggest to the students the probabilities as to the origin
of each group of fungi.

PREFACE V

In like manner the older botanists of today remember
the incoming of the belief in the heteroecism of rusts,
and how timorously the fact was accepted by teachers
of good standing among botanists. And this hesitancy
as to the acceptance of a new view was still more marked
in regard to the nature of '^ lichens," which by tradition
formerly constituted a third group in the triumvirate of
the lower plants. Algae, Fungi and Lichens — the ''thal-
logens" of that day. Happily we have outlived this
provincial timidity in regard to the starthng conclusions
of the German botanists, and in recent years have calmly
accepted the substitution of a radically different system
of the flowering plants for that which had generally pre-
vailed for seventy-five j^ears or more. Many of us still
remember that the Gymnosperms used to be regarded
as a division of the Dicotyledons, being sandwiched be-
tween the Monocotyledons and the Angiospermous
Dicotyledons. Now the Gymnosperms are regarded as
belonging to a genetic line different from the Angio-
sperms, although still associated with them as "seed
plants."

It will be noticed that this book follows the usual
German sequence of Morphology first, followed later by
Physiology. The experience of the authors leads them
to think that it is better to give the student a good
foundation in plant structure and then to have him study
the plant in action. However, this does not require the
teacher to defer all physiological topics until the com-
pletion of Chapters I, II and III; indeed it has been our
practice to introduce such topics as soon as the student is
prepared to master them.

In the systematic chapters (VII to XX) and especially
in Chapter XXII the Plant Kingdom is divided into four-
teen groups of primary ranlv, here called ''phyla." To

vi PREFACE

some teachers this may seem to be an unnecessarily
large number of primary groups, especially to those who
have been in the habit of dividing plants into Thallo-
phytes, Bryophytes, Pteridophytes and Spermatophytes,
but we may remind all such that Engler in the seventh
edition of his ''Syllabus der Pflanzenfamilien" divides
the thallophytic plants into eight primary groups, instead
of seven, as is done in this book. On the other hand the
Bryophytes, Pteridophytes, Calamites, and Lycopods
are brought into one primary division by Engler, and the
Cycads, Conifers and Flowering Plants into another.
We are assured that the phyla here recognized are natural
groups, and while they are by no means equally separated
from one another, they are easily distinguishable. This
is no less true for the phyla below the Bryophytes than
it is for those including and above this group. We
feel that the Calamites and Lycopods are entitled to
first rank independently of the Pteridophytes, and that
the latter and the Bryophytes are very certainly to be
treated as genetically separate phyla. In hke manner
it seems to us that genetically the Cycads and Conifers
are so remote from the Flowering Plants that they can
no longer be placed in the same phylum, and that they
differ so much from one another that they must be
separated.

Thirty-five years ago the treatment here given the
" hchens" would have called for explanation and defense;
now we are so familiar with their structure that the sug-
gestion that they were the first of the higher fungi will
cause little surprise. So, too, there is less need now than
formerly to defend the treatment of the Rust Fungi,
as to whose general relationship there is less and less dis-
agreement. With the growing acceptance of the struc-
tural homology of ascus and basidium in the higher

PREFACE vii

fungi, it now signifies less than formerly whether the
Rusts are regarded as related to the Ascus Fungi or the
Basidium Fungi. As will be seen in Chapter XIII we
still hold to the theory that their relationship is some-
what closer to the former than the latter.

For many years it has been evident to us that the
apocarpous Flowering Plants must be regarded as primi-
tive and that from these the syncarpous forms arose.
Moreover the apopetalous preceded the apetalous
flowers, the latter being derived from the former by a
simplification of the flower structure. The flowers of
willows, oaks, elms, nettles, etc., are quite simple, but
they are not primitively so: they have been simplified
from more complex structures, and are to be associated
with the latter, rather than given place near the beginning
of the phylum.

The diagrammatic illustrations used in this book are
similar to those used on our lecture room blackboards.
We have felt that in a textbook involving laboratory work
elaborate drawings were unnecessary and often subject
to grave abuse.

It is scarcely necessary to-day to insist that this book
requires a botanical laboratory; nor is it necessary to
give ''forms" to be followed by the student in his labora-
tory work; for it may be assumed that no one will attempt
to use this book who has not himself received training in
a good laboratory. We have purposely suggested many
more laboratory exercises than can be performed by the
ordinary student, affording the teacher a large Hst from
which he may make his own selection. A few suggestions
here as to this laboratory work may not be out of place,
as follows: (1) Have each pupil prepare his own speci-
mens, as far as possible; only in a few special cases should
he make use of specimens prepared by some one else.

viii PREFACE

(2) Require simple, accurate drawings of the essential

features of each specimen. (3) Label the different parts

of the drawings, upon the sheet. (4) Do not require long

descriptions of the specimens studied, for the student

needs more to see and study plants than to attempt to

^vrite about them. (5) Do not ask for ''conclusions,"

for the student has not yet enough knowledge of plants

to make generalizations. (G) The exact name of the

plant, or part of plant studied should be written upon

the sheet of drawings.

It remains only for us to say that while the junior

author originally prepared Chapters I to V, and the senior

author the remainder, all have been gone over again and

again by both of us so that we are both responsible for

what is here set forth. We hope that this presentation

that has approved itself to us in our classrooms and

laboratories may be equally helpful in those of other

teachers of Botany in the Colleges and other high

schools of the country.

The Authors.
May, 1914

CONTENTS

CHAPTER I

Protoplasm and Plant Cells (Cytology)

Page
Protoplasm. The Plant Cell. Coenocytes. Plastids. Cell
Inclusions. Cell Sap. Formation of New Cells.
Mitosis (Karyokinesis) 1

CHAPTER II

The Tissues of Plants (Histology)

Aggregations of Cells. Differentiation of Cells. Meristem.
Parenchyma. Sclerenchyma. Collenchyma. Fibrous
Tissue. Conductive Tissues. Tracheary Tissue. Sieve
Tissue. Laticiferous Tissue 27

CHAPTER III

Groups of Tissues, or Tissue Systems (Histology)

In Lower Plants. In Higher Plants. Apical Cells, Der-
matogen. Periblem. Plerome. Three Tissue Systems.
Epidermal System; Epidermis; Hairs; Stomata. Con-
ducting System; Vascular Bundles; Radial Bundles;
Concentric Bundles; Collateral Bundles; Closed Bundles;
Open Bundles. Secondary Thickening. Supporting
System; Collenchyma Strands; Fibrous Strands. Pali-
sade Parenchyma. "Sponge" Parenchyma. Storage
Parenchyma. Cork. Lenticels 43

CHAPTER IV

Plant Physiology

Nutrition; Water; Imbibition; Osmosis; Turgor; Path of the
Water; Evaporation of Water; Root Pressure; Solutions;
ix

X CONTENTS

Page
Mineral Nutrients; Photosynthesis; Carbohydrates; Pro-
teins; Root Nodules; Hysterophytic Plants; Respiration;
Anaerobic and Aerobic Respiration; Fermentation; Tem-
perature Relations; Effect of Poisons. Growth; Relation
to Nutrition, Temperature,Light. Reproduction; Asexual,
and Sexual; Behavior of Chromosomes, Diploid and Hai>
loid Number; Inheritance; Mendelism; Natural Selec-
tion; Survival of the Fittest; Variations; Mutations;
Evolution; Phylogeny; Plant Breeding. Movements;
Hygroscopic Movements; Protoplasmic Movements;
Turgor Movements; Growth Movements, Nutation,
Tropisms, Phototropism, Geotropism, Thigmotropism,
Chemotropism, Hydrotropism. Pathology; "Physiolog-
ical Diseases;" Diseases due to Parasites 71

CHAPTER V

The Chemistry of the Plant

Inorganic Acids and Salts. Organic Acids. Alcohols. Fats
and Fatty Oils. Aromatic Oils and Camphors. Carbo-
hydrates; Monosaccharids; Disaccharids; Trisaccharids ;
Tetrasaccharids; Polysaccharids. Glucosides. Alkaloids.
Protein Group. Enzymes. Miscellaneous Substances . 139

CHAPTER VI

The Classification of Plants

Number of Species. Relationship. Species and Genera.
Higher Groups; Families; Orders; Classes; Phyla. Evo-
lution. Origin of Phyla. The Place of Plants in Time.
Table of Geologic Time Divisions l.")7

CHAPTER VII

Phylum I. Myxophyceae: Slime Algae

General Characters. Two Classes. Blue Greens; Unicellular;

Filamentous. Bacteria. Higher Blue Greens .... 163

CONTENTS xi

CHAPTER VIll
Phylum II. CHLOROPHYfEAE: Simple Algae

Page
CJeneral Characters. Two Classes. Green Slimes; Palinel-
lales; Coenohiales. Confervas; Ulothrix; Oedop;oniiun;
Disk Algae 170

CILVPTER IX

Phylum III. Zygophyceae: Conjugate Algae

General Characters. Two Classes. Pond Scums; Desmids.

Diatoms. Origin of ZygophA^ceae 177

CHAPTER X

Phylum IV. Siphonophyceae: Tube Algae

General Characters. Lower Tube Algae; Water Flannel;
Green Felts. Tube Fungi; Water Molds; Downy Mil-
dews; Black Molds; Insect Fungi. Higher Tube Algae;
Bladder Algae; Sea Ferns; Sea Umbrellas; Stoneworts.
Summary 184

CHAPTER XI

Phylum V. Phaeophyceae: Brown Algae

General Characters. Origin. Ectocarpus. Kelps. Rock-
weeds. Gulfweeds 199

CHAPTER XII

Phylum VI. Rhodophyceae: Red Algae

General Characters. Cell-walls. Color. Reproduction.
"Laver." Nemalion. Corallina. Polysiphonia. "Irish
Moss" 205

xii CONTENTS

CHAPTER XIII
Phylum VII. Carpomyceteae: Higher Fungi

Page
General Characters. Reproduction. Three Classes. Asciis
Fungi; Disk Lichens; Cup Fungi; Morels; Slit-Fungi;
Closed Fungi; Mildews; Yeast-plants; Truffles. Basid-
ium Fungi; False Tubers; Puff-balls; Bird-nest Fungi;
Stink-horns; Toadstools. Brand Fungi; Rusts, Heter-
oecism, Wheat Rust, Sexual Reproduction; Smuts, Corn
Smut, Wheat Smut, Bunt. Imperfect Fungi; Spot-
Fungi; Black-dot Fungi; Molds 211

CHAPTER XIV

Phylum VIII. Bryophyta: Mossworts

General Characters. Life Cycle. Two Classes. Liverworts;
Riccia; Hornworts; Great Liverwort; Scale-Mosses.
Mosses; Reproduction; Protonema; Black Mosses; Peat
Mosses; True Mosses 242

CHAPTER XV

Phylum IX. Pteridophyta: Ferns

General Characters. Life Cycle. Two classes. Old-fash-
ioned Ferns; Adder Tongues; Marattias; Quillworts.
Modern Ferns; Land Ferns; Water Ferns 254

CHAPTER XVI

Phylum X. Calamophyta: Cal.\mites

General Characters. Wedge-leaved Calamites. Horsetails.
Old Calamites 261

CHAPTER XVII
Phylum XI. Lepidophyta: Lycopods

General Characters. Two Classes. Lower Lycopods; Ground

Pines. Club Mosses; Selaginellas; Lepidodendrids . . . 266

CONTENTS xiii

CHAPTER XVIII

Phylum XII. Cycadophyta: Cycads

Page
General Characters. '\Seed-ferns." Common Cycads.
" Flowering Plant Ancestors." Conifer Ancestors.
Maidenhair Trees. Joint-firs 271

CHAPTER XIX

Phylum XIII. Strobilophyta: Conifers

General Characters. Taxodiums. Old Pines. Modern Pines,

Genera of Modern Pines. Cypresses. Junipers. Yews. 277

CHAPTER XX

Phylum XIV. Anthophyta: Flowering Plants

General Characters. Typical Flower; Buttercup; Water
Plantain; Strawberry. Two Classes. Monocotyledons;
Lilies; Calla Lilies; Palms; Grasses; Amaryllises; Orchids.
Dicotyledons; Axis Flowers, Magnolia, Mallow, Gera-
nium, Violet, Mustard, Pink, Primrose, Phlox, Petunia,
Snapdragon, Sage; Cup Flowers, Spiraea, Rose, Apple,
Plum, Pea, Currant, Evening Primrose, Prickly Pear,
Walnut, Oak, Parsnip, Honeysuckle, Sunflower, Dande-
lion. Summary of Anthophyta; Evolution; Progressive
Development through the Phyla 284

CHAPTER XXI

Some Special Adaptations

Plant Body; Thorns; Storage Organs; Mesophytes; Xero-
phytes; Hydrophytes; Parasites. The Flower; Anemo-
pliilous; Entomophilous; Colors and Odors; Nectar;
Actinomorphic; Zygomorphic; Proterogynous ; Protcran-
drous;. Dimorphic; Parthenogenesis. Seed Distribution. 319

XIV CONTENTS

CHAPTER XXH
The Plant Phyla

Page
Number of Classes, Orders, Families, and Species. Key to the
Phyla. Systematic Arrangement of the Fourteen Plant
Phyla 327

Ini>ex 381

N. Q. COLLEGE OF A, & M. A.

ESSENTIALS OF COLLEGE
BOTANY

CHAPTER I

PROTOPLASM AND PLANT CELLS
CYTOLOGY

1. Protoplasm. Plants, like animals, possess as their
living portion a soft, viscid, more or less granular sub-
stance called protoplasm. This living matter makes up,
ordinarily, only a rather small proportion of the total
substance of the larger plants, being present in larger
proportion in the smaller, simpler organisms. In the
rapidly growing parts of plants it is far more abundant
than in the fully developed organs.

2. Protoplasm, when studied under high magnifica-
tions with the use of certain stains, is found not to be a
homogeneous substance but to occur in various forms
as follows: (1) Cytoplasm. This is the bulk of the pro-
toplasm and that which probably performs most of its
ordinary functions. It is less dense than the other forms,
being often of about the consistency of the white of an
egg. It appears to consist of a clear, more or less liquid
portion in which are imbedded innumerable granules of
all sizes, from those easily visible under moderately high
magnification to those barely visible at the highest possi-
ble magnification. (2) Nucleus. This is a somewhat
denser portion of the protoplasm, usually of definite

ntOPERTY LIBRARY

N. C. State College

2 PROTOPLAS:\I AND PLANT CELLS

shape (mostly rounded) and separated from the cyto-
pkism by a delicate membrane. Like the cytoplasm, the
bulk of the nucleus seems to be a colorless fluid in which
is found a network of fine threads (the linin network)
on which occur more or less numerous coarser or finer
granules of chromatin. A rounded, usually nearly homo-
geneous body, the nucleolus, is mostly visible as a small,
highly refractive drop within the nucleus. (3) Centro-
some. Although of general occurrence
throughout the animal kingdom centro-
somes are definitely known only in certain
of the lower plants. In a cell not in divi-
sion the centrosome appears as a minute
piaim enclosed by body lYi closc proximity to the nucleus. It

a cell wall. ,i ,• ■• i ,...

takes an active part m nuclear division in
animals, and possibly may do so in those plants in
which it is present. (4) Plastids. These consist of
denser masses of protoplasm lying in the cytoplasm
and are colorless (leucoplasts) or colored (chloroplasts
and chromoplasts). They are lacking in the cells of
many plants.

3. All these forms of protoplasm possess many char-
acteristics in common, both as to physical and chemical
structure. They are very complex compounds with
most of the characteristics belonging to the proteins but
differing from them in some important points. Proto-
plasms consist mainly of carbon, hydrogen, oxygen, nitro-
gen and sulphur and of phosphorus also in the case of
the nucleus. In all probability certain metallic elements
also enter into the combination.

4. The most remarkable property of protoplasm and
that which distinguishes it from all other chemical sub-
stances is its power of manufacturing new protoplasm
out of simpler substances, in other words, the power of

PROPERTIES OF PROTOPLASM 3

growth and reproduction. In addition, protoplasm pos-
sesses in great degree the power of movement as well as
of perception. Motion is not always evident but in cer-
tain stages at least it can almost always be found. The
protoplasm may move as a whole or certain portions of
the cytoplasm may stream to and fro in a most compli-
cated manner. Such streaming may affect only the small
granules, or the larger bodies such as nucleus and plastids
may be transported from one place to another.

5. Protoplasm possesses the power of imbibition of
water. It may imbibe so much water that it becomes
very thin and watery and yet still retain its powers of
motion and of reproduction. There is a limit, however,
to the amount of water protoplasm will imbibe, for some
of the naked masses of protoplasm set free by some
plants for reproductive purposes retain their shape and
size in spite of being immersed in water.

6. The complex chemical and physical structure of
protoplasm renders it very susceptible to injur}'-. This
injury may be simply physical, or certain of the groups
of atoms making up the complex protoplasmic molecule
may be changed chemically in such a way that the proper
functions can not be carried on. When the changes reach
such a point that on removal of these external unfavorable
conditions the protoplasm does not resume its functions,
we say that death has occurred. Heat, cold, electricity,
even light, also mechanical injury such as crushing, as
well as innumerable chemicals will cause death. Many
of these agents when applied in smaller amounts or to
a lesser degree check the functions of protoplasm only
temporarily. Thus a jar or sudden cooling will check
for a time the streaming within the protoplasm.

7. All of the modifications of protoplasm are, at least
when active, in a more or less liquid state. The two

4 PROTOPLASM AND PLANT CELLS

theories as to its physical structure that receive the
strongest support are the emulsion and the fibrillar
theories respectively. By the first theory protoplasm
is a very complex emulsion of various substances more
or less closely related chemically. The bodies appear-
ing as granules would be then, in part at least, small
drops suspended in the emulsion. These drops are
perhaps themselves also emulsions. The fine lines visi-
ble under certain conditions would be not fine strands
but rather the edges of surfaces separating adjacent
units of the emulsion. It is readily seen that this theory
would accord well with the observed fact of the great
power of imbibition of water by the protoplasm, for this
would but separate the droplets of the emulsion some-
what more without necessarily disturbing their relative
positions. The viscidity or relative firmness of some pro-
toplasm (e.g. plastids and nucleus) is in agreement with
what we know about emulsions. Thus two thin liquids
may sometimes be brought to such a state of emulsion
that the whole mass is firm and will stand upright. The
fibrillar theory supposes that the delicate lines mentioned
above are fine threads, connected at innumerable points
and traversing the clear liquid making up the bulk of the
protoplasm. The granules are looked upon as being
situated on these fibrillac or sometimes in the spaces
between them.

8. The Plant Cell. In all plants we find that the
protoplasm occurs in definite units which are independ-
ent or more or less connected with neighboring units; in
the latter case the whole mass of these units constitutes
the plant. These units are called cells and consist
always of at least two parts, a mass of cytoplasm and a
nucleus. In most plant cells the protoplasm deposits a
firmer substance as a box-like covering called the cell wall,

CELL WALL 5

which gives firmness to the cell and acts as a protection
to it. Plastids are very frequent constituents of cells
although large groups of the lower plants, the so-called
fungi, lack them entirely. Most cells contain spaces
within the cytoplasm filled with watery solutions. These
are called vacuoles, and the contained solutions are
known as cell sap. At its outer surface as well as at the
surfaces in contact with the larger vacuoles and the
nucleus the cytoplasm forms a denser layer, free from
granules, which holds the cytoplasm in shape, prevents
passage of certain substances into or out of the cyto-
plasm, etc. This is the plasma membrane. The plasma
membrane about the nucleus is usually, however, called
the nuclear membrane. The layer next to the vacuoles
is frequently spoken of as the tonoplast.

9. The cell wall consists usually of cellulose or related
substances, i.e. of some of the more complex carbohy-
drates. These are composed of carbon, hydrogen and
oxygen in the proportion, usually, of six parts of carbon,
ten of hydrogen and five of oxygen. In many of the
fungi and some other plants the cell wall is composed of
a form of chitin, containing nitrogen in addition to the
substances mentioned. This has been called fungus
cellulose, although not related to cellulose chemically.
In the walls of older cells there are frequently deposited
various other substances such as silica in the diatoms
and in the epidermal cells of joint rushes and grasses,
suberin and cutin in the walls of cork and epidermal cells,
respectively, hadromal, or perhaps vanillin and conif-
erin in wood cells, etc., these being in part the so-called
''Ugnin" of earlier botanical works. Aside from cellu-
lose the chief constituent of cell walls is pectose, chemi-
cally very similar to it and frequently mixed with it.
Under the influence of certain not well understood

6 PROTOPLASM AND PLANT CELLS

conditions the cellulose or pectose may become changed
into gums, e.g. gum arable, cherry gum, slime of flax-
seed, etc.

10. The cell wall when first formed is very thin.
Growth occurs either by apposition (deposition of cell
wall substance on the inner surface of the wall) in which
case the wall becomes thicker and may or may not
appear layered, or by intussusception (the deposition of
new material among the particles of the old), in which
case the wall becomes larger as well as often thicker.
The first laj^er formed is the thin middle lamella. Upon
this is deposited, on either side, a thicker layer of some-
what different composition, the secondary lamella. A
tertiary lamella is sometimes formed also. These
different layers are usually of somewhat different chemi-
cal composition. Thus the middle lamella is often com-
posed of calcium pectate or some other pectose compound
while the secondary lamellae are cellulose or a mixture
of cellulose with other substances. When present, the
tertiary lamella is usually nearly pure cellulose.

11. The walls between adjacent living cells are quite
generally perforated by very minute pores through which
delicate fibrils of cytoplasm extend from one cell to the

other, apparently thus binding all the
living cells of the plant together into one
more or less coordinated unit.

12. The thickening of the cell wall is
not always uniform. Indeed, except in
Fig. 2.— Thick- Comparatively thin-walled cells thinner
areas or spots are almost always left be
tween the more thickened parts. These thickenings may
be ridges which are in the shape of rings, spirals or reticu-
lations or may occupy so much of the surface that the
unthickened parts appear as pits. Usually these thick-

CHARACTERISTICS OF CELLS 7

enings are on the inner surface of the cell wall, but in
many spores (e.g. pollen grains or spores of ferns or fungi)
they are external. This is also the case in some of
the lower, one-celled plants such as desmids. The
thickenings have various functions, such as strengthen-
ing the wall, providing means for transportation (in the
case of spores and pollen grains which sometimes depend
upon animals for their dispersal, the rough projections
enabling them to cling to the animal), etc.

13. After attaining their full differentiation most of
the cells of the higher plants (at least of the woody
plants) die, their cell walls remaining to make up the
bulk of the plant body. We usually continue to speak
of such dead, empty cell walls as cells, although the
essential parts, the cytoplasm and nucleus, may have
disappeared long ago.

14. Cells vary greatly in size, those of some of the
bacteria being less than half a micron (i.e. less than one-
fifty-thousandth of an inch) in diameter, wdiile the egg
cell of Zamia may have a thickness of over a millimeter
and a length of 3 mm. (i.e. a volume over twenty billion
times as great), the egg cell of Dioon being even larger.
Some fiber cells have a length of many centimeters, e.g.
bast fibers of ramie {Boehmeria nivea).

15. In some of the lower aquatic plants occur repro-
ductive cells with no cell walls (e.g. zoospores, tetra-
spores, etc.). These cells are frequently motile by means
of protoplasmic processes called cilia or flagella. Such
cells in many cases settle down and, becoming attached
to something, form a cell wall before proceeding further
in their development. Even in the higher plants the egg
and sperm cells are naked.

16. Typical cells have but a single nucleus. In certain
stages of the life history of some groups of plants the

8 protoplas:m and plant cells

cells are binucleate while they are uninucleate in the
remaining stages. In some groups of plants, however,
we find that, enclosed in an outer cell wall, there is a
mass of cytoplasm containing many nuclei. Such a
structure is called a coenocyte. It is frequently re-
garded as consisting of as many cells as nuclei are present,
not separated, however, by partition w^alls. Perhaps it
may better be considered as a sort of compound cell as
the nuclei do not seem to control definite masses of cy-
toplasm. In some coenocytes of the seaweed Griffithsia
over 4,000 nuclei are present, while in the enormous
coenocyte of Caulerpa, likewise a seaweed, which often
attains a length of several decimeters, the number of
nuclei is vastly greater. Coenocytes are mostly re-
stricted to certain groups of lower plants, but cells of
coenocytic nature may occur even in the higher plants.

17. In shape cells are very variable. Usually we find
that free-living cells approach the spherical shape al-
though they are often elongated somewhat. Cells
united to other cells are usually flattened on the sides
where they are in contact. When surrounded by cells
at all sides cells are usually more or less regular, several
to many-sided polyhedra. Some cells are cylindrical
while often we have fiber or spindle shaped cells. Some
cells are lobed or branched.

Laboratory Studies. It is assumed that the attempt will
not be made to use this book without endeavoring to carry
out in the laboratory all or at least a selection of the laboratory
exercises suggested here and there in connection with the
various topics. So far as possible the suggested exercises
have been made simple enough for the student to undertake
himself, depending as little as possible upon specimens prepared
or experiments set up by the teacher. It is absolutely essential
that each student have the use of a good compound micro-
scope, and that he possess the proper tools for making sections,

LABORjVTORY STUDIES 9

etc., as well as a few siini)le reagents such as alcohol, iodinc-
potassium-iodide solution, potash solution, etc. The measure-
ments used throughout this book arc metric; 1 cm. = 0.394 in.
1 mm. = about 1/25 inch, 1 micron (written At)= 0.001 mm.
(i.e. about one-twcnt3''-five-thousandth of an inch).

(a) ]\Iake a thin longitudinal section of the tip of a large
root of Indian corn or hyacinth or any other plant with stout
roots, or of the growing point of a herbaceous stem, and
mount in water and examine under the microscope. The
small cells near the tip will be found to be full of protoplasm.
The following tests should be made on different sections: (1)
Add strong iodine solution; this turns the protoplasm brown
or yellowish brown. (2) Test with a drop or two of Millon's
reagent (dissolve a small amount of mercury in an equal weight
of strong nitric acid, and dilute with an equal amount of
distilled water. Use fresh): the protoplasm is turned bright
yellow. (3) Mount a section in strong sugar solution and
after a few moments add a drop of fairly strong sulphuric
acid: the protoplasm is stained red or pink. (4) Treat a
section with nitric acid and then with strong potash: the yellow
color of the protoplasm shows the so-called xanthoprotein
reaction.

(6) Repeat these tests with raw white of egg, which consists
of proteins. Note that the results are the same. For the
sulphuric-acid-sugar test it is more satisfactory to mix the egg
white with a strong sugar solution in a test tube, rolhng the
latter so that the sides are moistened with the mixture. Now
very carefully run a small drop of concentrated sul])huric acid
down the side of the tube. This browns the solution where
it comes in contact in most concentrated form but at the edge
of its path and at its point of entrance into the mixture tlie
red coloration is shown beautifull}^

(c) To study the motion of cytoplasm make a cross or
longitudinal section of a stem (the upper, younger portion) of
Petunia or tomato without injuring the hairs. JMount in
water and examine a cell of a hair. The cytoplasm will
usually be found to be streaming. Note that the streams seem
frequently to center upon the nucleus. Note the effect upon
the motion of placing the slide on a jiiece of ice. Warm it up
again to a temperature of about 30° to 35° C. and note the

10 PROTOPLASM AND PLANT CELLS

results. Heat to 55° to 60° C. Now cool to about 30°.
Examine again.

{(I) On similar specimens test the effect upon motion of
iodine solution, alcohol, glycerine, etc.

(e) Various types of proto])lasmic motion may be found in
the long cells of the young silk of Indian corn, in the cells of
the leaves of water weed (Philotria), the cells, especially those
near the ends of the shoots, of Chara or Nitella, etc.

(/) To observe the different parts of a cell study again the
stem hairs of Petunia. Note nucleus, nucleolus cytoplasm,
vacuoles, cell wall. Cells from the leaf of a moss may also be
used for this purpose.

(g) Bring into the laboratory some growing LTlothrix,
Cladophora, Stigeoclonium or other zoospore-producing algae,
and place in fresh water near the window. In a few hours one
can often find myriads of zoospores. Examine these for cells
lacking walls and provided with motile organs (flagella).

(h) Make a thin cross-section of a herbaceous stem. Treat
with iodine solution and then with somewhat diluted sulphuric
acid. Cellulose walls are turned blue, cutinized and lignificd
(wood) walls, yellowish brown. Stain another section with
anilin-water safranin. This stains cutin walls yellowish and
lignin walls bluish.

(i) Examine a thread of green felt (Vaucheria) or a vegeta-
tive thread of bread mold (Mucor) for a plant of coenocytic
structure. Note the lack of cross walls. The numerous
minute nuclei are not visible without staining.

ij) The stone cells making up the shells of various nuts are
good objects to show the deposition of the cell wall in layers,
i.e. by apposition. With a pocket knife cut as thin a section as
possible, and place it in water containing a httle potash. At
the edges may be found areas thin enough for examination.
Here and there in the plainly layered cell wall will be found
pits, i.e. thin places left when the rest of the wall thickened.

18. Plastids. Three kinds of plastids occur in plants.
They all agree in general structure in that they are denser
bodies of protoplasm imbedded in the cytoplasm. They
may have many shapes but are more frequently round or
elliptical in outline. So far as is certainly known new

PLASTID8 11

plastids are formed only from the division of old plastids
into two parts. They are difficultly visible in some plant
cells, e.g. in the small rapidly dividing meristem cells at
the growing points of a plant, and are entirely lacking in
some great groups of plants, viz. the bacteria and fungi.
19. Chloroplasts are plastids containing chlorophyll.
Ordinarily they are green, from the color of the chloro-
phyll itself, but in some groups of plants the green color
is masked by the presence of other pigments in the chloro-
plasts in addition to the chlorophyll. Thus
in the Red Seaweeds (Rhodophyceae) the
chloroplasts are usually red, in the Brown
Algae (Phaeophyceae) they are brown, in
some ]\Iyxophyceae the chloroplasts are
bluish green, etc. Chlorophyll proper is
a bluish green, apparently somewhat oily p^^ 3— piistida
substance, probably contained in inter- (cMoropiasts) in a
stices of the chloroplast. It is soluble
in alcohol, by means of which it can be removed, leav-
ing the chloroplast colorless. In addition to chlorophjdl
most chloroplasts contain an orange yellow pigment, to
which the name xanthophjdl is often applied. It ap-
pears to be a form of carotin. The mixture of these
two gives the grass-green color to the chloroplast. With
rare exceptions chlorophyll is not produced in the ab-
sence of light. It usually disappears in prolonged dark-
ness, leaving the chloroplast stained yellow with xantho-
phyll or colorless. In many of the lower plants the
chloroplasts are of various shapes, often being star-,
band-, plate-, or even net-shaped. In the higher plants
they are mostly more or less disk shaped. In some of
the liverworts and many of the algae they contain one
or more highly refractive bodies, called pyrenoids, which
are probably crystals of some albuminous substance.

12 PROTOPLAS:\r AND PLANT CELLS

20. Leucoplasts are colorless plastids occurring in the
parts of the plant not exposed to light. When exposed
to light they usually produce chlorophyll and become
green, showing that they are essentially the same as the
chloroplasts. They are abundant in parts of the plant
where starch is being stored up.

21. Chromoplasts are found in the cells of many
flowers and fruits and other colored parts of plants.
They are small, round or angular or needle shaped
plastids, mostly red or yellow in color. They contain
carotin or other coloring matters but no chlorophyll.
In many cases they are directly developed from chloro-
plasts by the loss of chlorophyll and the development of
some other pigment.

Laboratory Studies. — (a) Mount a leaf of moss and examine
for chloro})Iasts.

(6) Soak a few moss leaves in strong alcohol for twenty-four
hours and note the decoloration of the chloroplasts.

(^/) Soak a handful of leaves in alcohol for several hours. If
the flask containing the alcohol and leaves be placed in hot
water the extraction of the chlorophyll will progress more
rapidly. Note the green color of the extract. Add a little
gasoline or benzine (not benzene, i.e. benzol) to the alcoholic
solution and shake thoroughly and then let it stand until the
alcohol and gasoline separate. The chlorophyll will be found
now in the gasoline, the carotin remaining in the alcohol.

(e) Examine the cells of various fungi, e.g. toadstools,
puf'fballs, molds, etc., or of a parasitic flowering plant, e.g.
dodder (Cuscuta), and note the absence of chloroplasts.

(/) Sprout a potato in darkness. Make a section of its stem
and compare with a similar section of the stem of a potato
grown in light. Note the leucoplasts in the former and the
chloroplasts in the latter. Similarly compare the stomatal
guard cells of the epidermis of green and l)lanched celery.

{g) Examine the cells of a carrot root for chromoplasts

CELL INCLUSIONS

stained with carotin. Examine also the red cells of a ripe
tomato or the yellow cells of a petal of nasturtium (Tropaeo-
lum) or the cells of rose hips.

22. Cell Inclusions. Within many cells are often
found bodies not living and not an essential part of the
cell but which have been produced by the cell itself.
They may be temporary or permanent. They may lie
in the cytoplasm, in the vacuoles or in the plastids.
Such bodies are called cell inclusions. The most fre-
quent cell inclusions are starch, aleuron, crystals and
sometimes drops of fat or oil.

23. Starch. In the green cells of many plants there
are produced in the chloroplasts on exposure to light
small pearly white grains of starch.

These are usually transformed into
sugar during the night and used by the
plant for food or transported to some
other part such as root, tuber or seed,
where the sugar may be again con-
verted to starch, in the leucoplasts, to

Fig

Starch

remain until needed by the plant for f /eC/onUlmiif.' ^ ^"'^
food. Whereas in the green cells of
a leaf the starch does not ordinarilj^ accumulate in great
quantities, the storage cells of a plant become so packed
with it sometimes that little else can be seen.

Starch is a carbohj^drate and is closely related chemi-
cally to cellulose and to the sugars. It is composed of
carbon, hydrogen and oxygen in the proportions indi-
cated by the formula (C6Hio05)n, in which ''n" is a
fairly high Init not exactly ascertained amount. By the
action of certain organic substances produced by the cell
and called enzymes, or of some of the acids and heat, it
can l)e converted into some forms of sugar.

Starch grains frequently show a concentric structure,

14 PROTOPLASM AND PLANT CELLS

due apparently to the successive deposition of denser and
less dense la3'ers. At first the grains are entirely en-
closed by the plastid but as they increase in size they
become excentrically located and seem eventually to
burst out of the plastid at one side. In the chloroplasts
containing pyrenoids the starch grains are mostly pro-
duced in intimate connection with the latter.

24. Aleuron. In the dry seeds of many plants there
may be found, sometimes in a definite layer of cells,
sometimes scattered throughout the cells of the seed,
small rounded or frequently angular granules of a protein
substance called aleuron. This is stored up in the cells
as food for the young seedling. These aleuron grains are
formed in small vacuoles in the cytoplasm, the aleuron
being in solution at first but appearing as granules or
even crystalloids as the seed loses its moisture in the
process of ripening. As the seed absorbs water prepara-
tory to germinating the aleuron goes into solution again
and is used up for food. Aleuron is frequently found in
cells containing other stored up food matter such as
starch or oil. It was formerly supposed to be a dry
stage of protoplasm but is now recognized as one of the
highly complex food substances out of which protoplasm
can be formed by the cell.

25. Oils or Fats. Many plants provide for the use of
the young seedling a supply of fat instead of starch.
This is usually present in the cell as very minute drops,
in fact almost as an emulsion throughout the cytoplasm.
Sometimes the oil droplets are of considerable size, in
very oily seeds often filling all the interstices of the cyto-
plasm. Usually these fats are liquid but in some plants
they are semisolids of the consistency of butter. They
are mostly true fats, similar to those found in animals,

CRYSTALS 15

but in some plants cells are found which contain so-called
''ethereal oils," which are not true fats.

26. Crystals. In many plants may be found cells
containing crystals. These may be cubical, prismatic,
regular or irregular polyhedrons, needles, compound
crystals, etc. Sometimes the cells containing them are
unchanged but often they are enlarged or of special
shape. This is especially the case with the needle-
shaped crystals which are called raphids
and occur in large bundles in the cen-
tral vacuole of rather large, thin-walled
cells. The crystals seem to be formed
by the cytoplasm, in which they occa-
sionally lie, or more frequently in special
small vacuoles in the latter. Eventu- pound." and needTe^

,, , r 1 • , 'XT, shaped crystals.

ally they are found m most cases m the

central vacuole in which some of them may have had

their origin.

27. Crystals in most plants are composed of calcium
oxalate. In some plants calcium carbonate crystals
occur, while crystals of still different composition are
occasionally found. The purpose of crystals is not clear
in all cases but in many cases they are probably the
product of the combination of waste substances set free
in the course of some of the important chemical pro-
cesses of which the cell is constantly the seat.

Laboratory Studies, (a) Make a thin section of a potato
tuber. Mount in water. Note the large, thin-walled cells
packed with numerous ovoid, concentrically marked starch
grains. Treat with iodine solution. The starch grains become
blue or purple. In very young tubers, where the starch grains
are not so large nor so numerous, they may be seen to be
enclosed in leucoplasts.

(b) Study the different types of starch grains in corn, wheat,
rice, oats, etc.

16 PROTOPLASM AND PLAXT CELLS

(c) Place a dish of water containing Spirogyra in the light
for some hours and then examine a few filaments. In the
spirally wound chloroi)lasts, around the pyrenoids will be
found masses of starch which become more evident on staining
with iodine.

{(}) Make thin sections through various leaves that have been
exposed to the light for some time, staining with iodine. In
some of these minute grains of starch will be found in the
chloroplasts.

(e) Make longitudinal sections of ripened apple twigs, in the
fall or winter especially, and note the starch stored in the
rather thick-walled cells of the pith.

(/) IMount in strong alcohol or glycerine a thin section of a
pea or bean. In addition to starch grains the cells will be
found to contain very numerous fine granules. Stain with
iodine. These small aleuron granules will be stained brown
and the starch blue. To another section apply one of the
tests for proteins given on p. 9. Mount another section in
water and note the effect on the aleuron. Examine cotyle-
dons of germinated peas and beans for presence or absence of
aleuron.

(g) Examine a cross-section of a wlicat grain. The aleuron
will be found in a layer of cells outside of the starch-containing
cells. This laj^er is largely removed with the bran in the
process of making flour.

(h) Make a thin section of a seed of the castor oil plant
(Ricinus). Mount without adding water or any other
reagent. Large aleuron grains will be seen, each containing an
angular protein crystal and a spherical, so-called "globoid," of
inorganic nature. Add a little water and some of the oil will
escape and appear at the edges of the section as large drops.

(i) Examine various oily seeds such as cotton, flax, peanut,
or an oily fruit such as the avocado (Persea gratissima) or olive.
In the cells w^ill be found varying amounts of oil. By treating
the sections with 1 per cent, solution of osmic acid or with
alkannin solution the oil will be stained respectively black or
red.

(j) Make a thin longitudinal section of the stem of spider-
wort (Tradescantia) and mount in water. Certain thin-
walled cells will be found containing bundles of needle-shaped
crystals (raphids). Many of these will be torn out of position

CELL SAP

and scattered throup;liout the si)cciinen. These crj'stals are
composed of calcium oxalate. Add a little hydrochloric acid
and they will dissolve without effervescence.

(k) Similar crystals may be found in many other plants,
e.g. Lidian turnip (Arisaema), evening primrose (Oenothera),
fuchsia, garden balsam (Impatiens), garden rhulmrb, etc.

(/) For crystals of other types examine sections of prickly
pear (Opuntia), young basswood twigs, scales of onion, stem of
lamb's quarters (Chenopodium), petiole of beet, etc. These
are also composed of calcium oxalate.

(m) Examine a thin cross-section of the leaf of the rubber
plant (Ficus elastica). In some of the modified epidermal
cells will be found peculiar stalked crystalline bodies of calcium
carbonate deposited upon a cellulose core which hangs down
into the cell cavity from the outer jiortion of the cell wall.
Treat the section with, hydrochloric acid. The cystolith, as it
is called, dissolves with the evolution of CO2, leaving the cellu-
lose core, thus distinguishing it from calcium oxalate, which
dissolves without effervescence.

28. Cell Sap. The cytoplasm of a cell usually contains
a large amount of water imbibed by it but not really a
part of it. Water is also found fre-
quently in drops (vacuoles) within
the cell. This is the cell sap. It
holds in solution the various soluble
substances absorbed by the plant as
well as those manufactured by the
cell itself. It makes up by far the
greater part of the bulk of the contents
of the average cell. Among the sub-
stances dissolved in the cell sap, in
addition to the mineral matters absorl^ed by the plant
from the soil water, are many sorts of organic compounds
produced by the cytoplasm. The most important of
these are the various sugars and organic acids. The
commonest of the sugars are saccharose or cane sugar

-Large vacuoles.

18 PROTOPLAS:^! AND PLANT CELLS

(C12H22O11), glucose or grape sugar (C6H12O6), fructose
(CeHisOe), etc.

29. Cane sugar is found in great quantities in the cell
sap of the sugar cane, sugar beet, sugar maple, sorghum,
Indian corn and many other plants. The first two plants
produce the bulk of the sugar of commerce. In many-
fruits, such as grapes, cherries, gooseberries, figs, etc.,
glucose is present, while in still others, e.g. pineapple,
peach, plum, strawberries, etc., the two are mixed.
Fructose, as the name implies, is found in many fruits,
e.g. the grape. In many, if not in most plants glucose
seems to be the form in which green cells manufacture
their food, storing up the excess over immediate consump-
tion usually as starch, from which it is again obtained as
glucose. Inulin is found mostly in plants of the sunflower
family, e.g. sunflower (Helianthus), Dahlia, elecampane
(Inula), etc.

30. The organic acids found in the cell sap may occur
in acid form, but frequently are found as acid salts of
calcium or potassium or some other base. The most
common of these acids are maUc, citric, tartaric and ox-
alic. They seem to be present in some cases as food for
the plant while in others they doubtless help to keep the
cell turgid by raising the osmotic pressure within the cell
to the proper degree.

31. Among the substances found in the cell sap in so-
lution are certain compounds known as alkaloids. These
are perhaps in some cases products of the breaking down
of more complex substances and to be looked on as a sort
of excretion product comparable to urea in animals.
However, in certain plants they may serve as reserve
food as they are used up by the plant if no other food is
available. They are nitrogenous compounds of compli-

FORMATION OF NEW CELLS 19

cated composition, usually bitter to the taste and very
frequently poisonous to animals.

Laboratory Studies, (a) To show the large amount of
water in living cells place a few threads of pond-scum (Spiro-
gyra) in a little water and examine under the microscope.
Add a httle strong glycerine which has a great avidity for
water. Note how the cells collapse as the water is withdrawn.
Repeat the experiment with thin sections of some herbaceous
stem or simply allow the latter to dry out in the air.

(b) Taste the stem of sugar cane or growing Indian corn or a
piece of a sugar beet. The presence of sugar is readily recog-
nizable. Put small pieces of these plants into considerable
quantities of 95 per cent, alcohol to remove the water, or into
pure glj^cerine. The water is withdrawn rapidly by the
reagents and the cane sugar, which is practically insoluble in
them, crystallizes out in fine stellate crystals Sections for
examination must be mounted in the alcohol or glycerine as
water will redissolve the sugar.

(c) Make thin sections of the root of Dahlia or sunflower
(Helianthus) that has been preserved in strong alcohol and
note the large sphaerocrj'stals of inulin.

(d) To study glucose or fructose test the juices of various
fruits with Fehling's solution, which gives a precipitate of copper
oxide with both these sugars but not with cane sugar or inulin.

(e) The presence of acids or acid salts is readily discernible
by the taste in many plants, e.g. stem of rhubarb, leaves of
Oxalis, fruit of lemon, cranberry, etc. In smaller quantities
it can be demonstrated by placing the cut surface of the tissue
to be tested in contact with a piece of blue litmus paper which
will be turned red by the action of acids.

32. Formation of New Cells. No cell can originate
except from some pre-existing cell or cells. IMost cells
are capable of producing new cells at some stage of their
development, but frequently the power is soon lost.
New cells arise either through the division of a cell or
through the union of two (or rarely more) cells. In the
cell formation by division we distinguish two types, i>ac'h

PROTOPLASM AND PLANT CELLS

with modifications, \iz., fissioii, in which the cell divides
into two adjacent parts which may or may not remain at-
tached, and internal cell formation, in which the proto-
plasm within the cell divides into several cells which
eventually escape from the old cell wall as naked cells
(zoospores and motile gametes) or form new walls for
themselves within the old wall and bc^come free on the
rupture or decay of the old wall. The latter type in-
cludes cases in which all the protoplasm is used up in
forming the new cells, as in zoospore formation, as well
as those in which only a part is so used, the remainder

til:::.

Fig. 7. — Kuryokiucsis (mitosis).

lying between the new cells and the old wall, as in the
formation of ascospores within the ascus. Several forms
of fission may be distinguished. The commonest type
is that in which the protoplasm of the cell separates
into two parts that secrete a new wall between them,
the new cells thus remaining attached to each other.
The new separating wall may be formed as a ring-like
thickening on the old wall which gradually increases in

MITOSIS (KARYOKINESIS) 21

width until it has comi)h'ted the separation of the two
protopUismic masses, this being tlie commoner way in
the lower plants, or the wall may be produced sim-
ultaneously at all points at the plane of separation be-
tween the two protoplasts, as is the case in most higher
plants. In some of the lower plants the whole wall be-
gins to constrict at the middle, giving the appearance of
pinching the cell into two separate cells which are then
free from one another. A peculiar type of fission is that
termed budding, in which a small outgrowth appears at a
point on the cell, gradually enlarging until it is as large
as the old cell and then l^ecoming separated from it by
constriction of the wall at the point of emergence. This
is especially characteristic of, but not confined to, some of
the yeasts.

33. Cell division is in most cases initiated by, or more
or less immediately preceded by, the division of the
nucleus. In coenocytes, on the contrary, this connection
between nuclear division and that of the coenocyte seems
to be lacking. Two types of nuclear division may be
distinguished, direct or amitotic and indirect or mitotic.
The latter process is generally known as mitosis or karyo-
kinesis. The direct division is comparatively rare and
appears to consist of a simple pinching in two of the nu-
cleus. By far the commonest method is that of mitosis.
This is a very complicated process and is essentially as
follows, ])eing subject, however, to many more or less
pronounced variations in different plants. If a centro-
some is present, which is apparently the case only in some
of the lower plants, it divides into two centrosomes which
move around outside the nucleus until thej- lie at oppo-
site sides in a line at right angles to the plane of division.
The nuclear reticulum now begins to resolve itself into a
fine tangled thread without cross connections, the chro-

22 PROTOPLASJ^r AND PLANT CELLS

matin granules spreading themselves out along the thread
until it is of even thickness. The thread rapidly shortens
and thickens, eventually becoming a thick, more or less
distinctly spirally arranged thread (spirem stage). At
the same time the nucleolus has been growing smaller or
less distinct and soon disappears entirely. In the spirem
thread there often becomes visible at this stage a split for
its whole length. However, it does not separate along
this split as yet. In the mean time outside the nucleus
there begin to appear in the cytoplasm immediately
surrounding the centrosomes fine lines, or fibrillae (of
kinoplasm) , which appear to center at the centrosome and
extend from it in all directions but especially toward the
nucleus. In the plants which have no centrosomes there
appear near the poles of the nucleus tangled masses of
fine fibrillae which in some cases form a sort of cap at each
pole or even may entirely surround the nucleus. From
this tangled mass the fibrillae gradually untangle them-
selves somewhat and finally lie in the form of a cone at
each pole, with the apex away from the nucleus. In the
forms with centrosomes one of the latter lies at each apex,
often surrounded by radiating fibrillae which may reach
out even to the cell wall. Where the mass of fibrillae
comes in contact with the nucleus the nuclear membrane
disappears and soon after vanishes at all other points
also. The fibrillae push into the nuclear cavity. In the
meanwhile the spirem thread breaks transversely into a
number of segments called chromosomes, the number
being constant for all vegetative nuclei of a given species
of plant. Two sets of kinoplasmic fibrillae can now be
recognized. Some push through the nuclear cavity until
they meet and unite with similar ones from the other pole,
forming a spindle-shaped structure commonly spoken of
as the nuclear spindle. Other sets of fibrillae push toward

MITOSIS (KARYOKINESIS) 23

the chromosomes and become attached to them, one or
more sets from each pole being fastened to each chro-
mosome. In some way, perhaps by the contraction of
these fibrillae, the chromosomes are brought to he at the
equator of the spindle, forming the so-called equatorial
plate. The chromosomes are of various shapes, like rods,
or resembling the letters J, V or U, more frequently the
last two. Usually the faint longitudinal split which
first became visible during the spirem stage is quite dis-
tinct. As the fibrillae attached to the chromosomes con-
tinue to contract the latter are torn in two along the line
of this longitudinal split, one half being dragged toward
each pole. When these daughter chromosomes, as they
are called, reach the two poles they soon join to each other
end to end and form spirem threads similar to those
formed before the cleavage into chromosomes (the di-
spirem stage). These elongate and finally form a long
tangled thread along which the chromatin begins to
assemble in lumps and which soon forms short lateral
connections to make the typical nuclear reticulum. In
the meantime the nuclear membrane has appeared
around each daughter nucleus and the nucleolus has made
its appearance. The kinoplasmic fibrillae around the
centrosome gradually disappear in the plants with cen-
trosomes, while in plants without centrosomes they dis-
appear in about the same way that they appeared, or in
the higher plants take part in the formation of the sepa-
rating membrane. In this latter case the spindle fibrillae
seem to increase in number until they occupy the whole
width of the cell. At the equatorial plane a little knot
appears on each fibrilla. The fibrillae contract and as
they shorten the knots increase in size until by the con-
tact of the knots with each other a thin membrane (of
kinoplasm) is formed which separates the protoplasm of

24 PROTOPLASM AND PLANT CELLS

the coll into two parts. This membrane splits and be-
tween these two plasma membranes is secreted the first
layer of the cell wall (middle lamella). It is of interest
to note that mitotic nuclear division is essentially the
same in animals and plants. In the former, however,
centrosomes are usually present while they are lacking in
plants except in some of the lower groups.

34. In internal cell formation the nucleus usually
divides several times before the cytoplasm separates.
Usually the new cells are formed almost simultaneously

in this case. In many cases the cleavage of
the cytoplasm is such that all of it is used up
in forming the new cells, the spindle fibrillae
taking no part in the process. In other cases,
as in the formation of ascospores in the ascus,
the kinoplasmic fibrillae radiating from the
Internal c^ ccutrosomc outlinc the new cell in the midst

formation. rj.i i?j.i i ' ^ n

01 the mass oi cytoplasm, leavmg much of
the latter outside of the new cells, the so-called cpiplasm.

35. Cell formation by union is in the main the opposite
process to that by division. The union of the cytoplasm
of the uniting cells is usually followed by the union of the
nuclei to form one nucleus. If the cells are naked the
process is comparatively simple, but when enclosed in
walls the cells must either escape before uniting, or open-
ings must be made in the walls so that one cell can pass
into the other. By the union of the two nuclei the num-
ber of chromosomes is doubled and remains at this so-
called diploid number until by a peculiar modification of
the mitotic process (the reduction division ormeiosis) the
number is reduced to the original (or haploid) number.

Laboratory Studies, (a) Scrape off, after moistening with
alcohol, a little of the 3'oung white moldy growth on a lilac
leaf (powder}' mildew) or of similar mildews on cherry shoots

_ >EKrr UBRARf
IJ^ C. State College

LABORATORY STUDIES 25

grass leaves or other plants. Mount in dilute potash.
Threads will be found showing the formation of new cells
(spores) l\v fission.

(b) Add a little sugar (preferably glucose) to a little potato
water (made bj^ grating up a raw potato and heating with
water to extract the soluble matter and filtering) and break up
in it part of a yeast cake (''compressed yeast") setting the
solution in a warm place. Examine a small drop of the scum
or sediment after a few hours for cells showing the type of
fission called budding.

(r) By growing yeast for a few da3\s on a moist slab of
plaster-of-Paris under a bell jar or, less successfully in many
cases, on the cut surface of a raw potato or carrot some of the
cells may be found to have produced four cells by internal cell
division.

(d) Make a very tliin cross-section through a young flower
bud, or moss capsule. In the stamens of the former or in the
interior of the latter, if they are at the right stage, will be found
cells which have divided internally into four parts which sub-
sequently become spores, each with a thick wall of its own.

(e) Take a flower bud of Tradescantia just before opening
and remove a stamen and mount in water of about the room
temperature. By examining with proper manipulation of the
light, some cells near the tips of the stamen hairs may be found
in division and the main features of the mitotic division of the
nucleus may be dimly seen.

(/) Examine specially prepared, stained sections of rapidly
growing root tips, stamens, etc., where cell divisions are taking
place frequently. Find and study as many stages as possible
of the mitotic division of the nucleus and cells. These prep-
arations require especial technique and cannot be made
successfull}^ by the beginning student. It is desirable that he
study good preparations. Such can be obtained of various
su})ply houses if the teacher has not the time or desire to make
them.

(g) Cell formation by union can be observed in the conjuga-
tion of pond scums (Spirogyra or Zygnema) or of black molds
(Mucoraceae, especially Sporodinia, which is frequent on
decaying toadstools and can be transferred to bread where it
grows luxuriantly).

26 PROTOPLASM AND PLANT CELLS

REFERENCE BOOKS

B. AL Davis, Studies on the Plant Cell (American Naturalist,

(1904-1905, Boston).
Strasburger, Jost, Schenck and Karsten, Lehrhuch der

Botanik, 11 Ed., Jena, 1911 (or English Edition), and the

12 German Ed. 1913.

CHAPTER II

THE TISSUES OF PLANTS

HISTOLOGY

36. In many groups of plants a single cell makes up
the whole plant. In such groups the cells may vary
considerably in different species but there is not possible
a differentiation into cells of different structure for differ-
ent functions. All of the normal activities of the plant
are carried on by the same cell and, therefore, the modi-
fications of the cell are limited to those that do not inter-
fere with any of these functions. Aside from these
limitations the cell may vary much in size, shape, struc-
ture of wall, location and size of nucleus and vacuoles,
etc.

37. In other forms of plants there are several to many
cells forming one plant in which all of the cells are
essentially alike and each capable of continued existence
by itself even if the others should be destroyed. Such a
plant is scarcely more than a group of nearly independent
individuals. As we study the more and more complex
forms of plants, however, we find that the cells are no
longer all alike or nearly so, but that some are different
from the others in shape, structure and function. The
cells are not all equivalent, the plant is not now a collec-
tion of nearly independent individual parts (cells) ))ut
the whole must be considered as an individual made up
of numerous differentiated parts. It is true that in the
history of every plant there occurs a one-celled stage and

28 THE TISSUES OF PLANTS

by the division of this cell the plant originates, but none-
the-less the whole plant is to be considered as a unit and
not as an association of distinct cells.

38. In such higher plants we can distinguish several
types of differentiated cells and can with correctness
speak of tissues. A tissue may be defined as an associa-
tion of similar cells for a common function. In the less
differentiated plants the same tissue will have many
different functions; in the more highly specialized forms
there will be more kinds of tissues each with few^er func-
tions. In the study of tissues we must distinguish
between the so-called ''false" and 'Hrue" tissues. The
former are those that are formed by the subsequent close
association of cells that originated independently of one
another. Thus many separate motile cells (zoospores)
may join themselves to one another in such a way as to
form a definite structure (e.g. Hydrodictyon) or a sort of
tissue may be formed by the growing together of numer-
ous originally separate filaments of cells. On the other
hand a true tissue is formed by successive divisions from
one or a few cells, so that every cell may be said to have
been formed in place. In the false tissues the walls
between adjacent filaments or cells of different origin are
double, without a true middle lamella while in true
tissues the walls are single and the middle lamella is
present (at least at first). It is sometimes impossible to
make a very sharp distinction between these two kinds
of tissues as one method of origin may be combined with
the other. False tissues are found almost exclusively
in the higher fungi and some of the algae while the tissues
of the higher plants are true tissues.

In the following discussion only the more highly
differentiated types of tissues, such as occur in the higher
plants, will be described in their main features while the

IVIERISTEM, AND PARENCHYMA 29

loss difTereiitiiited or more gciKU'alized tissues of the lower
plants will not be considered.

39. Meristem. This is the form of tissue from which
ultimately all the other kinds arise. It is often spoken
of as rudimentary tissue from this fact. It consists of
small, usually rapidly dividing cells (at least during; the
growing season), some of which usually continue as
meristem, while others by enlarging and ceasing their
active division and by other modifications become other
kinds of tissues. Meristem is present in those parts of
the plant where new cells are being formed, i.e. in young
buds, at the apex of growing stems and roots, in the
developing seeds, etc. Meristem cells are usually small
and very thin-walled, and filled with cytoplasm, and
with a nucleus which is large in proportion to the size of
the cell and mostly central in location.
The vacuoles are small or entirely want-
ing. At the growing points of stems and
roots the cells are usually nearly cubical,
in other locations (e.g. cambium) they
may be elongated. If the plant be one ^ « ,, .

. \ . . , , . Fig. 9.— Moristem

with plastids they are present in men- tissue.

stem cells often as a single, very small, hardly distin-
guishable body. Some botanists, however, are of the
opinion that plastids are newly formed in the tissues
developed from the meristem.

40. Parenchyma. This is the chief vegetative tissue
of the higher i)lants and makes up much the larger part
of the living portions of the plant. It is the main nutri-
tive, storage and rei:)roductive tissue. Its cells are
much larger than those of meristem, from which it is
directly derived, but they preserve in general much the
same shape, i.e. they are rounded or polyhedral and usually
not much elongated. The cell walls are thicker than

30 THE TISSUES OF PLANTS

in meristem but are still usually thin, although in certain
modifications, e.g. the parenchyma occurring in wood
and sometimes that in the pith of woody twigs, the walls
may be considerabl}- thickened. In composition the
wall is usually a form of cellulose except where thicken-
ing has begun in which case the walls are often lignified.
A large vacuole occupies the center of the cell and leaves
the cytoplasm as a thin parietal layer (i.e. lining the wall)
although there are often cytoplasmic strands running
across the cell from one side to the other through the
vacuole. The nucleus is generally imbedded in the
parietal cytoplasm and appears relatively small owing
to the great increase in size of the cell in its development
from meristem, unaccompanied by a corresponding
increase in the size of the nucleus. The chloroplasts are
well developed in those parenchyma cells exposed to the
light (except of course in plants devoid of chlorophyll).
Very generally at the angles of contact of three or more
parenchyma cells the middle lamella is ruptured or dis-
solved and the corner of each cell be-
comes rounded off leaving a space
which becomes filled with air, a so-
called intercellular space, these form-
ing a continuous aerating system
throughout the living parts of the
Fig. 10.— Parenchyma plant. lu somo parts of a plant,
as in the pith, the parenchyma cells
die early and the cell contents disappear, being re-
placed by air. Probably this occurs by the absorption
of the protoplasm by the adjacent cells.

Laboratory Studies, (a) For undifferentiated cells examine
the one-celled green slime plants (Protococcus) found as a green
coating on the north side of trees or walls and the manj^-celled
pond scums (such as Spirogyra or Zygnema) or one of the sim-
ple filamentous blue-green algae (as Oscillatoria) which often

LABORATORY STUDIES 31

forms a purplish or brown slimy layer on flower pots in
greenhouses.

(b) For false tissues examine a longitudinal section of the
stalk of a toadstool. Here the longitudinal rows of cells are
distinct filaments grown together into one mass. Similarly
the basal portion of the apothecium of cup-fungi is made up of
false tissue, although here the separate filaments are often
indistinguishable. Some of the algae are also good examples,
e.g. Udotea, Lemanea, Nemalion, etc,

(c) For meristem examine a thin longitudinal section of a
root tip. For this purpose the first strong root from a ger-
minating grain of Indian corn or the j^oung, so-called 'Morace
roots" from near the base of the stem of that plant are good, as
are young roots from onion or h3^acinth bulbs. By staining
lightly with eosin or safranin the nuclei and cytoplasm become
more distinct.

(d) ]\Iake similar longitudinal sections of a very young flower-
or leaf-bud, e.g. lilac or elder, or of the growing tip of asparagus
or of a pumpkin or squash vine and examine the meristem tis-
sue. Compare the cells with those in corresponding locations
in sections made in the older parts of the stem.

(e) For parenchyma cells make thin longitudinal and cross-
sections of a young green stem of Indian corn or of a green shoot
of elder. Excluding the woody and epidermal parts the bulk
of the stem at this stage consists of parenchyma. Treat the
section with iodine solution and then with sulphuric acid. A
blue coloration indicates cellulose.

(f) Make a cross-section of a typical leaf such as apple, lily,
nasturtium, etc. The green cells are parenchyma tissue.

(g) IMake a thin section of the tul^er of potato to show
storage parcncln^ma. Similar parenchyma may be found in
the fruit of an apple or pear, etc.

(h) In thin cross or tangential sections of a living woody twig
will be found the medullary ra3^s. These consist of rather thick-
walled living parenchyma, the walls being more or less lignified
and provided with thin spots (pits) here and there through
which water and food substances can pass from cell to cell.
Stain different sections with iodine and sulphuric acid as a test
for cellulose, and with a five percent aqueous solution of ])hlo-
roglucin and hydrochloric acid as a test for lignified cell walls,
the latter taking a red coloration. Examine in similar manner

32 THE TISSUES OF PLANTS

the pith cells of one or two year old twigs of apple. These are
also somewhat tliick-walled.

41. Sclerenchyma is the name given to a tissue con-
sisting of more oi; less rounded or polyhedral, usually
not much elongated, thick-walled cells whose function is
to give support or protection to other tissues. These
cells originate from meristem by the thickening and
lignification of the walls, passing through an intermediate
parenchymatous stage. During the process numerous

spots on the walls remain thin so that
eventually they show as canals from the
small central lumen of the cell to the
original outer wall. These canals or pits

Fig. 11. -Sclerenchyma COrrCSpOUd ITi adjaCCnt CClls. Upon

( 10 -ory nut). reaching their final development the cell
contents die. Sclerenchyma cells are often called stone
cells. They are found in seed coats, nut shells, bark,
etc., where protection or support is required.

42. Of a much different type from the foregoing are
those tissues consisting of elongated cells with more or
less thickened walls whose function is the mechanical
strengthening and support of the plant body. To per-
mit bending while at the same time retain-
ing their supporting function they are more
or less elastic, a characteristic less marked
in the short-celled sclerenchyma whose func-
tion is protection or only local support. ^^^^ 12 — Coiien-
We can distinguish two types of these sup- chyma.
porting or mechanical tissues, collenchyma and fibrous
tissue.

43. Collenchyma. Directly ])eneath the epidermis of
many plants are found smaller or larger strands of elon-
gated cells whose longitudinal cell walls are thickened at
the angles where three or more cells come in contact.

FIBROUS TISSUE 33

Except in old cells the thickening rarely extends out
upon the wall lying between the angles. The cells
remain alive, for a long while, and usually contain chloro-
plasts. They remain capable of growth longitudinally.
Accordingly collenchyma is found to be the chief mechan-
ical tissue in growing parts of plants, such as stems,
leaf-stalks, etc. The thickened parts of the walls are
composed of cellulose and transmit the light with a pecu-
liar pearly luster when viewed in cross-section, the lumen
of the cell under these conditions appearing darker than
the cell walls.

44. Fibrous tissue consists of elongated cells, thick-
ened on all sides, usually overlapping at their more or
less tapering, often pointed, ends. The walls show
minute, usually ol^liquely placed, slit-
like pits. After they reach full develop-
ment, the cell contents die, so that the
cells are incapable of further growth or
development. The thickened walls are
usually strongly lignified. In cross-sec-
tion the cells are round or by mutual Fig. 13.— Wood and

, 1 -r-,., . . bast cells.

pressure, angled. Inbrous tissue is
found as the chief mechanical tissue in parts of plants
which have completed their longitudinal growth. Two
types can be distinguished, viz., bast and wood fibers.
The former are located in the outer part of the stem
(in the cortex in the Dicotyledoneae), the latter in the
true wood. Bast fibers are usually longer than wood
fibers, and more slender, with often thicker but less com-
pletely lignified and hence more elastict walls. Their
usual length is from 1 to 2 mm. but in Bochmcria nivea,
the ramie plant (according to Haberlandt) they reach a
length of 220 mm., the longest plant cells known. Wood
fibers are usually shorter (mostly 0.3 to 3.1 mm.) often

34 THE TISSUES OF PLANTS

somewhat thicker, with less tapering ends and frequently
with less thickened walls which are more strongly ligni-
fied than those of bast fibers.

Laboratory Studies, (a) Break tlie shell of a hickory nut,
ahnond, coconut, walnut, peach-stone, etc., and after smooth-
ing the broken surface, cut off a thin shaving, using a pocket
knife or scalpel held at rather an oblique angle. Mount in
water and a httle potassium hydrate. The very small cell
cavities show connecting pits or canals radiating from them to
the original cell wall where they meet similar canals from the
centers of adjoining cells, being separated only by the thickness
of the original wall. Concentric markings are visible in the
cell walls in some cases.

(b) Determine whether the walls in sc^erenchyma are made
of cellulose or are lignified, by testing one section with a 5 per
cent, aqueous phloroglucin solution followed by hydrochloric acid
which gives a red color for lignified walls, and another section
with iodine solution followed by somewhat diluted sulphuric
acid which gives a blue color for cellulose walls.

(c) Sclerenchj^ma may be found and studied (1) as the little
''grit" bodies in the flesh of the pear or sapodilla (Achras
mpota), (2) in the underground stem of the brake {Ptcridium
aquilinimi), (3) next to the epidermis in the prickly pear
(Opuntia), as well as (4) in coats of many seeds, e.g. apple,
squash, wild cucumber, and (5) forming the body of the
seeds of many palms, e.g. date.

(d) Examine a young leaf-stalk of the squash or pumpkin
and note the whitish bands, 1 or 2 mm. wide, which extend from
end to end just beneath the epidermis. These are bands of
collenchyma. They may be readily torn out, when the stalk
will be found to have lost much of its strength.

(e) Make a very thin cross-section of the leaf-stalk of one of
the foregoing plants, exactly at right angles to the axis of the
collenchyma strands, and examine under low and high magnifi-
cations. Test with iodine and sulphuric acid to determine the
composition of the walls.

(/) ]\Iake longitudinal sections through these collenchyma
Imnds. If good sections are obtained the thickened angles
(becoming thin toward the point where the thin cross walls
occur), chloroplasts and nuclei will be found. However, only

TRAClIEAllY TISSUE 35

those cells that happen to be so placed that a thickened angle
appears in the section will show this feature. On the other
liand, if the section passes between the corners of the cell the
walls will appear thin.

(g) CoUenchyma may be found also in the young green shoots
of elder (Sanibucus) and some other shrubs, in the stems of
lamb's quarters (Chenopodium), pigweed (Amaranthus),
petioles of beets and very many other plants.

(h) Make thin longitudinal sections of the wood and bark of
the basswood (Tilia) or maj)le (Acer) and macerate, to
separate the cells, in Schulze's reagent (i.e. heat in a test tube in
nitric acid to which has been added a little potassium chlorate).
Mount a bit of the macerated wood section on a slifle and tap
the cover glass, or tease the section apart with needles.
Study the wood fibers. Do the same for the bast fibers in the
bark.

(i) Now make thin longitudinal and cross-sections of the
same kind of twig without macerating and study the fibers in
place to note the relation of the overlapping cells. In the cross-
section, note the appearance of the fibers and their position in
the twig.

45. Besides the foregoing, there is a group of tissues
which have as their chief function the conduction of
water and food, the so-called conductive tissues. These
are of three kinds: tracheary tissue, whose primary func-
tion is the transportation of water, and sieve and lat-
iciferous tissues, which are chiefly concerned with the
conduction of food substances manufactured by the
leaves.

46. Tracheary tissue is of many kinds. The term is hero
used to include those elongated cells, whose chief function
is the transport or storage of water. The lumen is usually
rather large with the wall thickened in a more or less regu-
lar manner to give strength. At the same time, a consider-
able portion of the wall remains thin, permitting the en-
trance or exit of water. The cells are not living, i.e. their
protoplasm dies as soon as they have attained their final

36 THE TISSUES OF PLANTS

development, so that the conduction of the water is not
dependent upon the activity of these cells but occurs in
the cavities left empty by the disappearance of the proto-
plasm. Since the cells lack protoplasmic contents which
would furnish the turgor to keep them from collapsing,
the thickening of the walls is necessary. It often happens
that adjoining living cells swell out through the thinner
places into these cells, these bladder-like projections
being called tyloses. A distinction is made between
tracheids which are formed of single cells, and tracheae
(singular, trachea) or vessels, which are more or less
elongated tubes formed by the absorption of the cross
walls of adjoining cells so that the lumens of many suc-
cessive cells are all connected. The latter usually attain
the greater diameter. Tracheids are mostly not over 1
mm. long although in some cases they reach a length of
1 centimeter or even much more. Tracheae, accord-
ing to Strasburger, average about 10 centimeters long,
but in some cases reach a length of 2 to even 5 meters.
In some vines, the diameter reaches 0.3-0.7 mm. Trach-
eary tissue is found only in the higher plants, i.e., Seed
Plants and Ferns and Fern Allies.

47. In accordance with the character of the thickening,
there may be distinguished sev-
eral types of tracheary tissue,
these same types of thickening
being found both in tracheids
l^^)Mg?"^r^ I M rn ^^^ tracheae. These are ringed
^^ringtdTspirJureticJiatedK'^^ (or anuular), Spiral, reticulated

(netted), scalariform (ladder-
like) and pitted tracheae or tracheids. All but the last
are named after the manner of the internal thickenings of
the walls. The pitted cells, however, are those in which
the thickening is more extensive than in the others, the

TRACHEARY TISSUE 37

thin places remaining only as small pits. The cells of all
these structures are usually more or less pointed and over-
lapping at the ends, except in some of the tracheae in
which the square end walls were dissolved out. They
are mostly round or by mutual pressure somewhat angled
in cross-section.

48. The spiral and annular thickenings are the
only types found in the tracheary tissue that is formed in
stems or roots that are still elongating, as it is possible
for such cells to elongate by the stretching or growth of
the unthickened portion, whereby the rings become
farther apart or the spirals stretched out at a greater
angle. Very often adjacent rings may be connected here
and there by a spiral or the same vessel may have annular
thickenings in one part and spiral in another. There
may be from one to three or four spirals. The reticu-
late type of thickening is perhaps to be considered as a
many-spiraled type with numerous cross connections
from one spiral to the next so as to form a network.
Scalariform vessels are usually angular in cross-section
and have their thickenings on the flat faces of the prisms
as horizontal bars connected to the somewhat thickened
angles, and leaving horizontally elongated thin areas be-
tween them like the openings between the rungs of a
ladder. All transitions may be found from the reticu-
lated or scalariform structure to the pitted type. The
pitted tissues are of two types: (a) with simple pits, and
(6) with bordered pits. In the first the pits are of the
same diameter through their whole depth or even wider
toward the center of the cell. In the second, the}- are
narrow, adjacent to the cell lumen and are much wider as
they approach the middle of the cell wall, the cavity of
each pit having the shape of a planoconvex lens. The
wall or diaphragm separating the adjacent pits of ad-

THE TISSUES OF PLANTS

xoi

Fig. 15. — Tracheary tissue
(pitted and tracheids).

joining coUrf is very thin and permeable to water except
a button-like thickening, in the center. When seen in
surface view, a bordered pit shows a double circle, the
smaller inner one being the opening into the pit and the
outer circle, the outer edge of the diaphragm.

49. Special mention must be made of the tracheids of
Conifers (Spruces, Pines, etc.).
These are shaped and thickened
like wood fibers but differ in
possessing on their radial faces
one or more longitudinal rows
of bordered pits. They com-
bine the functions of tracheids
and fibrous tissue, serving both
for conduction of water and for
mechanical support.

50. Sieve Tissue. In almost
all of the higher plants and in many of the more massive
lower plants, there are found rows of elongated rather
wide cells whose transverse separating walls are pierced
by numerous larger or smaller perforations. Where two
such cells lie side by side parts of the lat-
eral separating wall will often show simi-
lar perforated areas. These are the so-
called sieve plates which give the name to
this tissue. The walls of the sieve tubes,
as the elongated cells are called, are usu-
ally rather thin. The sieve plates, on the
contrary, are rather thick. In surface view
they look like a sort of network. In some cases, the
meshes of the net are perforations, in others, they are
thin walled areas perforated by several to many fine holes.
The mature sieve tubes have the walls lined with a thick
layer of cytoplasm in which the nucleus is imbedded.

Fig. 1G.— Sieve
tissue.

LACTICIFEROUS TISSUE 39

The centi'iil vacuole is filled with a liquid ver}- rich in i)ro-
tein matter, the masses of this protein substance often
being continuous through the pores of the sieve plates
with those of the adjoining sieve tubes.

51. The sieve tubes of the Flowering Plants are
accompanied b}- usually slender parenchyma cells full of
protoplasm, the so-called companion cells. The walls
between these and the sieve tubes are perforated by
numerous very minute passages invisible except b}" special
manipulation. Other forms of parenchyma cells are
usually found adjacent to the sieve tissue. The function
of the sieve tissue is probably the transportation of
protein substances from the leaves to parts of the plant
where they are needed in the construction of new cells.
Possibly, also, sugars are transported, at least in part, in
the same tissues as well as in the ordinary parenchyma
cells near them. The function of the companion cells
is not certain.

52. Laticiferous Tissue. This consists of a system
of tubes extending throughout the plant
and filled wdth a substance called latex.
This is usuall}' white (hence the name ''milk
tissue" often applied to this kind of tissue),
but may be colored red, j^ellow or even be
almost clear and colorless. The latex con-
sists of water containing usually much pro- Fig. i?.— Laticif-

,, erous tissue.

tem matter as well as some sugar and
salts dissolved in it, and holding in suspension numerous
minute globules of resin or in many cases, caoutchouc.
On exposure to the air, the latex often coagulates. It is
from the latex of many plants that rubber and gutta
percha are obtained, while other substances of great value
are often found in it also, e.g. opium in the latex of
the poppy. In some plants, starch grains are found in

40 THE TISSUES OF PLANTS

the laticiferous tubes. The walls are lined with cyto-
plasm containing nuclei. They are mostly thin but in
Euphorbia the walls are thick and elastic.

63. Two distinct types of laticiferous tissue may be
distinguished: (1) Non-anastomosing and (2) Anastomos-
ing. The forrner consists of branching tubes which
originated from single cells in the embryo. These cells
elongate and branch, keeping pace with the growth of the
plant, forcing their way between the meristem cells
exactly as if they were part of a fungus instead of a tissue
of the plant in which they occur. They appear never to
anastomose. They are found in the Euphorbiaceae,
Moraceae, Apocynaceae, etc., i.e. in the chief rubber-
producing families.

54. The anastomosing milk vessels are formed by
the fusion (that is through the resorption of the separat-
ing walls) of adjacent meristem cells in such a way as to
form a network of latex-bearing tubes. Short lateral out-
growths may also be sent out from one tube to another,
thus increasing the number of anastomoses. Laticiferous
tissue of this type is found especially in theLactucaceae,
Papaveraceae,etc., as well as in a few of the Euphorbiaceae,
e.g. Manihot and Hevea, both rubber-producing trees of
great economic value.

Laboratory Studies, (a) Make a thin longitudinal section
of the stem of garden balsam (Impatiens) or any other her-
baceous plant that has not begun to become thickened and
wood3^ The section should pass through one of the vascular
bundles. There will be found various tj^pes of tracheary
tissue, those facing the interior of the stem being usually of the
annular or spiral type, with reticulated and pitted types to-
ward the outside.

(6) Good plants for study are Tradescantia, especially for
ringed and spiral types of tracheary tissue; Sida, for good spiral
and reticulated types; Indian corn, pumpkin or squash, etc.,
for large pitted vessels.

LABORATORY STUDIES 41

(<:•) Study tlie foregoing types of tracheary tissue in cross-
section in comparison with the longitudinal sections.

((/) The larger pores in the wood of oak, hickory, etc., as
well as in the grape, are pitted vessels.

(e) Excellent scalariform vessels are to be found in the
leaf-stalks or better still, in the underground stems of the
brake {Ptcridium aquilinum).

(/) The tracheids of pine, spruce, etc., resembling wood fibers
in shape, but with bordered pits, should be studied by making
tangential and radial longitudinal sections as well as cross-
sections of the wood. The bordered pits occur only on the
radial surfaces of the tracheids.

{g) Spirally marked tracheids, similar in shape to the fore-
going, may be found in the wood of the hackberry (Celtis),
and ash.

{h) By treating various kinds of wood with Schulze's reagent
(nitric acid and potassium chlorate, warmed) the various cells
will be separated and the tracheary elements of different kinds
can be studied separately.

{%) Sieve tissue is easily found by making longitudinal sec-
tions of the stems of squashes or pumpkins (Cucurbita) or
other vines such as grape, clematis, hop, etc. They will be
found in the part of the vascular bundle Ij'ing toward the
outside of the stem and in the case of Cucurbita also on the
inner side. By staining with eosin or carmine, the protoplasm
and protein contents will be stained. If alcoholic material be
used, the contents will be found shrunken away from the sieve
plates. If portions of living stems are killed before sectioning
by dipping into very hot water, the protein and protoplasmic
contents will be coagulated without much contraction.

ij) Make numerous very thin cross-sections of the same
stems and examine until sieve plates are found and studied in
surface view.

{k) Examine a drop of latex from milkweed, spurge or poppy,
under high magnification. The suspended granules will be
visible as fine dark brown bodies by transmitted light. Test
with iodine to determine whether starch grains are present.

(/) Collect a quantity of latex of spurge (Euphorbia) and
let it evaporate in a watch glass. The residue is a sticky,
rubbery mass, which on being burned, has the characteristic
odor of burning rubber.

42 THE TISSUES OF PLANTS

(m) For the study of laticiferous tissue thin tangential
sections are best. The tissues will show as tubes filled with a
brown granular mass, the latex. The non-anastomosing type
can be found in the milkweed (Asclc})ias), dogbane (Apo-
cynum), and spurge (Euphorbia), especially the more fleshy
forms of the latter. The anastomosing tyj^c can l)c studied
in the petioles of dandelion or lettuce, or in the stem of the
poppy.

(n) The long, branching, non-anastomosing laticiferous tubes
of Euphorbia can be isolated from the more fleshy leaved sorts
by boiling the leaves in dilute potash solution and then teasing
out a piece of the softened tissues.

(o) To examine the tissues in situ, the leaves should be
placed in strong alcohol (90-95%) for some hours. If the
leaves are thick, thin sections should be made parallel to
the surface. These sections, or the whole leaves if they are
thin, should then be placed for an hour or so in a clearing fluid
made of equal parts of turpentine and carbolic acid (phenol).
Mount the section or leaf in this fluid. The tissues are made
transparent, and the laticiferous tubes filled with granules of
latex can be studied with great ease. The same method can be
used for studying both types of laticiferous tissue.

REFERENCE BOOKS

The books enumerated for Chapter I and the following.
A. DeBary, Co?nparative Anatomy of the Vegetative Organs of

Phanerogams and Ferns (Engl. Ed. 1884. Oxford).
G. Haberlandt, Physiologische Pflanzenanatomie, Leipzig,

1904. (Engl. Ed. 1914. London.)

CHAPTER III

GROUPS OF TISSUES, OR TISSUE SYSTEMS

HISTOLOGY

65. In the lower plants, where all cells are essentially
alike and no distinction of tissues can be made, we often
find that growth takes place in all parts of the plant, al-
most every cell being capable of growth and division at
any age. In many plants, however, in which the differ-
entiation into various kinds of tissues is still almost lack-
ing, we find that growth is more or less limited to certain
regions of the plant. In those plants where the tissue
differentiation is strongly marked, we find that the
formation of new parts, as well as growth, is localized
in groups of meristem cells at the apices of stems and
roots (and also in many plants at the nodes), the older
cells of these groups gradually changing into the more
permanent tissues of the plant.

56. In many seaweeds and fungi, where the plant
body consists of separate or adjacent rows of cells, the
terminal cell of each row elongates and divides by a
cross partition and perhaps division occurs in one or two
cells behind it. Except for the formation of branches,
longitudinal divisions may be lacking and the result is
only the formation of rows of cells.

57. In the plants which are not so markedly fila-
mentous in structure the new tissue at the ai)ex may arise
by the division of a single aj)ical cell. This division
may be by horizontal i)artitions, the seguKMits thus

44 GROUPS OF TISSUES, OR TISSUE SYSTEMS

formed dividing subsequently by both horizontal and
longitudinal partitions (as in Sphacelaria and many other
algae). More often, we find that the apical cell is a three
sided pyramid, the convex base of the pyramid being
the apex of the shoot. Successive cells are cut off from
the three sides and the segments
thus produced divide by various
partitions so as to produce the mass
of meristem cells from which the tis-
,„ . . , „ r sues become differentiated. Some-

FiG. 18. — Apical cells of , ,

a seaweed (Sphacelaria), timeS, mstcad of the apiCal Cell

and a moss. . ^ ,

cuttmg off three rows of segments,
it produces only two or in other cases, four.

58. In most of the Flowering Plants, a group of cells
is found at the apex of the stem or root instead of one
cell, these giving rise, by their division, to the mass of
meristem. This group of apical cells, or the single apical
cell with the cells derived from it, is called the growing
point.

59. We can usually distinguish three different tissue
regions at or a short distance back from the growing
point of higher plants. At the outside we find a single
layer, the epidermis, which consists of cells that divide
only by walls perpendicular to the surface. When this
layer has an initial cell or cells distinct from the inner
layers the portion near the apex is often spoken of as
the dermatogen. The next region is spoken of as peri-
blem, and may consist of one or several layers of cells
surrounding the centrally located plerome. These two
regions may have separate sets of apical cells or the dis-
tinction may occur only some distance from the apex.
In most roots, the apex is covered by the root cap, a
mass of cells produced by the periclinal division (i.e.
by walls parallel to the surface) of a layer of cells outside

GROWING POINT 45

of the dermatogen, or in some cases, of the dermatogen
itself, or, in still other cases, by the division of some of
the cells of a common mass of initial cells from which the
root cap as well as epidermis, periblem and plcrome
arise. On the growing points of stems, the new branches
arise by the formation of secondary growing points at
the side of the main one, these having the same
general plan. Those that produce the leaves often grow
faster than the mai growing point and sur-
round and protect it, thus forming a bud. v ^ .■

60. As the growing point progresses, the
cells formed in it come to lie further and
further from the apex. They increase in size V,:
and, after a while, cease to divide. Certain v.>''
of the cells remain meristematic a long while; DfrmatigeiT
others become elongated, i.e. cease early to di- pYe*i-^o m Tit
vide transversely, and eventually become ering Pialr"
transformed into fibrous, tracheary, sieve tis-
sue or collenchyma. Some cells merely enlarge and
become parenchyma. Thus, near the tip the cells will
be found to be all meristematic, but further back, various
kinds of tissues may be found.

Laboratory Studies, (a) Make a longitudinal section of the
end of a Ijranch of the marine alga, Codium tojuentosinn. Here
the growing region is not a few cells as in a true growing point,
but each filament elongates at the aj)cx without tlie production
of cross walls. Many of the Red Seaweeds (Rliodophyceae)
show the same type of apical growth except that transverse
walls are formed near the apex of each filament (e.g. Melobesia,
Ncmalion, etc.).

(b) Examine the end of a shoot of Sphacelaria, one of the
Brown Seaweeds. Here there is a single ajiical cell which divides
by a transverse partition, the segments tluis formed dividing
longitudinally and transversely.

{(■) Make a thin longitudinal section througli the growing
point of a moss or of a stem or root of a fern or horsetail

46 GROUPS OF TISSUES, OR TISSUE SYSTEMS

(Equisetum). This is a difficult section to make, but if suc-
cessful the growing point, with its single apical cell, can be
studied. Sometimes this can be seen better by making
successive, very thin cross-sections at the tip of a fern root.
In this case, the apical cell will be seen in transverse view.

((/) IVIake a longitudinal median section through the growing
points of a stem and a root of a Flowering Plant. (Stained
microtome sections are preferable to hand sections since they
are thinner and more likely to show the desired features.)
Note that all of the tissue near the tip is meristem. Observe
the three regions, dermatogen (epidermis), periblem and
plerome. Trace them to their origin. On the root section,
note also the root cap and its origin.

61. The tissues produced from the primary meristem
in the manner described above have definite functions
to perform, and occupy definite positions in the plant
body. The outer layer or epidermis is set off as a boun-
dary tissue; other cells are developed into the skeletal or
supporting tissues, still others are for transportation of
water and food, while the remainder of the cells are at
first not so clearly differentiated for special functions.
This less differentiated group of tissues may eventually
fulfill various functions depending upon the part of the
plant they occupy, the nature of the plant, etc. Thus
they may be food making, as in leaves; for storage pur-
poses, as in tubers, many roots, some pith, etc. ; protective,
as in the shell of nuts where the tissue is changed to
sclerenchyma.

62. According to the kinds of tissues and functions,
it is customary to differentiate several so-called ''tissue
systems.'' These may be defined as aggregations of
elementary tissues, forming definite portions of the plant
and with a definite function. It is at once evident
that tissue systems cannot be distinguished where tissues
are not yet differentiated. In fact, we usually speak of
them only in connection with the higher plants.

EPIDER.MAL 8\\STEM 47

63. Three tissue systems are easily recognizable in
the higher plants apart from the less differentiated mass
of cells in which they lie. These are: (1) the epidermal
system, composed mainly of the boundary cells and their
appendages (hairs, scales, stomata, etc.) ; (2) the conducting
system, comprising those tissues which are water or
food conducting and the tissues immediately associated
with these; and (3) the mechanical or skeletal system,
consisting of the fibrous tissue, collenchyma and scler-
enchj^ma which furnish the rigidity and strength
necessary for the plant. The latter two are sometimes
considered together as the fibrovascular system, while
the remaining tissues are often grouped under the name
fundamental system. The latter is, however, no definite
aggregation of tissues but rather the residue of less
strongly specialized tissues from which we have rather
arbitrarily set off the other tissue systems, for we must
remember that these are all coherent parts of one plant
body and not separate parts without close interrelation.

64. The Epidermal System of Tissues. This is
perhaps the earliest tissue system to have been differ-
entiated from the remainder of the plant. In many
lower plants, the exterior and interior cells show no
visible differences, but even here among some we
find that the outer cells are more closely crowded together
and smaller while the inner cells are loosely arranged.
In the fruits of some fungi, the outer layers of cells are
firm and resistant. Some of the Liverworts and ^Mosses
possess an outer layer of cells distinct from the inner
cells and evidently of protective nature. It is only in
the higher, more massive land plants, however, that we
find a really distinct epidermal system of tissues. Thus
in the Ferns and onward through the various Fern Allies
and throughout the Seed Plants, the epidermis and its

48 GROUPS OF TISSUES, OR TISSUE SYSTEMS

appendages are well developed. It is worthy of note,
however, that those plants of these groups that have
reassumed the aquatic habit have their epidermis scarcely
distinguishable from the rest of the tissues. The roots
of most plants, being usually in moist soil, have their
epidermis not very strongly differentiated.

65. The Epidermis. In most cases the epidermis
consists of a single outside layer of cells which surrounds
the whole plant in an almost uninterrupted sheet. It
frequently originates from an apical cell or group of cells

distinct from those producing the
rest of the tissues, or is differen-
tiated from the latter near to the
growing point. Mostly the epider-
mal cells may be considered as a
special kind of parenchyma tissue
with a protective function. In
many plants, however, especially
those of hot, dry climates, the cells
soon become thickened and more
or less sclerenchymatous. Usually
they remain alive, but in the forms where they have
been changed to sclerenchyma the contents commonly
die. In most cases, epidermal cells show no well de-
veloped chloroplasts although the cell sap may be brightly
colored.

66. In shape, the epidermal cells are usually more or
less flattened parallel to the surface of the plant. If
the growth of the organ is nearly equal in length and
width, the epidermal cells seen from the outside will be
nearly isodiametric, but if the longitudinal growth has
been markedly greater than the transverse growth, the
epidermal cells will usually be elongated. Frequently
the cells are very irregular in outline. Except for the

Fig.

20. — Epidermis, with
stomata.

EPIDEILMIS 49

stomata, to be described later, no openings occur be-
tween the cells, even at their angles.

67. The most characteristic feature of well developed
epidermis cells is the thickening of the external wall
and the deposition in the outer layers of this wall of a
waxy or fatty substance called cutin. This water-proofs
the walls to a large extent and prevents loss of water
through them by evaporation. The cutin is not de-
posited equally throughout the outer wall, but is least
toward the cell cavity and greatest at the outside. The
outer, strongly cutinized portion of the wall is often
very distinct in appearance from the remainder of the
wall and can sometimes be stripped off as a continuous
sheet, the cuticle. Often this is coated externally with
a waxy or resinous coating, the ''bloom" of some
leaves or fruits.

68. The cutinized layer extends, in many cases, not
merely over the outer surface of the cell wall but even
down between the adjacent cells for some distance.
In roots, on the other hand, the younger parts are not at
all cutinized and further from the tip the cutinization is
only comparatively slight. The root hairs are cutinized,
if at all, only in their basal portion.

69. While the epidermis always consists at first of
but one lixyev of cells it becomes two to four layered in
some plants, e.g. oleander {Nerium oleander), rubber
plant {Ficus elastica), various cactuses (Opuntia), etc.,
by subsequent periclinal division (i.e. division by the
formation of a cell wall parallel to the outer surface)
of the original layer. The outer walls of these new
layers may become cutinized successively, from the
outer toward the inner layers.

70. The hairs originate mostly as outgrowths of single
epidermal cells. In the case of young roots the epidermal

50 GROUPS OF TISSUES, OR TISSUE SYSTEMS

cells at a distance of a few millimeters from the tip grow
out into long, normally unbranched, thin-walled hairs,
whose lumen is continuous with that of the main body
of the cell. These root hairs are not cutinized, or only
so at the base. They may attain a length of two or three
centimeters but are mostly not over one centimeter in
length and often much less. The thin wall is lined by a
delicate layer of cytoplasm and the central vacuole is
very large. These hairs push in between the particles
of soil and lie in the film of water with which these are
covered, absorbing some of this water by osmotic action.

Such mineral salts as are in
solution in this soil water in
greater concentration than
that of the same salts in the
cell sap diffuse into the cell

Fig. 21.— Root hair, glandular hair, and Upward thrOUgh the plant
branched hair, hair of nettle. , _ , i i

except so far as the plasma
membrane is impermeable to them.

71. The hairs on those parts of the plant exposed to the
air may be continuous with the epidermal cells from
which they have arisen, but mostly are separated from
them by cross partitions. They may remain one-celled
or may become many celled by cross septa. Sometimes
they are much branched or merely bifid or stellately
divided. In some cases the end cell of a short hair
divides by vertical partitions in several planes to form a
shield-shaped structure. Some hairs have the terminal
cell enlarged and functioning as a gland which secretes
sticky or oily substances. Certain hairs (as those of
nettles) contain strong irritant poisons. The tip of the
hair penetrates the skin of animals coming in contact with
the plant and then breaks, permitting the poison to be
forced out into the skin.

HAIRS, AND STOMATA 51

72. Not to be confused with hairs are those outgrowths
called emergences. These are not epidermal in nature
but are projections produced ])y the develo]:>ment of
cells beneath the epidermis. Often such emergences
are found bearing, and as it were, forming the support
for a stout hair, as in the sunflower or nettle.

73. The presence of hairs seems to be advantageous
to plants in many ways. They make it difficult for small
insects to ascend the plant, especially if the hairs are
pointed downward or are sticky-glandular. Stinging
hairs like those of the nettle, and also merely sharp-
pointed stiff hairs, such as abound on many plants,
are deterrents for animals that would otlierwise feed
on the plant. The same is probably true of various
evil-smelling substances secreted by some glandular
hairs. Finally, it has been shown that the presence of
hairs and scales reduces the loss of water from the plant
by forming an entanglement for a layer of air, thus
preventing the air currents from coming into direct
contact with the epidermis.

74. Stomata (singular, stoma), or breathing pores,
are definite openings through the epidermis to air
cavities beneath, through which an exchange of gases
takes place. These cavities (''substomatal chambers")
are connected with the intercel-
lular air spaces throughout the
plant.

75. Except in the Liverworts
(Hepaticae), where the stomata
are of different structure, the

typical stoma consists of an 0]:)en- Fig. 22.— Stomata, surface and

crosa-scctiou.

ing, slit-shaped or narrowly elli])-

tical, bordered by two, usually ('hlur()j)liyll-l)(niring, e])i-

dermal cells, somewhat kidney-shaped, and iiicontact with

52 GROUPS OF TISSUES, OR TISSUE SYSTEMS

each other at both ends. When these guard cells become
more turgid they curve outward, thus opening the stoma,
while a loss of turgidity results in its closure. Usually
the stomata open while the plant is in the light and close
partly, sometimes completel}^, in darkness. An excessive
loss of water by the plant reduces the turgor of the guard
cells, overcoming the effect light has in opening the
stomata, and causes them to close, thus conserving the
moisture in the plant.

76. Stomata occur on aerial leaves and stems and
more rarely on flowers and fruits. On underground stems
and leaves they are less abundant (and often not func-
tional), Avhile they are wanting on roots. On submerged
parts of aquatic higher plants they are lacking or only
rudimentary. On leaves they are usually more abundant
on the lower than on the upper surface. The numbers
as well as size of the stomata vary greatly for different
species. The following table will give an idea of their
relative abundance in some plants. (Page 53.)

Laboratory Studies, (a) Strip off the epidermis from the
upper and lower surfaces of the leaves of various plants, and
mount with the outer surface upward. If air bubbles
interfere, add alcohol, and follow this by a weak potash
solution, to swell the tissues again. Leaves of various grasses
or of carnation will show epidermal cells much elongated, while
more isodiametric cells may be found on the leaves of such
plants as the live-for-ever (Sedum or Sempervivum), dock
(Rumex), cabbage, etc.

(b) In the same specimens that were used for the foregoing,
study the stomata and their relations to the adjacent cells.
Compare the numbers of stomata on the two sides of the leaf,
and their relative size and number on different species of plants.

(c) Cut cross-sections of various leaves. Those of cabbage
and carnation, as well as of many other plants that grow in dry
regions, will show a considerable development of cuticle. Note
the structure of the stomata as shown in cross-section, and their

NUM15ER OF STO.MATA

Olive, Olea europaca

Black Walnut, Ju<>;laiis nigra

Red Clover, Trifoliuni pratense

Lilac, Syringa vulgaris

Sunflower, Helianthus annuus

Cabbage, Brassica oleracea

Sycamore, Platanus occidentalis

Lombardy Poplar, Populus nigra italica.

Hop, Huniulus lupulus

Plum, Prunus domestica

Apple, JMalus malus

Barberry, Berberis vulgaris

Pea, Pisum sativum

Box, Buxus sempervirens

Cherry, Prunus mahaleb

Thorn Apple, Datura stramonium

Indian Corn, Zea maj^s

Cottonwood, Populus deltoides

Wind Flower, Anemone nemorosa

Lily, Lilium bul])iferum

Iris, Iris germanica

Oats, Avena sativa

House leek, Sempervivum tcctorum

Water Lily, Castalia lotos

In one

square

millimeter

Upper

Lower

side

625

461

207

335

330

175

325

138

302

278

270

256

253

246

229

101

216

208

204

114

189

158

131

G25

relation to the substomatal chambers and the inter-cellular
spaces of the leaves.

(d) Make a cross-section of the leaf of oleander {Xcrium
oleander) or rubber plant {Fieus elastiea). In the former the
epidermis is in two layers, and in the latter sometimes as much
as four. This point can only be determined by making com-
parative sections of very young leaves and okl loaves. Note
the depressed, cistern-Hke pits in the oleander leaf, into
which the stomata open.

54 GROUPS OF TISSUES, OR TISSUE SYSTEMS

(e) Root hairs may be studied in cross- or longitudinal-sec-
tions of the young roots of seedlings that have been germinated
between damp cloth or paper, or in moist air. By adding a
rather strong sugar, or potassium nitrate solution the cyto-
plasm may be drawn away from the walls sufficiently (plas-
molyzed) to become visible.

(/) The leaves of various grasses (e.g. Panicum capillare)
will show simple one-celled hairs. The petunia stem possesses
unbranched hairs, consisting of rows of cells. Many will be
found to terminate in glandular cells. Hairs of these same types
ma}^ be found on tobacco, various species of Silene and very
many other plants.

(g) The stems and leaves of various crucifers (e.g. Erysi-
mum, Arabis, Bursa), show bifid hairs. Stellate and peltate
hairs are shown best on the leaves of species of Elaeagnus and
Shepherdia.

(h) The hairs of the common mullein (Verbascuin thapsvs)
may be studied as examples of greatly branched hairs.

(i) Cross-sections of the leaf or stem of nettle (Urtica and
related genera) will show the peculiar stinging hairs. Under
high power note the terminal knob which breaks off as the hair
penetrates the skin, thus permitting the distended base of the
turgid hair to contract and discharge the poisonous contents
into the skin.

77. The Conducting System. In most of the lower
algae and in the fungi, the plant body consists of separate
branching filaments, which are in some cases woven
together into a more or less firm body. These filaments
are about alike, and are mostly not differentiated into
conducting and other filaments. In some of the more
massive algae, however, as in the larger kelps (Laminaria,
etc.), or rock weeds (Fucus, etc.), the internal cells
are much more elongated, and seem to conduct the
elaborated food stuffs from one part of the plant to the
other, true sieve tissue sometimes being present. A
system of water-conducting tissue is not evolved until
the Mosses are reached. Here the center of the stem is
occupied by elongated cells, that serve probably in part

VASCULAR BUNDLES 55

as water-conducting cells, in part probal^ly for support.
Around these are somewhat elongated thin-walled cells
that are possibh^ food-conducting in function.

78. It is in the higher plants, however, the Ferns and
Fern Allies and Seed Plants, that a true conducting
system is developed. This consists usually of strands of
tracheary and sieve tissue, each associated with some
living parenchyma cells, passing longitudinally through
the stems and roots and out into the leaves. These
strands are called vascular bundles.

79. A vascular bundle consists of two parts which are
distinguished both structurall}^ and functionally. Xylem
is the name given to that part of a vascular bundle
consisting of the tracheary tissue and the parenchyma
associated with it. Its function is primaril}- water-
conducting. The phloem, on the other hand, consists
of the food-conducting sieve tissue, with the accom-
panying parenchyma in the form of companion cells,
sieve parenchyma, etc. Frequently fibrous tissue is
found intimately connected with the xylem and phloem,
usually in the form of wood fibers with the former and
bast fibers with the latter. In such a case, we find the
supporting S3'stem to be partially united with the
conducting system.

80. The vascular bundles originate in the growing
points by the conversion of certain of the rows of meris-
tem cells into strands of elongated, rather narrow cells.
These, bej'ond elongating considerably and dividing
longitudinally so as to become narrow, retain their
meristematic character long after the surrounding
tissues have acquired the more permanent forms.
They are then kno\vn as procambium or as procambial
strands. Eventually, the cells composing them bc^gin to
change into the permanent tissues, these changes

56 GROUPS OF TISSUES, OR TISSUE SYSTEMS

taking place first in a few cells and finally including all
the procambium in the so-called closed bundles or
leaving a sheet of unchanged meristem between the
xylem and phloem in the so-called open bundles.

81. Classifying them by the relative positions of the
xylem and phloem parts of the bundle, we may dis-
tinguish three main types of vascular bundles, radial,
concentric, and collateral. In the radial type, the
xjdem is present in two to many radially situated, more
or less flattened strands, which may or may not reach
the center. Alternating with these are the masses of
phloem. In the concentric type, the xylem is central

and is surrounded by an al-
most continuous layer of
phloem, or much more rarely
phloem and xylem have re-

FiG. 23.— Plans of radial, concentric, Verse pOSitioUS. In the Col-
and collateral vascular bundles. , . , , , , ,

lateral type, the xylem occu-
pies one side of the bundle (usually that toward the
center of the stem), and the phloem the other side
(usually the centrifugal side).

82. The radial vascular bundle is typical of roots.
It occupies that part that was marked off as plerome at
the growing point. Bounding it is a layer of rather thick-
walled cells, often with suberized or cutinized walls, the
endodermis (or bundle sheath) . This is actually the inner
layer of the cortex, and is not really a part of the bundle
itself. Within this is a delicate layer of thin-walled cells,
the pericycle (or pericambium). Bordering on this,
or in some families of plants interrupting it, and therefore
touching the endodermis, are the xylem strands. These
are made up of tracheary tissue. The elements vary in
size, the smallest (those first differentiated from the pro-
cambium) being those next to the pericycle, those lying

RADIAL, AND CO^X'EXTRIC BUNDLES 57

nearer the center being gradually larger. The various
xylem strands may meet in the center in one large vessel
or in a mass of tracheary elements, or the center may
consist of parenchyma, or of sclerenchyma, or even of
fibrous tissue. Midway between the xylem strands,
and like them bordering upon the pericycle are smaller
or larger phloem masses, consisting
mainly of large sieve tubes, and small
companion cells, and other parenchyma
cells. The tissue between the phloem ^^^ 24— Half of
and xylem strands may be parenchyma | radial vascular
or in part fibrous or sclerenchyma.

83. Lateral roots arise by the conversion of portions
of the pericycle into active meristem cells which soon
become arranged in definite layers, as in the growing
root tip. This rootlet forces its way out through the
cortex until it reaches the outside. The plerome part
becomes the vascular bundle whose tracheary and sieve
elements are connected respectively with the xylem and
phloem strands of the main bundle.

84. The concentric type of bundles is found mainly

in the stems and leaves of Ferns and
Fern Allies. In these plants the stem
usually possesses several vascular bun-
dles, which may be variously located
Fio. 25.— Concentric ^ud of different shapes and cross-

vascular bundle. '■

sections. They branch more or less
frequently and in some cases anastomose very freely.
Some of the bundles pass out from the stem into the
leaves, there to branch again to form the veins. In
general, the bundle consists of a plate of xylem, sur-
rounded on all sides or on all except the edges of the
plate, by large sieve tubes and small parenchyma cells.
Around these are often one or more layers of starch-bear-

5S GROUPS OF TISSUES, OR TISSUE SYSTEMS

ing cells, with usually a thick-walled bundle sheath about
the whole. In some species of Lycopodium there are
several plates of xylem alternating with phloem, with
one bundle sheath around all. Transitional forms are
found between this type and the radial type of bundle on
the one hand and the collateral on the other.

85. The collateral type of bundle is present in stems
and leaves of Seed Plants, and of many of the Fern Allies.
Three types may be distinguished, open collateral,
closed collateral, and bicoUateral. The first two differ
in the presence or absence, respectively, of a layer of
meristem cells (cambium) between the xylem and phloem,
while the third type is characterized by the presence of
a layer of phloem on the inner, as well as on the peripheral
side of the xylem.

86. The closed collateral type of bundles is especially

characteristic of the class Monocotyle-
doneae. It is usually associated, also, with
a scattered arrangement of the bundles in
the stem. There is usually less anas-
tomosing of such bundles with each other
than is the case in the open collateral type.
Fig. 26.— This type is present in some of the Dicotyle-
vlsculr^bundie!^ doneac as well, but not so frequently as the
open collateral type. As an example that
may be easily obtained to study, the vascular bundle
of Indian corn may be taken. In this the xylem portion
shows, in cross-section, four (rarely three or five) large
vessels, of which two (annular or spiral) are placed in
the radial plane, and the other two (large pitted vessels)
lie a little externally to and to the right and left of these
two. Between these large pitted vessels, and bordering
the outermost of the other two vessels, is a mass of smaller
cells, sometimes fibrous, sometimes tracheary in nature.

COLLATERAL BUNDLES 59

The innermost vessel borders a large intercellular air
space. Partly enclosed between the large ]Mtted vessels,
but in the main placed peripherally to the X3dem, is
the phloem. In cross-section this is elliptical and
consists of large sieve tubes and small companion cells.
The whole bundle is surrounded by a mass of cells, mainly
fibrous. No meristem tissue is present at all in the com-
j:)leted bundle.

87. Open collateral vascular bundles can be found
most typically in the class Dicotyledoneae, though they are
also present in the Strobilophyta and related groups.
In the stem they are usually placed almost equidistant
from the center, surrounding a central mass of paren-
chyma, the pith, and separated from each

other laterally by the masses of paren-
chyma (primary medullary rays), which
connect the pith to the cortex. The ten- t^TYK^^
dency to anastomose is very great in open
collateral bundles, so that these medullary p^^ 07—0 en
rays are interrupted above and below at cuilTrTundk "^ ^ '
frequent intervals, and are not continuous
for a long distance in the stem. Bicollateral bundles of
the open collateral type are similarly placed in the stem.

88. When first completed, the xylem portion consists
of two or three to several rows of tracheary tissue, usually
not crowded but loosely placed with reference to each
other, and with the spaces filled in with parenchyma.
The outer boundary of the xylem is parallel to the
surface of the stem, and is succeeded by a layer, one to
several cells thick, of meristem, the so-called cambium.
Bounding this externally is the phloem region, consisting
at first of sieve and companion cells and other par-
enchyma tissue, and sometimes even of masses of bast
fibers. In young woody stems there may be considerable

60 GROUPS OF TISSUES, OR TISSUE SYSTEMS

fibrous tissue among the tracheary tissue. In bicol-
lateral vascular bundles, the inner mass of phloem is not
separated from the xylem by a cambium layer.

89. Wherever a leaf is attached, one or more vascular
bundles in the stem pass out into it. These usually run
downward in the stem for some distance before they
unite with the other bundles there. In the leaf the
phloem portion is downward (i.e. toward the back of the
leaf), and the xylem mass uppermost. Here the bun-
dles are the so-called 'Veins." At first
they are much like the stem bundles,
although usually the cambium is lack-
ing, but the more they are divided, the
smaller and simpler they become until
finally they may consist of only one or
two rows of tracheids, a single row of

of a°vas^cuiTr^bu1idfe. slcvc cells, and a row of companion cells,
with a few thin-walled parenchyma cells
surrounding the whole. In some cases these bundles
end blindly in the parenchyma of the leaf. In other
cases they meet other similar bundles and so form a net-
work with no free ends.

90. Secondary Thickening. The fact that in the for-
mation of the open collateral bundles from the pro-
cambial strands of meristem tissue, a portion of the
meristem remains unchanged as the cambium layer,
separating the xylem and phloem, makes it possible for
the bundle to continue to grow in thickness. This it
does by the growth and periclinal division of the cambium
cells, and the transformation of the inner cells thus
formed into xylem and of the outer ones into phloem,
continually leaving, however, an intermediate portion of
cambium which can grow and divide further.

91. The xylem formed during the process of secondary

SECONDARY THICKENING 61

thickening diflers usually quite materially from the pri-
mary xylcm. It contains much more fibrous tissue, is
more compact, and forms a true wood. The phloem
also is interspersed with more bundles of bast, and may
by its formation soon crush out of recognizable shape the
primary phloem. In addition, the tissues forming the
primary medullary rays become active. The layer of
parenchyma cells that connects the edge of the cambium
of one bundle with that of the next bundle becomes
itself converted into cambium by the accumulation of
large amounts of cytoplasm in the cells, and the formation
of periclinal walls. Part of this interfascicular cambium
thus formed gives rise only to cortical and medullary
parenchyma, but at intervals new bundles arise by the
formation of xylem and phloem, respectively, on the
inner and outer faces of the cambium layer. Thus, sec-
ondary bundles are formed, which divide the medullary
rays longitudinally, and as the bundles become more and
more numerous, these primary rays may
eventually be reduced to thin plates of paren-
chyma, only one or two cells thick, and per-
haps only a few cells wide (measured in ver-
tical direction), but still extending from the
pith to the cortex. Additional (''second-
ary") medullary rays are formed within the Fiq. 29.—
bundles when certain cambium cells cease grmvth of l*^'"-
to form xylem elements and from that time
forward produce parenchyma cells. These secondary
medullary rays usually arise at varying distances from
the center, a certain number of new ones being laid down
each 3'ear.

92. Where the growth is continuous and (Hjual. the
wood is usually of fine grain and uniform. Most woody
plants of the temperate zones, however, and of those

62 GROUPS OF TISSUES, OR TISSUE SYSTEMS

portions of the tropics where there are marked wet and
dry seasons have annual growth periods, separated
by seasons, where growth ceases entirely or nearly so.
In such cases the first part of the xylem laid down each
year consists of a greater proportion of tracheary elements
and fewer wood fibers, the proportion of the latter in-
creasing as the season progresses. The wall of each
successive fiber is thicker and the lumen smaller.
Such tracheae as are produced later
in the season are smaller than those
first formed. The contrast of these
small thick- walled numerous wood
fibers, produced at the close of one
season's growth, and the large lu-
mened tracheary and wood cells
Fig. ao.^th^wth rings formcd at the beginning of the next,
in .tern of oak ^^^^^ ^ ^^^^ distinct line and

marks off the growth rings, which, as they are usually
annual, are of great value in determining the age of a
tree.

93. Usually the wood nearest the center of a tree
undergoes changes after it has reached a certain age.
Among these changes are the deposition in the lumina
of the cells of various organic substances, which seem
to make the tracheary elements no longer able to carry
water, and the death of all living cells (e.g. cells of medul-
lary rays, wood parenchyma, etc.), and often a change in
color. Such wood is called heart wood, to distinguish
it from the water-conducting sap wood, in which the
medullary rays and wood parenchyma cells are still alive.

Laboratory Studies, (a) By studying successive thin cross-
sections of the stem, bej^innin^ at the growing point, there will
be found the procambial strands, which give rise to the vascular
bundles. They appear, in cross-section, as masses of cells of

LABORATORY STUDIES 63

small diameter. Further down, part of these strands will be
found to consist of tracheary tissue.

(b) Study a vascular bundle of the radial type, by making
cross-sections of the larger roots of corn, iris, hyacinth, or of
the main roots of seedlings of bean, pea, sunflower, etc. Note
the number of xylem i)lates, location and extent of phloem, the
endodermis, pericycle, etc.

(d) Using a bean seedling, in which lateral rootlets have
begun to show, make numerous cross-sections, so as to find such
rootlets in various stages of development, and study their or-
igin and mode of emergence.

(e) The concentric type of bundle may be studied best in
cross-sections of the rhizomes of the brake {Pteridium aqni-
linum). Make a longitudinal section also, so as to identify the
tissues present.

(/) Vascular bundles that may perhaps be assigned to the
concentric type may be studied in cross and longitudinal
sections of the stems of Selaginella and Lycopodium.

{g) Make cross and longitudinal sections of the stem of
Indian corn, sugar cane, Smilax hcrbacea, or other mono-
cotyledons, for vascular bundles of the closed collateral type.
Note their distribution in the stem.

(h) Open collateral bundles may be studied to advantage in
the younger internodes of clover and alfalfa, or the upper ones
of sunflower. Note the arrangement of the various xylem
elements. Note how the l)undles are distributed in the stem.

(i) Study the lower internodes of the same j^lants, for secon-
dary thickening. Note the differences between the secondary
xylem and that formed in the bundle before the secondary
thickening had begun. Note the secondary vascular bundles,
interfascicular cambium, etc.

(j) Make and study a cross-section of a two-year-old twig of
basswood, elm, or other tree. Note the growth rings, and in
cross and longitudinal sections determine their structure.
Study the })rimar3' and secondary medullary rays.

{k) For bicollateral vascular bundles, the best objects are
the stems of Cucurbitaceae, e.g. squash, cucumber, etc.,
although they are found also in the Solanaceae, e.g. young(>r
parts of the stems of petunia, potato, etc.

64 GROUPS OF TISSUES, OR TISSUE SYSTEMS

(/) Reduced bundles and bundle endings can be studied in
leaves and petals by placing them in some clearing fluid, e.g. a
mixture of phenol (carbohc acid), and turpentine after 15 to 20
minutes' treatment with 95 per cent alcohol. Mount in the
same fluid and examine under low and high powers. If these
objects are previously placed with their cut ends in an aque-
ous safranin or eosin solution until the colored Hquid has
filled the bundles these are more conspicuous.

(w) Examine the cut ends of logs and stumps of various kinds,
to distinguish the heart wood and sap wood. That they are
different in some of their chemical characteristics will be shown
by their different proneness to decay.

94. The Supporting System. In many plants the
supporting and conducting systems are intimately
connected, the vascular bundles containing not only the
conducting cells but also an abundance of wood and bast
fibers. However, at first the stems are often supported
by other means. Thus, a strong development of
coUenchyma strands under the epidermis is a very com-
mon occurrence. By the natural turgor and growth
of the stem, these collenchyma strands are stretched,
and thus stiffen the stem until the fibrous tissues
are developed later in connection with the vas-
cular bundles. In the cortex, bast bundles are fre-
quently encountered, inde-
pendent of any vascular
bundles. In the stems of
Ferns and Fern Allies, large
bundles of fibrous tissues are

(3) scattered here and there.
Closely allied to the support-
ing system of tissues, in function, are those tissues that
serve for protection, as for example, the sclerenchyma,
deposited in various parts of the plant, such as the
bark, roots, fruits, and seeds.

Fig. 31. — Supporting system
stems of 'fl) moss, (2) fern,
flowering plant.

NUTRITIVE TISSUES

95. Ill addition to the conducting and supporting
systems, the remainder of the plant serves various
functions. Thus, a large portion of green plants con-
sists of nutritive tissues. These are usually found in
leaves, but are also present in the younger parts of stems.
In leaves we can usually distinguish, underneath the
upper epidermis, one or more rows of closely packed
cells, with their long axes perpendicular to the surface
of the leaf, forming the so-called pali-
sade parenchyma. In leaves equally
lighted on both sides, this palisade
parenchyma is often formed on both
surfaces. Below the palisade layers
the assimilative cells are looser, form-
ing the "sponge" parenchyma, with
larger intercellular spaces between them,
which connect with the exterior through the stomata.

96. The system of intercellular spaces is quite marked
in all higher plants. These passages are usually con-

32.— Section of
a leaf.

Fig. 33. — Large intercellular spaces in

■r-lily petiole, and rush stem.

tinuous through the petioles of the leaves into the stems
and down into the roots. In plants growing in swampy
places or in water these intercellular spaces are very
much enlarged and apparently serve the double function
of providing an ample air supply to the submerged por-

6G GROUPS OF TISSUES, OR TISSUE SYSTEMS

Fig. 34.— Starch
storage cells of
potato.

tions of the plant and of giving buoyancy to the part in
which they occur.

97. Another important function of tissues is that of
storage of food substances. Storage tissues are usually
composed of large parenchyma cells
with large central vacuoles and compara-
tively' little protoplasm. In some special
cases where the storage product is one
of the hemicelluloses this is deposited
against the cell wall forming a sort of
sclerenchyma tissue.

98. In many plants are found secretory
cells. These often line closed cavities
(or ''reservoirs") or elongated passages. These cavities
or passages may be formed simply by the pushing
apart of certain cells as the secretion is poured into
the space between them (i.e. produced schizogenously)
or certain cells may be dissolved, forming ''lysigenous"
cavities. Good examples of
the first type are shown by
the gum canals of the ivy
{Hedera helix) and the tur-
pentine canals of conifers or
the glands of the leaves of St.
John's wort (Hypericum).

In the leaves and fruits of Rutaceae the cavities more
often arise by the dissolving of the secretory cells thus
setting free the secretion within a cavity. The secretions
are usually gums or ethereal oils, often containing resins,
etc. Other cells containing crj^stals of calcium oxalate
and other substances, perhaps including tannin, may
possibly be classed as excretory organs in which the
excretions are stored up in the absence of any structure
that would permit their being thrown out of the plant.

Fig. 35. — Gum and turpentine
canals of ivy and pine.

CORK 67

Externally there ma}- be developed secretor}^ structures
such as the nectaries of flowers, etc.

99. Cork. At first the cutinized external wall of the
epidermis of the stem serves to prevent excessive water
loss. When the stem enlarges the increased circumfer-
ence is met by the enlargement or multiplication of the
epidermal cells. There is a limit, however, for most
stems to this epidermal growth and furthermore as the
stem becomes enlarged the one layer of cells is no longer
sufficient protection against water loss and especially
against mechanical injury. There is accordingly formed
beneath the epidermis a layer of meristem cells called
phellogen or cork cambium, which gives rise (by periclinal
divisions) to radial rows of cells without intercellular
spaces, whose walls become strongly suberized by the de-
position within them of a _______

fatty substance or substances P^r^^^ ^^-^^^~^>""---v^
called suberin, which makes ^Eizt ^'^^--^ Ij^A
them impermeable to water. ^B=^H /" ^\ ^A
The cells die shortly after sub- ^^^^^
erization occurs and remain Fig. 36— Cork (i), subepidermal,
filled with the broken-down

protoplasm or become filled with air. These layers of
cork cells, owing to the suberization, cut off the passage
of water toward the exterior and the epidermal cells
accordingly die. With the growth of the stem in
circumference these are soon ruptured here and there
and gradually peel off. Since the outer cork cells are
also dead they cannot enlarge and so as the stem
grows longitudinal fissures occur in the cork extending
down nearly to the living phellogen, which however
being alive is able to increase in circumference and
thus keep pace with the increasing circumference
of the stem. Sometimes this phellogen layer is per-

68 GROUPS OF TISSUES, OR TISSUE SYSTEMS '

manent but more often a layer of cells starting at the
phellogen and dipping inward into the cortex and finally
back to the phellogen also becomes converted into
phellogen and begins to produce cork. The more or
less lens-shaped mass of tissue cut off by this process
promptly dies from lack of water and eventually scales
off. Thus is formed the flaky type of bark. This proc-
ess is repeated time and again so that the bark remains
only about the same thickness, no matter what the age
of the tree.

100. Lenticels. As cork is about to form, a phellogen
of special type arises under many of the stomata on the

young stems and twigs. This forms
a loose mass of cork with large inter-
cellular spaces connecting through
the intercellular spaces in the phel-
logen (these being lacking in ordinary
Fig. 37.— Lenticels. phcllogeu and cork) with those of the
cortex. This mass of cork cells rup-
tures the epidermis and forms a minute lens-shaped
fleck. These lenticels function then as openings for the
exchange of gases while at the same time the mass of
loose cork cells greatly reduces the water loss.

101. In addition to the foregoing cases cork is also
formed in many plants as a result of wounds. The
injured cells die but those immediately or but a short
distance below become converted into phellogen which
produces a cork layer that forms an effective barrier
against further water loss and probabl}^ also prevents in a
large measure the entry of foreign organisms. Fre-
quently this cork thus formed serves as an abscission
layer, i.e. it splits, and permits the dead tissues to slough
off. The layers normally found at the base of the leaf
petiole in the autumn are of similar nature, serving to

LABORATORY STUDIES 69

permit the fall of the leaves and at the same time
covering the exposed surface with a cork laj-er which
prevents the loss of water or entry of harmful organisms.

Laboratory Studies, (a) Examine the cross-section of a
very young twig of elder or of a young stem of lamb's quarters
{Chenopodium album) and note the supporting system which
at this stage consists of longitudinal strands of stretched
elastic collenchyma just under the epidermis.

(b) In older parts of the stem of the same plant note how the
main supporting function has been assumed b}^ the wood fibers
associated with the xylem of the vascular bundles and by
strands of bast fibers sometimes closely associated with the
phloem of the same bundles and sometimes independent of any
bundles.

(c) Make a cross-section of a leaf of beech or lily or other
plant and examine. The special nutritive palisade tissue is
present next to the upper epidermis. In the lower part of the
leaf note the ''sponge" parenclwma with its large intercellular
spaces. The leaf of cottonwood (Populus sp.), compass plant
{SUphium laciniatum) , etc., will show palisade tissues on both
sides.

((/) ]\Iake a cross-section of a stem of a water lily (Castaha,
Nelumbo, etc.) or of a rush (Juncus) or of some other semi-
aquatic or aquatic plant. Note the large intercellular spaces.
Note also the rather small development of water-conducting
tissues.

(e) For examples of tissues devoted to storage purj^oses
study sections of a tuber of potato, root of sweet potato, i)ith
of twig of apple or sassafras, seed of date, etc.

(/) Make a cross-section of the stem of iv}^ {Hedera hcU.r)
for gum canals lined with secretory cells. Similar canals in the
wood and leaves of Conifers (pines, spruces, etc.) contain
turpentine.

(g) Make a cross-section of the leaf of St. John's wort
(Hypericum) or leaves or fruit of the orange or lemon (Citrus)
for secretory reservoirs ("glands") in the tissue.

(h) Examine various flowers and study the location and
structure of the nectaries. Extra-floral nectaries may 1)C found
on leaves of various plants, e.g. some of the plums. Other

70 GROUPS OF TISSUES, OR TISSUE SYSTEMS

types of glands maj- be found on the "tentacles" of the
leaves of the sun-dew (Drosera).

(i) Section a very young twig of basswood (Tilia) or elm or
other tree and note the epidermis. Compare this with a one
or two year old twig of the same tree and note the cork forma-
tion. Studv cross-sections of various kinds of tree trunks and
note the different types of cork formation in these.

ij) On a young twig of elder (Sambucus), snowball (Vibur-
num) or birch (Betula) section the lenticcls in different stages
of development and study them.

(k) In the autumn make longitudinal sections through the
base of the petiole of leaves of maple, elm or other deciduous-
leaved trees. If made at the proper place and time the cork-
like abscission layer may be found.

REFERENCE BOOKS
The books enumerated for Chapters I and II.

CHAPTER IV
PLANT PHYSIOLOGY

102. Plant Physiology has for its subject the study
of the activities of the plant and of its parts. It is not
sufficient to learn about the morphology, i.e. the external
and internal structure; we must also seek to learn what
the different parts are for, how the plant carries on its
activities and the relations of the plant to the external
surroundings. In the preceding chapters the functions
of the parts have been mentioned briefly in connection
with the special structures. In this chapter, it is sought
to take up the plant activities as a whole. Much of
what is here given can be used by the skillful teacher at
the same time that the foregoing chapters are being
studied.

Plant Physiology will be treated under the following
heads: (1) Nutrition, (2) Growth and Reproduction,
(3) Movements. To these will be added (4) a short
consideration of the Pathology of Plants.

103. Nutrition, in its widest sense, includes the taking
in and giving out of water and other substances, their
transportation from one part to another in the plant,
their use in the plant in the formation of food, the use
of this food, and the energies required or set free in all
these processes.

104. The most important single substance taken in
by a plant is, beyond doubt, water. The driest plant
parts, such as seeds, possess from 5 to 10 per cent, or
more of water while leaves may possess 75 per cent, or

72 PLANT PHYSIOLOGY

even greater amounts. Flesh}' fruits like the pear and
grape contain still larger amounts. Algae are extremely
watery, the amount of water in Spirogyra probably ex-
ceeding 97 per cent. This water is present not only
in the vacuoles but also in the cell wall and protoplasm,
both of which have the property of imbibing water to a
considerable extent. Thus even lignified cell walls may
have one-third of their weight as water and protoplasm
is probably not active unless 75 per cent, or more water
is contained in it.

105. This water is almost continuous throughout the
whole plant, so that we may think of a plant as a mass
of water of the shape of a plant with the interstices oc-
cupied here by molecules of cell wall substance, there by
protoplasm, the water being continuous also with the
water surrounding the roots in ordinary plants, or the
whole plant if it is aquatic.

106. Although the water is continuous throughout
the plant, it is held more abundantly in some parts than

others, and may be in motion within
the plant. The entry of water into a cell
is through the process called osmosis.
The plasma membrane of the cell is a
semipermeable membrane which is almost
Fid. 38.— A tur- perfectly permeable to water but almost
moiyz^ed^ceu. ^'^^" impcrvious to somc of the substances in
solution in the water of the cell. Under
such circumstances, if the solutes inside the cell are more
concentrated than those outside, the molecules of water
pass more rapidly into than out from the cell and it
becomes filled with water. The protoplasm is pressed
against the cell wall and this stretches until it may be
increased in area in some cases by as much as 50 per cent.
This stretching continues until the wall can stretch no

PASSAGE OF WATER 73

more or until the counter pressure of the stretched walls
equals the osmotic pressure (i.e. the power with which,
under the given difference in density of the outer and
inner solutions, the water from the outside tends to
enter the cell). Such a water-distended cell is said to be
turgid or in a state of turgor. The pressure within it
may equal several atmospheres. Jost gives this pressure
for some desert plants as equalling one hundred atmos-
pheres, i.e. about 1500 pounds per square inch.

107. If a cell be in contact with a plentiful water
supply, it will become as turgid as the difference in
osmotic pressure outside and inside will permit. If a
cell adjacent to it is not in contact wdth the external
water, there will be a passage of water from one cell to the
other, the direction depending upon which cell has the
denser solution in its cell sap. Thus, in a plant with one
part exposed to evaporation into the air and with
the other part in water there will be a constant passage
of water into the plant and up through it from cell to
cell, by osmosis, and out into the air by evaporation from
the wet surface of the cell walls.

108. In larger land plants, however, this rather slow
passage of water from one cell to another b}^ osmosis is
too slow to supply the aerial parts with the requisite
amount of water. Such plants possess special elongated
cells no longer living and often with the separating
partitions dissolved out, viz. : the tracheae and tracheids.
(See paragraphs 46 to 49.) These serve as tubes
through whi(^h the water rises, not as a simple diffusion
of molecules but with a mass motion, i.e. as a definite
current carrying with it whatever miiy be dissolved.

109. In these plants then we can trace the water
through the following steps of progress. It enters the
root hairs by osmosis from the surrounding soil where it

74 PLANT PHYSIOLOGY

is present in thin or thick films around the soil particles,
the entry being molecule by molecule. It passes by
osmosis from cell to cell through the cortex of the root
until the tracheary tissue of the vascular bundle is
reached. It enters these vessels (just by what force is
not clear) and ascends through them (also by what force
is uncertain). Some of it is taken out
by osmosis, by various parenchyma
cells (e.g. medullary rays) bordering the
tracheary tissue and passed osmot-
ically to the various tissues at that ap-
proximate level, but the bulk passes
on out into the leaves w^here it is taken

Fig. 39. — Course of , • • ^ n i n

w a t e r into, and by osmosis mto the parenchyma cells.

through a land plant. -^^ ,, n i i • ii i

From the cells bordermg the larger air
spaces, it evaporates into these and passes as vapor out
through the stomata.

110. The evaporation of water from a wet membrane
(e.g. cell wall) makes available a large amount of energy
for lifting up water to replace that evaporated. It has
been shown that the energy thus available in a leaf is
many times more than that necessary to lift the water
up to the tops of the highest trees (150 meters). How-
ever, though the energy is ample, the air pressure at sea
level is only sufficient to lift water not quite ten meters
into a vacuum. The osmotic pressure developed in
roots that are rapidly absorbing water is enough oc-
casionally to lift water to a height of eleven meters in the
grape and even twenty-five meters in the Birch (Betula
In tea). The distance that this root pressure will lift
water plus the height air pressure will lift water into a
vacuum fall far short of the distance water must be
lifted in tall trees. It has been suggested that perhaps
the cohesion that exists in water in narrow vessels

PATH OF WATER 75

(e.g. in tho trachoaiy tissues) is sufficient to pull the
water u]) from tlio lowest roots. Other investigators
have suggested that some of the living parenchyma cells
which accompany all water-conducting tracheids and
tracheae are concerned in the lifting of the water (or
ascent of sap as it is often called).

111. Path of the Water. This is chiefly in the cavities
(lumina) of the tracheary tissue. It is also not to be
denied that the w^ater will pass upw^ard slowly from the
roots, passing from cell to cell in the parenchyma by
osmosis, for the tissues above ground have more con-
centrated solutions, and so bring about osmosis from the
root cells with their less concentrated solutions. This is,
however, not sufficient to supply an ordinary plant.
Within the tracheary tissue, the lumen contains not only
water but some bubbles of air, past which the water flows
in a thin film next to the cell wall. In trees the central
wood after a number of years suffers deposition of resins
or other insoluble substances within the cell cavities and
possibly walls as well, so that w^ater conduction is no
longer possible. Such wood is often different in color
and is called heart wood and contains no living cells.
The unchanged wood around it, the sap wood, contains
dead water-conducting tracheary tissue, dead fibrous
tissue and living wood parenchyma.

112. The evaporation of water from the leaves and
stems is often given the name transpiration. It is an
unavoidable loss since the plant must have openings,
the stomata, through the epidermis, for the purpose of gas
exchange and when these are open the loss of water can-
not be jH-evented. The thickening of the cuticle in
plants of dry regions, the depression of stomata in the
pits to provide dead air spaces outside, the formation of
thick layers of hairs, etc., all indicate that it is not to the

76 PLANT PHYSIOLOGY

advantage of a plant, to have transjnralion taking place
but just the contrary.

113. The amount of water given off by transpira-
tion is very large. The water loss from a Birch tree,
standing alone and estimated to have 200,000 leaves was
calculated by von Hohnel at about 500 liters on a very
hot dry day and about 60 to 70 liters on average days.
An acre of hops will evaporate three million to four
million liters of water in a season. Dietrich estimates
that for every gram of dry substance found in a plant,
from 250 to 400 grams of water have been evaporated.
In twelve hours, a grape leaf evaporates as much water as
would form a film 0.13 mm. deep over the whole leaf,
while for cabbage and apple leaves in the same length of
time the figures are respectively 0.31 and 0.25 mm.
In one season, an oak tree, during the time it holds its
foliage, evaporates an amount equivalent to 33 mm. over
all its leaves. An open water surface would evaporate,
in the same time, 500 to 600 mm., showing that the
evaporation (transpiration) is far less from the leaves
than from a free surface.

114. It has been show^n that an impermeable surface
with very numerous openings, as for example, the
epidermis with its numerous stomata, evaporates nearly
as much water as if it were a free water surface. The
stomata, however, are capable of closing and thus almost
wholly preventing water loss for such periods of time as
they may remain closed. At night they are nearly
closed. When the plant begins to wilt, it has been
shown that they also close automatically through re-
duced turgor of the guard cells thus preventing too great
a loss of water. All physical phenomena which increase
evaporation also increase the water loss from the leaves
as long as the stomata remain open, e.g. increased

GUTTATIOX 77

temperature and dryness of the surrounding air, sun-
shine, etc.

115. Many plants exude water from specially modified
stomata (the so-called water pores) at the edges of the
leaves when the movement of water upward has been
strong and then, by increase of the humidity of the air,
the evaporation has been checked rather suddenly.
This may take place in the form of drops or even as a
fine stream. It is called guttation. Its mechanics and
use are not clear.

Laboratory Exercises. Note : In a large class, many of these
experiments cannot be performed by every student. In that
case the instructor should assign some experiments to one
student, others to another throughout the class or should set
up the experiments himself before the class. In either case,
every student should make complete notes upon the experiment
for himself.

(a) Weigh a handful of freshly picked leaves quickly before
they have begun to wilt. Place them in an oven at the
temperature of about 110° C. and dry them for twelve to
twenty-four hours. Now weigh them and note the loss in
weight. This is almost entirely due to the evaporation of the
water in the leaf. Calculate the percentage of water in the
original weight. Repeat the experiment with various parts of
the same plant such as stems, roots, flowers, fruit, seeds, etc.,
and compare the amount of water in these different parts as
well as with the corresponding parts of other plants.

(b) To demonstrate imbibition by cell walls, take a measured
block of wood 5 or 6 cm. long and 3 or 4 cm. square. Measure
it when perfectly dry, i.e. after having been kept a day or two in
an oven at 110° C. Then soak it in water (preferably warm or
hot, to hasten the process). Now measure accurately. The
piece will be found to have become perceptibly larger owing to
the imbibition of water by the cell walls. Probably the first
entrance of water into dry seeds is also due to imbibition of
water by the cell walls and protoplasm. As soon, however, as
the latter has imbibed enough to become hquid, osmosis
begins to act also in the taking in of water.

78 PLANT PHYSIOLOGY

(c) Osmosis may be demonstrated by tying a piece of fresh
bladder securely across the mouth of a thistle tube which is
inverted and filled with a strong solution of sugar up to a mark
on the stem. The larger end with the bladder is now placed
in a dish of water so that the water outside stands at the same
height as the water inside. The water will enter through the
bladder by osmosis and ascend the stem, perhaps reaching a
height of a meter or more above the level of the water outside.
The more impermeable the membrane is to the substance in
solution while still remaining permeable to water, the greater
the difference in level and the higher the pressure
that can be obtained. The latter can be measured
roughly by connecting the stem of the thistle tube to
a mercury manometer.

(d) The relation of osmosis to turgor may be demon-
strated by making an ''artificial cell." Fill a test
tube with a strong sugar solution and tie a piece of
bladder firmly over the open end. Place in a dish of
water. The water that passes into the tube by osmo-
sis through the bladder causes the latter to be
stretched and to bulge out. On removing the tube from the
water, and pricking the bladder with a pin, the pressure
developed by the stretching of the bladder will force the water
out in a stream.

(e) Mount one or two filaments of Spirogyra in water and
examine. Measure the length of a portion including a definite
number of cells. Now draw a 2 per cent, potassium nitrate
solution or a 5 per cent, sugar solution under the cover glass by
adding it at one side and withdrawing the water from the
other side with a piece of filter paper. Measure the filament
again. Add increasingly strong solutions and when the right
strength is reached, the cytoplasm will be found to be drawing
away from the corners of the cell wall, i.e. plasmolysis has
begun. This indicates that with the withdrawal of water by
the solution outside, the much stretched cell walls have lost
their tension until they have reached a state in which they are
not at all stretched. As the water is still withdrawn from the
cell, the cytoplasm is pulled further and further away from the
wall. At this stage, again measure the fdament and calculate
the amount that the turgid filament was stretched.

(/) To demonstrate that evaporation from a membrane filled

LABORATORY STUDIES 79

with water has a strong Hfting power, cover the end of a thistle
tube tightly with a piece of bladder or fill the mouth with a
tightly fitting thin layer of plaster of Paris. Invert the tube
and fill completely with water that has been boiled to remove
the air so that bubbles will not be produced in the tube. Invert
again with one end of the tube in a dish of mercury. Wet the
bladder or plaster of Paris plug externally. As evaporation
progresses, the mercury will be drawn up into the tube until a
point is reached where the pressure of air on the outside of the
bladder or plaster of Paris is sufficient to force the water
back out of it so that it is no longer wet. It then permits air
to pass through rapidly and the mercur}'- soon recedes to its
original level. Similarly, it is assumed that the
evaporation of water from the wet cell walls into the O
intercellular spaces of the leaves exerts a strong lift-
ing power on the water in the stem of the plant.
This will be shown by the following experiment.

(g) Cut a leafy twig and fasten it, without allow-
ing the cut end to dry out, into a glass tube filled fig. -ti.
with water and with its lower end in mercury. This — Evapora-

/•I'lii • e ''''"^ experi-

expernnent, if successful, will also show a rise of mer- mem (/).
cury in the glass tube as in the preceding one.

(h) Place the cut end of a stem (preferably a herbaceous one)
in a strong aqueous solution of safranin. After an hour or so,
make cross-sections at various points. The colored solution
will be found in the tracheary tissue (and after longer standing
also in some of the immediately surrounding tissues, especially
in wood fibers).

(i) Place a branch which has been girdled (i.e. the bark
removed to but not including any of the wood) with its lower
end in water, the girdled area being protected from drying out
by coating with grafting wax or paraffin. Compare with a
similar branch not girdled. Take a third branch and through
a small slit in the bark cut off the wood entirely with as little
injury to the bark as possible. Place it in water like the other
two. Note the differences in the rapidity of wilting in the
different cases.

(j) Take a potted plant, e.g. a geranium or begonia, and
after watering it well, envelop the pot in a sheet of rubber,
tying the rubber firmly about the stem of the plant. Instead
of using the rubber, the outside of the pot and the top of the

80 PLANT PHYSIOLOGY

soil may be made practically water proof by means of melted
paraffin whose melting point is sufficientl}'' low so as not to
injure the stem when applied to the top of the soil in a melted
condition. Weigh the pot and place in a dry room for an hour
and weigh again. Calculate the loss of water per square
centimeter of leaf surface. Place in a moist room under the
same light conditions as before and note the loss of weight in an
hour. Such experiments are not accurate as many factors
enter in to interfere, but they give an idea of the approximate
amount of water evaporated. The experiment may be
continued a long time by providing an opening in the rubber or
paraffin through which a thistle tube passes and adding every
twenty-four hours as much water as was lost in the preceding
2-4-hour period. By keeping a record in this way, the amount
of water lost in a week can be determined roughly. (Of course
the increase in weight of the plant itself as it grows is a factor
not taken into consideration in the foregoing nor the effect
upon the roots of the partial exclusion of the air by the rubber or
paraffin.)

(k) To show that it is mainly through the stomata that
evaporation (transpiration) occurs, take three lilac leaves of as
nearly equal size as possible. Coat the ends of the petioles of
each and the under surface of one and the upper surface of
another leaf with a varnish made of equal parts of
beeswax and lard or ordinary grafting wax if some-
what softened. Both surfaces of the third leaf are
to be left uncoated. The stomata are found only on
the lower surface and it will be found that the leaf
with this surface coated, thus covering the stomata,
remains fresh for a long time while the other two
wither quickly.
Fig. 42. (A 'p^g Icaves of the Cottonwood (Populus, vari-

— R oot •\i ii-iVki

pressure ous spccics) havc stomata on both sides. Repeat the
(Ji^f"™®'^^ foregoing experiment with leaves of this and com-
pare with the results obtained with the lilac,
(m) Root pressure may be demonstrated by cutting off the
stem of a rapidly growing sunflower or other rather large
plant (e.g. tomato, geranium, castor bean, etc.) and slipping a
heavy rubber tube over the cut stump, connecting this with a
narrow glass tube. If the soil be kept warm and wet water will
soon begin to escape from the cut surface and will rise to a

ENTRY OF SOLUTES 81

considerable height in the tube. If the latter be connected with
a mercury manometer the pressure can be measured.

116. Nutrients Other than Water. All other sub-
stances can enter the plant only in solution in water.
This is true of the gases as well as of mineral salts, for
although a gas may enter the air spaces of a leaf in the
gaseous state, it cannot penetrate the wet cell walls in this
state but must go into solution. It is then subject to the
same physical laws of diffusion as the other solutes.

117. The wet cell wall presents no (at least marked)
obstacle to the diffusion of any solute. The plasma
membrane, however, is impermeable for some, difficultly
permeable for others, and easily permeable for still other
substances. Accordingly the molecules of the substances
in solution outside of a cell will penetrate into the cell
with different degrees of rapidity and independent of the
direction that the water is passing. The result will be
that the solution inside of the cell may have its compo-
nents in entirely different proportions from the solution
outside.

118. The process by which solutes pass into the cell
and from cell to cell is diffusion. This is the molecular
passage of a solute from that part of a solution where the
concentration of that particular solute is greater to where
it is less. As long as the plasma membrane is easily
permeable for the particular solutes they have no osmotic
effect and may diffuse in the same direction with or
counter to the osmotic stream. Thus the dissolved salts
that enter a plant do so independently of osmosis and
diffuse toward those parts of the plant where these
particular salts are less abundant. They will not
become more concentrated anywhere in the plant than
outside of it as long as they retain their same composition
and the permeability of the plasma membrane remains

82 PLANT PHYSIOLOGY

the same. Frequently, however, they are changed chemi-
cally after they enter the plant and then are no longer able
to pass through the external plasma membrane. In
such a case the plant may be able to take in large amounts
of one substance from a dilute solution. Certain sea-
weeds, for example, accumulate large amounts of iodine
compounds from the sea water which contains iodides
only in very great dilution.

119. Water consists of hydrogen and oxygen (H2O).
Besides these two elements eight others are ordinarily
necessary to plant life. They are carbon (C), which
chiefly enters the plant in the form of carbon dioxide
(CO2) (see paragraph on photosynthesis), nitrogen (N)
in the form of nitrates or ammonium salts, calcium (Ca),
magnesium (Mg) and potassium (K), these mostly oc-
curring as phosphates, nitrates, sulphates or carbonates,
iron (Fe) in very small amounts as salts of various acids,
sulphur (S) almost entirely as sulphates (except in those
plants that feed on organic food where it may be taken up
from the proteins and a few lower plants which use
H2S or even free sulphur) and phosphorus (P) as various
phosphates. In addition to these, sodium (Na) is re-
quired by some plants, while on the other hand calcium
(Ca) is not required by certain fungi. Of the ten
elements first mentioned the last seven are usually taken
in as mineral salts from the water in which they are
dissolved. The oxygen is taken in, in the acid radical of
the sulphates, nitrates, carbonates and phosphates, in
combination with hydrogen in water, and in combination
with carbon in carbon dioxide as well as in the elementary
form directly from the air or in solution in the water.
Carbon in addition to being taken in as carbon dioxide
exists in the carbonates and in the case of hysterophytes,
also in various organic substances taken in by the plant.

ADDITIONAL NUTRIENTS 83

The use of free nitrogen by certain bacteria, will be
discussed further on.

120. In addition to the substances mentioned in the
preceding paragraph, silicon (Si) is taken up by many
plants (as silicates of various kinds) and adds to their
hardness but can be dispensed with except by the
diatoms whose cell walls are composed largely of silica.
Sodium can take the place of potassium for many pur-
poses, e.g. neutralizing acids, but cannot be substituted
for it entirely. Similarly an excess of calcium can replace
part but not all of the magnesium, while barium (Ba) and
strontium (Sr) can replace part of the calcium. Chlorine
(CI) in the form of chlorides is useful to many plants but
apparently can be dispensed with by almost all. The
various other salts present in the soil solution may be
taken up by the plant in greater or less degree, but
appear either to have no use whatever or to be used only
incidentally without being indispensible. Such are salts
of copper (Cu) aluminum (Al) manganese (Mn) zinc
(Zn), etc.

121. The role that the various substances mentioned
in the foregoing paragraphs play in the plant economy
is not certain in all cases. It is probable that calcium
and potassium, perhaps also magnesium and iron, are
essential parts of the protoplasm molecule. Sulj)hur is a
component of proteins while phosphorus is found in some
proteins, especially in the nucleus. Carbon, hydrogen
and oxygen are the components of the carbohydrates
which are the chief building materials of the plant (e.g.
cellulose) and of the proteins out of which protoplasm is
built up. In the absence of iron the chlorophyll seems
impossible of formation although it does not contain iron
itself. Mention must be made of the principle of
antagonistic action by various salts. Thus it has been

84 PLANT PHYSIOLOGY

shown that solutions of certain salts poisonous to plants
become innocuous upon the addition of certain other
salts which of themselves may also be poisonous. This
discovery has thrown doubt upon many of the con-
clusions of earlier botanists as to the functions of salts
that are supposed to be essential to plant life.

122. So far we have merely considered what sub-
stances are required by the plant and something of the
form in which the plant takes them in. Before they can
be used they must undergo various decompositions and
recombinations; in other words after absorption there
must be assimilative processes. Perhaps the most funda-
mental of these processes is that by which the carbon
compounds are built up by green plants, a process called
photosynthesis.

123. Photosynthesis. The green parts of all chloro-
phyll-bearing plants absorb carbon dioxide from the
surrounding water if aquatic plants, or from the air, which
contains about three parts of it to ten thousand. This
absorption goes on only when the plant is exposed to the
light. At the same time there is an increase in the
amount of carbohydrates often manifesting itself to the
eye by the formation of starch grains in the chloroplasts,
but also demonstrable chemically by the increased
amount of sugars (chiefly glucose C6H12O6) in the cell
sap. At the same time it can be demonstrated that
oxygen is given off by the plant. It is this process, the
manufacture of carbohydrates by green plants in the
presence of light, that has received the name photo-
synthesis (from the Greek meaning ''putting together
by light").

124. Careful experiments have shown that this
process cannot occur in the absence of any one of the
factors mentioned in the preceding paragraph. Thus a

PHOTOSYNTHESIS 85

plant growing in the light in an atmosphere free from
carbon dioxide cannot manufacture carbohydrates any-
more than if it were in the dark. A plant lacking chloro-
plasts, e.g. the fungi, cannot manufacture carbohydrates
from carbon dioxide even if light be present (excepting cer-
tain bacteria, the so-called nitrite and nitrate bacteria).
The process takes place in the chloroplasts apparently.
The light rays most effective in photosynthesis seem to be
those in the red part of the spectrum while those at the
violet end also have some value. Those lying between
seem in the main to be useless. The green color represents
the portion of the white light that strikes the chlorophyll
and is reflected back or passes through it without being
absorbed. The raw materials are carbon dioxide and
water, the energy is derived from the absorbed rays of
light and the end products are carbohydrates and oxygen.

125. The exact steps in photosynthesis are not
certainly known but the following seems to be the
probable course of events:

C02+H20 = H2C03 (water, plus carbon dioxide, equals
carbonic acid).

H2C03 = H2CO + 02 (carbonic acid acted on by the
energy derived from light by the cholorophyll is changed
into formaldehyde and oxygen) .

6H2CO = C6Hi206 (formaldehyde, probably by the
aid of more energy derived from the light is polymerized
into glucose).

It \\411 thus be seen that for every molecule of carbon
dioxide used up one molecule of oxygen (O2) will be set
free. Glucose is the carbohydrate first formed in most
cases but as this accumulates in the chloroplasts and
cell sap it is often transformed rapidly into the insoluble
starch (C6Hio05)n which becomes stored up in large
quantities in the chloroplasts. Sometimes instead of

86 PLANT PHYSIOLOGY

starch, drops of oil are produced in the cytoplasm and
cell sap, or cane sugar (C12H22O11) or some other
carboliydratcs.

126. The further fate of the carbohydrates formed in
photosynthesis is varied. The excess of glucose or other
sugars in the chlorophyll-bearing cells in addition to
what is put aside temporarily in insoluble form as starch
diffuses through the adjacent cells and finally reaches
the vascular bundles where it enters the parenchyma cells
bordering the sieve tubes. It probably diffuses through
these into the latter in which it diffuses and is probably
also carried by streams of protoplasm to those parts of
the plant where the tissues contain less glucose.
Here it diffuses out into these tissues. Besides passing
in the sieve tissues diffusion doubtless occurs from cell
to cell throughout the parenchyma of the cortex espe-
cially in those cells bordering on the sieve tubes. Dur-
ing the night the starch grains that have accumulated
in the chloroplasts in day time are transformed into
glucose which diffuses in the manner just described.

127. The carbohydrates transported in this manner
may be stored up as reserve food in various forms. Thus
they may be transformed into starch in the leucoplasts of
the storage organs, e.g. tubers of potato, roots of sweet
potato {lyomoea batatas), pith of various twigs such
as apple, sassafras, etc., medullary rays of many trees,
endosperm or cotyledons of seeds, etc. Cane sugar may
be found in many plants such as beets, maple, sugar cane,
etc. Inulin is found in the roots of many plants par-
ticularly those belonging to the order Asterales. Trans-
formed into fats they are found in many seeds, e.g. flax,
cotton, peanut, castor bean, as well as in the bulb scales
of onion, leaves of cabbage, etc. In the seeds of many
palms, e.g. date, and the wood of many trees, e.g. elm and

PROTEIN SYNTHESIS 87

mulberry, the reserve carbohydrate is in the form of a
thick deposit on the inner surface of the cell wall. This
is a substance closely related to cellulose, one of the hemi-
celluloses. The sugars in fruits perhaps belong in the
category of stored foods although they serve rather as
a bait for animals which on eating the fruit aid in the
distribution of the seeds.

128. The carbohydrates produced, whether first
stored up or used immediately, have for their ultimate
destination various functions. As building materials
they are used up in the formation of cell walls in the grow-
ing parts of plants. Whether they are thus used directly
or must first become a part of the protoplasm is uncertain.
The use of carbohydrates in furnishing energy to the
plant will be discussed under the topic Respiration.

129. A considerable portion of the carbohydrates
eventually becomes built up into those very complex
nitrogenous compounds called proteins. Whether the
carbohydrates are taken as such and combined with
nitrogen obtained from the nitrates and sulphur and
phosphorus from the sulphates and i:)hosphates re-
spectively, the product being proteins, or whether as
seems possibly may be the case part of them are broken
down and then combined with the nitrogen to form
hydrocyanic acid (HCN) this being polymerized and
combined with other carbohydrate molecules and with
sulphur and i)hosphorus, is not known. In any case
hydrocyanic acid is often formed in i:>lants in which active
protein production is taking i)lace.

130. Certain bacteria, chiefly parasitic in the roots
of plants of the bean family (Fabaceae), are capable,
when supplied with carbohydrates and the necessary'
mineral salts, of using the atmospheric nitrog(>n (as dis-
solved in the soil water) in building up protein com-

88 PLANT PHYSIOLOGY

pounds. These bacteria form galls on the roots of the
host plants. As they grow old the host plant digests
them and is thus able to thrive in a soil free from nitrog-
enous compounds. Thus if the bacteria are present,
crops of beans, clover, alfalfa, etc. will actu-
ally increase the amount of nitrogenous
compounds in the soil instead of decreas-
ing it.

131. The proteins formed may be stored
up as such for future use by the plant (e.g.
aleuron in seeds) or may be transported to
those parts of the plant where new cell
■^SdulermcL') * production and growth are taking place.
Here it is built up into protoplasm. How
this is accomplished we do not know. The path of
transportation seems to be in the sieve and possibly
laticiferous tissues. The form in which protein matters
are transported may be either as simple proteins or as
amids.

132. Hysterophytic plants, i.e. plants that lack chloro-
phyll, must obtain their organized food (carbohydrates,
proteins, fats, etc.) from sources outside of themselves.
We find all degrees of ability to make use of various
food sources. Some hysterophytes simply require
carbohydrates and mineral salts and can produce their
own proteins, others must have special, and in the case
of parasites, living forms of proteins. Some even are
able to use simpler carbon compounds than carbohy-
drates such as some of the simpler organic acids, glycer-
ine, etc. In general, however, the nutrition of hystero-
phytes differs but little from that of holophytes (i.e.
plants containing chlorophyll) except in their inabihty
to manufacture their own carbohydrates.

133. The means by which hysterophytic plants

NUTRITION OF HYSTEROPHYTES 89

obtain their food supplies are quite varied. One-celled
plants like yeasts and bacteria absorb the organic sub-
stances directly, or often decompose them to the appro-
priate form by means of digestive ferments called
enzymes, which are organic compounds of complex
structure whose exact action is not clearly known. Fungi
consist of long filaments of cells which either pass
through the substances to be absorbed or send little
suckers, called haustoria, into the cell of the host, the
latter being often the case with fungi i)arasitic upon
living plants. Among the hysterophytic flowering plants
some feed on decayed organic matter in the soil, others,
e.g. dodder, send haustoria into living plants, and take
organic substances directly from them. Some of the
mistletoes which possess chlorophyll take little else than
water and mineral salts. Of especial interest are the
insectivorous plants which catch and digest insects by
means of special structures. The digested insects are
the source of their nitrogen for many of these plants that
hve where nitrogen compounds are lacking in the soil.
Some plants have fungous hyphae growing partly within
and partly outside of some or all of their roots. Such roots
are often of peculiar shape and are known as mycorrhiza.
The fungi absorb water and mineral salts from the soil
and deliver them to the root from which in turn they
take organic foods. Some of these fungi are said to be
able to make use of the atmospheric nitrogen as do the
bacteria in the root tubercles of the bean family.

134. All the foregoing processes, e.g. transformation of
carbohydrates from one form to another, their trans-
portation and storage, their ])uilding uj) into proteins,
the transportation and storing away of the latter and
their building up into protoplasm, require the expenditure
of a considerable amount of energy. This must be

90 PLANT PHYSIOLOGY

available in every living cell and not confined to any
definite locality in the plant. This is made available by
the process known as respiration.

135. Respiration. With the exception of a few
bacteria and low fungi to be mentioned later all living
cells absorb oxygen and give off carbon dioxide, the
process being accompanied by a loss in weight. In
green plants in the light the absorption of carbon dioxide
and giving out of oxj^gen are so much greater than this
other process that for years it was not known that the
latter takes place. It is not dependent upon the
presence of light nor are chloroplasts necessary for its
occurrence. It takes place more rapidly the higher the
temperature until an optimum temperature is reached
which is sometimes perilously near to the death point of
the cell.

136. The oxygen is taken from the air (which contains
nearly 20 per cent, of oxygen) by the aerial parts of the
plant. It passes through the stomata and lenticels and
also to some extent through the cuticle into the inter-
cellular spaces and from thence is absorbed by the
cells. The roots whose outer walls are only slightly
cutinized and whose root hairs are practically free from
cutin absorb the oxygen which is dissolved in the soil
water and which is present in the air spaces between
the soil particles. Submerged plants, e.g. algae, absorb
the oxygen dissolved in the water. Many trees which
grow in swamps where the soil lacks oxygen send up
peculiar vertical branches from their roots out to the
surface and up into the air, these serving as aerating
organs for the roots. Such are the ''knees" of the
bald cypress {Taxodium distichum) when the latter
grows in wet places (and which are lacking when it grows
in well aerated soil) and the aerial roots of sotne of the

RESPIRATIOX 91

mangroves (e.g. the black mangrove of Florida, Avicen-
nia nitida).

137. Respiration consists primarily in the breaking up
of the complex molecules 'of certain organic compounds
(chiefly car])oh3'drates or even the carbohydrate portions
of protoplasm molecules) into simpler compounds. This
releases a large amount of energy much of which becomes
available for the use of the plant. Since all living parts
of the plant require energy, respiration will be found to
take place in all parts. The intensity of the respiration
varies with many factors, viz. the amount of food avail-
able that can be broken down into simpler compounds,
the availability of oxygen, the amount of water, the
temperature, etc. To what extent the protoplasm itself
can regulate the occurrence of this process, if the other
conditions are fulfilled, is uncertain.

138. Part of the energy set free in respiration is
exhibited in the form of heat. This is especially notice-
able where rapid gro^\i3h and rapid respiration are oc-
curring as in large flower buds, fruiting bodies of large
fungi, etc. In ordinary parts of plants the radiating
surface is great enough to keep the plant cool so that the
heating is not noticeable. In the case of wet leaves, hay,
manure, etc., the heat produced by the respiratory proc-
esses of the fungi and especially the bacteria present
leads in some cases to the kindling of some of the easily
inflammable substances produced so that it is a frequent
occurrence for hay, especially moist alfalfa hay, and
manure to catch fire.

139. It has been shown that there are two distinct
stages in respiration which follow one another so closely
in most cases that they a])pear as one. These are the
anaerobic and aerobic stages. Certain bacteria and
yeasts show only the first stage. In this stage no oxygon

92 PLANT PHYSIOLOGY

is required from outside the ceU. By the aid of certain
enz3^mes produced by the cell the carbohydrates or other
substances used in respiration are started in their disin-
tegration and proceed in it until simpler compounds and
some carbon dioxide are produced. Thus glucose is usually
decomposed into alcohol and car])on dioxide, the end
results being in accordance with the following formula:

C6H12O6-2C2H5OH+2CO2.

It is probable that the reaction is not as simple as this,
but that there are many steps in the process. This proc-
ess sets free a certain amount of energy. In the produc-
tion of alcohol and carbon dioxide from sugar by the yeast
plant it is this anaerobic stage of respiration that takes
place. Corresponding decomposition processes occur in
various kinds of bacterial fermentation and decay, the
intermediate and end products varying with the com-
position of the substance fermented and the kind of
organism.

140. The aerobic stage consists usually of the oxid-
ation of the rather complex compounds produced in the
anaerobic stage to simpler compounds, this also being
accompanied by the liberation of energy in large
amounts. This process also is probably carried on by
the aid of enzymes and it may be that the use of the
oxygen is rather to get rid of harmful products instead
of being the agent which sets free the energy. Taking
the case illustrated in the preceding paragraph the
alcohol is broken down and combined with oxygen to
form carbon dioxide and water. The final results, but
not the intermediate stages, are shown by the following
formula

C2H5OH+6O = 2CO0+3H2O.
Alcohol + oxygen = carbon dioxide + water.

RESPIRATION 93

By comparing the final results of the anaerobic and aero-
bic respiration of glucose with the steps in the photo-
synthetic production of glucose we realize that the proc-
esses are the reverse of one another. It is reasonable
to suppose then that the amount of energy set free in
the processes of respiration will equal that required to
build up the same amount of glucose in photosynthesis.
Viewed from this standpoint respiration is the process
by which the plant obtains at the places where it is needed
the energy taken in from the light by the chloroplasts.
The manufacture by photosynthesis of an excess of
carbohydrates over that used each day by the plant in
respiration enables the plant to store up a large amount
of energy for the winter season when photosynthesis
cannot occur or for the rapid grow^th of new organs
another season. With all the processes of respiration
the protoplasm, the living part of the cell, is intimately
connected. It is to it that the energy set fr^e is probably
transferred. It is apparently the protoplasm that regu-
lates the amount and location of the respiratory activi-
ties. How all this is brought about is still unknown as
is the relation of the structure of protoplasm and the
energy used to what we call ''life."

141. In place of the type of respiration described
above a few bacteria obtain their energy in other ways.
Thus the nitrite bacteria oxidize the ammonia of am-
monium salts to nitrites and the nitrate bacteria oxidize
the nitrites to nitrates, each of these processes setting
free a small amount of energy which is made use of by
the bacteria. In both cases the energy thus obtained is
sufficient to enable the cells to build up from carbon
dioxide and water the carbohydrates needed in the
cell's growth and further to combine these with the nec-
essary substances to form proteins and protoplasm.

94 PLANT PHYSIOLOGY

Still other bacteria inhabiting sulphur springs or places
where sewage is abundant obtain the necessary energy
by oxidizing US to SO2, sulphur frequently being stored
up as a reserve food supply. It is held by some investi-
gators that other bacteria obtain their energy by oxi-
dizing certain iron compounds, others by oxidizing
methane and still others hydrogen.

142. In the foregoing processes of photosj^nthesis
and respiration (including fermentation) many other
substances are produced besides those mentioned. Some
of these are perhaps nothing more than waste products,
or at least by-products, but others are reserve food of
various kinds. Still others perhaps serve for special
functions such as protection of plants from attacks of
insects, covering of wounds, etc. Among the substances
thus produced and whose functions are not certainly
known, are the alkaloids of which a great many have been
studied, e.g. caffein, nicotine, etc. Besides these may be
mentioned resins, rubber, gutta-percha, glucosides, etc.
Many of these are of great use to man. Many are very
poisonous. The organic acids mostly stand in another
category. They are either directly reserve stuffs, re-
placing carbohydrates, or are stages in the respiration
of carbohydrates, or in many cases are the substances
which produce the requisite osmotic pressure within the
cell. The commonest organic acids are the following:
maUc, (C4H6O5) found in the apple and many other
fruits as well as in the leaves of many succulent plants,
citric (CeHsO?) in the fruits of lemon, orange, etc.,
tartaric (C4H6O6) in fruit of grapes, oxalic (C2H2O4)
in the leaves of many plants, e.g. Oxalis, Rumex, etc.,
and tannic acid (C14H10O9) and its derivatives which ap-
pear to play a very important but little understood part
in the energy relations of the plant. ]\Iany of these

TEMPERATURE 95

acids are present in the free form but some of them
appear mostly as the acid salts of various metals.

143. Temperature. The relation of the plant to
temperature will be discussed here as it is chiefly a ques-
tion of the effect of temperature upon the nutritive
functions. Five cardinal points for temperature can be
distinguished for these different processes. They are:
death point from cold, death point from heat (points
which are the same whatever the process and mentioned
here simply because when reached the process cannot
be resumed when normal temperatures are again re-
gained), minimum, optimum and maximum. The last
three are quite different for different life processes.
Thus the optimum and maximum for respiration are
usually much higher than for photosynthesis, in fact
they often lie close to the death point from heat. Be-
tween the death point from cold and the minimum for
various processes may be a small range or sometimes
a great range of temperature. Usually the minimum
point is a little above or not much below 0° C. The
maximum temperature for the various functions lies
usually between 36° and 43° C. and the death point be-
tween 50° and 55° C, but in a few plants of hot springs
as well as some bacteria causing the heating of manure,
etc., the optimum temperature may be about 60° and
the death point even as high as 75° to 85° C.

144. The death of plants by heat appears to be due
to the coagulation of some of the protein constituents of
the protoplasm. Since this coagulation cannot occur
unless a certain amount of water is present we find that
some nearly water-free structures are able to endure
rather high temperatures. Thus the spores of some
bacteria can be boiled for several hours before they are
killed and some seeds can endure a dry heat exceeding

96 PLANT PHYSIOLOGY

100° C. Similarly dry plant parts can endure very low
temperatures. Many seeds are not killed by an ex-
posure for several hours to the temperature of liquid
hydrogen (below — 250° C). The latter is also true for
many single-celled water plants that must contain plenty
of water, e.g. diatoms, bacteria, etc. On the other hand
many watery tissues are killed by a temperature that does
not reach the freezing point. Just the reason for this is
unknown. It is here suggested that at these low
temperatures certain processes continue which result in
the accumulation of poisons, while the processes that
would usually destroy these poisons, are prevented by the
low temperature so that in reahty the death of the plant
would be due to poisoning.

145. Freezing of plants may cause death in several
ways: (1) the ice crystals formed may rupture the
cells or disrupt the tissues; (2) the water may escape
into the intercellular spaces and be frozen there and on
thawing rapidly may remain outside the cells filling up
the intercellular spaces and cutting off the air supply;
(3) the withdrawal of water from the protoplasm by freez-
ing may so increase the concentration of certain sub-
stances dissolved in the cell sap that the cells are killed.
Upon the whole subject considerable uncertainty rests.

146. Effect of Poisons. Many substances are poison-
ous to living plant cells. The effects are almost as varied
as the types of poisons. Some, like the strong acids,
simply decompose the protoplasm and cell walls and so
destroy life; others, Hke the salts of the heavier metals,
coagulate the protoplasm; others even in minute quanti-
ties interfere with the nutrition of the cell in a manner
not understood, and kill it. Thus one part of copper in
ten million parts of water will kill certain algae and fungi.
Hydrocyanic acid acts apparently by preventing the

EFFECT OF POISONS 97

taking in or using of oxygen in respiration. IMany
parasitic plants, e.g. bacteria and fungi secrete poisons
or induce activities in the cells of the host that lead to the
accumulation of poisons that may destroy the life of a
cell or lead it to abnormal growth or functioning.

Laboratory Studies, (a) Take a piece of the root of a living
red beet. Cutout a cube a centimeter or so in diameter. Wash
off the colored cell sap that has escaped from the cut cells and
place the cube in a test tube of water. So long as the cells are
alive their plasma membranes prevent the colored solute in the
cell sap from escaping. Gently heat the test tube. When the
death point of the beet tissues is reached (below G0° C.) the
plasma membranes are no longer impermeable and the color
diffuses out into the surrounding water. This experiment also
shows that the cell walls themselves are but slight obstacles
to diffusion. Instead of by heating, similar results may be
obtained by using certain poisons such as strong alcohol, etc.,
but care must be taken not to choose a substance that will
destroy the coloring matter.

(b) Set up a series of water cultures as follows : Take glass
jars (]\Iason jars will do) and to keep the contents dark encase
each with a cylinder of pasteboard which can be removed to
permit of observation. Fill these jars nearly full of the solution
to be tested, leaving a small air space between the water and
the cork. The cork should have at the center a hole 5 or
6 mm. in diameter. Germinate some peas, corn, buckwheat or
mustard seeds. When the radicles are 2 to 3 cm. long, fasten
one seed to each cork in such a way that the root just enters the
solution and the plumule is in a position to pass uj) through the
hole in the cork (or the seed can be fastened outside with the
root passing through the hole). Instead of a cork the jars may
be nearly filled with water and melted parafhn poured upon it ;
after the paraffin has hardened several holes may be made
through it by means of a hot metal rod. The water can now
be poured out and the desired liquid poured in, nearly up to the
under side of the paraffm. The germinated seeds can be set
upon this paraffin cap in such a way that the radicles will pass
throu2;h the holes. Expose all the jars to the same light and
temperature so that as far as possible the only differences will

98 PLANT PHYSIOLOGY

be those of the composition of the solutions. Make up the
following solutions and fill into the jars:

1. Distilled water

2. Complete culture solution (Sachs)

3. Complete culture solution, omitting the KNO3

4. Complete culture solution, omitting the ]\IgS04

5. Complete culture solution, omitting the KXO3 and

K2SO4 and adding Ca(N03)2 in place of the first.

6. Complete culture solution, omitting theCa3(P04)2

and adding an equal amount of Ca(N03)2

7. Complete culture solution, omitting theK2S0i and

MgS04 and replacing by an equal amount of
Mg(N03)2

8. Complete culture solution omitting the Ca3(PO.i)2

and substituting K2HPO4

9. Complete culture solution omitting the FeCU.
The Sachs' solution consists of:

Distilled water 1000 cc.

KNO3 1 gm.

K2SO. 0.5 gm.

MgS04 0.4 gm.

Ca3(PO02 0.5 gm.

FeCls trace.

Let the plants grow for several weeks, rej^lacing the old
solutions by fresh ones of the same composition every week or
so. Compare the amount of growth of both roots and stems in
the different solutions, the size and color of the leaves, etc.
Note when growth ceases and to what stage of development
the plant proceeds before its death.

(c) Bring some Spirogyra into the laboratory and place
in a dark room (not too cold) for twentj'-four to thirt^^-six
hours or until on testing some of the plants with iodine solution
no starch is found. Bring the dish into the sunlight and with
iodine solution test some of the plants for starch after five
minutes, ten minutes, half an hour, etc.

(d) In a rather broad, deep glass dish (e.g. a wide battery
jar) place some actively growing Spirogyra. Put a bit of wire
netting (iron, not copper nor brass) into the bottom of a short-
tubed funnel and invert over the Spirogyra submerging the

LABORATORY STUDIES 99

funnel and its tube completel}'. Over the latter invert a test
tube filled with water. Now raise the funnel as high as it will
go without lifting the edge of the test tube above the surface
of the water, supi)orting it on a small block. Place the whole
in the sunlight. As photosynthesis goes on the oxygen given off
by the pond scum collects in the test tube and may
be tested in various ways, e.g. by carefully re-
moving the test tube, inverting it and inserting
a glowing splinter which will burst into flame if
sufficient oxygen is present. The diameter of the
funnel must be considerably less than that of the
jar or no CO2 can reach the Spirogyra and photo-
synthesis will soon cease. If CO 2 is passed into
the water occasionally, taking care not to let any
bubbles enter the funnel, the activity of the process
is increased.

(e) In a similar way the oxygen evolved in photosynthesis by
Philotria (Elodea) may be collected by inserting the cut ends of
several plants into the mouth of an inverted test tube filled
with water and placing the whole dish in the sunlight. Care
must be taken, however, not to confuse two phenomena here, viz.
the rapid outflow of bubbles at first, due to the expansion of the
gas already present in the stem as it heats, and the much slower
evolution of oxygen by photosj-nthesis. After the first outrush
of gas due to the expansion by heat is past the relative
amount of photosynthesis can be told with a fair degree of
accuracy by counting the number of bubbles of oxygen evolved
per minute under the different conditions. Be sure, however,
to keep the water well supplied with CO2. Test now the effect
of placing glass plates of difi"erent colors in front of the dish
containing this j)lant, in all cases waiting long enough to
avoid the effect of the changing volume of the enclosed gas due
to changes of temperature.

(/) Place two potted geranium (Pehirgonium) ]ilants. prefer-
ably with plain, not variegated leaves, in the dark until their
leaves contain no starch. Now place them under bell jars,
sealing one air tight with sealing wax or by other means, first
placing under the jar a dish containing a strong solution of
KOH to absorb all CO2. Leave a small air space under the
edge of the other bell jar so as to permit the entry of air
containing CO2. After an hour or so place both plants in the

100 PLANT PHYSIOLOGY

sunlight and after three or four hours test their leaves for the
presence of starch as follows: Remove a leaf, immerse it in
hot alcohol for a few minutes to extract the chloro])hyll and then
cover with a strong solution of iodine which will color the leaf
blue or not according as the starch is present or absent. To
avoid rupture of the sealing by the expanding air it is well to
use a bell jar with an opening at the top into which is placed a
cork through which a glass tube passes. This tube should be
bent so that its other end is immersed in a dish of mercury.
As the air expands it passes out through this tube and escapes
through the mercury but the air and carbon dioxide from out-
side cannot enter.

(g) On a large leaf of geranium (Pelargonium), or other
plant which produces starch in abmidance in its leaves, clamp
on the upper side a flat cork and on the lower side a httle box
(a wooden box such as cover glasses come in will be satis-
factory) blackened inside and whose sidea

I r-T-x-r — , have been pierced from the outside by

^^' ^V' . ^ ^ ^ ^ ii'"^'^w^ ■ ■^''->|v>'^^>^ . ■a" > numcrous Small holes running obliquely
away from the leaf. These holes admit air
(and CO2) but as thej^ point awaj^ from the

Fig 45 — D" ^^^^ ^^^ ^\^\^ admitted through them is ab-

pearance of starch sorbed by the blackened inner surface of the
^^' box. Set the plant in the sunlight for sev-

eral hours then remove the leaf and treat
with alcohol and iodine as in (/). The spot protected from
hght by the cork and the httle box will show no starch.
To clamp two corks together on both sides of the leaf is un-
satisfactor}^, as in that case not only is the light cut off but the
CO2 as well, so that the reason for the lack of starch in that case
is two fold.

(A) Reserve carbohydrate in the form of starch may be
demonstrated in the tubers of potatoes, root of sweet potatoes
(Ipomoea batatas) , seeds of corn (Zea 7/ia?/s), wheat, beans, etc.
In the form of cane sugar it is present in the root of the beet
(especially in the sugar beet), in the stem of corn and sugar cane,
etc. As hemicellulose it is present in the wood of mulberry
(Morus) and elm where it ma}' be demonstrated by treating a
section with sulphuric acid followed by iodine solution. Food is
stored up in the seeds of cotton, castor bean (Ricinus), flax,
etc., and in the scales of onions, leaves of cabbage, etc., as fats.

LABORATORY STUDIES 101

It may be demonstrated by treating with dilute osmic acid
solution which turns fats black, or withalkannin solution, which
stains the fat drops red.

(t) Place a geranium (Pelargonium) plant in the light for
several hours until starch has been produced in quantity in the
leaves. On two or three leaves cut one or two of the main
radial veins leaving the other veins intact. Cover the whole
plant loosely with a bell jar to prevent these injured leaves from
drying out too much and place in the dark for from twelve to
twenty hours. Treat these leaves with alcohol and iodine
solution as in (/) to determine the location of the starch. It
will be found to have disappeared except from the portions
bordering on the cut veins, showing that it is through these
veins (vascular bundles) that the carbohydrates are transported.

(j) Reserve protein in the form of aleuron in the seeds of
beans, peas, etc., was studied in connection with cell inclusions
(paragraph 24). It will be worth while to repeat these
observations.

(k) Examine one of the powdery mildews (Erysiphaceae) as
an example of a hysterophytic lower plant that obtains its
food from living plants (i.e. is parasitic). Take a bit of infected
leaf and moisten with alcohol, then mount in water or dilute
potassium hj-drate solution wdth the infected side uppermost.
By careful focusing the filaments of the fungus may be dis-
tinguished and here and there may be seen the haustoria
("suckers") which are sent into the epidermal cells of the
leaf. Better developed haustoiia can sometimes be found on
making cross-sections of leaves or stems affected by downy
mildew (Peronosporaceae) or wliite rust (Albugo). In these
cases the whole fungus except certain reproductive ])arts is
within the host plant, growing interccllularly and sending well
developed haustoria into the cells between which it passes.
In both cases note the lack of chlorophyll in the fungus.

(/) Examine a dodder plant (Cuscuta) as an example of a
higher plant that is parasitic. No leaves are to be found and
in most cases no chlorophyll, and the plant carries on no
photosynthesis. The original root which penetrated the soil
dies as soon as the plant has attached itself to its host or even
before. Note the roots by which it obtains its food from the
host. Sections of the stem will reveal vascular bundles, epi-
dermis, etc., but usually no chlorophyll-bearing cells.

102 PLANT PHYSIOLOGY

(m) Place a number of fresh leaves or a short shoot with
leaves in the large end of a retort with a little water and place
the small end under a surface of mercury to prevent the
entrance of gases. Keep in a dark moderately warm place for
from twelve to twenty-four hours. Note tiiat the volume of
the gas does not seem to be changed. Carefully without allow-
ing any air to enter run a pipette full of strong KOH solution
into the small end of the retort or introduce a small piece of
stick potash (KOH) with a few drops of water, these rising to
the surface of the mercur}'. As the CO2 is absorbed the
mercury rises. When the ascent ceases (i.e. all the CO2 has
been absorbed) introduce a strong solution of pyrogallic acid.
This has the property when mixed with alkaline solutions of
absorbing oxygen. Note w^hether the mercury rises any
further. If it does so it shows that some oxygen was present.
Repeat the experiment using a retort without any leaves in it.
It will be found that about as much COowas produced by the
leaves (as shown by the height to which mercury rose with the
KOH alone) as oxygen was present (as shown in the control
experiment by the distance the mercury rose with the KOH
and pyrogallic acid). If this can be done with graduated cylin-
ders the amounts can be measured more accurately.

(n) That CO 2 is given off by a hving plant may be demon-
strated in the following waj^ also. Place a potted plant under
a bell jar with a dish of Ba(0H)2 solution or (less preferably)
Ca(0H)2 solution. Put in a dark place. The CO2 given off
forms a crust of BaCOc (or CaCOs) on the surface of the liquid
while in a control experiment with no plant under the bell jar
the amount of CO 2 in the air (3 parts in 10,000) produces only
a very small precipitate.

(0) Soak some peas over night and then place them in a
tall glass jar filling it about half full, and cover with a vase-
lined glass plate. After a few hours remove the plate and
lower a burning taper into the cyHnder. It is extinguished
by the CO2 which has replaced the oxygen. If the air is
very still it is more striking to place a small lighted taper in
the bottom of anotherjar and topour the CO2 from the jar of
peas into this jar, extinguishing the light.

ip) vSoak some peas over night. Fill a test tube with mer-
cury and invert over a dish of mercury. Force three or four
peas under the mercury so that they come under the edge of the

LABOUATORY STUDIES 103

test tube, when the}- will rise to its closed end. Respiration
in its first (anaerobic) stage will go on and gas will
be formed, oftentimes driving nearly all the mercur}^ |
out of the tube. Introduce a strong KOH solution L
or a piece of stick KOFI and a little water under Hffl
the edge of the test tube and the gas will all be I^uts-
absorbed, showing that it is CO2 that was produced, pirution

, GXpG r 1-

(q) Yeast plants ordinaril}^ carrj' on only this first ment
stage of respiration (called fermentation in this case). ^ ^'
To potato water (made by grating up a potato and boiling it in
a little water and expressing the latter) add about 5 per cent,
glucose. Place in a flask with a cork and a glass tube bent so as
to lead the gas produced under water. Break up part of a cake
of compressed yeast in a little water and add it to tlie solution in
the flask and insert the cork and glass tube. In a short time
gas will begin to escape in bubbles from the end of the tube.
Collect some in a test tube and test in various ways such as for
inflammabiUtj^, absorption by KOH, etc. It will be found to
be CO2. Note what large amounts are produced. After the
evolution of gas has ceased the proper chemical tests will show
the presence of alcohol in the liquid. Distill the latter and
collect the first part that comes over. Add to it some strong
KOH solution and some flakes of iodine, and heat. If alcohol is
present a strong odor of iodoform will be produced and if much
is present this will show as a yellow precipitate.

(r) The liberation of heat during resj^iration can be demon-
strated by placing a quantity of soaked peas or a number of
mushrooms just expanding in a flask with an accurate chemical
thermometer bulb in their midst and placing this flask in a
mass of cotton in another vessel and covering all with several
layers of cloth, leaving only the thermometer tube exposed.
Often the temperature within tlie flask will rise 3 or 4 degrees
or more above that of the surrounding air. Of course this
experiment must be carried on in a room where the temperature
is fairly constant. If a Dewar bulb or a Thermos bottle is used,
these being double walled with a vacuum between so that the
loss of heat is very small, the difference of temperature is
much more marked.

(.s) Without special thermostats where temperatures can be
controlled exactly, satisfactory ex])eriments as to the cardinal
points of temperature cannot be made. However, it will be

104 PLANT PHYSIOLOGY

helpful in the autumn to list the plants most susceptible to
injury and those that suffer least from frost.

147. Growth. In the one-celled plants, or plants
made up of undifferentiated cells, growth is a function of
every cell. It enlarges up to a certain point and then
divides into two cells which enlarge and divide, etc.
In some cases the cell divides internally into many small
cells which enlarge until they reach the size of the parent
cell and repeat the process. The growth of a cell in-
volves a number of factors. Among these are the in-
crease in the amount of cytoplasm and sometimes a great
increase in the amount of cell sap, also the enlargement
of the cell wall in area and frequently also in thickness.
These cells are meristematic in many features. In such
plants we can hardly dissociate growth from reproduction.

148. In the more complex plants we find some parts
that are the seat of the growth, the growing points and
adjacent region and cambium layers, while the rest of the
plant practically ceases to grow. The reproductive
functions are carried on by special parts of the plant
which have nothing to do with its ordinary growth.
The growth in such plants takes place still by the
process of cell growth and division, but we find that these
differ considerably from the case in one-celled plants.
Thus near the tips of the growing points the cells in-
crease their cytoplasm and cell wall area so as to become
perhaps twice as large, and then divide and form new cells
as is the case in one-celled plants except that the cells
remain attached. Gradually, however, some of these
cells that by the formation of new cells have come to lie
further from the tip increase more and more in size
and are not so active in their division. This increase in
size takes place largely by an increase in size of the
vacuoles so that the cells contain proportionally less and
less cytoplasm, although probably the amount of cyto-

GROWTH 105

plasm actually docs increase, or decreases but little. In
other words the growth of the cell is mainly accomplished
by absorbing large amounts of water, the cell wall being
increased in area so as to keep pace with the increase in
volume. It is possible that in some cases where the
growth of the cell is very rapid the total amount of cyto-
plasm in the cell may actually be reduced in manu-
facturing the additional cell wall substance required.
In this growth we can distinguish three phases which can
be more or less clearly set off, viz., formative phase, phase
of enlargement and phase of differentiation or maturation.

149. Thus it comes about that at the growing root tip
or tip of the stem we can distinguish an area near to the
tip where growth is not very rapid but cell division is
taking place abundantly (i.e. the cells are in the formative
phase of growth), and another area into which the first
grades, and a little distance back from it, where the cells
are enlarging very rapidly and but little cell division is
taking place (i.e. the cells are in the phase of enlarge-
ment). This gradually grades off into that portion of
the root or stem where growth in size. is no longer oc-
curring but where the various tissue differentiations are
taking place (i.e. the phase of differentiation). In the
root these zones are well marked, while in the stem the
elongation may persist for a long while and may become
localized in nodes while the internodes cease to grow.
In this case the nodes usually retain some meristem and
possess the power of producing new cells as well as in-
creasing in size.

150. There are several factors that influence plant
growth. There must in the first place be sufficient food
stuffs to enal)le the cells to manufacture the necessary
new cytoplasm and cell wall. Then there must be
sufficient organic substances to produce the osmotic

106 PLANT PHYSIOLOGY

pressure necessary to take in the requisite large quanti-
ties of water that increase the bulk of the cell so greatly
during the phase of enlargement. Then sufficient food
substances must also be present to supply in the process
of respiration the energy necessary for growth. Further-
more the water supply must be ample, for growth ceases
immediately if the cells of the plant are not kept strongly
turgid, hence the reason that in a dr}^ season a plant may
remain alive for months on a minimum of water, but
scared}^ grow at all. The temperature also has a
marked influence on growth. The cardinal points of
temperature for growth are often quite different from
those for photosjmthesis or respiration in the same plant.
In some plants that come up through the snow the
optimum temperature for growth may be but little
above 0° C, while in Indian corn, for example, the opti-
mum lies between 37° and 42° C.

151. The effect of light upon grow^th is noteworthy.
Careful records of the rate of growth with automatically
recording instruments show that, given constant tem-
perature, the growth is much more rapid in darkness
than in light. If the rays from the blue end of the
spectrum are excluded growth is scarcely if at all checked
by light. The absence of light, however, although favor-
ing the elongation of the plant, prevents the normal form-
ation of leaves. This is possibly due in part to lack of
food, but it seems probable that a definite stimulus on the
part of light is needed before leaves will be produced in
the normal form and size. Plants kept in the dark become
much elongated (remaining pale in color) with only rudi-
ments of leaves. Such plants are said to be etiolated.
To a certain degree this is useful to a plant in that a tuber
or seed buried too deep produces an abnormally elongated
shoot which may thus be able to reach the light.

CIROWTH 107

152. The amount of growth in a given length of time
varies with the plant. Sonic trees in dry regions, e.g.
Ccrcocarpus parvifolius, the mountain mahogany of
Colorado, may scarcely attain a height of two meters in
one hundred j-ears, while a morning glory vine (Ipomoea)
may grow 17 cm. per day, a bamboo shoot 60 cm. per
day and a stamen of Avheat 1.8 mm. per minute, i.e. at a
rate of over 25 meters a day (but of course this rate of
growth actually lasts only a few minutes).

153. As growth occurs in a stem or root various
tensions arise owing to the unequal amount of growth in
different parts. Thus the pith of many plants (especially
herbaceous ones) elongates considerabl}" when removed
from the stem and the surrounding portions shorten a
little. While they remain in the plant the result is that
certain parts of the plant are stretched and the pith
compressed, w^hich stiffens the plant just as in a turgid cell
the stretched cell wall pressing against the osmotic
pressure within the cell renders the cell stiff. Bark of
trees usually shows a circumferential stretching also
which helps to keep the stem rigid.

Laboratory Studies, (a) Examine plants of Protococciis
(one to few celled) or of Spirogyra (chain of cells). Cells of
different sizes will be found but the largest cells are
rarely more than twice as large as the smallest ones.
Here each cell grows and divides for itself and in the
case of the first the cells soon separate, forming new
plants.

(6) Take a germinated seed of Indian corn, sun-
flower or other plant and on a rapidly growing root,
using a thread dipped in India ink, mark lines 1 mm.
apart making the first mark 1 mm. back from the tij)
(special markers for this i)urpose may be bought, but
although more convenient are not indispensible). Place fu.. 47.
this seed on moist cotton with the marked root J~r^J,"„*i5i'
directed downward and cover with a bell jar to cxpcri-
prevent drying out. Examine at intervals of several

108 PLANT PHYSIOLOGY

hours to determine in what segment so marked the most
rapid growth occurs. It must be remembered that tliis zone
of most rapid growth is rapidlj^ passing down the root all
the time, keeping about the same distance back from the root
tip, so that the marked root must not be left too long before
examination or the conclusions will be faulty.

(c) Attach the thread of an auxanometcr (instrument for
measuring growth) to the tip of a leaf just growing out of an
onion or hj-acinth bulb or to the tip of the flower scape of such
a plant, or just below the cotyledons of a sunflower seedHng.

If possible have the plant in a situation where
it is almost equally lighted from all directions.
If the instrument is not self-recording readings
should be made every one or two hours during
the day and night. If the records are automat-
ically made the readings need not be taken during
the course of the experiment but the records can
be studied afterward. So far as possible keep the
nomete/Sr* temperature constant. Interesting results may
be obtained by varying the temperature while
keeping the intensity of the light the same or bj^ varjdng
the hght with constant temperature. The effect of keeping
the soil very wet and very dry may also be compared.

(d) Observe a potato that has started to grow in a dark
corner of a cellar and compare its growth with that from a tuber
that has been grown in full hght.

(e) Place potted plants under bell jars as follows: (1) clear
white glass, (2) double bell jar with space filled with saturated
K2Cr207 solution, (3) double jar with space filled with saturated
cuprammonia solution. Compare the growth. Note also the
differences in the color and development of the leaves. The
cuprammonia solution is prepared by carefully adding to a
copper sulphate solution sufficient ammonia to precipitate all of
the copper as copper hydroxide but not adding enough ammonia
to redissolve the precipitate. Filter and wash the precipitate
and then dissolve it in strong ammonia using only enough of
the latter to completely dissolve it. This must not be done
on the filter paper as the solution thus formed dissolves cellulose.

(/) The rate of growth under normal conditions can be meas-
ured by an auxanometer or with a horizontal microscope or in
the case of rapidly growing plants, such as Indian corn, morn-

REPRODUCTION 109

ing glory vine, bamboo, etc., it can be measured even^ day with
a ruler. ]\Iake and record such measurements night and morn-
ing for several kinds of plants.

154. Reproduction. This is the ultimate function of
all plants. For many it is the final function of hfe, the
death of the old individual occurring with the formation
of the new individual. It is perhaps to be considered as
the final act of growth toward which all development
of the plant has been leading.

155. In many of the lower plants, especially those
that are undifferentiated, reproduction is nothing more
than cell division followed by separation of the cells thus
produced. In the more differentiated plants, however,
we find certain cells set aside for reproductive purposes.
These may be at first ordinary vegetative "cells that
later take up the reproductive function, or they may be
destined for the latter from their beginning.

156. Very early in the vegetable and animal kingdoms
two types of reproduction become recognizable, the
asexual and the sexual. The former consists essentially
of the division of the plant, or of the separation from it
of single cells or groups of cells or even whole plant
members. By further growth these parts thus pro-
duced become like the parent plant. Not to be confused
with true asexual reproduction, is the development
of the gametophyte from the spores produced by the
sporophyte.

157. Sexual reproduction is fundamentally different
from asexual reproduction in that there is requisite the
union of two distinct cells (or at least their nuclei) to
form a single cell, the zygote. This may develop
directly into a new plant or into a mass of cells (the
spore fruit), which produces onlj^ eventually the repro-
ductive cells, which give rise to the new plants. The

no PLANT PHYSIOLOGY

uniting cells (gametes) may come from the same or
from different plants, indeed they may be sister cells,
i.e. formed by the division of one cell, but this is not
common. They may be alike (isogamous) or unlike
(heterogamous).

158. As we proceed from the simple to more complex
plants in the study of sexual reproduction we find entering
in, the principle of "increased parental care." In the
lowest plants with sexual reproduction the gametes
unite outside of the parent plant, at a higher stage one
gamete (the egg) is retained in the parent plant and is
fertilized by the motile sperm. Still higher the egg is
surrounded by special protective structures (cystocarp,
archegone, etc.) and produces no longer a simple zygote
but a spore fruit w^hich may also be included in the pro-
tective envelope. A still higher stage is whei'e the
spore fruit is so highly differentiated that it becomes a
separate generation (sporophyte), capable of separate
existence, similar to or differing in appearance from the
parent generation (gametophyte). Highest of all we
find the sporophyte becoming the prevalent generation,
the gametophyte being retained within its protective
tissues and only developing far enough to permit sexual
reproduction to occur.

159. Each gamete of the same species has the same
number of chromosomes in its nucleus. The cell re-
sulting from their union, the zygote, has double this
number (diploid number). Where a zygote is formed
which gives rise directly to a plant like the original one,
the reduction in the number of the chromosomes from
the diploid to the haploid number (see paragraphs 35
and 160), occurs with the germination of the zygote.
Where a spore fruit or sporophytic generation occurs its
cells retain the diploid number and the reduction divi-

REDUCTION OF CHROMOSOMES

111

sion does not enter in until tlie spores are being produced,
which give rise to the sexual generation (gametophyte).
This latter has the haploid number of chromosomes in
its nuclei. We must thus distinguish carefully between
typical asexual reproduction, where the resulting plant
is, as it were, but a separated part of the mother plant,
and the formation of a gametophytic generation from
the spore produced in the sporophytic generation. In-
deed each of these generations may have typical asexuiil
reproduction leading simply to the formation of other
plants of the same generation.

160. After the union of gametes the chromosomes
from the two gametes remain separate, but usually the
corresponding chromosomes from each gamete lie close
together. In the reduction division the chromosomes
gather at the equator of the spindle as double chromo-
somes, in all probability representing the two corre-
sponding chromosomes from the two gametes. Before
this stage is reached, and while the chromatin matter
is found on fine
threads, there is a
characteristic bunch-
ing together of these
threads (called the
synapsis) in the course
of which it is sup-
posed that certain
characters become ex-
changed in the corres-
ponding c h r o m o -
somes. These double chromosomes split apart and as
single ones go to the opposite poles. There are thus
entering into each daughter nucleus only as many chromo-
somes as were originally present in the gametes. These

Fig. 49. — Reduction division (diagrammatic).

112 PLANT PHYSIOLOGY

chromosomes do not, however, correspond exactly to the
originals, for in the synaptic stage there has been an
exchange of some characters. At the next division the
nuclear phenomena are like those of the ordinary
vegetative division.

161. These peculiarities of haploid and diploid chro-
mosome number, reduction division, and ordinary (so-
matic) division of the nuclei, as well as other observed
phenomena of heredity, have led most investigators to
conclude that the chromosomes are the chief bearers of
heredity. In sexual reproduction, then, is found a means
of combining in the most complicated ways the minute
or larger differences found in the different parents.

162. Variations. Hardly any two plants are exactly
alike. The differences are of two kinds: (1) a response
of the plant to slightly or greatly different environ-
mental conditions, and (2) a difference in the constitu-
tions of the plants that leads them to respond somewhat
differently in morphological or physiological characters
when exposed to the same conditions. These latter
are the only ones that demand attention here. They
may be slight differences that are apparently not inherit-
able (i.e. although the somatic or vegetative cells are
somewhat different the sexual cells are not so), or there
may actually have taken place a change in the constitu-
tion of the protoplasm that affects also the reproductive
cells, so that the heredity carriers (probably the chromo-
somes) are slightly different in the different plants.

163. Gregor Mendel, in 18G6, published a paper in
which he pointed out that certain characters that differed
in the two parents and that are mutually exclusive
(i.e. that allow of no intermediate form) would appear in
the second generation in a pure form in some of the
plants. This is now explained by the phenomena taking

VARIATIONS 113

place in connection with the reduction division, where
during synapsis certain character-determining units in
the chromosomes may become exchanged, so that the
chances are about equal whether one or the other char-
acter from respectively one or the other parent will be
present in the new cell. Mendel found that about one-
fourth of the second generation plants show a given char-
acter from one of the original plants and one-fourth the
character from the other plant, while one-half still re-
tains (at least potentially) both characters, although only
one is visible, it being ''dominant" over the other char-
acter which is ''recessive.'^ That both characters are
present is shown by the fact that seeds from this half
produce plants which divide up again into one-fourth,
one-fourth, and one-half, etc.

164. In sexual reproduction the various differences
borne by the different chromosomes, or perhaps more
accurately by the unit structures of the chromosomes,
will be redistributed among the daughter and grand-
daughter plants in new combinations. Some of these
will be advantageous to the plant, and it will succeed
better and be able to reproduce more freely; other com-
binations may be less favorable, and the plants with
such combinations will have a poorer chance in the
struggle for existence, and will not reproduce so freely.
As a result, ''Natural Selection'^ sorts out those whose
combinations are most favorable. Thus we see that
sexual reproduction forms a means by which the con-
stantly arising individual differences (and why they arise
we do not know) are made use of in the most manifold
combinations, the most favorable of which are perpet-
uated. This is what was called by Darwin "The
survival of the fittest."

165. These inheritable variations may be slight or

lU PLANT PHYSIOLOGY

they may be strongly marked. They are often called
"mutations" to distmguish them from the non-in-
heritable variations. If the plants showing them are
considerably better able to exist, they will rapidly crowd
out the less favorably constituted plants, and thus a
new species will replace the old. Under other environ-
mental conditions this new feature may be less favorable
and so the older form will persist. Thus we find plants
with all sorts of differences or what we call ''species,"
all over the world. Some plants have changed but little
apparently from their primitive structure, as they were
able to persist in that form under certain conditions,
while some of their descendants, it may be, have pro-
gressed far along the evolutionary line. Thus we find
the Vegetable Kingdom made up not only of the ends of
long evolutionary branches but also of stragglers that
have progressed only a very little way, and of those that
have grown further before branching out in some other
direction. It is this fact that enables us to attempt to
show the probable course of evolution (phylogeny) of the
Vegetable Kingdom in our arrangement of the plants now
existing.

166. The conditions that favor reproduction have
been worked out for a good many plants, but are un-
known for the vast majority. It seems that those con-
ditions that favor continued vegetative growth, such as
an abundance of water and all foods, tend to delay or
prevent reproduction. On the other hand, there must
usually be a certain amount of food stuffs stored up.
If these can be prevented from accumulating, or can be
used up by promoting vegetative growth, reproduction
will be held back. In many cases, however, the repro-
ductive stage comes on in spite of all efforts to keep it
back, showing that not all the factors are known.

PLANT BREEDING 115

167. The breeding of plants is an application of the
principles of reproduction and heredity to the production
of plants with certain desirable characteristics. In-
stead of waiting for the chance production of a desirable
type of plant, the plant breeder either grows many plants
in conditions under his control and selects for further
propagation those he deems most desirable (method of
selection), or he takes two distinct plants, each with
certain characters that he desires, and crosses them, and
grows the progeny in large numbers for several generations
until by the laws of chance in the distribution of the
unit character determinants there appears a plant
combining the desirable characters of the two parents.
This is the method of hybridization or crossing. The
discovery by Mendel of the segregation of characters by
definite laws of numbers (see paragraph 165) has given a
great impetus to this line of work.

Laboratory Studies. Not much can be done in the way of
laboratory work on this subject. In the study of the different
forms of plants in the later chapters of the book, the points
emphasized in the foregoing paragraphs should be borne in
mind. A few suggestions are made for observations on the
part of the student.

(a) Find and compare carefully a dozen different plants of
timothy {Phleinn prateiisc), red clover {Trijolmm pratense),
ribbed plantain (Plantogo lanccoJata), etc. Select those
plants of the same age and from as ncarlj^ as possible the same
soil and growing under the same environmental conditions.
Note how thc}^ differ in height ; number, size and sluii)e of leaves;
size of flower heads; number of flowers in the head; amount of
hairiness of various parts, etc.

(6) Compare plants of the same kind grown in sun and shade,
in dry and moist soils, in barren and on fertile ground, for
differences due largely to the environment. Note the (Hffcr-
enccs in the times of flowering and of ripening of seeds, as well
as the structural differences.

116 PLANT PHYSIOLOGY

168. Movements. Plant movements are of four
kinds: (1) hygroscopic, (2) protoplasmic, (3) turgor^
and (4) growth movements. The first is a strictly
physical phenomenon of dead cells, the last three are
functions of living cells or tissues.

169. Hygroscopic Movements. Cell walls have a
great power of iml^ibition of water, and when filled with
water have a greater volume than when dry. In many
plant organs certain cell walls have a greater power of
imbibition than others, or in some cases certain tissues
on one side prevent the organs from elongating or con-
tracting on that side. The result in either case is that
as the cell walls absorb water or give it up a curvature
takes place. This may be a simple bending or may consist
of twisting. Mostly the organs straighten out on becom-
ing wet and curve or twist as they dry. In some cases the
differences in the moisture content of the air are sufficient
to produce movements. These movements are of value to
the plant in opening reproductive organs (sporangia, seed
capsules, etc.) or in enabling seeds to penetrate the ground
(twisting of the long awn of porcupine grass, Stipa).

170. In the case of the sporangia of the common ferns
(Potypodiaceae), the cell lumen as well as the walls is
filled with water. As the water evaporates through the

cell wall, the cell

Ob, O,

- o^

'^^^ <>

contracts to compen-
?=?^^I'VOo sate for the water
lost. As the walls
are thin and collap-
sible on one side

Fig. 50.-Dispcrsal of fern spores. Ouly, and thick but

flexible on the
others, the cell contracts more and more toward the thin
side until the row of cells instead of being in a nearly

PROTOPLAS]\IIC MOVEMENTS 117

complete circle with the thin wall at the outside, is bent
back into almost a reverse circle, the whole row being now
under high tension. As the evaporation proceeds, further
contraction becomes impossible, and the collapsed thin
cell walls become dry in spots. These dry spots are per-
meable to air, which rushes into them and permits the
whole ring to snap back with extraordinary violence,
flinging the spores a comparatively long distance.

171. Protoplasmic Movements. We may distinguish
two types of these, the movements of the cytoplasm
within the cell and the movement of the cell as a whole,
due to the motion of the cytoplasm or special parts of it
(cilia or flagella).

172. The motion of cytoplasm within the cell seems
to be a normal phenomenon in all living cells whose
protoplasm has imbibed enough water to make it rather
liquid, i.e. in all active cells. It is probably
entirely absent in so-called dormant cells, such ^
as the cells of dry seeds, etc. In many cells it
cannot be distinguished except by special methods.
The motion may consist of a rotation of all the
cytoplasm of the cell except a thin layer against
the cell wall (as in Chara and Nitella), or of
large streams in which chloroplasts and cell inclu- pio. 51.
sions are swept along (as in Philotria), or in cur- i^nTpfo-
rents in the parietal cytoplasm and delicate (tEIS
strands crossing the vacuole (as in Tradescantia) , *'^°***^-
or it may consist of rather local disturbances.

173. Of especial interest are those movements by
which the nucleus is carried from one part of the cell to
the other. Thus in a cell that is growing rapidly on one
side or secreting abundantly at one side, the nucleus
is often carried to the point of activity. The chloroplasts,
too, change their position with reference to the light. If

118 PLANT PHYSIOLOGY

tlie light is dim, they are carried to the top or bottom
of the cell, where they will get the strongest light broad-
side. If the light is too strong, they are carried to the
sides of the cell, where the light will only strike them
edgewise.

174. The locomotion of cells is accomplished mostly
by the lashing movements of slender cytoplasmic pro-
jections from the surface of the naked cell. If few in
number and long, they are usually called fiagella. If
numerous and rather short, they are called cilia. When
single or few, they are usually attached at the anterior

end of the cell. A few plant cells
move by amoeboid motion, i.e.
send out processes or lobes into
which the whole protoplasm flows.
The cells of diatoms (Bacillario-
ideae) are provided with cell walls
of cellulose so filled with silica as

Fig. 52.— Flagellate cells, , . , ,. i i -,,1

(uiothrix, pieurociadia. to bc nou-clastic and brittle.

JMarchantia, Struthiopteris, ^ ,. , ,, , ,

Zainia). lu some diatoms the protoplasm

comes to the surface through a
longitudinal slit, the raphe, and its longitudinal motion
in this slit is probably the cause of the motion of the cell.
Finally, must be mentioned the motion of some diatoms
as well as desmids, and some of the blue-green algae
(e.g. Oscillatoria) which is ascribed to the secretion of a
slime through the cell wall. The bending of the
Oscillatoria filaments, however, may be due to proto-
plasmic contraction.

175. All of these movements are dependent on an ample
supply of oxygen, and cease very quickly in its absence.
The usual cardinal points of temperature can be found
for these as well as for other functions of the cell. Ap-
parently the movements within the cell are of use in

LOCOMOTION OF CELLS 110

distributing various food products as well as other sub-
stances throughout the cell.

176. In motile cells there is observable a response
in direction of the movements to various external stimuli.
Thus many cells swim toward the light, or away from it
(positive and negative phototaxy). Others swim to-
ward or away from various chemical substances (e.g.
food matters, acids, etc.) diffusing through the water,
this being called chemotaxy. In many cases a degree
of light or of concentration of a chemical that causes
positive reaction, when increased beyond a certain point
repels the cell. It is not always the case that harmful
chemical substances (poisons) repel the cell, although
usually this is the case.

Laboratory Studies, (a) Insert the point of the fruit of
porcupine grass (Stipa) into a cork or fasten the fruit of cranes-
bill (Erodium) to a cork with a drop of seahng wax, with the
main shaft of the fruit upright, and place a marker opposite
the tip of the bent portion. Place a bell jar partially lined with
wet filter paper over it and note how it changes its position and
the direction of the motion. Remove the bell jar and note the
change in the direction of motion. By spraying a fine mist on
the specimen a lively movement will be obtained.

(b) Mount several ripe sporangia of a fern in a very little
water without a cover glass and watch the motion as the water
dries out.

(c) Examine some of the end cells of Chara or Xitella for
rotatory movement of cytoplasm, the leaf of Philotria for large
streams of cytoplasm carrying the chloroplasts with them, the
stamen hairs of Tradescantia or the stem hairs of petunia,
tomato or watermelon for more delicate strands of streaming
cyto])Iasm.

(d) With some of the foregoing test the effect on the move-
ment of cold (laying on a block of ice) and heat (up to 40° or
45° C), examining again at room temperature.

(e) Place some green felt (Vauchoria) that has been growing
on the surface of the ground in a dish of water. Often this will

120 PLANT PHYSIOLOGY

cause it to form its multiciliate zoospores. Study their motion.
Study also zoospores of Ulothrix, Chaetophora or Draparnaldia
which can often be obtained by bringing these algae into the
laboratory and leaving them over night in a dish of water.
Often they will collect at the side of the glass next to the hght.

(/) With sharp scissors cut off as much as possible of the
mycelium (fungous threads) of Saprolegnia growing on a fly or
piece of meat thrown into a dish of algae. Place it in a dish of
clean water and after a few hours hang a small piece of meat in
the water at one side of the dish. After a comparatively short
time the zoospores produced will be found congregated around
the meat (chemotaxis).

177. Turgor Movements. Many plant organs change
their position or become curved by the change in turgor
of the cells on one or both sides of the organ. Thus at
the base of the petiole of the leaf of the sensitive plant
{Mimosa pudicd) there is a strongly developed mass
of thin-walled cells, the pulvinus. When the cells on the
lower side are turgid the leaf is held out horizontally or
inclined upward. In response to various stimuli these
cells suddenly allow their water to escape into the
intercellular spaces, thus losing their turgor and contract-
ing considerably. Apparently the cells on the upper
side of the pulvinus take up this water very quickly,
thus becoming turgid in their turn. This process takes
place very rapidly and results in a quick dowmward
bending of the leaves. It is by a similar arrangement
that the two halves of the leaf of the Venus fly-trap
{Dionaea muscipula) snap together quickly enough to
catch insects lighting upon them, or that in the case of
the sundew (Drosera), when an insect is caught by the
sticky mass on one of the so-called tentacles, the ad-
jacent ones bend over until they too touch the un-
fortunate victim and the whole leaf gradually closes in
on it. The movement of the stamens in the flower of
barberry (Berberis) is also due to turgor changes as are

TURGOR MOVEMENTS 121

the constant movements of the lateral leaflets of the
leaves of the telegraph plant {Desmdoium gyrans).

178. Some turgor movements are so-called auton-
omous movements; i.e. they seem to be due to internal
causes and not caused by external stimuli. Such seems
to be the case in the movements of the leaflets of Des-
modium referred to above. The haflets of red clover
{Trifolium pratense) show a similar rising and falling,
but instead of requiring only a few seconds as is the case
with Desmodium, require several hours. It is possible
that these so-called autonomous movements are due to
external stimuli which have not yet been recognized.

179. Most turgor movements are in response to
some recognized stimulus. Whereas the hygroscopic
movements are the direct physical result of the in-
creased or decreased moisture in the surrounding air,
the movements in response to a stimulus are not the
direct physical effects of the energy exerted by the
stimulus but are due to energy stored up in the tissues
which is released by the stimulus as the energy of the
gunpowder is released by the chain of events between the
pulling of the trigger and the discharge of the gun. As
the strength with which the trigger is pulled has no
influence upon the energ}^ applied to the bullet, so the
intensity of the stimulus has no direct effect upon the
vigor of the movement resulting from it (except in so far
as a more vigorous stimulus may reach more cells and so
release more energy in that way).

180. The most frequent stimuli for turgor movements
are variations in temperature and light. Examples of
this are the so-called sleep movements of leaves of clover,
Oxalis, Mimosa, etc., and probably all leaves that have a
pulvinus at the base of the leaflets or of the petiole.
On the other hand the sudden movements of the stamens

122 PLANT PHYSIOLOGY

of barberry, the rapid closing of the leaf halves of
Dionaea, the closing of the leaflets and dropping down-
ward of the leaves of Mimosa are responses to the stimulus
of contact. In the case of the sundew the movement of
the tentacles may take place both in response to contact
or to the presence of certain chemicals such as ammonium
sulphate, proteins, etc. It is worthy of note that the
stimulus may be applied at a distance even of several
centimeters from the point where the change in turgor
occurs, i.e. the plant tissues are able to transmit a stimu-
lus for a considerable distance. Kone of these move-
ments will take place except under the proper degrees of
temperature, moisture, etc.

Laboratory Studies, (a) Observe a plant of Desmodium
gijrans at a temperature of between 20° and 30° C. The
rapidity of the rotation of the leaflets will be found to vary
with the temperature, degree of illumination and other factors.

(6) Observe clover and Oxalis leaves by night and by day.
Compare also the leaves of Mimosa, Robinia, etc., in light and
darkness.

(c) Touch one of the three bristles on the surface of a leaf
half of Venus fly-trap (Dionaea). Note the sudden closing of
the leaf. The temperature and humidity must be rather high
or it will not respond well.

{(I) Toucli a leaf of a sensitive plant {Mimosa pudica) at
the under side of the pulvinus. Touch or sHghtly pinch other
leaves of the same plant at various points. Apply the flame
of a match to the end of one of the leaflets. Note in this case
the progressive closing of the leaflets followed by the dropping
of the whole leaf and in many cases of the nearest leaves above
and below.

(e) Place a grain of sand on the tip of a tentacle of a leaf of
sundew (Drosera). Note the degree of movement in the sur-
rounding tentacles. On a tentacle on another leaf place a tiny
piece of meat or a very small crystal of ammonium sulphate and
note the movements of the adjacent tentacles.

181. Growth Movements. Many plant movements
are the result of unequal growth on opposite sides of an

NUTATION 123

organ. Here again can be distinguished autonomous
movements whose stimuU if external are not recognized
and paratonic movements in response to recognized
stimuli.

182. Probably the most widely prevalent autono-
mous growth movement is that called nutation. If a
firm long bristle be fastened to the tip of a growing stem
or root tip and its end be observed under a microscope
or in some cases with the unaided eye it will be found to
describe a very irregular somewhat circular figure. This
is really a low spiral for the tip is advancing at the same
time that it rotates. This is the form of nutation that is
frequentl}^ called circumnutation. This
movement is due to the fact that the
zone of most rapid growth is not equal
on all sides but growth takes place more
rapidly at one side, this region of most
rapid growth passing around the stem and
slowly advancing so that it remains at a ^ ^„ ^•

^ ° Fig. 53. — Cir-

const ant distance from the tip. The tip cum nutation

T 1 c 1 • 1 (Ipomoea).

is then bent a little away from the side
where the most rapid growth is occurring, hence its nuta-
tion. The opening of buds is due to greater growth on
the upper than on the lower side of the leaf bases. This
may be followed by the reverse and so on until finally a
state of balance is reached. This is another form of nuta-
tion. The rotation of free horizontal ends of twining
plants is often, perhaps not with correctness, regarded as a
type of nutation. When such a rotating shoot strikes a
vertical support it keeps on rotating and thus winds
around the support while at the same time its negatively
geotropic response (see paragraph 186) is sufficient to
cause the stem to ascend spirally. IMost ]ilants rotate in
a direction opposite to that of the hands of a watch when

124 PLANT PHYSIOLOGY

seen from above, but a few plants rotate in the opposite
direction. Some botanists regard the whole rotary
movement of such plants not as a form of nutation but
as a special form of geotropic response.

183. Those growth movements due to the response
to recognized stimuli are often divided into tropic
movements where the organ affected is brought to lie
with its axis in some definite relation to the direction of
the stimulus, and nastic movements where one or the
other face of a bifacial organ is placed in some relation to
the direction of the stimulus. However, in view of the
fact that the general phenomena concerned are the same,
the}^ need not be sharply separated here.

184. The chief tropic movements of plants are
phototropism, geotropism, thigmotropism, chemotropism,
being responses respectively to the stimulus of light,
gravity, contact and chemical substances. Other tro-
pisms have been distinguished but will not be discussed
here. For all tropisms the point of curvature is the
region where the most rapid growth usually occurs. As
the result of the stimulus the growth is increased above
the normal rate on one side and sometimes even retarded
below the normal on the other with the result that a
curvature is produced. The perceptive region for the
stimulus may be distant some millimeters or even
centimeters from the zone of growth.

185. Phototropism may be illustrated by the action of
a plant illuminated on one side only. Usually the
stem of such a plant curves toward the source of light
(positive phototropism) while the leaves place themselves
so as to stand with their surfaces at right angles to the
source of the light (photonasty). Sometimes the cur-
vature is away from the light as is the case with most
roots and with the stems of some climbing plants, e.g.

GEOTROPISM 125

ivy (Hedera helix). This is negative phototropism.
Too great intensity of light may cause a positively
phototropic organ to become negatively phototropic.
A very small amomit of light scarcely perceptible to
the human eye is sufficient to induce phototropic cur-
vature in some plants. The effective rays of light
are those of the blue and violet portion of the spec-
trum. The perceptive region may be some distance
from the region of curvature. Thus in the seedlings of
oats the tip of the first leaf is the perceptive region while
the curvature takes place at a point near the ground.

186. Geotropism. If a seedling that usually grows
upright be placed in a horizontal position for a few hours
the tip of the stem will be found to be curved so as to be
directed upward, while the tip of the root will have
assumed a position directed downward, the remainder
of the stem and roots being horizontal. If the root tip
and stem tip have been previously marked with cross
lines at equal distances it will be found that the curvature
begins and is carried out by those regions of stem and root
respectively where the growth is usually most rapid and
the curvature has taken place by the more rapid growth
on one side than on the other. The main root, then, is
positively geotropic and the stem negatively so.

187. If the plant has been allowed to grow until
horizontal lateral roots have been produced and then is
placed with the main stem horizontal it will be found
that not only does the main stem curve upward and the
main root downward, but that the lateral roots, which
are now of course some of them directed upward and some
downward, wnll curve so as to occupy a horizontal position
again. Thus it is apparent that some stimulus causes
certain plant parts to grow toward, other parts away from
and still others parallel to the surface of the earth. Care-

126 PLANT PHYSIOLOGY

ful experiments have shown that it is with reference to
the direction of the force of gravity that these different
plant parts orient themselves.

188. Experiments have shown that by attaching
plants to a rapidly whirling wheel the centrifugal force
has the same effect as gravity and stimulates the main
root growth away from the center of the wheel, while
the growth of the main stem becomes directed toward
the center and that of the lateral roots at right angles
to the radius. On the other hand, if the wheel to which
a plant is attached be rotated very slowly with its axis
horizontal so that all sides of the plant are successively
exposed to the stimulus of gravity, the rotation being so
slow that the centrifugal force is negligible, the different
parts of the plant continue to grow in any direction they
may have happened to start. It is thus apparent that
the general form of the plant is largely controlled by
the stimulus of gravity as well as by the stimulus of
light.

189. The zone of curvature is that of most rapid
growth. The perceptive region may, how^ever, be dis-
tant some millimeters. Thus in the root it has been
shown that the root cap is the region of greatest percep-
tion. It has been suggested that the cells there contain-
ing starch grains are the perceptive cells, the different
position in the cell assumed by these starch grains in
response to gravity as the root is pointed in various
directions furnishing the stimulus which is communi-
cated from cell to cell to the growing zone. Here cer-
tain cells on one side are stimulated to grow^ more rapidly
than those on the opposite side until the root has assumed
its proper position, when the starch grains (statoliths)
will resume their normal position in the perceptive cells.
The similar starch-bearing cells in the perceptive regions

THIGMOTROPISM, CHEMOTROPISM 127

of stems have also Iwcn supposed to be such ''statocysts. ''

190. Thigmotropism. If a tendril be touched on one
side by some uneven object (not by a smooth object
like a very smooth rod or a drop of water or mercury), it
begins to curve very soon in the direction of that object.
At the very first this curvature, which may become
apparent within a few seconds, is undoubtedly due to
changes in turgor on the two sides of the tendril, but in
only a short time rapid growth sets in on the outside, and
the tendril winds around the object. Soon thereafter the
part of the tendril between the stem and the object also
begins to coil in a double spiral, this also being due to
unequal growth. Thigmotropism, as this phenomenon
is called, is exhibited by tendrils and by other parts of
plants that assume this function, such as the leaf stalk of
Clematis, peduncles of some plants, and whole shoots,
especially modified for this purpose, of other plants.
Special papilla-like cells have . been regarded by some
botanists as the organs of perception. The curvature of
roots toward or away from points of injury is possibly to
be considered as a special form of thigmotropism. It is
often called traumatropism.

191. Chemotropism. The hyphae (filaments of cells) of
many fungi and the i)ollen tubes of seed plants show a
peculiar growth response to the stimulus of various
chemical substances. Thus, many pollen grains placed
on a piece of moist filter paper will produce tubes
growing in any direction, but if a small crystal of cane
sugar be placed on the paper, some kinds of pollen
tubes will change their direction of growth and turn
directly toward it. Fungus hyphae show similar changes
in direction of growth when they perceive various sub-
stances in solution. In both cases certain substances
induce positive and others negative chemotropism.

128 PLANT PHYSIOLOGY

Of the same general class of phenomena is the so-called
hydrotropism, in which roots grow away from the dry
and toward the moist er air.

192. In all these tropisms the stimulus must be of a
certain strength, or it is not perceived. Even if strong
enough to be perceived, the stimulus must act for a
certain length of time before the plant has been suffi-
ciently affected to bring about a reaction. The stronger
the stimulus (up to a certain point), the shorter the time
that is necessary for it to act. The reaction to the stimu-
lus may be almost immediate, or it may not show itself
for some time. In fact, the stimulus may have ceased to
act upon the plant for some httle time before the plant
shows any response. Thus a root may be placed in a
horizontal position for fifteen to twenty minutes and then
restored to its normal vertical position. After a little
while the root will begin to curve and will attain quite a
marked curvature until the stimulus then produced by
the resulting abnormal position induces the root to curve
back again. In this case it usually swings too far in the
other direction, and does not finally attain its normal
position until it has made several such swings. Similar
results can be obtained with phototropism.

193. Among the nastic movements are the opening
and closing of flowers, in response to changes in tempera-
ture or illumination. These are accomplished by in-
creased growth at the base of the petals and sepals on
the inner or outer sides respectively. A change of tem-
perature of only one or two degrees is sufficient in the
case of the tulip to stimulate the flower to open or close,
as the case may be. Many plants, as long as their leaves
are still capable of growth, show so-called sleep move-
ments, which are not, like those of the clover (see para-
graph 180), due to changes in turgor, but to more rapid

NASTIC MOVEMENTS 12!)

growtli on one or the other side of the base of the petiole.
Such responses to changes in Hght and temperature cease
when the leaves have attained full growth, while those
due to turgor changes in the leaves that have pulvini
persist.

Laboratory Studies, (a) Fix a slender filament of glass or a
stiff bristle to the rapidly growing end of a shoot of Fuchsia,
geranium (Pelargonium), or verbena, using a drop of thick
shellac glue. Support a plate of glass in a horizontal position,
just above the tip of the pointer, and record, by making ink
dots on the glass, the position of the pointer at definite inter-
vals of time, say every ten minutes. A microscope may be
focused upon the tip of the pointer and the movement observed
in this way. In this and similar experiments the illumination
should be as nearly equal as possible on all sides.

(6) In a similar manner, the nutator}'- movements of a Iciif
may be observed by fastening a pointer to its tip, and observing
it with a horizontal microscope or by recording the position of
the pointer at successive intervals on a vertical glass plate.

(c) Nutation can be demonstrated also in the long stout
roots from seedlings of beans, peas, etc. These should be
placed so as to point directly downward, so as to avoid geo-
tropic curvature. The movement can be observed by placing
a mirror at an angle of 45 degrees under the tip, and focusing a
horizontal microscope on the tip as reflected in the mirror.

(d) Observe the rotatory movements of the horizontally
bent end of a shoot of morning-glory (Ipomoca) or hop (Humu-
lus). Note the time required to make a complete revolution.
The stem also nuist twist one whole revolution

for every turn the tip makes. Place an upright
stake in the way of the shoot, and note how the
climbing takes i)lace.

(<?) Germinate a mustard or sunflower seed
in the dark, and after the cotyledons have
escaped from the seed coat, place the seedling

in a hole in a cork, so that tiie root i)rojects Fh- o4.— Phoio-
below and the cotyledons above. Put the ^j;op'=^'"*^^i'^""'"^*"^
cork in a bottle so that the tip of the root
dips into water, or better stifl, into a nutrient solution (see

130 PLANT PHYSIOLOGY

laboratory study (b) after paragraph 146). Keep in the dark
until the stem and roots are both in a vertical position. Place
in a box, closed on all sides, except for an opening about 10
mm. wide at one side, and direct this opening toward a win-
dow. Note the direction of curvature of stem and roots, as
well as the region where the curvature occurs.

(/) Perform experiments similar to the foregoing, placing
orange-red glass or deep blue glass in front of the opening, and
note the results.

(g) Sterilize some fresh horse manure in a steam sterihzer
to destroy all the fungi, and inoculate with the manure mold,
Pilobolus. When the sporangia of this are about to be formed,
place the dish containing the culture, micovered, in a dark box,
tilting the dish at an angle of 45 degrees toward one side, where
a small window about 2.5 cm. in diameter is left open to admit
light, but covered on the inside with a glass plate. Place the
box in such a position that the Hght can enter the window. The
sporangia will direct themselves toward the light and discharge
their spore masses, which will stick to the glass covering the
window. Only a few shots will fail to hit the ''bull's eye"
if the distance from the dish of the fungus to the window is
not more than 10 to 20 cm., although these are discharged with
considerable accuracy much further than that. Try the effect
of different colored glass on the accuracy of the aim.

(h) Germinate a number of seeds of
broom-corn millet or proso {Panicum
miliaceum) in the dark, in a pot of earth.
When they have attained a length of 1 to
2 cm., cap the tips of half of the seed-
lings with httle caps of tinfoil, made over
the point of a pencil, and then gently
Fig. o5.-Phototropi3m ^lippcd ovcr the tip of the sccdling and
experiment {h). pinchcd in placc. Set the pot in the

box used for experiment (e), and note the
result. Almost as good results can be obtained by using oats.
{i) Germinate seeds of bean, sunflower, mustard, etc. After
the seedlings show well-developed cotyledons, fasten several of
them by their middles in a horizontal position, under a bell-jar
over water, so as to keep the air moist and prevent the seeds
from drying out. Keep in a dark place for a few hours and note
the results.

LABORATORY STUDIES 131

0') Grow a bean seedling in water culture until some of the
horizontal roots have developed a little way. Then place the
main root horizontally as in (i). Note the effect on the main
and lateral roots and stem.

(k) Plant seeds of Indian corn or beans 1 or 2
cm. beneath the surface of the soil, in a completely
filled flower pot. Fasten a coarse wire netting over
the top of the pot, and invert it, putting it on an
iron tripod, standing in a plate of water, and place a
bell jar over the whole, to keep the air moist. After
a few days the roots will emerge from the soil into the
air in response to the stimulus of gravity, while the menuiT.""
stems grow on up into the soil.

(l) Place a flower pot with a growing plant in a horizontal
position. At the same time place another one with a similar
plant horizontally in a khnostat, so that it rotates slowly with
the axis of rotation horizontal. Keep both in a dark room
twenty-four hours during the process, and then compare the
plants. (A klinostat is an apparatus worked by clock-work,
which rotates a flower pot fastened to it at a
slow rate, being arranged so that the axis of
rotation may be in any direction desired. A
simple klinostat can he made by removing
the longer hand of a clock and fastening to the
Fig. 57.— Geo- pinion a stiff horizontal wire, supported, if need
menrcJ). ^^^^"" bc, at the other end. At the middle of the
wire may be placed a large cork, to which seed-
lings can be attached. With a small clock it is impossible to
use a flower-pot, as it is too heavy, and so instead the seedlings
will be fastened to the edge of the cork, and since they are
exposed to the stimulus of gravity from successively different
directions, they will show no gcotropic curvature. In home-
made apparatus of this kind the portion including the cork
with the attached plants ought to be so enclosed that the plants
will not dry out.)

(m) Place seedlings at the edge of a horizontal wheel that
can be rotated very rapidly (centrifugal apparatus). When the
centrifugal force much exceeds the force of gravity, the roots
will grow almost directly outward and the stems almost directly
inward. If both are equal, the roots will be directed downward
and outward at an angle of 45 degrees, and the stem upward

132 PLANT PHYSIOLOGY

and inward at the same angle. If the wheel is rotated in a
vertical plane, the effect of gravity is entirely eliminated, for
it acts on all sides in succession, and it is only the centrifugal
force that comes into play. (Such an apparatus with the wheel
rotating in the vertical plane can be con-
structed by using a stout knitting needle for
an axis, the bearings being little cups of glass
made by sealing and cutting off short the end
of a glass tube. These are inserted into corks,
fastened to two upright supports. At the
center of the knitting needle is placed a large
cork with short knitting needles radiating in
troTsnf^'ex^eri- ^^^^ directions in a plane at right angles to
ment (m). the main axle. The ends of these hold corks,

which are connected to each other by a wire,
which forms the circumference of the wheel. On this wire are
strung a number of small cork disks. A stream of water is
directed at these disks, and causes the wheel to rotate at a high
speed. Seedlings to be experimented with are pinned firmly
to the cork disks.)

(n) IMake a thin section of a root cap of a growing root,
stain with iodine to make the starch grains more ea^y visible,
The cells containing them are supposed by some botanists to
be the perceptive cells for gravity (statocysts).

(o) On a vigorous plant of cucumber or squash or pea, make
the following experiment with the tendrils. Place a very
smooth glass rod in contact with one tendril, and a rough stick
of the same diameter in contact with another equally developed
one. Note the time in each case before the first curvature is
noticeable and until the tendril has made one complete turn
around the object. Note wdien the formation of the coils
between the object and point of attachment of the tendril
first begins, and observe how a twisting of the tendril is avoided
as these coils develop.

{])) Wet a piece of filter paper with Sachs' culture solution
and sow on it fresh pollen grains of various kinds, keeping the
different kinds on different parts of the paper, but all at about
the same distance from the center. Cover to prevent evapo-
ration. After a few hours, examine and if germination has
occurred, place a small crystal of cane sugar at the center.
Examine every two or three hours, and note when and where

PATHOLOGY 133

and for what kind of pollen clicniotroi)ism first boconies ai^jKir-
ent. The experiment can be varied by placing the stigmas of
one of the flowers at the center instead of the crystal of sugar.
It will attract some of the kinds of pollen tubes and have no
effect on others. (The pollen grains and their germination
can be observed much more easily if, in place of the filter paper,
the following be used: To a measured quantity of boiling culture
solution, sift in with constant stirring enough agar powder to
make a 2 per cent, solution. When thoroughly dissolved, pour
it into petri dishes and cover, and allow to cool. On the jell}--
like mass thus produced the germination of pollen grains can
be observed very easily.)

(q) In the spring bring into the laboratorj^ buds of tulij) or
crocus, just about to open. In the w'armer air thc}^ will soon
open by increased growth on the inner surface of the bases of
the petals and sepals. When fully opened, place in an ice-box
or out-of-doors on the window ledge, and ver}^ soon increased
growth on the outside will cause them to close.

(r) Observe growing plants of sunflower (Helianthus), lamb's
quarters (Chenopodium), etc., by day and by night, and
notice the different leaf positions assumed by the younger
leaves. The fully developed leaves will show little or no change
of position.

194. Pathology is the study of the abnormal develop-
ment and functioning of a plant. It is in its widest as-
pect abnormal physiology. As usually studied, however,
it is the determination of the cause of and means of pre-
vention of certain plant diseases. Since most plant
diseases that have been studied are caused by fungi,
pathology as taught is often but a study of mycology, in
which parasitic fungi alone are considered. These views
of pathology are in reality only partial views, and do not
take the real scope of the subject into consideration.

195. Since abnormal functioning often leads to abnor-
mal structural development it is necessary to study not
only the al)normal functioning of a plant but also the
abnormal structures produced by the diseased conditions.
Thus we can distinguish cases in which cells or tissues do

134 PLANT PHYSIOLOGY

not. reach their full size or number (hypoplasy), orinwhich
individual cells or whole tissues are enlarged above the
normal size (hypertrophy), or in which the cells are ab-
normally increased in number (hyperplasy). In some
cases cells destined to produce one kind of tissue are
changed into other kinds by the pathological conditions.
Furthermore, the internal structures of the cell may be
modified. The chloroplasts may be increased in number
and size or. diminished or apparently wholly suppressed.
The nucleus may be enlarged and changed in shape or
caused to divide abnormally so that multinucleate cells
result. The contents of the cells are often modified;
acids may be increased or diminished; the tannin content
may increase remarkably in some cases as also that of
various coloring matters or of various enzymes.

196. These changes are in some cases the results of
causes not as yet recognizable. Such troubles are spoken
of as ''Physiological Diseases," this being simply a name
to cloak our ignorance of the true cause of the trouble.
In many cases, however, the changes occur as a result of
the action of parasitic organisms, either plant or animal
in nature. In the case of many inj uries caused by animals
(e.g. biting insects) the injury is chiefly mechanical and is
a subject for study from the standpoint of pathology in
just the same way as the study of wounds caused by other
agencies. But the punctures of some insects (e.g. plant
lice, aphids) are followed by marked physiological dis-
turbances in the cells immediately or even remotely ad-
jacent to the punctures, leading to the type of disease
called stigmonose (or puncture disease) . The enormously
varied structures found in insect galls as a result of the
presence or punctures of various gall-producing insects,
if properly understood, would doubtless throw a flood of
light upon the subject of pathology and even physiology.

PATHOLOGY 135

In all these cases it is not the parasite but its effect upon
the host that should be the subject of pathological in-
vestigation by the botanist. It must be remembered
that merely to learn the name of the organism causing the
pathological change in a plant is not to study pathology.
It is the investigation of the actual physiological and
structural changes in the diseased tissues that deserves
that name.

197. By far the greater number of plant diseases
hitherto investigated are those caused by parasitic plants
(bacteria, fungi and flowering plants). As in the case of
injury by animal parasites the effects are very varied.
Thus with some parasites the injury consists of perhaps
hardly more than the withdrawal of food stuffs or water
from the tissues of the host. Usually, however, the case
is not so simple. There is almost always some mechanical
disturbance as, for example, the destruction of the middle
lamella to permit the intercellular growth of a fungus
hypha or perhaps the actual crushing of some of the cells
of the host by the roots of some of the parasitic flowering
plants. A few parasites kill the cells some distance in
advance of their progress by the secretion of poisons of
various kinds (as is the case with Sclerotinia lihertiana),
feeding then upon the more or less disorganized remains
of the dead cells. In other cases, however, the parasite
does not kill the host cells outright but sends little
branches (haustoria) into them through which the food
matters are gradually absorbed, the death of the cell
perhaps being delayed for a long period during which it is
constantly furnishing food to its parasite. Sometimes
the diseased tissues become enlarged and richly stored
with food (various fungus galls, e.g. peach leaf curl due to
Exoasciis dejormans) which may then be used by the
fungus.

136 PLANT PHYSIOLOGY

198. Death of the diseased phiiit or tissues may be very
early or may actually be postponed beyond the normal
time, the fungus continuin<^ to live in the living infected
tissues after the surrounding tissues are dead. In most
cases, however, the presence of the parasite so weakens
the host that part of it or even the whole plant dies. The
death may result from various causes. Thus a disease
involving the tissues of the roots may so interfere with the
al)sorption of water that the top of the pLant dies under
symptoms of wilting. It is sometimes hard to tell,
however, whether the wilting is really due to reduced
water supply from the roots or to poisons secreted by or
whose secretion is induced by the fungus so that the cells
of the top are poisoned and lose their turgor, i.e. wilt.
Or again, the leaf tissues may be so destroyed by the in-
vasion of a fungus that photosynthesis is not sufficient
and the plant is weakened and dies. In some cases the
mechanical rupture of the host tissues by the reproduc-
tive bodies of the parasites leads to the destructive loss of
water through the wounds thus formed. This is probably
why the black stem rust of grains {Pucdnia graminis) is
so destructive.

199. External meteorological conditions often result in
harmful conditions in the plant. Thus low temperature,
even when the freezing point is not approached, may so
check certain functions that a plant remains dwarfed or
pale (as in Indian corn in a cold spring). Excessive heat
and atmospheric dr3'ness ma}" cause so much water loss
that the plant actually' dries out and dies. But aside
from these cases must ])e noted the diseased conditions
resulting from harmful substances in the air. Thus in
the vicinity of manufacturing cities some trees cannot
exist, owing to the sulphur dioxide given out in the smoke
and which gradually poisons some of the nutritive cells

PATHOLOGY 137

of tlie leaves. Some of the eon.stitueiits of illumiiuLtin^
gases in the air or in the soil are frequent sources of injury
and death of plants.

200. The question of the relative susceptibility of
plants to attack by parasites is also comprehended in the
term pathology. As yet it is not clear whj^ certain phmts
are nearly immune and other plants of the same species
are very susceptible to a certain disease. Apparently the
difTerence is due parth^ to differences in structure and
partly (perhaps chiefiy) to slight differences in the chem-
ical composition of the protoplasm or cell sap. The
question of induced immunit}^ the effect of changed
external conditions upon susceptibility to injury, etc.,
are very important fields of study that are as yet almost
uninvaded.

201. The study of a plant disease would require then
that the student determine the answers to the following
questions, and perhaps others as well: (1) What are the
pathological symptoms, both structural and plwsiological ?
(2) Is the disease caused by a parasite? (3) If not caused
b}^ a parasite, what is the cause? (4) If caused by a
parasite, what is its life history, particular attention being
given to the time and mode of entry into the host, method
of propagation, over-wintering, etc.? (5) What are the
external conditions, meteorological or cultural, that favor
or check the spread of the disease? (6) What differences
in susceptibility to the disease are found in different indi-
viduals or strains of the host? (7) What is the history of
the disease, its distribution, loss caused by it, etc.? (8)
In view of the foregoing, how can the disease best be
controlled?

Laboratory Studies. It is iiiipossil)le for a student in this
stage of training to undertake laboratory or field studies of any
plant diseases. It may not be amiss, however, to have him

138 PLANT PHYSIOLOGY

collect and examine as many different types of plant diseases
as he can find, for the mere ability to recognize diseased condi-
tions is of great value.

REFERENCE BOOKS

C. R. Barnes, Physiology (in Text-book of Botany by Coulter,

Barnes & Cowles), Chicago, 1910.
L, JosT, Lectures on Plant Physiology (Engl. Ed., Oxford, 1909).
W. Pfeffer, The Physiology of Plants (Engl. Ed., Oxford, 1900-

1906).
B. M. DuGGAR, Plant Physiology, 1911, New York.
R. J. Pool , Suggestions for Experiments in Plant Physiology,

19 U, Lincoln.
For the chemical aspects of this chapter and especially for the

following chapter the following books are useful.
Haas and Hill, Introduction to the chemistry of Plant Products

1913, New York.
F. CzAPEK, Biochemie der Pflanzen, 1913, Jena.

CHAPTER V

THE CHEMISTRY OF THE PLANT

In these paragraphs are brought together the com-
moner plant constituents and products, giving the name,
chemical formula and occurrence of each, so far as these
are known.

Substance and Formula

Water
H2O
Inorganic Acids and Salts

Sulphuric

H,S04
Nitric

HXO3
Hydrochloric

HCl

Phosphoric
H3PO4 (and

other forniy)

Occurrence

In all parts of the plant; the
chief solvent.

These acids are present almost
exclusively as the neutral or
acid salts of various metals,
especially Ca, K, Na and Mg.
They are largely absorbed by
the plant from the surround-
ing water in the forms in which
they are present in the plant,
or a shifting of the bases oc-
curs after their absorption.
Chiefly as the Ca salt in some
crystals.
As various salts in the cell sap.

Chiefly as K or Na salts in the
cell sap of plants, especially
those of salty soil, or in ma-
rine algae.

In the cell sap as Ca, Na or K
salts.

139

140

THE CHEMISTRY OF THE PLANT

Carbonic
H2CO3

Silicic (of various forms)
Si(0H)4, etc.

Organic Acids.

As CaCOs in cyst olit lis of
Ficus, and as deposits in or
upon the cell walls of many-
algae and fungi.
These are absor])ed in the K,
Na and Al salts and are some-
times deposited in undeter-
mined composition in cell
walls, e.g. diatoms, scouring
rushes (Equisetum), etc.

These occur in all parts of the
plant, either free or as esters
or as salts of metallic bases.
They are present as reserve
food, as waste products, as
substances to increase the os-
motic pressure, to increase
acidity, etc.

As free acid in stinging hairs
of nettles, in some fruits, etc.,
and sometimes as salts of
various metals.

As salts of various metals in
the cell sap. Formed as free
acid by the fermentation of
ethyl alcohol by various bac-
teria. Produced in dry distil-
lation of wood.

Butyric (normal) As esters in various Apiaceae.

C4H8O0, (CH3-CH2-CH.2-

COOH).
Isobutyric Free in fruit of St. John's

[ CHsv bread {Ceratonia siliqua) and

C4H8O2, \ >CH-COOH)in various other plants.

[ cn/

Palmitic, Stearic and Oleic (see below under /«/s).

Glycollic In unripe fruits and leaves of

C2H4O3, (CH2(OH)-COOH) the grape.

Formic

CH2O2, (HCOOH)

Acetic

C0H4O2, (CH3COOH)

ACIDS AND ALCOHOLS 141

Lactic Formed by the bacterial fer-

C^HfiOs (CH3-CH(0H) - mentation of milk sugar (lac-
COOH) tose), also by bacterial fer-

mentation in sauer kraut and
ensilage.
Oxalic Free or as acid or neutral salts

C2H..04(COOH-COOH) of Ca, K or Na in Oxalis,

Rumex, Rheum, etc. Very
abundant as Ca salt in the
form of crystals.
Succinic In green grapes, and in

C4H6O4 (COOH — CH2 — CH2 various Papaveraceae and As-
-COOH) terales.

Dextro-tartaric Free and as acid salt of K in

C4H606(COOH-CH(OH)- fruit of grapes and in other
CH(OH)-COOH) fruits.

Malic Very widely distributed as

C4H6O5 (COOH-CH2-CH- free acid in fruits, e.g. apple,
(OH)— COOH) barberry, grape; in leaves of

Crassulaceae, etc.
Citric Free in fruits of Citrus

C6H807(CH..(COOH)-C- (orange, lemon, etc.), goose-
(0H)(C00H)-CH2(C00H)) berry, etc.
Benzoic In fruit of cranberry and in

CtHoO. (C6H5(C00H)) various gums.

Salicylic In flowers of Ulmaria and as

CtHsOs (C6H4(0H)(C00H)) an ester in Wintergreen.
Gallic In insect galls, tea, etc.

C7H6O5 (Cr,H.(0H)3(C00H))
Gallotannic (tannin) In great abundance in many

C14H10O9 (= two molecules of i)lants; the chief tanning sub-
gallic acid united, less H2O) stance.
Alcohols.

Methvl As an ester in some fruits;

CH4O (CH3(0H)) i)roduced by dry distillation of

wood.
Ethyl Produced in the anaerobic

C2H6O (CHa -CH.,(OII)) stage of respiration of glucose.

The chief product (together
with CO2) of fermentation of
glucose by yeasts.

142

THE CHEMISTRY OF THE PLANT

Higher Alcohols.

These are grouped under the
name "fusel oil" and are pro-
duced in small quantities dur-
ing the fermentation processes
that lead to the production of
ethyl alcohol. The commonest
are the following.

Normal propyl

CsHsO, (CH3-CH2-CH2-

(OH))
Normal butyl

C4H10O, (CH3-CH2-CH2

CH2(0H))
Isobutyl f CH3\

C4H10O, i

[ CH3'

Isobutyl carbinol

[ CH,

C6H12O, \

[CHa/
Glycerine

C3H8O3, (CHo(OH)-CH-

(0H)-CH2(0H))
Mannite

CeHuOe, (CH2(0H)-CH-

(OH) -CH(OH) -CH(OH)

-CH(0H)-CH20H)
Dulcite (formula as for man-
nite).
Sorbite (formula as for mannite)
Perseite

CyHieOy, (CH2(0H) - (CH-

(OH))5-CH2(OH))
Fats and Fatty Oils.

>CH-CH2(0H))

Also found
mile oil.
>CH-CH2-CH2(OH))

in Roman camo-

See under /a/s, below.

In leaves of hlac and celery,

in sugar cane, especially in the

manna ash {Fraxinus ornus)

and in many fungi.

In Euonymus, Melampyrum,

etc.

In service berries.

In seeds of the avocado,

{Per sea gratissima) .

These are distinguished read-
ily from the so-called ethereal
or aromatic oils in that the
former leave grease spots on
paper while the spots formed
by the latter disappear on
evaporation. The chief fats
and fatty oils are esters of the

FATS AND OILS

143

Fats and Fatty Oils. — Con.

Palmitic acid

Cl6H3202,(Cl5H31-COOH)

Stearic acid

C18H36O2, (C17H35-COOH)
Oleic acid

Ci8H3402,(Ci7H33-COOH)

Ricinoleic acid

C18H34O3
Linoleic acid

C18H32O2
Crotonic acids

C4H6O2

Aromatic Oils and Camphors.

alcohol glycerine and various
fatty acids. They are mostly
liquid (i.e. oils) in plants but
in some tropical plants are
solid at ordinary temperatures.
Usually they are mixtures of
several fats, the three most
common ones being the same
as the commonest animal fats,
viz.: the first three named
below. Upon the propor-
tions of the three depends
whether the fat will be solid or
Hquid. The acids concerned
are:

Forming with glycerine a
solid fat, palmitin.
Forming with glycerine a
solid fat, stearin.
Forming with glycerine a
liquid oil, olein.
Forming with glycerine a
liquid oil (castor oil).
Forming with glycerine a
liquid oil (in linseed oil).
Of which several isomeres are
known, are found in their glyc-
erine esters in croton oil.
These are oily hquids or crys-
talline solids, mostly "ben-
zene derivatives," occurring
in fruits, leaves and stems of
many plants. The oily spots
made by the oils disappear on
evaporation. Very many are
known but in many cases the
composition is not satisfac-
torily worked out. Chemically
they are verj^ variable. Those
mentioned below arc all very
closely related to each other.

144

THE CHEMISTRY OF THE PLANT

Pineiic

C10H16
d-Limonene
CioHie

Cineol (Eucalvi)tol)

CioH.sO
Liiialool

CioHisO
Citral

CioHieO
Tanacetone

CioHieO
Camphor

CioHieO
Menthol

CioHjoO
Caoutchouc

(CioHi6)n

Gutta Percha

(CioHi60)n

Carbohydrates.

Chief constituent of turpen-
tine.

The chief oil of the orange
rind, also of oil of dill, oil of
erigeron. Together with pi-
nene it forms oil of citron.
In oil of luicalyptus.

In oils of lavender and gera-
nium.
In oil of bergamot.

In oil of tans}'.

In all parts of the camphor
tree.

Chief constituent of oil of
peppermint.

Produced in the latex of many
plants, especially Apocynaceae
and Euphorbiaceae.
In the latex of Isonamha
gutta and many other Sapo-
taceae.

The compounds grouped
under this head are in their
nature in some cases alde-
hydes, in others ketones. They
may be combined into more
complex anhydrides or ethe-
real derivatives. They con-
sist of carbon, hydrogen and
oxygen in the proportion
CxH2yOy in which x and y
may be equal, or y may be one
or more less than x (e.g.
CeHi.Oe, C12H22O11, etc.).
Mostly x = 6 or a multiple of
G. The forms with low value
for X (5 or 6 or 12) are soluble
in water and sweet to the

CARBOHYDRATES

145

Carbohydrates. — Con.

Monosaccharids.

Arabinose

C5H10O5, (CH2(0H)-(CH-

(0H))3-CH0)
d-Glucose (grape sugar, dex-
trose)

CeHioOe, (CH2(0H)-(CH-

(0H))4-CH0)

d-Galactose (formula as for glu-
cose)

d-AIaniiose (formula as for glu-
cose)

d- Fructose (fruit sugar or levu-
lose)
CfiHioO,;, (CH,(0P^)-(CH-
(0H))3-C0-CHo(0H))
10

taste and dialyze easil}'. The
solubility and sweetness as
well as i)ower to dialyze
decrease as the numl^er of car-
bon atoms increases. Those
with Ce (or C5) are called
monosaccharids; with C12, di-
saccharids or bioses; Cis, tri-
saccharids or trioses; C24,
tetrasaccharids or tetroses;
those with larger value of car-
bon are often termed poly-
saccharids. They usually have
the formula (C6Hio05)n.
Only the commoner forms
will be mentioned.
Obtained by treatment of
various gums with dilute
boiling H2SO4.

This is the commonest sugar.
It is in most cases the first car-
bohydrate produced in pho-
tosynthesis. It occurs alDun-
dantly in most sweet fruits.
It is the form in which carbo-
hydrates are translocated.
Produced b}^ the splitting of
the lactose, raffinose, or man-
neotetrose molecule by weak
acids, therefore one of the
constituents of these sugars.
Produced by the splitting of
the molecule of certain (re-
serve) celluloses by weak acida
and therefore one of the con-
stituents of those carbohy-
drates.

This sugar is abundant in
many sweet fruits, e.g. graj)e.

146

THE CHEMISTRY OF THE PLANT

Sorbinose (formula

d-fructosc)
Disaccharids.

Saccharose (Cane sugar)
d-glucose -f d-f ructose

Trehalose (Fungus sugar)
d-glucose + d-glucose

Maltose (Malt sugar)
d-glucose + d-glucose

Lactose (Milk sugar)
d-glucose + d-galactose

Trisaccharids.

Raffinose

d-f ructose + d-galactose + d-

fructose
Tetrasaccharids.

Manneotetrose

C24H44O22, d-f ructose H-d-
glucose + d-galactose + d-
galactose.

as for In juice of the fruit of the
service-berr}'.

These are to be looked upon as
formed by the union of two
(not necessarily similar) mole-
cules of monosaccharids with
the loss of H2O. Their arbi-
trary formula is C12H22O11.
The exact arrangement of the
groups within the molecule is
still disputed, so that no at-
tempt will be made to show
it. The component monosac-
charids are given in each case.
Very abundant in the higher
groups of plants in stems,
roots and fruits. Found in
sugar beet, sugar cane, Indian
corn, maple, birch, and various
palms, etc.
Abundant in fungi.

In germinating starchy seeds.

Common in milk but only
rarel}' in plants.
These have the arbitrary for-
mula C18H32O16 and are looked
upon as composed of three
monosaccharid molecules
joined with the loss of 2H2O.
Occurs in the sugar beet
(abundant in beet molasses),
cotton seeds, etc.
These are formed by the
union of four monosaccharids
with loss of water.
In gum of the Manna ash
(^Fraxinus ornus).

CARBOHYDRATES

147

Polysaccharids.

Starch (Amylum).

Glycogen (Liver starch)

InuHii

Celluloses

The following carbohydrates
have an arbitrary formula
corresponding nearly if not
exactly to (CeHioOs),. in
which n may be different for
the different forms. They
are looked upon as composed
of n molecules of monosac-
charids with loss of some
H2O. They are mostly little if
at all soluble in water and are
correspondingly lacking in
sweetness. They are the com-
monest forms of reserve car-
bohydrates.

Hydrolyzes ultimately to d-
glucose. The commonest form
of reserve carbohydrate for
green plants. Always pro-
duced in plastids (chloroplasts
or leucoplasts). Usually
formed in grains of alternating
denser and less dense concen-
tric la3^ers. Occurs in many
modifications (i.e. there are
many starches).
Hydrolyzes to d-glucose.
Very abundant in fungi. Is
the storage carbohydrate of
animals also.

Hydrolyzes to d-g 1 u c o s e.
Stored in solution in roots and
tubers of Asterales (e.g. Dah-
lia).

These are water-insoluble
compounds which form the cell
walls of most plants. Many
forms have been distin-
guished, differing in their solu-
bility in weak acids and

1-18

THE CHEMISTRY OF THE PLANT

Glucosides.

Amygdalin
C20H27NO11

Solanin
C28H47NOU

Saponin

C32H52O17
Coniferin

CifiHo^Os

alkalies and in the form of
monosaccharids produced on
hydrolysis. We can distin-
guish the celluloses proper (in-
soluble in weak acids and
alkalies, but soluble in am-
moniacal copper oxide solution
and hydrolyzing with diffi-
culty) and the hemi-celluloses
(reserve celluloses are of this
type), pectoses, etc., with all
gradations to the plant gums
which are pectic in nature and
soluble in water.
These are compounds of glu-
cose with various other, often
not. closely related, substances
from which the glucose is set
free by the action of enzymes
or acids. The most important
are:

This occurs in the leaves, bark
and kernels of peach, bitter al-
mond, cherry, etc. Under the
influence of the enzyme emul-
sin it breaks up into d-glu-
cose, oil of bitter almonds
(CeHs-CHO) and hydrocy-
anic acid (HCN).
In green portions and seeds of
the potato and other Solana-
ceae.

In soap bark (Sapindus) and
many other plants.
In young wood of Conifers
(see below under hadromal for
discussion).

GLUCOSIDES AND ALKALOIDS

149

Hesperidin

CooH^fiOi,
Aesculin

C15H16O9
Arbutin

C12H16O7
Salicin

CuHigOr
Alkaloids.

Caffeine (Theine)
C8H10N4O2

Theobromine

Piperin

CiyHiglSOa

Abrotanin
C21H00X2O

Aconitin
C33H45NO12

In green oranges.

In bark of horse chestnut

(Aescukis).

In leaves of bear})erry (Arcto-

staphylos) .

In the willow.

These are organic compounds,
acting as bases in the presence
of acids, and usually bitter to
the taste. Under this name
are grouped a variety of un-
related substances although
the tendency now is to limit
the name to derivatives of the
pyridin group which would
exclude the first two in the list
below of the commoner alka-
loids. Many if not most
alkaloids are poisonous. They
may be in some cases reserve
foods but possibly in other
cases are waste products or
even special defences against
herbivorous animals.
In leaves of tea, "berries" of
coffee and in many other
plants (e.g. Cola nut).
In seeds of the cacao.

In pepper {Piper nigrum).

In wormwood (Artemisia

ahrotanum).

In monkshood (Aconitum).

150

THE CHEMISTRY OF THE PLANT

Atropine

C17H23NO3
Berberin

C20H17NO4
Brucine

C23H26N:!04

Cocaine

C17H21NO4
Coniine

CsHnN

Cytisin
C11H14N2O

Hydrochinin
C20H26N2O2

Hyoscyamine
C17H23NO3

Lupinin
C10H19NO

Morphine

CiyHiglsOa

Nicotine

C10H14N2
Quinine

C20H30N 2O2
Strychnine

G21H22N 2O2
Taxin

C37H52NO10

Veratrine

C22H42NO9
Protein Group.

In leaves of Atropa bella-
donna.

In Berberidaceae, Ranuncu-
laceae, Papaveraceae, etc.
In the seeds of nux vomica
{Strychnos nux-vomica. )
In leaves of coca (Erythrox-
ylon coca) .

The poisonous principle of the
hemlock {Coniiim macula-
turn).

In various Fabaceae, e.g.
Cytisus, Laburnum, Sophora,
Thermopsis, Baptisia, Ulex,
etc.
In Cinchona bark.

I n henbane {Hyoscyamus

niger).

In seeds of various lupines.

The chief of many alkaloids
in opium, the coagulated latex
of Papaver somniferum.
In tobacco.

In the bark of Cinchona.

In the seeds of nux vomica

{Strychnos nux-vomica).

In twigs, leaves and fruit of

the European yew {Taxu^

baccata) .

In Veratrum album.

This embraces a vast number
of very complex compounds

PROTEINS 151

Protein Grouv. — Con, whose true composition is in

great part not yet clear. They
contain C, H, and N in
fairly large amounts and usu-
ally some S and often P. They
may also have in combination
certain metallic bases, but
this is not proved. They are
probably built up of combined
chains of amino-acids. Pos-
sibly hydrocyanic acid is one
of the steps, for it is abundant
in many plants when protein-
synthesis is active. Possibly
carbohydrates also are of
importance in the framework
of the molecule. The molecule
is very large and in the more
complex forms dialysis does
not occur or oi\\y feebly, but
in forms like peptones it
readily takes place. The high-
er forms lead to the Proto-
plasms which are chemically
to be regarded as very com-
plex protein compounds in
which probabl}' various metal-
lic bases are combined and
which perhaps have one or
more carbohydrate nuclei in
the molecule. They are very
labile compounds, easily de-
stroyed by external influences
of varied nature. The proto-
plasm and higher protein
compounds {Albinucns) are
usually easily coagulable by
heat and by"^salts of Cu, Hg,
Ag, etc. By hydrolysis with
certain enzymes these com-
pounds are broken down into

152

THK CHEMISTRY OF THE PLANT

Protein Group. — Con.

Enzymes.

Invertase
Cytase

the less complex, soluble, di-
alyzable Albumoses (to which
the peptones belong). Other
related groups are the Albu-
minoidSf some of which are
crystallizablc. All of these
groups have innumerable
forms differing from one
another in solubility in acids,
alkaUes and salt solutions; in
their coagulabihty with heat,
salts, acids and alkalies and
enzymes; in their power to
dialyze, and in the forms of
enzymes that can attack them
and the forms of the pro-
ducts of such enzymatic
action.

These are substances showing
many of the characteristics of
the protein compounds (e.g.
destruction of activity by heat
or salts of heavy metals, etc.),
but not so complex. They are
very numerous, even in the
same plant, and perform many
of its important functions.
They are in a sense ''cataly-
zers," in that they start or
intensify chemical processes
without themselves being used
up (or only in relatively small
degree) .

The more important plant en-
zymes and the substances
acted upon by them are as
follows :

Hydrolyzing saccharose to d-
glucose and d-fructose.
Hydrolyzing hemicelluloses to
• monosaccharids.

ENZYMES

l-)3

Pectase

Amylase (diastase)

Zymase
Emulsin

Lipase

Pepsins and trypsines

Oxidases and peroxidases

Catalase

Reductase

Miscellaneous substances.

Methane

CH4
Heptane

C7H16
Methylamine

CHsX, (CH3NH2)
Tri-methjdaminc

C3H9N, (CH3)3X)

Formaldehyde
CH20,(H-CH0)

Ilydrolyzinjs; pectin com-
pounds to monosaccharids.
Hydrolyzing starch to d-glu-
cose (probably several steps,
involving perhaps several
enzymes).

Sphtting d-glucose into ethyl
alcohol and CO2.
Hydrolyzing amygdalin to
HCN, d-glucose and oil of
bitter almonds.
Acting on fats, saponifying
and emulsifjang them.
Hydrolyzing protein com-
pounds to different degrees of
simplicity.

IMany kinds, bringing about
numerous oxidations within
the plant.

Decomposing peroxides in the
plant.

Bringing about reducing proc-
esses in the plant.
Under this head are grouped a
number of totall}^ unrelated
substances that do not come
under anj^ of the foregoing
heads and that are not numer-
ous enough to form classes by
themselves.

Produced by bacterial fermen-
tations of celluloses.
In the oil from the seeds of
some pines.

In Mercitrialis pcrcnuis and
M. annua.

In Chenopodium, in blossoms
of Crataegus, and of pear, etc.
Apparently one of the first
steps in the photosynthesis of
CO2 and HO2 to form carbo-

154

THE CHEMISTRY OF THE PLANT

Formaldehyde — C

Asparagin

C4H8N0O3, (CO(XHo) - CH2
-CH(XHo)-COOH).

Chit in
CisH

iNoOi

hydrates. Found free in
minute quantities in leaves
when active photosynthesis is
occurring.

This is found, especially in the
growing regions, in many
plants, e.g. asparagus, peas,
beans, vetches, beet roots,
potatoes, etc.

This forms part of, or in some
cases is the chief constituent of,
the cell wall of many of the
lower plants, e.g. Myxo-
phyceae, Mucorales, Carpo-
myceteae. It was long con-
sidered a form of cellulose
("fungus cellulose")- It
forms the body waU of insects,
crustaceans, etc.
Formed by the fermentation
of the seed pods (''beans") of
the Vanilla plant, whence it is
extracted by alcohol. It is
present in most if not all
lignified cell walls and is
possibly one of the substances
giving the cell wall the char-
acters that we call "lignifica-
tion" (see hadromal).
Hadromal (composition uncer- This is a substance separated
tain) by Czapek from hgnified cell

walls and believed by him to
be what gives them their
"Hgnified" character. On the
other hand many botanists do
not consider this as the impor-
tant body and ascribe hgnifi ca-
tion to the presence in the cell
walls of conifcrin and vanilhn
(q.v.) and perhaps other sub-
stances.

Vanillin
CsHsOa

PIGMENTS

155

Suberiu

Cutin

Chlorophyll (chlorophyllan)

Carotin (Xanthophyll)
C26H38

This is the name appHed to
what is proi)ably a mixture of
several fatty acids including
the following: Phellonic, phloe-
onic and suberic (CgH^Os).
Their presence in the cell walls
waterproofs them.
This is a fatty substance or
substances related to the fore-
going and waterproofing the
epidermal cell walls in which
it is deposited.

This is a blue-green pigment
occurring only in chloroplasts
(or in such Myxophyceae as
lack definite chloroplasts in
minute particles in the cyto-
plasm). It is the most im-
portant plant pigment, ab-
sorbing certain light rays and
transforming the energy into
the chemical energy used in
photosynthesis. It is formed
(with rare exceptions) only in
the light and is itself quickly
destroyed by bright fight. It
contains no iron but the plant
requires iron for its produc-
tion. Its chemical composi-
tion is not exactly known but
it seems to be closely related
to haemoglobin. It is insoluble
in water but soluble in alcohol,
ether, petroleum ether, gaso-
line, etc. Probably "chloro-
j)hyir' is not one but a group
of closely similar compounds.
Under the name Xanthoi)hyll
this substance is associated in
small or ,largc proj)ortions
with chlo5i)hyll wlierrever the
latter occurs, the mixture giv-

156

THE CHEMISTRY OF THE PLANT

ing the characteristic ''grass
green" color to the chloro-
plasts. It is present without
chloroph}^! in autumn leaves
and in many parts of some
plants. The autumn colora-
tion of leaves is due to various
chemical changes of carotin
and chlorophyll and other sub-
stances present in the cells.
Carotin is of itself yellow to
orange when in solution, form-
ing orange-red to red crystals.
It is insoluble in water, petrol-
eum ether and gasohne, but
soluble in alcohol, ether, etc.
Other plant pigments, of un-
known composition, may be
associated w4th the two pre-
ceding pigments, giving char-
atceristic colors to the chloro-
plasts. Their function is not
proved, but in some cases they
probably change the quality of
light to that most favorable for
absorption by the chlorophyll.

Phycocyanin In the Myxophyceae, blue,

water soluble.

Phycophaein In the Phaeophyceae, brown.

Diatomin In Bacillarioideae (diatoms)

brown, water soluble.

Phycoerythrin In Rhodophyceae and a few

Siphonophyceae, violet-red,
water soluble.

Anthocyanin is a red (in acid cell sap) or blue (in alkaline cell

sap) coloring matter in the
cell sap of many brightly
colored leaves and other plant
parts, occurring especially in
the epidermal cells. It is ap-
parently a nitrogen-free glu-
coside.

CHAPTER VI
THE CLASSIFICATION OF PLANTS

202. We now come to that part of the subject in which
we are to consider the different kinds of plants to be
found in the world. Botanists now know over 233,000
kinds, a number which is too vast to be remembered in
detail by any one and yet even the beginner may learn
much about them by taking up their study properly.

Of Relationship

203. It is now known that all the kinds of plants are
related to one another. By this we mean that traced
back far enough all plants have a common ancestry, in
other words they have descended from earlier identical
or similar forms. This is what we know as Evolution,
and in thinking of the great numbers of plants we regard
them as related to one another because they have
descended recenth' or remotely from common ancestors.

204. In Botany we try to group plants according to
their relationships, much as we group people by their
relationships. This requires that as we study plants we
should constantly keep in mind the fact that they are
less or more alike just as their relationship is remoter or
nearer. And this is what we call Phylogeny, that is, the
racial history of the groups of plants. So what follows
in Chapters VII to XX is an attempt to present selected
representatives of the groups of plants in such a sequence
as will suggest their relationship and path of development.

205. It must be remembered that plants have been in
existence for a very long time, and that many, or possi-

157

158 THE CLASSIFICATION OF PLANTS

bly all of the earliest kinds have disappeared. If we
had before us all of the plants that ever existed the task
of arranging them so as to show their relationship would
still be a difficult one, but with many forms irretrievably
lost the difficulty of the task is very greatly increased.
Some lower plants are probably still much like their
primitive ancestors, while others have been greatly
modified. We may think of the plants that we now see
as having developed through shorter or longer distances;
some perhaps have stood still in their original places,
others have moved forward short distances to where we
now find them, while still others have gone much farther
along their evolutionary pathway to their present
positions.

Of Species and Genera

206. In studying plants we notice that they exist as
kinds, and there has been a general agreement to speak of
each recognizable kind as a "species." Thus we speak
of the species of Oaks, Elms, Ashes, Magnolias, etc.,
meaning the kinds of Oaks (White Oak, Red Oak, Black
Oak, etc.), or Elms (White Elm, Sfippery Elm, Cork Elm,
etc.), or Ash (White Ash, Green Ash, Black Ash, etc.),
etc., etc., and in all these cases we recognize that we refer
to a quite definite kind — a species. While in many cases
the distinctions are less definite, it is still true that in any
particular locality plants are recognizable as kinds
(species). Now these species are sufficiently stable so
that under constant conditions, in any particular locality
they change slowly, if at all, while they are sufficiently
plastic so that under changed conditions, as when they
are carried to other habitats, they change more or less,
and this may be great enough so that we regard them as
different species.

HIGHER GROUPS 159

207. For our own convenience we group similar species
into genera. Thus we group all the species of oaks into
one genus Quercus, the old Latin name for all the Oaks,
and in like manner all the Elms are grouped under U Imus,
the Latin name for the Elms. So we have Quercus alba,
Quercus rubra, Quercus nigra, etc., and Ulmus americana,
Uhnus fulva, Ulmus racemosa, etc., in all of which cases
the first name is that of the genus, and the second that of
the species and these constitute the names of these plants.
The name of the plant comes thus from its classification.

Higher Groups

208. For further convenience all genera are gathered
into their appropriate families, all famihes into orders, all
orders into classes, and finally all classes into phyla.
Lastly all the kinds of plants in the world are said to con-
stitute the Vegetable Kingdom.

We may arrange these as follows:
Species consist of individual plants
Genera are composed of species
Families are collections of genera
Orders are collections of families
Classes are collections of orders
Phyla are collections of classes

The vegetable kingdom is a collection
of phyla.
From this it follows that:

Every plant belongs to some species
Every species to some genus
Every genus to some family
Every family to some order
Every order to some class
Every class to some phylum

All phyla to the Vegetal)lc Kingdom.

160 THE CLASSIFICATION OF PLANTS

So the Vegetable Kingdom contains
Phyla

Classes (also Sub-classes)

Orders (also Super-orders, and Sub-orders)
Families (also Sub-families)
Genera
Species.

The foregoing may be called the framework of the
classification of plants used in this book.

209, It must be borne in mind that in this classification
we are dealing with individuals as the only actually ex-
istent things. For our own convenience we form a
mental concept of an aggregation of similar individuals,
and this we hold as "kind" ('' species")- So also we
form a mental picture of an aggregation of similar species,
and this is what we call the genus. Quite similarly we
form a concept of aggregated genera, and call it a family,
and so on for orders, classes and phyla.

Evolution

210. For the present purpose the more important
points included in the general doctrine of evolution may
be summarily stated as follows:

1. The first species were lower plants, and these gave
rise to higher plants.

2. Evolution while generally upward (progressive) is
often downward (retrogressive).

3. Evolution does not necessarily involve all organs of
the plant equally in any particular period, and one organ
may be progressing at the same time that another is
retrograding.

4. Hysterophytic retrogression of plants is persistent,
and the hysterophytic phylum does not afterward be-
come holophytic.

EVOLUTION 101

5. All plant relationships are genetic, and these rela-
tionships are up and doini the genetic Hnes.

Origin of Phyla

211. If now we inquire as to the origin of phyla we may
formulate our answer in several ways. Stated philo-
sophically we may say that a phylum originates with
the incoming of a new idea. Stated structurally, it has
its beginning with the development of a dominant mor-
phological peculiarity. Stated taxonomically, its initial
point is indicated bj^ the appearance of a new character.
So every phylum is the result of a development which
differs from that which preceded it because of the incom-
ing of a new idea: this dominant idea was manifestetl
structurally by a divergence from the previous lines of
evolution and this point of divergence became the actual
origin of the new phylum. As long as this idea and its
structural expression dominate, so long does the phylum
extend, and when a still newer idea comes in and attains
dominance, a still newer phylum has its beginning. So
we say that a phylum originates with a divergence which
is the expression of a new idea, or in other words a ''tend-
ency"; and this in taxonomy we call a ''new character."

The Place of Plants in Time

212. As stated a])ove, plants have been in existence a
ver}' long time, and as some references will be made in the
following chapters to particular periods of time it is
necessary here to give a table showing the divisions of
earth time (''geologic time") as recognized in recent
treatises, with suggestions as to their vegetation. In this
table no attempt is made to indicate the relative lengths
of different periods.

162

THE CLASSIFICATION OF PLANTS

General Table of Geologic Time Divisions

Cexozoic
(Tertiary)

Mesozoic ,

Paleozoic,

Proterozoic.
Archeozoic.

Present — All i^hyla including highest Flow-
ering Plants.

Pleistocene — Nearly as at present.

Pliocene 1

Miocene [ Increase in higher Flowering

Oligocene J Plants.

Eocene — Increase of Flowering Plants.

Upper Cretaceous — Rapid increase of lower
Flowering Plants.

Lower Cretaceous (Comanche or Shastan) —
Appearance of lower Flowering Plants.

Jurassic — Ferns, Cycads, Conife^^.

Triassic — Ferns, Cycads, Conifers.

Permian — Ferns, Calamites, Lycopods, Cy-
cads, Conifers.

Coal Measures, or Pennsylvanian — Ferns,
Calamites, Lycopods, Cycads.

Subcarboniferous, or Mississippian — Ferns,
Calamites, Lycopods, Cy'cads.

Devonian — Ferns, Calamites, Lycopods, Cy-
cads.

Silurian — Probably some land vegetation.

Ordovician — Probabty some land vegetation.

Cambrian — Apparently some higher algae.

Keweenawan 1 Probably

Animikean (Upper Huronian) > only simple

Huronian J algae.

Archean Complex — Probably only very sim-
ple algae.

CHAPTER VII

PHYLUM I. MYXOPHYCEAE
THE SLIME ALGAE

213. The Slime Algae are the lowest and simplest
plants, and are often so minute as to require the highest
powers of the microscope for their study. Some of them
are single cells, while others are rows or masses of similar
or slightly different cells. In most Slime Algae the cells
are poorly developed, the walls being soft and easily
gelatinized and usually containing chitin, the nuclear
matter diffused and not bounded by a nuclear membrane,
and the cytoplasm containing no plastids.

214. The dominant coloring matter of the cells, phiy-
cocyanin, which is blue, is mostly distributed through-
out the protoplasm, and mixed with the chlorophyll and
more or less carotin give the blue-green, brown-green,
or smok}^ color found in this group. In the hystero-
phytes these are wanting.

215. They reproduce asexually by fission,
and the formation of spores, and in the fila-
mentous forms by the breaking of the filaments
into short segments (hormogones) each of fig. 59.
which then grows into a long filament. No theMyxo-
sexual reproduction is known. ^ ^^*^^^"

216. The Slime Algae mostly live in the water, getting
their nourishment from the solutions it contains. The
green plants (holophytes) are able to use carbon dioxide,
but those not green (hysterophytes) are typically par-
asitic or saprophytic.

163

164 PHYLUiM I. MYXOPHYCEAE

217. In this Pln^lum the dominant idea is the simple
nucleus, typically not limited by a nuclear membrane,
asexual reproduction, and blue-green color.

There are two classes:

I. Nucleus not definitely outlined, no nuclear membrane; no
plastids. Class 1. Archiplastideae.

II. Nucleus definitely outlined, with a nuclear membrane;
plastids present. Class 2. Holoplastideae.

Class 1. ARCHIPLASTIDEAE (CYANOPHYCEAE)
The Blue Greens

218. In these plants (numbering about 2000 species)
there is no limiting membrane around the primitive
nucleus, and yet there is a simple karyokinetic process
in cell division. In the absence of plastids the coloring
matter is diffused throughout the cell.

ORDER COCCOGONALES. Unicellular Blue Greens

219. Here the plants are strictly unicellular, although
they may be aggregated into colonies in which the cells
are included in a gelatinous matrix due to the softeuing
of their walls.

220. These are the lowest and simplest of plants; they
<-s /TN live as single cells in the water, or they may
©Q ^ ^^6 aggregated into slimy films on sticks

§and stones. The principal family is Chro-
ococcaceae, represented by minute species
Fig. go — of Chroococcus, Gloeocapsa, Aphanocapsa,
chrooV^)?Jurand Mcrismopcdia and other genera. Each cell
Gloeocapsa. dividcs iuto two, and these soon divide

again, and so on. In Merismopedia the successive
divisions are in two planes, resulting in quadrate
colonies of regularly arranged cells.

FILAMENTOUS BLUE GREENS Kio

ORDER HORMOGONALES. Filamentous Blue Greens

221. These plants consist of simple or branched rows
(filaments) of cells, which are usually enclosed in a
sheath. There are half a dozen families, the lowest of
which is Oscillator iaceae, with cylindrical filaments of
uniform cells. There are many genera, as Microcolcus,
L3'ngb3"a, Spirulina, Oscillatoria, etc., which occur in
quiet waters. Oscillatoria and Spirulina are interesting
because of their marked motility.

222. The Nostocs (Family Nostocaceae) are filamen-
tous with more or less spherical cells, some of which
are larger (rarely smaller) than the others and have
thickened, cellulose walls (heterocysts). Spores are
common as larger, denser cells which serve to carry the
species through adverse conditions. The genera Nostoc,
Anabaena, and Cyhndrospermum are common.

^m^^^^nnlt.Hltf]^

Fig. 61. — Oscilla- Fig. 62. — Scytonema and

toria and Nostoc. Rivularia.

223. The Scytonemas (Family Scytonemataceae) have
cylindrical (often branched) filaments which contain
heterocysts also. Scytonema and Tolypothrix are
common genera.

224. The Rivularias (Famil}^ Rividar iaceae) are taper-
ing filaments with a heterocyst at the base. They
usually occur in jelly-like masses. The principal genus
is Rivularia.

225. The Stigonemas (Family Stigoncmataccac), while
filamentous, have their larger filaments composed of more
than one row of cells. Haplosiphon and Stigonema are
common genera.

166 PHYLUM I. MYXOPHYCEAE

ORDER BACTERIALES. The Bactkria

226. Tli(^ Bacteria, wliich are here regarded as degen-
erated chlorophyll-less Blue Greens, are so important
that they require a somewhat fuller treatment. They
are the smallest of living things, some being as small as
0.0005 millimeters (1/50,000 inch), or even smaller. Al-
though typically filamentous they break up easily into
one-celled or few-celled forms, in which condition they
are most commonly found. In some species they occur
as minute rounded cells (''cocci"), in others elongated
(then called ''rods"), and in still others they are more or
less curved. They are frequently provided with one or
more cilia or flagella by means of wdiich they are motile.

227. Bacteria are found in great numbers in the watery
parts of decaying organic matter, causing various kinds

of fermentation, and in fact they occur so
generally in Nature that their presence is
almost universal. They reproduce by fis-
sion with such astonishing rapidity that in
^^°"b!fct7r?a.' """^^^ a short time they swarm in any exposed
substance which is capable of furnishing
them with food. Some of the species live in the
watery juices of plants and animals, causing various
diseases. However, of the hundreds of species known,
the great majority are harmless, or actually beneficent.

228. Some bacteria can endure high temperatures,
especially in the spore state, and frequently appear in
tightly closed vessels whose contents have been boiled.
Some people have been led to explain their appearance
under such circumstances by ''spontaneous generation";
but thus far the facts are capable of other explanation.

229. The proper spores of bacteria (endospores) are
produced singly within the cells, and are thick-walled,
rounded bodies. By the breaking of the filaments into

HIGHER BLUE GREENS 167

their component cells other reproductive bodies (hormo-
gones) are formed.

230. On account of their minuteness, bacteria may be
picked up by currents of air and borne long distances,
and in this way they are doubtless often carried from
place to place. When a pool of putrid water dries up,
the bacteria with which it swarmed are blown away with
the dust and dirt, dropping everywhere into pools, upon
plants and animals living and dead, and even entering
our lungs with the air we breathe.

Class 2. HOLOPLASTIDEAE
The Higher Blue Greens

231. This little class, of about 20 species, includes
SHme Algae, in which the nucleus is defined by a nuclear
membrane, and the coloring matter is concentrated in
one or more plastids. There is but one order, the
Glaucocystales, and a single family (Glaucocystaceae) of
unicellular plants. The type genus is Glaucocystis.

Laboratory Studies of the Myxophyceae. With the fore-
going sciicrul statements of the structure and life of the Slime
Algae including the Bacteria, the student must now make some
examination of them by means of a good compound microscope
in the laboratory. In his examination he should make careful
drawings accompanied by brief, necessary descriptions. It is a
good rule in the study of plants never to make a needless draw-
ing, nor write an unnecessary description. A second rule of still
greater importance insists upon the absolute truthfulness (ac-
curacy) of both drawings and descriptions.

The following studies are suggested as useful.

(a) Scrape off a little of the greenish slimy matter from a
damp wall, mounting it in water; examine und.cr a liigli power.
Some small blue-green or smoky-green cells will be found
belonging to the Blue-green Slimes (Chroococcus, etc.); of

168 PHYLUIM I. IVIYXOPHYCEAE

these some will probably be found in process of fission. Larger
br'ght-green cells filled with granular protoplasm will also be
found; these are species of Protococcus belonging to the next
phylum.

(h) In midsummer look along the water-line of fresh-water
lakes and ponds for soft, amber-colored, round masses from the
s"ze of a pea to that of a hickory-nut. By mounting a small
sl'ce of one of these it will be seen under the microscope to be
composed of mj^iads of filaments of Nostoc. Occasionally a
filament may be seen with a heterocj^st; its function is not
known.

(c) Secure a handful of the dark-green filamentous growth
which is common on the wet sides of watering-troughs and
place it in a dish of water. If an Oscillatoria, it will rapidly
disperse itself, a few minutes being long enough to show quite
a change in position. Now mount a few filaments in water and
examine under a high power. They will be seen to sway from
side to side while moving quite rapidly across the field of the
m'croscope.

(d) In midsummer scrape off one of the small jelly-like
masses of Rivularia, so common on the submerged stems of
water-plants; mount in water, crushing or cutting the mass so
as to show the individual filaments. Each filament tapers
from the center of the mass outw^ard, and at its larger (inner)
end there is generally a heterocyst.

Some elementary studies of bacteria may be made very easily,
but their profound study (Bacteriology) involves a technique
which is unattainable by the beginner in Botany. The follow-
ing may be attempted.

(e) Boil a pinch of cut hay or any other similar vegetable
substance for a few moments, and put into a glass of water;
keep in a warm room for a couple of days, or until it be-
comes turbid (from the abundance of bacteria); examine a
minute drop with the highest powers of the microscope, for
active bacteria. The bacterial growth originates from the
si)ores which were not killed by the short boihng. The com-
monest form thus obtained is Bacillus subtilis.

(/) Put a bit of fresh meat into water, and study the bacteria
which will appear in it. Spiral forms (especially Spirillum)
may often be found in such a preparation.

(g) Examine the juices of decaying fruits and vegetables.

LABORATORY STUDIES 169

(It) Amons the many hacteriii of esi)ccial iiitcroHt to us are
the following:

1. Clover-nodule bacteria (Psendomonas leguminosarum) ,
which enrich the soil by the i^'oduction of nitrogen compounds.

2. Sulphur-bacteria (Bcggiatoa aiha), which occur as large
motile filaments in refrigerator drains.

3. Apple and i)ear blight bacteria {Bacillus amylovorus),
causing the blight in apple and pear trees.

4. Cucumber-wilt bacteria {Bacillus tracheiphilus) , causing
the ''wilt disease" of cucumbers, and other cucurbits.

5. Crown-gall bacteria {Pseudomonas tumcfaciens) , causing
the crown galls in the roots and stems of many plants.

6. Typhoid fever bacteria {Bacillus typhosus), causing
typhoid fever.

7. Tuberculosis bacteria {Bacterium tuberculosis), causing
tuberculosis.

8. Diphtheria bacteria {Bacterium diphtheriae), causing
diphtheria.

9. Influenza bacteria {Bacterium influenzae), causing influ-
enza (''Grippe").

10. Anthrax bacteria {Bacterium anthracis), causing anthrax.

11. Cholera bacteria {Microspira comma), causing cholera.

12. Colon bacteria {Bacillus coli) in the large intestines of
most mammals.

LITERATURE OF MYXOPHYCEAE

Here as elsewhere only the most necessary works are men-
tioned, in the order of their desirability for the beginner in
Botany.

G. S. West, A Treatise on the British Freshwater Algae,

Cambridge, 1904.
Josephine E. Tildex, The Myxophyccae of North America and

Adjacent Regions (Vol. I of Minnesota Algae), Minneapolis,

1910.
G. B. De Toni, Sylloge Algarum, Vol. 5, Padua.
E. F. Smith, Bacteria in Relation to Plant Diseases, Washington,

I, 1906; II, 1911.
W. D. Frost and E. F. Campbell, A Text-hook of General

Bacteriology, New York, 1910.

CHAPTER VIII
PHYLUM II. CHLOROPHYCEAE*

THE SIMPLE ALGAE

232. The plants of this phylum while still small, and
mostly microscopic and consisting of single cells, fila-
ments or rarely plates of cells, show a considerable ad-
vance over the Slime Algae in having well-defined nuclei,
definite plastids, a dominant yellow-green color (chlor-

ophyll and carotin), and in many genera
sexual reproduction. The cells are much
better developed, the walls are composed of
cellulose, and are usually firmer. The nu-
FiG. 64— A <^lear matter of the cell is collected into a

rophyceae^^^°' definite uuclcus which is surrounded by a
membrane. A portion of the protoplasm is

set off as one or more distinct plastids (chloroplasts)

which are stained green by chlorophyll.

233. Here the dominant idea is the definite nucleus
limited by a nuclear membrane. With this are associated
the definite plastids, true chlorophyll, firm cell wall,
motile reproductive structures (zoospores and gametes),
and the still simple plant body.

234. The Simple Algae, of which there are about 1100
species, are mainly fresh-water plants, living on wet
rocks, moist walls or tree-trunks, etc., or floating or
attached in the deeper waters. A few have become
degenerated through parasitism.

* This name is here used in the narrower sense, excluding the
plants of the phyla Zygophyceae and Siphonophyceae.

170

GREEN SLIMES 171

235. This phylum has been unusually productive of
other phyla of primary and secondary rank, and the
suggestion is hazarded that also from it (near Proto-
coccoideae) a phyletic line gave rise to the Animal King-
dom. There are two classes:

I. Plants unicellular, or in colonies.

Class 3. Protococcoideae

II. Plants pluricellular, in filaments (or plates).

Class 4. CONFERVOIDEAE

Class 3. PROTOCOCCOIDEAE. Green Slimes

236. These plants (of about 450 species) are nearly all
microscopic, and are unicellular, or in a few cases aggre-
gated into definite colonies. They propagate (reproduce
by asexual reproduction) by (1) cell division, (2) ciliated
zoospores, (3) and thick-walled spores (chlamydospores),
and generate (reproduce by sexual reproduction) by the
union of equal, motile gametes (isogametes) to form a
single cell (zygote) which often becomes a thick-walled
spore. Generation is not known for all of the species.

ORDER PALMELLALES

237. These unicellular plants are not aggregated into
colonies, although they may remain attached together
in irregular masses for some time after cell

division. They are common in water, and (o) ^2><

in moist or wet places, as the sides of walls,

trees, posts, etc., where they often form (^^ fs^p)

dense, green layers. The spherical forms ^^— ^ Ks^

growing on trees, walls, etc., which produce prol^eoccus

no zoospores are species of Protococcus,

while those with zoospores may be Chlorococcum.

Near relatives of these have become unicellular para-

172 PHYLUM II. CIILOROPHYCEAE

sites (Family Synchytriaccae) in the tissues of other algae,
or even land plants, and are known as Gall-fungi.

ORDER COENOBIALES

238. The cells or coenocytes in these plants are aggre-
gated into colonies, the most common of which are the

pretty species of Scenedesmus, in
which four spindle-shaped cells lie
side by side. Less common is the
very regular plate-colony of Pedias-
trum with usually a dozen or more
regularly arranged coenocytes. Re-
T, ^^ o , lated to these is the Water Net

riG. GG. — Scenedosmus,

dfcf'oi'"™ ''"'^ Hydro- (Hydrodictyon) with its many long
coenocytes arranged in a hollow,
reticulated colony 20 to 30 centimeters long. Ciliated
zoospores and isogametes occur in Pediastrum and
H3xlrodictyon.

239. Here are commonly placed certain doubtful
organisms, the Volvoces (Volvox, Pandorina, and related
genera), with the color of plants but the structure of
animals. Most botanists still claim them on account of
their color, but many zoologists emphasizing the impor-
tance of their structure regard them as animals (Flag-
ellata). The explanation here given is that at about
this point in the Vegetable Kingdom the animal type be-
came differentiated from the plant type by an increase
in the motility of the cells, and in the Volvoces we have
the organisms on the pathway leading from plants to
animals. In the opinion of the authors they have already
passed the frontier of the Plant Kingdom, and entered
that of Animals, although they have not yet abandoned
their use of chlorophyll.

240. On the same ground should be excluded the ''red

CONFERVAS

173

snow plant'' of high mountains and polar regions, a
unicellular ciliated organism (Chlamydomonas) which is
usually of a red color, and some more common but similar,
often red, organisms (Haematococcus) found in pools and
on wet earth. They are all more like animals than
plants.

Class 4. CONFERVOIDEAE. Confervas

241. The Confervas are simple or branched filaments of
cells, or a sheet (plate) of cells, and number about G40
species. They propagate by (1) the fracture of the
filaments (into hormogones), (2) ciliated zoospores, (3)
thick- walled spores (chlamydospores), and generate by
the union of isogametes or heterogametes, to form a
zygote which often becomes a thick-walled spore. They
are mostly fresh-water plants, in

ponds and in running waters. W^( ^

242. The simplest of the Confervas jf( '
are small unbranched filaments (spe-
cies of Ulothrix) which are usually
attached by a basal cell (''root").
They propagate by 2- or 4-ciliated
zoospores, and generate by the union
of 2-ciliate gametes.

243. The very similar, much-branched and rooted
Draparnaldia and Chaetophora present a slightly higher
development of the same type. They are common in
running fresh water.

244. Kelated to these are the Sea-Lettuces common on
stones, wharf-timbers, etc., along the coast and in brack-
ish waters, and resembling small lettuce leaves. Each
plant consists of a single layer of cells (JNIonostroma) or
two layers (Ulva), and nearly every cell is capable of

Fig. 67.— Ulothrix and
Monostroma.

174

PHYLUM II. CHLOROPHYCEAE

Fig. 68.
Oedogonium.

producing 4-ciliate zoospores, or 2-ciliate gametes. The
irregularly tubular Enteromorphas resemble the Sea
Lettuces and are oommon in brackish ponds.

245. In the Oedogoniums {Ocdogoniaceae) the plants
are attached below, and are simple or branched above.
They propagate by means of multiciliated zoospores which
are formed singly in the cells, and generate by hetero-
gametes, consisting of small multiciliated sperms, and

large non-ciliated eggs. The sperms are
formed (1) in certain cells in the filament
which produces the eggs, or (2) in some-
what smaller filaments, or (3) in very
small, few-celled filaments ("dwarf males").
The eggs are formed singly in oogones that
are merely transformed and considerably
enlarged vegetative cells. When the egg
reaches maturity the oogone wall opens to admit the
sperm, after which the egg becomes a thick-walled rest-
ing spore. In germination the resting spore divides into
four multiciliated zoospores which soon come to rest and
develop into ordinary vegetative filaments.

246. The little Disk Algae (Coleochaetaceae) are minute
branching plants closely related to the Oedogoniums,
whose radiating filaments usually fuse later-
ally into small disks or cushions, a milli-
meter or so in diameter, and occurring on
the stems and leaves of larger water plants.
They propagate by biciliated zoospores
formed singly in the cells, and generate by
heterogametes. The biciliated sperms are
formed singly in the antheridial cells.
The oogones are terminal and each contains

a single egg, and is supplied with a tubular prolongation,
the 'Hrichogyne.'^

Coleochaete.

DISK ALGAE 175

247. Fertilization is effected by a sperm uniting with
the egg in the oogone, usually by passing into the open
end of the trichogyne. After fertilization the egg in-
creases considerably in size, and forms a cellulose coat of
its own. The cells which support the oogone send out
lateral branches, which grow up and closely surround it,
finally covering it entirely (excepting the trichogyne)
with a cellular thick- walled '^pericarp. '' The whole mass,
including the fertilized oogone and its investing pericarp,
constitutes the simplest form of spore-fruit (sporocarp).

248. The further growth of the spore-fruit takes place
the next spring by the swelling of the protoplasmic con-
tents, and the consequent rupture of the pericarp; the
inner portion divides into several cells (the proper fruit-
spores), which give rise to zoospores closely resembling
those developed from the vegetative cells. From each
zoospore a new plant eventually arises.

There is but one genus (Coleochaete) including a few
widely distributed species.

Laboratory Studies, (a) Scrape off a little of the green,
paint-like coating from a flower-pot, a damp wall, or a side-
walk plank, and examine under a high power for common
Green Slime (Protococcus, etc.).

(6) Gall-fungi may sometimes be found in Spirogyra and
Desmids, and in the leaves of evening primroses, plantains,
mints, and some leguminous plants.

(c) Examine the green })lants collected from ponds and
ditches for Sccnedesmus and Pediastrum. The former may
often be found in great numbers on the glass sides of jars or
aquaria.

{d) In midsummer search quiet pools for Water Nets. With
a fine scissors cut out a piece of one and mount carefully in
water. Stud}^ with a low power of the microscope. Some of
the coenocytes will })e found producing zoospores. Search
for young nets forming within the old coenocytes.

(e) Collect fresh specimens of Sea Lettuce, put into a jar of

176 PHYLUM II. CHLOROPHYCEAE

water, and watch the jiroduetion of zoospore^. Knteromorpha,
which is common in brackish waters in the interior, may be
substituted for Ulva.

(/) Study Ulothrix in hke manner. It may be grown in an
aciuarium very easily, so as to be obtainal^le at an}^ time, even
in the winter. Draparnaldia ma}' be found in running fresh
water.

(g) Specimens of Oedogonium may l)e obtained by examining
the small sticks and stems of aquatic plants from quiet waters.
They may be recognized by the enlarged oogones.

(h) The Disk Algae occur in fresh-water pools as little green
masses adhering to leaves, sticks, the stems of living plants,
etc., where they should be sought. The sexual process and
the development of the sexual organs occur in May, June, and
July.

LITERATURE OF CHLOROPHYCEAE

Frank S. Collins, The Green Algae of North America, Tufts
College, 1909.

G. S. West, A Treatise on the British Fresh-water Algae, Cam-
bridge, 1904.

CHAPTER IX

PHYLUM III. ZYGOPHYCEAE

THE CONJUGATE ALGAE

249. These plants are typically unbranched, unat-
tached filaments, which easily fragment into short
segments, or single cells. They are green, with chloro-
phyll, but in many cases this is obscured by the presence
of a yellow-brown pigment in the cells. They propagate
by the fission and ultimate separation of cells (hormo-
gones) or by the formation of spores, but are wholly
destitute of zoospores. They generate by the union of
the protoplasm of pairs of ordinary cells (isogametes).

250. The dominant idea in this phylum is the physio-
logical sluggishness of the cells, resulting in the feeble
attachment of the cells to one another and the easy and
usually early fragmentation of the filament, the absence
of zoospores, and the reduction of the sexual roi)roduction
to the sluggish union of the scarcely modified proto-
plasms of two vegetative cells. This is a phylum on the
down-grade, and all of its members show more or less
structural degeneration.

There are two classes:

I. Chloroi)hyll p;rceii phiiits with cellulose walls.

Class 5. CONJUGATAE.

II. Mostly yellowish-brown plants, with silicificd walls.

Class G. Bacillarioideak.
12 177

178 PHYLUM III. ZYGOPHYCEAE

Class 5. CONJUGATAE
In this class the lowest type is that of the filamentous
Pond Scums, well represented everywhere by species of
Spirogyra. In this genus the ribbon-shaped chloro-
plasts are longer than the cells, and are therefore more or
less spirall}^ coiled. In generation two cells unite by
pushing out short opposing tubes until they come in

contact; the contact walls then are

absorbed leaving an open channel
from cell to cell, and through this
the protoplasm from one cell slowly
fH. 70.— Spirogyra. passcs to the othcr, the two proto-
plasms uniting into one mass, which
rounds up and covers itself with a thick wall, thus
forming a resting spore. The resting spore thus formed
is set free by the decay of the dead cell- walls of the old
filament surrounding it; it then falls to the bottom of the
water, and remains there until the proper conditions for
its growth appear.

251. More commonly this sexual union takes place
between cells of different filaments, as described, but in
some species such a union takes place between contigu-
ous cells in the same filament, the tubes forming at the
contiguous ends.

252. The germination of the resting spore is a simple
process. The inner mass enlarges and bursts the outer
hard coat; it then extends as a cylindrical cell, in which
after a while a transverse partition forms, and this is
followed by another and another, until an extended
filament is produced.

253. In the Desmids the filaments usually fragment
easily into single cells, which then grow more or less after
separation. However in the lower Desmids the cells are
still in filaments (Family Desmidiaceae). In the second

DESMIDS 179

family {Closteriaceae) the elongated cylindrical cells sepa-
rate early and become more or less attenuated, as in
Closterium. In a third family (Cosma-
riaceae) the flattened, more or less con-
stricted cells separate very early, and
in many cases become terminally much
lobed or otherwise modified. Of the
less modified desmids the species of Fig.ti.— Desmids:

j^ . , 1 1 •! Closterium, Cosma-

Cosmarmm are good examples, while num. and Micra-
those of Euastrum and Micrasterias are
greatly modified, the cells of the latter being divided
into mam' pointed lobes.

254. In generation the desmid cells break open at the
middle (where there is commonly a joint in the wall) and
the two protoplasms (isogametes) unite into a zygote,
which eventually becomes a thick-walled resting spore.
After some time the resting spore germinates by ruptur-
ing its wall and dividing the contents into two, four or
eight new non-ciliated cells which eventually become like
the parent cells.

255. Desmids are fresh-water plants, floating free in
the waters of quiet pools, or entangled with mosses or
other aquatic plants.

Class G. BACILLARIOIDEAE

256. The plants of this class are the Diatoms, num-
bering about 5700 species, or even as many as 10,000
species in the opinion of some botanists. Some diatoms
are filamentous, but in the greater number the filaments
fragment early into single cells. The cells contain
chlorophyll, which is commonly hidden by the addition
of diatomin, a yellow-brown pigment. A few diatoms
are colorless, and hysterophytic, and therefore are
''fungi.''

180 PHYLU:\r III. ZYGOPHYCEAE

257. Tlic ccUulusc walls in most tliatoms soon 1)C('ome
more or less silicified and rigid, and incapable of further
expansion. This is proV)ably a protective device, many
diatoms Hving at or near the surface of the ocean waters
where softer walls would be likely to be crushed. This
rigidity of their walls has brought about some structural
details that are peculiar to this group of plants, and
which are quite puzzling to the beginner if not considered
in connection with the origin of diatoms and their rela-
tionship to the filamentous types.

258. In order to understand the structure of any
diatom it is necessary to consider it as one cell of a
cylindrical, angled, or flattened filament. These cells
are usually short (measured along the axis of the fila-
ment), so that when separated from the other cells they
lie with one end up, and thus show a cross-section of the
filament. Compare this with the end view of the cells
in a filamentous plant like Ulothrix or Spirogyra. As in
Desmids, the cells of the Diatoms are transversely
jointed, allowing the two halves (really the two ends of
the cells) to move apart, and thus enlarge the cell cavity.
Each half of the silicified wall is shaped like a paper box
cover, the flat surface corresponding to the ''valve" and
the curving ring to the ''girdle." Sometimes there are

additional rings known as " interzones, " giv-
ing a good deal of flexibility to the diatom
cell wall.

259. Diatoms propagate (1) by the enlarge-
ment of the protoplasm of the cell resulting in
its elongation, and the formation of two walls
propagiui^ in the plane of the joint which become the
of a diatom. ^^^^ ^f ^j^^ ^^^.^ ^^^^ ^^^g (''fission"); (2) by

the separation of the two halves of the cell allowing the
escape of the protoplasm which then rapidly grows into a

DIATOMS LSI

larger now coll (''rojuvonosccnce"). Thoy gonorato ])y
tlio oscapo and union of tlio protoplasms of two contigu-
ous colls whose half-cells have separated, resulting in the
formation of one or two new and usuall}- much larger
cells. Small biciliate isogametes have been doubtfully
reported in some marine diatoms.

260. There are two general kinds (orders) of Diatoms,
namely, the Round Diatoms (Eupodiscales) with the cells
mostly round in end view, and the Flat Diatoms
{Xaviculales) with the filaments flattened in end view.

261. The Round Diatoms are mostly

marine and fossil. The ends of the cells J . 1 , 1 .L.L
are usually marked radially with lines or (^

rows of dots, as in Melosira, Coscinodiscus, fig. 73.— a
Actinodiscus, etc. Some Round Diatoms Meioglr?!^"'"'"'
form long filaments (Melosira).

262. The Flat Diatoms occur abundantly as fresh-
water, marine, and fossil plants. The ends of the cells

(transection of the flat filament) are often
marked transversely or pinnately by dots or
lines. In many of our most common Flat
Diatoms (e.g. Naviculaccae) there is a me-
dian longitudinal slit (''raphe") in the end
FiS^D^at^n^ wall, which probabl}^ has to do with the mo-
Baciiiaria. ' ^-j-^^. cxhi))ited by thoso pUiuts (Par. 174).

263. Origin of Zygophyceae. It may be assumed that
the plants of this phylum have been derived from other
filamentous plants, and that the adhesion of cell to coll,
and the consequent formation of a multicellular plant
body, had l)ocome a well established habit long before
the peculiarties arose which set them off as Zygophy-
ceae. We must search among the Confervoideae of the
pnH'oding phylum for the ancestral tyi)os from whioh the
Conjugate Algae may have descended. Such plants as

182 PHYLUM III. ZYGOPHYCEAE

IMicrospora and Ulothrix could very well serve as the
originals which have been modified successively into
the Pond Scums, the Desmids and the Diatoms. The
limited fragmentation of the filament in Ulothrix is so
much increased in the Conjugate Algae as to render the
production of zoospores unnecessary. In like manner
the sluggish protoplasm of the Conjugate Algae is corre-
lated with the disappearance of the freely motile gametes
and the degeneration of the sexual process into a sluggish
conjugation, which in some Desmids and Diatoms results
in the partial (if not complete) suppression of the sexual
act. According to this view ''conjugation" is the result
of degeneration. It is sexual reproduction on its way
toward disappearance. Instead of affording an example
of the beginning of sexuality, as has so often been sug-
gested, these plants show sexuality on its way to disap-
pearance. Furthermore, it is obvious that the Conjugate
Algae constitute a lateral phylum which is related to
other phyla only in its lower members, and that its higher
members depart more and more widely from all other
forms of plants.

Laboratory Studies, (a) Collect a quantity of bright green
pond scum, which always abounds in shallow ponds and pools in
the spring, summer and autumn, and preserve in a dish of
water. Collect, also, some which has begun to turn yellow and
brown. Upon mounting a little of the first in water and exam-
ining with a high power it will be found to consist of threads
of cylindrical cells, each containing one or more spiral chloro-
plasts (Spirog>Ta) or star-shaped chloroplasts (Zygnema).
Upon mounting some of the second collection, here and there
the formation of resting spores may be observed. In all cases
care must be taken not to mount too great a quantity of the
material, nor to injure the plants }:)y rough handling.

(b) Collect a quantity of pond scum and other aquatic
vegetation. IMount portions of this material and search for
desmids, using a low power objective. Two-lobed desmids

LABORATORY STUDIES 183

(Cosmarium) of a bright green color may frequently be found.
The hirge kuiatc desmids (Closteriuni) are often more common.
In the hitter the clear protoplasm at each end is always stream-
ing rai)idly.

(c) Round Diatoms may be obtained of dealers in laboratory
material, or mounted slides may be used. A few Round
Diatoms may be found occasionally in fresh-water ponds, and
they often occur on the surfaces of marine seaweeds.

(d) Collect a little of the brownish-yellow scum which in
earl}^ si)ring gathers on the top of the water of brooks, ditches,
and pools. Mount in water and examine with a high power.
Hundreds of Flat Diatoms may be seen moving rapidl}- in
ever}^ direction across the field. In any such preparation many
species of various shapes will be found. The prevailing forms,
however, are much flattened and somewhat diamond shaped
in end view.

(e) Study in like manner the slimy coating upon dead leaves
and twugs in water in the summer for diatoms. On some of
these very fine markings ma}^ be found.

(/) Here again mounted shdes of Flat Diatoms may be
used with profit, but it is well to study Kving specimens so as
to be able to observe their motihty.

(g) For future study in the laboratory the Conjugate Algae
should be preserved in bottles of water containing just enough
alcohol, glycerine, formaldehyde or carbolic acid to prevent
their decay. One-fourth or fifth of the first and second, one-
tenth of the third, and enough of the last to give a decided
odor, will usually do well enough. A 2 per cent, solution of
potassium acetate made light blue by addition of copper suljihate
will preserve the green color of these i)lants, if kept in the dark.

LITERATURE OF ZYGOPHYCEAE

0. S. West, A Treatise on the British Fresh-water Algae, Cam-
bridge, 1904.

Frank S. Collins, The Green Algae of North America, Tufts
College, 1909.

0. B. De Toni, Sylloge Algarum, Vol. II, Padua 1S91-1S94.

H. Van Heurck. ^l Treatise on the Diatomaccac (Engl, trans.),
London, 1896.

chapti:r X

PHYLUM IV. SIPHONOPHYCEAE

THE TUBE ALGAE

264. These plants are filamentous, saccate or erect-
dendroid, and are composed of coenocytes instead of dis-
tinct cells. In the first (primitive) forms the plant body
consists of a row of long bi- or poly-nucleated segments
(coenocytes) arranged in a simple or branched filament,
which is more commonly rooted below. When the fila-
ment has cross partitions it is said to be septated. In
many Tube Algae there are no partitions in the vegeta-
tive portions of the plant, and such are said to be
continuous.

265. They are propagated (1) by the internal division
of the protoplasm of a coenocyte (sporangium), or even of
the whole plant into spores (ciliated zoospores in the
water — walled spores in the air) ; (2) by the condensation
of definite masses of protoplasm directly into thick-walled
spores (chlamydospores). Their generation shows all
gradations including the union of (1) ciliated isogametes;
(2) ciliated heterogametes; (3) ciliated sperms, with eggs;
(4) antherid nuclei, with eggs — in all cases producing
zygotes, which usually become thick-walled resting
spores.

266. The dominant idea here is the development of
coenocytes instead of distinct cells, and this has been
consistently adhered to even when the plant body has
shown otherwise a considera])le amount of differentiation.

184

CLADOPHORA AXD VAUCHERIA

1S5

267. They are typically aquatic, green plants (holo-
phytes), but many have become parasites or saprophytes,
and suffered degradation into ''fungi" (hysterophytes).
The number of species now known is about 1260. The
holophytes are readily separated into two classes, the
Lower Tube Algae (Vaucherioideae) and the Higher
Tube Algae (Bryopsidoideae), and from the first have
been derived a considerable number of hysterophytes
which may be separated as a class of Tube Fungi, or
Lower Fungi (Phycomyceteae).

268. Water Flannel (Cladophora) is one of the com-
monest genera of the Lower Tube Algae, occurring in
large tangled masses of stout branched fila-
ments in fresh-water streams, or even in
salt waters. Its coenocytes have thick
w^alls, with two to many nuclei. In their
propagation and generation they so closely
resemble Ulothrix and Microspora that they
were formerly included in the same famil3^
Zoospores with two or four ciUa escape

from the segments and after a free-swimming period
come to rest and grow directly into new plants. Like-
wise biciliated isogametes issue from similar segments,
and fuse into zygotes.

269. The Green Felts (Vaucheria) are good repre-
sentatives of one of the families in which the plant body

is a continuous coenocyte. They are
coarse, green, tubular, branching and
rooted plants which grow in abun-
dance on the moist earth in the vicinity
of springs, and in shallow running
water, forming dense felted masses.

270. They propagate by large compound motile zoo-
spores, formed in the ends of the branches. Each zoo-

FiG. 75.
Cladophora.

Fig. 76. — Vaucheri;

186 PHlTU^r IV. SIPHONOPHYCEAE

spore eventually forms a wall around itself, and then
proceeds to elongate into a new plant-body.

271. Generation takes place in special, usually lateral,
segments. Both antherids and oogones develop as pro-
tuberances upon the stem. The antherid is long and
rather narrow, and soon much curved; its upper portion
becomes cut off by a partition, and in it very small bi-
ciliated sperms are developed in great numbers. The
oogone is short and ovoid in outline, and usually stands
near the antherids. In it a partition forms at its base;
the upper portion becomes an oogone, and its protoplasm
condenses into a rounded body, the egg. At this time
the wall of the oogone opens, and permits the entrance of
the sperms which were set free by the rupture of the
antherid wall.

272. Upon coming into contact with the egg one sperm
fuses with it; the fertilized egg (zj^gote) immediately
begins to secrete a wall of cellulose about itself, and it
thus becomes a resting spore. After a period of rest the
thick wall of the resting spore splits, and through the
opening a tube grows out which eventually assumes the
form and dimensions of the full-grown plant.

Here must be placed half a dozen families of hystero-

phytic plants, the ''Tube Fungi," often known as the

''lower fungi," and to be regarded as degen-

j{i erate descendants of some such holophytic

' form as Vaucheria.

273. The Water-molds {Saprolegniaceae)
are colorless saprophytes or parasites. They
are generally to be found in the water,
Saproiegnia. attached to the bodies of living or dead
fishes, crayfishes, etc., or in decaying animal
or vegetable matter, in or out of the water. The plant-
body is greatly elongated and much branched, and is

WATER MOLDS 187

basally rooted. All its vegetative portion is continuous;
the reproductive portions only are separated from the
rest of the plant-body by partitions.

274. The propagation is very much the same as in
Green Felt. It may be briefly described as follows for
Saprolegnia: The protoplasm in the end of a branch
becomes somewhat condensed, a partition forms, cutting
off this portion from the remainder of the filament, and
the whole of its contents becomes converted by inter-
nal cell division into zoospores provided with two cilia.
These soon escape from a fissure in the wall and are active
for a few minutes, after which they come to rest and their
cilia disappear. In one or two hours they germinate by
sending out a filament, from which a new plant is quickly
produced.

275. The sexual organs also bear a close resemblance
to those of Green Felt. The oogones are spherical, or
nearly so (in most of the species), and contain from one
to many eggs, which are fertilized by means of antherids,
which usually develop as lateral branches just below the
oogones. Fertilization takes place by the direct contact
of the antherid and the passage of its contents into the
oogone by means of a tubular process from the former.
In some species there is no transfer of the contents of
the antherid, and in others again there are no antherids.
These eggs must therefore develop without fertilization,
indicating that sexuality is disappearing in these plants.
Eventually each egg becomes covered with a wall of
cellulose and is thus transformed into a resting spore,
which later germinates by sending out a tube, as in
Green Felt.

276. The Downy Mildews {Peronosporaceae) and
White Rusts (Alhuginaccae) live parasitically in the
tissues of higher plants. They are composed of long

188 PHYLUM IV. SIPHONOPHYCEAE

brant'liino; tubes, whose cavities are continuous through-
out. They usually grow between the cells of their hosts,
and draw nourishment from them ])y means of little
Dranches Hiaustoria), which thrust them-
selves through the walls.

277. The asexual spores (conidia) are
produced upon branches (conidiophores)
which protude through the epidermis of
Fig. 78.— Piasmopara the host. In the Downy Mildews (Per-
onospora, Phytophthora, Piasmopara,
etc. ) these branches find their way through the breath-
ing-pores and bear their spores singly upon lateral branch-
lets; in the White Rusts (Albugo) the conidia-bearing
branches collect under the epidermis and rup-
ture it. Here the conidia are borne in chains
or bead-like rows.

278. In some genera the relationship to the
Water Molds is shown by the fact that these
conidia upon falling into water become true
sporangia, within which few to many zoospores
are produced. These after a free-swimming period be-
come motionless and germinate by means of a tube which
bores its way into the host. In two genera, however
(Bremia and Peronospora), the conidia themselves germ-
inate directly by a tube.

279. The sexual reproduction takes place in the inter-
cellular spaces of the host. Lateral branches of two kinds
appear upon the hyphae; those of one kind (the young
oogones) become greatly thickened and finally assume a
globular shape; the other branches (the young antherids)
become elongated and club-shaped, both becoming sepa-
rated from the main filament by cross partitions. The
antherid comes in contact with the oogone which it
penetrates by a tube, through which fertilization occurs,

BLACK MOLDS LS9

and th('reu])oii the egg socretes a thick doubh' wall, and
becomes a resting spore.

280. The resting spores remain in the tissues of the
host until the latter decay, which is generally in the
spring. Germination then takes place, in some species
by the production of a tube (either germ-tul)e, or co-
nidiophore), in others by the division of the protoplasm
into zoospores whose subsequent development is like
that described above in case of the conidia.

281. The Black Molds (Miicoraceac) are saprophytic
and sometimes parasitic plants; they are composed of
long branching non-septate filaments (hj^phae), which
ahvays form a more or less felted mass, the mycelium.
The protoplasmic contents of the filaments are more or
less granular, but they never develop chlorophyll. The
cell walls are colorless, except in the fruiting filaments,
which are often dark-colored or smoky (fuliginous);
hence the name of Black Molds.

282. The mycelium sometimes develops exclusively in
the interior of the nutrient medium; in
other cases it develops partly in the me-
dium and partly in the air. In some
species the mycelium may attack the fila-
ments of other plants of the same order,
and even exhibit a weak parasitism upon
higher plants.

283. The reproduction of black molds is asexual and
sexual. In the asexual reproduction (propagation) the
mycelium sends up erect filaments, which produce few or
many separable reproductive cells — the spores. The
method of formation of the spores in a common black
mold (Mucor) is as follows: The vertical filaments,
which are filled with protoplasm, become enlarged at the
top, and in each an arched partition forms, constitut-

190 PHYLU.M IV. SIPHONOPHYCEAE

ing the so-called columella. The protoplasm in the
enlarged terminal segment (sporangium) divides into a
large number of minute masses (spores) each of which
surrounds itself with a cell wall.

284. The spores are set free in different ways: in some
cases the wall of the sporangium is entirely absorbed by
the time the spores are mature; in other cases only por-
tions of the wall are absorbed, producing fissures of va-
rious kinds. The spores germinate readily when on or in
a substance capable of nourishing them, by sending out
one or two filaments, which soon branch and give rise to
a mycelium. If kept dry, the spores may retain their
vitality for months.

285. Sexual reproduction (generation) may take place
after the production of asexual spores, but it appears to
be of rare occurrence in our commonest species. Two
filaments in the air or within the nutritive medium, in
contact send out small branches (here regarded as re-
duced sexual organs, the one an antherid, and the other
an oogone) ; these elongate and become club-shaped, and
at the same time become more closely united to each
other at their larger extremities; a little later a transverse
partition forms in each at a little distance from their
place of union; the wall separating the new terminal seg-
ments is now absorbed, and their protoplasmic contents
unite into one common mass (the zygote) ; the last stage
of the process is the secretion of a thick wall around the
new mass, thus forming a zygospore, i.e. a resting spore,
which eventually germinates and sooner or later gives
rise to a new plant.

286. In some Black Molds both gametes are formed
upon different branches of the same mycelium (homo-
thallic forms, monoecious). In many, however, the
plants are of two kinds (dioecious), and sexual reproduc-

INSECT FUNGI 191

tion occurs only when hyphae of the two kinds come into
contact (heterothaUic forms).

287. The Insect-fungi {Entomophthoraccne) are well
represented by the Fly-fungus {EntoniophtJiora muscae)j
which in the autumn is destructive to house-flies. It
consists of small tubular coenocytes which grow in the
moist tissues of the fly, and at last pierce the
skin, producing minute terminal spores, which
give the fly a powdery appearance. These
spores (called, also, conidia) may be seen as a
whitish halo surrounding the spot to which the
fly (now dead) has attached itself. Round
and thick-walled resting spores (formed by
the union of gametes similar to those of Black
Molds) have been observed in some species, and may be
studied in the Grasshopper Fungus {Entomophthora
grylli), which destroys great numbers of grasshoppers
every autumn.

The Sexual Organs of the Water Molds, Downy Mil-
dews, Black Molds, and Insect Fungi show a progressive
degeneration from the typical structure occurring in the
Green Felts. In the Water Molds there is a suppression
of the sperms, the antherid protoplasm being transferred
directly to the egg. This is continued with little change
throughout the Downy ]\Iildews and White Rusts, which
being non-aquatic could scarcely make use of motile
sperms. The sexual organs of the Black Molds are
apparently of the same general type as those of Water
Molds and Downy Mildews, each being an end cell cut
off from a reproductive filament, but in Black Molds
these filaments show little differentiation. They unite
prematurely, before the oogone has developed an eg^,
and before the other filament has developed its anthei-
idial protoplasm. They are physically under-developed

192 PHYLUM IV. SIPHONOPHYCEAE

sexual organs, and are to be regarded as mere vestiges of
the fully developed antherids and oogones of the Green
Felts. They are sexual organs on the road to extinction.
In the Insect Fungi the sexual organs are still more de-
generated and vestigial in structure.

288. The commonest example of the Higher Tube
Algae is the little Bladder Alga (Botrydium), found on

»^ moist ground. It is a globular coenocyte

a millimeter or two in diameter, with a
branching root below. When in good
vegetative condition it is bright green, but
later it may be dull red. It is known to
Fig 82— P^opagatc by uniciliated zoospores, and

Botrydiuni^ind thick wallcd chlamydosporcs. Its genera-
tion was long supposed to be by the union

of biciliated isogametes, but these are now thought to

belong to Protosiphon, a similar plant ^vith an unb^anched

root.

289. In the shallow waters of the ocean there are
larger Bladder Algae (Valonia) that when young are
single globose or club-shaped coenocytes, firmly rooted
below. They may reach several centimeters in height,
and ultimately become more or less divided
into segments. Their propagation and
generation appear to be much like that
of the little Bladder Algae.

290. The Sea Ferns (Bryopsis) are erect,
slender, cylindrical, single coenocytes, rooted
below, and pinnately branched above, and fig. 83.— Bry-
look like little trees, or fern-leaves. They Slaru."^ '^'^"
generate by biciliated heterogametes. They

occur along the shores of the warmer oceans.

291. The pretty Sea Umbrellas (Acetabularia) are
also erect, slender, cylindrical, single coenocytes, rooted

STONEWORTS

193

below; but here the branches are in one terminal whorl
and are united into an umbrella-like structure. They
generate by biciliated isogametes. They occur in shal-
low tropical or sub-tropical marine w^aters.

292. In the Stoneworts (Charales) we find the highest
development of the coenocytic structure. The plants
are erect, slender, cylindrical rows of coenocytes, rooted
below, and bearing many whorls of free branches. The
stems are often corticated with a parallel layer of smaller
coenocytes. They occur in the fresh or brackish waters
of ponds and lakes.

293. The generation of Stoneworts is heterogamous,
that is by the union of bicihated sperms, with non-ciliated

eggs. The sperms are pro-
duced in compound antherids
which are globular many-
celled bodies, in the interior
of which certain multicellular
filaments (the antherids) pro-
duce the sperms singly in the
cells. Each sperm is a spiral
thread of protoplasm, provided with two long cilia at
one end, by means of which it swims rapidly through
the water.

294. The oogone is a single cell, which soon becomes
covered (corticated) by the growth from below of a layer
of five spirally wound coenocytes, which are prolonged
into a 5- or 10-cclled crown. This covering, which here
develops before fertilization, is analogous to the protec-
tive covering which in Coleochaete, forms after fertiliza-
tion has taken place. In the oogone is the egg, which is
non-ciliated, and very much larger than the sperms.

295. The sperms enter the opening at the apex of the
oogone and one of them entering the egg fertilizes it.

Fig. 84.— Chara.

194 PHYLUM IV. SIPHONOPHYCEAE

The oogone and its covering now become thicker-walled
and constitute a spore-fruit. The latter soon drops off
and falls to the bottom of the water, where it remains at
rest for a time and later germinates by sending out a
jointed filament, which eventually gives rise to a branch-
ing plant like the original.

296. About IGO species of Stoneworts are known, all
included in the single order Charales. The two f amiUes,
NiteUaceae and Characeae are separated by the structure
of the crown, which is 10-celled in the former, and 5-
celled in the latter. The principal genus of the first
family is Nitella, and of the second Chara; each contains
in this country a dozen or more widely distributed
species.

297. Summary. The attempt has been made in the
foregoing pages to treat the coenocytic plants in accord-
ance with the theory that they have been derived from
the many-celled filamentous algae of the Ulothrix type
in the Phylum Chlorophyceae, where the segments of the
filaments are true cells, each having a single nucleus.
And it is regarded as probable that the coenocytic struc-
ture was gradually attained by the formation of fewer
and fewer partitions in the succession of filamentous
plants.

298. Accordingly the Cladophoraceae are given place
at the beginning of the phylum, and they are regarded
as having given rise to two general lines of development,
one of which is characterized by the retention of a dis-
tinctly filamentous structure, while in the other the
coenocyte undergoes great differentiation into ''root,''
"stem" and "leaves." If we designate these Hues by
their highest holophytic representatives, we may call
them (1) the Vaucheria line, and (2) the Chara line.

299. In passing from Cladophoraceae to Vaucheriaceae

EVOLUTION OF SIPHONOPHYCEAE 195

the plant body has become almost completely non-septate
and the sexual reproduction has become heterogamic.
This plant body and heterogamic generation have been
bequeathed to the hysterophj^tes of this line (Class
Phycomyceteae) , and both suffer marked degeneration
in passing from family to family.

300. So also we may trace an evolutionary line from Cla-
dophoraceae to Valoniaceae (and Botrydiaceae), Bryop-
sidaceae, Dasycladaceae, and the Charales, in all of which
the erect, rooted and regularly branched plant body
becomes more and more marked. Here there is again a
passage from isogamy to heterogamy.

Laboratory Studies. Note: In addition to those mentioned
below many marine forms, as Codium, Penicillus, Halimeda,
Udotea, etc., occur in warm seas, and may be studied with
profit, (a) Collect a quantity of Water-flannel (Cladophora)
and put it into a large dish of water, leaving it over night.
Next morning the side of the dish which is nearest to the hght
will show a green band at the water's edge, due to the mjTiads
of zoospores which escaped during the night. Mount a drop
of water and search for zoospores. Occasionally the escape of
zoospores may be seen by mounting a number of filaments and
searching carefully.

(b) Collect a quantity of terrestrial Green Felt (Vaucheria)
and preserve it in a dish of water. After a few hours a large
number of zoospores may be observed collected at the edge of
the water nearest to the light.

(c) Examine carefully mounted specimens of the bright green
filaments, and look for the thickened branches which produce
the zoospores.

(d) Select some of the oldest, j'cllowish filaments. Mount
and examine with a low power for the sexual organs. In col-
lecting specimens for the study of the sexual organs it is usually
necessary to take those masses which arc yellowish and appear
to be dying or dead.

(e) Kill a few flies in strong alcohol and place them in a dish
containing algae freshly gathered from some ditch or pool.
After a day or two the flics will usually be found to be covered

196 PH\XUM IV. SIPHOXOPHYCEAE

with whitish masses of radiating hj'-phae of Saprolegnia or
related genera. Remove some of these hyphae and examine
for zoospore formation. Somewhat later oogones and antherids
may often be found. A water mold {Saprolegnia ferax)
frequently occurs upon the bodies of young fishes, especially in
fish-hatcheries where it is occasionally very destructive.

(/) In the Spring the leaves and stems of shepherds'-purse
and peppergrass may often be found covered underneath with
a white mold-like growth {Peronospora parasitica). Carefully
scrape off a little of this growth and mount first in alcohol,
afterward adding a little potassium hydrate. The irregularly
branching filaments will be seen to bear here and there white,
broadly ellipsoidal conidia. Similar studies may be made of
the Grape-mildew {Plasmopara viticola) on grape-leaves in
autumn, and the Lettuce-mildew {Bremia lactucae) on cultivated
and wild lettuce from spring to autumn.

(g) Make very thin cross-sections of a leaf affected with a
Downy Mildew, when the latter has passed the period of its
greatest vegetative activity. Mount in alcohol (to drive out
air-bubbles), then add potassium hj'drate, and look for the
resting-spores, which in some species are of a dark brown color.

(h) White Rusts occur on man}?- plants: one {Albugo Candida)
on shepherd's-purse, peppergrass, radish, etc.; another {A.
hliti) on Amaranthus; and another (.4. portulacae) on purslane.
For conidia make very thin cross-sections of leaves, through a
white-rust spot, and mount as above. The resting spores
(which are dark brown) are easily obtained in the leaves of
Amaranthus and purslane and in the distorted stem of the
radish.

{i) In the study of Black Molds it is mostly necessary to
make use of alcohol for freeing the specimens of air; afterward
they usually require to be treated with a dilute alkah (as a
weak solution of ammonia or potassium hydrate), which
causes the filaments to swell up to their original proportions.

{j) Cut a lemon in two, and, squeezing out most of the juice,
expose the two halves to the air af an ordinary laboratory or
living-room for a few days, when various molds will begin to
develop. Under favorable circumstances Black Mold (Mucor)
will predominate. It can be told by its dark color and the
minute round black sporangia on the ends of the erect filaments.

LABORATORY STUDIES 197

Mount a few filaments (as directed in i above) and examine
filaments, sporangia, and spores.

{k) Moisten a piece of bread and then sow here and there on
its surface a few spores of Black Mold; cover with a tumbler or
bell glass. In a few hours a new crop of Black Mold will Ijogin
developing. The nutritive mycelium may be studied by
teasing out small bits of the newly infected bread.

(0 Place several clean glass slides in contact with a culture of
black mold, as described in (^•). By removing these at different
times the various stages of growth of the mold may be easily
studied.

{m) Collect a number of large fleshy fungi (Boletus, Lactaria,
Agaricus, etc.) and place under bell jars for a couple of days.
Usually a cream-colored mold {Sporodinia grandis) will begin
to develop upon some of these. Transfer it to pieces of bread
as in (A-) and study in a similar way. After a few days the
zygospore formation will be observed, as this species is homo-
thallic.

{n) In the latter part of summer and in the autumn examine
the dead flies which adhere to windowpanes, door-casings, and
especially to wires and strings hanging from the ceiling. ' The
whitish powder around the fly will indicate the presence of the
Fly-fungus {Entomophthora muscae). Mount some of this
white powder in water and examine under a high power. Tear
out small bits of the distended abdomen of the fly, and examine
for internal portions of the parasite.

(o) In the autumn look for dead grasshoppers attached to the
tops of weeds and grasses. Examine their interior tissues for
thick- walled resting spores of Entomophthora grylli.

(p) In damp weather in the summer look for Botrydium on
the hard, smooth ground of unused paths. It often appears
on compact soil in greenhouses in the winter.

iq) Specimens of Valonia, Bryopsis, Caulcrpa and Acetabu-
laria may be obtained of dealers in laboratory material for
study and examination.

(r) Search the sandy margins of ponds, lakes, and slow streams
for Stoneworts (Charales). They are generally found in water
from a few centimeters to one or two meters in depth. Pre-
serve such specimens temporarily in water which is frequently
changed, but for future use preserve in alcohol. Study as
follows.

198 PHYLUM IV. SIPHONOPHYCEAE

(.s) INIoimt carefully a considerable portion of a fresh plant,
and examine its structure under a low power. Note that in
some species the stem is composed of a row of large coenocytes
surrounded by a coat of smaller ones. Look for the rapid
movement of protoplasm which is so marked in these plants.

(0 Mount several spore-fruits in various stages of develop-
ment. Note the covering layer of spirally coiled cells surround-
ing the oogone (in young specimens) or the resting spore (in
older specimens).

(u) Mount several full-grown compound antherids. Care-
fully crush them and look for sperms, which are produced in
chains of cells (antherids).

LITERATURE OF SIPHONOPHYCEAE

Frank S. Collins, The Green Algae of North America, Tufts
College, 1909.

G. S. West, A Treatise on the British Fresh-water Algae, Cam-
bridge, 1904.

F. E. Clements, The Genera of Fungi, Minneapolis, 1909.

W. Migula, Die Characeen, etc., in Rabenhorst's Kryptoga-
men Flora von Deutschland, Oesterreich u. d. Schweiz, Vol. V,
Leipzig, 1897.

CHAPTER XI
PHYLUM V. PHAEOPHYCEAE

THE BROWN ALGAE

301. The Brown Algae which are almost wholly marine
plants of shallow waters, numbering about 1000 species,
are all truly cellular, and range from small filamentous
few celled plants, to large massive organisms differenti-
ated into roots, stems and leaves. They are brown-
green in color, and contain other coloring matters in their
cells in addition to chlorophyll. They are propagated
mostly by laterally biciliated zoospores, and generated
in the lower families by isogametes, and in the higher
famiUes by heterogametes, their union in all cases pro-
ducing a simple zygote. The gradations in the sexual
union of the gametes include (1) biciliated isogametes,
(2) biciliated heterogametes, (3) biciliated for uniciliated)
sperms and non-ciliated eggs.

302. In this phjdum the dominant feature is the addi-
tion of the brown pigment, phycophaein, to the chloro-
phyll of the cells. With this character must be associated
the typically motile, usually biciliated gametes, produc-
ing simple zygotes upon uniting, and the rooted plant
body (from filamentous and small, to massive and
large.)

303. Brown Algae probably originated in the vicinity
of Ulotrichaceae in the Chlorophyceae. The phylum
constitutes a ''side line" diverging from the main evolu-
tionary stem or current.

199

200 PHYLU:M \. PHAEOPHYCEAE

304. Among the commonest of the smaller Brown Algae
are the species of Ectocarpus in which the plant body is
composed of simple or branched filaments which may

attain a length of many centimeters. They
are firmly rooted below, and their tufted
filaments float as dark brown masses in the
tide currents near the shore. They are
propagated by zoospores produced in one-
celled sporangia which occur on the sides
Ectocafpus. of the filaments. These zoospores are
oval, pointed anteriorly, and have two
long cilia which are attached near together at one side.
Generation takes place by the union of isogametes, re-
sembling the zoospores, but originating in many-celled
sporangia (gametangia) also occurring on the sides of the
filaments. This union takes place in the water after
both gametes have escaped from the sporangia, and it
results in the formation of a zygote, which soon germi-
nates and gives rise to a new plant.

305. The Kelps (Laminariaceoe) while large massive
plants are still of a low type. In the Flat Kelps, or
Devil's Aprons (Laminaria), there is a stout stem a cen-
timeter or so thick, and a decimeter to nearly a meter
long, firmly rooted below, and flat-
tened into a broad 'Ueaf" above.
The whole plant may be a meter or
even several meters in length, and
the ''leaf" a few centimeters to half
a meter in breadth. On the sur-
face of the ''leaf" there develop """• s^-^-^^-^"-
patches of 1-celled sporangia that produce zoospores
like those in Ectocarpus. Gametes are not certainly
known to occur in the Kelps.

306. Other kelps that are common on the Atlantic or

KELPS 201

Pacific coasts are the Sea Girdle (Cymathere) with a
narrow beautifully ribbed " leaf" ; the Sea Tree (Lessonia)
with a stout branching stem bearing many small leaves;
the Sea Palm (Postelsia) with an unbranched stem bearing
a tuft of leaves at the top; the Bladder Kelp (Nereocystis)
with a long, cord-like stem, often 10 to 15 meters long and
bearing an air bladder at the top, to which is attached a
tuft of large leaves; the Giant Kelp (Macrocystis) with a
long, slender, cord-like stem, sometimes 50 to 75 meters
long and bearing a row of large leaves toward its extrem-
ity, each with a basal air bladder; the Leafy Kelp (Egre-
gia) with a fiat stem which bears innumerable lateral leaf-
lets and air bladders.

307. The highest of the Brown Seaweeds are the Rock-
weeds and Gulf weeds (Fucales) in which the plant body is
of medium size (usually from a decimeter
to a meter in length), rooted below, and
massive and branching above. Their
tissues, too, show a considerable differ-
entiation; the cells are arranged in cell-
masses, and these are differentiated into
several varieties of parenchyma, and other
tissues approaching, in some instances, to the condition
which prevails in higher plants. Some species develop
air bladders in their tissues.

308. With the foregoing there is found a marked differ-
entiation of portions of the plant ])ody into general re-
productive organs, analogous to the floral branches of
higher plants. The sexual organs are developed upon
modified l^ranches, which differ more or less in shape and
appearance from those destitute of such organs.

309. In all Rockweeds the asexual reproduction
("propagation") has been suppressed, the emphasis l^eing
placed upon the sexual reproduction ("generation").

Fig. S7. — Fucus.

202 PHYLUM V. PHAEOPHYCEAE

310. In common Rockweeds (Fucus) of the seashore
the sexual organs are found in the thickened ends of the
lateral branches. The}^ occur on the walls of cavities
(conceptacles), which are spherical, with a small opening
at the top. The conceptacles are at first portions of the
general surface, and afterward become depressed and
walled in by the overgrowth of the surrounding tissues;
they are thus in reality portions of the general surface.

311. The walls of the conceptacles are clothed with
pointed hairs, which in some species project through the
opening, and among these are found the sexual organs.
The antherids are produced as lateral ])ranches of hairs;
each antherid is a thin-walled structure containing a
large number of biciliatecl sperms, which escape by the
rupture of the surrounding wall. Before rupturing,
however, the antherids detach themselves and float in the
water with their contained sperms.

312. The oogone is a globular or ovoid short-stalked
body containing eight eggs. These escape from the
oogone and float out through the opening of the concep-
tacle, into the open water. The sperms, which are lib-
erated at about the same time, gather around the
inactive eggs in great numbers, and by the vigor of
their movements sometimes actually give them a rotary
motion. Fertilization results from the union of one of
these sperms with the egg, the zygote thus produced
secreting a Avail of cellulose about itself.

313. In germination the zj-gote lengthens and under-
goes division into numerous cells; at the same time it
elongates below into root-like processes, which serve to
hold fast the new plant.

314. In the nearly related Gulfweeds (Sargassum) the
plant body is composed of a distinct stem, rooted below,
and bearing leaves above. The stem bears also many

GULFWEEDS 203

stalked air bladders which ])uoy up the plant when
rooted, and float it when torn free. The short, thickened,
elontrated and clustered axillary branches (receptacles)
which contain the conceptacles ma}' be dis-
tinguished easil}^ from the spherical air l^lad-
ders. There are many species, one of which
(Sargassum vulgare) is common along our
eastern coast as a low-tide plant, half a meter
to a meter long. Another smaller species Fig. 88.

/-» •/• \ n • '111 Sargassum.

{bargassum oacciferum) iloats m considerable
quantities in the so-called ''Sargasso Sea" of the central
Atlantic Ocean. Its proper home is in the West Indian
region, where it grows attached to rocks.

Laboratory Studies. Probably the best Brown Algae for the
beginner to take up are Ectocarpus, Laminaria, and Fucus.

(a) Good material of Ectocarpus for study may be obtained
of dealers in laboratory supplies. The specimens should be
examined with reference to tlic general form and appearance of
the plant body, and especially for the 1-celled, and the many-
celled sporangia.

(/;) Where fresh material cannot be secured, the Kelps may
be studied very well from preserved specimens, which can also
be obtained from dealers in botanical supplies.

(d) Make sections through the fruiting j)atc]ies and examine
the sporangia and ''paraphyses," that is, the elongated,
intervening protective cells.

(e) It is helpful to have jars of other Kelps, as Sea Palms,
Bladder Kelj)s, Giant Kelps, Leafy Kelps, etc., for macroscopic
observation.

(/) Secure specimens of Rockweeds, fresh, alcoholic, or dry.
Fresh ones may easily be found along the beach of the ocean
after a storm. AlcohoHc and dry specimens and even living
material can easily be procured by purcliase or exclianpe.
Make thin cross-sections through the conceptacles in the thick-
ened ends of the branchlets. When mounted in water, even the

204 PHYLUIM V. PHAEOPHYCEAE

sections from the drj" specimens will frequently show the sexual
organs quite well. It must be remembered that some species
are dioecious, i.e. have the antherids on one plant and the
oogones on another.

(g) Make very thin cross and longitudinal sections of differ-
ent portions of the plant bod}', and study the tissues. Note
particularly the boundary tissue (epidermis), and the cells
constituting the mid-ribs and harder portions of the stems and
leaves.

(h) Secure in like manner specimens of Gulfwced, and make
macroscopic examination of the plant body, then if there is
time available make cross-sections of the air bladders and the
receptacles.

LITERATURE OF PHAEOPHYCEAE

George Murray, An Introduction to the Study of Seaweeds,

London, 1895.
G. B. De Toni, Sylloge Algarum, vol. Ill, Padua, 1895.
W. G. Farlow, Marine Algae of New England and Adjacent

Coast, Washington, 1881.

CHAPTER XII

PHYLUM VI. RHODOPHYCEAE

THE RED ALGAE

315. The Red Algae are almost wholly marine plants,
in structure ranging from small, simple, cellular, attached
filaments to stout, massive, rooted plants which may
attain considerable dimensions (half a meter or more).
The smaller plants are often diffusely and beautifully
branched into quite intricate patterns, rising from a
short basal stem which is rooted below, while in the
larger forms there may be a thick, rooted stem
which bears one or more flat leaves above.

316. The cell walls of the Red Algae are
more or less gelatinous in nature and swell
greatly in fresh water, even dissolving. The
cells usually are connected with one another
by visible openings in their walls, so that the
protoplasm is continuous from cell to cell.

317. The cells contain chloroplasts, but their green
color is masked by the presence of a red or purple
coloring matter (phycoerythrin) and sometimes a blue
coloring matter (phj^cocyanin), so that the plants appear
red or purple, instead of green, although in fact they
are green; but lit must not be overlooked that a few
species are parasitic, and therefore devoid of coloring
matter!

318. The Red Algae are propagated by non-ciliated,
naked cells which are separated from the plant, either

205

206 PHYLUM VI. RHODOPHYCEAE

singly C'monospores") or in groups of fours ('Hetra-
spores"); these float away and on germination give rise
to new plants. They are generated heterogamically by
the union of non-motile sperms with enclosed eggs,
usually resulting in the growth of branching, sporebearing
filaments, mostly covered, and constituting a primitive
many-spored fruit (^'cystocarp").

319. In those species (by far the greater number of the
Red Seaweeds) in which tetraspores are produced, these

give rise to the sexual plants which
are mostly dioecious. The carpospores
from the latter give rise, in their turn,
to the tetrasporic plants. The nuclei
of the latter possess the diploid number

FiQ. 90. — Tetraspores. p ^ ±^ r j.i j*

of chromosomes; those oi the former
the haploid number, the reduction of chromosomes tak-
ing place during the divisions leading to the production
of the tetraspores.

320. Here the dominant characters are the reddish
pigment added to the chlorophyll of the cells, and the
development of the zygote into a sporiferous, usually
covered, tissue (the spore fruit; cystocarp). The im-
portant secondary characters are the definite and final
attainment of heterogamy, and the mostly symmetrically
branched and basally rooted plant body.

For the most part the Red Algae grow at very consider-
able depths in the waters of the ocean, although a few
occur near the shore, and a very few live in fresh water.
They are more abundant in the warmer waters, and be-
come less frequent as we go toward the poles. The
number of known species is about three thousand.

321. This phylum as a whole is poorly understood.
Very little consideration has been given to the physical
modification these plants have suffered through living

RED SEAWEEDS 207

(1) at such depths (where the Ught is greatly modified),
and also (2) in waters of such considerable salinity. It
is probal^le that this modification has masked their true
relationship to other plants, as well as to one another.

322. One of the lowest of the Red Algae is the common
"Laver" (PorphjTa), of the class bangioideap:, of all
coasts, in which the erect, deep purple, leaf-like, and
basally rooted, plant body is composed of a single layer
of cells. They propagate by monospores borne in the
cell layer. In their very simple generation certain cells
of the cell layer divide into non-ciliated sperms, while
others ])ecome very slightly modified into oogones, each
containing a single egg. The latter is fertilized by the
entrance of the sperm through an opening in the cell
wall, after which the zygote develops into usually eight
spores. The fruit is thus of very simple structure.

323. In Nemalion (which with the succeeding plants
belongs to the class florideae), a branching, filamentous
marine Red Alga, the clustered antherids
produce small spherical, non-ciliated
sperms. The oogone is prolonged into a
slender structure, the trichogyne, and to
this latter the sperm adheres and fertilizes
the egg. After fertilization the egg divides,
and each new cell sends out short crowded
branches which bear terminal spores. Here no protec-
tive envelope covers the spores, the fruit being very
simple. Asexual reproduction is not known.

324. Here may ])e noted briefly the Corallines (('oral-
lina) which are filamentous Red Algae which become so
heavily coated with lime as to efYectually hide their cells.
This lime coating is like an ancient coat of mail with its
flexible joints at intervals. The antherids and oogones
are in separate terminal cup-shaped structures, those con-

208 PHYLUM VI. RHODOPHYCEAE

taining the oogones becoming the fruit after fertilization.
Tetraspores occur in similar cup-shaped structures.

325. Polysiphonia contains plants in Avhich the branch-
ing, filamentous plant body is composed of more than one
row of cells, usually of a central row surrounded by an
outer layer, completely covering it. These shallow-
water plants are often of marked beauty both in struc-
ture and coloring. The tetraspores are
produced in unmodified or slightly swollen
branches, and originate within the tissues,
but with the increase in size of the tetra-
sporangia they eventually reach the surface
and sUp out as large, deeply colored naked

Polysiphonia. ccUs. The spccial antheridial branches
consist of a central axis with numerous
short, crowded, radiating branchlets whose extremi-
ties (antherids) abstrict the naked, colorless sperms.
The oogone possesses a trichogyne, and is surrounded by
a few protective cells. The sperms carried by currents
of water come in contact with the trichogyne, and
attach themselves to it and form cell walls. The nucleus
of one passes into the trichogyne, and unites with that of
the oogone. The oogone now fuses (for nutritive pur-
poses, as there are no nuclear fusions) with a large nearby
cell (the auxiliary cell) into which the zygote nucleus
passes, and from which arise the filaments which produce
the carpospores. In the meantime the surrounding
cells produce an urn-shaped structure (pericarp) w^th
an opening at the top from which the liaked carpospores
escape at maturity.

326, Irish Moss (Chondrus) is so easily obtained at the
apothecaries that it may well be cited as one with a
parenchymatous, much branched plant body. The
oogones and afterward the spore fruits are immersed in

RED SEAWEEDS 209

the substance of the plant body. The plants are col-
lected, washed and dried and so preserved for human food
(blanc mange) and especially as a food
for convalescents. The structure of Cal-
lymenia is similar to that of Chondrus.

327. Among the very commonly col-
lected Red Algae on either coast are speci-
mens of Plocamium remarkable for the
beauty of its color and the regularity of
its branching.

Laboratory Studies, (a) It is better for the student to
stud}^ the li\'ing plants of this phjdum at the seashore, but the
beginner should not fail to make a study of such specimens as
may be accessible. Specimens for the study of structure should
be preserved in alcohol or formalin, using sea-water instead of
fresh water. However, much may be made out by the careful
examination of dried specimens which may be obtained from
dealers. Red Seaweeds may often be obtained ''in the rough'*
which can be moistened and then pressed out and dried for
study. Such material will often yield quite good si)ecimens.
Good mounted microscopic specimens may sometimes be ob-
tained showing the structure of the plant as well as of the sexual
and asexual reproductive organs.

(b) Make careful microscopical examination of Poly-
si})honia using alcoholic or formalin material. Such mounts
should be made in sea-water or a 3 per cent, salt solution to
avoid the swelling of the cell walls. In the course of the study
the following should be noted: (i) the cellular structure of the
plant body, (ii) the tetraspores, (iii) the antherids, (iv) the
oogones (difficult to find), (v) the cystocarps with their sj^orcs
(carposporos). The closely related Dasya may be substituted
for Polysii)honia.

(d) Dried specimens of some or all of the following genera,
mounted on heavy white paper, or cardboard, should be
available for macroscopic examination.

Porphvra, ]5atrachospermum, Corallina, Grinnellia, Xito-
phyllum, Polysiphonia, Dasya, Chondrus, Callophyllis, and
Plocamium.
u

210 PHIlTLUM VI. RHODOPHYCEAE

LITERATURE OF RHODOPHYCEAE

George Murray, An Introduction to the Study of Seaweeds,

London, 1895.
G. B. De Toxi, Sylloge Algarum, Vol. IV, Padua, 1897-1905.
W. G. Farlow, Marine Algae of New England and Adjacent

Coast, Washington, 1881.

CHAPTER XIII
PHYLUM VII. CARPOMYCETEAE

THE HIGHER FUNGI

328. The plants here brought together are all hystero-
phytes, being destitute of chlorophyll or any other simi-
lar coloring matter with physiological significance. In
accordance with the theory underlying the treatment of
all plant phyla in this book these hysterophytes must
have been derived from some of the preceding holophytes,
and it seems most probable that they came from the plants
in the phylum immediately preceding this one. In other
words, it is here assumed that the Higher Fungi arc allied
in structure to the Red Algae, and that the striking differ-
ences between them are correlated principally with the
change from the holophytic to the hysterophytic habit,
but it must be remembered also that the Red Algae arc
aquatic plants, while nearly all the Higher Fungi have
adapted themselves to terrestrial or aerial (non-aquatic)
conditions.

329. The Higher Fungi may be characterized as fol-
lows: They are filamentous plants, whose cells are always
without chlorophyll. Visible protoplasmic connections
between cell and cell are common. The filaments are
mostly isolated, but sometimes they are compacted into
parenchymatous masses, yet in few cases is there a con-
spicuous plant body comparable to the body of the re-
lated chlorophyll-bearing plants. This obsolescence of
the plant body results from the abandonment of tlie holo-
phytic habit, which has rendered chlorophyll-bearing

211

212 PHYLUM VII. CARPOMYCETEAE

cells unnecessary. The vestiges of the plant body are
present mainly as root-like absorbing organs, which di-
rectly bear the reproductive structures.

330. The Higher Fungi are propagated mainly by (1)
the separation of special terminal cells (conidia),and (2)
the separation of considerable fragments of the original
plant body. Zoospores are unknown in this phylum.
They generate by the union of the protoplasm of an an-
therid with the egg in an oogone, resulting in the produc-
tion of a spore-fruit (sporocarp) consisting of (1) sporog-
enous and (2) sterile tissues. In the fertilization of the
egg no instance is known of the production of motile
sperms.

331. Because of the reduction of the plant body the
spore-bearing structures, asexual and sexual, appear to
be relatively large. Moreover, because of the dependent
habit of the Higher Fungi it is necessary that many spores
should be produced, so that correlated with their depend-
ence is the great increase in the number of spores, and the
size of the spore-bearing structures. Thus it happens
that in many cases there is an actual increase in the size
and development of the spore-bearing structures, espe-
cially of the spore fruits. In many Higher Fungi no
sexual organs have been found, and it is thought that they
may have disappeared through the degradation of the
plant body.

332. This phylum contains about 64,000 known spe-
cies, and these may be arranged under three classes, with
an additional group of poorly understood, and unassorted
plants.

A. Spore fruits containing one or more asci, with ascospores.

Class ASCOSPOREAE.

B. Spore fruits containing one or more basidia, with basidio-
spores. Class Basidiosporeae.

ASCOSPHOREAE 213

C. Spore fruits much reduced, containing teliospores.

Class Teliosporeae.

D. Asci, basidia or teliospores unknown (artificial group).

Fungi Imperfecti.

Class 14. ASCOSPOREAE. The Ascus Fungi.

333. This large class includes chlorophyll-less plants
which differ much in size and appearance, but which agree
in producing their fruit-spores (carpo-

spores) in sacs (asci), and because they
are in sacs they are called sac-spores or
ascospores. These spore-bearing sacs
(singular, ascus; plural, asci) are end-
cells in the sporogenous tissue of the
fruit of the fungus, and they tend to Fio. 94.— Deveiop-

. . r 'f ^ • mcnt of asci and

develop m a layer of uniform height — ascospores.
the so-called ''h3^menium."

334. The sexual organs where known consist of oogones
and antherids, and, after fertilization, produce a spore-
fruit (sporocarp) which includes the sacs and sac-spores
(ascospores). The most common number of ascospores
is eight in each ascus; but it sometimes exceeds, and fre-
quently falls short, of this number, there being sometimes
no more than one or two.

335. In addition to the ascospores there are generally
one or more other kinds of spores which are developed
asexually. Some of these are doubtless to be regarded as
the equivalents of the conidia of the lower groups, and
accordingly will be so named here.

336. The Ascus Fungi include about 29,000 species,
representing 15 orders and 80 families. In the treat-
ment hero a selection has been made of representative
forms.

214 PHYLUM VII. CARPOMYCETEAE

The Disk "Lichens" (ORDER DISCOLICHENES)

337. The primitive Asciis Fungi (Ascosporeae) appear to
have been parasitic on small, green algae (myxophyceae
and khlorophyceae), and indeed this may have first
taken place in the water. It is known that some of the
proper Red Algae are parasitic, and the view here taken is
t hat in the Disk Lichens we have a group of plants in which
the parasitism has gone further, and has resulted in so
great a modification of the plant body as to place them in
another phylum.

338. The Disk Lichens abound almost everywhere —
on tree-trunks, rocks, old roofs, and in many regions upon
the ground. They are for the most part of a greenish-
gray color, and hence are often called ''Gray Mosses.''
Other colors, as black, purple, yellow, and white, are also
common.

339. The plant-body of a Disk Lichen is composed of
jointed, branching, colorless filaments, similar to those in

-TTTTv-r-T-r-r the other fungi, but usually more or less
compacted together into a thallus, or even
a branching stem. They obtain their
nourishment from little green Myxophy-
FiG. 95.— Section ceac oY ChlorophycesB to which the fila-
ments attach themselves parasitically.
These little hosts, which at first live free in water or on
moist surfaces, eventually come to live in the midst
of the moist tissues of the fungus parasite. They
were formerly supposed to be parts of the lichen itself,
and were called "gonidia," an objectionable term which
is still in common use.

340. Disk Lichens are all of rather small size, vary-
ing from a millimeter or so, to 20 or 30 centimeters in
length. For the greater part the plant-body is flattish,
and adherent to the surface upon which it grows, but

DISK LICHENS 215

some species have more or less elongated branching
stems.

341. Lichens propagate by the escape of some of the
algal cells, with attached fungal filaments by means of
eruptive areas C'soredia") on the plant body. When
one of these comes to rest upon a favorable substratum
it grows directly into a lichen plant body like the original.
Asexual spores appear to be wanting.

342. The sexual organs as far as known remind one
of those of the Red Algae. The oogone, which is a spiral
coil of cells, sends up a slender trichogyne to the surface
of the plant body. Fertilization takes place by means of
minute non-ciliated sperms which are
produced in countless numbers in nearby
cavities (spermogones) in the plant body.
The sperms come in contact with the f^j
projecting trichogyne (doubtless aided
by water) and fertilize the oogone, the organs^ orcou^ml.
result of which is the rapid upward

growth of filaments, the enlarged terminal cells of which
become asci. INIingled with the asci are long sterile cells
(paraphyses) for the protection of the asci and ascospores
in the hymenial layer, which forms a more or less disk-
shaped, or cup-shaped fruit. Such open fruits are known
as "apothecia, " in contrast with the closed fruits C'peri-
thecia") of many of the fungi to be taken up later.

343. The ascospores germinate by sending out one or
more tubes which develop directly into the ordinary fila-
ments of the lichen-body. Experiments have shown that
these filaments will not grow for any great length of time
unless they come into contact with green algae of the
proper species, to which they become attached, growing
rapidly and surrounding them. On the other hand, in
the moist tissues thus formed the green algae find protec-

216 PHYLUM VII. CARPOMYCETEAE

tion and ample opportunity for growing. There is thus
an association between these plants which is mutually
beneficial (symbiosis); the fungus lives parasitically upon

the green algae, to which in return it furnishes

shelter and moisture.

344. Among the Disk Lichens one of the

simplest is the Thread Lichen (Ephebe) found

on wet rocks. In it the fungus filaments
Fig. 97. grow ovcr and around the cells of Scytonema
(parasitic^on or Stigoucma filaments,
cy onema . ^^^^ Some other Disk Lichens are parasitic
upon Nostoc colonies, as in the Jelly Lichens (Collema,
Leptogium), while for the greater part they are parasitic
on species of Protococcus, as is the case with the great
majority of common lichens — Cladonia, Theloschistes,
Physcia, Parmelia, Ramalina, Usnea, etc.

The Cup-fungi (ORDER PEZIZALES)

346. The common Cup-fungus of the woods is a typical
representative of this order. The familiar cup- or saucer-
shaped growth is in reality the spore-fruit C'apothecium"),
while the plant itself is out of sight. The plant consists
of whitish, septate filaments which grow on or in the
ground or in rotten wood, drawing their nourishment from
decaying vegetable matter. These plants are therefore
saprophytes. Some Cup-fungi, however, are known
to be parasites.

347. But little is known as to the asexual reproduction
of the Cup-fungi, but in some species conidia have been
observed.

348. Thesexualorgansof Pyronema("Peziza")are pro-
duced by the sweUing up of the ends of certain of the fila-
ments of the plant into globular or ovoid cells, the oogones,
each having a projection (trichogyne). From below each

CUP FUNGI

217

oogone a slender branch grows out, and becomes the
antherid, which soon comes into contact with the tricho-
gyne. FertiUzation is effected by the passage of the
nuclei from the antherid into the trichogyne and from
thence into the oogone. As a result numerous branches
start out from the oogone,
forming the ascogenous
hyphae. At the same time
their arise numerous sterile
hyphae, from the tissues
beneath the oogone, and

, , 1 • , Fig. 98. — Pcziza, and Pyronema.

these grow upward mter-

mingling with the ascogenous hyphae, forming a dense
felted mass, which gradually takes on the size and form
of the spore fruit. The upper ends of the ascogenous
hyphae become enlarged into asci in which spores
are developed, while the sterile hyphae make up the
remainder of the apothecium, some of them standing
among the asci as the so-called paraphyses. The asci
and paraphyses all reach the same height, and make up
the inner surface of the cup (the ''hymenium"). Upon
escaping from the asci, the spores germinate and produce
the filamentous plants.

The Morels (ORDER HELVELLALES)

349. Morels are related to the Cup-
fungi, and like them are filamentous sapro-
phytes living in the ground. The conical
fruit is stalked, and its upper surface is
studded with hymenial areas in which are
asci and paraphyses similar to those of
the preceding order. A common species
is Morchella esculenia, in which the whitish fruit is

218

PHYLU.M VII. CARPOMYCETEAE

poc

Fig. 100.
Exoascus.

from 7 to 12 centimeters high. It is edible and bears
the name of Mushroom in the central United States.

350. The Plum-pocket fungus (Exoascus), which dis-
torts the young plums in spring and early
summer, is a greatlj^ reduced parasitic sac
fungus (Order Exoascales). Here the plant
consists of delicate threads which penetrate
the tissues of the plum, eventually producing
on the surface poorly developed asci which are
not aggregated into cups.

351. Two additional orders of Hchens — the Slit Lichens
(Graphidalcs) and Closed Lichens (Pyrenolichenes) are
abundantly represented by species of Arthonia, Graphis,
and Endocarpon. In the first order the apothecia are so
nearly closed as to leave only a narrow slit, and in the
second the asci are w^holly enclosed, the fruits being peri-
thecia, with only a minute pore or none at all.

352. The Slit-fungi (Order Hysteriales), are to be
associated with the Slit Lichens, and may be illustrated
by the Black Slit-fungus (Hystero-
graphium) whose saprophj^tic fila-
ments ramify through bark or old
wood and eventually produce small,
black, narrow, elongated, sessile
apothecia, whose edges approximate,
leaving only a narrow slit. Each
ascus contains eight muriform,
elongated spores, and the asci are intermixed with
branched paraphyses.

Fig. 101. — Ilysterogra-
phium.

The Closed Fungi (ORDER PYRENOMYCETALES)

353. The plants of this order are parasitic or saprophy-
tic filaments, and their spore-fruits, which are simple or
compound, are usually hard and somewhat coriaceous.

BLACK KNOT 219

354. A good illustration of the plants of this order is
the Black Knot {Plowrighiia morbosa), which attacks the
plum and eherr}^ In the spring the parasitic filaments,
which the previous year penetrated the 3'oung bark,
multiply greatly, and finally ])reak through the ])ark,
and form a dense tissue. The knot-like mass grows
rapidly, and when full-sized is usually from 2 or 3 to 10 or
15 centimeters long, and from 1 to 3 centimeters in
thickness; it is solid and but slightl}^ yielding, and is
composed of filaments intermingled with an abnormal
development of the bark-tissues of the host-plant.

355. The knot at this time is dark-colored, and has a
velvety appearance, which is due to the
fact that its surface is covered with
myriads of short, jointed, vertical fila-
ments, each of which bears one or more
conidia. The conidia, which fall off
readily, are produced until the latter part
of summer, when the filaments which
bear them shrivel up and disappear.

356. During the autumn asci are produced, but re-
quire the greater part of winter to come to perfection.
The asci grow in the cavities of minute papillae {peri-
thecia), and are intermingled with slender filaments
(paraphj'ses). Each ascus contains eight spores, which
eventually escai)e through an ai)ical pore. These spores
germinate by sending out a small filament, or sometimes
two.

357. No sexual organs have as yet been observed.
Possibly they exist in the dense tissues of the knot, and
fertilization may occur in the spring or early summer,
but they may have disappeared through the excessive
parasitism of these plants.

358. The parasitic filaments of each year's knot gener-

220 PHYLUM VII. CARPOMYCETEAE

ally penetrate downward some centimeters into the unin-
jured bark, and remain dormant there until the following
spring, when they begin the growth which results in the
production of a new knot, as described above.

359. To this order belongs the Ergot (Claviceps), a
common parasite upon heads of rye, and also many of
the black growths upon the bark and wood of trees.
Many species produce black spots upon living leaves,
wdiile many others occur upon dead leaves and twigs.

360. The Closed Fungi include a large number of
exceedingly injurious species; they often attack and
destroy not only plants, but also insects, upon which
their ravages are sometimes very great.

The Mildews (ORDER PERI SPORI ALES)

361. These plants, which are mainly parasitic, are
composed of branching septate filaments (hyphae) which
form a white or dark web-like film upon the surface of the
leaves and stems of their hosts. There are both sexual
and asexual spores, and of the latter there are in some
cases two or three different kinds, which are produced
earher than those that result from a fertilization.

362. In the Powdery Mildews (Family Erysiphaceae) ^
which are all parasitic, the jointed filaments closely

cover the leaves and other tender parts
of many plants, and draw nourishment
from them by means of suckers (hausto-
ria), w^hich project as irregular out-
growths from the side next to the epi-

^'"'o/Er^Tiphe'^'^ dermis. These suckers apply them-
selves closely to the epidermal cells, and

penetrate them.

363. The crossing and branching filaments soon send
up many vertical branches, which continue to form new

POWDERY MILDEWS 221

cells below by cross partitions. The cells thus formed are
at first oblong and cyhndrical, with flattened ends; but
the topmost ones soon become rounded at their extremi-
ties, thus giving rise to a row of cells, the spores, or
conidia. These fall off successively and germinate at once
by pushing out a tube, which gives rise to a new plant.

364. The sexual process (generation) in most species
takes place late in the season. Two
filaments crossing each other or coming
into close contact swell slightly and send
out from each a short branch; one of
these becomes the oogone, and the other
the antherid, both organs being very fig 104— Gcncm-

much reduced. tion of Erysiphaceae.

365. Fertilization is effected by the direct union of
protoplasm. Eight or ten branches then bud out below
the oogone, and growing upward soon completely enclose
it in a cellular coat which eventually becomes hardened
and turns brownish in color, constituting the spore-fruit
(perithecium).

366. The oogone inside of the perithecium gives rise,
by branching, to one or more large cells (young asci)
filled at first with granular protoplasm, which soon forms
two to eight spores (ascospores) , Upon its outer surface
the spore-fruit develops long filaments (known as
** appendages''), probably for holdfasts. In some genera
these terminate in hooks; in others they are dichotom-
ously branched; in still others, needle-shaped; while in
many species they end irregularly. The spore-fruits re-
main during the winter upon the fallen and decaying
leaves, and finally, by rupturing, permit the asci, with
the contained spores, to escape.

367. The Herbarium-mold (Aspergillus) is related to
the Mildews and belongs to the order of Little Tubers

222 PHYLUM VII. CARPOMYCETEAE

(AspERGiLLALEs). It is commoii on poorly dried speci-
mens in the herbarium, and also on moldy hay and decay-
ing vegetation generally. It sends up vertical branches,
which swell at the top and bear a great number of small
protuberances (the sterigmata) , each of which produces
a chain of conidia.

368. The sexual organs appear a little later than the
conidia. The end of a branch of the plant becomes

coiled into a hollow spiral which con-
stitutes the oogone. From below the
spiral an antherid grows upward, and
brings its apex into contact with the
upper cells of the oogone. After fer-
tilization other branches grow up
Fig. 105.— Aspergillus, arouud the oogouc, and finally com-
pletely enclose it, as in the Mildews,
described above. In the meantime from the cells of the
enclosed oogone branches bud out, and finally produce
many eight-spored asci on their extremities; later the
asci are dissolved, and the spore fruit, now of a sulphur-
yellow color, contains a multitude of loose spores.

369. The Blue Molds (species of Penicillium) are
related to Aspergillus. The conidial stage is a common
Blue Mold on decaying fruit and pastry. The sexual
organs resemble those of the herbarium-mold, and the
spore-fruit is a minute truffle-like body as large as a
coarse sand-grain.

370. Yeast-plants. A still greater degradation of the
sac-fungus type is reached in the minute plants which
occur in yeast. If a bit of yeast be placed upon a glass
slip and carefully examined under high powers of the
microscope, there will he seen very many small roundish
or oval cells, of a pale or whitish color. They have a
cell-wall, but generally the nucleus is indistinct. These

YEAST PLANTS 223

little cells are Yeast-plants, and bear the name of
Saccharomyces cerevisiae.

371. The}' reproduce l^y a kind of fission, called
"budding.'' Eacli cell ]nishes out a little projection
which grows larger and larger, and finally a cell-wall
forms between it and the old cell and these sooncT or
later separate from one another. Under
favorable circumstances certain cells form
spores internally, and these are now re-
garded as asci, homologous with the asci
of the higher sac-fungi. Yeast-plants are,
therefore, to be considered as greatly sim- Fig. iog.— Sac-
plified Sac-fungi, and they are members of ^ ^romyces.
the family Saccharomycetaceae (of the Order Hemi asc ales)
which has experienced what is probably the greatest
reduction suffered by any plants of the Ascosporeae,

372. Yeast-plants are saprophytes, and live upon the
starch of flour. They break up the starch, and in the
process liberate considerable quantities of carbon dioxide
which appears as bubbles upon the surface of the j^east.
Another result of the l^reaking up of the starch is the
formation of alcohol; hence the growth of yeast-plants in
a starchy substance is always accompanied by what is
known as alcoholic fermentation. The housewife and
baker use yeast-plants for the carbon dioxide gas which
they evolve, to give lightness to the bread, while the
brewer and distiller use the same plants for the alcohol
produced b}' their activity. (See Chapter IV, paragraph
139.)

373. The Truffles (Order Tuberales) are well known
from their large underground spore-fruits, which are
edible. Internally there are narrow tortuous channels
on whose walls asci develop, each containing a numl)er of
spores. Little is known of their round of life, and the

224 PHYLUM VII. CARPOMYCETEAE

sexual organs have not been discovered. The part of
the truffle that we eat is the large spore-fruit. These
are collected in Europe by experts and preserved for the
market, where they command high prices.

Laboratory Studies, (a) Collect fruiting specimens of the
common fruticosc lit-hcn (Usnca), which grows upon branches
of trees in forests. Make thin cross-sections of the stem, mount
in alcohol, afterward adding dilute potassium hydrate. Study
the filaments and their relation to the algae. Isolate some of
the algae by tapping on the cover-glass, and note their resem-
blance to Green Shme (Protococcus).

(6) Make thin vertical sections through one of the fruiting
disks, mount as above, and study asci, ascospores and para-
physes.

(c) Collect some of the small, flat, many-lobed hchens which
grow on the bark of apple-, maple-, and oak-trees, and which
have small blackish fruit-disks. Make careful sections of the
plant-body through the fruit-disks, and study the whole struc-
ture, ascospores, asci, paraphyses, filaments, and algae.

(d) Search for cup-shaped fungi, in the spring, about old
hot-beds and upon well-rotted barnyard-refuse. A common
cup fungus of an amber color often to be met with in such
localities is one of the best for the study of ascospores and asci.
Make very thin sections at right angles to the inner surface.

(e) Collect the bright red saucer-shaped cup-fungus {Sar-
coscypha coccinea) growing in the woods upon decaying sticks
and having a diameter of 1 to 4 centimeters. Make similar
sections.

(/) Collect a few Morels {Morchella esculenta), and make
sections at right angles to the surface of the pits which cover
the upper portion and examine for ascospores and asci.

(g) Collect fresh specimens of Plum Pockets, and preserve
them in alcohol. Study the fungus by making very thin
sections at right angles to the surface. Each ascus will be
found to contain several rounded ascospores.

(h) Collect Sht-fungi (Hystcrographium) on the bark of oak
or ash trees, or on dead twigs of sumach, and other shrubs.
The apothecia are black and carbonaceous, and are about a
millimeter long.

LABORATORY STUDIES 225

(i) In early summer examine the choke-cherry and plum
trees (wild and cultivated) for the 3'oung stages of Black Knot.
Watch the development until the knot becomes velvety in
appearance (about midsummer). Now make very thin cross-
sections of the knot and examine for conidia. The several
stages may be readily preserved in alcohol for future study.

(j) Late in autumn and in early winter examine the knots on
the same trees. Note the young perithecia, i.e. hollow paj)illae.
Make very thin vertical sections through some of these. No
perfect ascospores can be found at this time.

(k) Collect fresh knots in midwinter and make similar
examinations, when the asci and ascospores may be found.

(/) In the autumn collect a quantity of leaves of the lilac
which are covered with a whitish mold-like growth, the Lilac-
mildew (Microsphaera alni). Scrape off a bit of this Mildew
after moistening with a drop of alcohol; mount carefully,
adding a httle potassium hydrate. Look for conidia and
haustoria. Look also for spore-fruits, which appear like minute
dark dots to the naked eye. Carefully crush the spore-fruits
and observe the asci (four to seven) with their contained
ascospores (6). Note the beautifully branched tips of the
appendages.

(m) Collect and study the mildews to be found on hops
(Sphaerotheca castagnei), on cherry- and apple-leaves {Podo-
sphaera oxyacanthae) , on hazel- and ironwood-leaves (Phyl-
lactinia suffulta), on willow-leaves {Uncinula salicis), on leaves
and fruit of grapes {U. necator), on wild sunflowers, verbenas,
etc. (Erysiphe cichoraccanun) , on peas, grass, anemones,
buttercups, etc. {E. comynunis).

(n) Place a few shps of green twigs in an ordinary plant-press,
allowing them to remain until they become (1) moldy (conidial
state), and (2) covered with minute yellow globular bodies (the
spore-fruits) . These are known as the Herbarium-mold (.1 spcr-
gillus herhariorum) . Study as in the case of the Mildews.
This can frequently be obtained by placing a piece of almost
dry bread under a bell jar for a few days.

(o) Blue Mold may be obtained from decaying fruit, pas-
try, etc.

(p) Place a minute piece of "compressed" yeast upon a glass
sHde, add a little water, cover with a cover-glass, tapping it
down gently. After a short examination under a high power of

226 PHYLUM VII. CARPOMYCETEAE

the microscope add iodine, which will stain the starch-grains
blue or purple, and the yeast-plants j^ellowish. Alany of the
latter will be found in process of budding.

(q) Repeat experiment q on page 103 for production of
carbon dioxide by yeast.

(?') Spread a little ''compressed" yeast on a fresh-cut shce
of potato or carrot; cover with a tumbler or l^ell-jar to kee]:) it
moist; after a few daj^s (four to eight) examine for cells which
are producing ascospores.

(s) Commercial Truffles are natives of Europe, but they may
be obtained for study in our markets. Make thin cross-
sections of the large spore-fruit and examine the ascospores and
asci.

Class 15. BASIDIO SPORE AE

The Basidium Fungi

374, The plants, or rather the fruits, of this class are
among the largest and most conspicuous of the fungi.
They are mostly saprophytes whose abundant vegetative
filaments {viycelium) ramify through the nourishing sub-
stance, and afterw^ard give rise to the conspicuous spore
fruits. The spores are produced usually in 4's upon
slender outgrowths from the ends of enlarged cells {ha-
sidia), the latter usually arranged parallel to each other
so as to form a spore-bearing surface Qiymenium) , which
may be external (as in Toadstools) or
internal (as in Puff-balls).

375. The basidia in this class are
here regarded as homologous wdth the
asci of the Ascosporeae. The differ-
ence between them is that in the asci
mento?''bI^Sia''a°nd the sporcs iu their development remain
basidiospores. inside of the ascus cavity, while in the

basidia the spores as they develop push out so as finally
to become external. It is obvious that the ascus is the

PUFF BALLS 227

more primitive structure, and that the basidium is a
hiter and a higher structure, probabl}^ derived from it.

376. There are about 14,000 species, which may be
separated into nine orders, and about twenty-five fami-
lies. A few only of these will be taken up here.

377. The lowest of the Basidium-fungi, the False
Tubers (Order Hymenogastrales) are subterranean
plants, with subterranean truffle-like, fleshy fruits, which
like the truffles are edible and wholesome. They are
distinguished from the truffles by the fact that they con-
tain basidia instead of asci.

378. The Pufif-balls (Order Lycoperdales). The
plants of this order are saprophj^tes, whose spore fruits
are often of large size, and usually more or less globular in
form. The basidiospores are always borne in the in-
terior of more or less regular cavities, and from these they
escape by the deliquescence, and subsequent drying and
rupture of the surrounding tissues.

379. The vegetative filaments of Puff-balls penetrate
the substance of decaying wood, and the soil filled with
decaying organic matter. They
usually aggregate themselves into
cylindrical root-like masses. After
an extended vegetative period the
filaments produce upon their root- fig. los.— Puff-haii and
like portions small rounded bodies, basidiospores.

the young spore fruits, which increase rapidly in size and
assume the forms characteristic of the different genera.

380. No sexual organs have yet been discovered, but
analogy points to their possible existence upon the vege-
tative filaments just previous to the first appearance of
the spore fruits. The spore fruits are composed of inter-
laced filaments loosely arranged in the interior, and an
external more compact limitary tissue forming a rind

228 PHYLUM VII. CARPOMYCETEAE

(peridium) . The basidia develop in a portion of the in-
terior (the gleba), the remainder being sterile.

381. Many common puff-balls belong to the genus
Lycoperdon, the type of the family Ly coper daceae, of
which there are a good many species. The genus Cal-
vatia contains the Giant Puff-ball (C. maxima), whose
spore fruit is sometimes 30 centimeters or more in diam-
eter. Here it must be remembered that the proper plant
lives underground, obtaining its food from decaying vege-
table matter, while the great ball is a fruit containing
basidia and basidiospores.

382. The Bird-nest fungi (Order Nidulariales) are
so noticeable that they should be examined here. These
little fruits usually grow on twigs and sticks, and are
closed at first, and then open and cup shaped. They are
a centimeter or less in height and width, and when mature
contain several small brownish spore packets (the ''eggs''
of the little *' nests"). When young these *'eggs" are
small cavities lined with basidia and surrounded by a
dense layer of hyphae. When the tissues about them
deliquesce these spore-bearing cavities persist as hard
walled bodies.

Fig. 109. — Development Fig. 110. — Development

of bird-nest fungi. of stinkhorn.

383. The Stink -horns (Order Phallales) live as sap-
rophytes, feeding upon decaying organic matter in the
ground, or less frequently as parasites in the roots of
various plants, eventually developing globose subterra-
nean fruits. These fruits produce their spores in a circu-

TOADSTOOLS 229

lar layer, and when mature become ruptured by the rapid
growth of their central tissues, resulting in the formation
of a stalk which carries up the slimy mass of spores to
some distance above the ground. The intolerable odor
of most of the species has earned for them their inelegant
but quite appropriate common name.

384. The Toadstools (Order Agaricales). The fruits
of these plants in some respects are the highest of the
Carpomj'ceteae. They are not only of considerable size
(ranging from 1 to 20 centimeters, or more, in height),
but their structural complexity is so much greater than
that of the other orders that they must be regarded as the
highest of the fungi. Like the Puff-balls, they produce
an abundance of vegetative filaments (mycelium) under-
ground or in the substance of decaying wood. These
filaments are loosely interwoven, becoming in some cases
densely felted into tough masses or compacted into root-
like forms. While mostly saprophytic some appear to be
parasitic, especially on the woody tissue of trees which are
rotted by them. Sooner or later these underground
filaments produce the spore fruits, which are mostly
umbrella-shaped, as in common Toadstools and Mush-
rooms, or of various more or less irregular shapes, as in
the Pore fungi, Coral fungi, etc.

385. The Mushrooms of the markets (Agaricus cam-
pcstris) so connnonly cultivated by gardeners, may illus-
trate the mode of development of the Toadstools (Family
Agaricaceac). The vegetative filaments compose the so-
called ''spawn" which grows through the decaying matter
from which it derives its nourishment. Upon this at
length little rounded masses of filaments arise, which be-
come larger and larger and are the young fruits. The
circular spore-bearing layer is first internal and su])ter-
ranean as in the Stink-horns, but it is brought above

230 PHYLU.M VII. CARPO^IYCETEAE

ground by tlie rapid growth of a central mass of stalk
tissue, and later by a rupture of tissues the hymenium be-
comes external.

386. At maturity the spore fruit of the Mushroom
consists of a short thick stalk, bearing an expanded um-
brella-shaped cap, beneath which
are many thin radiating plates, the
gills. Each gill is a mass of fila-
ments whose enlarged end-cells
(basidia) come to, and completely

Fig. 111. -Development of covcr, both of its surfaccs. The

mushroom. basidla produce spores in the usual

manner for plants of this class, that is, upon slender stalks.

387. In the Pore fungi (Polyporaceae) the basidia line
the sides of pores; in the Prickly Fungi (Hydnaceae) and
Coral fungi (Clavariaceae) they cover the surface of spines
and branches; while in the Leathery fungi (Thelephora-
ceae, Stereum, etc.) they form a smooth surface.

388. Nothing is yet known as to their sexual organs.
Several botanists have described such supposed organs
upon the vegetative filaments before the formation of the
spore fruit, but there are grave doubts as to the correct-
ness of the observations, and it is the general opinion that
these organs have become obsolete.

389. The vegetative filaments (mycelium) of some
species of this order (as Foines fovientariiis, etc.) often
form thick, tough, whitish masses of considerable extent
in trees and logs.

390. We know but little as to the germination of the
spores and the subsequent development of the vegetative
filaments.

391. Several families of more or less reduced basidium
fungi which probably have been derived from the fore-
going families, as the Ear Fungi (Auriculariales) , Jelly

LAHOUATORV STUDIES 2:U

Fungi (Tremellales) and the ytill more reduced Exoha-
sidiales are probably to be placed here.

Laboratory Studies, (a) Collect specimens of puff-balls in
various stages of growth. IMake very thin sections of the young
spore fruit, and look for the cavities lined with spore-bearing
cells (basidia).

(b) JMount in alcohol some of the dust which escapes from a
dry iniff-ball. Examine with a high power, and note the spores
and fragments of brokcn-up filaments.

(c) Dig up tiie earth under a cluster of young i)ufT-balls, and
observe the vegetative filaments. Examine some of these
filaments under the microscope.

(d) In the summer look for Earth Stars (Geaster) in which
the outer peridium is rolled back (open) when wet, and closed
when dry.

(e) Stalked Puff-balls (Tylostoma) may often he found witli
a stallv 3 to 10 or more centimeters long holding the spore
cavit}' aloft.

(/) Look for Bird-nest fungi in fruit on sticks and twigs on
damp ground. Note that when j^oung the fruits are closed
and solid, and that as they become older much of the internal
tissue deliquesces, leaving the little egg-like spore packets.

(g) Collect specimens of Stink-horns in various stages of
development and preserve in formalin. Make vertical sections
of the immature (globose) spore fruit and note the circular
spore layer. Study the basidia and basidiospores under a
high power.

(h) Collect a few toadstools in various stages of development,
securing at the same time some of the subterranean vegetative
filaments. Note the appearance of the young spore fruits,
and how they develop into the mature toadstool.

(0 Select a mature (but not old) spore fruit with dark-
colored spores, cut away the stem, and place the top (pileus)
on a sheet of white paper, with the gills down. In a few hours
many spores will be found to have dropi)ed from the gills uj)on
tlic paper; these are the so-called "spore-prints".

(j) Examine the minute structure of various parts of tiie
spore fruit and the vegetative fdaments, and ol)servo that tiiey
are composcnl of rows of cylindrical colorless oolis joiiunl end to
end.

232 PHYLU:M VII. CARPOMYCETEAE

(k) Make very thin cross-sections of several of the gills and
carefully mount in water or alcohol. Note the layer of spore-
bearing cells (hymenium), with basidiospores borne upon little
stalks.

(/) Examine the pores of fresh polypores in transection,
looking for the basidia and basidiospores in the pores.

(w) In like manner make transections of Prickly Fungi,
Coral Fungi, and Leathery Fungi, but in these look for basid-
iospores on the outer surface of the sections.

Class 16. TELIOSPOREAE. The Brand-Fungi

392. Here are collected a considerable number (4200
species) of extremely parasitic fungi, certainly related to
the fungi of the two preceding classes. On account of
their excessive parasitism they are structurally much re-
duced and degraded and this has served to hide their true
relationship.

393. The plant body consists of branching septate
filaments which run through the green tissues of higher
plants, eventually producing usually erumpent spore
clusters (sori), but no definite spore fruits (perithecia, or
apothecia). Conidia of one or two kinds are usually
present, and precede the formation of teliospores.

394. The Rusts (Order Uredinales) are minute,
parasitic, greatly degraded fungi
which grow in the tissues of higher
plants.

395. A common Wheat rust
{Puccinia graminis) may be taken
oraeciospores and pycnio- as au illustratiou of the ordcr. It
is common wherever wheat is
grown, and often greatly injures and sometimes entirely
destroys the crop. Its round of life shows four well-
marked stages, as follows: (I) In the spring clusters of
minute yellowish cups occur on the leaves of the

WHEAT RUST 233

BarbciT}'. These cups are at first internal rounded
bodies, in which spores (conidia) develop in chains,
at length bursting through the lower epidermis. The
spores quickly drop out and are carried away by the
winds. This stage is known as the cluster-cup stage,
and the spores as aecidiospores, or aeciospores.

396. Associated with this cluster-cup stage there are
usually flask-shaped structures known as spermogones or
pycnia, in which minute spores or spore-like bodies
(pycniospores) are produced. They resemble the struc-
tures which produce sperms in the Disk Lichens. If
they have a similar function in the rusts it has not yet
been demonstrated.

397. (II) The aeciospores falling upon a wheat plant
germinate there and penetrate its tissues, through the
stomata, sending haustoria into the cells. After a few
days, if the weather has been favorable, the parasite has
grown sufficiently to begin the formation of large red-
dish spores (uredospores, or urediniospores) just beneath
the epidermis, which is soon ruptured, exposing the
spores in reddish lines or spots upon the stems and leaf
sheaths. This is the Red-rust stage, so common before
wheat-harvest. These red spores fall easily, and quickly
germinate on wheat again, producing
more Red rust, and so rapidly increasing
the parasite.

398. (Ill) Somewhat later in the season
the parasitic filaments which have been
producing Red-rust spores begin to pro- fig. 113— uredo-
duce the dark-colored, thick-walled, l^nd'sporidsi""^"'^'
2-spored bodies characteristic of the

Black Rust. Each 2-spored body consists of a contin-
uous wall tightly enclosing the two spores, here called
*'teliospores." Being thick-walled, these spores endure

234 PHYLUM VII. CARPOMYCETEAE

the winter without injury, antl when spring comes (IV)
they germinate on the rotting straw forming a 4-celled
**promyceHum" and producing several (usually four)
minute spores, called sporids. This is the fourth and
last stage of the rust. Such sporids as fall upon
Barberry-leaves germinate, and enter directly through
the epidermis, giving rise to cluster cups again.

399. These stages (I, II, III) are so different in appear-
ance that for a long time they were regarded as distinct
plants, and received different names. Thus the first
stage was classified as a species of Aecidium, the second
as a species of Uredo, and the third as a Puccinia. We
still preserve these names by sometim.es calling the spores
of the first aecidiospores (or aeciospores) and of the second
uredospores (or urediniospores), while the third name is
retained as the scientific name of the genus.

400. For a long time many botanists did not believe
the statement that this Wheat rust lives for a part of its
life upon one host (barberry), and later upon another
(wheat), but now this fact (known as ''heteroecism") is
well established not only for Wheat rust, but also for
many other species.

401. The sporids cannot ordiiiarily produce rust
directly upon wheat, probably because of the toughness
of the epidermis; but it has been claimed (by Plowright)
that when sporids germinate upon very young leaves of
wheat-seedlings they penetrate the epidermis and then
soon give rise to a red-rust stage. In such cases the
cluster-cup stage is omitted. Possibly the rusts upon
the spring wheat, oats, and barley in the Mississippi
Valley and on the Great Plains where barberry is rare
are sometimes propagated in this way. It has been
shown also that on the Great Plains the red rust lives
through the winter on the little wheat plants, and that

SEXUALITY OF RUSTS 235

its spores blow to the north in the spring from field to
field, and back to the south in the autumn. Probably
this is the more common mode of propagation upon the
Plains. Recently it has been found also that teliosporcs
occur on and in wheat kernels, and it is thought that
young plants may be infected directly from these.

402. There are many kinds of rusts, distinguished
mainly by their teliospores, which are single (Uromyces
and Melampsora), in twos (Puccinia and Gymnospor-
angium), or several (Phragmidium). In many species
the round of life is similar to that in the Wheat rust
described above (heteroecious), the hosts, however, being
different, but in others there appears to be a constant
omission of certain stages. Moreover, in many species
all the stages develop upon the same host plant (autoe-
cious).

403. Cell fusions which are now regarded as having
a sexual significance, and whose ultimate result is the
production of teUospores, have been observed in the
mycelium of some of the rusts. The simple sexual or-
gans (usually end cells of adjacent filaments) coalesce into
binucleate cells, which develop short hyphae of cells also
binucleate. In some cases these produce directly one
or more teliospores; in others one or two additional spore
forms are intercalated as aeciospores and uredospores.
Thus we may have either aecia or uredinia or both form-
ing as the first result of the sexual act, but in any event
the ultimate result is the production of teliospores.
Accordingly these several spore forms are all primarily
binuclcated, but the two nuclei unite early in the young
teliospore, and therefore the promycelial cells and sporids
are uninucleate.

404. The Smuts (Order Ustilaginales). The i^lants
which compose this order are all parasites living in the

236 PHYLU:^! VII. CARPOMYCETEAE

tissues of Flowering Plants. Like the Rusts, they send
their parasitic threads through the tissues of their hosts,
and afterward produce spores in great abundance which
usually burst through the epidermis.
There is a still greater structural degra-
dation in the plants of the present order
than in the Rusts, probably due to their
excessive parasitism.
Fig. ii4.-TeUo- 405. The parasitic threads of the

spore and sponds. *^

Smuts are well defined, and consist of
thick-walled, cellular, branching filaments, which are
generally of very irregular shape. They grow in the
intercellular spaces and cell cavities of their hosts, and
some send out suckers {haustoria), which penetrate the
adjacent cells much as in the Mildews. The parasite
generally begins its growth when the host plant is
quite young (meristematic) and grows with it, spreading
into its branches as they form, until it reaches the place
of spore-formation. In perennial plants the parasite
may be perennial, reappearing year after year upon the
same stems, or upon the new stems grown from the same
roots; in annuals it must obtain a foot-hold in the young
plants as they grow in the spring.

406. The life history of the Smuts has been made out
for but few species. Three kinds of spores (conidia,
teliospores and sporids) have been observed in many
species, and their germination has been carefully studied,
but the sexual organs (if any exist) have not yet been
discovered.

407. The Smut of Indian corn (Ustilago maydis) is
very common in autumn. The parasitic filaments are
found in various parts of the host, and at last those which
reach the young kernels or other succulent parts become
semi-gelatinous and form spores internally. There is

SMUTS 237

much crowding and distortion of these soft-walled spore-
l)earing fihunents, but here and there this structure may
be made out. When the spores are ripe, the gelatinous
walls dissolve and, the watery portions evaporating,
leave a dust}' mass of black spores. The spores germinate
by sending out a short septate filament (promycelium)
upon which minute sporids are formed laterally, much
as in the Wheat rust. Like other smuts, that of Corn
is capable of growing as a saprophyte in the deca3'ing
vegetable matter of the soil, producing an abundance of
conidia. It has been found that when the sporids or the
conidia germinate upon the meristematic parts of the
growing plant or the projecting styles of the developing
ears the}^ penetrate the surface layers, and thus secure
admission to the tissues of their host.

408. Other Smuts, as Wheat smut or Black Blast
{Ustilago tritici) of wheat, Oat smut {U. avenae), Barley
smut ([/. hordei), etc., have a structure and mode of devel-
opment closely resembling the foregoing, but with most of
these the hosts can be infected only when very young, i.e.
during or shortly after germination, or through their
stigmas at the time of flowering.

409. The Bunt or Stinking smut of wheat {Tilletia
tritici and T. foelens) represent an allied family {Tille-
tiaceae) in which the sporids are formed in a whorl at the
end of the non-septate promycelium.

Laboratory Studies, (a) Collect specimens of cluster cups
(from barberry, l)uttercups, or cvenin<j; i)riniroses, etc.); ex-
amine first under a low power without niakinfj; sections. Note
the cups filled with yellowish or orange conidia (aeciospores).
Note spermogones (minute dark spots) generally on the opposite
side of the leaf.

(6) Make very thin cross-sections through a mass of cups so
as to obtain vertical sections of the cups and the spermogones.

(r) In May, Juno or July collect leaves of wheat, oats, or

238 PHYLU.M VII. CARPOMYCETEAE

barley, bearing lines or spots of Red rust. First examine a
few of the spores mounted in alcohol, with the subsequent
addition of a little potassium hydrate. Then make very thin
cross-sections thi-ough a rust si)ot, and mount as before, so as
to see the parasitic filaments in the leaf, bearing the Red-rust
spores upon little stalks.

(d) In July, August, or September collect stems of wheat,
oats, or barley bearing lines or spots of Black rust. Study the
teliospores as above, and afterward make cross-sections also.

(e) In early spring collect and examine the Black rust on
wet stems of rotting straw. Look for germinating tehospores
and sporids, which sometimes may be found.

(/) Examine microscopically the gelatinous prolongations on
"cedar-apples," and observe the teliospores, which resemble
those of Wheat rust. *' Cedar-apples," which are common in
the spring on red-cedar twigs, are in reality species of rust of
the genus Gymnosporangium. Their cluster cups occur on
apple leaves. Uredospores are lacking.

(g) Collect smutted ears of Indian corn. Mount a little of
the black internal mass in alcohol, followed by weak potassium
hydrate and observe the spores.

(h) Make very thin slices of young fresh or preserved speci-
mens and examine for parasitic and spore-bearing filaments.
The outer tissues of the distorted kernels are generally best.

(i) Make similar studies of the smuts of wheat, oats, or
barley, which may be collected in June, or about the time of the
"heading" of the grain.

(j) Make hanging-drop cultures (in water) of the teliospores
of Tilletia and Ustilago, and compare their germination.

The Imperfect Fungi

410. There are many fungi (about 16,000 species), in
some respects resembling the Ascus Fungi (Ascosporeae),
of which we know only the conidial stages. They have
been brought together temporarily in three orders under
the general name of ''Imperfect F^ungi."

411. The Spot Fungi (Order Sphaeropsidales) are
mostly parasitic on leaves and fruits of higher plants,

IMPERFECT FUNGI 239

producing whitish or discolored spots, and eventually
developing small perithecia-like structures (pycnidia)
containing conidia. Species of Phyllosticta are common
on leaves of Virginia creeper, wild grape, cottonwood,
willow, pansy, peach, apple, wild cherry, elm, etc., while
species of Septoria are to be found on leaves of box-elder,
aster, thistle, evening primrose, wild lettuce, plum,
elder, etc.

412. The Black-dot Fungi (Order Melanconiales)
differ from the preceding mainly in the absence of a
distinct perithecium, the spores developing beneath the
epidermis of the host and ])ursting through so as to form

Fig. 115. — Septoria. Fig. 116. — Fig. 117. — Cercospora.

Gloeosporiuni.

small dark-colored or black dots (acervuli). Species of
Gloeosporium and Melanconium are common on leaves,
fruits, and twigs.

413. In the Molds (Order ]Moniliales) the conidia-
bearing threads emerge through the stomata of the host,
or grow out through the outer decaying tissues, forming
moldy patches or masses. Here are many common
parasites (e.g. species of Ramularia, Cercospora, Fusi-
cladium) and saprophytes (Monilia, Botrytis, etc.), some
of which are l)otli parasitic and saprophytic.

Laboratory Studies. Altliou«2;h the Imperfect Fungi are
quite too diliicuh lor the beginner to do much with, it is well
that he should become somewhat familiar with their general
appearance; accordingly a few studies are suggested.

240 PHYLU.M VII. CARPOMYCETEAE

(a) Look for Spot Fungi on the hosts mentioned above, and
especially for the minute black fruits in the spots, making
sections of the latter.

(b) Look for Black-dot Fungi on leaves, fruits and twigs of
many plants, especially for Colletotrichum on bean pods.

414. Summary for the Higher Fungi. The theory
underlying the foregoing account of the Higher Fungi is
that these plants have been derived from the Red Algae
by modifications, mostly degradational, due to the change
from a holophytic to a hysterophytic habit, accompanied
by the equally significant change from aquatic to non-
aquatic life. It is here considered probable that the
earliest fungi were those known as 'lichens," which
became parasitic upon small algae. In them the dom-
inant modification was, of course, the disappearance of
chlorophyll, and the reduction of the plant body. In
the fruit resulting from the fertiUzation of the egg, the
homologues of the carpospores of the Red Algae divided
internally into spores, thus changing the carpospore
into the ascus, and resulting in the considerable multi-
plication of spores. Thus the asci and ascospores be-
came characteristic structures in the fruits of the fungi,
and gave name to the first class — Ascosporeae.

415. Later, in the subterranean fruits of the truffles
another modification took place whereby the spores
instead of remaining within the ascus, push out beyond
the ascus wall, so as to be more easily dispersed. In
this way the basidium with its basidiospores arose from
the ascus and its ascospores. These are thus to be re-
garded as homologous structures, in which the later-
formed basidia have superior means for dispersing their
spores.

416. In like manner in the Brand Fungi we find

PHYLOGENY OF FUNGI 241

teliospores instead of the homologous ascospores or
basidiospores, and in these plants the fruit body has
become so reduced as to be scarcely recognizable as such.
The excessive parasitism of these plants may account for
their physical degeneration. As to the origin of the
Brand Fungi it is probable that they came off from the
parasitic Ascosporeao rather early in the phyletic history,
and a possible relationship is here suggested with the
Exoascales, and the Phacidiales.

417. The Imperfect Fungi are thought to be mainly
Ascosporeae that may have lost their ascospores through
excessive degeneration. It is probable, however, that
many of them are the conidial stages of Ascosporeae and
Basidiosporeae whose relationship is not yet recognized.
In recent years many conidial forms hitherto placed here
have been found to belong to well known ascigerous
fungi.

LITERATURE OF CARPOMYCETEAE

F. E. Clements, The Genera of Fungi, Minneapolis, 1909.
P. A. Saccardo, Sylloge Fungorum, Vols. I to XXII, 1882-1913.
These are comiDrehensive works; the following include certain
portions of the Higher Fungi.
J. B. Ellis and B. M. Everhart, North American Pyrenomy-

cetes, Newfield, 1892.
Bruce Fixk, Lichens of Minnesota, Washington, 1910.
Albert Schneider, A Text-hook of Lichenulogy, Binghainton,

1897.
L. M. Underwood, Molds, Mildews and Mushrooms, Xew

York, 1899.
C. B. Plowrioiit, .1 Monograph of the British Uredineae and
Ustilagincaea, London, 1889.

CHAPTER XIV

PHYLUM VIII. BRYOPHYTA

THE MOSSWORTS

418. This phylum includes plants of much greater
complexity than any of the preceding. In very many
cases they have distinct stems and leaves, whose tissues
often show a differentiation into several varieties. In
the sexual organs the cell to be fertilized (the egg) is from
the first enclosed in a protective layer of cells, and after
fertilization it develops into a complex spore-bearing
body.

419. The life-cycle of the Mossworts includes a dis-
tinct alternation of generations. The immediate prod-
uct of the fertilization of an egg is not a thalloid or leafy
plant Uke that which bears the sexual organs, but, on the
contrary, it is a many-celled leafless structure, spherical
or approximately cylindrical, which eventually produces
spores internally. The plant which produces the sexual
organs is the gametophyte, while that which produces the
spores is the sporophyte.

420. So the Mossworts have a marked duality, and we
must consider both phases when we wish to get a complete
idea of any particular plant. This duality has permitted
the acquisition of the land habit, since the gametophytes
have retained some of their aquatic characteristics, while
the sporophytes have become modified for a terrestrial
life. Accordingly in Bryophytes we find the beginning of
the terrestrial habit in green plants.

242

ALTERNATION OF GENERATIONS 243

421. Mossworts may then be described as green plants
in which the gametophyte is a prostrate or erect some-
what long-Hvcd phint, producing antherids, and oogones
(the latter enclosed in archegones). After fertilization a
distinct structure, the sporophyte, is produced, but al-
though it rests on and in the gametophyte and obtains its
supply of water and much of its food from it there is
no organic connection between them. In this sporo-
phyte certain internal cells (the ''spore mother-cells")
divide twice and thus produce internally four spores
each. These eventually germinate and produce other
gametophytes.

422. Here it should be noted that the nuclei of the
gametophyte cells contain a definite number of chromo-
somes, and that on the fertilization of the egg this number
is doubled. This double number is maintained in the
sporophyte until spores are formed by division into fours,
at which time a reduction takes place to the original num-
ber. So in this phylum the two generations are separable
also by their chromosome numbers in addition to the
other more obvious differences.

423. The antherids are complex structures. They are
usually short-stalked, and consist of a layer of large
])Oundary cells within which are very numerous, small,
more or less cu])ical cells, each of which produces in-
ternally an elongated, more or less spiral, biciliate sperm.
The walls of these spermatogenous cells dissolve, leaving
the sperms free within the cavity of the antherid. By the
rupture of the apical cells the sperms escape. This
occurs only when the antherid is covered with water (rain,
dew, etc.).

424. The archegone is a flask-shaped, elongated organ,
consisting of an enlarged lower part (venter) containing
the egg, aljove which is the slender neck, at first closed at

244 PHYLUM VIII. BRYOPHYTA

the top and surrounding the row of canal cells, but later
open with a continuous passage to the egg (owing to the
dissolution of the canal cells). In fertilization which
takes place in water, the sperms pass down the tubular
neck to the egg below.

425. Mossworts are of small size,- rarely exceeding 10 or
15 centimeters in height. They generally prefer moist
situations upon the ground, or on the sides of trees or
rocks. All told there are somewhat more than 16,000
species. Two classes may be distinguished, as follows:

Mostly bilateral, often thalloid, creeping gametophytes,
usually with splitting sporophytes, and mostly having
elaters Class Hepaticae.

Multilateral, leafy -stemmed, mostly erect gametophytes, usu-
ally with circularly dehiscing sporophytes, and without
elaters Class IMusci.

Class HEPATICAE. Liverworts

426. In the lower Liverworts the gametophy te is a flat,
expanded thallus of parenchymatous tissue, and this
gradually differentiates into a leafy stem as we pass to
the higher forms, but in all cases the plant body has two
distinct and well-marked surfaces, an upper and an under
one, the latter bearing the root-hairs (rhizoids) by which
the plant is fixed to the ground. About 4000 species are
known.

427. Among the simplest of the Liverworts are the
little round, flat Riccias (Riccia) which grow on wet earth
or even float on the water. In the upper surface of the
loose green tissue are the sunken antherids which pro-
duce biciliated spiral sperms. In a similar manner the
archegones are sunken in the upper surface. After fer-
tilization the egg develops into a globose cellular body

HORXWORTS

245

(the sporophyte), whose interior cells divide into spores,
hut there are no " elaters." Although still surrounded by
the distended archegone this sporophyte is not organically
connected with any part of the gametophyte. The spores
escape by the decay of the surrounding layers of cells, and
on germination give rise to gametophytes like that with
which we started.

428. In the Horn worts (Anthoceros) the gametophyte
is a thin thallus of somewhat more compact tissue than
in Riccia, and growing on moist earth. The antherids

Fig. lis.— Rice

Fig. 119.

Anthoceros.

and archegones are sunken in the upper surface, and
resemble those of Riccia. When fertiUzed the egg de-
velops into an elongated, cylindrical sporophyte whose
upper part emerges from the neck of the archegone,
while the enlarged base remains seated in the venter.
The sporophyte is made up of a considerable mass of
green tissue, and is surrounded by an epidermis which is
suppUed with stomata like those of higher plants. This
the first appearance of true stomata in the Vegetable
Kingdom.

429. The lower part of the sporophyte continues to
grow in length indefinitely. Internally there is a layer
of cells by the division of which spores are formed, and
intermingled with these spores are the elongated sterile
cells called ''elaters. '' As the spores ripen above the
sporophyte splits from the top to permit their escape.

246

PHYLUAI VIII. BRYOPHYTA

Fig. 120. — Marchantia,
brood-masses (gemmae).

On germination the spores produce gametophytes like
the originals.

430. The verj^ conspicuous Great Liverwort (Mar-
chantia) is common on moist ground and is frequently
abundant in green houses. Its gametophyte is a large,
flat, branching, thalloid plant with a distinct midrib.
Its epidermis is pierced with circular, many-celled

''stomata" which open into large
air cavities supplied with many
green cells. Here and there on the
upper surface are cups containing
hairs whose terminal cells develop
into green masses (brood masses, or
gemmae) which fall off and quickly
develop into new gametophytes. This is thus an asex-
ual mode of reproduction, and these brood masses take
the place of the zoospores, tetraspores,
and conidia of lower plants.

431. The antherids are confined to par-
ticular portions of the gametophyte (an-
theridial disks) which are raised on short
stalks. Here they are sunken in the sur-
face and they and the sperms resemble
those of Riccia and Anthoceros.

432. The archegones are also confined to particular
portions of the gametophyte (known as '^ receptacles"

but really lobed disks) which are raised
on more or less elongated stalks (arche-
gonial branches). The archegones are
dependent from the under side of the re-
ceptacle. When fertilized the egg de-
velops into a globose, shortly stalked
sporophyte containing spores and elon-
gated sterile cells, the "elaters," whose walls are spirally

Fig. 121.— March-
antia (antherids).

Fig. 122.— March
antia (archegones)

SCALE MOSSES 247

thickened. By the expansive force of these elaters
the sporophyte is ruptured somewhat stellately, and the
spores are forced out. When the spores germinate they
give rise directly to the f!;ametophyte generation.

433. The Scale mosses (Order Jungermanniales)
are the highest of the Liverworts, and also the most
numerous in species. In the lower family {Metz-
gcriaccae) the gametophyte is usually a thal-
lus as in the liverworts already described,
but in the higher family {J linger manniaceae)
it is a creeping, leafy stem. In the first
f amity w^e find all gradations from the en- p^^ 12.3 —
tire margined thallus to those with more and- Metzgeria, and

^ Jungermanma.

more pronounced lateral lobing, and finally
to those in which the lobes have become distinct leaves
on a rounded stem. The leaves of Scale mosses are
but one cell thick and are not ribbed.

434. The antherids and archegones are borne dorsally
or subterminally and are much like those already
described. The sporophyte develops a slender stalk
which carries up the enlarged spore case, and the latter
when the spores are mature splits vertically into four
segments and permits the escape of spores and elaters.
When the spores germinate they may develop directly
such adult gametophytes as are described above, while
in the higher forms the gametophyte is first a filamentous
or thalloid structure ('^protonema") from which tlie
adult gametophyte subsequentl}^ buds out.

435. ALmy Scale mosses reproduce by means of l^rood
masses much like those of Marchantia, or even simple,
single-celled structures (brood cells).

436. Scale mosses have no stomata on either gameto-
phytes or sporophytes.

248 PHYLUM VIII. BRYOPHYTA

Laboratory Studies, (a) Look for Riccias on the wet
ground by the sides of ponds and slow streams from midsummer
to fall. Make careful vertical sections for structure of the
gametophyte, at the same time looking for the sexual organs
and the imbedded sporophyte.

(b) Study Anthoceros for gametophyte, and cylindrical spor-
ophj'tes. In the latter find stomata, spores and simple elaters.
Anthoceros may be obtained from the South (Gulf states) for
study in early spring.

(c) Collect specimens of the Great Liverwort (Marchantia)
which may be found in fruit in midsummer. Note that one
plant produces the antheridial branches, which have flat disks,
and another produces the archegonial branches, which have
lobed disks (''receptacles"). Note the cups, with contained
brood masses (gemmae).

(d) Examine the upper surface of a plant with a low power
of the microscope, and note the round ''stomata." Next strip
off some of the epidermis, mount in alcohol, and study with a
high power.

(e) Make longitudinal sections . of the plant through its
thickened central rib, and observe the elongated cells, with
foreshadow fibro-vascular bundles.

(/) Make vertical sections of the antheridial disk, mount in
water, and study the antherids. By repeated trials sperms
also may be seen.

(g) Make similar sections of the archegonial disk, and study
archegones. By taking older specimens the sporophytes,
spores, a<nd elaters may be studied. For the latter, mount in
alcohol and afterward add a little potassium hydrate.

(h) Examine the bark of trees for small brownish Scale
mosses. Mount a bit of one in alcohol, afterward adding potas-
sium hydrate, and study for structure of the gametophyte.
In the spring the minute splitting spore cases may readily be
found.

Class MUSCI. Mosses

437. The gametophyte in this class is a leafy multi-
lateral stem, rarely bilateral. It is fixed to the soil or
other support by root-hairs (rhizoids) which grow out
from the sides of the stem. The leaves are usually

MOSSES 249

composed of a single layer of cells, and in many cases have
a midrib. The sporophyte is more or less elongated,
enlarged above into a spore-case (capsule) and does not
contain claters.

438. The tissues of the Mosses present a considerable
advance upon those of the Liverworts. In the stem
there is frequently a bundle of very narrow thin-walled
cells, which in some species become considerably thick-
ened. In a few cases there have been observed bundles
of thin-walled cells extending from the leaves to the
bundles in the stem. It cannot be doubted, then, that
the Mosses possess rudimentary fibro-vascular bundles.
As in liverworts, the tissues of mosses develop from
a single apical cell. Breathing-pores (stomata) re-
sembling those of the higher plants occur on the sporo-
phytes; they are not found upon the leaves or stems.

439. Mosses, for the most part, grow upon moist
earth or rocks, or upon the trunks and branches of
trees; comparatively few are
aquatic. They range in size from
less than a millimeter to many
centimeters in length, the most
common height being from 2 to 4
centimeters. They are all chlo- fig. 124.-A moss (protonema
rophyll-bearing plants, and are and leafy gamctophyte).

generally of a bright green color; occasionally, however,
they are whitish or brownish.

440. The reproduction of mosses is mainly sexual,
but often brood-masses are found resembling those of
liverworts. The sexual organs develop either upon the
ends of the main stems, within flower-like rosettes of
leaves, or on the ends of short branches in the axils of the
leaves.

441. The antherids are club-shaped or gloi)ose struc-

250 PHYLUiM VIII. BRYOPHYTA

tures whose interior cells produce sperms, which escape
from the antherid through a rent in its wall. Each
spermatogenous cell contains one spirally coiled sperm,
which, when set free, swims by means of its two long cilia.
442. The archegones are elongated, flask-shaped bodies
with a swollen base (''venter") and a long slender
neck. At maturity the neck has an open channel from
its apex to the base, where there is a rounded egg. In
some mosses the antherids and archegones are inter-
mixed in the same "flower," but in other cases they
occur upon different parts of the same plant ( monoe-
cious), or even upon different plants (dioecious).

Fig. 125. — Antherids and Fio. 126. — Archegones and eggs

sperms (Sphagnum and (Sphagnum and Funaria).

Funaria).

443. The act of fertilization requires water; but as the
sperms are very minute, a dewdrop may be suflacient.
The sperms swim to the open neck of the archegone,
down which they pass to the egg. The egg now begins
to divide rapidly, growing upward, eventually forming
the sporophyte. In most mosses the sporophyte is
narrow and elongated below, forming a stalk (seta)
which supports the upper spore-bearing part (the capsule
or spore-case). The epidermis of the latter is usually
provided with stomata, especially toward its basal part.

444. The spore-case, when ripe, usually opens by a
lid which falls off, leaving a round opening, generally
fringed with many teeth. In most species as the sporo-

ORDERS OF MOSSES 251

phyto elongates it carries up the remains of the distended
archegone as a Uttle cap (calyptra).

445. The spores, which are round or angular cells
containing protoplasm, chloroplasts, oil-drops, etc.,
germinate quickly upon moist soil. Each spore pro-
trudes a tubular filament, which develops into a conferva-
like ])ranching growth of green cells, called the '^pro-
tonema." Upon this buds are event uall}^ produced from
which spring up the leafy stems, thus completing the
round of life.

446. There are three orders of Mosses, including about
12,600 species, as follows: (1) Black Mosses (Order An-
dreas ales), composed of a few small and rare mosses
whose spore-cases open by four longitudinal slits; (2)
Peat-mosses (Order Sphagnales), composed of large,
soft and usually pale-colored plants, with clustered lat-
eral branches; they inhabit bogs and swamp}- places,
where they form dense moist cushions, often
of great extent. On account of pecuharities
in the structure of their leaves they are en-
abled to absorb and hold large quantities of
water, and for this reason they are exten-
sively used for "packing" in the transporta-
tion of living plants. They all belong to Fig. 127 —
the genus Sphagnum, and their spore-cases (Amirt<aeu and
open by a circular lid, leaving an unguarded

opening (without teeth). In this and the preceding
order the stalk supporting the spore-case is an extension of
the gametophyte stc^n and not a part of the sporophyte.

447. (3) True Mosses (Order Bryales) include the
great majority of the species of this class. They are
usually bright green (in a few genera brownish), and in
most instances live upon moist ground and rocks, or
upon the bark of trees; in a comparatively small number

252 PHYLUM VIII. BRYOPHYTA

of cases the species live in the water. They are undoubt-
edly the highest of the class, and show a greater differ-
entiation of tissues than either of the pre-
ceding orders. The spore-cases usually
r^ open by a circular lid (operculum), and
' V the opening is usually guarded by one or
_ two rows of teeth (the peristome) of which
Sporophytea there may be 4, 8, 16, 32 or 64. Here

(Bryales). ^ \ ^ i .

the seta is a part of the sporopnyte.
448. There are more than fifty families of True
Mosses, of which about one-half are Top Mosses
(Acrocarpi), i.e. bearing their sporophytes at the summit
of the gametophyte stem, the remainder being Side
Mosses (Pleurocarpi) , with laterally borne sporophytes.
Among the first are Turf Mosses (Dicranaceae) , Cushion
Mosses (Leucohryaceae) , Petticoat-mosses \>
(Splachnum) , Bristle Mosses {Funariaceae
and Timmiaceae) y Ephemeral Mosses {Ephe-
merum), Wood Mosses (Bryaceae and Mnia-
ceae), Humpback Mosses {Buxhaumiaceae) ,
and Hair-cap Mosses (Po^y^nc/iaceae) . Among Top " moss,
the Side Mosses are the Brook Mosses [b on-
tinalaceae), the Tree Mosses {Climaciaceae) , and the Bog
Mosses (Hypnaceae).

Laboratory Studies, (a) Collect several kinds of mosses in
fruit; some of these should be of large species. Note the
brownish root-hairs, the stem and leaves, the spore-fruit (sporo-
phyte) composed of a slender stalk (seta) bearing a spore-case,
the latter in some species covered by a membranous or hairy
cap (calyptra).

(6) Select a broad-leaved species. Mount a single leaf in
water, and examine with a lower power. Note that the leaf
is (generally) a single layer of cells, and that the midrib (if
present) is composed of elongated cells. Make cross- and
longitudinal sections of stems of the larger species, and note
that some of the cells are elongated and fiber-like.

LABORATORY STUDIES 253

(c) Place a spore-case under tlic microscope and examine
with a low power, noting the lid. Now remove the lid and
observe the teeth. The teeth may be studied still better by
splitting the spore-case from base to apex and then mounting
in alcohol, and afterward adding potassium hydrate: or the
lid may be removed and a transection of the si)ore-case made
just below the peristome, so as to show the latter from above.
In these specimens spores may be studied also.

{(I) Split a young spore-case and examine the external sur-
face of the lower part for breathing-pores, and note internally
the adjacent chlorophyll tissues, and the sporogenous layer
above.

(e) Collect a number of mosses not in fruit, showing at the
apex of their stems little cup-shaped whorls of leaves. IVIake
several vertical sections of one of these cups, and mount in
water. Examine for antherids and archegones. Sperms may
sometimes be seen with a high power.

(/) The first stage (protonema) of a moss gametopl\vte may
be found by scraping off some of the greenish growth from a wall
or cliff or surface of a greenhouse flower pot where yomig mosses
are just springing up. By mounting some of this in water and
washing awaj^ the dirt the branching green growth may
generally be seen, with here and there the buds which give rise
to leafy stems.

LITERATURE OF BRYOPHYTA

D. H. Campbell, The Structure and Development of Mosses and
Ferns, New York, 1905.

L. AI. Underwood, Descriptive Catalogue of the Xorth American
Hepaticae, Champaign, 1883.

L. Lesquereux and T. P. James, Manual of the Mosses of
North America, Boston, 1884.

A. J. Grout, Mosses with a Hand Lens and Microscope, Brook-
lyn, 1905-1911.

CHAPTER XV

PHYLUM IX. PTERIDOPHYTA*

THE FERNS

449. The Ferns are green plants that as to their
gametophytes are of smaller size than the INIossworts,
while, as to their sporophytes they are much larger and
more complex. In fact the gametophyte generation is
so small compared with the sporophyte that it is usually
overlooked, or when seen is often not recognized as a
fern at all by those who are not familiar with the whole
life cycle of these plants. The fern that we commonly
see with its roots, solid stems, and ample leaves is the
sporophyte generation, which has become so large and
conspicuous in this phylum that it completely over-
shadows the little gametophyte.

450. The gametophyte (commonly called the ''pro-
thallium") is usually a flat thallus, of
one or more layers of nearly uniform
chlorophyll-bearing cells, the whole
being rounded or heart-shaped in out-
line. Its longitudinal axis is consider-

FiG. 130.— Game- ably thickeued, and this portion is pro-

tophytes" 7 i i

vided underneath with many root-hairs,
intermingled with which in most cases are the antherids
and the archegones.

451. The antherids are nearly globular, few-celled

* This name is here used in the narrower sense excluding Cala-
mites and Lycopods.

254

FERN STRUCTURE

:oo

Fig. 131.— Fern arch-
1 r ,^ • , . , 1 egone, egg, antherid and

where one oi them unites with sperm.

structures consisting of an outer hi^-er of cells surrounding
a central mass of small cells, each of which produces
a sperm. When mature, the antherids rupture and
permit the escape of the spiral multiciliated sperms
which swim with a rotary motion.

452. The archegones are flask-shaped organs sunken
into the tissues of the plant. At first
the neck is closed, but at maturity it
opens down to the egg. Fertilization
takes place in water (after rains or
heavy dews), the sperms swimming
to and down the neck of the arche-
gone,
the egg.

453. Sporophyte. After fertilization the egg divides
again and again, soon producing a solid stem from which
a root springs at one end, while from the other the leaves
arise. The latter are at first small and quite simple in
structure, but those formed later are larger and more
and more complex in structure, until finally the full form

is reached, and still later the full
size. The stem, bearing leaves
and roots, constitutes the sporo-
phyte, which is sharply contrasted
with the gametophyte in structure,
size, and duration, the latter being
short-lived, small, and of simple
structure, while the former is long-lived, often of large
size, and of great complexity of structure. On this
plant the spores are eventually produced which on
germination give rise to gametophytes like those with
which we started, thus completing the round of life. In
most Ferns the spores are of one kind, only (isospores),
but in a few they are of two kinds (heterospores) in

<M^'^

Fig

132. — Development of
fern sporophyte.

256 PHYLUM IX. PTERIDOPHYTA

which some arc small (microspores) and the others large
(megaspores).

454. In looking over the whole structure of the Ferns
it will be seen that the sporophyte has become the
dominant generation. This is due to the fact that in
its development it has pushed roots of its own down into
the ground from its lower end, thus insuring a constant
supply of water, while at the same time it has pushed
out some of the green tissue from its upper part into flat
expansions (leaves), thus insuring the supply of car-
bohydrates. The sporophyte has thus become in-
dependent of the gametophyte, and the latter, being now
useless after the maturity and disappearance of the sexual
organs, has become very short-lived, while the rooted
and leafy sporophyte has developed into a long-lived
plant, which may continue its growth for many years.

455. With this longer life and larger size the fern
sporophytes have developed many kinds of tissues in
addition to parenchyma, including collenchyma, scler-
enchyma, fibrous tissue, tracheary tissue, and sieve
tissue, some of which appear to be as highly specialized
as in the flowering plants. Furthermore, true vascular
bundles as well as bundles of fibrous tissue are developed,
the roots containing bundles of the radial type, and the
solid stems and leaves, of the concentric tj^pe. The
epidermis and stomata are scarcely to be distinguished
from those of the highest plants.

456. The typically large leaves are sometimes simple,
flat blades, but more commonly they have branched into
*' compound" blades of extraordinary complexity and
beauty of outline. The young leaves before expanding
are generally coiled or rolled, so that as they grow up
and open they unroll from below upward (i.e. cir-
cinately). Their vascular bundles (here usually called

OLD-FASHIONED FERNS 257

''veins") present different patterns, sometimes being
parallel to one another or divergent (veins ''free"), or
uniting here and there in a netted fashion (veins
"reticulated").

457. Since the sporophytes of ferns are long-lived
the}" delay the formation of their spores, this sometimes
not taking place for a few years (or many years in tree
ferns). In the more primitive ferns the spores develop
from internal cells (as in Anthoceros of the Bryophyta),
but in the higher forms they are produced in superficial
sporangia.

458. On account of the dominance of the sporophyte
its structure has been emphasized in the s^^stematic
classification of the ferns, although some consideration
has latterly been given to gametophyte characters.
About 3800 species of Ferns have been described, and
they are widely distributed throughout warm and tem-
perate regions.

459. There are two classes of Ferns, as follows:
1. Old-fashioned Ferns (Class Eusporangiatae) in which
the spores develop from internal cells.

Fig. 133. — Ophioglossuni. Fig. 134. — Angiopteria

(Marattialcs); develop-
ment of sporangia.

460. Here are the Adder-tongues (Order Opiiio-
GLOSSALEs) by many botanists regarded as the lowest of
the Ferns, and not very distantly related to Anthoceros
of the preceding phylum. Here too are placed the

258 PHYLUM IX. PTERIDOPHYTA

Marattias (Order Marattiales), large, very leafy ferns
of the tropics, formerly abundant, now nearly extinct,
and with them may be placed the aquatic Quillworts
(Order Isoctales) with slender rush-like leaves. The
latter produce two kinds of spores, viz. microspores
which are small, and megaspores which are much larger.
The plants are thus heterosporous, in contrast with
the preceding which are isosporous. The microspores
produce minute antheridial gametophytes (microgame-
tophytes), and the megaspores, larger archegonial
gametophj'tes (megagametophy tes) .

2. Modern Ferns (Class Leptosporangiatae) develop
their sporangia from superficial cells.

461. These are our common ferns, and this class
includes the greater part of the species now living. In
them the sporangia are usually developed on the lower
surface of the leaves in clusters ('' sori ") of various shapes,
and these may be naked or covered
with an indusium. The mature spor-
angium (spore-case) in most common
ferns has a ring of thicker cells ex-
tending around it. When these be-
come (hy, they contract in such a way
„ ,^, ,, , as to break open the spore-case and

Fig. 13o. — Modern ^ ^

ferns (sporangium and thus sct the sporcs free. Most Modcm

son). '■

Ferns are terrestrial, and hence may
be set off as Land Ferns (Order Fili gales), in which
are the less common CHmbing Ferns (Lygodium), Tree
Ferns (FsunWy Cyatheaceae) , Filmy Ferns (Family //?//rteno-
phyllaceae), and Common Ferns (Family Polypodiaceae).
In the last-named family nearly all of the ferns of our
woodlands are found, including such species as the
common Polypody (Polypodiiim vulgare), the Golden
Fern of California {Gymnograrnme triangularis), the

WATER FERNS 259

Maidenhair of the North {Adiantum pedatum), and of
the South {A. capillus-ve?ieris) , the common Brake
{Pteridium aquilinum) the Spleenworts (Asplenium) of
many species, the Shield-ferns (Aspidium), also of many
species, the curious little Walking- fern {Camptosorus
rhizophyllus), the Bladder-fern (Filix fragilis) and the
large Ostrich-fern {Onoclea struthiopteris) .

462. Some of the Modern Ferns have become aquatic
and hence are known as Water Ferns
(Order Marsiliales) in which two kinds of
spores ("heterospores") are produced, mic-
rospores and megaspores, which in time give
rise respectively to antheridial, and arch-
egonial gametophytes. The Marsilias are
rooted plants, with floating, 4-parted leaves,
while the Salvinias are small, floating, nearly rootless
plants, with simple leaves.

Laboratory Studies, (a) Collect several different kinds of
common ferns, including the underground portions as well as
the leaves. Study the vascular bundles, stone tissue, and
fibrous tissue in the underground stem.

(6) Examine the disposition of the small vascular bundles in
the leaves, whether free or reticulated. Peel off a bit of epider-
mis from both surfaces, and study the breathing-pores.

(c) With a low-power study the sori (clusters of spore-cases),
using top light only. The sporangia maj^ be seen and their
attachment made out in this way in those cases where there
is no indusium covering the sorus.

{d) ]\lake a vertical section through a sorus and stud}' care-
fully, looking for the ring of darker cells on the spore cases.

(e) Gametophytes of ferns may often be found in plant-
houses on or in flower-pots near ferns. They may be obtained
also by sowing the fresh spores in flower-pots and keeping them
in a warm damp place (a greenhouse is best). In a month or
two the gametophytes will be full grown. Collect a few of
these of various sizes, carefully wash off the dirt from the under
side, then mount in water, and examine the untlcr surface for

260 PHYLUM IX. PTERIDOPHYTA

antherids and archegoncs. By careful searching j^oung
fernlets may be found still attached to the gametophytes
(prothallia).

(/) If possible secure specimens of Adder-tongue, and com-
pare the structure of the sporangia with the foregoing.

(g) Search the borders of lakes, ponds, and slow streams for
Marsilias. They may probably be found in every part of
the country, although they are rarely collected.

(h) Where possible compare the structure of the sporangia
and sori of Marattias (from greenhouses) with those of common
ferns.

(i) In some places it is possible to secure sporophytes of
Isoetes for a comparative study.

0") Try to secure fresh spores of Isoetes or Marsilia for a
study of heterospores, and of the antheridial, and archegonial
gametophytes.

LITERATURE OF PTERIDOPHYTA

D. H. Campbell, The Structure and Development of Mosses and

Ferns, New York, 1905.
N. L. Britton and Addison Brown, Illustrated Flora of the

Northern States and Canada, Second Edition, New York,

1913.
B. L. Robinson and M. L. Fernald, Graifs New Manual of

Botany, New York, 1908.
J. K. Small, Flora of the Southeastern United States, Second

Edition, New York, 1913.
L. M. Underwood, Ferns and Fern Allies, New York, 1905.

CHAPTER XVI

PHYLUM X. CALAMOPHYTA
THE CALAMITES

463. As far as we know them the Calamites are green
plants in which the marked difference between the small
gametophytes and the large sporophytes seen in the
Ferns is continued, but here the sporophyte stems are
mostly hollow and jointed, and the leaves relatively
small. A great difficulty in studjdng the plants of this
phylum is that although common in the Paleozoic
period, but few (about 24 species) have survived to the
present time, and our knowledge of them is confined to
what w^e have been able to make out from fragmentary
fossils, helped out in some details by a study of the
surviving species.

464. This much, how^ever, has been made out pretty
certainly: Gametophytes small, and short-lived, mostly
monoecious; Sporophytes large, long-lived, with roots,
and elongated, cylindrical, jointed, often hollow stems,
bearing relatively small whorled leaves at the joints;
spores alike (isospores), or of two kinds (heterospores),
borne in cones of sporophylls (i.e. special spore-bearing
leaves).

465. Like the Ferns the Calamites have well-developed
tissues in the sporophyte generation; the vascular
bundles are of a higher type ("collateral"), and are
arranged in a cylinder in the stem. When these bundles
are "open" the stems have the power of increasing in

261

262 PHYLUM X. CALAMOPHYTA

diameter. The epidermis is abundantly supplied with
stomata.

466. The Wedge-leaved Calamites (Class Spheno-
phyllineae) were Paleozoic herbaceous
plants of moderate dimensions, whose sporo-
phyte stems Avere solid, jointed, grooved ex-
ternally, and at the joints bore spreading
whorls of wedge-shaped leaves. Their iso-
spores were borne in terminal cones com-
posed of whorls of 1- or 2-sporangiate spor-

ophylls. Sphenophyllum is the typical genus.

467. In the Horsetails (Class Equisetineae; of the
present, the plant-body of the sporophyte
consists of a hollow, elongated and jointed
herbaceous stem, bearing whorls of narrow,
united leaves, which form close sheaths; the
stem is grooved, and is usually rough and
hard from the large amount of silica depos-
ited in the epidermis.

468. The branches, w^hen present, are in
whorls. Both the main axis and the branches are in
most cases richly supplied with chlorophyll-bearing tis-
sue; but in some of the species the stems which bear
the spores are destitute of chlorophyll. All of the
species have underground stems, which bear roots and
rudimentary sheaths, and which each year send up the
vegetating and spore-bearing stems.

469. The Horsetails are perennial plants. In some
species the underground portions, only, persist, the
aerial stems dying at the end of each year; these are called
the annual-stemmed species. In other species the
aerial stems persist; they are hence known as perennial-
stemmed.

470. The epidermal cells are mostly narrow and

HORSETAILS 263

elongated. The stomata which are present in all the
chlorophyll-bearing parts of the plant, are arranged with
more or less regularity in longitudinal rows; on the stem
they occur in the channels between the numerous ridges.
The vascular bundles of the stem are disposed in a cyl-
inder and run parallel with each other from node to
node, where they join with one another. They contain
tracheary, sieve and fibrous tissues, arranged somewhat
as they are in the bundles of flowering plants.

471. The spores of Horsetails are produced in cones at
the summit of the stems. The cones are composed of
crowded whorls of shield-shaped leaves (sporophylls),
each of which bears upon its under surface five to ten
sporangia. The spores are spherical, and at maturity
the outer wall spUts spirally into four narrow filaments
{elaters) which unroll when dry, and roll up around the
spore again when moistened. Their office seems to be
to aid in setting the spores free from the spore-cases. The
spores germinate soon after falling
upon water or moist earth, enlarg-
ing and successively dividing until
a fiattish irregular gametophj'te
(the prothallium) a few milli-
meters in l)readth is produced. It
bears antherids and archegones ^Jj-- JS'-'/S'SyTo,).
resembling those of the ferns upon

its lobes or their edges; in some cases both sexual organs
are on the same gametophyte, while very commonly
they are upon separate gametophytes, although the
spores show no differences. The sperms are spiral and
multiciliated.

472. This class contains but one family (Kquisc-
taceae), including a single genus,' Eciuisetum. and twenty-
four species of herbaceous plants usually a meter or less

264 PHYLUM X. CALAMOPHYTA

in height, but in certain tropical species attaining a
length of 10 meters or more. Among the better known
are the Common Horsetail {Equisetiim arvense), which
sends up short lived, pale or brownish cone-bearing stems
in spring, and profusely branching green stems in sum-
mer {E. telmateia, the Great Horsetail of Europe and our
own Northwestern region, resembles, but is larger than,
the Common Horsetail); the Woodland Horsetail {E.
sijlvaticum), whose green cone-bearing stems branch
profusely after fruiting, and persist all summer; and the
Scouring-rush, called also Dutch Rush {E. hiemale),
with green, branchless stems which produce cones, and
survive the winter. The genus Equisetum originated in
the Paleozoic period, and so is ver}^ old. Some of its
species have become extinct, as is the case with several
related genera.

473. The Old Calamites (Class Calamarineae) were
Paleozoic plants whose sporophytes were
often trees, with hollow, jointed stems,
whose collateral vascular bundles allowed
an increase in diameter by the develop-
ment of a cambial zone. The leaves
were separate, narrow, and whorled at
op^'yte^anifspo^ea the joiuts of the stcm. The heterospores
of Old Caianute. ^^^^^ bome in terminal cones composed
of whorls of sporophylls, each bearing one or more spo-
rangia. Only fragmentary fossils of these plants are
known.

Laboratory Studies, (a) Collect in early spring a number
of cone-bearing stems of the Common Horsetail. Note the
joints (nodes), bearing whorls of united flat leaves, and the
cone, composed of whorls of shield-shaped leaves (sporophylls).
Split the cone and stem and note that the latter is hollow, with
closed nodes.

(6) Carefully dissect put a single sporophyll from the cone,

LABORATORY STUDU-.S 265

and examine it, using a low power. Note the sac-shaped spore
cases upon the under side of the leaf. JMount some of the spores
dry, using no cover-glass, and examine with the 16 mm.
objective. Breathe upon the spores very gently to moisten
them, and notice the coiling of the elatcrs; observe the quick
uncoiling which takes place upon the evaporation of the
moisture.

(c) Sow a quantity of the fresh spores upon moist earth or
porous pottery, covering with a bell-jar and taking every pre-
caution to secure constant moisture. The spores will begin to
germinate in a few days, when studies of successive stages of
growth may be taken up. By care the mature gametophytes
(prothallia) may be grown, and the antherids and archegones
studied.

{d) ]\Iake ver}^ thin cross-sections of the stem of the Common
Horsetail. Note the position of the vascular bundles. Now
make a vertical section of the bundles and study the tissues,
using high powers.

(e) Study the breathing-pores on the green stems of the Com-
mon Horsetail. Compare these with those of the Scouring
Rush. Study also the disposition of the chlorophyll-bearing
tissue in cross-sections of both stems.

(/) Examine underground stems of Horsetails, and compare
the structure with that of the aerial stems. Make cross-sec-
tions of the roots which are attached to these underground
stems.

LITERATURE OF C.ALAMOPHYTA

The same as for the preceding jihylum, and
M. C. Stopes, Ancient Plants, London, 1910.

CHAPTER XVII

PHYLUM XL LEPIDOPHYTA
THE LYCOPODS

474. Here as in the Calamites we are dealing with a
phylum from which many of the forms have disappeared
through extinction, leaving only their fragmentary
fossils. Yet here again by a study of the plants that
have survived, and a comparison of their structure
with such fossil remains as have been found, we may make
out pretty clearly the nature of the plants that constitute
this phylum.

475. Accordingly the Lycopods may be characterized
as chlorophyll-green, terrestrial plants, exhibiting two
generations in each hfe-cycle, viz. : (1) thegametophyte,
which is small, short-lived, and typically tuberous or
globose, with few rhizoids or none, and often dioecious;
the sexual organs are deeply sunken, and the sperms
are biciliated; (2) the sporophyte, which is large and
long-lived, with roots, a solid, continuous (not jointed)
stem, and many small spirally arranged or opposite
leaves, some of which, the sporophylls, with sporangia
in their axils, are in terminal cones. The spores are
mostly heterosporous. The tissues of Lycopods re-
semble those of Ferns and Calamites in both number
and kind. Their vascular bundles are essentially Uke
those of the Ferns (concentric), and in some cases are
separate, while in others they are consolidated into a
central compound bundle, surrounded by a mass of thick-

266

GROUND PINES

267

walled fibrous tissue. The epidermis is abundantly
supplied with stomata.

476. The phylum contains about 700 living species,
and consists of two quite distinct classes, viz.: The
Lower Lycopods (Class Lycopodineae) mainly dis-
tinguished by being isosporous, and the Higher Lycopods
(Class Lepidodendrineae) which are heterosporous.

477. In the first we find the Ground Pines (Family
Lycopodiaccae), otherwise known as Club-mosses, which
are terrestrial, perennial, evergreen plants with many
small, generally moss-like leaves cover-
ing the stems. The sporophylls are
often crowded toward the summits of
certain branches, in some cases form-
ing well-marked cones (strobili). The
spores are all of one kind, and are
borne in roundish sporangia of which
there is one on the upper surface of sperms, archegon
each leaf near the base.

The Ground Pines are common in the Appa-
lachian region, Canada, and northwestward, and all
belong to the genus Lycopodium, including L. clavatum,
L. complanatum and L. dendroideimi, all ex-
tensively used in Christmas decorations. Fos-
sil specimens of Ground Pines from the Paleo-
zoic period have been recorded.

478. In the second class are the Club-mosses
(Family Sclaginellaceae) which resemble the
Ground Pines, but in our common species are
generally smaller and more moss-like, and
have (with few exceptions) four-ranked leaves.
Their sporangia occur singly on the sporophylls
which are clustered into terminal spikes (cones). The
spores arc of two kinds: the small ones (microspores)

Fig. 141. — Lycopodium
(gainetophyte, antherid.s,
ea and

©qo

Fig. 142.—
Lycopodium
(sporophyte,

sp o r a n gia,

Bpores).

268 PHYLU:\I XI. LEPIDOPHYTA

which are very numerous in their sporangia, and the
hu'gcr ones (megaspores) which are mostly four in each
sporangium. These microsporangia and megasporangia
are intermingled in the cones. When mature the
microspores fall out and are blown awa}^, but it often
happens that the megaspores remain in the old wall of
the megasporangium.

479. The gametophytes of the Club-mosses have almost
disappeared. When a microspore germi-
nates, it becomes divided into a consider-
able number of cells, one of which is the
remnant of the gametophyte (prothallium),
while the other cells form one large an-
lagineiia (game- thcrid, each iuncr cell of which produces

tophytes, anthe- , . .,• , i

rid, sperms, ar- blClliated SpCrmS.

c egones, egg . ^g^^ ^^^^ mcgaspore likewise produces a

very small but many-celled gametophyte, which pro-
trudes but little from the ruptured spore-wall. Upon
this several archegones develop. This development
may take place while the megaspore is still enclosed
in the wall of its sporangium. After fertilization the
egg gives rise directly to a leafy
plant, which emerges from the spore-
wall in a way to remind one very
forcibly of the growth of a plantlet
from a seed. This resemblance is
made greater by the hkeness of the ^^^ i 4 4._seiagineUa
first leaves to cotyledons. spo^esf ^^^^' ^ ^ ° ^ ^ " ^ '*•

481. But one genus, Selaginella,
is known in this family. It contains many species,
most of which are tropical. Several species are com-
mon throughout the United States, and several exotic
species are frequently cultivated in plant-houses.

LEPIDODEXDRIDS 209

482. Allied to the Club-mosses are the arborescent
Lepidodendrids (Order Lepidodendrales) which were
abundant in the Paleozoic period, and which disappeared
in the Mesozoic. We have fragmentary fossils of the
sporophytes, which were large dichotomously branched
trees, sometimes 30 meters high and a

meter in diameter. There was a large ^^&^^
central vascular bundle, which how- V^ >t 1^
ever formed a peripheral cambium
so that the stems increased their di-
ameter much as in the case of higher
plants. The stems and branches
were thickly clothed with pointed tZ^TolX'''"' '''''"
leaves a decimeter or more in length,
and when these fell off they left large scars of charac-
teristic shape and arrangement.

483. The fossil remains of the spore-bearing cones, of
which many specimens have been found, indicate that
they contained two kinds of spores. Hence it is certain
that the Lepidodendrids were allied to the Club-mosses.
The more common genera are Lepidodendron, and
Sigillaria.

Laboratory Studies, (a) Secure a few fresh or alcoholic
specimens of various kinds of Lycopods in fruit. Ground
Pines may be collected in many places in the eastern United
States. The Club-mosses may be obtained in plant-houses.

(6) IVIake cross-sections of the stems, and study the vascular
bundles in Lycopodium where they are imbedded in a thick
mass of fibrous tissue. Examine the leaves, noting the small
vascular bundle in the midrib. Stud}' the epidermis, which
contains numerous breathing-pores.

(d) Carefully remove a sporophyll from a cone of Lycopo-
dium, and study the sporangium and spores. Further exami-
nation will show that the spores are of one kind only.

270 PHYLUM XI. LEPIDOPHYTA

(e) Carefully dissect out from the fruiting cone of Selaginella
several sporangia, some with four large spores, and others with
many small spores.

LITERATURE OF LEPIDOPHYTA

The same as for the Ferns and Calamites.

CHAPTER XVIII

PHYLUM XII. CYCADOPHYTA

THE CYCADS

484. Like the two preceding phyla this one is a mere
remnant of a much larger group. All told there are only
about 140 living species belonging to six families, while
we know of as many more families whose species have
become extinct. Enough has been made out as to the
structure of living and extinct forms to enable us to
define the Cycad phylum as follows:

485. Their archegonial gametophytes are so dependent
that they are enclosed in the megaspore, which is itself
retained in the sporangium; the antheridial gametophyte
is minute and free, and its tubular antherid typically
develops two or more multiciliated sperms; after fer-
tilization of the egg the megasporangium becomes a
''seed." The sporophyte is first enclosed in the seed,
where it is nourished by the gametophyte, and later it
escapes by developing roots below, and expanding its
leaves above; eventually some leaves become sporophylls
and develop microspores and megaspores.

486. It is instructive here to compare the higher
Lycopods with the Cycads. In both there are micro-
spores and megaspores, and in both the microspores
always are set free from the sporangium. In both again
the microspore produces a very small (one- to few-celled)
gametophyte. However, the antherid of the higher
Lycopods is a few-celled structure, with many minute,
biciliated sperms, while in the Cycads the antherid is

271

272 PHYLUM XII. CYCADOPHYTA

reduced to a simple tube, which contains usually two
large, multiciliated sperms (suggesting a correlation
between size and the number of sperms). In both
phyla, again, the megaspores develop from a spore
mother-cell (archespore) as tetrads, but while in the
Lycopods all four may become mature,
in the Cycads only one matures. In Ly-
copods the megaspores separate from the
sporangial tissue as they develop, and
normally are set free, while in Cycads
Yia. r46.— Cyoad ^^® smglc mcgasporc remains perma-
fnd sSms!^^' ^^^^ nently connected with and surrounded
by the sporangial tissue. So the embryo
sporophyte of the former normally develops outside of
the megasporangium^ while in the latter it does so in-
side of the megasporangium, and thus forms the seed.

487. The lowest Cycads, the so-called **Seed-ferns"
(Class Pteridospermeae) , were abundant in the Paleo-
zoic period and are now known only from their fossil frag-
ments. They were long thought to be

ferns of an ancient type, but are now

known to have been seed-bearing plants.

Apparently they were derived from the

Marattias among the Old Ferns. Their

leaves were fern-like in shape and struc- fig. 147.— Pterido-

ture. Their stems were capable of in- and seTd. '''°'°''^'^''

creasing in diameter. It is now thought

that the Seed-ferns constituted a group of vast extent in

Paleozoic times.

488. In the Common Cycads of the present (Class
Cycadineae) the sporophytcs are usually erect, woody,
little-branched trees, rooted below, and bearing terminal
crowns of evergreen, pinnate leaves. The collateral
vascular bundles are arranged cylindrically in the stem,

COMMON CYCADS 273

and increase its thickness by the development of their
cambium, and by the formation of new bundles in the
cortical meristem. The sporophylls
which bear microspores and megaspores
form more or less distinct cones (strobili)
but occur on separate plants (dioecious).

489. The common greenhouse Cycad
(Cycas rcvoluta) produces elongated,
compact cones of microsporophylls, 20 epoJophytt^' m^gT
to 30 centimeters long and 5 to 6 centi- c^osp^r^ophyiL"'^ ""'
meters thick. Each sporophyll bears on

its lowTr surface numerous small scattered microspor-
angia containing microspores, constituting the so-called
'^ pollen." These microspores fall out, and on germi-
nation produce a small one- or two-celled gametophyte,
and a tubular antherid containing tw^o spirally many-
ciliated sperms (about 0.2 millimeter in diameter). The
megasporophylls constitute a loose terminal cone on the
main axis of the tree. Each sporophyll bears several
laterally placed megasporangia each of which has become
covered with an indusium-like structure (integument).
Within the body of the sporangium (now known as the
ovule) a megaspore develops, l^ut this at maturity does
not fall out but remains surrounded by nutrient tissue.
Here it germinates and develops a solid, many-celled
spheroidal gametophyte, and at its summit forms sev-
eral deeply sunken archegones, in which the eggs are of
remarkably large size (2 to 3 millimeters).

490. Fertilization of the egg takes place as follows:
The microspore is carried by the wind or other means to
the opening (micropyle) at the summit of the ovule
integument; there it germinates, the tubular antherid
penetrating the adjacent tissues; the sperms escape by the
rupture of the tube, and swim through the intervening

274 PHYLUIM XII. CYCADOPHYTA

watery fluid to the archegone, finally reaching the egg.

From the fertilized egg there is later developed a little
sporophyte which is nourished for a
time by the tissue of the surrounding
gametophyte. In the meantime the
integument of the sporangium has
greatly thickened into a mass of tissue
Fio. i49.-zanna ^^^^ extcmally and stony internally.

to°h"'tcr'' """^ ^^"'''' ^^'^^^^'^ ^^^ growth ceases the megaspor-
angium (ovule) with its contained

gametophyte and sporophyte falls off, as the ''seed."

491. After the fall of the seed when placed in proper
conditions as to moisture and temperature, the sporo-
phyte resumes its growth at the expense of the game-
tophyte (now called ''endosperm"), and soon sends out a
root, and later a green leaf, after which it becomes an
independent long-lived plant.

492. The other living Cycads are essentiall}^ similar
in structure to the foregoing. All of the species are
tropical or subtropical. jVIany that

lived in Mesozoic times have long
been extinct.

493. In the Mesozoic period there
flourished a group of Cycads that may
be called the "Flowering Plant An-
cestors" (Class Bennettitineae), ^''^- ^?Pfl~^?M°^"^^''
and which had "flowers" containing

a central cluster of stalked megasporangia, surrounded
by a whorl of pinnate microsporophylls. Below these
were many sterile bracts reminding one of flower-leaves
(perianth). The resemblance of this primitive flower
to the flowers of the simpler Flowering Plants such as
Magnolia, Asimina, Ranunculus, etc., is so great as to
suggest a genetic relationship.

CORDAITALES AND GIXKGOALES 275

494. The Conifer Ancestors of the Paleozoic period
(Order Cordaitales) were hirge trees 30 or more meters
in height, and bearing a dense crown of ])ranches and
hirge, paraHel-veined leaves, sometimes a meter or so
in length. Microspore and megaspore cones are known,
and even the seeds have been preserved, and many of
their details of structure made out.

Fig. 151. — Cordaites. Fig. 152. — Ginkgo (staniinate

and ovulate).

495. The Maidenhair Trees (Order Ginkgoales) re-
mind one in some respects of the preceding. They were
common in the Mesozoic period, but all are now extinct
excepting a single species {Ginkgo biloha) from eastern
Asia. They have parallel-veined, fan-shaped leaves,
and branching, woody stems. In the surviving species
the trees are dioecious. The bisporangiate micro-
sporophylls constitute a loose cone, while the mega-
sporophylls remind one of those of Cycas described
above. The seed integument becomes fleshy externally
and stony internally when mature.

496. The Joint-firs (Order Gnetales), including several
rather widely separated families, should probably ])e
placed here, although their relationship is doubtful,
especially since they have non-ciliated sperms. Ephedra
is a widely distributed genus of green, branching, leafless
shrubs resembling Equisetum in appearance. Gnetum
includes tropical shrubs and trees with large pinnately
veined leaves; Tumboa (Welwitschia) occurs in tropical
west Africa.

276 PHYLUM XII. CYCADOPHYTA

Laboratory Studies, (a) In many greenhouses may be
found well-grown sj^ccimens of Cycas and Zamia. Examine
these for the general appearance of Cycads.

(b) On inquiry it is possible that microspore cones of these
common Cycads may be found, and secured for a closer study.

(c) Old trees of Cycas produce their '^ flowers" of mega-
sporophylls every few years, and on inquiry some of the latter
may be secured in various stages of development for dissection
and study.

(d) Zamia plants in greenhouses frequently produce their
thick, rounded megasporophyll cones. These should be dis-
sected to find the sporangia (seeds).

(e) It should be remembered that various Cycads, including
Cycas and Zamia, grow in the Gulf states, and specimens may be
obtained for study without much difficulty.

(/) Ginkgo trees are grown in many parks and door yards,
and may be examined for their foliage and general appearance.

(g) In the spring look for microsporophylls and megasporo-
phylls of Ginkgo and later for ripe, fleshy seeds.

(h) From the middle of June to early in July, depending
upon the location, the sperms can sometimes be observed in the
seeds as follows: Take a seed and with a stout knife split off
two opposite sides (including the stony part of the integument).
If properly made a slice will be removed from each side of the
megagametophyte which can be removed with a portion of
the megasporangium (nucellus) adhering as a cap to its apex.
Upon carefully lifting this cap the microgametophytes will be
found hanging to its under side as thick, glistening, tube-like
bodies. Carefully dissect these off with very sharp scalpel
and mount in a solution containing about 5 per cent, of cane
sugar. The sperms (or at least the cells from which they arise)
will readily be visible even under low power of the microscope,
as they are very large, attaining a diameter of 0.1 millimeter.

LITERATURE OF CYCADOPHYTA

J. M. Coulter and C. J. Chamberlain, Morphology of

Gymnosperms, Chicago, 1910.
M. C. Stopes, Ancient Plants, London, 1910.

CHAPTER XIX

PHYLUM XIII. STROBILOPHYTA
THE CONIFERS

497. To a large extent this is a phylum of living plants,
and although many species and some genera have be-
come extinct, everj^ family is still represented in some part
of the world. The number of living species is about 400,
widely distributed throughout the earth. The Conifers
probably were derived from some of the old Cycads
{Cordaitales) to which they show some affinities.

498. In these plants there is a still more marked
alternation of generations than in the preceding phyla.
The gametophytes are so minute and short-lived that
they are rarely seen, while the sporophytes are mostly
great trees with long-lived perennial roots and stems and
mostly perennial green leaves also. The phylum may be
defined as follows: Megaspores and microspores mostly
borne in homogeneous cones of sporophylls on the
arboreous sporophytes. Archegonial gametophytes very
minute, solid, ellipsoid, and permanent]}' enclosed in the
megaspore, which in turn is retained in the megasporan-
gium; antheridial gametophyte minute, few-celled, free,
developing a tubular antherid containing two noncili-
ated sperms. After the fertilization of the egg and the
formation of the cylindrical, leafy sporophyte, the
megasporangium, covered by an indusial coat (integu-
ment), becomes a ''seed." The sporophyte upon esca})ing
from the seed in germination grows into a perennial,

277

278 PHYLUIM XIII. STROBILOPHYTA

long-lived tree, rooted below, and bearing green (mostly
perennial) leaves above.

499. Since the sporophytes are large and long-lived
their tissues are many and well-developed. Their
tracheary tissue is almost wholly of the form known as
tracheids, which are here marked on their radial faces
with ])ordered pits. Proper fibrous tissue is scanty or
wanting. The vascular bundles are of the open collateral
type, arranged in a cyUnder so that they provide for
increasing the diameter of the stems and roots. Turpen-
tine canals are present in all parts of the plant.

500. There are nine families of conifers, a few only of
which need be noticed here. In all the microspore cones
are well developed, but there is a gradual simpUfication
of the megaspore cones from those with many sporo-
phylls to those with few or one. The Taxodiums (Family
Taxodiaceae) , Microsporophylls with two to eight spor-
angia: megasporophylls woody, much en-
larged distally, bearing two to several erect
or inverted seeds, forming compact, elhpsoid
cones; ''seed scale" wanting. Here are the

Sequoia (seed- Bald Cypresscs (Taxodium) and Redwoods
(Sequoia), very old types that originated in
the Mesozoic, and have persisted with reduced numbers
to the present. The Redwoods, now confined to the
mountains of California, were once widely distributed
in the Northern Hemisphere.

501. The Old Pines (Family Araucariaceae) . Micro-
sporophylls with five to fifteen spor- j,
angia: megasporophylls woody, slightly /^^ ^m
enlarged distally, bearing one inverted * ^P
seed, forming compact spheroidal cones; Fig. 154— Arauca-
"seed scale" rudimentary. The Old

Pines are now confined to the Southern Hemisphere, and

PINES 279

are represented by but two living genera, Araucaria and
Agatliis. These and other genera were represented in
the Northern Hemisphere in Mesozoic and later periods.

502. Modern Pines (Family Ahietaceae). These may
be illustrated by the common Scotch Pine {Pinus silves-
iris), in which the microsporophylls are
massed into cones 1 centimeter long, and
these cones are themselves massed in clus-
ters. Each microsporophyll bears two spor-
angia on its lower surface. The microspores
are spheroidal but the outer layer of the p^^^^
wall is often swelled out into two bladder- spore cone and

microspore).

like distentions at opposite sides. These
microspores C' pollen") escape from the sporangia in
the spring, and may be carried by the wind for long
distances (sometimes for hundreds of miles).

503. The megaspore cones grow singly near the ends
of the upper twigs of the season's growth, and are about

1 centimeter long. They consist of an
axis on which are borne flat megasporo-
phylls, each bearing two inverted mega-
sporangia (ovules). In these plants fertili-
zation is a slow process: the microspores
Fig. 156.— Pinus Carried by the wind fall between the meg-
see -cone). asporophylls (in the spring or early sum-
mer), where each spore pushes out a tubular antherid
("pollen tube") which penetrates the ovule tissue. This
stimulates the growth of the tissues of the cone and it
increases in size and bends downward on its stalk. In
the meantime the ovules enlarge, the upper ("chalazal")
end doveloi)ing a thickened mass of grcMMi tissue which
grows far beyond the end of the sporojihyll, constituting
the ''seed scale." These green "seed scales'' are in

280 PHYLUM XIII. STROBILOPHYTA

reality the distal portions of the ovules, and function as
photosynthetic structures for a year (or more).

504. In the first summer or autumn an axial spore
mother-cell C'archespore") arises in the interior tissues
of the ovule, and this ultimately divides into four cells
(four young megaspores), only the lowermost of which
enlarges into the fully developed megaspore. By the
second spring this megaspore has divided and subdivided

until a solid ellipsoidal cellular
mass is formed — the gameto-
phyte. Then from certain cells
on the summit of the gameto-
phyte several (usually four)
sunken archegones arise, when
Fig 157— Pinus (archegoniai, everything is ready for the com-

andanthendial gametophytcs). ^ o ^

pletion of the process of fertili-
zation. In the meantime, the pollen tube resumes its
growth, bringing the two non-ciliated sperms to the
mouth of an archegone where one of the sperms soon
fuses with the egg, and fertilization is completed, a
little more than a year after pollination.

505. By repeated subdivision and continued growth
of the zygote a cylindrical stem is formed, rooted below,
and with a whorl of narrow leaves above. This is the
sporophyte (or "embryo" of the seed). It is nourished
by the gametophyte tissue in which it is imbedded. In the
meantime ovule, "seed scale," and cone have increased
in size, and later the "seed scales" lose their chlorophyll
and become woody. Still later by the lessened supply
of water all parts of the cone become dry, stopping the
growth of the young sporophyte. The cone- and seeds
are now "ripe," and by the spreading of the dry scales
the part of the seed containing the embryo is split loose
and blown away.

Pinus (seeds, and
young sporo-

PINES 281

506. Germination of the seed takes place when water
is again suppUecl, resulting in a resumption of the growth
of the embryo, the bursting of the brittle
integument (indusium) and the escape of nN\\|/A
the root, stem and leaves of the embryo. C^^^f^
The root penetrates the soil and provides C^^\ \ i
water, while the leaves (now green) pro- . — ^ (
vide carbohj^drates, completing the estab-
lishment of the new plant. f i a . 1 5 s

507. There are about half a dozen genera
of Modern Pines, distinguished by their ^^^^""^^
leaves and cones, as follows:

I. Twigs with primary green
leaves only.

1. Cone scales persistent.

i. Leaves prismatic, four-
angled. (Spruces) Picea
ii. Leaves fiat.

(a) Megasporophylls (False

long, protruding. Hemlocks) Pseudotsuga

(6) Megasporophylls
short, not protrud-
ing. (Hemlocks) Tsuga

2. Cone scales deciduous, the

cone falling to pieces. (Firs) Abies

H. Twigs with both primary and
secondary green leaves.
L Leaves evergreen. (Cedars) Cedrus

2. Leaves deciduous. (Larches) Larix

in. Twigs with only secondary

green leaves. (Pines) Pinus

508. The very young twigs of the last genus (Pinus) are
covered with flat primary leaves which die immediately,
and in their axils short twiglets push out bearing five,
three or two very narrow leaves, the secondary leaves,
which are the only ones persistent on these plants. Com-

282 PHYLUM XIII. STROBILOPHYTA

mon ''White Pines" have five leaves in a fascicle, the
"Yellow Pines" three or two. An Arizona pine has but
one leaf on each twiglet.

509. In the Cypresses (Family Ciipressaceae), and
Thuyas (Family Thuyopsidaccac) the woody cones are
small and composed of only a few scales, and the leaves
are small and scale-like. In the Junipers (Family Juni-
peraceac) some twigs bear scale-leaves and others fiat
leaves, while the cone scales are few and fleshy, so that
the cones are fleshy. In the Yews (Order Taxales) the
reduction in the cones is carried so far that but one scale
remains, and that has become fleshy. In the proper
Yews (Taxus) the leaves are flat, but in some related
genera they are scale-like.

Laboratory Studies, (a) In the spring of the j^ear collect a
quantity of the microspore (staminate) cones of a pine (Scotch
or Austrian are very good), and preserve such as are not wanted
for immediate use in alcohol. Collect at the same time the
3'oung megaspore (ovule-bearing) cones which are to be found
at the ends of the new shoots.

(6) SpUt both kinds of cones vertically, and study their
structure, comparing the one with the other.

(c) Study microspores from young and mature cones. In
the young microspores look for the cells representing the game-
tophyte; in the mature microspores note the bladder-like
enlargements of the outer coat.

((/) Study young megaspore cones of different ages, and note
the growth of the "seed scale."

(e) Study megaspore cones one year old and note the devel-
opment of the gametophyte, and later the archegones.

(/) Note that the megaspore cones of Scotch and Austrian
pines are two years in coming to maturity. Make vertical
sections of cones of various ages, and note the growth of the
seed. Note the thin wing (useful in their dispersion) on the
seeds. Make longitudinal sections of seeds, and note the
little sporophyte with its several leaves (cotyledons).

(g) Examine the very young twigs as they develop in the

LABORATORY STUDIES 283

spring and note the primary leaves with the growth of twiglets
in tlieir axils bearing young secondary leaves.

(h) Make cross-sections of mature leaves, and note the
turpentine-canals, one near each angle, with others symmetric-
ally arranged between. JMake cross-sections of the young
twigs, and note the canals in the rind or bark. Make similar
sections of the wood of the trunk, and note similar canals at
intervals.

(0 Make very thin cross-sections of the mature wood of the
stem and note shape and size of the cells; note also the gradual
decrease in their size in passing from the inner to the outer side
of a growth ring. Now make a very thin longitudinal-radial
section, and observe the bordered pits. A longitudinal section
at right angles to the last (longitudinal-tangential) will show
no bordered pits. In all these sections note that the wood is
made up of but one kind of cells, viz. tracheids.

(j) In a cross-section of a stem note the thin radiating plates
of tissue (medullary rays), in many cases extending from pith
to bark. In longitudinal-tangential section of the stem these
rays are seen in cross-section to be made of thick-walled cells.
In longitudinal-radial sections the raj^s are seen split lengthwise.

(k) Make very thin cross-sections of the stem through bark
and wood, and note the layers of ver}^ soft thin-walled tissue
(cambium) between wood and bark. This may be made more
evident bj' soaking the section for some time in eosin, by which
the cambium will be stained.

(l) Compare the cones of Pinus, Picea, Abies, Taxodium,
Sequoia, Cupressus, Thuya, and Juniperus.

(7/1) Compare the leaves of Pinus, Picea, Abies, Thuya, and
Juniperus.

LITERATURE OF STROBILOPHYTA.

J. AI. Coulter and C. J. Chamberlain, Morphology of

Gijmnoa perms, Chicago, 1910.
C. S. Sargent, Manual of the Forest Trees of Xorth Amei'ica,

Boston, 1905.

CHAPTER XX

PHYLUM XIV. ANTHOPHYTA

FLOWERING PLANTS

510. In this highest phylum we have the culmination
of the repeated structural advances in earlier phyla.
These plants are mainly modern, although some of the
more primitive forms originated as far back as the
Cretaceous period. It includes more than 132,000 known
species, that is, more than all the other phjda together.

511. The Anthophyta probably were derived from the
Bennettitales among the Cycads. It is certain, at
any rate, that the flower structure of this ancient order
bears a remarkable resemblance to that of the lower orders
of the Flowering Plants.

512. This phylum may be characterized summarily as
follows: Microspores and megaspores borne in flowers
on the leafy, rooted sporophytes. Flowers normally
consisting of more or less cone-like clusters of closed
megasporophylls (carpels) above, and microsporophylls
(stamens) below, and subtended by a perianth. Micro-
spores (pollen-cells) free at maturity, each producing a
one-celled gametophyte, and a tubular antherid, the
latter containing two non-ciliated sperms. Megaspore
retained within the megasporangium (ovule) where it
develops an egg in a reduced archegone and imma-
ture gametophyte. After fertilization the gametophyte
matures ("endosperm"), and the zygote develops into
a cylindrical, leafy sporophyte. The megasporangium

284

THE FLOWER 285

(covered by one or two indiisial coats) now becomes the
*'seed." Upon germination of the seed the sporophyte
escapes, sending its roots downward into the soil, and
its stem upward into the light, bearing green (annual
or perennial) leaves.

513. The tissues of the Flowering Plants show a higher
development than in any of the preceding phyla.
They range, in size and duration, from herbs, a few
millimeters in extent and living but a few days or weeks,
to enormous trees, 50 to 100 meters high and many
centuries old; they live in all kinds of habitats from very
wet to very dry, and from the most protected to the most
exposed situations; accordingly their tissues, especially
those which are supporting and conducting, show all
degrees of variation from very simple to the most com-
plex. The supporting and conducting bundles are here
frequently united into fibrovascular bundles, which in the
higher forms remain ^'open" and are arranged in a cyl-
inder in the stem, thus providing a cambium zone for
the thickening of the perennial stem.

514. Most Flowering Plants are terrestrial and chloro-
phyll-bearing; there are, however, many aquatic and
aerial species, and a considerable number of parasites
and saproph^'tes.

515. A Typical Flower. Flowers have so many par-
ticular forms that it would be impossible to describe
them here, and yet they all conform to a general plan of
structure. In other words, each particular flower shows
a greater or less modification of or departure from what
may be called the typical structure.

516. First of all, every flower has a central stem por-
tion (axis), on which there grow pistils, stamens, and a
perianth. This flower axis may ])e elongated, glo])u]ar
or very short, or it may be flattened into a disk or hollow

286 PHITUM XIV. ANTHOPHYTA

cup (''receptacular cup")- In such a typical flower
as a Buttercup (Ranunculus) this axis is globular.

517. In the Buttercup the globular axis is spirally
studded with many carpels (simple pistils) each consisting
of a closed cavity below (ovar}'), gradually tapering

above to the soft terminal part (stigma).

When young the carpel (megasporophyll)

is an open, flattish, leaf-like structure, but
vert'i^ai pian'^ as it grows larger its margins curve up-
flowrr"''"''^''' ^vard until they meet and grow together.

While the carpel is closing, an ovule grows
out from the base, and becomes enclosed by the carpel
walls.

518. Below the globular head of carpels (pistils) are
several rows of stamens spirally encircling the axis. Each
stamen is a stalked, somewhat flattish structure (micro-
sporophyll), bearing four elongated, parallel sporangia
which contain microspores (pollen). Commonly the
stalk is called the filament, and the four sporangia to-
gether, the anther. The sporangia (pollen sacs) split
longitudinally at maturity and permit the escape of the
pollen.

519. Still lower on the flower axis are two series of
leaf-like structures also spirally arranged, constituting
the perianth. The upper series includes five rounded,
yellow petals, the whole being known as the corolla.
The lower series is made up of five pointed, green sepals,
this being known as the calyx.

520. The purpose of a flower is the production of
seed, and in the Buttercup this is accomplished as
follows:

521. In the ovule (megasporangium) an axial spore
mother cell (archespore) arises, and later this divides
into four young cells (megaspores), but only the deeper

DEVELOPMENT OF THE SEED

28;

lying one of these develops, the others perishing. So the
ovule comes to have one megasporc, which is retained in
the ovule tissues. A little later this megaspore develops
an egg in connection with a greatly reduced archegone,
and a very immature gametophyte, in the following
manner:

The nucleus of the megaspore divides into two, which
move to opposite poles of the megaspore cavity; here
they divide twice resulting in four nuclei at each pole;
then a nucleus from each pole (the so-called polar nuclei)
moves to the center, where they ultimately unite. At
the upper (micropylar) end one of the (naked) cells
becomes the egg, accompanied by two companion cells

Fig. 160.— Ra-
nunculus (pistil
and seed).

Fig. IGl. — Ranunculus (dc-
velopincnt of ovule).

Fig. 1G2.— P(
Icn, tubular anthe-
rid and sperms.

C'synergids"). At the lower end are the antipotlal
nuclei (or cells) . About this time any pollen cell (micro-
spore) that may have fallen upon the soft tissue of the
carpel stigma germinates there producing its most
reduced gametophyte, and a tubular antherid (pollen
tube). The latter penetrates the soft stigma tissues
toward the ovary cavity, carrying down the two sperms.
When the tubular antherid reaches the ovule it enters
the little pore (micropyle) at the summit of the indusial
coats, and penetrates the ovule to the egg where one of
the sperms then unites with the egg, this constituting
fertilization. The zygote now divides repeatedly and

288 PHYLUM XIV. AXTIIOPHYTA

finally takes the form of a verj^ small stem, tipped with
a root at one end, and bearing two rudimentary leaves
at the other. In the meantime the immature game-
tophyte resumes its development as the result of the
union of the second sperm nucleus with the two polar
nuclei to form the so-called endosperm nucleus, which by
its rapid division, with much delayed formation of cell
walls, results in the development of a mass of tissue
surrounding and nourishing the embryo sporophyte
and filling the growing ovule. It is now known as the
endosperm, but it is in reaUty only the belated game-
tophyte.

522. The ovule has now grown much in size. Ex-
ternally its outer coat has become thicker and harder,
•while internally the gametophyte has enlarged and solidi-
fied. A layer of cells at the base of the ovule now
becomes corky and checks the supply of water, drjdng
and hardening the whole ovule, and stopping further
growth. In this final state the ovule is called the
seed.

523. In the Buttercup the carpel enlarges to accom-
modate the growing ovule, but finally its tissues harden
and dry so that when the seed is mature it is contained
within the close-fitting wall of the old carpel and, in this
condition, it finally falls off from the flower axis and is
known as a fruit. The term "fruit," therefore, is here
used for the ripened carpel and its contained seed, and
in flowering plants this is the generally accepted signi-
fication of the term.

524. When these fruits fall to the ground and absorb
moisture, the eml^ryo plant in each seed renews its
growth, getting its food from the endosperm. At
length it is able to push out a root into the soil, and much
later it escapes wholly from seed and fruit and pushes up

WATER PLANTAIN 289

its stem and leaves to the light above ground, and be-
comes an independent plant (sporophyte).

525. The flower structure of the Water Plantain
(Alisma) is essentially the same as that of the Buttercup.
In it the flower axis is less enlarged, the carpels are
fewer, in only a single whorl (i.e. not spirally arranged),
and the stamens are usually six. The rounded, white petals
are in a whorl of three, and the pointed, green sepals are
also in a whorl of three. In the single ovule the develop-
ment of the megaspore and later of the egg is similar
to that in the Buttercup, as is also the growth of the
pollen tube, and the process of fertilization. The
endosperm develops as a belated gameto-

phyte, and the zygote divides repeat-
edly, eventually becoming a small stem
with a root at one end and a single ru-
dimentary leaf at the other. Here this fig. les.— Verti-
embryo sporophyte continues its growth flowl'r'^and^pi^tii)?*
until it has absorbed all of the endo-
sperm: as a consequence it is much larger than in the
Buttercup, and the seed at maturity contains no
endosperm.

526. The structure and behavior of the fruits (ripened
carpels with their contained seeds) are in no wise unlike
those in the Buttercup. So too the germination of the
seed inside of the ripened carpels is similar to what has
been described above. However, as there is no more
endosperm remaining in the seed, the embryo escapes
from it shortly after the root has appeared and pushes
up its stem and leaves to the light above ground, as an
independent plant (sporophyte).

527. A third example of a typical flower ma}^ be seen
in the Strawberry (Fragaria) in which the flower re-
sembles that of the Buttercup and the Water Plantain.

290 PHYLUAI XIV. AXTHOPHYTA

Here the flower axis is globularly enlarged somewhat as
in the Buttercup, and this is covered likewise with many
spirally arranged carpels (megasporophylls). At the
base of this globular body of carpels the axis is flattened
out into a rim or collar, on the margin of which the
stamens grow in several whorls of 5 or 10 each. On
this margin there grow also the five rounded, white petals,
and the five pointed, green sepals, both series in whorls.
The development of the single ovules
and the production of the egg are

(S^

<^=^ essentially the same as in the two

n^P£<^ preceding examples. After fertiliza-
tion the zygote develops into an em-
FiG 164— Vertical plan ^ryo plant cousistiug of a small stem
pistu)!'^^"^ ^°""" ^'""^ with a root at one end and two rudi-
mentary leaves at the other. The
endosperm which appeared in abundance after fertili-
zation is here wholly absorbed by the growing embryo,
so that at maturity the seed contains a large embryo,
and no endosperm.

528. While these changes are taking place in the seed
the carpel enlarges, and the inner layers of the ovary
cells thicken their walls into sclerenchyma, w^hile the
outer layers soften into a juicy flesh (parenchyma). The
ripe carpels are thus very small fruits consisting of a thin
flesh surrounding a tiny stone, which encloses a single
seed. The proper fruits of the Strawberry are these
small ripened carpels. When they fall to the ground the
contained seed germinates by pushing out the root of
the embryo, and since there is no remaining endosperm
this is quickly followed by the escape of the remainder
of the plant from seed and carpel, when it pushes its stem
and leaves into the light, becoming an independent plant
(sporophyte).

STRAWBiaiUY 291

529. Here it should bo said that in the Strawl)erry
while the fruits are developing the gloi)ular flower axis
enlarges very greatly, and its tissues become soft and
juicy, and this is wdiat we eat with so much relish. So
the ''strawberry" as we eat it is not a
fruit properly speaking. It is a thickened
flower axis (stem), covered with the tiny
proper fruits, popularly supposed to ])e

^^^^^' Fig. 165.— Fm-

garia ("straw-

Laboratory Studies. Xote: In connection tnic^fVuit)^'^
with the anatomical studies of special plants
suggested below the student is referred to the general studies
on the cell, tissues, and tissue systems, already taken up in
Chapters I, II, and III respectivel}'.

In working out the following studies the student should have
before him specimens of the three plants named so as to make
comparative studies of the structures represented by them. —

(1) Ranunculus, (2) Alisma, and (3) Fragaria. Where these
cannot be obtained, acceptable substitutions may be made as
follows: for (1) Myosurus, Magnolia, Caltha, Hepatica,
Anemone; (2) Sagittaria; (3) Potentilla, Rubus, Geuni,
Duchesnea.

(a) Make a macroscopic examination of the stems (of the
sporophytes) noting their shape, nodes, branching, bud and
leaf arrangement, and follow with a microscopic examination of
(i) a cross-section to show the location and structure of the vas-
cular bundles, and the distribution of green and colorless
tissues; and (ii) a longisection to show the tissues, epidermis,
hairs and stomata.

{}}) Examine the roots (of the sporophytes) and note whether
there is one main root (tap root) with lateral rootlets, or a
cluster of roots arising from about the same point on the stem.
Note the shape, size and character of the roots and rootlets.
Make cross- and longisections of the younger and older parts
and a longisection of the tip of a root, to study the location and
character of the vascular bundles, the kinds and distribution
of tissues, the origin of lateral roots, the character of the root
cap, etc.

292 PHYLUM XIV. ANTHOPHYTA

(c) Make a similar macroscopic examination of the leaves (of
the sporophytes), noting whether they arise singly at the nodes
("alternate" leaves), or in pairs ("opposite"), or in whorls of
three or more ("whorled"); determine the shape (sometimes
variable), margin, surface, size and variation of the leaf blades;
the length and shape of the petioles; and the shape and position
of the stipules (where present). For the microscopic anatomy
make cross-sections of the leaves and note shape and size of
the epidermal cells, thickness of cuticle, character of hairs,
type and location of vascular bundles (veins), and amount and
location of the forms of parenchyma tissue (the mesophyll)
called "pahsade" and "sponge" parenchyma respectively.
In cross-sections of the petioles note size of intercellular spaces.
Make sections of the blade parallel to the surface, and note the
comparative frequency of the stomata in the upper and lower
epidermis, shape of epidermal cells (and correlation with type
of venation if any), component tissues of the veins and the
course of the latter, etc.

(d) Study the macroscopic structure of the flowers observing
them from above, note that they are radially symmetrical (ac-
tinomorphic). Note the shape of the axis (torus) and how the
flower parts are attached to it, making a longitudinal section if
necessarj^; observe that it does not surround or grow fast to
any floral parts. Note the number and arrangement (in spirals
or whorls) of the megasporophylls (carpels), and observe that
they are free from one another (apocarpous) ; distinguish the
ovar}' and stigma (and style if present); make transverse and
longitudinal sections of carpels and observe number and loca-
tion of the megasporangia (ovules). Count and note arrange-
ment (in spirals or whorls) of the microsporophylls (stamens) ;
examine one carefull}^ and note the filament (stalk) and anther
(cluster of microsporangia); section transversely an unopened
anther and note the four microsporangia; examine the mi-
crospores (pollen) from a mature anther. For the petals note
number, shape, color, size, and particularly their arrangement
(spirals or whorls). Make a similar study of the sepals; note
whether free or united; observe their arrangement with refer-
ence to the petals.

(e) The study of the female gametophyte will require the
use of prepared slides. If possible they should show the devel-
opment from the megaspore mother-cell (archespore) to four

COMPARISON OF FLOWER TYPES 203

megasporcs, thence to the formation of the immature gameto-
phyte (embryo sac) with its egg, arrangement of cells and nuclei
being noted. A slide should also be studied in which a young
sporophyte is developing amid the cells representing the
further growth of the gametophyte (i.e. the endosperm).
The male gametophyte may also be studied in a prepared slide
showing microspores (pollen cells) that have been germinated
so as to show the tubular antherids (pollen tubes) and which
should also show the antheridial nucleus, and the generative
nucleus (or possibly the two non-ciliated sperms derived from

(/) Strictly considered the fruits consist of the modified
carpels containing the ripe seeds, but any accessory modification
of adjacent parts should also be noted. Examine the flowers
when the fruits are mature and note the structure of the carpels,
whether dry or partly fleshy, and dehiscent (i.e. opening to per-
mit the escape of the seeds) or not (indehiscent). Note (in
Fragaria or Duchesnea) the considerable enlargement of the
torus, and consequent separation of the carpels. Note how the
calyx is modified, and whether it remains or falls. Remove a
mature seed from a carpel and note its size and shape, and the
external characters of the seed coat (consisting of the integu-
ments); section it transversely and longitudinally and deter-
mine the presence or absence of endosperm, the relative size
of the embryo, and the number of cotyledons.

530. If now we compare the three flowers described
above it will be seen that they are very similar. Yet
the Buttercup and Strawberry have their petals and
sepals in whorls or series of five each, while they are in
whorls of three each in the Water Plantain. Again in
the former there are tw^o rudimentary leaves (''cotyle-
dons") on the embryo sporophyte, wdiile in the latter
there is but one. Now if we carry our comparison to the
plants bearing the flowers we find other differences. The
first leaves on the little plant in the Buttercup and the
Strawberry as it appears above ground are opposite on the
stem, while in tlie Water Plantain thev are alternate,

294 PHYLU.M XIV. ANTHOPHYTA

and continue to be so throughout the life of the plant.
In the first two the vascular bundles of the leaves are
irregularly netted with one another, while in the Water
Plantain the bundles are quite as markedly parallel.
Also in the stems of the first two there is a more or less
cylindrical arrangement of the vascular bundles, showing
as a ring in a cross-section, while in the Water Plantain
the bundles show little if any cylindrical arrange-
ment, the bundles being more or less scattered through-
out the cross-section.

531. These differences are pretty constant for the
plants related to Buttercups, Strawberries and Water
Plantains respectively, so that botanists have been
led to use them for the division of the Flowering Plants
into two classes. Thus the first two plants and their
relatives constitute the Class Dicotyledoneae, that is the
plants with two cotyledons, while the Water Plantains
and their relatives constitute the Class Monocotyledoneae
that is the plants with one cotyledon. These classes are
of very unequal size, the Dicotyledons containing nearly
109,000 species, while the Monocot-
yledons contain somewhat less than
24,000 species.

632. It is now thought that the
Dicotyledons originated earlier
than the Monocotyledons, and that
the latter must be considered an
^'''■Fiowe;[;.?p[an^s.*^' early offshoot of the former. Yet
the Monocotyledons are by no
means higher in rank than the Dicotyledons as a whole;
they show fewer variations from a common type; they
are more nearly uniform in structure and at no point do
they rise as high as do many of the Dicotyledons. For
these reasons the Monocotyledons are usually discussed

MONOCOTYLEDONS 295

before the Dicotyledons, as a lower class, in sj)ite of the
fact that they appear to have originated from the latter.
The Dicotyledons are an earlier class, but they have
risen higher than the later derived Monocotyledons.

CLASS MONOCOTYLEDONEAE.
The Monocotyledons

533. Cotyledon one; leaves on the stem alternate;
vascular bundles in the stem scattered (as seen in cross-
section), in the leaf blades parallel (''parallel-veined");
perianth whorls mostly ternate (in 3's).

534. There are seven or eight types (orders) of Mono-
cotyledons. The lowest of these (Alifitnatales) is rep-
resented by the Water Plantain, already described.
The others are briefl}^ as follows:

535. Lilies (Liliales). In a Lily the carpels (mega-
sporophylls) have been reduced to three, and these have
grown together into a single pistil (''com-
pound pistil"), in which each carpel
retains its ovule-bearing cavity (i.e. the
pistil is "3-celled"). The stamens (mi-
crosporophylls) are in two whorls of
three each: the petals are three; and the p^^ ig7— Liiium
sepals three. Commonly the perianth is ^vi'rse '^'Vansf ^'^''"'*"
relatively large, and the two whorls of

similar texture. Throughout the flower the members of
successive whorls are alternate.

536. The flower structure here reached appears to be
typical of the great body of the Monocotyledons; and the
structural ]MH'uliarities of the following orders are only
modifications of those of the Lilies.

537. Calla Lilies (Aralcs). In the Calla Lilies the
individual flowers are small, and massed on a thick

296 PHYLU^I XIV. AXTHOPHYTA

stem, commonly diclinous (i.e. stamens and pistils in
separate flowers, monoecious or dioecious) usually sub-
tended V)y a colored leaf (spathe). Each flower is like a
very small lily, but it is very short verti-
cally, and relatively thick ('"squatty")-
The short stamens are usually six, and
the very short-styled pistil is 3-celled (or
^i68"^aiia l-ceflcd). The perianth lobes are short,
pSiKPoThTs).'"^ thick and fleshy or wanting. Through-
out the order (w^hich is largely tropical)
there is a marked tendency toward fleshiness both as to
the plant body (always herbaceous) and the flowers.

538. Palms {Palmales). This order of woody trees
and coriaceous leaves has small flowers resembling those
of the Lilies, but with the parts usually harder and more
parchment-like in texture. In the Coconut the flowers
are separated (diclinous), one kind having functional
stamens (staminate), and the other a functional pistil
(pistillate) . The staminate flower has a perianth of two
ternate whorls, the outer (sepals) shorter than the
inner (petals). The stamens are six in two whorls, and
there is a small, tricarpellary functionless pistil. The
pistillate flower is much larger, and
has a perianth of two ternate whorls,
the sepals and petals being similar to
each other. There are no stamens.
The large pistil is tricarpellary and
should contain a seed in each of the

, 1 , , 1 1 Fig. 169. — Palm flowers

carpels, but two seeds are always (Cocos).

suppressed and their carpellary cavi-
ties are crushed by the growth of the third large
seed. The fruit has much the structure of a plum;
in which the inner part of the ovary wall becomes
stony (sclerenchyma), while the outer part remains

GRASSES

2u:

flesh}' in the plum, but eventually becomes fibrous in the
coconut. The coconut of the northern markets is the
stone of the ovary wall, containing one large seed. This
stone shows its tricarpellary structure by the ridges on
its surface.

539. Grasses {Graminales) . In these plants (includ-
ing several families) the stems and leaves have become
elongated and markedly fibrous and tough. The flowers
are of the Lily type but much reduced, and are clustered
uniformly on slender axes into ''spikelets.'^ In the
Grasses proper (Family Poaceae) each flower is in the
axil of an outer bract (flowering glume, flowering scale,
lemma). The perianth consists of a scale-like, 2-keeled
calyx (palet, palea) representing the two united posterior
sepals (the third being absent) and of two (anterior),
rarely three, small, flesh}^ petals (lodicules). Two whorls
of three stamens each are present, or more often only
the outer whorl. The pistil is tri-
carpellary with two stigmas (very
rarely three stigmas) and there is
but one ovule in the single ovary
cavit3\

540. The Bamboos are large,
woody, hollow-stemmed tropical
grasses, in which the corolla is
trimerous, with the petals (lodicules)
relatively large, the stamens are mostly six, and the
pistil is frequently tristigmatic. In some bamboos the
fruit is externally flesh}', while in others it is like that
in the Brome Grasses.

541. Brome Grass (Bromus) has a hollow herbaceous
stem, and its large spikelets are several flowered; the
corolla is reduced to two small petals (lodicules) ; the
stamens are three, and the pistil has two feathery

Fig. 170. — Grass flowers
and spikelet.

298 PHYLUM XIV. AXTHOPHYTA

stigmas. The ripened pistil tightly encloses the seed,
forming the "grain" or ''caryopsis."

542. Maize (Indian Corn) has a solid (not hollow)
stem and its spikelets are diclinous, the staminate form-
ing a branching inflorescence at the top of the stem, the
pistillate being crowded upon the lateral ''ears," which
terminate short lateral branches, whose numerous
crowded leaf sheaths form the ''husks." The staminate
spikelets are in pairs (one sessile, the other stalked),
and each is two-flowered. The pistillate spikelets are
also in pairs, but here there is only one flower in each.
The styles ("silks") are long, and bistigmatic. The
corn "kernel" is the ripened ovary with its tightly
fitting single seed.

543. The Sedges (Family Cyperaceae) are a family
of widely distributed, somewhat more primitive, grass-
like plants that differ in vegetative structure from the
Grasses in that the leaves are three-ranked, instead of
two ranked, and the stems solid instead of hollow. The
spikelets more often have the bracts spirally arranged,
only a few genera having them two-ranked as in the
grasses. The axillary flower consists of a tri- or a bicar-
pellary pistil, six, or more often three, stamens, and a

perianth of two ternate whorls of
narrow segments, or bristles or want-
ing. The ovary wall is not grown
fast to the single seed.

544. Amaryllis {Iridales). In the

Amaryllis the flower is Lily-like with

Fig. 171.— Amaryllis ^ ^^^^^ dcvclopcd perianth of six equal

petaloid segments (sepals three, petals

three), six stamens, and a tricarpellary, long-styled pistil,

whose ovary is overgrown by the receptacular cup which

carries up the perianth and stamens, so that the ovary

ORCHIDS 299

is said to be ''inferior.'' The nearl}' related Iris has its
sepals reflexed and its petals erect: its stamens are three,
and the three style branches are broad and spreading.
The ovary is inferior as in Amaryllis.

545. Orchids (Orchidales). Here the ovary is in-
ferior as in AmaryUis, but the
perianth is made up of unequal
and unlike segments, the stamens
are reduced to two or one (very
rarely three), and the tricarpel-
lary pistil has but two functional
stigmas in the large majority of ^'^- ■^^fu^^nd or ^[pfP"^^
species.

546. In all the foregoing Monocotyledons the embryos
have one cotyledon, the stems have scattered vascular
bundles, the leaves are alternate on the stems, and paral-
lel-veined, and the perianth whorls are ternate.

Laboratory Studies. Note: In these studies, and those
upon Dicotyledons, the aim should be to bring out the succes-
sive advances in flower structure from the lower to the higher
forms. With this object in view many other details may well
be omitted, but some attention should be given also to special
modifications of the general plant body.

(a) Make cross- and longitudinal sections of onion seeds and
note the seed coats (integuments) enclosing the rather horny
endosperm witliin which lies tlie embrj'o sporoi)hyte. In
similar sections of grains of Indian corn the external coat con-
sists of the ovary wall grown fast to the integuments; the
remainder of the grain consists of endosperm except the elon-
gated or shield-shaped "germ," which is the embryo sporo-
phyte.

(6) Sow a number of onion seeds and grains of Indian corn
and examine one of each every day after germination begins.
In the onion note that the plantlet "backs out" of tlie seed, as
it were, the root first appearing, followed by tlie stem, and last
of all, tlie single cotyledon. In the corn tlie cotyledon remains
in the grain as a si)ecial absorbing organ, so that after the root

300 PHYLUM XIV. ANTHOPHYTA

emerges the leaves appear, the short stem remaining in the seed
for some time before it begins to elongate.

(c) For the lilies use any true lil}' (Lilium) or one of the
following: Erythronium, Yucca, Allium, or TrilHum. By
longitudinal and transverse sections of the flowers show the
single, superior, tricarpellary pistil, the double, trimerous
whorl of stamens, the three petals, and the three sepals.

(d) In like manner examine the small flowers of any culti-
vated ''Calla Lily" (or Arisaema, Pothos, or Acorus), and note
also the thick axis (spadix) on which the flowers are collected,
and the large, subtending bract (spathe). Look for more or
less reduction in the structure of the flowers in some of these
plants.

(e) The lily-like staminate flowers of the Coconut (Cocos
nucifcra) should be studied like those of the true lilies (c) for
general plan, and the pistillate flowers for a considerable modi-
fication of that plan. Add a study of the mature nut. The
perfect flowers of the palmettos (Sabal) are much like the
staminate flowers of the coconut, but the fruits may develop
one, two or three of their carpels.

(/) Examine segments of Bamboo stems for woodiness. Dis-
sect Bamboo spikelets, noting their general structure; study the
flowers with their nearly complete perianth whorls, three or six
stamens, and two or three stigmas.

(g) A further reduction of the flower structure together with
a typical, not much reduced, spikelet structure, may be found
in the herbaceous grasses Bromus, Poa, Triticum, or Avena.
Study the spikelet structure, and then the flowers, in which
both perianth whorls are incomplete, one whorl of stamens is
lacking, and the pistil has but two stigmas. Examine also the
hollow stem (including nodes and internodes) and leaves
(including sheaths and blades).

(h) Examine the solid stem (stalk) of Indian Corn (Zea)
in cross and longitudinal sections, and also the leaves and
sheaths. Dissect a staminate spikelet (from the ''tassel")
with its two tristaminate flowers. Dissect out from a young
"ear" a pistil with its long stjde ("silk"), and reduced and
distorted scales at its base.

(i) Examine a plant of Bulrush (Scirpus) and note arrange-
ment of leaves on the solid (parenchymatous) stem, and the
structure of blade and sheath. Dissect a spikelet (noting its

DICOTYLEDONS 301

spiral arrangement), and study a flower with its tri- or bi-
stigmatic pistil, three stamens and (usually) six perianth bris-
tles. Cyperus differs mainl}- in its two-ranked spikelets, and
absence of perianth bristles.

(j) Study an AmarylUs flower in longitudinal and cross-
sections as in the lily (c). The small, somewhat zygomorphic
flowers of the banana (Musa) may be substituted for the amar-
yllis. Note the absence of one stamen. Study also the ma-
ture fruit (usually seedless) in sections.

(k) Make a similar study of the Iris flower.

(l) For Orchids the Lady's Slipper (Cj^pripedium) should be
studied, and its two stamens grown fast to the tristigmatic
style, one petal slipper-shaped (''lip"), the other two much
like the pointed, rather elongated sepals (two of which are often
united). Note the sticky pollen, and the very numerous, mi-
nute seeds. For this may be substituted the native Orchis, or
Ibidium, or various greenhouse orchids; here the single stamen
is attached to the bistigmatic style, and the petals and sepals
are very variable, one petal ("lip") being always much longer
and more showy.

CLASS DICOTYLEDONEAE.

The Dicotyledons

547. Cotyledons two; leaves opposite on the stem,
later ones opposite or alternate; vascular bundles in
the stem arranged cylindrically (in a ring
as seen in cross-section) ; vascular bundles
in the leaf-blades irregularly netted
C'netted-veined"); perianth whorls
mostly quinate (in 5's).

548. There are two greater types (sub- grams oV ' flower
classes) of Dicotyledons, which are dis-
tinguished by the structure of the flower axis, as follows:

1. Flower axis cyHndrical, spherical, hemispherical or flat-
tened, bearing on its surface the flower parts (perianth, stamens
and carpels) "Axis Flowers" (Axiflorae).

2. Flower axis more or less expanded into a disk or cup,

302 PHYLU.M XIV. AXTHOPHYTA

bearing on its margin the perianth and stamens, subtending
or surrounding the carpels . . " Cup Flowers" (Calyciflorae) .

.\xis Flowers^

549. The Buttercup (Ranunculus) described above is
one of tlie simplest of the Axis Flowers, in which the
flower axis is nearly spherical.

550. The Magnolia flower (Magnolia) is much like a
gigantic Buttercup, the axis being more elongated, but
with essentially the same structural plan. This flower
also has many separate carpels.

551. The common Mallow (Malva) has many carpels
in a single whorl, whose adjacent sides feebly cohere

to form a compound pistil. The many
stamens also cohere below into a tube, but
above they are separate and spreading.
The perianth whorls are dissimilar, the
outer being green and coarser, and the
inner white or bluish, and of soft texture.
All these flower parts are borne on the
small, conical axis.

552. The Wild Geranium (Geranium) has an elongated
axis on the sides of which is borne the whorl of five
feebly adherent carpels. The stamens are similarly
reduced in number (two whorls of 5 each) and the per-
ianth consists of dissimilar whorls, the outer of green
sepals, and the inner of pink or purplish petals.

553. In the Violet (Viola) the axis is very short and
bears on its summit the tricarpellary pistil. The
carpels are united by their margins, making but one

^ For the more systematic arrangement of the plants in this and
the following sub-class the reader is referred to the outline of the
Plant Phyla in Chapter XXII, where the orders and families are
given in what is believed to be their proper sequence.

AXIS FLOWERS 303

pistil cavity, and the ovules grow upon these margins,

i.e. the placentae (the areas from which the ovules grow)

are '^parietal." The stamens are

five, the usually blue petals five and

the green sepals five. In all violets

the front lower petal is large and

spurred at its base, the side petals

are smaller, while the back petals are

larger. There is an unUkeness in the

petals, and the flower is 'irregular."

554. The Mustard flower (Brassica) has reduced the
number of its parts still further, the pistil being bicar-
pellary. Its two carpels are united at their margins, and
the ovules grow upon these margins (parietal placentae) ,
as in the Violet. Here, however, a thin membrane
stretches across from margin to margin dividing the cavity
into two. The stamens are six in two whorls (4 and 2),
the yellow petals four, and the green sepals four. All
of these parts grow upon the very short flower axis.

555. In some Pinks (Lychnis) the five-carpelled pistil
has broken away the partitions between the carpels so

that there is but one pistil cavity,
although the five styles indicate its
structure. The ovules grow upon a
central column, the united placentae.
The stamens are ten (two whorls), the

Fig. i76.-Lychnis. pctals five, and the united green sepals
five (gamosepalous). In some other

pinks the carpels are reduced to two, but the flowers are

otherwise like those of Lychnis.

556. The Primrose flower (Primula) reminds one of the
pinks, but here the five petals have grown together into a
tubular corolla, so that it is spoken of as gamopetalous.
The pistil is composed of several (probably five) carpels,

304

PH^XUIVI XIV. ANTHOPHYTA

closely fused together, and their partitions have broken
away, leaving a central ovuliferous column. The
stamens are five, and they have grown fast to the corolla
tube. The sepals are five, and they have united with one
another for some distance from their bases.

Fig. 177. — Primula.

Fig. 17S.— Phlox.

557. The Phlox (Phlox ) again reminds one of the pinks,
and primroses, to which it is related. The corolla
is gamopetalous, and the five stamens are attached
to the corolla tube. The five sepals are united for some
distance from their bases (gamosepalous). The pistil
is reduced to three carpels, but here the carpel cavities
persist, and in each there are from one to four ovules.

558. In the Petunia (Petunia) the gamopetalous
corolla is more widely open, while the attachment of the
five stamens, and the gamosepaly of the calj^x are
like those of phloxes and primroses. The reduction in

the number of carpels has continued so
that here there are only two, each with
its many-ovuled cavity.

559. The Snapdragon (Antirrhinum) has
intensified the slight irregularity of the
corolla of the Petunia so that it is markedly
2-lipped. Its stamens which are attached
to the corolla are reduced to four, one hav-
ing disappeared. The pistil is bicarpellary, and the seeds
many in each carpel cavity. The calyx is gamosepalous.
560. The Sage (Salvia) carries the preceding modifi-
cations a step further. The gamopetalous corolla is

Fig. 170.
Atitirrhinum.

AXIS FLOWERS 305

strongly 2- lipped, and its attached stamens are reduced
to two, the other three having disappeared. The
bicarpellary pistil contains two ovules
in each carpel cavity. The calyx is
gamosepalous.

In the Salvia and the related mints
we have the highest development of
the Axis Flowers. Compare them with
the Buttercups and Magnolias, and fig.^iso.— Sah
note what changes have taken place.
The axis has been shortened and reduced; the carpels
have been reduced from many and separate to two,
united; the stamens, from very many to two; the petals
from separate (apopetalous) to united (gamopetalous) ;
as well as from regular to irregular; the sepals, from
separate to united.

Laboratory Studies, (a) Examine externally and by cross
and longitudinal sections the seeds of Castor Bean (Ricinus),
Pea (Pisum), and Squash (Cucurbita), noting the character of
the seed coat; the presence of endosperm in Ricinus, its absence
in the other two; and the two cotj^ledons, and between them the
rudiments of the next leaves (the plumule). Where the endo-
sperm is lacking note that the cotyledons are thickened into
storage organs.

(b) Germinate some of the foregoing seeds, examining at
frequent intervals, and note that in the Castor Bean the tliin
cotyledons remain in the seeds (in contact with the endosperm)
for a longer time than in the Squash, but eventually in both they
become green, and function as leaves. In the pea the hemi-
spherical cotyledons are too thick to function as leaves, and
remain in the seed coats.

(c) Examine, in sections if necessary, a flower of the common
Mallow (Alalva), or of Hollyhock (Althaea), or Cotton (Gossy-
pium), noting number and arrangement on the torus of the
united carpels, united stamens, petals and sepals, bearing in
mind the resemblance toiind dilTcrcnces from the general plan
of the Buttercup type of flower.

30G PHYLUM XIV. ANTHOPHYTA

(d) In a similar way and making similar comparisons study
the flower of Wild Geranium (Geranium), or Cultivated
Geranium (Pelargonium).

(e) In the Violets and Pansy (Viola) make out especially
the structure of the pistil and its stigma, the fewer stamens (the
two lower extended backward), and the zygomorphic perianth.

(/) In studying the flowers of Mustard (Brassica) or of
Radish (Raphanus), note particularly the reduction of the
general flower-parts to fours, with the carpels and outer whorl
of stamens further reduced to two.

(g) In the Pinks (using Lychnis, Silene or Dianthus) observe
the disappearance of the septa in the ovary, leaving a free
central placenta, and note the number of styles and number and
arrangement of the stamens, petals and (united) sepals.

(h) For the Primrose flower (Primula) make out the pistil
structure, comparing with that of the Pinks, the central pla-
cental column, the capitate stigma, the five stamens attached
to the tubular spreading corolla, and somewhat united sepals.

(i) Note the similarities and dissimilarities in the structure
of the flower of Phlox as compared with Primula.

ij) Study the funnel-shaped Petunia flower noting especially
the reduction of the carpels to two and the slight zygomorphy
of some of the corollas. The more open flower of Solanum, or
the long-tubular flower of Nicotiana may be substituted for
Petunia,

(k) In the Snapdragon (Antirrhinum) in addition to the
marked zygomorphy of the corolla, note that one of the stamens
(the posterior) has disappeared. Digitahs with similar stamens,
or Pentstemon with four fertile and one sterile stamen may be
substituted for Antirrhinum.

(/) In the flowers of Sage (Salvia) or Horsemint (Monarda)
note the strongly-marked bilabiate structure, and the reduced
number of stamens, as well as the reduction of the pistil to two
bilobed, biovulate carpels. In Dead Nettle (Lamium) the
stamens are four instead of two.

Cup Flowers

561. The Strawberry (Fragaria) described above is
one of the simplest of the Cup Flowers; in fact it is so

CUP FLOWERS

307

c^)

Fig. 181. — Spiraea.

On the margin

simple that at first sight we scarcely recognize it as a Cup
Flower. The expanded rim below the globular axis is
however the beginning of the cup form of the flower axis.

562. The Spiraea or Bridal Wreath (Spiraea) of the
gardens shows a great reduction in the number of carpels,
from many (in the Strawberry) to five
each with several ovules, and with this
we have the disappearance of the globular
flower axis, while the fleshy rim or disk
has now become somewhat cup-shaped,
of the cup are borne the many stamens, usually 20, in
whorls of 5 or 10 each, the five separate, white, rounded
petals, and the five separate pointed, green sepals.

563. The Rose flower (Rosa) show\s a considerable
advance over that of the Spiraea in its general structure
although more primitive as to its carpels and stamens.
The cup is very deep and completely encloses the many
free, biovulate (but one-seeded) carpels. The stamens
are very many (40-50, or more) in whorls of 5 or 10,
attached to the cup margin. The five petals are large and
rounded, and with the pointed, green sepals are attached
to the margin of the cup. After flowering the cups ri-
pen into edible, fleshy ''rose-apples."

Fig. 182.— Rosa.

Fig. 183.— Malus.

564. In the Apple flower (j\Ialus) the cup is still
deeper, narrower, and more fleshy, and it encloses and is
grown to the five, slightly united biovulate carpels.
The many stamens, 20 or more, in whorls of 5 or 10 each,

308 PHYLU:M XIV. ANTHOPHYTA

are borne on the margin of the cup, and liere are found the
five round, pinkish petals, and the five, green-pointed
sepals. As the seeds mature the tissue of the cup enlarges
and softens into the flesh of the ripe apple, while the five
carpels constitute the ''core.'^ Thus in the apple as in
the strawberry the fleshy, edible tissue belongs to the
flower-axis, and not to the proper fruit (the core).
In fact we eat the cup (flower axis) and throw the fruit
(core) away!

565. In the Plum (Prunus) the cup has become deeper
and narrower than in the Spiraea, while the carpels are

reduced to only one with 2 ovules.
The stamens are still many, 20 or
more in whorls of 5 or 10 each, on the
margin of the cup, while the petals

Fig. 1S4. — Prunus. , , . ^ . ,^.

and sepals are as m Spn-aea. Ihe
(free) carpel in ripening softens and thickens its outer
tissues into an edible flesh, while the inner tissues imme-
diately surrounding the seed are hardened into a stone
(sclerenchyma).

566. The Pea flower (Pisum) has a shallow cup, and in
its center a single monocarpellary pistil, as in the Plum
flower. Here, however, instead of two ovules there are
several, so that the pistil becomes elongated.
The stamens on the margin of the cup have
been reduced to ten, and nine of these have
grown together by their filaments, leaving
one free. The five white petals are unlike,
so that the flower is ''irregular." The
back (upper) petal is large and broad (the
'' banner"), the two lateral petals (''wings") are narrower
and hooded, while the two lower petals are still narrower,
united along their lower margins and much curved
upward (forming the "keel"). The green calyx is

CUP FLOWERS 309

gamosepalous and nearl}^ regular. The carpel, which is
somewhat fleshy when young, on ripening becomes dry
and fibrous. This form of fruit is known as a '' legume."

567. It should be noted that the flowers of the plum
and the pea are very much aUke in plan, the greatest
difference being the irregularity of the corolla, and the
fewer, united stamens. The pea represents an immense
group of plants (Bean Family) of 6,000 to 7,000 species,
which appear to have been developed from plum-like
ancestors by their corollas becoming irregular. They
constitute an evolutionary side line in which irregularity
of the corolla C'zygomorphy") has been especially
developed with reference to insect agency in pollination.

568. The flower of the Garden Currant (Ribes) re-
minds one a little of that of the Apple. Its cup is deep
enough to enclose the ovary of the bicar-
pellary pistil. The carpels are united at
their margins, so that there is but one
cavity with two parietal placentae. The ^RibJg.^'
margin of the cup bears the perianth (five

sepals, five petals) and the five stamens. The ovar}"
in ripening thickens and softens its wall, becoming a
many-seeded berry, a portion of which consists of the
thickened cup.

569. The cup of the Evening Primrose
(Oenothera) is ver}^ dee]), not only en-
closing the quadricarpellary ovary, ])ut
extending as a tube much beyond it. The
carpels are wholly united so that the
ovary has four many-seeded cavities. The
eight stamens (in two whorls) are borne
on the edge of the tubular cup, as are
the four large yellow petals antl tlie narrow, greenish
sepals. The ripening ovary becomes hard and dry,

310

PHYLUM XIV. AXTHOPHYTA

Fig. ISS.— Opunti

eventually splitting open to permit the escape of the
seeds.

570. The flower of the Prickly Pear (Opuntia, a cactus)
is in plan much like the preceding, but there are more
carpels (four to eight) : these are united at their margins,

so that there is- but one, many-ovuled
cavity, with four to eight parietal
l^lacentae. The cup is ver}- fleshy, and
bears on its margin and inner face the
very many stamens, many petals and
many sepals. Cactuses are evidently
related to the Evening Primroses, but

are peculiar in being very fleshy, and mostly leafless.

The stems of the Prickly Pear when young bear small

leaves, but these soon dry up and fall off after which the

stems are leafless.

571. The Walnut flowers (Juglans) are small and
diclinous, those with stamens being in drooping, cylindri-
cal, crowded clusters, those with

pistils soUtary or in pairs. Staminate

flowers with a reduced perianth

(calyx), and many short stamens;

pistillate flowers with a bicarpellary Fu-.. is9.— Jugians.

pistil which is wholly covered with

the thick cup, on the margin of which are four reduced

sepals, and as many very small petals. The fruit is fleshy

externally while the single seed is surrounded by a mass

of stone tissue, as in the plum.

572. The flowers of the Oak (Quercus) are much like
those of the Walnut, but the staminate flower clusters
are less dense, and the pistillate flowers are solitary in scaly
involucres (i.e. a collection of several to many crowded
bracts). The staminate flowers have a reduced perianth
(calyx) and six to twelve long stamens, while the single

CUP FLOWERS

311

pistillate flower in each scaly cup-like involucre consists of
a tricarpellary pistil, wholly covered by a thin cup
bearing on its margin the very minute perianth (calyx).
The fruit is a thin, tough-sholled nut C' acorn") usually
with but one large seed. The ripe acorn rests in the
enlarged scaly involucre, now known as the acorn cup.

Fig. 190.— Quercus.

Fig. 101. — Pastinaca.

573. In the Parsnip (Pastinaca) the small flowers are
clustered at the ends of slender spreading rays (in an
umbel). The bicarpellary pistil is covered with the thin
cup, on the margin of which are the five very minute
sepals, the five yellow petals, and the five elongated
stamens. Each carpel cavity contains a single pendulous
ovule. In ripening the bicarpellary ovary becomes much
flattened (dorsally) so that each carpel becomes winged
marginally, and later the two carpels split apart.

574. The flower of the Honeysuckle (Lonicera) has its
bi- or tricarpellary pistil covered with the

deep cup, as in the preceding plants. The
five sepals on the cup margin are very small,
and the five petals are united into a tube
which widens upward to its irregular mar-
gin. The five stamens are attached to the
inside of the corolla tube. On ripening,
the cup and enclosed ovary develop into a
fleshy few-seeded ])erry.

575. In the Sunflower (Helianthu.s) which is one
the lowest members of the highest order {Adeniles)

312 PH^XUM XIV. ANTHOPHYTA

Flowering Plants the small flowers are clustered into
many-flowered heads, from which fact these plants and
their relatives are known as 'X'omposites." The face
or top of the head is flat, and its back is covered with
many spreading, green bracts, constituting the '^invo-
lucre." The face of the head bears the many small
crowded flowers each in the axil of a stiff bract. Those
on the margin (''ray flowers") are
quite sterile, and have large flat
corollas (of five petals united below
into a tube, but "ligulate" above),
while the remainder, ("disk flowers")
produce seeds and have tubular
Fig. i93.-Heiianthus. corolks. Examining one of the
latter we find that the bicarpellary pistil is wholly
covered by the thin cup: the calj^x ("pappus") is re-
duced to two or a few scales : the corolla consists of five
petals united into a tube which is five-pointed at its
summit: the five stamens are borne on the inside of the
corolla tube, and the anthers are united by their mar-
gins into a tube which surrounds the style. The pistil
has a long style which divides above into two recurved
style branches, each stigmatic on its upper surface.
There is but one erect ovule at the base of the single
cavity of the ovary. On ripening the cup and ovary wall
become tough and leathery, and closely surround the
relatively large seed, and this structure is known as an
"achene."

576. The Dandelion flower head (Taraxacum, or Leon-
todon) is in plan much like that of the Sunflower, but here
the flowers all have flat (ligulate) corollas, and all produce
seeds. Each flower consists of a bicarpellary ovary which
is wholly covered by the thin cup, on whose upper margin
is the whorl of many fine bristles (the calyx, or pappus),

CUP FLOWERS 313

and the five-petaled corolla, tubular below, but open

and flat above. The five stamens are borne on the inside

of the tubular part of the corolla, and their anthers are

united around the style, as in the

Sunflower. The ovule also is

quite like that in the Sunflower.

On ripening the upper part of

the cup becomes prolonged into

a slender beak far beyond the

ovary carrying the spreading ^^^ ^^^

calyx whorl upon its summit,

and forming a veritable parachute which readily carries

away the achene and its seed in even the lightest of

breezes.

577. Here it may be remarked that the Dandelion
shows the highest development of flower structure found
in the Anthophyta, and so it may be considered as the
highest plant in the Vegetable Kingdom.

Laboratory Studies, (a) With longitudinal sections of the
flowers of Spiraea make out especially the thickened cup (torus),
the smaller number of several-seeded carpels (five), and the
man}' stamens.

(6) Examine externally and in longitudinal section flowers
and "apples" of any rose (Rosa). Note the great number of
one-seeded carpels (resembling those of Strawberry), and sta-
mens, and the deeply hoUowed out, fleshy, receptacular cup,
comparing with S])iraea.

(c) Making comparisons with the Rose examine in a similar
way tlic flowers and fruit of the Apple (Mains), or Pear (Pirus),
Quince (Cydonia) or Hawthorn (Crataegus), noting especially
the great thickening of the torus and its adherence to the five
united carpels.

(d) Make vertical sections of Plum flowers (Prunus) so as
to show the single free pistil (of one carpel) at the bottom of the
cup, and the many stamens on its margin. Make cross-sections
of growing ])lums (fruits) showing stony cndocarp, and fleshy

314 PHYLUM XIV. AXTHOPHYTA

exocarp. Cherry, Peach or Almond flowers and fruits may be
Bubstitiited for the Plum.

(e) Dissect a flower of the Garden Pea (Pisum) so as to show
the zygomorphy of the corolla, the ten curved stamens, the
single, elongated and several-ovuled pistil. Study developed
pods (legumes) and young seeds. Comi)are the zygomorphic,
shallow-cupped Pea flower with the related actinomorphic
Plum flower. The Sweet Pea (Lathyrus), Bean (Phaseolus),
and Locust (Robinia) flowers are similar to those of the Pea.

(/) Study the flowers and fruits of the Currant or Gooseberry
(Ribes), observing their general resemblance to the Apple, but
noting the bicarpellary pistil with parietal placentae and the
reduced number of stamens.

ig) Compare the flower of Oenothera with that of Spiraea
noting the extreme elongation of the receptacular cup, which
adheres to the united, many-seeded carpels; and the reduction
of the stamens to two whorls.

(h) Study macroscopically the mature sporophyte of a
Prickly Pear (Opuntia), noting the small, narrow, fleshy, short-
lived leaves on the young shoots. In longitudinal and cross-
sections of the flowers make out the fleshy cup surrounding the
compound ovary, and the many spirally arranged stamens,
petals and sepals. Other genera of cactuses show a similar
flower structure, and may be substituted for Opuntia, but the
plants are mostly wholly leafless.

(i) Examine macroscopically a staminate flower cluster (cat-
kin) of the Walnut (Juglans) or Hickory (Hicoria) noting the
crowded, small, many-stamened, apetalous flowers. IMake
cross and longitudinal sections of the pistillate flower showing
the inferior ovary, surmounted by two large stigmas. Make
comparative studies of the fruits and nuts.

if) Examine the staminate flower clusters of the Oak
(Quercus) or Chestnut (Castanea), comparing the several
staminate flowers with those of the preceding (i). As the
leaves are unfolding, or soon after, find near the tips of the
twigs the clusters of two or three pistillate flowers. Dissect
these out from their involucres, and note the calyx borne on
the edge of the thin receptacular cup which adheres to the tri-
carpellary ovary. Examine ripe acorns which are found
single seated in the cup-like involucre, or chestnuts which occur
several together entirely enclosed in the prickly involucre.

SUMMARY OF ANTHOPHYTA 315

(k) In examining the flowers of the Parsnip (Pastinaca),
note first the umbellate inflorescence, and then dissect out a
little flower, noting especially the very small vestiges of sepals.
8tudy the matured fruit noting that it splits vertically into
two halves. The Carrot (Daucus) or Cow Parsnip (Heracleum)
may be substituted for the Parsnip.

(l) Make dissections of the flowers of the Honeysuckle
(Lonicera), Snowberry (Symphoricarpos) or Elder (Sambucus)
and note the few-celled, few-seeded, inferior ovary, very small
sepals, and the somewhat zygomorphic (regular in Sambucus)
corolla of united petals, upon which are borne the few stamens.

(m) Make a macrosco])ic examination of a Sunflower head
(Helianthus), noting the involucre of green bracts on the back,
the marginal row of ligulate flowers (''rays"), and the central
mass ("disk") of tubular flowers. Dissect out and examine
carefully an individual flower of each kind, noting particularly
the calyx (''pappus"), and inferior, bicarpellary, one-seeded
pistil. Dissect a mature achene ("seed"). Rudbeckia or
Coreopsis maj^ be substituted for Helianthus.

(n) Study the flower-head of the Dandelion (Taraxacum
or Leontodon), comparing it with that of the Sunflower. Note
the following points of difference: the development of the cor-
ollas of all flowers into ligules, fertility of all flowers, develop-
ment of calyx (pappus) as a whorl of numerous fine bristles,
and absence of bracts subtending each flower. Examine a
fruiting head. Note the presence of latex in the plant. Wild
or cultivated Lettuce (Lactuca) may be substituted for the
Dandelion.

Summary of Anthophyta

578. Looking ])ack over the Flowering Plants it is
seen that their simpler forms are like those of Buttercups
and their near relatives, and that from this primitive
type there have arisen three diverging phyletic groups.
One of these (the Monocotyledons) begins with the
Water Plantains, and culminates in the Orchids: another
(the Axis Flowers) begins with the Buttercups and
passing through various intermediate^ forms culminates in

316 PHYLUIvI XIV. AXTHOPHYTA

the flints: while still another (the Cup Flowers) begins
with the Strawberries and culminates in the Sunflowers
and Dandelions. It will be noted furthermore that the
Axis Flowers and Cup Flowers agree in regard to their
cotyledons, arrangement of leaves, vascular bundles of
stems and leaves, and perianth whorls, causing us to
consider them as two subdivisions of a common class, —
Dicotyledons, — coordinate with the Monocotyledons.

579. Taking a longer look backward it may be seen
that in the Anthophyta we have the culmination of the
evolutionary tendencies manifested in the main line of
plant progress over which we have travelled: — from
Myxophyceae to Chlorophyceae, thence to the lower
Bryophyta, and from these to the Old-fashioned Ferns
(Pteridophyta) and from these again to the Seed Ferns
and Flowering Plant Ancestors (in Cycadophyta), from
which the step is relatively short to the simpler Flowering
Plants. It follows that but five of the preceding phyla
have contributed to the development of the Flowering
Plants, and that the eight remaining phyla are side
branches whose developmental accretions added nothing
that continued to the Flowering Plants. These five
contributing phyla contain somewhat less than one-fourth
of the non-flowering plants, and yet it may be doubted
whether even more than one-fifth of these again con-
tributed in any way to the structure of the Flowering
Plants. So we may say that of the approximately
100,000 plants in the thirteen phyla preceding Antho-
phyta, probably no more than 5,000 represent structures
in any sense ancestral.

580. It will be instructive to enumerate the greater
steps in this progressive development from the Myxo-
phyceae to Anthophyta, as follows:

STEPS IN DEVELOPMENT 317

Myxophyceae, contributed first of all the cell unit, to which

they added a definite nucleus, and definite plastids.
Chlorophyceae, carried the plant body from the single cell

to the rooted, branched fdament,
— added ciliated gametes,

— carried generation homisogamy to heterogamy,
— carried the result of fertihzation from the simple

zygote to the simple fruit.
Bryophyta, developed the plant body as a cell 77iass,
— developed the sporophyte from the simple fruit,
and so brought in an obvious alternation of generations,
and with it terrestrial life,
with which came the beginning of supporting tissues

(woody strands),
and simultaneously the beginning of conducting tissues

{vascular strands).
Pteridophyta, reduced the gametophyte to a smaller and

short-lived structure,
— developed an independent sporophyte by the production

of roots and leaves;
— differentiated isospores into heterospores; (microspores

and megaspores);
— perfected the supporting tissues (woody stratids);
— perfected the conducting tissues (vascular bundles).
Cycadophyta, developed special sporophylls for megaspores

( megasporophylU) ,
— retained the megaspore in the megasporangium,
— which became covered ])y an indusium (integument),
— reduced the archegonial gametophyte to a dependent

structure retained by the megasporangium,
— which led to the development of the seed,
— developed special sporophylls for microspores (micro-

sporophylls),
— developed tubular antherids,
— reduced the sperms to two,

— aggregated the sporophylls into a cone (strobilus);
— developed the beginnings of the perianth,
— produced an erect, long-lived stem,
— developed fihro-vascular bundles,

and modes of thickening the stem.

318 PHYLUM XIV. ANTHOPHYTA

Anthophyta, developed inicrosporophylls into stamens,
— reduced the sperms to non-ciliated cells,
— developed megasporophylls into jnstils,
— developed a proper perianth,
— perfected fihrovascular bundles,

arranging them in a cylinder,
— perfected the thickening of the stem,

by fihrovascular and interfascicular cambium,.

LITERATURE OF ANTHOPHYTA

J. M. Coulter and C. J. Chamberlain, Morphology of

Angiosperms, New York, 1903.
N. L. Britton and Addison Brown, Illustrated Flora of the

Northern States and Canada, Second Edition, New York,

1913.
N. L. Britton, Manual of the Flora of the Northern States

and Canada, Second Edition, New York, 1905.
B. L. Robinson and M. L. Fernald, Gray's New Manual of

Botany, New York, 1908.
J. K. Small, Flora of the Southeastern United States, Second

Edition, New York, 1913.
J. M. Coulter and Aven Nelson, New Manual of Botany

of the Central Rocky Mountains, New York, 1909.
F. E. and E. S. Clements, Rocky Mountain Flowers, New

York, 1914.
T. C. Frye and G. B. Rigg, Northwest Flora, Seattle, 1912.
L. R. Abrams, Flora of Los Angeles and Vicinity, Stanford

University, 1911.

CHAPTER XXI
SO:\IE SPECIAL ADAPTATIONS

681. The plant body (sporophyte) of the Anthophyta,
while standardized as to general plan, is very plastic as
to the details of its structure. This plasticity has enabled
it to respond so fully to various needs as to bring about
marked changes in its size, form, proportions of parts,
surface characters, etc. Only the more important of
these need be noticed here.

582. For particular purposes some parts of the plant
body may have a special development, as the thorny (not

Fig. 195. — Standard Fig. 190. — Runners, above
plant (Anthophyta). and under ground.

Fig. 197 — Corm, bulb,
and root.

parenchymatous) leaves of the Barberry, the thorny
leafless branches of the Honey Locust (both protective),
the runners of the Strawberry above ground, and the
under-ground rootstocks of the Canada Thistle (both for
vegetative reproduction) .

583. Many plants store up food substances in some
part of the i)lant body, resulting in considerable changes
in form. Thus the lower part of the stem may be
spherically enlarged, as in the so-called corms of Arisaema
and Gladiolus. In the bulbs of iiuiiiy plants, as the

319

320 SOME SPECIAL ADAPTATIONS

Onion, and Hyacinth, the food substances are stored in
the thickened leaf bases. Turnips, radishes, dahUas,
etc., store their food substances in tlieir roots which are
accordingly much thickened. Other plants develop
the ends of their rootstocks into storage structures, as
the tubers of the potato and Jerusalem Artichoke; while
again some thick leaves, as those of the Century Plant
(Agave), and many other Monocotyledons, are storage
organs.

584. Habitat. Most flowering plants grow with their
roots in moist (not wet) soil, with their leaves in air of
moderate humidity. Stated otherwise we may say that
under these conditions the great majority of flowering
plants developed the forms which they have. So when
we say that such plants are '^mesophytes" we are merely
stating the fact that the majority of plants live under
these quite similar conditions. And these have the usual
leaves and stems. A much smaller number have been
able to live in drier soil and drier air, their leaf surfaces
being smaller or wanting, their epidermis thicker, their
tissues harder, and these we have denominated ''xero-
phytes," literally, dry plants. On the other hand some
plants have been able to live partly or wholly in the
water. Their stems and leaves are weak and soft and
their submerged leaves reduced (dissected). Such plants
we have called '^ hydrophytes" (i.e. water plants).
Other adaptations still less marked have been noticed, as
the ^'halophytes" of salt waters or soils, the ''ruderal
plants" of waste places, ''shade plants," ''sun plants,"
etc.

585. Here may be noted the mocUfications of the
plant body following the acquisition of a parasitic habit.
These are well illustrated in the common Dodder (Cus~
cuta, a climbing vine related to the Morning Glories)

AXKMOPIIILY

321

Fig. 198.

Morning glory

and dodder.

which has lost its leaves, its ^reen color, and its firm stem
structure. The Broom-rapes {Orohanchaceae) likewise
have bract-like, chlorophyll-less leaves.
And so the saprophytic Indian Pipes {Mon-
otropaccae) show a similar reduction.
Somewhat allied to these modifications
are those in the case of the so-called In-
sectivorous plants where the leaves are modi-
fied into pitchers, or other structures for the
capture or digestion of insects.

586. In their evolution from the primitive type of
flower to the more derived structures the Flowering
Plants have produced a multitude of forms of flowers
many of which show themselves extremely well-fitted for
certain very definite conditions. It is in connection
with the methods of pollination that the greatest varia-
tion is shown. It seems certain that the primitive flowers
were dependent, as are the vast majority of flower types
now, upon the aid of insects in pollination. However,
very numerous groups of Flowering Plants have given
up this so-caUed ''entomophilous" habit, and are polli-
nated by the wind (''anemophilous"). Such
flowers are usually marked by certain charac-
ters in common, viz. the abundance and
lightness of the pollen, the occurrence of the
staminate flowers in hanging clusters, "cat-
kins" (easily swung by the wind, as in the
Walnut, Oak, etc.) ; or with the branches or
inflorescence slender and swinging easily in
the wind (as in various grasses); the styles
and stigmas are usually very large, thus exposing more
surface on which the chance pollen grains may be caught;
usually too the pistils have but one, or very few ovules,
for each ovule requires a pollen grain for its fertilization

322 SOME SPECIAL ADAPTATIONS

and the chances are fewer for a multiple pollination by
wind-blown pollen. Wind-pollinated flowers are usually
small and dull in color.

587. On the contrary the insect (and bird) pollinated
flowers are usually bright colored (and it has been found

that many insects are attracted long dis-
tances by bright colors). They are usually
large enough to be easily visible, or if
small are bunched in large, conspicuous
masses (as in Elder). If not showy them-
FiG. 200.— Dog- selves they are often bordered by showy
leaves (as in Snow-on-the-Mountain Eu-
phorbia margi7iata), or some of the flowers are con-
verted into showy structures at the sacrifice of their
sexual function (e.g. marginal flowers of some Dog-
woods). In addition to these it is usual for entomophi-
lous flowers to emit perfumes of various kinds, some
of which are perceived by insects at great distances.
Some of these are very unpleasant to man, but are
attractive to certain insects, e.g. StapeUa, whose car-
rion-like odor is attractive to carrion insects.

588. Within the flowers are developed the secretory
glands which secrete a sugary liquid. Attracted by
color and odor the insects fly ito the flowers and seek out
this nectar which they imbibe. In
so doing they come in contact wdth
the stamens, and become powdered
with pollen, and later touch the t. „^, ^ , .

. ., 1 • 1 1 ^'°- 201.— Regular (ac-

piStll to which the pollen is trans- tinomorphic) and irregular
^ ^ (zygomorphic) flowers.

f erred. In flowers with many
stamens and pistils the nectaries are usually several
in all the radii of the flower, and the insect in visiting
will manage to become thoroughly covered with pollen
and to put it on the summit of the stigma. In many

ZYGOMORPHY AND DIIVIORPHISAI 323

flowers, however, the stamens are few, and the pistils
few or only one. Here often the flowers become one-
sided (zygomorphic), of such a structure that access to
the nectary can be obtained only at such a point that
polhnation is rendered all the more certain. In this
connection adaptation of flowers to certain insects is
very apparent. Thus certain
orchids are of such a structure
that only certain butterflies or bees
can reach the nectary, and in so
doing pollinate the flowers. Other W _^_ ^
insects either cannot reach it at I' \^ ''^^^^^:^^='
all, or in so doing fail to remove ,, ono t> *

' ^ Fig. 202. — Proterogvnoua

the pollen or transfer it to the (Plantago) and proteran-
'^ drous (Llaytonia) flowers.

stigma.

589. In connection with entomophily it was early ob-
served that many flowers were of such structure that self-
fertilization (i.e. polhnation with pollen of the same
flower) is impossible. Thus in the majority of such
flowers the pollen is all shed before the stigma is recep-
tive (proterandrous), or much less frequently the stigma
passes the receptive stage before the pollen is set free
(proterogynous). In some plants the
flowers are ''dimorphic," i.e. on certain
individuals the stamens are at one level
and the stigmas at a different level in the

Fig. 203.— Di- , ., . ...

niorphic flower same flower, while m other mdividuals of

(Primula). ' .

the same species they occupy the reverse
positions. An insect visiting the flowers of the first
plant, becomes pollinated at a definite part of its body
which does not come into contact with the stigma at
all in that same type of flower. When, however, it
visits the other type of flower, the stigma is at tlie
level of the stamens of the first type, and it comes in

324 SOME SPECIAL ADAPTATIONS

contact with the pollen-bearing portion of the insect's
body. It has been shown that even artificial pollination
of flowers of these species with pollen from the same type
of flower is unfavorable to seed production, this occurring
best when the pollen comes from the other type.

590. A few plants (e.g. the common Dandelion, and
some of the Hawkweeds) whose structures would indi-
cate entomophily, and whose near relatives are so polli-
nated, seem to have dropped the habit of requiring polH-
nation, and the eggs develop without fertilization. Thus
we find a loss of sexuality in these plants (apogamy,
parthenogenesis) .

591. In their methods of seed distribution also, the
Flowering Plants show great variation. Some seeds are
let fall directly from the parent plant, and are of such
structure that they are not suited to any special means of
distribution. The result is a crowding of the young seed-
lings, and competition between them and with the parent
plant. Such plants do not extend their range rapidly.
On the other hand a great proportion of the Flowering
Plants have structures, either of the parent plant or of

the seed, that fit the seeds for special
modes of distribution. Depending
upon the habitat, and means of
seed distribution the spread of such
plants may be more or less rapid.

592. The chief agents in seed
distribution are (1) water, (2)
^'''' ^athTcoiSebur.^^'^^'''' ^iud, (3) auimals (including man),
and (4) mechanical expulsion.
Adapted to distribution by water are seeds (or fruits)
with an abundance of corky or woody tissue which
buoys up the seed, and, in the case of ocean-borne
forms (e.g. coconut), protects the seed from mechanical

SEED DISTRIBUTION 325

injury by the pouncliiig of the surf. The abundant
springing up of many kinds of weeds (great ragweed,
etc.), on flooded lands after the water has subsided
is due to water-borne seeds. Many of the seeds so
transported are the small rounded seeds that are washed
along in the mud (not floating). Structures that enable
the wind to transport seeds are almost innumerable.
Chief among them are the long hairs on seeds and fruits
(thistle, milkweed, cottonwood); flattened extensions
into wings, which may be more or less spirally warped
(elm, maple, ash, catalpa) ; the inflorescence (tickle grass,
sycamore), or the whole plant (Russian thistle, and other
'* tumbleweeds"), both rolled over the ground in the wind,
dropping the seeds as they go.

593. Distribution by animals is accomplished in many
ways. Some seeds and fruits are provided with hooks or
prickles which become caught in the hairs of the passing

<5)

Fig. 205. — Spanish needles, cherry, acorn. Fia. 206. — Touch-me-not.

animal and so provide for the carrying of the seed (e.g.
cocklebur, sand-bur, stickseed, Spanish needles, ])ed-
straw, burdock, etc.). Other seeds are edible and so are
sought by various animals which eat many but drop some
in transporting them, or bury them for future consump-
tion, thus planting them (e.g. acorns, achenes of sun-
flowers, nuts, etc.). Probably the development of fleshy
fruits, however, is the one that most perfectly provides
for seed distribution. Animals of all kinds gather and
eat the fruits, and in doing so drop the sclerenchyma-
enclosed seeds (plums, cherries, etc.), or eat the fruits

326 SOME SPECIAL ADAPTATIONS

with the seeds, the latter passing through the body un-
harmed (strawberries, grapes, and most berries). Many-
small, rounded seeds dropping to the earth are widely
distributed by animals to whose feet the earth containing
them clings, thus being carried long distances. Such are
the majority of the common weeds of the roadsides,
barnyards, and waste places (pigweeds, lamb 's quarters,
purslane, knot-grass, etc.). Of special interest, but rela-
tively infrequent, are the plants that have fruits that
dehisce explosively so that their seeds are flung compara-
tively long distances, thus placing them where they do
not compete with their parents (OxaHs, touch-me-not,
various vetches, wild geranium, etc.).

REFERENCE BOOKS

W. F. Ganong, The Living Plant, New York, 1913.

F. E. Clements, Plant Physiology and Ecology, New York,

1907.
H. C. CowLES, Ecology (in Textbook of Botany by Coulter,

Barnes and Cowles) Chicago, 1911.
Hermann Muller, The Fertilization of Flowers, Engl. Ed.,

London, 1883.
Paul Knuth, Handbook of Flower Pollination, Engl. Ed.

Oxford, 1906-9.
Eng. Warming, Oecology of Plants, Engl. Ed., Oxford, 1909.

CHAPTER XXII
THE PLANT PHYLA

WITH THEIR CLASSES, ORDERS, FAMILIES AND IL-
LUSTRATIVE GENERA

The Plant World is here regarded as readily separable into
fourteen Phyla (often called ''Branches" or "Divisions").
These are subdivided into Classes, and these again into Orders,
and the latter into Families. The latest enumeration of the
species of plants shows that we now know approximately a
quarter of a milUon recognizable forms. These numerical data
may be shown concisely in tabular form as follows:

Classes Orders Families Species

1. Myxophyceac . .

2. Chlorophyceae..

3. Zygophyceae . . .

4. Siphonophyceae

5. Phaeophyceae. .

6. Rhodophyceae .

7. Carpomj'ceteae.

8. Bryophyta

9. Pterido])hyta. . .

10. Calamoi)hyta.. .

11. Lepidophyta. . ..

12. Cycadophyta. . .

13. Strobilophyta...

14. Anthophyta. . . .

Total

145

300

123

About

2,020

About

1,090

About

7,000

About

1,26a

About

1,030

About

3,050

About 64,000

About 16,600

About

3,800

About

700

About

140

About

400

About 132,500

683 About 233,614

327

328 THE PLANT PHYLA

KEY TO THE PHYLA OF PLANTS

In this key onl}' the general or typical characters are indi-
cated, and it must be reincml)ered that many variations
("exceptions") occur in every phylum.

A. Cells typically with poorly developed nuclei and chromato-

phores; reproducing by fission and spores;
mostly blue-green, brown-green or fuliginous
(or colorless), never chlorophyll green.
L Unicellular to filamentous plants.

Phylum 1. IMi'xoPHYCEAE.

B. Cells typically with well-developed nuclei and chromato-

phores (chloroplasts) ; reproducing by fission
and spores, and mostly by gametes also;
chlorophyll-green, sometimes hidden by other
coloring matter (or colorless).
L Plants usually of but one obvious generation, typi-
cally aquatic.

a. The fertilized egg developing into a z3'gote only.

1. Unicellular, to filamentous, manj^-celled plants

(rarely a plate of cells); isogamic to hetero-
gamic, one or both gametes ciliated.

Phylum 2. Chlorophyceae.

2. Filamentous many-celled plants, mostly break-

ing up early into single cells; isogamic, gam-
etes not ciliated. Phylum 3. Zygophyceae.

3. Tubular filamentous (or saccate) coenocytic

plants, usually attached basally by rhizoids;
isogamic to heterogamic.

Phylum 4. Siphonophyceae.

4. Cellular filamentous (rarely unicellular) to

massive plants, attached basally b}^ rhizoids
(or roots); isogamic to heterogamic; the
green color hidden by a brownish pigment.
Phylum 5. Phaeophyceae.

b. The fertilized egg developing into a spore-fruit.

L Cellular filamentous to massive holophytic
plants, attached basally by rhizoids (or
roots); heterogamic; the green color mostly
hidden by a red or j)urple pigment.

Phvlum 6. Rhodophyceae.

KEY TO THE PH\XA 329

2. Cellular filaiiieiitous hystcrophytic plants,
often much tlep;enerated, without chloro-
phyll; heterof2;aMiic.

Phylum 7. Carpomyceteae.
II. Plants of two obvious, alternating generations, tyj)-
ically terrestrial.

a. Gametophyte generation larger, and longer-lived

than the dependent sporophj^te generation.
1. Gametophytes from prostrate and thalloid to
erect leafy shoots; sporophytes globose to
cylindrical or stalked, neither expanded nor
rooted.

Phylum 8. Bryophyta.

b. Gametophj^te generation smaller and shorter-

lived than the independent sporophyte
generation.

1. Both generations mostly holophytic, independ-

ent of one another.

(a) Gametophytes typically flat and thal-
loid, normally attached by rhizoids,
mostly monoecious; sporophytes consist-
ing of large-leaved, solid stems, which
are rooted below.

Phylum 9. Pteridophyta.

(b) Gametophytes typically fiat and thal-
loid, normall}^ attached by rhizoids,
mostly monoecious; sporophytes con-
sisting of mostly solid, cylindrical,
jointed and fluted stems, bearing small,
whorled leaves at the nodes, and rooted
below. Phylum 10. Calamophyta.

(c) Gametophytes typically tubular or glo-
bose, with few rhizoids or none, often
dioecious; sporophytes consisting of
solid, cylindrical, continuous (not joint-
ed) and not fluted stems, bearing small
spirally arranged (or opposite) leaves,
and rooted l)elow.

Phylum 11. Lepidopiiyta.

2. Gametophytes hystcrophytic, dependent upon

and nourished by the 8j)oroi)hyto.

330 THE PLANT PHYLA

(a) Sporophylls open, ovules and seeds
naked (gymnospermous).

(1) Gametophytes dioecious; sperms cili-
ated and motile; sporophytes pro-
ducing microspores and megaspores
in spiral or whorled sporophylls, or
these aggregated into cones.

Phylum 12. Cycadophyta.

(2) Gametophytes dioecious; sperms not
ciliated, not motile; sporophytes
with sporophylls in cones.

Phylum 13. Strobilophyta.

(b) Sporophylls closed, ovules and seeds

covered (angiospermous).
(1) Gametophytes dioecious; sperms not
ciliated, not motile; sporophytes
with sporophylls in flowers.

Phylum 14. Anthophyta.

In the following systematic enumeration many of the families
are merely named in their sequence, without any characteriza-
tion or examples. Moreover the characterizations of all groups
are necessarily very brief and general. The examples cited are
of the more conmion genera, or those of particular interest to
the student.

Phylum I. MYXOPHYCEAE. The Slime Algae

Usually blue-green, poorly developed cells, or filaments

Class 1. ARCHIPLASTIDEAE (Cyanophyceae). "Blue
Greens." Without nuclear mem-
brane. (Sp. about 2,000.)
Order Coccogonales. Green or greenish; unicellular.
Family 1. Chroococcaceae. Cells rounded. — Chroo-

coccus, Gloeocapsa, IMerismopedia.
Family 2. Chamaesiphonaceae. Cells elongated. —
Chamaesiphon.
Order Hormogonales. Mostly green or greenish; fila-
mentous.
Family 3. Oscillatoriaceae. No heterocysts. — Oscil-
lator ia, Lyngbya.

MYXOPHYCEAE 331

Family 4. Nostocaceae. Heterocysts intercalary
prominent. — N ostoc, Cylindrosper
mum.

Family 5. Scytonemataceae. Heterocysts intercal-
ary, not prominent. — Scytonema.

Family (J. Rivulariaceae. Heterocysts basal. — Rivu-
laria.

Family 7. Camptotrichaceae. Xo heterocysts. —
Camptothrix.

Family 8. Stigonemataceae. Heterocysts intercal-
ary, not prominent; cells in more than
one row. — Stigonema.
Order Bacteriales. The Bacteria. Not green; typically
filamentous, but becoming few- or
one-celled by the solution of the fila-
ment. Related to the foregoing blue-
green plants.
Sub-order Thiobacteria. With sulphur granules in the
cells.

Family 9. Beggiatoaceae. Cells in motile filaments,
colorless. — Beggiatoa.

Family 10. Rhodobacteriaceae. Cells single, or in
colonies; red, rose or violet colored. —
Chromatium.
Sub-order Eubacteria. Without sulphur granules in the
cells.

Family 11. Phycobacteriaceae. Cells in straight,
motionless filaments. — C renothrix,
Sphaerotilus.

Family 12. Spirillaceae. Cells in spirally coiled, mo-
tile filaments. — Spirillum, ]\licrospira,
Spirochaete.

Family 13. Bacteriaceae. Cells mostly single, elon-
gated, straight. — Bacterium (no flag-
ella), Bacillus (surface flagella),
Pseudomonas (polar flagella).

Family 14. ]\Iyxobacteriaceae. Cells elongated, with-
out flagella, growing in definite, slimy
colonies. — Chondromyces.

Family 15. Coccaceae. Cells mostly single, spherical.
— Micrococcus, Streptococcus, Sar-
cina.

332 THE PLANT PHYLA

Class 2. HOLOPLASTIDEAE. With nuclear menihrane.
(Sp. about 20.)
Order Glaucocystales. Dividing in one plane.
Family 16. Glaucocystaceae. — Glaucocystis.

Phylum II. CHLOROPHYCEAE. Tlie Simple Algae

Normally chloro])liyll-green, with well-developed single cells,
or filaments. (Here restricted to two
classes of green algae).

Class 3. PROTOCOCCOIDEAE. Green Slimes. Unicellu-
lar. (Sp. about 450.)
Order Palmellales. Cells not in colonies.

Family 1. Protococcaceae. No zoospores. — Proto-

coccus, Trochiscia, Crucigenia.
Family 2. Chlorococcaceae. With zoospores. — Chloro-

coccum, Tetraspora. Botryococcus.
Family 3. Synchytriaceae. Colorless parasites. —
Olpidium, Synchytrium.
Order Coenobiales. Cells in colonies.

Family 4. Hydrodictyaceae. Vegetative cells not cili-
ated. — Scenedesmus, Hydrodictyon.
Family 5. Volvocaceae. Vegetative cells ciliated. —
Gonium, Pandorina, Volvox. (Ani-
mals!)
Class 4. CONFERVOIDEAE. Confervas. Filamentous, or
a plane. (Sp. about 640.)
Order Microsporales. Unbranched.

Family 6. Microsporaceae. — Microspora.
Order Schizogoniales. Unbranched.

Family 7. Prasiolaceae. — Prasiola.
Order Ulvales. Plant a plane or tube.

Family 8. Ulvaceae. — Ulva, Enteromorpha.
Order Chaetophorales. Usually branched. Zoospores
and ciliated gametes.
Family 9. Ulotrichaceae. Unbranched. — Ulothrix.
Family 10. Chaetophoraceae. Branches attenuated
into hairs. — Draparnaldia, Chaeto-
phora.
Family 11. Alicrothamniaceae. Scarcely attenuated,
no hairs. — Microthamnion.

ZYGOPHYCKAE 333

Family 12. Trent epohliaceae. Scarcely attenuated,

no hairs. — Trent cpohlia.
Family 13. Herposteiraceac. Scarcely attenuated,

with hairs. — Herposteiron.
Family 14. Cylindrocapsaceae. Unbranchcd, hetero-

gamic. — Cylindrocapsa.
Family 15. Oedogoniaceao. Unbranched or branched,

heterogamic. — Oedogonium.
Order Coleochaetales. Branched, fusing into discs.
Family 16. Coleochaetaceae. Minute disk-like

plants. — Coleochaete.

Phylum III. ZYGOPHYCEAE. The Conjugate Algae

Chlorophyll-green sluggish filaments, often fragmenting into
single cells

Class 5. CONJUGATAE. Typically filamentous, green
plants, with cellulose walls. (Sp.
about 1,300.)
Order Zygnematales. Pond Scums. Filamentous.

Family 1. Mesocarpaceae. Chloroplast single, long,

axial. — Mougeotia, Gonatonema.
Family 2. Zygnemataceae. Chloroplasts two, short,

axial. — Zygnema, Zygogonium.
Family 3. SpirogjTaceae. Chloroplasts 1 to 9, parie-
tal, spiral. — Spirogyra.
Order Desmidiales. Desmids. Filaments usually early
fragmenting into single cells.
Family 4. Desmidiaceae. Unbranched filaments. —
Genicularia, Hyalotheca, Desmidium.
Family 5. Closteriaceae. Cells solitary, elongated.

— Clostcrium, Pcnium.
Family G. Cosmariaceae. Cells solitary, broad, flat-
tened. — Cosmarium, ^licrastcrias.
Class 6. BACILLARIOIDEAE. The Diatoms. Brownish-
green plants, with silicified walls.
(Sp. about 5,700.)
Order Eupodiscales. Round Diatoms. Filaments com-
monly cylindrical, usually fragmented
into single cells.

334 THE PLANT PHYLA

Family 7. Coscinodiscaceae. Cells short, ends not
ribbed. — Coscinodiscus.

Family 8. Actinodiscaceae. Cells short, ends rib-
bed. — Actinodiscus, Arachnoidiscus.

Family 9. Eupodiscaceae. Cells short, ends with
"eves." — Eupodiscus, Actinocyclus.

Family 10. Soleniaceac; 11, Chaetocerotaceae; 12,
Biddulphiaceae; 13, Euodiaceae; 14,
Anauliaceae; 15, Rutilariaceae.
Order Naviculales. Flat Diatoms. Filaments flattened,
usually fragmented into single cells.

Family 16. Tabellariaceae. Mostly filaments, cells
short, rectangular in side view. —
Grammatophora, Rhabdonema.

Family 17. Meridionaceae; 18, Fragilariaceae.

Family 19. Naviculaceae. Cells single, end with
central slit. — Navicula, Amphipleura.

Family 20. Bacillariaceae; 21, Surirellaceae.

Phylum R'. SIPHONOPHYCEAE. The Tube Algae

Normally chlorophyll-green filaments composed of one or more
coenocytes

Class 7. VAUCHERIOIDEAE. Lower Tube Algae. Fila-
ments septate or tubular. (Sp. about

400.)
Order Cladophorales. The Cladophoras. Septate, the

segments coenocytic.
Family 1. Cladophoraceae. Unbranched or branched,

isogamic. — Cladophora, Pithophora.
Family 2. Sphaeropleaceae. Unbranched, hetero-

gamic. Sphaeroplea.
Order Siphonales. Green Felts. Tubular, irregularly

branched, chlorophyllose.
Family 3. Phyllosiphonaceae. Endophytic. — Phyl-

losiphon.
Family 4. Codiaceae. Filaments compacted into a

large plant-body. — Codium, Peni-

cillus.
Family 5. Vaucheriaceae* Filaments single, free. —

Vaucheria.

SIPHONOPIIYCEAE 335

Class 8. PHYCOMYCETEAE. Tube Fungi. Lower Fungi.
Filaments tubular, mostl}- irregularly
branched, chlorophyll-less. (About
400 species.)
Order Saprolegniajles. Typically aquatic; mostly sapro-
phytic ; forming zoospores in zoospor-
angia.

Family 6. IVIonoblepharidaceae. Aquatic sapro-
phytes; antherids producing unicili-
ated sperms. — Monoblepharis.

Family 7. Saprolegniaceae. Water Molds. Aquatic,
parasitic or saprophytic; antherids
not producing sperms. — Saprolegnia,
Achlya.

Family 8. Pythiaceae; 9, Cladochytriaceae; 10, An-
cylistaceae.
Order Peroxosporales. Non-aquatic; mostly parasitic
in the tissues of higher plants; usually
forming zoospores in conidia.

Family 11. Albuginaceae. White Rusts. Conidia in
chains. — Albugo.

Family 12. Peronosporaceae, Downy Mildews.
Conidia terminal singly on branched
conidiophores. — Phytophthora, Plas-
mopara, Peronospora.
Order Mucorales. Typically non-aquatic; saprophytic,
or parasitic on other fungi; not form-
ing zoospores; spores single, clustered,
or in sporangia.

Family 13. Mucoraceae, Black Molds. Sporangium
with a columella. — Rhizopus, Mucor,
Pilobolus.

Family 14. IMortierellaceae. Sporangium without a
columella. — Mortierella.

Family 15. Chaetocladiaceae. Spores single, or clus-
tered on branched conidiophores. —
Chaetocladium.

Family 16. Piptocephalidaceae. Spores in chains,
clustered on the ends of branches. —
Piptocephalis, Synccphalis.

336 THE PLANT PH\TA

Order Entomophthorales. Xon-aquatic; mostly para-
sitic in insects; without zoospores.

Family 17. Entomophthoraccae. Fly Fungi. — Ento-
mophthora.
Class 9. BRYOPSIDOIDEAE. Higher Tube Algae. Globu-
lar to stipitate or dendroid, septate or
continuous. (Sp. about 4G0.)
Order Valoniales. Globular coenocytes to compound
septate plants. Isogamic.

Family 18. Botrydiaceae. Little Bladder Algae.
Minute, globular, terrestrial green
plants. — Botrydium, Protosiphon.

Family 19. Chytridiaceae. Minute, globular, endo-
phytic, colorless plants. — Chytri-
dium.

Family 20. Valoniaceae. Large Bladder Algae. Large,
usually septate, marine plants. —
Valonia, Struvea, Halicystis.
Order Dasycladales. Regularly branched, non-septate,
marine plants. IMostly isogamic.

Family 21. Derbesiaceae.

Family 22. Bryopsidaceae. Sea Ferns. Dendroid,
erect, pinnately branched. — Bryopsis.

Family 23. Caulerpaceae.

Family 24. Dasycladaceae. Erect with whorled
branches. — Dasycladus, Acetabularia.
Order Charales. The Stoneworts. Erect, rooted, sep-
tate, dendroid, with whorled branches,
heterogamic, antherids compound.
(Sp. about 160.)

Family 25. Nitellaceae. Oogone crown of ten cells. —
Nitella, Tolypella.

Family 26. Characeae. Oogone crown of five cells. —
Chara, Lamprothamnus.

Phylum V. PHAEOPHYCEAE. The Brown Algae

Brown-green filamentous to large, massive plants, marine

Class 10. PHAEOSPOREAE. Kelps. Reproductive organs
external, isogamic to heterogamic.
(Sp. about 550.)

PHAEOPHYCEAE SAT

Order Ectocarpales. Zoospores and isogametes similar
and motile.

Family 1. Ectocarpaceae. Mostly filamentous, sim-
ple or branched, with zoosj)ores and
gametes. — Ectocarpus, Streblonema.

Family 2. Myriotrichiaceae;3, Choristocarpaceae; 4,
Elachistaceae; 5, Chordariaceae; 6,
Stilophoraceae; 7, Spermatochnaceae;
8, Sporochnaceae; 9, Encoeliaceae; 10,
Desmarestiaceae; 11, Arthrocladia-
ceae; 12, Sphacelariaceae; 13, Ralf-
siaceae; 14, Striariaceae; 15, Dictyo-
siphonaceae.

Family 16. Laminariaceae. Large, parenchymatoas,
usually stalked, with zoospores only.
— Laminaria, Alaria, Postelsia, Nereo-
cj'stis, Macrocj'stis. Egregia.
Order Cutleriales. Zoospores and heterogametes dis-
similar and motile.

Famil}^ 17. Cutleriaceae; 18, Splachnidiaceae.
Order Tilopteridales. Zoospores and heterogametes dis-
similar, eggs non-motile.

Family 19. Tilopteridaceae.
Class 11. DICTYOTINEAE. Reproductive organs external,
heterogamic. (Sp. about 130.)
Order Dictyotales. Plants erect, flat, leaf-like.

Family 20. Dictyotaceae. — Dictyota, Padina, Zonaria.
Class 12. CYCLOSPOREAE. Rockweeds. Reproductive or-
gans in sunken conceptacles, hetero-
gamic. (Sp. about 350.)
Order Fucales. Usually flattish, branched.

Family 21. Durvillaeaceae. Conceptacles on vegetative
])arts of plant. — Durvillaea.

Family 22. Himanthaliaceae. Conceptacles on long
branches arising from a vegetative
cup. — Himanthalia.

Family 23. Fucaceae. Conceptacles on ends of vegeta-
tive branches. — Fucus. Ascophyllum.

Family 24. Sargassaceao. Conceptacles on small
lateral branches. — Sargassum, Ilali-
drys.

338 THE PLANT PHYLA

Phylum Vl. RHODOPHYCEAE. The Red Algae

Red to purple filamentous to massive plants; marine

Class 13. BAXOIOIDEAE. Antherids and oogones developed
from ordinary cells of plant body;
propagation by monospores. Red or
purple ])lants. (Sp. about 50, doubt-
fully belonging here.)
Order Bangiales. One chloroplast in each cell.

Family 1. Bangiaceae. Including the genus Por-
phyra.
Order Rhodochaetales. Several to many chloroplasts
in each cell.
Family 2. Rhodochaetaceae; 3, Campsopogonaceae.
Class 14. FLORIDEAE. Red Seaweeds. Antherids and
oogones specially developed; propaga-
tion by tetraspores. Red or purple
plants. (Sp. about 3,000.)
Order Nemalionales. Lower Red Seaweeds. Mostly
filamentous plants. Sporophores pro-
duced directly from fertilized eggs.
Family 4. Lemaneaceae.

Family 5. Helminthocladiaceae. Filamentous or
parenchymatous, variously branched.
— Batrachospermum, Nemahon.
Family 6. Thoreaceae; 7, Chaetangiaceae; 8, Geli-
diaceae.
Order Cryptonemiales. Hard Red Seaweeds. Filiform,
branched, often complanate; sporo-
phores produced by remote auxiliary
cells.
Family 9. Gloiosiphoniaceae; 10, Grateloupiaceae;
11, Dumontiaceae; 12, Nemasto-
maceae; 13, RhiziphyUidaceae; 14,
Squamariaceae.
Family 15. Corallinaceae. Filamentous, branched
(and jointed) to crustaceous. — Coral-
lina.
Order Ceramiales. "Sea Mosses." Fihform to folia-
ceous plants. Sporophores produced
by nearby auxiliary cells.

RHODOPHYCEAE 339

ramily 1(3. Dclessaricceac. Foliaceous. — Delesseria,
Grinnellia, Nitophylluni.

Family 17. Bonnemaisoniaceae.

Family 18. Rhodomelaceac. Cylindrical, flattened,
to foliaceous. — Poly.siplionia, Rhodo-
mela, Dasya.

Family 19. Ceramiaceae. Filiform, branched, com-
planate. — Ceramium, Lcjolisia, Pti-
lota.
Order Gigartinales. Soft Red Seaweeds. Parenchyma-
tous plants; sporophores produced by
the nearby auxiliary cells branching
in the tissues.

Family 20. Acrotylaceae.

Family 21. Gigartinaceae. Erect or spreading, branch-
ing, cylindrical to flat plants. Chon-
drus, Gigartina, Callophyllis.

Family 22. Rhodophyllidaceae. Erect, or spreading
branching, flat plants. — Rhodophyllis
Rhabdonema.
Order Rhodyaieniales. Higher Red Seaweeds. Filiform,
to foliaceous and massive plants;
sporophores produced b}' nearby aux-
iliary cells growing outward in plant
body.

Family 23. Sphaerococcaceae.

Family 24. Rhodymeniaceae. Filiform to foliaceous.
Rhodymenia, Plocamium.

Phylum VII. CARPOMYCETEAE. The Higher Fungi
Terrestrial, chlorophyll-less, filamentous, parasites and sapro-
phytes, producing spore-fruits
Class 15. ASCOSPOREAE. Ascus Fungi. Spore-fruits con-
taining one or more asci with asco-
spores. (Sp. about 29,000.)
Order Laboulbeniales. Beetle Fungi. Erect, minute,
few celled, bearing simple ascigerous
fruits.
Family 1. Laboulbeniaceae. Parasitic on beetles. —
Laboulbcnia, Ceratomyces, Dicho-
myces.

340

THE PLANT PHTiXA

Order Discolichenes. Disk Lichens. Lichen-forming
fungi with asci in apothecia.

Famil}^ 2. Lecanactidaceae; 3, Pilocarpaceae; 4,
Chrysothricaceae; 5, Thelotrema-
taceae; 6, Diploschistaceae; 7, Ecto-
lechiaceae; 8, G^-alectaceae; 9, Coe-
nogoniaccae; 10, Lecidiaceae; 11,
Phyllopsoraceae.

Family 12. Cladoniaceae. Crustaceous to scaly or
foliose, with Protococcus hosts
(rarely Myxophyceae hosts). — Beo-
myces, Cladonia, Stereocaulon.

Family 13. Gyrophoraceae. Foliose, coriaceous, with
Protococcus hosts. — Umbilicaria.

Family 14. Acarosporaceae. Crustaceous, scaly or
foliose, with Protococcus hosts — The-
locarpon, Acarospora.

Family 15. Ephebaceae; 16, Pyrenopsidaceae; 17,
Lichinaceae.

18. Collemataceae. Gelatinous to crusta-
ceous, scaly foliose to fruticose, with
Nostoc hosts. — Physma, Collema,
Leptogium.

19. Heppiaceae; 20, Pannariaceae.
21. Stictaceae. Fohose, with Palmella or

Nostoc hosts. — Sticta, Lobaria.

Family 22. Peltigeraceae. Foliose with Palmella or
Nostoc hosts. — Peltigera.

Family 23. Pertusariaceae. Crustaceous, with Pro-
tococcus hosts. — Pertusaria.

Family 24. Lecanoraceae. Crustaceous, with Pro-
tococcus hosts. — Lecanora.

Family 25. Parmeliaceae. Foliose, with Protococ-
cus hosts. — Parmelia.

Family 2G. Usneaceae. Fruticose, with Protococcus
hosts. — Usnea, Ramalina.

Family 27. Caloplaceae. Crustaceous, with Proto-
coccus hosts. — Caloplaca.

Family 28. — Theloschistaceae. Foliose to fruticose,
with Protococcus hosts. — Thelo-
schistes.

Family

Family
Family

CARPOMYCETEAE 341

Family 29. Buelliaccae. Crustaceous, with Protococ-

cus hosts. — Buellia.
Family 30. Physciaceae. Foliose to fruticose, with
Protococcus hosts. — Physcia.
Order Caliciales. Powdery Lichens. Common fungi,
and lichen-forming fungi; apothecia
spheroidal, pulverulent.
Family 31. ProtocaHciaceae. True fungi, sapro-
phytic. — Mycocalicium.
Family 32. Caliciaceae. Crustaceous Hchens, with
Protococcus or Stichococcus hosts.
• — Calicium.
Family 33. Cypheliaceae. Crustaceous lichens with
Protococcus or Trentepohlia hosts.
— Cyphelium, Tylophoron.
Family 34. Sphaerophoraceae. Foliose or fruticose
lichens with Protococcus hosts. —
Sphaerophorus.
Order Phacidiales. Little Cup-fungi. Common fungi,
spore-fruits open (apothecia).
Family 35. Stictidaceae. Fleshy, yellow. — Stictis,

Propolis.
Family 36. Tryblidiaceae. Leathery or carbonace-
ous, black. — Tryblidium, Scleroder-
ris.
Family 37. Phacidiaceae. Leathery or carbonace-
ous, black. — Phacidium, Rhytisma.
Order Exoascales. Pocket Fungi. Common fungi;
apothecia much reduced and sim-
plified.
Family 38. Exoascaceae. Parasitic in higher plants.

— Exoascus, Taphrina.
Family 39. Ascocorticiaceae. Saprophytic, asci

forming a cushion. — Ascocorticium.
Family 40. Endomycetaceac. Asci single, not in
masses or in cushions. — Endomyces,
Ercmascus.
Order Pkzizales. Cup-fungi. Conmion fungi; apothe-
cia at length cup-shaped, fleshy or
leathery.

342

THE PLANT PHYLA

Family 41. Pyronemataceae. Fleshy, open from the

first. — Pyronema.
Family 42. Pezizaceae. Fleshy, first spherical, later

open. — Lachnca, Peziza.
Family 43. Ascobolaceae. Fleshy, first spherical,

later open. — Ascobolus.
Family 44. Helotiaceae. Fleshy, mostly open from

the first. — Sclerotinia, Dasyscypha,

Helotium.
Family 45. AloUisiaceae; 46, Celidiaceae; 47, Patel-

lariaceae; 48, Cenangiaceae; 49, Cor-

dieritidaceae; 50, Cyttariaceae.
Order Helvellales. Helvellas. Common fungi; apo-

thecia open from the first; fleshy or

gelatinous.
Family 51. Rhizinaceae. Sessile. — Rhizina.
Family 52. Geoglossaceae. Stalked, capitate. — ]\Ii-

trula, Geoglossum.
Family 53. Helvellaceae. Stalked, capitate. — Mor-

chella, Verpa, Helvella.
Order Graphidales. SHt Lichens. Lichen-forming

fungi, aUied to the preceding families.
Family 54. Arthoniaceae. Crustaceous, with Pal-

mella, Trentepohlia, or Phyllactidium

hosts. — Arthonia, Arthothelium.
Family 55. Graphidaceae. Crustaceous, with Pal-

mella or Trentepohlia hosts. — Ope-

grapha, Graphis, Graphina.
Family 56. Chiodectonaceae; 57, Dirinaceae.
Family 58. Roccellaceae. Fruticose, erect, with Tren-
tepohlia hosts. — Roccella.
Order Pyrenolichenes. Closed Lichens. Lichen-form-
ing fungi, aUied to the preceding

families.
Family 59. Moriolaceae. Crustaceous, with Cysto-

coccus hosts. — Moriola.
Family ()0. Epigloeaceae. Gelatinous, with Pal-

mcUa hosts. — Epigloea.
Family 6L Verrucariaceae. Crustaceous with Prot-

ococcus or Palmella hosts. — Verru-

caria, Thelidium.

CARPOMYCETEAE

343

Family
Family

Family 62. Dermatocarpaceae; 63, Pyrenothamni-
aceae; 64, Pyrenulaceae; 65, Phyl-
lopyreniaceae; 66, Trypethcliaceae;
67, Paratheliaceae; 68, Astrothe-
liaceae; 69, Strigulaceae; 70, Pyreni-
diaceae; 71, Mycoporaceac.
Order Pyrenomycetales. Closed Fungi. Filamentous,
with mostly compound closed spore-
fruits.
Family 72. Hypocreaceae. Mostly reddish or yel-
lowish.— Nectria, Cordyceps, Clavi-
ceps.
Family 73. Dothidiaceae. Black.— Plowrightia,
Dothidea, Phyllachora.
74. Sordariaceae; 75, Chaetomiaceae.
76. Sphaeriaceae. Simple, superficial or
sunken.— Trichosphaeria, Lasio-
sphaeria.
Family 77. Ceratostomataceae; 78, Cucurbitaria-
ceae; 79, Amphisphaeriaceae; 80,
Lophiostomataceae; 81, IMycosphae-
rellaceae; 82, Pleosporaceae; 83, Mas-
sariaceae; 84, Gnomoniaceae.
Family 85. Valsaceae. Permanently enclosed in a
black stroma.— Valsa, Anthostoma,
Diaporthe.
Family 86. Melanconidiaceae; 87, Diatrypaceae; 88,

Melogrammataceae.
Family 89. Xylariaceae. Peripheral in massive
stroma.— Hypoxylon, Xylaria.
Order Hysteriales. Slit Fungi. Common fungi; sapro-
phytic, apothecia opening by a slit.
Family 90. Hypodermataceae; 91, Dichaenaceae; 92,

Ostropaceae.
Family 93. Hysteriaceae. Carbonaceous or leathery,
elongated.— Hysterographium, Hys-

terium.
Family 94. Acrospcrmaceae.
Order Perisporiales. IVlildews. Filamentous, with sim-
ple, mostly spherical spore-fruits.

344 THE PLANT PHYLA

Family 95. Erysiphaceae. Superficial parasites upon
higher plants. — Erysiphe, Micro-
sphaera, Uncinula, Podosphaera.

Family 96. Perisporiaceae; 97, IVIicrothyriaceae.
Order Aspergillales. Little Tubers. Common fungi;
spore-fruits minute or small, mostly
not subterranean.

Family 98. Gymnoascaceae. Loose hyphae, central-
ly ascigerous. — Gj'mnoascus.

Family 99. Aspergillaceae. Spheroidal, parenchy-
matous, sessile. — Aspergillus, Penicil-
lium.

Family 100. Onj^genaceae; 101, Trichocomataceae;
102, Elaphomycetaceae.

Family 103. Terfeziaceae. Spore-fruits subterranean
resembling small Tubers. — Terfezia.
Order Hemiascales. Common fungi; no apothecia; asci
single, scattered.

Family 104. Ascoideaceae; 105, Protomycetaceae.

Family 106. Saccharomycetaceae. Yeast fungi, asci
early isolated. — Saccharomyces.
Order TuBERALES. Tubers. Common fungi; spore-fruits
large, tuberous, subterranean, fleshy,
internally ascigerous.

Family 107. Tuberaceae. Eventually opening. —
Tuber.

Family 108. Balsamiaceae. Not opening. — Balsamia.
Class 16. BASIDIOSPOREAE. Basidium Fungi. Spore-fruits
containing one or more basidia with
basidiospores. (Sp. about 14,000.)
Order Hymenogastrales. False Tubers. Spore-fruits
large, tuberous, subterranean, fleshy,
with internal hymenium. Sapro-
phytes.

Family 109. Hymenogastraceae. Resembling Tuber-
aceae. — Hysterangium, Hj^menogas-
ter, Octaviana, Rhizopogon.
Order Sclerodermatales. Hard puff-balls. Spore-
fruits small to large, roundish, event-
ually pulverulent. Saprophytes.

CARPOMYCETEAE 345

Family 110. Scleroderinataceao. Spore-fruits round,
often stalked. — Scleroderma.

Family 111. Podaxaceae. Spore-fruit pyriform or

clavate, stalked. — Secotium, Podaxon.

Order Lycopehdales. Pulf-balls. Spore-fruits large,

fleshy, at first subterranean, later

emerging — Saprophytes.

Family 112. Lycoperdaceae. Sessile or short^stalked.
— Lycoperdon, Bovista, Geaster.

Family 1 1.3. Tylostomataeeae. Long-stalked. — Tylo-
stoma, Battarea.
Order Xidulariales. Bird-nest Fungi. Spore-fruits
small, spherical or top-shaped, leath-
ery, containing one or more peridioles.
Saprophytes.

Family 114. Nidulariaceae. With several peridioles.
— Nidularia, Crucibulum, Cyathus.

Family 115. Sphaerobolaceae. With but one peridiole.
— Sphaerobolus.
Order Phallales. Stink-Horns. Spore-fruits large,
fleshy, at first tuberous and subter-
ranean, later stalked and emerging.
Saprophytes.

Family 116. Phallaceae. Stalk cylindrical, capped
with spore-mass. — Mutinus, Ithyphal-
lus, Dictyophora.

Family 117. Clathraceae. Stalk ovoid and reticu-
lated, or branched. — Simblum, Clatli-
rus, Aseroe.
Order Ar.ARicALES. Toadstool Fungi. Spore-fruits large,
umbrella-shaped, bracket-shaped or
variously branched; hymenium even-
tually external. — Saprophytes and
parasites.

Family U.S. Agaricaceae. Agarics or Toadstools;
typically umbrella- shaped, usually
fleshy; hymenium on gills. — Cop-
rinus, Russula, Psalliota, Agaricus,
Amanita.

Family 11!). Polyporaceae. Polypores: from umbrel-
la-shaped to bracket-shaped, fleshy to

346 THE PLANT PHYLA

leathery or woody; hymenium lining
pits or pores. — Boletus, Polyporus,
Fomes, Polystictus.

Family 120. Hj'dnaceae. Prickly Fungi. From um-
brella-shaped to bracket- shaped,
fleshy to leathery or woody; hymen-
ium on warts or prickles. — Hydnum,
Irpex.

Famil}^ 12L Clavariaceae. Coral Fungi. Cylindrical
to clavate and fruticose, mostly
leathery; hymenium superficial. — Pis-
tillaria, Clavaria.

Family 122. Thelephoraceae. Leathery Fungi. Flat,
shell-shaped, capitate or branched,
mostly leathery; hymenium superfi-
cial. — Thelephora, C o r t i c i u m,
Stereum.
Order Exobasidiales. Reduced and degraded plants
related to the preceding families;
basidia undivided.

Family 123. Dacryomycetaceae; 124, Tulasnellaceae;
125, Hypochnaceae; 126, Exobasid-
iaceae.
Order Tremellales. Jelly Fungi. Reduced and degrad-
ed plants related to the preceding
families; basidia divided verticall5\

Family 127. Sirobasidiaceae.

Family 128. Tremellaceae. Basidia collateral, spore
fruits open. — Tremella, Exidia.

Family 129. Hyaloriaceae.
Order Auriculariales. Ear Fungi. Reduced and
degraded plants related to the preced-
ing families; basidia divided trans-
versely.

Family 130. Auriculariaceae. Hymenium exposed, on
a gelatinous, foliose or vague spore
fruit. — Auricularia.

Family 131. Pilacraceae.
Class 17. TELIOSPOREAE. Brand Fungi. Parasitic, much
reduced plants, producing erumpent
sori (but no definite spore fruits)

CARPOMYCETEAE 347

consisting of teliospores. (Sp. about
4,200.)
Order Uredinales. Rusts. Typically with sporidia,
pycniospores, aeciospores, uredinio-
spores and teliospores.

Family 132. Aecidiaceae. Teliospores free or fas-
cicled. — "Puccinia," Dicaeoma, Ni-
gredo, Uropj'xis, Aecidium, Phrag-
midium, Uromyces.

Family 133. Uredinaceae. Teliospores compacted
into a crust or column. — "Melamp-
sora," Uredo, Cronartium.

Family 134. Coleosporiaceae. Teliospores compacted
laterally into waxy layers. — Coleo-
sporium.
Order Ustilaginales. Smuts. Typically with sporidia
and teliospores.

Famih" 135. Ustilaginaceae. Germinating teliospore
producing a septated promycelium. —
Ustilago, Sphacelotheca.

Familj' 136. Tilletiaceae. Germinating teliospore pro-
ducing a tubular promycelium. —
Tilletia, Entyloma.
FUNGI IMPERFECTI. The "Imperfect Fungi." Including
16,000 to 17,000 species with regard
to which our knowledge is quite im-
perfect. Most of them are regarded as
conidial states of Ascosporeae. The
classification here given is merely
provisional.
Order Sphaeropsidales. Spot Fungi. Conidia developed
in pycnidia.

Family 137. Sphaerioidaceae. Pycnidia more or less
spherical, black. — Phyllosticta, Sphae-
ropsis, Septoria.

Family 138. Nectrioidaceae. Pycnidia more or less
spherical, bright colored. — Sphaero-
nemella, Aschersonia.

Family 139. Leptostromataceae. Pycnidia shield-
shaped, black. — Leptostroma, Lepto-
thvrium.

348 THE PLANT PHYLA

Family 1-iO. Excipulaceae. Pycnidia more or less
disk-shaped, round or elongated,
black. — Excipula, Discella.
Order Melanconiales. Black-dot Fungi. Conidia de-
veloped on a stroma.

Family 14 L IMelanconiaccae. Including Gloeospor-
ium, Collctotrichum, Melanconium,
Pcstalozzia, Cylindrosporium, etc.
Order AIoniliales. JMolds. Conidia developed upon
separate conidiophores which do not
form a stroma.

Family 142. Mucedinaceae. Conidiophores separate,
hyaline. — Oospora, Monilia, Oidium,
Sterigmatocystis, Botrytis, Ramu-
laria.

Family 143. Dematiaceae. Conidiophores separate,
dark or black. — Torula, Dematium,
Fusicladium, Cladosporium, Macro-
sporium, Cercospora.

Family 144. Stilbaceae. Conidiophores united into an
erect, compound, spore-bearing body.
— Stysanus, Isaria, Graphium.

Family 145. Tuberculariaceae. Conidiophores united
into a compound, cushion-like, spore-
bearing body. — Tuberculina, Fusar-
ium, Epicoccum.

Phylum Vm. BRYOPHYTA. The Mossworts

Chlorophyll-green, small, massive, sexual plants (gameto-

phytes), producing a small, spore-bearing generation

(sporophyte)

Class 18. HEPATICAE. Liverworts. Gametophytes mostly
bilateral, often thalloid, creeping;
sporophytes usually splitting and
containing elaters. (Sp. about 4,000.)
Order Ricciales. The Riccias. Sporophyte globose,
sessile, without columella or elaters.
Family 1. Ricciaceae. Small thallose plants, float-
ing or terrestrial. — Riccia.

BRYOPHYTA 349

Order Axthocekotales. Hornworts. Sporoj)hyte elon-
gated, with a columella and elaters,
two-valved.

Family 2. Anthocerotaccae. Gametophyte a flat
thallus. — Anthoceros.
Order Marchantiales. Great Liverworts. Sporophyte
rounded, without columella, indehis-
cent.

Family 3. Corsiniaceae.

Family 4. Marchantiaceae. Gametophyte large,
thallose, branching, with elaters. —
Marchantia, Conocephalus.
Order Jungermanniales. Scale Mosses. Sporophyte
stalked, four-valved; with elaters.

Family 5. Metzgeriaceae. Gametophyte usually
thallose, archegones lateral. — IMetz-
geria, Pellia, Fossombronia.

Family G. Jungermanniaceae. Gametophyte a bi-
lateral leafy stem, archegones termi-
nal. — Lophosia, Bazzania, Scapania,
Frullania.
Class 19. MUSCI. Alosses. Gametophytes multilateral, usu-
ally erect; sporophytes mostly dehis-
cent by a circular lid, and without
elaters. (Sp. about 12,600.)
Order Andreaeales. Black Mosses. Sporophyte short-
stalked, opening by four to six longi-
tudinal slits.

Family 7. Andreaeaceae. Small mosses. — Andreaea.
Order Sphagnales. Peat Mosses. Sporophyte short-
stalked, opening by a circular lid.

Family 8. Sphagnaceae. Large bog mosses. — Sphag-
num.
Order Bryales. True Mosses. Sporophytes mostly long-
staLked, generally opening by a circu-
lar lid, usually with a peristome.
Sub-order Acrocarpi. ''Top Mosses." Sporophytes
terminal on the main axis of the
gametophyte.

Family 9. Archidiaceae; 10, Dicranaceae ("Turf
Mosses") ; 11, Leucobryaceae (" Cush-

350

THE PLANT PHYLA

ion Mosses"); 12, Fissidentaceae; 13,
Calymperaceae.

Family 14. Pottiaceae. Small to medium plants,
with erect capsules usually having a
peristome of 10 teeth.— Weisia, Bar-
bula, Phascum, Pottia, Encalypta.

Family 15. Grimmiaceae,

Family IG. Orthotrichaceae. Erect, tufted plants,
with erect capsules usually with one
or two rows of 8 or 16 teeth. — Ortlio-
trichum, Macomitrium.

Family 17. Splachnaceae. ''Petticoat Mosses."
Capsule stalked, generally with an
enlarged base. — Splachnum.

Family 18. Oedipodiaceae; 19, Disceliaceae.

Family 20. Funariaceae. ''Bristle Mosses." Capsule
from erect and regular to drooping
and curved or oblique; teeth 0, or one
or two rows of 16 each. — Ephemerum,
Physcomitrium, Funaria.

Family 21. Schistostegiaceae; 22, Drepanophyllaceae;
23, Mitteniaccae.

Family 24. Bryaceae. "Wood Mosses." Small to
large plants with costate leaves, and
pear-shaped, long-stalked capsule;
teeth usually in two whorls of 16
each. — Bryum.

Family 25. Leptostomataceae.

Family 26. Mniaceae. "Wood Mosses." Rather
large, leafy plants, with ovoid to
cylindrical, pendent capsule; peri-
stome usually double, each whorl of
16 teeth. — Mnium.

Family 27. Rhizogoniaceae; 28, Meeseaoeae; 29, Aulo-
comniaceae; 30, Catascopiaceae; 31,
Bartramiaceae.

Family 32. Timmiaceae. "Bristle Mosses." Rather
large leafy plants, with long-stalked
capsules; peristome in two rows of
16 and 64 teeth. — Timmia.

BRYOPHYTA 351

Family 33. Webcraceae; 34, Buxl^aumiaccao (" Hump-
back Mosses"); 35, Georgiaccae.

Famih' 30. Polytrichaccae. "Hair-caps." I-argo,
leafy plants, with long-stalked cap-
sules; teeth short in one row of 32 or
64. — Polytrichum, Pogonatum.
Sub-order Pleurocarpi. "Side Mosses." Sporophytes
terminal on short lateral axes of the
gametophyte.

Family 38. Erpodiaceae; 39, Hedwigiaceae; 40, Font-
inalaceae ("Brook Mosses").

Family 41. Climaciaceae. "Tree Mosses." Large
erect dendroid plants, with erect or
recurved capsules; teeth in two rows
of 16 each. — Climacium.

Family 42. Cryphaeaceae; 43, Leucodontaceae; 44,
Prion odontaceae; 45, Ptychomniaceae;
46, Spiridentaceae; 47, Lepyrodonta-
ceae; 48, Pleurophascaceae.

Family 49. Neckeraceae. More or less rigid, leafy
plants, with short-stalked, erect cap-
sules, having single or double peri-
stome. — Leptodon, Neckera.

Family 50. Lembophyllaceae; 51, Entodontaceae; 52,
Fabroniaceae; 53, Pilotrichaceae; 54
Nematocaceae; 55, Hookeriaceae; 56,
Hypopterygiaceae; 57, Helicophyl-,
laceae; 58, Rhacopilaccae.

Family 59. Leskeaceae. Cushion-forming, leafy
plants, with symmetrical, erect caj)-
sules, having double peristome. —
Leskea, Anomodon, Thuidium.

Family 60. Leucomiaceae; 61, Sematophyllaceae; 62,
Rhegmatodontaceae; 63, Brachythe-
ciaceae; 64, Hypnodendraceae.

Family 65. Hypnaceae. "Bog flosses." Of variable
size and habit, with long-stalked
capsules, which have a double peri-
stome, of 16 teeth in each row. —
Hypnum, Amblystcgium.

352 THE PLANT PHYLA

Phylum IX. PTERmOPHYTA. The Ferns

Chlorophyll-green, small, sexual j^lants (gametophytes), pro-
ducing a large-leaved, rooted generation (sporophyte).
(Here restricted to the ferns alone and
including about 3,800 sp.)

Class 20. EUSPORANGIATAE. Old-fashioned Ferns. Spor-
angia developed from internal cells.
Order Ophioglossales. Adder-tongues. Gametophyte
tuberous, subterranean; sporophyte
with large leaves, some parts sporog-
enous.

Famil}' 1. Ophioglossaceae. Including Ophioglos-
sum, Botrychium, etc.
Order Marattiales. Marattias. Gametophyte flat,
green, superficial; sporophyte with
large compound leaves; sporangia
hypophyllous.

Family 2. Marattiaceae. Large tropical ferns, from
the Paleozoic to the present. — Angi-
opteris, Marattia.
Order Isoetales. Quillworts. Gametophytes dioecious
rounded; sporophyte with erect,
crowded, narrow leaves; sporangia
epiphyllous, basal.

Family 3. Isoetaceae. Aquatic, rush-like plants. —
Isoetes.
Class 21. LEPTOSPORANGIATAE. Modern Ferns. Spor-
angia developed from superficial cells.
Order Filicales. Land Ferns. Spores of one kind; game-
tophytes foliose, monoecious.

Family 4. Osmundaceae. Sporangia globose, split-
ting vertically. — Osmunda.

Family 5. Schizaeaceae;6, Gleicheniaceae; 7, Maton-
iaceae; 8, Parkeriaceae.

Family 9. Cyatheaceae. Tree Ferns. Sporangia
compressed, splitting transversely. — ■
Alsophila, Cyathea, Dicksonia.

Family 10. Hymenophyllaceae. Filmy Ferns. Spor-
angia compressed, splitting vertically.
— Hymenophyllum, Trichomanes.

CALAxMOPHYTA 353

Family 11. Poly pod iaceao. Common Ferns. Spor-
angia compressed, splitting trans-
versely. — Polypodium, Asplenium,
Nephrodium, Adiantum, Pteridium.
Order Marsiliales. Water Ferns. Spores of two kinds;
gametophytes dioecious, rounded.

Family 12. Marsiliaceae. Perennial plants rooted in
the mud, mostly bearing 4-parted
leaves. — Marsilia, Pilularia.

Family 13. Salviniaceae. Annual, small, floating,
nearly rootless plants. — Azolla, Sal-
vinia.

Phylum X. CALAMOPHYTA. The Calamites

Minute sexual plants (gametophytes), producing cylindrical,
jointed and rooted sporophytes which bear
whorled leaves. (Living species about
24, but very many extinct.)

Class 22. SPHENOPHYLLINEAE. Wedge-leaved Calamites.
Paleozoic herbaceous plants of mod-
erate dimensions and solid, jointed
stems; long extinct. Isosporous.
Order Sphexophyllales, including Family 1, Spheno-
phyllaceae.
Class 23. EQUISETINEAE. Horsetails. Paleozoic to recent
herbaceous plants with hollow,
jointed stems. Isosporous.
Order Equisetales. Spore-bearing cones terminal.

Family 2. Equisetaceae. With one living genus. —
Equisetum.
Class 24. CALAMARIXEAE. Old Calamites. Paleozoic
plants, often trees, with hollow, in-
creasing stems, long extinct. Hetcro-
sporous.
Order Calamariales, including Family 3, Protocalamaria-
ceae; 4, Calamariaceae.

354 THE PLANT PHYLA

Phylum XL LEPIDOPHYTA. The Lycopods

Minute gametophytes, producing branching, small-leaved,

rooted sporophytcs. (Living species about

700, but very many extinct.)

Class 25. LYCOPODINEAE. Lower Lycopods. Lsosporous;
leaves without ligules.
Order Lycopodiales. Gametophytes much larger than
the spore.
Family 1. Lycopodiaceae. Ground Pines. Dendroid,

evergreen plants. — Lycopodium.
Familv 2. Psilotaceae.
Class 26. LEPIDODENDRINEAE. Higher Lycopods.
Heterosporous; leaves with ligules.
Order Selaginellales. Small plants; stems not thicken-
ing.
Family 3. Selaginellaceae. Club Mosses. Moss-like
plants bearing terminal cones. —
Selaginella.
Order Lepidodendrales. Paleozoic and Mesozoic trees,
long extinct.
Family 4. Lepidodendraceae; 5, Bothrodendraceae;
6, Sigillariaceae; 7, Pleuromoiaceae.

Phylum XIL CYCADOPHYTA. The Cycads

IMinute gametophytes developed in naked seeds produced by

the large, leafy-stemmed and rooted sporophj^tes;

sperms motile. (Living species about 140, but

very many extinct.)

Class 27. PTERIDOSPERMEAE. Seed Ferns. Paleozoic,
fern-like plants, long extinct.
Order Pteridospermales. With characters of the class.
Family 1. Lyginopterideae; 2, ]\ledullosae; 3, Clad-
oxyleae; 4, Protopityeae; 5, Araucari-
oxyleae.
Class 28. CYCADIXEAE. Common Cycads. Mesozoic to
present plants with pinnate leaves.
Order Cycadales. With the characters of the class.

Family 6. Cycadaceae. Mostly tropical trees with
staminate cones onlv. — Cvcas.

CYCADOPHYTA 355

Family 7. Zamiaceae. Tropical trees with staminate
and seed cones. — Zamia, Macro-
zamia, Dioon.
Class 29. BENNETTITINEAE. Flowering-plant Ancestors.
Mesozoic plants with pinnate leaves,
long extinct.
Order Bennettitales. With the characters of the cla.ss.
Family 8. Bennettitaceae.
Class 30. CORDAITINEAE. Conifer Ancestors. Paleozoic
to present, trees and shrubs with
typically parallel-veined leaves,
mostly long extinct.
Order Cordaitales. Branching trees with elongated
parallel-veined leaves. (Extinct.)
Family 9. Cordaitaceae.
Order Ginkgoales. Maidenhair Trees. Branching trees
with fan-shaped, parallel-veined
leaves. (All extinct but one species.)
Family 10. Ginkgoaceae. But one genus remaining.
— Ginkgo.
Order Gxetales. Joint Firs. Anomalous woody plants
of doubtful relationship, probably to
be placed here, but the sperms not
motile.
Family 11. Ephedraceae. Small Equisetum-like
shrubs with reduced, opposite leaves.
— Ephedra.
Family 12. Gnetaceae. Shrubs and trees with large,
opposite, pinnately veined leaves. —
Gnetum.
Family 13. Tumboaceae. Short, thick-stemmed
woody plants with two large, oppo-
site, parallcl-veined leaves. — Turn-
boa (Welwitschia).

Phylum XIII. STROBILOPHYTA. The Conifers

Minute gametophytes developed in naked seeds produced by

the large, leafy-stemmed and rooted sporojjhyte^; sperms

not motile. (Sp. about 400.)

Class 31. PINOIDEAE. Mostly trees with increasing stents

35a THE PLANT PHYLA

and small mostl}' persistent leaves;
sporophylls mostly in cones.
Order Coniferales. jMicrosporophylls and megasporo-
phylls in cones.

Family 1. Taxodiaceae. Taxodiums. IMicrosporo-
phyll with 2 to 8 sporangia; mega-
sporophyll woody, with 2 to several
erect or inverted seeds; *' seed-scale"
wanting. — Taxodium, Sequoia.

Family 2. Araucariaceae. Old Pines. JMicrosporo-
phyll with 5 to 15 sporangia; mega-
sporophyll woody, with 1 inverted
seed; "seed-scale" rudimentary. —
Araucaria.

Family 3. Abietaceae. Modern Pines. Microsporo-
phjdl with 2 sporangia; megasporo-
phyll woody, with 2 inverted seeds;
* ' seed-scale " promin ent. — Pinus,
Larix, Picea, Abies.

Family 4. Cupressaceae. Cypresses. Microsporo-
phjdl with 4 to 8 sporangia; mega-
sporophyll woody, with 1 to many
seeds; no ''seed-scale." — Cupressus,
Chamaecyparis,

Family 5. Thuyopsidaceae. Thuyas. Microsporo-
phyll with 3 to 5 sporangia; mega-
sporophyll woody, with 1 to many
seeds. — Thuya, Libocedrus.

Family 6. Juniperaceae. Junipers. Microsporo-
phyll with 4 to 8 sporangia; mega-
sporophyll fleshy, with 1 to 2 seeds. —
Juniperus.
Order T.\xales. Microsporophylls in cones, megasporo-
phylls in very small cones or solitary.

Family 7. Podocarpaceae. Microsporophyll with
2 sporangia; megasporophylls in very
small cones or solitary; seed 1, in-
verted. — Podocarpus.

Family 8. Phyllocladaceae. Microsporophjdl with
2 sporangia; megasporophylls soli_
tary; seed 1, erect. — Phyllocladus.

AXTHOPHYTA 357

Family 9. Taxaceae. Yews. Microsporophyll with
3 to 5 sporangia; megasporophyll
solitary; seeds 1 or 2, erect. — Taxus,
Torreya.

Phylum XIV. ANTHOPHYTA. The Flowering Plants

Minute gametophytes developed in seeds enclosed in carpels
in flowers, produced by the large, leafy-stemmed and
rooted sporophytes; sperms not motile
(Sp.' about 132,500.)

Class 32. MOXOCOTYLEDONEAE. .Monocotyledons-
Leaves of sporophj'te alternate, from
the first, iLsually parallel veined;
fibrovascular bundles of stem scat-
tered. (Sp. about 23,700.)
Sub-Class IMOXOCOTYLEDONEAE-HYPOGYXAE. Peri-
anth and stamens arising below the
carpels (carpels superior).
Order Allsmatales. Carpels separate, superior to all other
parts of the flower.

Family 1. Alismataceae. Water Plantains. Large-
leaved herbs with rather large flowers
having cal^'x and corolla of 3 leaves
each. — Alisma, Sagittaria.

Family 2. Butomaceae;3, Triuridaceae;4, Scheuch-
zeriaceae.

Family 5. Typhaceae. Cat-tails. Tall herbs with
linear, sheathing leaves and cylin-
drical-crowded flowers. — Typha.

Family G. Sparganiaceae; 7, Pandanaceae; 8, Apon-
ogetonaceae.

Family 9. Potamogetonaceae. River-weeds. ]\Iost-
ly aquatic herbs with reduced small
flowers. — Potamogeton, Zostera, Zan-
nichellia.
Order Liliales. Carpels (usually 3) united forming a
compound pistil, superior; perianth
in two whorls (of 3 eacli), corolla-like.

Family 10. Liliaccac. Lilies. Pistil, mostly 3-
celled; stamens (3. — Lilium. Ervthron-

358

THE PLANT PHYLA

Famib

Family 1.

Family
Family

ium, Tulipa, Yucca, Asparagus,
Allium.

11. Stemonaceac; 12, Pontederiaceae; 13,
Cyanastraceae; 14, Philydraceae.
Commclinaceao. Spiderworts. Succu-
lent herbs with 3 or 2-celled pistil,
and 6 stamens. — Commelina, Trades-
cant ia.

16. Xyridaceae; 17, Mayaceae.

18. Juncaceae. Rushes. Herbs with stiff,
narrow leaves, and 1 to 3-celled pistil.
— Juncus.
Eriocaulonaceae; 20, Thurniaceae; 21,
Rapateaceae; 22, Naiadaceae.
Compound pistil mostly tricarpellary,
superior; ovules solitary.

23. Cyclanthaceae.

24. Araceae. Arums. Mostly herbs with
broad, petioled reticulate-veined
leaves; flowers small, clustered. —
Acorus, Symplocarpus, Calla, Cala-
dium. Arum, Arisaema.

25. Lemnaceae. Duckweeds. Reduced
plants related to the Araceae, with
flat plant-body floating free on water.
— Lemna, Spirodela.
Compound pistil mostly tricarpellary,

superior; ovule usually 1; perianth
reduced to rigid scales.
Family 2G. Palmaceae. Palms. Trees or shrubs
with pinnate or palmate leaves. —
Phoenix, Chamaerops, Calamus, Ore-
odoxa, Cocos.
Order Graminales. Compound pistil reduced to 2 or
3 carpels; ovule solitary; perianth re-
duced to small scales, or wanting.
Restionaceae; 28, Centrolepidiaceae; 29,
Flagellariaceae.
30. Cyperaceae. Sedges. Grass-like herbs
with 3-ranked leaves. — Cyperus, Scir-
pus, Carex.

Family 19.
Order Arales.

Family
Familv

Familv

Order Palmales.

Family 27

Familv

AXTIIOPHYTA 359

Family ol. Poaceae. Grasses, with 2-ranked leaves.
(Sp. about 3,o45.)
There aie six tril)es and several sub-tribes, of which the
Bamboos are the lowest, while the
Agrostideae, Paniceae and Maydeae
are at the summits 'of as many di-
verging phyletic lines. These groups
may be distinguished as follows:

A. Woody })Iants; a joint between the leaf-blade and the

sheath. 1. Bamboos. {Bambuseae)
Bambusa.

B. Herbaceous plants; no joint between the leaf-blade

and sheath.

I. Spikelets with the larger flowers at the base.

1. Spikelets typically containing several to many

flowei's.

a. IMostly arranged in panicles; awns ter-

minal. 2. Fescue Grasses (Festuceae)
— Bromus.

b. Arranged in panicles; awns dorsal. 2a.

Oat Grasses (Avetieae) — Avena.

c. Sessile in two rows on the opposite

sides of the main stem. 2b. Wheat
Grasses ( Triticeae) — Triticum.

d. Sessile in two rows on one side of a flat-

tened axis. 2c. Gramma Grasses.
(Chlorideae) — Bouteloua.

2. Spikelets containing but one flower. 3. Red-

top Grasses (Agrostidcae) — Agrostis.

II. Spikelets with the larger flowers at the top.

1. A joint above the empty glumes.

a. Spikelets with five glumes; palets one-
nerved. 4. Canary Grasses {Phal-
aridcae) — Phalaris.

2. A joint below the empty glumes.

a. Spikelets flattened laterally, one-flowered.

4a. Rice Grasses (Oryzeae) — Oryza.

b. Spikelets not flattened laterally, one to

two-flowered.
(1) Stems hollow, medium sized to
small. 5. Panic Grasses {Paniceae)—
Panicum.

360

THE PLANT PHYLA

(2) Stems mostly solid, often large and
tall.

(a) Spikelets perfect or staminate,

not separated. 6. Blue-stem
Grasses (Andropogoneae) —
Andropogon.

(b) Spikelets all unisexual, sepa-
rate, monoecious. 6a. Maize
Grasses (Maydeae) — Zea.

Order Hydrales,
Order Iridales.

Sub-Class MONOCOTYLEDONEAE-EPIGYNAE. Peri-
anth and stamens arising above the
carpels; carpels inferior,
with one family, 32, Hydrocharitaceae.
Compound tricarpellary pistil inferior;
whorls of perianth mostly alike and
regular.

Family 33. Amaryllidaceae. Amaryllises. Leaves
narrow to broad, the veins longi-
tudinal. — Amaryllis, Narcissus, Ag-
ave, Hypoxis.

Family 34. Haemodoraceae.

Family 35. Iridaceae. Irises. Leaves sword-shaped;
stamens 3. — Iris, Crocus, Sisyrinch-
ium. Gladiolus.

Family 36. Velloziaceae; 37, Taccaceae; 38, Dio-
scoreaceae.

Family 39. Bromeliaceae. Leaves mostly rosulate
elongated and pointed. — Tillandsia,
Ananas.

Family 40. Musaceae. Bananas. Large herbs,
often tree-like. — Musa, Strelitzia.

Family 41. Zingiberaceae.

Family 42. Cannaceae. Perennial herbs with pin-
nately-veined leaves and irregular
flowers. — Canna.

Family 43. Marantaceae.
Order Orchidales. Compound tricarpellary pistil in-
ferior; perianth irregular.

Family 44. Burmanniaceae.

Family 45. Orchidaceae. Orchids. Flowers irregular,

ANTHOPIIYTA

361

stamens lor 2. — Cypripedium, Orchis,
Platanthera, Vanilla, Spiranthes.
Class 33. DICOTYLEDONEAE. Dicotyledons. Leaves of
young sporophy te opposite, sometimes
remaininp; so, usually reticulate
veined; fibrovascular bundles of stem
in one or more rings. (Sp. about
108,800.)
Sub-Class DICOTYLEDONEAE-AXIFLORAE. '' Axis Flow-
ers." Axis of the flower normally cy-
lindrical, spherical, hemispherical or
flattened, bearing on its surface
the hypogynous perianth, stamens
and carpels (or the stamens may be
attached to the corolla).
Super-Order .\xiflorae-Apopetalae-Polycarpellatae.
Carpels typically many, separate
or united; petals separate.
Order Ranales. All parts of the flower free (not united);
carpels separate; typically many.

Family 46. Magnoliaceae. Magnolias. Trees and
shrubs with many petals in 1 to many
whorls. — Magnolia, Liriodendron.

Family 47. Calycanthaceae; 48, Monimiaceae; 49,
Cercidiphyllaceae; 50, Trochoden-
draceae; 51, Leitneriaceae.

Family 52. Anonaceae. Papaws. Trees and shrubs
with 6 petals in two whorls.^
Asimina.

Family 53. Lactoridaceae; 54, Gomortegaceae; 55,
Myristicaceae; 56, Saururaceae; 57,
Piperaceae; 58, Lacistemaceae; 59,
Chloranthaceae.

Family ()0. Ranunculaceae. Buttercups. Mostly
herbs, normally with 5 i)etals in 1
whorl. — Myosurus, Ranunculus, An-
emone, Clematis.
Lardizabalaceae; 62, Berberidaceae; 63,

Menisi^ermaceae; 64, Lauraccae.

Nelumbaceae. Lotuses. Aquatic herbs

with separate carpels. — Nelumbo.

Family
Family

65.

362

THE PLANT PHYLA

Family 06. Cabombaceae; 67, Ceratophyllaceae; 68,
Dilleniaceae; 69, Winteranaceae.
Order Ma lv ales. Pistil usually of 3 to many carpels,
with as many cells; stamens normally
indefinite, monadelphous, branched.

Family 70. Sterculiaceae.

Family 7L Malvaceae. Mallows. Herbs, shrubs
and trees; flowers regular with mon-
adelphous stamens. — Malva, Hibis-
cus, Althaea, Abutilon, Gossypium.

Family 72. Bombacaceae; 73, Scytopetalaceae; 74,
Chlaenaceae; 75, Gonystjdaceae.

Family 70. Tiliaceae. Lindens. Mostly trees and
shrubs; flowers regular with free
stamens. — Tilia.

Family 77. Elaeocarpaceae; 78, Balanopsidaceae.

Family 79. Ulmaceae. Elms. Trees and shrubs;
flowers reduced, small, apetalous;
pistil 1 or 2-celled. — Ulmus, Celtis,
Planera.

Family 80. Moraceae. Figs. Trees, shrubs and
herbs, mostly with a milky juice;
flowers reduced, smafl, apetalous; pis-
til 1-celled. — Morus, Toxylon, Ficus,
Humulus, Cannabis.

Family 81. Urticaceae. Nettles. Herbs, shrubs and
trees, juice not milky; flowers re-
duced, small apetalous; pistil 1-
celled. — Urtica, Boehmeria.
Order Sarraceniales. ''Insectivorous" plants.

Family 82. Sarraceniaceae; 83, Nepenthaceae.
Order Geraniales. Pistil of several carpels; receptacle
usually with an annular or glandular
disk.

Family 84. Geraniaceae. Geraniums. Herbs, shrubs
and trees; pistil 3 to 5-celled on an
elongated receptacle. — Geranium,
Pelargonium, Erodium.

Family 85. Oxalidaceae. Sorrels. Mostly herbs
with a sour juice; flowers pentamer-
ous. — Oxalis.

ANTHOPHYTA

363

Family 80.
Fiiiiiily 87.

Family 88.
Family 94.

Family 95.

Family 104.

Family 105.
Order Guttifer

Family 106.
Family 107.

Family 118

Family 119
Family 121

Tropauolaceae. Succulent, trailing herbs
with alternate, peltate leaves, and
irregular flowers. — Tropaeolum.

Balsaminaceae. Touch-me-nots. Succu-
lent, mostly erect herbs with alter-
nate leaves, and irregular flowers. — ■
Impatiens.

Limnanthaceae; 89, Linaceae; 90, Hum-
iriaceae; 91, Erythroxylaceae; 92, Zy-
gophyllaceae; 93, Cneoraceae.

Rutaceae. Herbs, shrubs and trees usu-
ally wuth opposite, glandular-dotted
leaves, and regular flowers. — Xan-
thoxylum, Ruta, Ptelea, Limonia,
Citrus.

Simarubaceae; 96, Burseraceae; 97, Meli-
aceae; 98, Malpighiaceae; 99, Trigoni-
aceae; 100, Vochysiaceae; 101, Poly-
galaceae; 102, Tremandraceae; 103,
Dichapetalaceae.

Euphorbiaceae. Herbs, shrubs and trees,
mostly with a milky juice; flowers
diclinous; pistil usually 3-celled. —
Euphorbia, Croton, Ricinus, jManihot.

Callitrichaceae.
.\LES. Pistil mostly of 2 or more carpels;
stamens usually indefinite; endosperm
usually wanting.

Theaceae. Shrubs and trees with regular
flowers. — Thea, Gordonia, Stuartia.

Cistaceae; 108, Guttiferaceae; 109, Eu-
cryphiaceae; 110, Ochnaceae; 111,
Dipterocarpaceae; 112, Caryocaraceae
113, Quiinaccae; 114, ]\larcgraviaceae;
115, Flacourtiaceae; 116, lii.xaceae;
117, Cochlospermaceae.

Violaceae. Violets. Herbs and shrubs
and trees, with irregular flowers and
tficarpellary pistil. — \''iola.

Malesherbiaceao; 120, Turneraceae.

Passifloraceae. Pa.ssion Flowers. Climb-

364 THE PLANT PHYLA

ing herbs and shrubs with regular
flowers. — Passiflora.

Family 122. Achariaceae; 123, Caricaceae; 124,
Stachyuraceae; 125, Koeberliniaceae.
Order Rhoedales. Pistil of two or more united carpels,
mostly one-celled with parietal pla-
centae.

Family 126. Papaveraceae. Poppies. Perianth 2 to
4-merous, stamens indefinite, pistils
2 to many carpellary. — Eschscholtzia,
Sanguinaria, Argemone, Papaver,
Bicuculla.

Family 127. Tovariaceae.

Family 128. Nymphaeaceae. Water lilies. Aquatic
herbs with floating leaves. — Nym-
phaea, Castalia, Victoria.

Family 129. Moringaceae; 130, Resedaceae; 131, Cap-
paridaceae.

Family 132. Brassicaceae. Mustards. Perianth 4-
merous, stamens 6 or 4, pistil 2-car-
pellary. — Sinapis, Brassica, Rapha-
nus, Bursa, Alyssum.
Order Caryophyllales. Pistil usually of 3 or more united
carpels, mostly 1-celled; stamens as
many or twice as many as the petals.

Family 133. Caryophyllaceae. Pinks. Mostly herbs,
with opposite leaves; ovules many on
a central placenta. — Silene, Lychnis,
Dianthus, Alsine, Paronychia.

Family 134. Elatinaceae.

Family 135. Portulacaceae. Mostly succulent herbs
with 2 sepals and 4 to 5 petals. —
Portulaca, Claytonia.

Family 136. Aizoaceae; 137, Frankeniaceae; 138,
Fouquieraceae; 139, Tamaricaceae.

Family 140. Salicaceae. WiHows. Shrubs and trees
with alternate leaves and no perianth.
— Salix, Populus.

Family 141. Podostemonaceae; 142, Hydrostachyda-
ceae; 143, Phytolaccaceae; 144, Basel-
laceae.

ANTllOPllYTA 365

Family 145. Amaranthaceae. Mostly herbs and

shrubs with opposite or alternate

leaves; perianth harsh. — Amaranthus,

Celosia, Froelichia.
Family 146. Chenopodiaccae. Mostly herbs and

shrubs with alternate or opposite

leaves; perianth soft. — Beta, Cheno-

podium, Atriplex, Salsola.
Family 147. Polygonaceae. Herbs, shrubs and trees,

with alternate, rarely opposite leaves;

perianth petal - like. — Eriogonum,

Rheum, Polygonum, Fagopyrum,

Coccoloba.
Family 148. Nyctaginaceae; 149, Cynocrambaceae;

150, Batidaceae.
Super-Order Axiflorae-Gamopetalae-Polycarpel-

LATAE. Carpels typically many,

united; petals united.
Order Prlmulales. Pistil mostly 1-celled, with a central

placenta; stamens mostl}^ opposite

the corolla lobes.
Family 151. Primulaceae. Primroses. Herbs with

showy flowers. — Primula, Cyclamen,

Dodecatheon.
Family 152. Plantaginaceae. Plantains. Herbs with

reduced flowers; stamens alternate

with the petals. — Plantago.
Family 153. Plumbaginaceae; 154, Theophrastaceae;

155, Myrsinaceae.
Order Ericales. Pistil more than 1-celled, with many

minute seeds; stamens alternate with

the corolla lobes.
Family 156. Clethraceae.
Family 157. Ericaceae. Heaths. Shrubs and small

trees with mostly evergreen leaves;

anthers opening bj^ a terminal pore. —

Rhododendron, Kalmia, Arctostaph}--

los, Vaccinium, Erica.
Family 158. Epacridaceae; 159, Diapensiaccac; 160,

Pirolaceae; 161, Lennoaceao.
Order Ebenales, with four families of mostly

THE PLANT PHYLA

tropical trees. — 162, Sapotaceae; 163,
Ebenaceae; 164, Symplocaceae; 165,
StjTacaceae.
Super-Order Axiflorae-Gamopetalae-Dicarpellatae.
Carpels typicall}^ two, united; petah
united.
Order Polemoniales. Corolla regular; stamens as many
as the corolla lobes; leaves mostly
alternate.

Family 166. Polemoniaceae. Phloxes. Mostly herbs
with alternate or opposite leaves;
pistil tricarpellary. — Phlox Gilia, Pol-
emonium.

Family 167. Convolvulaceae. IMorning Glories. Most-
ly herbs and shrubs with alternate
leaves; pistil mostly bicarpellary.
— Convolvulus, Ipomoea, Evolvulus,
Cuscuta.

Family 168. Hydrophyllaceae. Soft herbs; pistil bi-
carpellary. — Hydrophyllum, P h a -
celia.

Family 169. Borraginaceae. Forget-me-nots. Herbs,
shrubs and trees; pistil bicarpellary,
4-celled. — Heliotropium, B o r r a g o ,
Myosotis, Mertensia, Lithospermum.

Family 170. Nolanaceae.

Family 171. Solanaceae. Nightshades. Mostly herbs
and shrubs; pistil bicarpellarj', mostly
2-celled. — Solanum, Atropa, Physalis,
Capsicum, Datura, Nicotiana, Pe-
tunia.
Order Gentianales. Corolla regular; stamens as many as
the corolla lobes; leaves opposite.

Family 172. Oleaceae. Olives. Mostly shrubs and
trees; stamens 2 or 4; ovary 2-celled.
— Olea, Syringa, Jasminum, Fraxinus.

Family 173. Salvadoraceae; 174, Loganiaceae.

Family 175. Gentianaceae. Mostly herbs with limpid
juice; ovary usually 1-celled. — Gen-
tiana, Eustoma, Menyanthes.

Family 176. Apocynaceae. Trees, shrubs and herbs

ANTHOPIIYTA 3(37

witli milky juice; ovarj' 2-celled, or of
two separated carpels. — Apocynum,
Vinca, Nerium.

Family 177. Asclepiadaceae. Alilkweeds. Herbs and
shrubs with milky juice; ovary of
two separated carpels. — Asclepias,
Ceropegia, Stapelia, Hoya.
Order Scrophulariales. Corolla mostly irregular; sta-
mens fewer than the corolla lobes;
ovules many.

Family 178. Scrophulariaceae. Snapdragons. Mostly
herbs; ovary 2-celled; seeds endo-
spermous. — Verbascum, Antirrhinum,
Scrophularia, ]\Iimulus, Veronica,
Gerardia, Castilleia, Pedicularis.

Family 179. Bignoniaceae. Catalpas. Mostly trees
and shrubs; ovary 1 or 2-celled; seeds
without endosperm. — Bignonia, Cat-
alpa, Tecoma.

Family 180. Pedaliaceae; 181, Martyniaceae; 182,
Orobanchaceae; 183, Gesneraceae;
184, Columelliaceae; 185, Lentibu-
lariaceae; 186, Globulariaceae; 187,
Acanthaceae.
Order Lamiales. Corolla mostly irregular ; stamene fewer
than the corolla lobes; ovules usually
solitary.

Family 188. Myoporaceae; 189, Phrymaceae.

Family 190. Verbenaceae. Herbs, shrubs and trees,
with usually undivided stigma. —
Verbena, Lantana, Lippia, Tectona,
Vitcx.

Family 191. Lamiaceae. Mints. Mostly herbs and
shrubs, aromatic, with usually bifid
stigma. — Lavandula, Nepeta, ^Salvia,
Thvmus, Mentha, Coleus.
Sub-Class DICOTYLEDOXEAE-CALYCTFLORAE. "Cup
Flowers." Axis of the flower nor-
mally expanded into a disk or cup,
bearing on its margin the perianth and

368 THE PLANT PHYLA

stamens (or the latter may be at-
tached to the corolla).
Super-Order Calyciflorae-Apopetalae. Petals separate.
Carpels many to few, separate to
united, superior to inferior.
Order Rosales. Flowers usually perfect, regular or irregu-
lar; carpels from wholly separate to
more or less united, sometimes over-
grown by the axis-cup; styles distinct.
- Family 192. Rosaceae. Roses. Herbs, shrubs and
trees, with mostly alternate leave3
and indefinite stamens; carpels from
many to one, free. — Potentilla, Fra-
garia, Spiraea, Rosa.

Family 193. IVIalaceae. Apples. Shrubs and trees,
with alternate leaves, and usually
many stamens; carpels few, more or
less united to the axis cup. — Malus,
Pirus, Crataegus.

Family 194. Prunaceae. Plums. Shrubs and trees
with alternate leaves, and many
stamens; carpel one, in the bottom
of the deep cup, becoming a drupe on
ripening. — Prunus, Amygdalus.

Family 195. Crossosomataceae; 196, Connaraceae.

Family 197. Mimosaceae. The Mimosas. Trees,
shrubs and herbs, with alternate,
mostly compound leaves; flowers
regular; stamens 10 or more, usually
separate; carpel one, ripening into a
legume. — Acacia, Mimosa.

Family 198. Cassiaceae. The Sennas. Trees, shrubs
and herbs, with alternate, mostly
compound leaves; flowers irregular;
stamens 10 or less, usually separate;
carpel one, ripening into a legume. —
Cassia, Caesalpinia, Gleditsia, Gym-
nocladus.

Family 199. Fabaceae. The Beans. Herbs, and some
shrubs and trees, with alternate,
mostly compound leaves; flowers ir-

ANTHOPHYTA

369

regular; stamens 10 or less, usually
united; carpel one, ripening into a
legume. — Lupinus, Medicago, Trifo-
lium, Robinia, Vicia, Pisum, Phaseo-
lus.

Family 200. Saxifragaceae. Saxifrages. Herbs with
alternate or opposite leaves; flowers
regular; stamens 8 to 10; carpels 2,
superior. — Saxifraga, Heuchera, ]\lit-
ella.

Family 201. Hydrangeaceae. Hydrangeas. Shrubs
and trees with mostly opposite leaves;
flowers regular; stamens 8 to 40;
carpels 2 to 5, united, more or less
overgrown by the axis-cup. — Phila-
delphus, Hydrangea.

Family 202. Grossulariaceae. Gooseberries. Shrubs
with alternate leaves; flowers regu-
lar; stamens 5; carpels 2 to several,
wholly overgrown by the fleshy axis-
cup. — Ribes.

Family 203. Crassulaceae; 204, Droseraceae; 205,
Cephalotaceae; 206, Pittosporaceae;
207, Brunelliaceae; 208, Cunoniaceae;
209, Myrothamnaceae; 210, Bruni-
aceae; 211, Hamamelidaceae; 212,
Casuarinaceae; 213, Eucommiaceae.

Familj' 214. Platanaceae. Trees with alternate
leaves and reduced, monoecious flow-
ers in globular heads; no perianth. —
Platanus.
Order Myrtales. Flowers usually perfect, regular;
pistils several, united, usually in-
ferior.

Family 215. Lythraceae. Herbs, shrubs and trees,
usuall}" with o])posite leaves; pistil
free. — Lythrum, Cuj)hea.

Family 216. Sonneratiaceae; 217, Punioaceae; 218,
Lecythidaceac; 219, Mela.^tomataceae.

Family 220. Myrtaceac. Myrtles. Trees and shrubs
with opposite or alternate leaves;

370 THE PLANT PHYLA

stamens indefinite; pistil 2 to many-
celled, inferior. — Myrtus, Pimenta,
Eugenia, Jambosa, Eucalyptus, Mal-
aleuca.

Family 221. Combretaceae; 222, Rhizophoraceae.

Famil}' 223. Oenotheraceae. Evening Primroses.
Mostly herbs, with opposite or alter-
nate leaves; stamens 1 to 8; pistil usu-
ally 4-celled, inferior. — Epilobium,
Anogra, Oenothera, Gaura, Fuchsia,
Circaea.

Family 224. Halorrhagidaceae; 225, Hippuridaceae;
226, Cynomoriaceae; 227, Aristoloch-
iaceae; 228, Rafflesiaceae; 229, Hyd-
noraceae.
Order Cactales. Flowers regular and perfect; pistil
syncarpous, 1-celled, with parietal
placentae, inferior; mostly leafless
plants.

Family 230. Cactaceae. Cactuses. Fleshy-stemmed,
mostly leafless plants. — Peireskia,
Opuntia, Cereus, Carnegiea, Echino-
cactus. Cactus, Melocactus, Rhipsalis.
Order Loasales. Flowers regular and perfect or diclinous;
pistil syncarpous, 1-celled, with pa-
rietal placentae, inferior; leaves ample.

Family 231. Loasaceae. Star Flowers. Erect herbs
with perfect, regular flowers, and
many stamens. — MentzeHa, Loasa.

Family 232. Cucurbitaceae. Melons. Mostly climb-
ing herbs with but 3 stamens. —
Cucurbita, Cucumis, Lagenaria, Cit-
rullus, Momordica.

Family 233. Begoniaceae. Begonias. Mostly erect
herbs, with diclinous flowers and
many stamens. — Begonia.

Family 234. Datisaaceae; 235, Ancistrocladaceae.

Order Celastrales. Flowers regular, rcceptacular disk

annular or turgid, sometimes adnate

to the 1 to several-celled pistil, the

latter sometimes inferior; ovules few.

ANTHOPIIYTA 371

Family 236. Rhainnaccac. Bucktliorns. Erect trees
and shrubs. — Rhainnus, Ceanothus,
Colletia.

Family 237. Vitaceae. Grapes Woody climbers. —
Vitis, Parthenocissus, Ampelopsis.

Family 238. Celastraceae; 239, Buxaceae; 240, Aquil-
foliaceae; 291, Cyrillaceae; 242, Penta-
phyllaceae; 243, Corynocarpaceae; 244,
Hippocrateaceae; 245, Stackhousi-
aceae; 246, Staphyleaceae; 247, Geis-
solomataceae; 248, Penaeaceae; 249,
Oliniaceae; 250, Thymelaeaceae; 251,
Hernandiaceae; 252, Elacagnaceae;
253, Myzodendraceac; 254, Santala-
ceae; 255, Opiliaceae; 256, Grub-
biaceae; 257, Olacaceae.

Family 258. Loranthaceae. Mistletoes. Parasitic
herbs or shrubs with opposite or
alternate leaves; flowers perfect or
diclinous, apetalous; pistil 1-celled,
inferior. — Loranthus, Viscum, Phor-
adendron, Razoumofskya.

Family 259. Balanophoraceae.
Order Sapindales. Flowers mostly regular, disk tumid
(or wanting) ; pistil 1 to several-celled,
sometimes inferior; ovules 1 to 2.

Family 260. Sapindaceae. Mostly tropical trees and
shrubs, with alternate leaver, and
regular flowers. — Sapindus, Koelreu-
teria.

Family 261. Hippocastanaceae. Buckej'es. Trees
and shrubs with opposite, palmate
leaves, and large, irregular flowers;
pistil superior. — Aesculus.

Family 262. Aceraceae. Maples. Trees and shrubs
with opposite, palmate or pinnate
leaves, and small, regular flowers;
pistil superior. — Acer.

Family 263. Sabiaceae; 264, Icacinaceae; 265, Meli-
anthaceae; 266, Empetraccue; 267,
Coriariaceae.

372 THE PLANT PHYLA

Family 268. Anacardiaceae. Sumachs. Trees and
shrubs with alternate pinnate leav^es;
and small flowers with superior or
inferior, 1 to 5-celled pistil. — Rhus,
JMangifera, Cotinus.

Family 269. Juglandaceae. Walnuts. Trees and
shrubs, with alternate, pinnate leaves;
and small much reduced flowers
with inferior, 1-celled pistil. — Juglans,
Hicoria.

Family 270. Betulaceae. Birches. Trees and shrubs
with alternate, pinnate leaves, and
diclinous flowers in aments; pistil 1
to 2-celled, superior or inferior. —
Betula, Alnus, Corylus, Ostrya, Car-
pinus.

Family 271. Fagaceae. Beeches. Trees and shrubs
with alternate, pinnate leaves and
diclinous flowers in aments; pistils 2
to6-celled, inferior. — Fagus, Castanea,
Quercus.

Family 272. Myricaceae; 273, Julianaceae; 274, Pro-
teaceae.
Order Umbellales. Flowers regular, usuall}^ perfect,
disk adherent to the mostly bicar-
pellary pistil which is inferior and 2-
celled; ovules 1 in each cell.

Family 275. Araliaceae. Ginsengs. Mostly trees
and shrubs; pistil 2 to 15-carpellary;
fruit a berry. — Aralia, Hedera, Panax.

Family 276. Apiaceae. Parsleys. Mostly herbs;
pistil bicarpellary; fruit dry, splitting
vertically; inflorescence umbellate. —
Sanicula, Coriandrum, Apium, Cicuta,
Pastinaca, Foeniculum, Ferula, Hera-
cleum, Daucus.

Family 277. Cornaceae. Cornels. Mostly shrubs and
trees with usually opposite leaves;
pistil 2 to 4-carpellary; fruit a drupe.
— Cornus, Nyssa.

ANTHOPHYTA 373

Super-Order Calyciflorae-Gamopetalae. Petals united.
Carpels few, united, inferior.

Order Rubiales. Flowers regular or irregular; ovary 2
to 8-celled; ovules 2 to many.
Family 278. Rubiaceae. Coffees. Trees, shrubs and
herbs with opposite or whorled leaves
and mostly regular flowers. — Galium,
Houstonia, Cinchona, Coffea, IMitch-
ella.
Family 279. Caprifoliaceae. Honeysuckles. Mostly
woody plants, with opposite leaves
and mostly irregular flowers. — Sam-
bucus. Viburnum, Linnaea, Lonicera.
Family 280. Adoxaceae; 281, Valerianaceae; 282, Dip-
sacaceae.

Order Campaxulales. Flowers regular to irregular,
stamens mostly free from the corolla;
ovary 1 to several-celled; ovules 1
to 8.
Family 283. Campanulaceae. Bellworts. Mostly
herbs; stamens, usually 5, free from
the style. — Campanula, Lobelia.
Famil}' 284. Goodeniaceae; 285, Stylidiaceae; 286,
Calyceraceae.

Order Asterales. Composites. Flowers regular to irregu-
lar, collected into involucrate heads;
calyx small and often forming a
"pappus" or wanting; stamens 5,
epipetalous, mostly with their an-
thers connate; carpels 2, united,
inferior, with one style which is
2-branched above; ovule one, erect,
anatropous. An immense order
(commonly regarded as a family)
of more than 14,300 species, which are
usually distributed among fourteen
tribes, all of which are here raised
to families. In the following arrange-
ment the Helianthaceae are regarded
as the lowest, from which the two
princij)al phyletic lines have arisen.

374 THE PLANT PHYLA

culminating on the one hand in the
Eupatoriaceae, and on the other in the
Lactucaceae.

Key to the Families of Asterales

A. Pappus not capillary; plants typically large

and coarse.
L Receptacle chaffy.

1. Usually with ray flowers — 287. Heli-
anthaceae.

2. Without ray flowers — 288. Ambros-
iaceae.

IL Receptacle naked (rarely chaffy).

1. Anthers tailless.

a. Involucral bracts mostly in 2

series — 289. Heleniaceae.

b. Involucral bracts in many

series — 290. Ardotidaceae.

2. Anthers tailed or mucronate — 291.
Calendulaceae.

B. Pappus bracteose, none, or capillary; recep-

tacle usually naked; plants typically
low to medium sized.
L Usually without ray flowers; anthers
tailed — 292. Inulaceae.

C. Pappus from short bracteose to capillary or

none; receptacle naked; plants typi-
cally medium sized.

L Usually with ray flowers — 293. Aster-
aceae.

IL Without ray flowers; style branches
filiform, hispidulous. — 294. Vernoni-
aceae.

III. Without ray flowers; style branches
clavate, papillose — 295. Eupatoriaceae.

D. Pappus a short crown or none; involucral

bracts dry, scarious, imbricated;
plants typically medium sized.
I. Usually with white ray flowers — 296.
Anthettiidaceae.

ANTHOPHYTA 375

E. Pappus capillary; involucral bracts mostly

valvate, not scarious; plants larger.
I. With or without rays— 297. Senecionid-
accae.

F. Pappus mostly capillary, plants usually

rather large and stout.

I. Tnvolucral bracts much imbricated.

1. Flowers all tubular, receptacle usu-
' ally bristly— 298. Carduaceae.

II. Invoiucral bracts little imbricated.

1. Flowers all labiate, receptacle usu-
ally naked— 299. Mutisiaceae.

2. Flowers all ligulate, receptacle usu-
ally naked— 300. Lactucaceae.

Family 287. Helianthaceae. Sunflowers. Herbs;
calyx not capillary; receptacle chaffy;
usually rayed; mostly large, coarse
plants.— Helianthus, Zinnia, Rud-
beckia, Silphium.
Family 288. Ambrosiaceae. Ragweeds. Herbs;
calyx not capillary; receptacle chaffy;
rayless; mostly large, coarse plants.
—Ambrosia, Xanthium.
Family 289. Heleniaceae. False Sunflowers. Herbs;
calyx not capiUary; receptacle naked;
rayed or rayless; anthers tailless;
medium sized plants.— Helenium,
Gaillardia.
Family 290. Arctotidaceae. Gazanias. Herbs; calyx
not capillary; receptacle naked;
anthers tailless. South African plants.
— Gazania, Arctotis.
Family 291. Calendulaceae. Marigolds. Herbs;
calyx not capillary; receptacle naked;
anthers tailed. Old AVorld jilants,
mostly tropical— Calendula.
Family 292. Inulaceae, Everlastings. Herbs, with
some shrubs and small trees; calyx
from bracteose to capillary; receptacle
usually naked; anthers tailed; usu-
ally rayless; mostly low plants.—

376 THE PLANT PHYLA

Antennaria, Gnaphalium, Helichry-
sum, Inula.

Family 293. Astcraceae. Asters. Herbs and under-
shrubs; calyx from bracteose to capil-
lary; receptacle naked; usually rayed;
medium sized plants. — Aster, Solid-
ago, Erigeron, Bellis, Baccharis.

Family 294. Vernoniaceae. Ironweeds. Herbs;
calyx from bracteose to capillary;
receptacle naked; rayless; style-
branches fiUform, hispidulous; me-
dium sized plants. — Vernonia, Ele-
phantopus.

Family 295. Eupatoriaceae. Blazing Stars. Herbs;
calyx from bracteose to capillary;
receptacle naked; rayless; style-
branches thickened upward, papillose;
medium sized plants. — Lacinaria,
Eupatorium, Kuhnia.

Family 296. Anthemidaceae. Camomiles. Herbs,
shrubs, and small trees; calyx a short
crown or wanting; receptacle chaffy or
naked; usually with white rays;
mostly medium sized plants. — An-
themis, Chrysanthemum, Artemisia.

Family 297. Senecionidaceae. Groundsels. Herbs,
shrubs, and trees; calyx capillary;
receptacle naked; rayed or rayless;
mostly medium sized plants. — Sene-
cio, Arnica.

Family 298. Carduaceae. Thistles. Herbs; calyx
mostly capillary; receptacle usually
bristly (not chaffy); rayless; mostly
stout plants. — Carduus, Arctium,
Cnicus.

Family 299. Mutisiaceae. Mutisias. Herbs, shrubs,
and small trees; calyx mostly capil-
lary; receptacle usually naked; flow-
ers all two-lipped, so no proper rays;
mostly medium sized tropical plants.
— Mutisia, Chaptaha.

ANTHOPHYTA 377

Family 300. Lactucaccae. Lettuces. Herbs with a
milky juice; calyx mostly capillar}'-;
receptacle usually naked; flowers all
ligulate, so no proper rays; medium
sized to small plants. — Lactuca, Hier-
acium, Cichorium, Taraxacum, (Leon-
todon).

REFERENCE BOOKS

A. Engler and K. Prantl, Die NaturUchen Pflamenfamilien,
Leipzig, 1889 to 1909.

C. E. Bessey, A Synopsis of Plant Phyla, Lincoln, 1907.

A. Engler and E. Gilg, Syllabus der Pflanzenfamilicn, Berlin,
1912.

C. E. Bessey, Revisions of Sortie Plant Phyla, Lincoln, 1914.

Chart to Show Relationship of the Plant Phyla.

Chart TO Show Relationship of the Ohdehs of Anthophyta.

APPROXIMATE NUMBERS OF SPECIES IN THE ORDERS
OF ANTHOPHYTA.

Alismatales. 409; Liliales, 3370; Arales, 1052; Palmalcs. 1085;
Graminales, 5795; Hydrales, 53; Iridales, 4419; Orchidales, 7578;
Ranales, 5551; Malvales, 3829; Sarraconiales, GO; Gcranialos, 92G8;
Guttifcralcs, 3138; Rhoedales, 2856; C'aryophyllalos, 4330; Priinulalcs,
1581; Ericales. 1730; Ebonalcs, 1136; Polcmoniales, 4112; Gentian-
ales, 4664; Scrophulariales, 7081; Lamiales. 4119; Resales, 14261;
Myrtales, 7323; Cactales, 1168; Loasales, 1392; Cclastrales, 2741;
Sapindalcs, 2903; Umbellales, 2809; Rubialcs, 5063; Campanulales,
1539; Astcralcs, 14324.

INDEX

Abies, 281, 356
Abiotaccae, 279, 356
Abrotanin, 149
Abutilon, 362
Acacia, 368
Acanthaceac, 367
Acarospora, 340
Acarosporaceae, 340
Acer, 371
Aceraccae, 371
Acervuli, 239
Acetabularia, 192, 336
Acetic acid, 140
Achariaceae, 364
Achene, 312
Achlya, 335
Acids, 18, 139
Aconitin, 149
Acorn, 311, 325
Acorns, 300, 358
Acrocarpi, 252, 349
Acrospermaccae, 343
Acrotylaceae, 339
Actinocyclus, 334
Actinodiscaceae, 334
Actinodiscus, 181, 334
Actinoniorphic. 292, 322
Adder-tongues, 257, 352
Adiantuni, 259, 353
Adoxaceae, 373
Aecidiaceae, 347
Aecidiospores, 233
Accidium, 234, 347
Aeciospores, 233
Aerobic respiration, 91
Aesculin, 149
Aesculus, 371
Agaricaccac, 229
Agaricales, 229, 345
Agarics, 345
Agaricus, 229, 345

Agathis, 279
Agave, 320, 360
Agrostideae, 359
Agrostis, 359
Aizoaceae, 364
Alaria, 337

Albuginaceae, 187, 335
Albugo, 188
Albumens, 151
Albuminoids, 152
Albumoses, 152
Alcohols, 141
Aleuron, 14
Alisma, 289, 357
Alismataceae, 357
Alismatales, 295, 357
Alkaloids, 18, 149
Allium, 300, 358
Almond, 314
Alnus, 372
Alsine, 364
Alsophila, 352
Alternate leaves, 292
Alternation of Generations, 242
Althaea, 305, 362
Alyssum, 364
Amanita, 345
Amaranthaceae, 365
Amaranthus, 365
Amaryllidaceae, 360
Amaryllis, 298, 360
Amaryllises, 360
Amblystegium, 351
Ambrosia, 375
Ambrosiaceae, 375
Ampelopsis, 371
Amphipleura, 334
Amphisi)haeriaceae, 343
Amygdalin, 148
Amygdalus, 368
Amylase, 153

381

382

INDEX

Aniyluni, 147
Anabacna, 165
Anacardiaceae, 372
Anaerobic respiration, 91
Ananas, 360
Anauliaceae, 334
Ancistrocladaceae, 370
Ancylistaceae, 335
Andreaea, 251, 349
Andreaeaceae, 349
Andreaeales, 251, 349
Andropogon, 360
Andropogoneae, 360
Anemone, 291, 361
Anemophilous, 321
Angiopteris, 352
Angiospermous, 330
Animal Kingdom, 171
Animals, 172, 332
Anogra, 370
Anomodon, 351
Anonaceae, 361
Antennaria, 376
Anthemidaceae, 376
Anthemis, 376
Anther, 292
Antheridial cells, 174

disks, 246

gametophytes, 258
Antherids, 186
Anthoceros, 245, 349
Anthocerotaceae, 349
Anthocerotales, 349
Anthocyanin, 156
Anthophyta, 284, 357
Anthostoma, 343
Antipodal nuclei, 287
Antirrhinum, 304, 367
Aphanocapsa, 164
Apiaceae, 372
Apical cell, 43
Apium, 372
Apocarpous, 292
Apocynaceae, 366
Apocynum, 367
Apogamy, 324
Aponogetonaceae, 357
Apopetalous, 305
Apothccia, 215
Appendages, 221
Apple, 307

Apple, Blight bacteria, 169
Apples, 368
Aquifoliaceae, 371
Arabinose, 145
Araceae, 358
Arachnoidiscus, 334
Arales, 295, 358
Aralia, 372
Araliaceae, 372
Araucaria, 279, 356
Araucariaceae, 278, 356
Araucarioxyleae, 354
Arbutin, 149
Archegone, 110, 243
Archegonial gametophytes, 258
Archespore, 272, 292
Archidiaceae, 349
Archiplastideae, 164, 330
Arctium, 376
Arctostaphylos, 365
Arctotidaceae, 375
Arctotis, 375
Argemone, 364
Arisaema, 300, 319, 358
Aristolochiaceae, 370
Arnica, 376
Aromatic oils, 143
Artemisia, 376
Arthonia, 218, 342
Arthoniaceae, 342
Arthrocladiaceae, 337
Arthothelium, 342
Arum, 358
Aschersonia, 347
Asclepiadaceae, 367
Asclepias, 367
Ascobolaceae, 342
Ascobolus, 342
Ascocorticiaceae, 341
Ascocorticium, 341
Ascoidaceae, 344
Ascophyllum, 337
Ascosporeae, 211, 339
Ascospores, 213
Ascus, 213

Fungi, 213, 339
Aseroe, 345

Asexual reproduction, 109, 171
Ash, 324

Asimina, 274, 361
Asparagin, 154

INDEX

383

Asparagus, 358
Aspergillaceae, 344
Aspergillales, 344, 222
Aspergillus, 221, 344
Aspidium, 259
Asplenium, 259, 353
Assimilative processes, 84
Aster, 376
Asteraceae, 376
Asterales, 311, 373
Asters, 376
Astrotheliaceae, 343
Atriplex, 365
Atropa, 366
Atropine, 150
Aulocomniaceae, 350
Auricularia, 346
Auriculariaceae, 346
Aurioulariales, 230, 346
Austrian Pine, 282
Autonomous movements, 121
Aiixanometer, 108
Auxiliary cells, 208
Avena, 300, 359
Aveneae, 359
Axes of flowers, 301
Axiflorae, 301

-Apopetalae-Polycarpellatae,
361

-Gamopetalae-Dicarpellatae,
366

-Gamopetalae-Polycarpellatae,
365
Axis Flowers, 301, 302, 361

(of flower), 285
Azolla, 353

Baccharis, 376
Bacillaria, 181
Bacillariaceae, 334
Bacillarioideae, 177, 179, 333
Bacillus, 331
Bacteria, 166, 331
Bactoriaroae, 331
liactcrialcs, 166, 331
liactcrium, 331
Balanophoraceac, 371
Balanopsidaceae, 3()2
Bald Cypresses, 278

lialsamia, 344
Balsamiaceae, 344, 363
Bamboo, 297, 359
Bambusa, 359
Bambuseae, 359
Banana, 301
Bananas, 360
Bangiaceae, 338
Bangiales, 338
Bangioideae, 207. 338
Banner, 308
Barberry, 319
Barbula, 350
Barley Smut, 237
Bartramiaceae, 350
Basellaceae, 364
Basidia, 226

Basidiosporeae, 211, 226, 344
Basidiospores, 226
Basidium Fungi, 226, 344
Bast fibers, 33
Batidaceae, 365
Batrachospermum, 209, 338
Battarca, 345
Bazzania, 349
Bean, 314

Family, 309
Beans, 368
Bed straw, 325
Beeches, 372
Beetle Fungi, 339
Beggiatoa, 331
Beggiatoaceae, 331
Begonia, 370
Begoniaceae, 370
Begonias, 370
Bcllis, 376
Bellworts, 373
Bennettitaceac, 355
Bennettitales, 355
Bcnnettitos, 274
Bennettitineae, 274, 355
Benzoic acid, 141
Beomyccs, 340
Berberidaceae, 361
Berberin, 150
liergamot oil, 11 4
Berries, 326
Berry, 309
Beta, 365
Betula, 372

384

INDEX

Betulaceae, 372
BicoUateral bundles, 59
Bicuculla, 364
Biddulphiaccae, 334
Bignonia, 3G7
Bignoniaceae, 367
Birches, 372

Bird-nest Fungi, 228, 345
Bixaceae, 363
Black Blast, 237

-dot Fungi, 239, 348

Knot, 219

Molds, 189, 335

Mosses, 251, 349

Rust, 233
Bladder Algae, 192, 336

-fern, 259

Kelp, 201
Blanc mange, 209
Blazing Stars, 376
Blue Greens, 164, 330

Molds, 222

-stem Grasses, 360
Boehmeria, 362
Bog Mosses, 252, 351
Boletus, 346
Bombacaceae, 362
Bonnemaisoniaceae, 339
Borraginaceae, 366
Borrago, 366
Bothrodendraceae, 354
Botrychium, 352
Botrydiaceae, 336
Botrydium, 192, 336
Botryococcus, 332
Botrytis, 239, 348
Boundary tissue, 46
Bouteloua, 359
Bovista, 345
Brachytheciaceae, 351
Brake, 259

Brand-Fungi, 232, 346
Brassica, 303, 364
Brassicaceae, 364
Breathing pores, 51
Breeding of Plants, 115
Bremia, 188
Bridal Wreath, 307
Bristle Mosses, 252, 350
Brome Grass, 297
Bromeliaceae, 360

Bromus, 297, 359
Brood cells, 247

Masses, 246, 252, 351
Broom- rapes, 321
Brown Algae, 199, 336

Seaweeds, 201
Brucine, 150
BruncUiaceae, 369
Bruniaceae, 369
Bryaceae, 252, 350
Bryales, 251, 349
Bryophyta, 242, 348
Bryopsidaceae, 336
Bryopsidoideae, 185, 336
Bryopsis, 192, 336
Bryum, 350
Buckeyes, 371
Buckthorns, 371
Bud, 45

Budding, 21, 223
Buellia, 341
Buelliaceae, 341
Bulbs, 319
Bulrush, 300
Bunt, 237
Burdock, 325
Burmanniaceae, 360
Bursa, 364
Burseraceae, 363
Butomaceae, 357
Buttercup, 286, 361
Butyl, 142
Butyric acid, 140
Buxaceae, 371
Buxbaumiaceae, 252, 351

Cabombaceae, 362
Cactaoeae, 370
Cactales, 370
Cactus, 310, 370
Cactuses, 370
Caesalpinia, 308
Caffeine, 149
Caladium, 358
Calamariaceac, 353
Calamariales, 353
Calamarineae, 264, 353
Calamites, 254, 261, 264, 353
Calamophyta, 261, 353

INDEX

385

Calamus, 358
Calendula, 375
Calcndulaccac, 375
Caliciaceae, 341
Calicialcs, 341
(^aliciuni, 341
Calla, 358

Lilies, 205
Callitriehaccae, 303
Callophyllis, 200, 339
Callymenia, 200
Caloplaca, 340
Caloplaceae, 340
Caltha, 201
Calvatia, 228
Calycanthaceae, 3G1
Calyceraceae, 373
Calyciflorae, 302

-Apopetalae, 368

-Gamopetalae, 373
Calymperaceae, 350
Calyptra, 251
Calyx, 286

Cambium, 58, 60, 260, 283
Camomiles, 376
Campanula, 373
Campanulaceae, 373
Campanulales, 373
Camphor, 144
Camphors, 143
Campsopogonaceae, 338
Camptosorus, 250
Camptotrichaceae, 331
Camptothrix, 331
Canada Thistle, 319
Canal Cells, 244
Canary Grasses, 359
Cane Sugar, 17,146
Canna, 360
Cannabis, 362
Cannaceae, 360
Caoutchouc, 144
Capparidaceae, 364
Caprifoliaceae, 373
Capsicum, 366
Capsule, 250

Carbohydrates, 13, 84, 85, 144
Carbonic Acid, 85, 139
Carduaccae, 376
Carduus, 376
Carcx, 358

Caricaceae, 364
Carnegiea, 370
Carotin, 155
Carpels, 286
Carpinus, 321, 372
Carpomycetoac. 211, 339
Carpospores, 206
Carrot, 315
Caryocaraceae, 363
Caryophyllaceae, 364
Caryophyllales, 364
Caryopsis, 298
Cassia, 368
Cassiaceae, 368
Castalia, 364
Castanea, 314, 372
Castilleia, 367
Castor Bean, 305

oil. 143
Casuarinaceae, 369
Catalase, 153
Catalpa, 367
Catascopiaceae, 350
Catkins. 321
Cat-tails, 357
Caulerpa, 107
Caulerpaceae, 336
Ceanothus, 371
Cedar-apples, 238
Cedars, 281
Cedrus, 281
Celastraceae, 371
Celastrales, 370
Celidiaceae, 342
Cell, 4

division, 10

inclusions, 13

sap. 17

wall. 5
Cellulose. 5
Celluloses. 147
Celosia, 365
Celtis, 362
Cenangiaceae, 342
Centrifugal apparatus, 131
Centrolepidiaceae, 358
Centrosomc. 2
Century Plant, 320
Ophalotaceae, 360
Ceramiaceae, 339
Ceraniiales, 338

386

INDEX

Ceramium, 339

Ceratomyces, 339

Ceratophyllaceae, 362

Ceratostoinataceae, 343

Cercidiphyllaceae, 301

Cercospora, 239, 348

Cereus, 370

Ceropegia, 367

Chaetangiaccae, 338

Chaetocerotaceae, 334

Chaetocladiaceae, 335

Chaetocladium, 335

Chaetomiaceae, 343

Chaetophora, 173, 332

Chaetophoraceae, 332

Chaetophorales, 332

Chalazal, 279

Chamaecyparis, 356

Chamaerops, 358
^hamaesiphon, 330

Chamaesiphonaceae, 330

Chaptalia, 376

Chara, 193, 336
•,'Characeae, 194, 336

Charales, 193, 336

Chemistry of the plant, 139

Chemotaxy, 119

Chemotropism, 127

Chenopodiaceae, 365

Chenopodium, 365

Cherry, 314, 325

Chestnut, 314

Chiodectonaceae, 342

Chitin, 5, 154

Chlaenaceae, 362
ji(fehlamydomonas, 173

Chlamydosporcs, 184

Chloranthaceae, 361

Chlorideae, 359
, Chlorococcaceae, 332
.:^hlorococcum, 171, 332
'^Chlorophyceae, 170, 332

Chlorophyll, 11, 155

Chlorophyllan, 155

Chloroplasts, 2, 11, 84

Cholera bacteria, 169

Chondromyces, 331

Chondrus, 208, 339

Chordariaceae, 337

Choristocarpaceae, 337

Christmas decorations, 267

Chromatin, 2

Chromatium, 331

Chromoplasts, 2, 12

Chromosome number, 110

Chromosomes 22, 110

Chroococcaceac, 164, 330
hroococcus, 164, 330
hrysanthemums, 376

Chrysothricaceae, 340

Chytridiaceae, 336

Chytridium, 336

Cichorium, 377

Cicuta, 372

Cilia, 118

Cinchona, 373

Cineol, 144

Circaea, 370

Circinately, 256

Circumnutation, 123

Cistaceae, 363

Citral, 144

Citric acid, 141

CitruUus, 370

Citrus, 363

Cladochytriaceae, 335

Cladonia, 216, 340

Cladoniaceae, 340

Cladophora, 185, 334

Cladophoraceae, 334

Cladophorales, 334

Cladosporium, 348

Cladoxyleae, 354

Classes, 159

Classification of plants, 157

Clathraceae, 345

Clathrus, 345

Clavaria, 346

Clavariaceae, 230, 346

Claviceps, 220, 343

Claytonia, 323, 364

Clematis, 361

Clethraceae, 365

Climaciaceae, 252, 351

Climacium, 351

Climbing Ferns, 258

Closed bundles, 58
Fungi, 218, 343
Lichens, 218, 342

Closteriaceae, 179, 333

Closterium, 179, 333

Clover-nodule bacteria, 169

INDEX

387

Club-Mosses, 267. 354
Cluster-cups, 233
Cneoraccae, 363
Cnicus, 376
Cocaine, 150
Coccaceae, 331
Cocci, 166

CoccoKonalos, 164, 330
Coccoloba, 365
Cochlospermaceac, 363
Cocklebur, 324
Coconut, 296, 324
Cocos, 296, 358
Codiaceao, 334
Codiuni, 195, 334
Cocnobiales, 172, 332
Coenocytes, 8, 172
Coenogoniaceae, 340
Coffea, 373
Coffees, 373

Coleochaetaceae, 174, 333
Coleochaetales, 333
Coleochaete, 174, 333
Coleosporiaceae, 347
Coleosporium, 347
Coleus, 367
Collateral bundles, 58
Collema, 216, 340
CoUemataceae, 340
Collenchyma, 32
Colletia, 371
CoUetotrichum, 240, 348
Colon bacteria, 169
Colors of flowers, 322
Columelliaceae, 367
Combretaceae, 370
Commelina, 358
Commelinaceae, 358
Common Cycads, 272, 354

Ferns, 258, 353

Horsetail. 264
Companion cells, 39
Composites, 312, 373
Compound pistil, 295
Concentric bundles, 57
Conceptades. 202
Conducting System, 54
Confervas, 173, 332
Confervoideae, 171, 173, 332
Conidia, ISS
Conidiophore, 188

Coniferales, 356
Conifer Ancestors, 275, 355
Coniferin, 148
Conifers, 277, 355
Coniine, 150
Conjugatae, 177, 333
Conjugate Algae, 177, 333
Conjugation, 182
Connaraceae, 368
Conocephalus, 349
Constituents of plants, 82
Convolvulaceac, 366
Convolvulus, 366
Coprinus, 345
Coral Fungi, 230, 34G
Corallina, 207, 338
Corallinaceae, 338
Corallines, 207
Cordaitaceae, 355
Cordaitales, 275, 355
Cordaites, 275
Cordaitineae, 355
Cordieritidaceae, 342
Cordyceps, 343
Core (apple), 308
Coreopsis, 315
Coriandrum, 372
Coriariaceae, 371
Cork, 67
Corms, 319
Cornaceae, 372
Cornels, 372
Corn (Indian), 298

Smut, 236
Cornus, 322, 372
Corolla, 286
Corsiniaceae, 349
Corticium, 346
Corylus, 372
Corynocarpaceae, 371
Coscinodiscaceae, 334
Coscinodiscus, 181, 334
, Cosmariaceae, 179, 333
r^Cosmarium, 179, 333
Cotinus, 372
Cotton. 305

Cotyledons. 268, 282, 293
Cow Parsnip, 315
Crassulaceae, 369
Crataegus, 313, 368
Crenothrix, 331

388

INDEX

Crocus, 360
Cronartium, 347
Crossosomataceae, 368
Croton, 363

oil, 143
Crotonic acid, 143
Crown-gall bacteria, 169
Crucibulum, 345
Crucigenia, 332
Cryphacaccae, 351
Cryptoneniialcs, 338
Crystals, 15

Cucumber-wilt bacteria, 169
Cucumis, 370
Cucurbita, 305, 370
Cucurbitaceae, 370
Cucurbitariaceae, 343
Culture solutions, 97
Cunoniaceae, 369
Cup Flowers, 302, 300, 367

-fungi, 216, 341
Cuphea, 369
Cupressaceae, 282, 356
Cupressus, 356
Currant, 309
Cuscuta, 320, 366
Cushion Mosses, 252, 349
Cutin, 155
Cutleriaceae, 337
Cutleriales, 337
Cyanastraceae, 358
(Cyanophyceae, 330
Cyathea, 352
Cyatheaceae, 258, 352
Cyathus, 345
Cycadaceae, 354
Cycadales, 354
Cycadineae, 272, 354
Cycadophyta, 271, 354
Cycads, 271, 354
Cycas, 273, 354
Cyclamen, 365
Cyclanthaceae, 358
Cyclosporeae, 337
Cydonia, 313
Cylindrocapsa, 333
Cylindrocapsaceae, 333
Cylindrospermum, 165, 331
( 'ylindrosporium, 346
Cymathere, 201
Cynocrambaceae, 365

Cynomoriaceae, 370
Cyperaceae, 298, 358
Cyperus, 301, 358
Cypheliaceae, 341
Cyphelium, 341
Cypresses, 282, 356
Cypripedium, 299, 301
Cyrillaceae, 371
Cystocarp, 110, 206
Cytase, 152
Cytology, 1
Cytoplasm, 1
Cyttariaceae, 342

Dacryomycetaceae, 346
Dahlias, 320

Dandelion, 312, 313, 324
Dasya, 209, 339
Dasycladaceae, 336
Dasycladales, 336
Dasycladus, 336
Dasyscypha, 342
Datiscaceae, 370
Datura, 366
Daucus, 315, 372
Dead nettle, 306
Death from disease, 136
Death of plants, 95
Delesseria, 339
Delesseriaceae, 339
Dematiaceae, 348
Dematium, 348
Derbesiaceae, 336
Dermatocarpaceae, 343
Dermatogen, 44
Desmarestiaceae, 337
Desmidiaceae, 178, 333
Desmidiales, 333
Desmidium, 333
Desmids, 178, 333
Devil's aprons, 200
Dextrose, 145
Dextro-tartaric acid, 141
Dianthus, 300, 364
Diapensiaceae, 305
Diaporthe, 343
Diastase, 153
Diatomin, 156, 179
i4Diatoms, 179, 333

INDEX

389

Diatrj-paceae, 343
Dicaeoina, 347
Dichacnaceac, 343
Dichapctalaccao, 363
Dichoniyces. 339
Dicksonia, 352
Diclinous, 29G

Dicotylcdoneae, 294, 301, 361
-Axiflorae, 361
-Calyciflorap, 367
Dicotyledons, 301, 361
Dicranaceae, 252, 349
Dictyophora, 345
Dictyosiphonaceae, 337
VDictyota, 337
'^Dictyotaceae, 337
Dictyotineae, 337
Digitalis, 306
Dilleniaceac, 362
Dimorphism, 323
Dioecious, 273
Dioon, 355
Dioscoreaceae, 360
Diphtheria bacteria, 169
Diploid, 24, 110
Diploschistaceae, 340
Dipsacaceae, 373
Dipterocarpaceae, 363
Dirinaceae, 342
Disaccharids, 146
Disceliaceae, 350
Discella, 348
Discolichenes, 214, 340
Diseases of Plants, 133
Disc Algae, 174
flowers, 312
Lichens, 214, 340
Division of cells, 19
Dodder, 320, 321
Dodecatheon, 365
Dogwood, 322
Dothidia, 343
Dothidiaceae, 343
Downy Mildews, 187, 335
Draparnaldia, 173, 332
Drci)anophyllaceae, 350
Droseraceae, 369
Duchesnea, 291
Duckweeds, 358
Dulcite, 142
Dumontiaciae, 338

Durvillaea, 337
Durvillaeaceae, 337
Dutch Rush, 264
Dwarf males, 174

Ears, 298

Ear Fungi, 230. 346
Earth Stars, 231
Ebenaceac, 366
Ebenales, 365
Echinocactus, 370
Ectocarpaceae, 337
Ectocarpales, 337
Ji^ctocarpus, 200, 337
Ectolechiaceae, 340
Egg, 110, 174
Egregia, 201, 337
Elachistaceae, 337
Elaeagnaceae, 371
Elaeocarpaceae, 362
Elaphomycetaceae, 34
Elaters, 245, 263
Elatinaceae, 364
Elder, 315
Elephantopus, 376
Elms, 362
Embryo, 280
Emergencies, 51
Empetraceae, 371
Emulsin, 153
Encalypta, 350
Encoeliaceae, 337
Endocarpon, 218
Endomyces, 341
Endomycetaceae, 341
Endosperm, 274. 284, 288

nucleus, 288
Endospores, 166
Energy, 90

supply of, 91
Enteromorpha, 174, 332
Entodontaceac, 351
Entomophilous, 321
Entomophily, 323
Entomophthora, 191, 336
Entomophthoraceae, 191, 336
Entomojihthoralcs, 336
Entyloma, 347
Enzymes, 152
Epacridacoae, 3(>5

390

INDEX

Ephebaceae, 340
Ephebe, 216
Ephedra, 275, 355
Ephedraceae, 355
Ephemeral Mosses, 252'
Ephemerum, 252, 350
Epicoccum, 348
Epidermal System, 47
Epidermis, 48
Epigloea, 342
Epiglueaceae, 342
Epilobium, 370
Epiplasm, 24
Equisetaceae, 263, 353
Equisetales, 353
Equisetineae, 262. 353
Equisetum, 262, 353
Eremascus, 341
Ergot, 220
Erica, 365
Ericaceae, 365
Ericales, 365
Erigeron, 376
Eriocaulonaceae, 358
Eriogonum, 365
Erodium, 362
Erpodiaceae, 351
Erysiphaceae, 220, 344
Erysiphe, 220, 225, 344
Erythronium, 300, 357
Erythroxylaceae, 363
Eschscholtzia, 364
Ethyl alcohol, 141
Euastrum, 179
Eubacteria, 331
Eucalyptol, 144
Eucalyptus, 370

oil, 144
Eucomiaceae, 369
Eucryphiaceae, 363
Eugenia, 370
Euodiaceae, 334
Eupatoriaceae, 376
Eupatorium, 376
Euphorbia, 322, 363
Euphorbiaceae, 363
Eupodiscaceae, 334
Eupodiscales, 181, 333
Eupodiscus, 334
Eusporangiatae, 257, 352
Eustoma, 366

Evaporation of water, 74, 75
Evening Primrose, 309, 370
Everlastings, 375
Evolution, 160

of Anthophyta, 316
Evolvulus, 366
Excipula, 348
Excipulaceae, 348
Exidia, 346
Exoascaceae, 341
Exoascalcs, 218, 341
Exoascus, 218, 341
Exobasidiaceae, 346
Exobasidiales, 231, 346

Fabaceae, 368

Fabroniaceae, 351

Fagaceae, 372

Fagopyrum, 365

Fagus, 372

False Hemlocks, 281
Sunflowers, 375
tissues, 28
Tubers, 227, 344

Families, 159

Fats, 14, 142

Fatty oils, 142

Fermentation, 223

Ferns, 254

Fertilization of the egg, 273

Ferula, 372

Fescue Grasses, 359

Festuceae, 359

Fibrous tissue, 33

Fibrovascular system, 47

Ficus, 362

Figs, 362

Filament, 292

Filicales, 258, 352

Filix, 259

Filmy Ferns, 258, 352

Firs, 281

First stom'ata, 245

Fissidentaceae, 350

Fission, 20

Flacourtiaceae, 362

Flagella, 118

Flagellariaceae, 358

Flagellata, 172

INDEX

391

riat Diatoms, 181, 334

Kelps, 200
Florideae, 207, 338
Flower, 274, 285

axes, 301
Flowering Plant Ancestors, 274,
355
Plants, 274, 284, 357
"Flower" of Mosses, 250
Fly Fungi. 33G
Foeniculum, 372
Fomes, 230, 346
Fontinalaceae, 252, 351
Forget-me-nots, 3G6
Formaldehyde, 85, 153
Formation of New Cells, 19
Formic Acid, 140
Fossombronia, 349
Fouquieraceae, 3G4
Fragaria, 289, 306, 368
Fragiiariaceae, 334
Frankeniaceae, 364
Fraxinus, 366
Free veins, 257
Freezing of plants, 96
Froelichia, 365
Fructose, 18, 145
Fruit, 288

-spores, 175
Sugar, 145
FruUania, 349
Fucaceae, 337
Fucales, 201, 337
Fuchsia, 370
^^ucus, 201, 337
' Funaria, 250, 350
Funariaceae, 252, 350
Fungi, 179, 211

Imperfecti, 213, 347
Fungus cellulose, 5, 154

sugar, 146
Fusarium, 34S
Fusel oil, 142
Fusidadium, 239, 348

Gaillardia, 375
Galactose, 145
Galium. 373
Gall-fungi, 172

Gallic acid, 141

Gallotannic acid, 141

Gametangia, 200

Gametes, 109

Gametophyte, 110, 242

Gamopetalous. 303

Gamosepaly, 304

Garden Currant, 309

Gaura, 370

Gazania, 375

Gazanias, 375

Geaster, 231, 345

Geissolomataceae, 371

Gelidiaceae, 338

Gemmae, 246

Genera, 158

Generation, 171

Genicularia, 333

Gentiana, 366

Gentianaceae, 366

Gentianales, 366

Geoglossaceae, 342

Geoglossum, 342

Geologic time, 161, 162
Georgiaceae, 351
Geotropism, 125
Geraniaceae, 362
Geraniales, 362
Geranium, 302, 362
Geraniums, 362
Gerardia, 367

Germination of seed, 281, 288
Gesneraceae, 367
Geum. 291
Giant Kelp, 201

Puff-I)all. 228
Gigartina. 339
Gigartinaceae, 339
Gigartinales, 339
Gilia, 366
Gills, 230
Ginkgo, 275, 355
Ginkgoaceae, 355
Ginkgoales. 275, 355
Ginsengs, ',i7'2
Girdle. ISO
Gladiolus. 319, 360
Glaucocystaceae, 167, 332
Glaucocystales, 167, 332
Glaucocystis, 167, 332
Glcba, 228

392

INDEX

Gleditsia, 368
Gleicheniaceae, 352
Globulariaceae, 307
'Gloeocapsa, 164, 330
Gloeosporium, 239, 348
Gloiosiphoniaccae, 338
Glucose, 18, 85, 145
Glucosides, 148
Glume, 297
Glycerine, 142
Glycogen, 147
Glycollic acid, 140
Gnaphaliuni, 376
Gnetaceue, 355
Gnetales, 275, 355
Gnetum, 275, 355
Gnomoniaceae, 343
Golden Fern, 258
Gomortegaceae, 361
Gonatonema, 333
Gonidia, 214
Gonium, 332
Gonystylaceae, 362
Goodeniaceae, 373
Gooseberries, 314, 369
Gordonia, 363
Gossypium, 305, 362
Grain (of grass), 298
Graminales, 297, 358
Gramma Grasses, 359
Grammatophora, 334
Grapes, 326, 371
Grape Sugar, 18, 145
Graphidaceae, 342
Graphidales, 218, 342
Graphina, 342
Graphis, 218, 342
Graphium, 348
Grasses, 297, 359
Grasshopper Fungus, 191
Grateloupiaceae, 338
Gray Mosses, 214
Great Horsetail, 264

Liverwort, 246, 349
Green Felts, 185, 334

Slimes, 171, 332
Grimmiaceae, 350
Grinnellia, 209, 339
Grippe bacteria, 169
Grossulariaceae, 369
Ground Pines, 267, 354

Groundsels, 376
Growing point, 45
Growth, 104

movements, 122

rings, 62
Grubbiaceae, 371
Gulfweeds, 201
Gum canals, 66
Gutta Percha, 144
Guttation, 77
Guttiferaceae, 363
Guttiferales, 363
Gyalectaceae, 340
Gymnoascaceae, 344
Gj^mnoascus, 344
Gymnocladus, 368
Gymnogramme, 258
Gymnospermous, 330
Gymnosporangium, 235
Gyrophoraceae, 340

Habitat, 320
Hadromal, 154
Haematococcus, 173
Haemodoraceao, 360
Hair-cap Mosses, 252
Hair Caps, 351
Hairs, 49
Halicystis, 336
Halidrys, 337
Halimeda, 195
Halophytes, 320
Halorrhagidaceae, 370
Hamamelidaceae, 369
Haploid, 24, 110
Haplosiphon, 165
Hard Puff-balls, 344

Red Seaweeds, 338
Haustoria, 188
Hawkweed, 324
Hawthorn, 313
Heartwood, 62
Heaths, 365
Hedera, 372
Hedwigiaceae, 351
Heleniaceae, 375
Helenium, 375
Helianthus, 311, 312, 375
Hclianthaceae, 375

INDEX

393

Helichrysuni, 376

Helicophyllaceae, 351

Holiotropiuni, 366

llelinintliooladiaceae, 338

llelotiaeoao, 342

Hclotiuni, 342

Helvella. 342

Helvellaccae, 342

Hclvellalcs, 217, 342

Ilelvellas, 342

Hcniiascales. 223, 344

Hemlocks, 281

Hepatica, 291

Hepaticac, 244, 348

Heppiaceae. 340

Heptane, 153

Heracleum, 315, 372

Herbarium Mold, 221

Hernandiaceae, 371

Herposteiraceae, 333

Herposteiron, 333

Hesperidin, 149

Heterocysts, 165

Heteroecism, 234

Heterogametes, 174

Heterogamous, 110

Heterospores, 255

Heterothallic, 191

Heuchera, 369

Hibiscus, 362

Hickory, 314

Hicoria, 314, 372

Hieracium, 377

Higher Fungi, 211, 330
Lycopods, 267, 354
Red Seaweeds, 339
Tube Algae, 336

Highest plant, 313

Himanthalia, 337

Himanthaliaceae, 337, 371

Hippocrateaceae, 371

Hippuridaceae, 370

Histology. 27, 43

Hollyhock, 305

Holophytes, 88

Holoplastideae, 164, 167, 332

Homothallic. 197

Honey Locust, 319

Honeysuckle, 311, 373

Hookeriaceae, 351

Hormogonales, 165, 330

Hormogones, 163
Hornworts, 245, 349
Horsemint, 306
Horsetails, 262, 353
Houstonia, 373
Hoya, 367
Humiriaceae, 363
Humpback Mosses, 252, 351
Humulus, 362
Husks, 298
Hyacinth, 320
Hyaloriaceae, 346
Hyalothcca, 333
Hydnaccae, 230, 346
Hydnoraceae, 370
Hydnum, 346
Hydrales, 360
Hydrangea, 369
Hydrangeaceae, 360
Hydrocharitaceae, 360
Hydrochinin, 150
Hydrochloric acid, 139
Hydrocyanic acid, 148
Hydrodictyaceae, 332
Hydrodictyon, 172, 332
Hydrophyllaceae, 366
Hydrophyllum, 366
Hydrophytes, 320
Hydrostachydaceae, 364
Hygroscopic movements, 116
Hymenium, 213, 226
Hymenogastraceae, 344
Hymenogastrales, 227, 344
Hymenophyllaceae. 258, 352
Hymenophyllum, 352
Hyoscyamine, 150
Hyperplasy, 134
Hypertrophy, 134
Hyphae, 189
Hypnaceae, 252, 351
Hypnodendraceae, 351
Hypnum, 351
Hypochnaceac, 34G
Hypocreaceae, 343
Hypoderniataceae, 343
Hypoplasy, 134
Hypopterygiaccae, 351
Hyijoxis, 360
Hy poxy Ion, 343
Hysterangiuni, 344
Hysteriaceae, 343

394

INDEX

Hysteriales, 218, 343
Hysterium, 343
Hysterographiuni, 218, 343
Hysterophytes, 88

Icacinaceae, 371
Immunity to diseases, 137
Impatiens, 363
Imperfect Fungi, 347
Imperfecti (Fungi), 213
Increased parental care, 110
Indian Corn, 298
Smut, 236

Pipes, 321
Indusium, 273
Inferior ovary, 298
Influenza bacteria, 169
Inheritable variations, 113
Inorganic Acids, 139

Salts, 139
Inula, 376
Inulaceae, 375
Inulin, 18, 147
Insect Fungi, 191
Insectivorous Plants, 362
Integument, 273
Intercellular spaces, 65
Interzones, 180
Invertase, 152
Involucre, 311, 312
Ipomoea, 366
Iridaceae, 360
Iridales, 298, 360
Iris, 299, 360
Irish Moss, 208
Ironweeds, 376
Irpex, 346

Irregular flowers, 303, 322
Isaria, 348
Isobutyl, 142

carbinol, 142
Isobutyric acid, 140
Isoetaceae, 352
Isoetales, 258, 352
Isoetes, 260, 352
Isogametes, 171
Isogamous, 110
Isospores, 255
Ithyphallus, 345

Jambosa, 370
Jasminum, 366
Jelly Fungi, 230, 346
Jelly Lichens, 216
Jerusalem Artichoke, 320
Joint-firs, 275, 355
Juglandaceae, 372
Juglans, 310, 372
Julianaceae, 372
Juncaceae, 358
Juncus, 358
Jungermannia, 247
Jungermanniaceae, 247, 349
Jungermanniales, 247, 349
Juniperaceae, 282, 356
Junipers, 282
Juniperus, 356

Kalmia, 365

Karyokinesis, 20

Keel, 308

Kelps, 200, 336

Kernel (of grass), 298

Key to families of Asterales, 374

to the Phyla, 328
Kinoplasm, 22
Klinostat, 131
Knot-grass, 326
Koeberliniaceae, 364
Koelreuteria, 371
Kuhnia, 376

Laboratory suggestions, 8
Laboulbenia, 339
Laboulbeniaceae, 339
Laboulbeniales, 339
Lachnea, 342
Lacinaria, 376
Lacistemaceae, 361
Lactic acid, 141
Lactoridaceae, 361
Lactose, 146
Lactuca, 315, 377
Lactucaceae, 377
Lady's Slipper, 301

INDEX

395

Lagonaria, 370
Lamb's (luarters, 326
Lainiarcao, 307
Lainialos, 307
Laininaria, 200, 337
Laminariaooae, 200, 337
Lamium, 30G
Laniprothaninus, 336
Land Ferns, 2o2, 258

Habit, 242
Lantana, 367
Larches, 281
Lardizal)alaceae, 301
Lar^e Bladder Algae, 331
Larix, 281, 350
Lasiosphaeria, 343
Latex, 39
Lathyrus, 314
Laticiferous tissue, 39
Lauraceae, 301
Lavandula, 307
Lavender oil, 144
Laver, 207
Leafy Kelp, 201
Leathery fungi, 230
Leaves, 247, 249, 255
Lecanactidaceae, 340
Lecanora, 340
Lecanoraccae, 340
Lccidiaceae, 340
Lccythidaceae, 369
Legume, 309
Leitneriaceae, 361
Lejolisia, 339
Lenianeaceae, 338
Lenibophyllaceae, 351
Lemma, 297
Lemna, 358
Lemnaceae, 358
Lennoaceae, 305
Lentibulariaceae, 367
Lenticels, 68
Leontodon. 312, 377
Lepidodendraceae, 354
Lepidodcndrales, 269, 354
Lepidodendrids. 269
Lopidodcndriiieae, 267, 354
Lepidodcndron, 269
Lepidnphyta, 266, 354
Leptodon, 351
Leptogium, 210, 340

Leptosporangiatae, 258, 352

Leptostomataceae, 350

Leptostroma, 347

Lcptostromataceae, 347

Leptothyrium, 347

Lepyrodontaceae, 351

Leskea, 351

Leskeaceae, 351

Lessonia, 201

Lettuces, 377

Leucobryaceae, 252, 349

Lcucodontaceae, 351

Leucomiaceae, 351

Leucoplasts, 2, 12

Levulose, 145

Libocedrus, 356

Lichens, 214

Lichinaceae, 340

Light, 106

L'gnin, 5, 154

Ligulate flowers, 312

Lilac Mildew, 225

Liliaceae, 357

Liliales, 295, 357

Lilies, 295, 357

Lilium, 295, 357

Limnanthaceae, 363

Limoncne, 144

Limonia, 303

Linaceae, 303

Linalool, 144

Lindens, 302

Linin, 2

Linnaea, 373

Linoleic acid, 143

Linseed oil, 143

Lipase, 153

Lip (of orchids), 301

Lippia, 307

Liriodendron, 301

Lithospermuni, 306

Little Bladder Algae, 336

Cup-fungi, 341

Tubers. 221, 344
Liver starch, 147
Liverworts, 244, 348
Loasa. 370
Loasaccae, 370
Loasales, 370
Lobaria. 340
Lobelia, 373

396

INDEX

Locomotion of cells, 118

Lodicule, 297

Loganiaceae, 366

Lonicera, 311, 373

Lophiostomataceae, 343

Lophosia, 349

Loranthaceac, 371

Loranthus, 371

Lotuses, 361

Lower Fungi, 186, 335
Lycopods, 267, 354
Red Seaweeds, 338
Tube Algae, 334

Lupinin, 150

Lupinus, 369

Lychnis, 303, 364

Lycoperdaceae, 228, 345

Lycoperdales, 227, 345

Lycoperdon, 345

Lycopodiaceae, 267, 354

Lycopodiales, 354

Lycopodineae, 267, 354

Lycopodium, 354

Lycopods, 254, 266, 354

Lyginopterideae, 354

Lygodium, 258

Lyngbya, 165, 330

Lythraceae, 369

Lythrum, 369

Macomitrium, 350
Macrocystis, 201, 337
Macrosporium, 348
Macrozamia, 355
Magnolia, 274, 291, 302, 361
Magnoliaceae, 361
Maidenhair Fern, 259

Trees, 275, 355
Maize, 298

Grasses, 360
Malaceae, 368
Malaleuca, 370
Malesherbiaceae, 363
Malic acid, 141
Mallow, 302
Mallows, 362
Malpighiaceae, 363
Malus, 307, 368
Malva, 302, 362
Malvaceae, 362

Malvales, 362
Maltose, 146
Malt Sugar, 146
Mangifcra, 372
Manihot, 363
Manna Ash, 146
Manncotctrose, 146
Mannitc, 142
Mannose, 145
Maples, 371
Maiantaceae, 360
Marattia, 352
Marattiaceae, 352
Marattiales, 258, 352
Marattias, 258, 352
Marcgraviaoeae, 363
Marchantia, 246, 349
Marchantiaceae, 349
Marchantiales, 349
Marigolds, 375
Marsilia, 259, 353
Marsiliaceae, 353
Marsiliales, 259, 353
Martyniaceae, 367
Massariaceae, 343
Matoniaceae, 352
Mayaceae, 358
Maydeae, 360
Measurements, 9
Medicago, 369
Medullary rays, 61, 283
Medullosae, 354
Meeseaceae, 350
Megagametophytes, 258
Megasporangia, 268
Megaspores, 256, 268
Melampsora, 235, 347
Melanconiaceae, 348
Melanconiales, 239, 348
Melanconidiaceae, 343
Melanconium, 239, 348
Mclastomataceae, 369
Meliaceae, 363
Melianthaceae, 371
Melocactus, 370
Melogrammataceae, 343
Melons, 370
Melosira, 181
Mendel, 112
Menisperniaceae, 361
Mentha, 367

INDEX

397

Menthol, 144
Mentzelia, 370
Menyanthes, 300
Meridionacoac, 334

tierismopedia, 104, 330
leristeni, 29
Mertonsia, 300
Mesocarpacoao, 333
Mesophyll, 202
Mcsophytes, 320
Methane, 153
Methyl alcohol, 141
Methylamine, 153
Metzgeria, 247, 340
Metzgeriaccac, 247, 340
Micrasterias, 170, 333
Micrococcus, 331
Microcolevis, 105
Microgametophytes, 258
Micropylar end, 287
Micropyle, 273
Microsphaera, 225, 344
Microspora, 332
Microsporaceae, 332
Microsporales, 332
Microsporangia, 208
Microspores, 250, 208
Microthamniaceae, 332
Microthamnion, 332
Microthyriaceae, 344
Mildews, 220, 343
Milk Sugar, 140

tissue, 30
Milkweeds, 307
Millon's reagent,
Mimosa, 308
Mimosaceae, 308
Mimulus, 307
Mints, 307
Mitchella. 373
Mitella, 300
Mitosis, 20
Mitrula, 342
Mitteniaceae, 350
Mniaceae, 252, 350
Milium, 350
Modern Ferns, 25S. 352

Pines, 270, 35(i
Molds. 230, 348
Mollisinceae, 342
Momordica, 370

Monarda, 300
Monilia, 230, 348
Moniliales, 230, 348
Monimiaceae, 301
Mon()l)lei)haridales, 335
Monoblopharis, 335
Monocotyledoneae, 204, 205, 357

-Epigynae, 300

-Hypogynae, 357
Monocotyledons, 205, 357
Monosaccharids, 145
Monospores, 200
Monostroma, 173
Monotropaceae, 321
Moraceae, 302
Morchella, 217, 342
Morels, 217
Moringaceae, 304
Moriola, 342
Moriolaceae, 342
Morning Glories, 320, 321, 306
Morphine, 150
Mortierella, 335
Mortierellaceae, 335
Morus, 302
Mosses, 248, 349
Mossworts, 242, 348
Mougeotia, 333
Movements, 116
Mucedinaceae, 348
Mucor, 180, 335
Mucoraceae, ISO, 335
Mucorales, 335
Musa, 301, 300
Musaceae, 300
Musci, 244, 349
Mushroom, 218, 229

Spawn, 229
Mustard, 303, 304
Mutations, 114
Mutinus, 345
Mutisia, 370
Mutisiaceae, 376
Mycelium, 180
Mycocalicium, 341
Mycoporaccae, 343
Mycosphaerellaceae, 343
Myoporaceae, 307
Myosotis, 300
Myosurus, 201. 301
Myricaccae, 372

398

INDEX

Myriothamnaccae, 3G9
Myriotrichiaceae, 337
Myristicaceae, 3G1
Myrsinaceae, 3G5
Myrtaceae, 3G9
Myrtales, 3G9
Myrtles, 3G9
Myrtus, 370
Myxobacteriaceae, 331
Myxophyceae, 1G3, 330
Myzodendraceae, 371

Naiadaceae, 358
Names of plants, 159
Narcissus, 3G0
Nastic movements, 128
Natural Selection, 113
Navicula, 334
Naviculaceae, 334
Naviculales, 334
Neckera, 351
Neckeraceae, 351
Nectar of flowers, 322
Nectria, 343
Nectrioidaceae, 347
Neluinbaceae, 361
Nelumbo, 361
Nemalion, 207, 338
Nemalionales, 338
Nemastomaceae, 338
Nematocaceae, 351
Nepenthaceae, 362
Nepeta, 367
Nephrodium, 353
Nereocystis, 201, 337
Nerium, 367
Netted-veined, 301
Nettles, 362

New Cells, formation of, 19
Nicotiana, 306, 366
Nicotine, 150
Nidularia, 345
Nidulariaceae, 345
Nidulariales, 228, 345
Nightshades, 366
Nigredo, 347
Nitella, 194, 336
Nitellaceae, 194, 336
Nitophyllum, 209, 339

Nitric acid, 139
Nolanaceae, 366
i^ostoc, 165, 331
^Nostocaceae, 165, 331
Nucleus, 1

Number of plants, 157
Numerical data, 327
Nutation, 123
Nutrition, 71
Nutritive tissues, 65
Nux vomica, 150
Nyctaginaceae, 365
Nymphaea, 364
Nymphaeaceae, 364
Nyssa, 372

Oak, 310

Oat Grasses, 359

Smut, 237
Ochnaceae, 363
Octaviana, 344
Odors of flowers, 322
Oedogoniaceae, 174, 333
,:yOedogonium, 174, 333
'Oedopodiaceae, 350
Oenothera, 309, 370
Oenotheraceae, 370
Oidium, 348
Oils, 14
Olacaceae, 371
Old Calamites, 264, 353

-fashioned Ferns, 257, 352

Pines, 278, 356
Olea, 366
Oleaceae, 366
Oleic acid, 143
Olein, 143
Oliniaceae, 371
Olives, 366
Olpidium, 332
Onion, 320
Onoclea, 259
Onygenaceae, 34
Oogones, 174
Oospora, 348
Opegrapha, 342
Open bundles, 59
Operculum, 252
Ophiogloss^kceae, 352

INDEX

399

Ophioglossales, 257, 352
Ophioglossuni, 352
Opiliaccae, 371
Opposite leaves, 292
Opuntia, 310, 370
Orchidaceae, 3G0
Orchidales, 299, 360
Orchids, 299, 3G0
Orchis, 299, 3G1
Orders, 159
Oreodoxa, 358
Organic Acids, 140
Origin of Phyla, 161

of Zygophyceae, 181
Orobanchaceae, 321, 307
Orthotrichaceae, 350
Orthotrichum, 350
Oryza, 359
Oryzeae, 359
Oscillatoria, 165, 330
Oscillatoriaceae, 165, 330
Osmosis, 72
Osmunda, 352
Osmundaceae, 352
Ostrich-fern, 259
Ostropaceae, 343
Ostrya, 372
Ovary, 286, 292
Ovulate, 275
Ovule, 273
Oxalic acid, 141
Oxalidaceae, 362
Oxalis, 326, 362
Oxidases, 153

Padina, 337
Palea, 297
Palct, 297
Palisade tissue, 292
Palmaceae, 358
Palmales, 296, 358
Palmatin, 143
Palmcllales, 171, 332
Palmettos, 300
Palmitic acid. 140, 143
Palms, 296, 358
Panax, 372
Pandanaceae, 357
:::4^andorina, 172, 332

Paniceae, 359

Panic Grasses, 359

Panicum, 359

Pannariaceae, 340

Pansy, 306

Papaver, 364

Papaveraceae, 364

Papaws, 361

Pappus, 312

J»arallel veined, 295
VJaraphyses, 203, 215
""l^arasitic habit, 320

Paratheliaceae, 343

Paratonic movements, 123

Parenchyma, 29

Parental care, 110

Parietal placentae, 303

Parkeriaceae, 352

Parmelia, 216, 340

Parmeliaceae, 340

Paronj^chia, 364

Parsleys, 372

Parsnip, 311

Parthenocissus, 371

Parthenogenesis, 324

Passage of Water, 73

Passiflora, 364

Passifioraceae, 363

Passion Flowers, 363

Pastinaca, 311, 372

Patellariaceae, 342

Path of the Water, 75

Pathology, 133

Pea, 305, 308

Peach, 314

Pear, 313

blight bacteria, 169

Peat-mosses, 251, 349

Pectase, 153

Pectose, 5

Pedaliaceae, 367
'^l5*ediastrum, 172

Pedicularis, 367

Peireskia, 370

Pelargonium, 306, 362

Pellia, 349

Peltigcra, 340

Pcltigcraceae, 340

Penaeaceae, 371

Pcnicillium, 222, 344

Penicillus, 195, 334

400

INDEX

renium, 333
Pentaphyllaccao, 371
Pentsteinon, 306
Peppermint oil, l-l-i
Pepsins, 153
Perianth, 274, 284
Peribleni, 44
Pericarp, 175, 208
Peridiuni, 228
Perisporiaoeae, 344
Perisporiales, 220, 343
Peristome, 252
Peritheeia, 215
Peronospora, 188, 335
Peronosporaceae, 187, 335
Pcronosporales, 335
Peroxidases, 153
Perseite, 142
Pertusaria, 340
Pertusariaceae, 340
Pestalozzia, 348
Petals, 286
Petticoat Mosses, 252
Petunia, 304, 366
Peziza, 216, 342
Pezizaceae, 342
Pezizales, 216, 341
Phacelia, 366
Phacidiaceae, 341
Phacidiales, 341
Phacidium, 341
Phaeophyceae, 199, 366
Phaeosporeae, 336
Phalarideae, 359
Phalaris, 359
Phallaceae, 345
Phallales, 228, 345
Phascum, 350
Phaseolus, 314, 369
Phellonic acid, 155
Philadelphus, 369
Philydraceae, 358
Phloem, 55
Phloeonic acid, 155
Phlox, 304, 366
Phoenix, 358
Phoradendron, 371
Phosphoric acid, 139
Photonasty, 124
Photosynthesis, 84
Phototaxy, 119

Phototropism, 124
Phragmidium, 235, 347
Phrymaceae, 367
Phycobarteriaccae, 331
Phycocyanin, 156, 163, 205
Phycoeryt.hrin, 156, 205
Phycomyceteae, 185, 335
Phycophaein, 156, 199
Phyla. 159, 327
Phylogeny, 114, 157
Phylogeny of Fungi, 240
Phyllachora, 343
Phyllactinia, 225
Phyllocladaceae, 356
Phyllocladus, 356
Phyllopsoraceae, 340
Phyllopyreniaceae, 343
Phyllosiphon, 334
Phyllosiphonaceae, 334
Phyllosticta, 239, 347
Physalis, 366
Physcia, 216, 341
Physciaceae, 341
Physcomitrium, 350
"Physiological Diseases," 134
Physiology, 71
Physma, 340
Phytolaccaceae, 364
Phytophthora, 188, 335
Picea, 281, 356
Pigments, 155
Pigweeds, 326
Pilacraceae, 346
Pilobolus, 335
Pilocarpaceae, 340
Pilotrichaceae, 351
Pilularia, 353
Pimenta, 370
Pinene, 144
Pines, 281, 356
Pinks, 303, 364
Pinoideae, 355
Pinus, 279, 281, 356
Piperaceae, 361
Piperin, 149

Piptocephalidaceae, 335
Piptocephalis, 335
Pirolaceae, 365
Pirus, 313, 368
Pistillaria, 346
Pistils, 284

INDEX

401

Pisuni, 305. 308, 309
Pithophora, 334
Pitted vessels, 36
Pittosporaccue, 369
Planera, 302
Plant Breeding, 115

Cell. 4
Plantaginaceae, 365
Plantago, 323, 365
Plantains. 365
Plasmolysis, 72
Plasmopara, 187, 335
Plasticity of Plant body, 319
Plastids, 2, 10
Platanaceae, 369
Platanthera, 361
Platanus, 369
Pleosporaceae, 343
Plerome, 44
Pleurocarpi, 252, 351
Pleuromoiaceae, 354
Pleurophascaceae, 351
Plocamiuni, 209, 339
Plowrightia, 219, 343
Plum, 308

Plumbaginaceae, 365
Plum-pocket Fungus, 218
Plums, 368
Plumule, 305
Poa, 300

Poaccae, 297, 359
Pocket Fungi, 341
Podaxaceae, 345
Podaxon, 345
Podocarpaceae, 356
Podocarpus, 356
Podosphaera, 225, 344
Podostemonaceae, 364
Pogonatuni, 351
Poisons, 96
Polar nuclei, 287
Polemoniaceae, 366
Polemonialos, 306
Polemonium, 366
Pollen, 273

-cells, 284

-sacs, 286

tube, 279, 287
Pollination, 280, 321
Polygalaceae, 363
Polygonaceae, 365

Polygonum. 305
PolypodiacM'ac. 258, 353
Polypodium, 258, 353
Polypody, 258
Polyporaceae, 230, 345
Polypores, 232, 345
Polyporus, 346
Polysaccharids, 147
-7**Jolysiphonia, 208, 339
Polystictus, 346
Polytrichaceae, 252, 351
Polytrichum, 351
Pond Scums, 178, 333
Pontederiaceae, 358
Poppies, 304
Populus, 304
Pore Fungi, 230
Porphyra, 207, 338
Portulaca, 364
Portulacaceae, 364
Postelsia, 201, 337
Potamogeton, 357
Potamogetonaceae, 357
Potato, 320
Potentilla, 291, 368
Pothos, 296, 300
Pottia, 350
Pottiaceae, 350
Powdery Mildews, 220
Prasiola, 332
Prasiolaceae, 332
Prickly Fungi, 230, 346

Pear, 310
Primary leaves, 281
Primrose, 303, 305
Primula, 303, 304, 323, 365
Primulaceae, 365
Primulales, 365
Prinodontaceae, 351
Promycelium, 234
Propagation, 171
Propolis, 341
Propyl, 142
Proteaceae, 372
Proteins, 87, 150
Proterandrous, 323
Proterogynous, 323
Prothallium. 254
Protocalamarinceae. 353
Protocaliciacoae, 341
Protococcaceae, 332

402

INDEX

Protococcoideao, 171, 332
Protococcus, 171, 332
Protomycetaceae, 344
Protonema, 247
Protopityeae, 354
Protoplasm, 1, 151
Protoplasmic movements, 110
Protosiphon, 192, 336
Prunaceae, 368
Prunus, 308, 368
Psalliota, 345
Pseuclomonas, 331
Pseudotsuga, 281
Psilotaceae, 354
Ptelea, 363
Pteridium, 259, 353
Pteridophyta, 254, 352
Pteridosperm, 272
Pteridospermalcs, 354
Pteridospermeae, 272, 354
Ptilota, 339
Ptychomniaceae, 351
Pucoinia, 232, 347
Puff-balls, 227, 345
Punicaceae, 309
Purslane, 320
Pycnia, 233
Pycnidia, 239
Pycniospores, 233
Pyrenidiaceae, 343
Pyrenoids, 11
Pyrenolichenes, 218, 342
Pyrenomycetales, 218, 343
Pyrenopsidaceae, 340
Pyrenothamniaceae, 343
Pyrenulaceae, 343
Pyronema, 217, 342
Pyronemataceae, 342
Pythiaceae, 335

Quercus, 310, 311, 372
Quiinaceae, 363
Quilhvorts, 258, 352
Quince, 313
Quinine, 150

Radial bundles, 56
Radish, 306
Radishes, 320

Raffinose, 146

Rafflesiaceae, 370

Ragweeds, 375

Ralfsiaceae, 337

Ramalina, 216, 340

Ramularia, 239, 348

Ranales, 361

Ranunculaceae, 361

Ranunculus, 274, 286, 361

Rapateaceae, 358

Raphanus, 306, 364

Raphe, 181

Raphids, 15

Ray flowers, 312

Razoumofskya, 371

Receptacles, 246

Receptacular cup, 286

Red Algae, 205, 338
-rust, 233
Seaweeds, 338
Snow plant, 172
-top Grasses, 359

Reductase, 153

Reduction Division, 111

Redwoods, 278

Regular flowers, 322

Rejuvenescence, 181

Relationship, 157

Reproduction, 109

Resedaceae, 364

Respiration, 90

Resting spore, 174

Restionaceae, 358

Reticulated veins, 257
vessels, 36

Rhabdonema, 334, 339

Rhacopilaceae, 351

Rhamnaceae, 371

Rhamnus, 371

Rhegmatodontaceae, 351

Rheum, 365

Rhipsalis, 370

Rhizina, 342

Rhizinaceae, 342

Rhiziphyllidaceae, 338

Rhizoids, 244

Rhizogoniaceae, 350

Rhizophoraceae, 370

Rhizopogon, 344

Rhizopus, 335

Rhodobacteria, 331

INDEX

403

Rhodochaotaceao, 338

Rhodochaetales, 338

Rhododendron, 365

Rhodonicla, 339

Rhodomclaccac, 330
/ilhodophyceae, 205, 338
'Rhodophyllidaocae, 339

Rhodophyllip, 339

Rhodynienia, 339

Rhodynioniacoae, 339

Rhodynieniales, 339

Rhoedales, 3G4

Rhus, 372

Rhytisnia, 341

Ribes, 309. 3G9

Riccia, 244, 348

Ricciaccae, 348

Ricciales, 348

Riccias, 348

Rice Grasses, 359

Rioinolcic acid, 143

Ricinus, 305, 363

Ringed vessels, 36

River- weeds, 357
^^ividaria, 331

Kivulariaceae, 165, 331

Rivularias, 165

Robinia, 369

Roccella, 342

Roccellaccae, 342

Rockweeds, 201, 337

Root (thickened), 320

Roots, 256

Rootstocks, 319

Rosa, 307, 368

Rosaceae, 368

Rosales, 368

Rose, 307, 368
-apples, 307

Ronnd Diatoms, 181, 333

Rubiaceae, 373

Rubiales, 373

Rul)us. 291

Riulbeckia, 315, 375

Ruderal plants, 320

Runners, 319

Rushes, 358

Russian Thistle, 325

Russula, 345

Rusts, 232, 347

Ruta, 363

Rutaceae, 363
Rutilariaceae, 334

Sabal, 300
Sabiaceae, 371
Saccharoniyces, 223, 344
Saccharomycetaceae, 344
Saccharose, 17, 146
Sac-Fungi, 213
Sachs's solution, 98
Sac-spores, 213
Sage, 304

Sagittaria, 291, 357
Salicaceae, 364
Salicin, 149
Salicylic acid, 141
Salix, 364
Salsola, 365
Salvadoraceae, 366
Salvia, 304, 305, 367
Salvinia, 259, 353
Salviniaceae, 353
Sambucus, 315, 373
Sand-bur, 325
Sanguinaria, 364
Sanicula, 372
Santalaceae, 371
Sapindaceae, 371
Sapindales, 371
Sapindus, 371
Saponin, 148
Sapotaceae, 366
Saprolcgnia, 186, 335
Saprolegniaceae, 186, 335
Saprolegniales, 335
Sap wood, 62
Sarcina, 331
Sarcoscypha, 224
Sargassaceae, 337
Sargasso Sea, 203
Sargassum, 202, 337
Sarraceniaceae, 362
Sarraceniales, 362
Saururaceae, 361
Saxifraga. 369
Saxifragaceae, 36
Saxifrages, 369
Scalariforni vessels, 36
Scale Mosses, 247, 349

404

INDEX

Scapania, 349
Scenedesmus, 172, 332
Scheuchzeriaceae, 357
Schistostegiaceae, 350
Schizaeaceae, 352
Schizogoniales, 332
Schulze's reagent, 35
Scirpus, 300, 358
Sclerenchyma, 32
Scleroderma, 345
Sclerodermataceae, 345
Scleroderniatales, 344
Scleroderris, 341
Sclerotinia, 342
Scotch Pine, 279
Scouring-Rush, 264
Scrophularia, 367
Scrophulariaceae, 367
Scrophulariales, 367
Scytonema,. 165, 331
Seytonemas, 165
Scytonemataceae, 165, 331
Scytopetalaceae, 362
Sea Ferns, 192, 336

Girdle, 201

Lettuces, 173

Mosses, 338

Palm, 201

Tree, 201

Umbrellas, 192
Secondary leaves, 281

thickening, 60
Secotium, 345
Secretory cells, 66
Sedges, 298, 358
Seed, 271

distribution, 324

-ferns, 272, 354

scale, 278, 279
Selaginella, 268, 354
Selaginellaceae, 267
Selaginellales, 354
Self fertilization, 323
Sematophyllaceae, 351
Senecio, 376
Senecionidaceae, 376
Sennas, 368
Sepals, 286
Septoria, 239, 347
Sequoia, 278, 356
Seta, 250

Sexual cells, 112

reproduction, 109, 170, 171
Shade plants, 320
Shield-Ferns, 259
Shoot, 329

Side Mosses, 252, 351
Sieve tissue, 38
Sigillaria, 269
Sigillariaceae, 354
Silene, 306, 364
Silicic acid, 140
Silks (of maize), 298
Silphium, 375
Simarubaceae, 363
Simblum, 345
Simple Algae, 170, 332

pistils, 286
Sinapis, 364
Siphonales, 334
Siphonophyceae, 184, 334
Sirobasidiaceae, 346
Sisyrinchium, 360
Size of Cells, 7
Skeletal tissue, 46
Slime Algae, 163, 330
Slit-Fungi, 218, 343

-Lichens, 218, 342
Smuts, 347
Snapdragon, 304, 367
Snowberry, 315
Snow-on-the-Mountain, 322
Soft Red Seaweeds, 339
Solanaceae, 366
Solanin, 148
Solanum, 366
Soleniaceae, 334
Solidago, 376
Solutes, 81
Solutions, 81
Somatic cells, 112

division, 112
Sonneratiaceae, 369
Sorbinose, 146
Sorbite, 142
Sordariaceae, 343
Soredia, 215
Sori, 232
Spadix, 300
Spanish needles, 325
Sparganiaceae, 357
Spathe, 296

INDEX

405

Spawn. 229

Special Adaptations, 319
Species, 114, 158
Spermatochnaceae, 337
SpermoRoncs, 215, 233
Sperms, 110, 174 .
Sphacelariaceae, 337
Sphac'olothcca, 347
Sphaerobolaceae, 345
Sphacrobolus, 345
Sphaerococcaceae, 339
Sphaeriaceae, 343
Sphaerioidaceae, 347
Sphaeroneniclla, 347
Sphaerophoraceae, 341
Sphaerophorus, 341
Sphacroplea, 334
Sphaeropleaceae, 334
Sphaeropsidales, 238, 347
Sphaeropsis, 347
Sphaerotheca, 225
Sphagnaceae, 349
Sphagnales. 251, 349
Sphagnum, 250, 349
Sphenophyllaceae, 353
Sphenophyllales, 353
Sphenophyllincae, 262, 353
Sphenophyllum, 262
Spiderworts, 358
Spikelet, 297
Spiraea, 307, 368
Spiral vessels, 36
Spiranthes, 361
Spiridentaceae, 351
Spirochaete, 331
jSpirodela, 358
^tepirogyra, 178, 333
bpirogyraceac, 333
Spirulina, 165
Splachnaceae, 350
Splachnidiaceae, 337
Splachnum, 252, 350
Spleenworts, 259
Sponge tissue, 292
Spontaneous Generation, 166
Sporangium, 190
Spore-case, 250

-fruit, 100. 175, 213

mother-cells. 243

-prints, 231
Sporids. 233

Sporocarp, 175. 213
Sporochnaceae. 337
Sporodinia. 197
Sporogenous tissues. 211
Sporophyll. 261
Sporophyte. 110. 242
Spot Fungi. 238, 347
Spruces, 281
Squamariaceac. 338
Squash, 305
Stachyuraceae, 364
Stackhousiaceae, 371
Stalked Puff-balls, 231
Stamens, 284
Staminate, 275
Stapelia, 322, 367
Staphyleaceae, 371
Starch, 13, 85, 147
Star Flowers, 370
Statocysts, 127
Statoliths, 126
Stearic acid. 143
Stearin. 143
Stem, 255
Stemonaceae, 358
Sterculiaceae. 362
Stereocaulon. 340
Stereum. 230. 346
Sterigmata, 222
Sterigmatocystis, 348
Sterile tissues, 211
Stickseed, 325
Sticta, 340
Stictaceae, 340
Stictidaceae, 341
Stictis. 341
Stigma, 286. 292
Stigmonose, 134
Stigonema. 165. 331
Stigonemataceae, 165, 331
Stilbaceae, 348
Stilophoraceac. 337
Stink-horns. 228. 345
Stinking Smut, 237
Stipules, 292
Stomata. 51
Stone cells. 32
Stoneworts. 193, 336
Storage tissues. 66
Store of food. 319
Strawberry, 289, 306, 319. 326

406

INDEX

Strcbloncma, 337

Strelitzia, 360

Streptococcus, 331

Striariaccae, 337

Strigiilaceae, 343

8trobilophyta, 277, 355

Strobilus, 273

Struvoa, 336

iStryohnino, 150

Stuartia, 363

Style, 292

Stylidiaceae, 373

Styracaceae, 366

Stysaniis, 348

Sub-classes, 160
-families, 160
-orders, 160

Suberin, 155

Succinic acid, 141

Sugar, 145

Sugars, 17

Sulphur-bacteria, 169

Sulphuric Acid, 139

Sumachs, 372

Summary of Anthophyta, 315

Sunflower, 311

Sunflowers, 375

Sun plants, 320

Super-orders, 160, 361, 365, 366,

368, 373
Supply of energy, 91
Supporting System, 64
Surirellaceae, 334
Survival of the fittest, 113
Susceptibility to diseases, 137
Sweet Pea, 314
Symbiosis, 216
Symphoricarpos, 315
Symplocaceae, 366
Symplocarpus, 358
Synapsis, 111
Syncephalis, 335
Synchytriaceae, 172, 332
Synchytrium, 332
Synergids, 287
Syringa, 366

Tabellariaceae, 334
Taccaceae, 360
Tamaricaceae, 364

Tanacetone, 144
Tannin. 141
Tansy oil, 144
Taphrina, 341
Taraxacum, 312, 377
Tassel, 300
Taxaceae, 357
Taxales, 282, 356
Taxin, 150

Taxodiaceae, 278, 356
Taxodium, 278, 356
Taxodiums, 278, 356
Taxus, 282, 357
Tecoma, 367
Tectona, 367

Teliosporeae, 213, 232, 346
Teliospores, 232
Temperature, 95
Terfezia, 344
Terfeziacoae, 344
Tetrasaccharids, 146
Tetraspora, 332
Tetraspores, 206
Thea, 363
Theaceae, 363
Theine, 149
Thelephora, 346
Thelcphoraceae, 230, 346
Thelidium, 342
Thelocarpon, 340
Theloschistaceae, 340
Theloschistes, 216, 340
Thelotremataceae, 340
Theobromine, 149
Theophrastaceae, 365
Thigmotropism, 127
Thiobacteria, 331
Thistle, 324, 376
Tlioreaceae, 338
Thorns, 319
Thread Lichen, 216
Thuidium, 351
Thurniaceac, 358
Thuya, 356
Thuyas, 282, 356
Thuyopsidacoae, 282, 356
Thymclaeaceae, 371
Thymus, 367
Tilia, 362
Tiliacoao, 362
Tillandsia, 360

INDEX

407

Till(>tia, 237, 347
Tillotiaccae, 237, 347
Tilopteridacoae, 337
Tilopteridalcs, 337
Tininiia, 350
Tininiiaceao, 252, 350
Tissues, 28

Tissue systems, 43, 46
Toadstools, 229, 345
Tolypella, 330
Tolypothrix, 105
Top Mosses, 252, 349
Torreya, 357
Torula, 348
Torus, 292

Touch-me-not, 325, 326, 363
Tovariaceae, 364
Toxylon, 362
Tracheae, 36
Tracheary tissue, 35
Tracheids, 36
Tradescantia, 358
Transpiration, 76
Tree Ferns, 258, 352
Mosses, 252, 351
Trehalose, 146
Tremandracoae, 363
Tremella, 340
Treniellaceae, 346
Tremellales, 231, 346
Trentepohlia, 333
Trentepohliaceae, 333
Trichocomataceae, 344
Trichogyne, 174
Trichomanes, 352
Trichosphaeria, 343
Trifolium, 369
Trinoniaceae, 363
Trillium, 300
Tri-methylamine, 153
Trisaccharids, 140
Triticeae, 359
Triticum, 300, 359
Triuridaceae, 357
Trochiscia, 332
Trochodcndraceae, 361
Tropaeolaceae, 363
Tropaeolum, 363
Tropisms, 124
True Mosses, 251, 349
Truffles, 223

Tryblidiaccae, 341
Tryblidium, 341
Trypetheliacoae, 343
Trypsines, 153
Tube Algae, 184. 334

Fungi, 186, 335
Tubcraceae, 344
Tuberales, 223, 344
Tuber, 344

Tuberculariaceae, 348
Tuberculina, 348
Tuberculosis bacteria, 169
Tubers, 320, 344
Tulasnellaceae, 346
Tulipa, 358
Tumble weeds, 325
Tumboa, 275, 355
Tumboaceae, 355
Turf Mosses, 252, 349
Turgor, 73

movements, 120
Turneraceae, 363
Turnips, 320
Turpentine, 144

canals, 283
Tylophoron, 341
Tylostoma, 231, 345
Tylostomataceae, 345
Typha, 357
Typhaceae, 357
Typhoid bacteria, 169
Typical flower, 285

Ulmaceae, 362
Ulmus, 362
OLJlothrix, 173, 332
Ulotrichaceae, 332
Ulva, 173, 332
Ulvaceae, 332
Ulvales, 332
Umbellales, 372
l^mbilicaria, 342
Uncinula, 225, 344
Union of cells, 24
l^redinaceae, 347
Uredinales, 232, 347
Urediniospores, 233
Uredo. 234, 347

408

INDEX

Uredospores, 233
Uromyces, 235, 347
Uropyxis, 347
Urtica, 362
Urticaceac, 362
Usnea, 216, 224, 340
Usneaceae, 340
Ustilaginaceae, 347
Ustilaginales, 235, 347
Ustilago, 237, 347

Violet, 302, 363
Viscum, 371
Vitaceae, 371
Vitcx, 367
Vitis, 371
Vochysiaccac, 363
Volvocaceae, 332
Volvoces, 172
-^Volvox, 172, 332

Vaccinium, 365
Vacuoles, 17
Valerianaceac, 373
Valonia, 192, 336
Valoniaceae, 336
Valoniales, 336
Valsa, 343
Valsaeeae, 343
Valve, 180
Vanilla, 361
Vanillin, 154
Variations, 112
Vascular Bundles, 55
^aucheria, 185, 334
vaucheriaceae, 334
Vaucherioideae, 185, 334
Vegetable Kingdom, 159
Veins, 257

of leaves, 60
Velloziaceae, 360
Venter, 243
Veratrine, 150
Verbascum, 367
Verbena, 367
Verbenaceae, 367
Vernonia, 376
Vernoniaceae, 376
Veronica, 367
Verpa, 342
Verrucaria, 342
Vcrrucariaceae, 342
Vetches, 326
Viburnum, 373
Vicia, 369
Victoria, 364
Vinca, 367
Viola, 302, 303, 363
Violaceae, 363

Walking-fern, 259
Walnut, 310, 372
Water, 71, 139

Cultures, 97

Ferns, 259, 353

Flannel, 185

-lilies, 364

Molds, 186, 335

Net, 172

Plantain, 289, 357

pores, 77
Weberaceae, 351

Wedge-leaved Calamites, 262, 353
Wcisia, 350
Welv.itschia, 275, 355
Wheat Grasses, 359

rust, 232

Smut, 237
White Pines, 282

Rusts, 187, 335
Whorled leaves, 292
Wild Geranium, 302, 326
Willows, 364
Wings, 308
Winteranaceae, 362
Wood-fibers, 33
Wood Mosses, 252, 350

Xanthium, 375
Xanthophyll, 11, 155
Xanthoxylum, 363
Xerophytes, 320
Xylaria, 343
Xylariaceae, 343
Xylem, 55
Xyridaceae, 358

INDEX

409

Yeast-Fungi, 344

Plants, 222
Yellow Pines, 282
Yews, 282, 357
Yucca, 300, 358

Zamia, 274, 355
Zaniiaccae, 355
Zannichoilia, 357
Zea, 300. 360
Zingibcraceae, 360

Zinnia, 375 '
Zonaria, 337
Zoospores, 171
Zostera, 357
Zygnema, 182, 333
Zygnemataceae, 333
Zygnema tales, 333
Zygogonium, 333
Zygomorphic, 322
Zygoniorphy, 309
Zygophyceae, 177, 33i
Zygophyllaceao, 363
Zygospore, 190
Zygote, 109, 171
Zymase, 153