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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
BY
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
1
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-