LESSONS IN BOTANY
BY
GEORGE FRANCIS ATKINSON, Pn.B.
Professor of Botanv in Cornell University
NEW YORK
HENRY HOLT AND COMPANY
1900
Copyright, 1900,
BY
HENRY HOLT & CO.
ROBERT DRUMMOND, PRINTER, NEW YORK.
PREFACE.
THIS abbreviated and simplified edition of my Elementary
Botany has been prepared for the use of pupils in the secondary
schools, where short, or half-year, courses in botany are given,
and where, for one reason or another, my larger book cannot
be adapted to such abbreviated courses. A large part of the
matter has been rewritten, only the less technical descriptive
portions being retained.
The subject-matter is arranged for three different uses : exer-
cises for the pupils, demonstrations by the teacher, and descrip-
tive matter for reading and reference. To clearly set apart, for
the convenience of the teacher and pupil, the work suggested
for each, all the work outlined for the teacher is placed under
the head of demonstration, whether the setting up of apparatus or
an actual demonstration before the class ; so also all the prac-
tical work of the pupils, whether an experiment or an ordinary
exercise, is put under the head of exercise. The demonstrations
and the exercises each have their own consecutive numbering,
so that the teacher can tell at a glance the subdivisions of the
work. Where there are a sufficient number of microscopes, so
that one can be allotted to two or three pupils, many of the
demonstrations can be used as exercises, at the discretion of the
teacher. All the paragraphs, whether descriptive, demonstration
or exercise, have a separate and consecutive numbering.
The first chapter in this abbreviated book is devoted to a
study of how seedlings grow from the seed, and this is followed
by a chapter on shoots, buds, etc., in order to give an oppor-
tunity for some out-door work if the season is propitious, or for
IV PREFACE.
the study of material easily collected. This emphasizes the de-
sirability of supplementing the regular laboratory course with
the out-door work, or with observations on material suitable to be
employed in out-door work when conditions permit. The third
chapter then treats of protoplasm (the living substance) in the
root hairs of seedlings, followed by a similar study in spirogyra.
In the following chapters much the same order is used as in the
larger book, but there has been an attempt to simplify the
treatment. Very much of the technical matter in the larger
book has been omitted here, and in consequence much of the
matter which is useful for reference to those who desire supple-
mentary reading and explanations. For this matter the larger
Elementary Botany should be consulted.
The studies indicated in the part on ecology are not intended
to be pursued as a distinct and separate piece of work, but they
may be made the basis of excursions during the progress of the
work on physiology and morphology. It is possible to indicate
definitely where some of these out-door studies are applicable.
At the same time the retention of the third part as a distinct
subdivision of the book serves to emphasize the importance of
ecological study, or perhaps rather of the study of plant life on
a larger scale, and some of the interesting problems connected
with the environmental influences on plant life and plant com-
munities. It should be recognized that plant distribution, as
well as many of the other important problems connected with
ecological study, cannot be carried on in the secondary schools
with the rigid system applicable in the college or university, or
even with the precision which the student of ecology would
desire, since a considerable previous technical knowledge of
plants would be necessary. The chief importance of the study
in the secondary schools is, I believe, to get the pupil interested
in observing living plants, and in gaining a general impression
of the fundamental laws, and in leading the pupil to realize, in a
measure, the great influence which environment has on living
beings.
PREFA CE. V
It is suggested that the teacher, at the beginning of the work,
take some account of the time to be allotted to the different
subjects of the course. For example, in a 2o-\veeks' course,
7 to 8 weeks could be devoted to physiology, 5 or 6 weeks
could be devoted to general morphology ; while 6 or 8 weeks
could be devoted to the study of plant families. As the work
progresses it can be easily seen whether or not all the exercises
and demonstrations can be gotten in during the allotted time.
If the time is too short in some cases, the teacher can then
arrange to omit certain of the exercises in each chapter, so that
as a whole the work can be completed in the desired time.
Some of the chapters are intended for reading and reference
only. These are indicated at the beginning of the chapters in
question. They should not be taken into account when consid-
ering the amount of practical work to be done by the pupil.
CORNELL UNIVERSITY,
January, 1900.
MATERIAL FOR LABORATORY ILLUSTRATION.
HIGH SCHOOL BOTANICAL SET.
Special net price, $20. Express extra.
PERMANENT MOUNTS.
Those on cards are protected with fly-leaf and placed together in
a neat portfolio.
Pond scum (Spirogyra) on card $ .20
Green felt (Vaucheria) on card 20
Wheat rust (Puccinia), three stages, on card 30
Carnation rust (Uromyces) on card 20
Dodder (Cuscuta) on card 20
Mildew (Uncinula) on card 20
Lichen thallus on card 20
Liverwort (Marchantia) thallus with gemmae and sexual organs on
card :••".• -35
Liverwort — mature fruit (Sporogonia) carefully preserved in fluid
for exhibition 75
Moss (Polytrichum) — male, female, and fruiting plant on card 35
Fern (Polypodium) — whole plant on card 10
Horsetail (Equisetum) — fertile and sterile plants on card 35
Quillwort (Isoetes) — whole plant on card 30
Quillwort (Isoetes) — plant in section preserved in fluid 45
Pine — male and female flowers and mature scale with seed on card .35
Trillium — mature plant on card 20
Tooth wort (Dentaria) — plant on card 20
MICROSCOPIC PREPARATIONS.
Corn — cross- section of stem showing bundles 40
Corn — longitudinal section of stem showing bundles 40
Sunflower — cross-section of stem showing bundles 40
Sunflower — longitudinal section of stem showing bundles 40
Caladium — cross-section of leaf stalk showing bundles 40
Celery — cross -section of leaf stalk showing bundles 40
Celery — longitudinal section of leaf stalk showing bundles 40
Ivy — cross-section of leaf 40
Begonia — cross-section of leaf 40
Pond scum (Spirogyra) in fruit 40
Green felt (Vaucheria) in fruit 50
Green felt (Vaucheria) — sexual organs 50
Black mould (Rhizopus) — rhizoids, sporangia, and columella .... .50
Willow mildew (Uncinula) — perithecia crushed and stained to show
asci and spores 50
Carnation rust — sections showing haustoria 40
Dodder ^Cuscuta) — sections showing haustoria 40
Wheat rust (Puccinia) — sections of cluster cup 50
Wheat rust (Puccinia) — sections of red rust 50
WTheat rust i Puccinia) — spores of black rust 40
$14.60
vi
MATERIAL FOR LABORATORY ILLUSTRAI^ION, vii
Brought forward $14.60
Lichen (Peltigera) — section of thallus .40
Liverwort (Marchantia) — section of antheridia .75
Liverwort (Marchantia) — section of archegonia 75
Liverwort (Marchantia) — spores and elaters 40
Moss (Mnium) — section of antheridia . .75
Moss (Mnium) — section of archegonia 75
Moss capsule showing teeth (peristome) and spores 50
Fern (Polypodium) — cross-section of stem 40
Fern (Polypodium) — longitudinal section of stem 40
Fern (Pteris) — cross-section of stem 40
Fern (Pteris) — longitudinal section of stem 40
Fern — sporangia and spores 40
Fern — germinating spores 50
Fern — prothallium with sexual organs 75
Fern — prothallium with attached embryo 75
Horsetail (Equisetum) — spores and elaters 40
Quillwort (Isoetes) — section of microsporangia 75
Quillwort (Isoetes) — section of macrosporangia 75
Pine— mature pollen 40
Pine — fruiting scale at time of pollination 40
Pine — prothallium with archegonia, and pollen tube in nucellus. . .75
Trillium — pollen 40
Trillium — section of anther 40
Trillium — section of pistil showing locules and ovules . co
Lilium — embryo-sac in section 75
Dentaria — section of pistil showing locules and ovules 50
$27.50
or the entire set for $20.00.
DUPLICATE MATERIAL FREE WITH SET.
Pond scum (Spirogyra) in fruit.
Green felt (Vaucheria) in fruit.
Wheat rust — two stages on wheat and a cluster cup to represent the stage
on barberry.
Powdery mildew.
Liverwort (Conocephalus).
Moss ( Poly trichum) — male, female, and fruiting plant.
Fern (Polypodium) — pressed plants, and sporangia in formalin.
Horsetail (Equisetum) — sterile and fertile plants.
Quillwort (Isoetes) — plants in formalin.
Pine — mature male and young female cones in formalin.
These prepared slides, and other material, for laboratory work, can
be obtained of the Ithaca Botanical Supply Co., Ithaca, N. Y. They
are especially adapted to illustrate LESSONS IN BOTANY, as well as the
author's larger ''Elementary Botany."
A supplementary list of supplies representing additional topics treated
of in " Elementary Botany," can be had on application to the Ithaca
Botanical Supply Co.
TABLE OF CONTENTS.
PART I: PHYSIOLOGY.
PAGE!
CHAPTER I.
HOW THE SEEDLING GROWS FROM THE SEED .............. . 1-6
CHAPTER II.
WINTER BUDS, SHOOTS, ETC .................................. 7-14
CHAPTER III.
THE LIVING SUBSTANCE OF PLANTS .......................... I5~l8
I. Protoplasm in root hairs of seedlings.
CHAPTER IV.
THE LIVING SUBSTANCE OF PLANTS, CONTINUED ............... !9~23
II. Protoplasm in an alga: Spirogyra.
CHAPTER V.
THE LIVING SUBSTANCE OF PLANTS, CONCLUDED ............... 24-27
III. Protoplasm in a fungus: Mucor.
CHAPTER VI.
HOW WATER MOVES IN AND OUT OF PLANT CELLS ....... .... 28-33
Absorption, diffusion, osmose.
ix
X TABLE OF CONTENTS.
CHAPTER VII.
PAGES
HOW PLANTS OBTAIN THEIR LIQUID FOOD 34~44
I . Water cultures ." 34~3^
II. How plants obtain food from the soil 36-41
III. Strong solutions of plant food are injurious 4!-44
CHAPTER VIII.
HOW SOME PLANT PARTS REMAIN RIGID 45~49
CHAPTER IX.
HOW WATER MOVES THROUGH THE PLANT 5°-55
I. Root pressure or osmotic pressure So-51
II. The loss of water by plants (transpiration) 5I~55
CHAPTER X.
HOW WATER MOVES THROUGH THE PLANT, CONCLUDED 56-60
III. Part which the leaf plays in transpiration.
CHAPTER XI.
PATH OF MOVEMENT OF LIQUIDS IN PLANTS 61-69
CHAPTER XII.
HOW PLANTS GET THEIR CARBON FOOD 7°~73
I. The gases concerned.
CHAPTER XIII.
HOW PLANTS GET THEIR CARBON FOOD, CONCLUDED 74-80
II. Starch formed by green plants.
CHAPTER XIV.
ROUGH ANALYSIS OF PLANT SUBSTANCE 81-83
TABLE OF CONTENTS. XI
.CHAPTER XV.
PAGES
SOME OTHER WAYS IN WHICH CERTAIN PLANTS OBTAIN FOOD... 84-93
CHAPTER XVI.
RESPIRATION 94-101
CHAPTER XVII.
GROWTH 102-106
CHAPTER XVIII.
MOVEMENT IN PLANTS DUE TO IRRITABILITY 107-114
PART II: MORPHOLOGY AND LIFE HISTORY
I OF REPRESENTATIVE PLANTS.
CHAPTER XIX.
SPIROGYRA 115-119
CHAPTER XX.
THE GREEN FELT: VAUCHERIA 120-124
CHAPTER XXI.
FUNGI: THE BLACK MOULD 1-5-128
CHAPTER XXII.
FUNGI, CONTINUED : WHEAT RUST (PucciNiA GRAMINIS) 129-133
CHAPTER XXIII.
FUNGI, CONCLUDED : THE WILLOW MILDEW (UNCINULA SALICIS). 134-138
XI 1 TABLE OF CONTENTS.
CHAPTER XXIV.
PAGES
LIVERWORTS : HEPATIC^: (MARCHANTIA POLYMORPHA) 139-148
CHAPTER XXV.
MOSSES : Musci (POLYTRICHUM OR MNIUM) 149-154
CHAPTER XXVI.
FERNS: FILICINE^E (THE POLYPODY OR CHRISTMAS FERN) 155-165
CHAPTER XXVII.
FERNS, CONCLUDED: THE SEXUAL STAGE OF FERNS 166-173
CHAPTER XXVIII.
HORSETAILS : EQUISETINE^ (THE FIELD EQUISETUM) 174-179
CHAPTER XXIX.
QUILLWORTS: ISOETES 180-183
CHAPTER XXX.
GYMNOSPERMS : THE WHITE PINE 184-193
CHAPTER XXXI.
MORPHOLOGY OF THE ANGIOSPERMS : TRILLIUM ; DENTARIA 194-202
«
CHAPTER XXXII.
PROTHALLIUM AND SEXUAL ORGANS OF FLOWERING PLANTS 203-207
CHAPTER XXXIII.
SEEDS AND SEEDLINGS.. . 208 216
TABLE OF CONTENTS. Xlll
CHAPTER XXXIV.
PAGES .
THE PLANT BODY AND SOME OF ITS MODIFICATIONS 2IJ-22Q
CHAPTER XXXV.
ARRANGEMENTS OF THE PARTS OF THE FLOWER 221-224
CHAPTER XXXVI.
RELATIONSHIPS SHOWN BY FLOWER AND FRUIT 225-230
CHAPTER XXXVII.
CLASSIFICATION (OR TAXONOMY) 231-235
STUDIES ON PLANT FAMILIES.
MONOCOTYLEDONES 236-249
CHAPTER XXXVIII.
TOPIC I : MONOCOTYLEDONES WITH CONSPICUOUS PETALS (PETA-
LOIDE/E) 236-242
Order Liliflbrge : Family Liliaceae; the lily family.
Order Gynandrse : Family Orchidaceae ; the orchid family.
CHAPTER XXXIX.
TOPIC II : MONOCOTYLEDONES WITH FLOWERS ON A SPADIX (SPA-
DICIFLOR^) . . .'. 243-246
Family Araceae ; the arum family.
CHAPTER XL.
TOPIC III : MONOCOTYLEDONES WITH A GLUME SUBTENDING THE
FLOWER (GLUMIFLOR^:) 247-249
Family Gramineae ; the grass family.
XIV TABLE OF CONTENTS.
PAGES
DICOTYLEDONES 250-283
CHAPTER XLI.
TOPIC IV : DICOTYLEDONES WITH DISTINCT PETALS, FLOWERS IN
CATKINS OR AMENTS ; OFTEN DEGENERATE 250-254
Order Amentiferae : Family Salicaceae ; the willow family.
Family Cupuliferae ; the oak family.
CHAPTER XLII.
TOPIC V : DICOTYLEDONES WITH DISTINCT PETALS AND HYPOGY-
NODS FLOWERS 255-261
Order Urticiflorae : Family Ulmacese ; the elm family .
Order Polycarpicse : Family Ranunculacese ; the crowfoot
family.
Order Rhoeadinae : Family Cruciferae ; the mustard family.
Order Cistiflorae : Family Violaceae ; the violet family.
CHAPTER XLIII.
TOPIC VI : DICOTYLEDONES WITH DISTINCT PETALS AND PERIGY-
NOUS OR EPIGYNOUS FLOWERS . 262-264
Order ^Esculinae : Family Aceraceae ; the maple family.
CHAPTER XLIV.
TOPIC VI, CONTINUED 265-270
Order Rosiflorae : Family Rosaceae ; the rose family.
Family Amygdalaceae ; the almond family.
Family Pomaceae ; the apple family.
Order Leguminosae : Family Papilionaceae ; the pea family.
TOPIC VII : DICOTYLEDONES WITH DISTINCT PETALS AND EPIGY-
NOUS FLOWERS. 271-273
Order Myrtiflorae : Family Onograceae ; the evening-primrose
family.
SYMPETAL/E. 274-282
CHAPTER XLV.
TOPIC VIII : DICOTYLEDONES WITH UNITED PETALS, FLOWER
PARTS IN FIVE WHORLS 274
Order Bicornes : Family Vacciniaceae ; the whortleberry
family.
TABLE OF CONTENTS. XV
PAGES
TOPIC IX : DlCOTYLEDONES WITH UNITED PETALS, FLOWER PARTS
IX FOUR WHORLS 275~277
Order Tubiflorte : Family Labiatse ; the mint family.
Order Personatse : Family Scrophulariacese; the figwort family.
CHAPTER XLVI.
TOPIC IX, CONTINUED 2 78-282
Order Aggregate : Family Composite ; the composite family.
PART III: ECOLOGY.
INTRODUCTION 283-291
Suggestions for ecological study.
CHAPTER XLVII.
SEED DISTRIBUTION 292-299
CHAPTER XLVIII.
STRUGGLE FOR OCCUPATION OF LAND 300-305
CHAPTER XLIX.
ZONAL DISTRIBUTION OF PLANTS 306-310
CHAPTER L.
SOIL FORMATION IN ROCKY REGIONS AND IN MOORS 311-327
CHAPTER LI.
PLANT COMMUNITIES ; SEASONAL CHANGES 328-336
CHAPTER LII.
ADAPTATION OF PLANTS TO CLIMATE 337-34 J
APPENDIX 343-353
GLOSSARY 355-360
f| BOTANY.
PART I. PHYSIOLOGY.
CHAPTER I.
HOW THE SEEDLING GROWS FROM THE SEED.
1. Since the seedling plant is useful in illustrating several of
the life processes of plants we may well begin with some studies
of germinating seeds. We may take for the first example the
pumpkin seedling, and then follow with several others in order
to become familiar with the parts of the seedling plant before
,re, study the life processes.
THE PUMPKIN SEEDLING.
Demonstration I.
2. To prepare seeds for germination. — Soak(a handful of seeds (or more if
the class is large) in water for twelve to twenty -four hours. Take shallow
crockery plates, or ordinary plates, or a germinator with a fluted bottom.
Place in the bottom some sheets of paper, and if sphagnum moss is at
hand scatter some over the paper. If the moss is not at hand, throw the
upper layer of paper into numerous folds. Thoroughly wet the paper and
rr oss, but do not have an excess of water. Scatter the seeds among the
moss or the folds of the paper. Cover with some more wet paper and
. in a room where the temperature is about 20° C. to 25° C. The ger-
minator should be looked after to see that the paper does not become dry.
5 may be necessary to cover it with another vessel to prevent the too rapid
evaporation of the water. The germinator should be started about a week
before the seedlings are wanted fer study. Some of the soaked seeds should
be planted in soil in pots and kept at the same temperature, for comparison
with those grown in the germinator.
2 BOTANY.
3. Structure of the pumpkin seed. — The pumpkin seed has
a tough papery outer covering for the protection of the embryo
plant within. This covering is made up of the seed coats.
When the seed is opened by slitting off these coats there is seen
within the "meat" of the pumpkin seed. This is nothing
more than the embryo plant. The larger part of this embryo
consists of two flattened bodies which are more prominent than
any other part of the plantlet at this time. These two flattened
bodies are the two first leaves, usually called cotyledons. If we
spread these cotyledons apart we see that they are connected at
one end. Lying between them at this point of attachment is a
small bud. This is the plumule. The plumule consists of the
very young leaves at the end of the stem which will grow as the
seed germinates. At the other end where the cotyledons are
joined is a small projection, the young root, often termed the
radicle.
4. How the embryo gets out of a pumpkin seed. — To see
how the embryo gets out of the pumpkin seed we should
examine seeds germinated in the folds of damp paper or on damp
sphagnum, as well as some which have been germinated in earth.
Seeds should be selected which represent several different stages
of germination.
Fig. i.
Germinating seed of pumpkin, showing how the heel or " peg " catches on the seed coat
to cast it off.
5. The peg helps to pull the seed coats apart. — The root
pushes its way out from between the stout seed coats at the
smaller end, and then turns downward unless prevented from so
HOW 'THE SEEDLING GROWS FROM THE SEED. 3
doing by a hard surface. After the root is 2-^cm long, and the
two halves of the seed coats have begun to be pried apart, if we
look in this rift at the
junction of the root
and stem, we shall see
that one end of the seed
coat is caught against
a heel, or "peg,"
which has grown out
from the stem for this
purpose. Now if we
examine one which is
a little
more ad-
vanced,
we shall see this heel
more distinctly, and
also that the stem is
arching out away from
the seed coats. As the
stem arches up its back
in this way it pries with
the cotyledons against
*• the upper seed coat,
Escape of the pumpkin seedling from the seed coats. •, , ,1 i cpprl mat
is caught against this heel, and the two are pulled gradually
apart. In this way the embryo plant pulls itself out from be-
tween the seed coats. In the case of seeds which are planted
deeply in the soil we do not see this contrivance unless we dig
down into the earth. The stem of the seedling arches through
the soil, pulling the cotyledons up at one end. Then it
straightens up, the green cotyledons part, and open out their
inner faces to the sunlight, as shown in fig. 3. If we dig into
the soil we shall see that this same heel is formed on the stem,
and that the seed coats are cast off into the soil.
4 BOTANY.
6, Parts of the pumpkin seedling. — During the germination
of the seed all parts of the embryo have enlarged. This in-
crease in size of a plant is one of the peculiarities of growth.
The cotyledons have elongated and expanded somewhat, though
not to such a great extent as the root and the stem. The
cotyledons also have become green on exposure to the light.
Very soon alter the main root has emerged from the seed coats,
other lateral roots begin to form, so that the
root soon becomes very much branched.
The main root with its branches makes
up the root system of the seedling. Be-
tween the expanded cotyledons is seen
the plumule. This has enlarged some-
what, but not nearly so much as the root,
or the part of the stem which extends
below the cotyledons. This part of the
stem, i.e., that
part below the
cotyledons and
extending to the
beginning of the
root, is called in
all seedlings the
Fig. 3.
Pumpkin seedling rising from the ground.
hypocotyl, which means ' ' below the cotyledon.
Exercise 1 .
7. Structure of a squash or pumpkin seed. — Sketch a squash or pumpkin
seed, noting carefully the form and markings. Split off the tough papery
seed coats (testa], from a seed which has been soaked in water, to observe
the embryo. Note the large, flattened cotyledons. Spread them gently apart
to see the attachment at the smaller ends, where they are attached to the
short caulicle (stem). Sketch the embryo in this position showing the
cotyledons, the plumule between them, and the short radicle projecting from
the end where the cotyledons are attached; name the parts of the embryo.
Make a cross-section of another seed through the middle, and observe the
relati3n of the cotyledons to the seed coats; sketch. Make a cross-section
HOW THE SEEDLING GROWS FROM THE SEED. 5
of a seed near the smaller end so that the section will cut across the
plumule; sketch showing the positions of the different parts and the relation
to the seed coats.
Exercise 2.
8. Structure of the bean seed. — Take beans which have been soaked in
water. Sketch a bean, showing the form, the scar (hilutn) on the concave
side, the minute pit (niicropyle) by the side of the hilum. Remove the
testa (seed coats) from one of the beans; note the large thick cotyledons; de-
termine where the cotyledons are joined (or attached to the young caulicle).
Along one side of this point of attachment note the young radicle; at the
other end between the cotyledons note the plumule.
Split open a bean along the line where the cotyledons meet ; sketch one
half, showing the young plumule and the venation of the leaf, and at
the other side the young radicle. Make a cross-section of a bean and
sketch to show the relation of the cotyledons to the seed coats, and the
plumule between the cotyledons.
If there is time, compare a pea seed.
Exercise 3.
9. Structure of the grain of corn. — Take grains of corn that have been
soaked. Note the form, and the difference of the two sides. Sketch a
grain of corn showing the depressed area near the smaller end.
Make a longisection of a grain of corn through the middle line. (If neces-
sary make several to obtain one which shows the structures well near the
smaller end of the grain.) Sketch the section as shown by one half, observ-
ing the following structures : ist, the hard outer " wall " (formed of the con-
solidated wall of the ovary with the integuments of the ovules — see
Chapters 32 and 33) ; 2d, the greater mass of starch and other plant food
(the endosperm) in the centre ; 3d, a somewhat crescent-shaped body (the
scutellum) lying next the endosperm and near the smaller end of the
grain ; 4th, the remaining portion of the young embryo lying between
the scutellum and the seed coat in the depression. When good sections
are made one can make out the radicle at the smaller end of the seed,
and a few successive leaves (the plumule) which lie at the opposite end of
the embryo shown by sharply curved parallel lines. Observe the attach-
ment of the scutellum to the caulicle at the point of junction of the plumule
and the radicle. The scutellum is a part of the embryo and represents a
cotyledon.
Dissect out an embryo from another seed, and compare with that seen in
the section.
6 BOTANY.
Exercise 4.
10. The squash (or pumpkin) seedling. — Take seedlings in different
stages of germination which have been grown in a germinator. Make
sketches of several different stages, showing the expanded cotyledons, the
plumule between them, the main root, and the origin of the lateral roots, the
hypocotyl (the portion of the stem between the root and the cotyledons).
Note the "peg" on the hypocotyl and determine the way in which this
organ assists the embryo in getting out of the seed coats. Compare seed-
lings growing in the soil.
11. Other seedlings. — Make a similar study of the bean, pea, and corn
seedlings, both from seeds germinated in folds of damp paper, and from
those grown in the soil. Sketch the different stages, and write a full descrip-
tion and comparison, noting the points of agreement and disagreement
between them, and the different ways in which the seedlings come up from
the ground.
(Consult Chapter 33).
Material. — Seeds of the pumpkin or squash, beans, peas, and corn.
These should be soaked in water for about twenty-four hours before they
are wanted for the study of the seed.
Seedlings of the same plants in different stages of germination. Some of
the seeds should be germinated in folds of wet paper or in moss, and some
of them should be planted in soil in pots. These should be started about a
week in advance of the time when they are wanted for study by the student.
The number of seeds and seedlings which should be prepared will depend on
the number of students in the class. A surplus of material should be pro-
vided for.
CHAPTER II.
WINTER BUDS, SHOOTS, ETC.
12. Season for study of shoots. — Either the autumn or the
winter is an excellent time for some observations of the winter
condition of plants, especially of the stems or shoots, as well as
the leaves. While actual growth of the parts cannot then be
observed, certain interesting and important peculiarities of the
stems and leaves can then be easily studied. The exercises are
also instructive for classes which have not had previous instruc-
tion in nature studies.
13. Annuals, biennials, perennials.— One of the striking
things which we observe during the winter season is the fact that
certain plants, especially the herbs, like many weeds and culti-
vated plants, are dead and dry. Where the plant makes its
entire growth during the year or season, and ripens at the close, it
is an annual. The bean, corn, squash, the ragweed, etc., are
annuals. Other plants, like the thistle, mullein, etc., do not
mature their fruit or seed until the second year. Such plants are
biennials. Trees, shrubs, and many herbs as well, like the asters,
goldenrods, etc., live from year to year, and are therefore peren-
nials. In the goldenrods, in trillium, the toothwort, and other
perennials of this kind, the larger part of the annual growth
dies back at the close of the season, while the plant is carried
over the winter by the shorter underground stem.
14. Annual growth of the horse-chestnut. — In figure 4 there
is illustrated a shoot of the horse-chestnut. Near the middle
portion of the shoot is a ring of numerous fine scars, and
another ring of similar scars near the lower end. These rings
of scars mark the positions of successive annual terminal buds,
7
BOTANY.
so that the portion of the shoot between two
such adjacent rings, or above the last one, rep-
resents the growth in length of the shoot for one
year. At the close of the season's growth the
"bud" is formed. In the horse-chestnut the
terminal bud is broader than the diameter of the
shoot, and is ovate in form.
15. We notice that there are a number of
scales which overlap each other somewhat as
shingles do on a roof, only they are turned in
the opposite direction. If we begin at the base
of the bud, we can see that the two lowest
scales are opposite each other, and that the two
next higher ones are also opposite each other,
and set at right angles to the position of the
lower pair. In the same manner successive
pairs of scales alternate, so that the third, fifth,
seventh, etc. , are exactly over the first, and the
fourth, sixth, etc. , are exactly over the second.
Aside from the fact that these brown scales fit
closely together over the bud, we notice that
they are covered with a sticky substance which
helps to keep out the surface water. Thus a
very complete armature is provided for the pro-
tection of the young leaves inside.
16. Leaf scars. — The number of leaves de-
veloped during one season's growth in length
of the shoot can be determined by counting the
broad whitish scars which are situated just
below each pair of lateral buds. Near the
margin of these scars in the horse-chestnut are
^ seen prominent pits arranged in a row. These
_ Two-year old twig ]jttie pits in the leaf scar are formed by the
of horse chestnut.
showing buds and breaking away of the fibro-vascular bundles
leaf scars. (A twig
with a terminal bud (which run into the petiole of the leaf) as the
should have been v
selected for this fig- jeaf fans in the autumn.
ure.)
WINTER BUDS, SHOOTS, ETC.
17. Lateral buds. — The lateral buds, it is noticed, arise in
the axils of the leaves. Each one of these by growth the next
year, unless they remain dormant, will develop a shoot or
branch. Just above the junction of the upper pair of branches
we notice scars which run around the shoot in the form of
slender rings, several quite
close together. These are the
scars of the bud scales of the
previous year. By observing
the location of these ring scars
on the stem the age of the
branch may be determined, as
well as the growth in length
each year. Small buds may
be frequently seen arising in
the axils of the bud scales,
that is after the scales have
fallen, so that four to ten
small buds may be counted
sometimes on these very nar-
row zones of the shoot.
18. Bud leaves. — On re-
moving the brown scales of
the bud there is seen a pair
of thin membranous scales
which are nearly colorless.
Underneath these are young
leaves; successive pairs lie Fig. 5.
farther in the bud, in Outline Three-year-old twig of the American ash,
with sections of each year s growth showing
similar to the mature leaves, annual rings.
and each pair smaller than the one just below it. They are
very hairy, with long white woolly fibres. These woolly fibres
serve also to protect the young leaves from the cold or from
sudden changes in the temperature, since they hold the air in
their 'meshes very securely.
10 BOTANY.
19. Opening of the buds in the spring. — As the buds
"swell " in the spring of the year, when the growth of the
young leaves and of the shoot begins, the bud scales are thrown
backward and soon fall away as the leaves unfold, thus leaving
the "ring scar" which marks the start of the new year's
growth in length of the shoot.
20. Variations in different shoots. — A study of a number of
different kinds of woody shoots would serve to show us a series
of very interesting variations in the color, surface markings, out-
line of the branch, arrangement of the leaves and consequently
different modes of branching, variations in the leaf scars, the form,
size, color, and armature of the buds, as well as great variations
in the character of the bud scales. There are striking differences
between the buds of different genera, and with careful study
differences can also be seen in the members of a genus.
21. Growth in thickness of woody stems. — In the growth of
woody perennial shoots, the shoot increases in length each year
at the end. The shoot also increases in diameter each year,
though portions of the shoot one year or more old do not
increase in length. We can find where this growth in diameter
of the stem takes place by making a thin cror.s-section of a
young shoot or branch of one of the woody plants. If we take
the white ash, for example, in a cross-section of a one-year-old
shoot we observe the following zones : A central one of whitish
tissue the cells of which have thin walls. This makes a cylin-
drical column of tissue through the shoot which we call the
pith or medulla. Just outside of this pith is a ring of firmer
tissue. The inner portion of this ring shows many woody
vessels or ducts, and the outer portion smaller ducts, and a
great many thick-walled woody cells or fibres. This then is a
woody zone, or the zone of xylem.
The outer ring is made up of the bark, as we call it. In this
part are the bast cells. Between the bark and the woody zone
is a ring of small cells distinguished from the bark and the
woody inner portion by the finer texture of the cut surface.
WINTER BUDS, SHOOTS, ETC. II
This is the growing cylindrical layer of the shoot which lies
between the bark and wood throughout the extent of the shoot
and in fact the entire tree. It is the cambium.
22, Annual rings in woody stems, — If we now cut across a
ehoot of the ash which is several years old, we shall note, as
shown in fig. 5, that there are successive rings which have a
similar appearance to the woody ring in the one-year-old stem.
This can well be seen without any magnification. The larger
size of the woody ducts which are developed each spring, and
the preponderance of the fibres at the close of each season's
growth, mark well the growth in diameter which takes place
each year.
For further details consult Chapter XI, and also the author's
larger " Elementary Botany."
23. Phyilotaxy, or arrangement of leaves. — In examining
buds on the winter shoots of woody plants, we cannot fail to
be impressed with some peculiarities in the arrangement of these
members on the stem of the plant.
In the horse-chestnut, as we have already observed, the leaves
are in pairs, each one of the pair standing opposite its partner,
while the pair just below or above stand across the stem at right
angles to the position of the former pair. In other cases (the
common bed straw) the leaves are in whorls, that is, several
ctand at the same level on the axis, distributed around the
Ltem. By far the larger number of plants have their leaves
arranged alternately. A simple example of alternate leaves is
presented by the elm, where the leaves stand successively on
alternate sides of the stem, so that the distance from one leaf
to the next, as one would measure around the stem, is exactly
one half the distance around the stem. This arrangement is ^,
or the angle of divergence of one leaf from the next is £. In
the case of the sedges the angle of divergence is less, that is £.
By far the larger number of those plants which have the
alternate arrangement have the leaves set at an angle of diver-
gence represented by the fraction f .
12 BOTANY.
24. Other angles of divergence. — Other angles of divergence
have been discovered, and much stress has been laid on what is
termed a law in the growth of the stem with reference to the
position which the leaves occupy. There are, however, numer-
ous exceptions to this regular arrangement, which have caused
some to question the importance of any theory like that of the
' ' spiral theory ' ' of growth propounded by Goethe and others
of his time.
25. Adaptation in leaf arrangement. — As a result, however,
of one arrangement or another we see a beautiful adaptation of
the plant parts to environment, or the influence which environ-
ment, especially light, has had on the arrangement of the leaves
and branches of the plant. Access to light and air are of the
greatest importance to green plants, and one cannot fail to be
profoundly impressed with the workings of the natural laws in
obedience to which the great variety of plants have worked out
this adaptation in manifold ways.
Exercise 5.
26. Shoots of the horse- chestnut. — Select shoots with strong terminal
buds, and with several ring scars indicating several years' growth. Sketch
a shoot, showing the ring scars, the leaf scars, the lateral and terminal buds,
the lenticels (small rough elevations scattered over the surface of the twig,
made up of corky tissue through which air is admitted). Note that the lat-
eral buds arise in the axils of leaves (above the leaf scars). Are there buds
in the axils of all the leaf scars on the shoot ? How do they differ in size ?
Note that the larger and longer ones, from which the lateral branches usually
arise, are usually situated near the terminal portion of each year's growth
of the shoot. There was not room for all of the buds to grow into branches
because they would be too crowded, and would shut out light and air. In
the struggle for existence some have outgrown others which remain dormant
ready to start growth if by accident the main shoot should be broken just
above them.
Compare shoots which have lx>rne flower-clusters for several years, and
determine what effect this has had on the character of the branching.
27. Buds of the horse-chestnut. — Sketch in detail a large terminal bud.
Note the color and texture of the outer scales of the bud. Is the texture of
the outer bud scales such as to afford protection to the tender portion of the
bud within ? Is there any other means for protection of the buds ?
WINTER BUDS, SHOOTS, ETC. 13
Remove the scales one by one, determining the number, and their ar-
rangement on the axis, as well as the difference in texture and form. Make
a longitudinal section of the bud, and sketch one half to show the relation of
the scales in the bud. Make a cross-section and sketch.
28. Annual growth in thickness as shown by the " annual rings. " —
With a sharp knife make cross- sections of the shoots of different ages, and
from the number of annual rings determine the age of the shoot. Compare
the annual rings with the number of ring scars on the shoot and see if the
age of the shoot determined by both means is the same.
Exercise 6.
29. Comparative study of other shoots. — Study in a similar way other
shoots, taking for example the walnut or butternut, the birch, elm, dog-
wood, peach, apple, etc. The selection may be made from trees or shrubs
which are accessible, and for the purpose of illustrating several different
types.
Sketch the form of the shoot, the position of the leaf scars, of the ring
scars, of the buds, lenticels, etc.
Make careful notes upon these characters, as well as on the different col-
ors, surface markings, etc.
Determine the age of the shoots, and of the branches, the relation of the
dormant buds to those which have developed into the lateral shoots or
branches. Determine the effect which fruit buds have had on the branching
of the different species.
Make cross-sections and determine the age by the annual rings.
Exercise 7.
30. Comparative study of other buds. — Study the buds of several different
shoots of trees and shrubs, for the purpose of determining the variations in
the form of the bud scales, and the different means for the protection of the
delicate scales within.
Examples suggested are as follows : walnut or butternut, hickory, cur-
rant, etc.
Sketch the form and surface characters of the buds, and note the color, or
other characters.
Remove the scales one by one, note their arrangement on the shoot, their
relation one to another in the bud. Determine the number of scales in a bud
of the different kinds. Sketch the different forms of bud scales in each differ-
ent kind of bud, arranging the sketches to represent the number of the scales,
their form, and relative position on the axis, but far enough separated to
show the details of each.
14 BOTANY.
Exercise 8.
13. Comparison of leaf arrangement. — Study the arrangement of the leaves
on several different shoots, by an examination of the leaf scars or by the buds.
The teacher can select shoots which represent several different systems of
phyllotaxy, for example the opposite and the alternate; among the alternate
let the pupil determine those which have the angles of divergence repre-
sented by the fractions £, i, f, f, etc.
Exercise 9.
32. Field observations on trees and shoots. — If the weather is favorable
an excursion to the woods, fields, or to some park or garden would be an ap-
propriate conclusion to these exercises. The result can be made the basis of
a short paper by each student. For example, let the pupil observe the habit
(that is, the general form, character of branching, etc.) of different trees ; the
character of the bark ; any further peculiarities of buds and shoots ; the dif-
ferences between deciduous trees (those which shed all their leaves in the
autumn, or whose leaves die), and evergreens. (In the evergreens the leaves
remain green and attached to the trees for more than a year, for example in
the pines for about three years. In this way while new leaves are formed
each year, and old leaves are shed each year, there are green leaves on the
tree at all seasons.)
Material (for exercises 5-8). — Shoots showing two or three years' growth
of the following species (or others which may be more convenient in some
localities) : horse-chestnut, birch, dogwood, apple, peach, etc., a selection
to represent several different types. In selecting some of the shoots it will
be well to collect some which have borne fruit and which have fruit buds, in
order to compare the different type of branching induced on the fruit-bearing
shoots. (If some of the material can be collected when the leaves are present
and preserved, such leafy shoots will be interesting for comparison, especially
shoots of the birch, which have short lateral branches bearing only two
leaves each year.)
CHAPTER III.
THE LIVING SUBSTANCE OF PLANTS.
I. PROTOPLASM IN ROOT HAIRS OF SEEDLINGS.
33. Importance of studying protoplasm. — Now that we have
become familiar with the parts of the seedling, have studied the
germination of the seed, and have observed the increase in size
and elongation of its parts we are impressed with the fact that it
is a living thing. It is now time to inquire into the nature of
the living substance of plants. Plant growth as well as some of
the other life processes which we are about to study are at
bottom dependent on this living matter. It is evident, then,
that we should know something about it, how it appears, and
how it acts. For with this knowledge it is easier to comprehend
how the plant does its work as a living being. This living sub-
stance of plants is protoplasm. The student should now observe
protoplasm in several plants. If there are not a sufficient num-
ber of microscopes to enable the students to make and study
their own preparations, let the teacher prepare a demonstration
for the members of the class.
Demonstration 2.
34. To prepare seedlings with clean root hairs. — Begin to prepare the
seeds several days or a week before they are wanted for study. Soak a
handful of corn or beans, radishes, etc. (or more if there is a large class) in an
abundance of water for 24 hours. Prepare a moist chamber by placing a
layer of moss (sphagnum) or cotton in the bottom of a wide vessel (a crockery
plate or a germinator with a fluted bottom). Upon this place a layer of filter
paper. Have the sphagnum and filter paper well wetted, but not with a sur-
15
1 6 BOTANY.
plus of water. Remove the seeds from the water and scatter them over the
paper. Place another sheet of wet filter paper over them, and if it is necessary,
in order to keep the seeds moist, scatter among
them a little damp absorbent cotton. Cover
with a glass or with an inverted vessel to pre-
vent too rapid evaporation of the moisture. Set
aside in a warm place, about 22° C. to 25° C.
(about 7O°-8o° Fahr.). Look at the culture Fig. 6.
every day to see that there is just the right Seedling of radish, showing root
amount of water to keep the seeds from drying,
and also to see that there is not a surplus of water or the seeds will rot.
When the roots have begun to appear from the seeds remove the upper
layer of paper and moss so that the root hairs can develop without interfer-
ence. When the young roots just back of the tip are covered with a downy
growth of colorless hairs, as in figure 6, they are ready for use.
Demonstration 3.
35. To prepare the root hairs for examination with the microscope. —
Hold the root between the thumb and finger (or in this position between two
thin pieces of elder pith to give it support). Then with a sharp razor, the
blade resting on the forefinger and the edge against the root in the region of
the root hairs, make a sliding cut across the root. Make several successive
similar cuts in such a way as to get thin cross-sections of the root with the
root hairs attached. Mount these sections in a drop of water on a glass slip
and cover with a clean circle cover glass. Or with the needles tease out
a small portion of the root with the root hairs attached. Tease apart the
tissues in a drop of water, being careful not to break off the root hairs, and
mount in water on a glass slip. Place the slip under the microscope and focus
the microscope on suitable root hairs for demonstration of the protoplasm.
Let each pupil be seated at the microscope for a few moments to observe the
protoplasm in the root hairs.
Demonstration 4.
36. Protoplasm in the root hairs. — Examining this preparation with the
aid of the microscope we see that each thread or root hair is a continuous
tube. It is a single plant cell which has become very much elongated and
free by pushing out its free end some distance from the other cells of the
outer portion of the root. Observe the boundary wall of the thread. This is
the cell wall. Within this the protoplasm is seen. It is colorless and very
granular, that is, numerous small granules of different sizes lie quite closely
together in a colorless slimy liquid. This is the protoplasm. It does not
THE LIVING SUBSTANCE OF PLANTS.
entirely fill the root hair. But here and there are seen strands of this sub-
stance which cross the thread leaving clear spaces between. Or the clear
spaces appear as rounded vacuoles of different sizes,
or the vacuoles are more or less elongated. These
clear spaces in the root hair are occupied by a watery
substance known as the cell sap.
Demonstration 5.
37. Test for protoplasm. — Draw off the water from
under the cover glass by the use of filter paper, and
at the same time add some of the solution of iodine
with a medicine dropper. Observe that the proto-
plasm is stained a yellowish-brown color. This is
the reaction of protoplasm in the presence of iodine.
Exercise 1 O.
38. Study root hairs of seedlings. — Some of the
seedlings prepared in demonstration 2 can be used
by the members of the class for a study of the gross
appearance of the root hairs.
Make a sketch of the seedling showing what por-
tion of the root is covered by the root hairs. Why
are not the root tips covered with the root hairs?
Why are the root hairs absent from the older portions
of the roots ? As to strength and firmness how do
the root hairs and roots compare ? Test this by
handling.
Immerse the portion of the root covered by the
root hairs for a few moments in a solution of iodine.
Do they take the stain ? Will the stain all wash out
in water when immersed for a few moments ?
Take a fresh seedling with uninjured root hairs
and immerse the root for a few moments in a 1%
aqueous solution of eosin. Rinse in water. Do the root hairs hold the
stain ? Immerse the root for a few moments in strong alcohol, or in 2%
formalin, and then immerse the root hairs in eosin. Rinse in water. Do the
root hairs hold the stain now ? Why ?
Write out a complete account of your experiments and observations.
Fig. 7.
Root hairs of corn be-
fore and after treatment
with 5% salt solution.
18 BOTANY.
Synopsis. — The root hairs are formed near the growing end of the young
root.
The root hair is a single plant cell, very long and narrow.
The root hair is formed by the elongation of one of the outer cells of the
root.
Cell wall, the enclosing cellulose membrane to protect and hold
the cell contents.
Protoplasm.
Nucleus.
The root-
hair cell.
Granular protoplasm, arranged differently from that in spiro-
gyra ; a wall layer, and then stout strands and masses
which reach across with clear rounded spaces between (the
vacuoles).
Cell sap, in the vacuoles.
L Chlorophyll absent.
Reactions of the protoplasm ; is killed, and stained yellowish brown with
iodine; a 1% aqueous solution of eosin does not stain it; it does stain with the
eosin when first killed with alcohol.
Materials. — Young seedlings of radish, corn, squash, or other plants, with
clean root hairs, grown in a germinator (see Demonstration 2).
A solution of iodine.
A 1% aqueous solution of eosin.
95$ alcohol (commercial strength).
Watch glasses to receive small quantities of these solutions when the pupils
are engaged in exercise 10. Medicine droppers.
For the demonstrations : Microscope, razor, glass slips, cover-glass circles,
dissecting needles. (Hereafter the microscope and accessories will not be
listed in each case for the demonstrations ; microscope, etc. , will be inserted
instead.)
CHAPTER IV.
THE LIVING SUBSTANCE OF PLANTS— CONTINUED.
II. PROTOPLASM IN AN ALGA: SPIROGYRA.
39, The plant spirogyra,* — There are a number of algae
which would serve the pmrpose quite as well as spirogyra, but
we shall want to employ this plant again at a later time, and
it is well now to become familiar with it. It is found in the
water of pools, ditches, ponds, or in streams of slow-running
water. It is green in color, and occurs in loose mats, usually
floating near the surface. The name " pond scum " is some-
times given to this plant, along with others which are more or
less closely related. If we lift a portion of it from the water,
we see that the mat is made up of a great tangle of green silky
threads. Each one of these threads is a plant, so that ^ the
number contained in one of these floating mats is very great.
Demonstration 6.
40. To prepare spirogyra for study under the microscope. — Lift up a bit of
this thread tangle with a needle and place it in a drop of water on a " glass
slip." With the needles tease apart the threads so that they will be scattered
in the water. Now place over these threads in the water a clean, thin, glass
circle. Place the preparation on the stage of the microscope and adjust for
observation of a thread. Let the pupils first examine the plant under the
low power of the microscope, and then under the high power. They should
* If spirogyra is in fruit some of the threads will be lying parallel in pairs,
and connected by short tubes. In some of the cells may be found rounded or
oval bodies known as zygospores. These may be seen in figure 93 and will
be described in another part of the book.
19
20
BOTANY.
first observe certain things about the plant enumerated in paragraphs 41 and 42,
- so that they will be able to tell it from other minute green
algae. When these things have been observed the protoplasm
can be demonstrated. At one sitting each pupil can ob-
serve the things called for in paragraphs 41-44 ; make
sketches and notes.
41. Chlorophyll bands in spirogyra. — We first
observe the presence of bands, green in color,
the edges of which are usually very irregularly
notched. These bands course along in a spiral
manner near the surface of the thread. There
may be one or several of these spirals, according
to the species which we happen to select for
study. This green coloring matter of the band
is chlorophyll, and this substance, which also oc-
curs in the higher green plants, will be considered
in a later chapter. At quite regular intervals in
the chlorophyll band are small starch grains,
grouped in a rounded mass.
42. The spirogyra thread consists of cylind-
rical cells end to end. — Another thing which
attracts our attention, as we examine a thread
of spirogyra under the microscope, is that the
thread is made up of cylindrical segments or
compartments placed end to end. We can see
a distinct separating line between the ends.
Each one of these segments or compartments
of the thread is a cell, and the boundary wall is
in the form of a cylinder with closed ends.
43. Protoplasm. — Having distinguished these
Fig. s. parts of the plant we can look for the proto-
Thread of spiro- , .... T
gyra, showing long plasm, it occurs within the cells. It is color-
ceils, chlorophyll ./.,..»
band, nucleus, less (i.e., hvalme) and consequently requires
strands of proto-
plasm, and the close observation. Near the centre of the cell
granular wall layer
of protoplasm. can be seen a rather dense granular body ot an
elliptical or irregular form, with its long diameter transverse to
THE LIVING SUBSTANCE OF PLANTS.
21
the axis of the cell in some species; or triangular, or quadrate
in others. This is the nucleus. Around the nucleus is a
granular layer from which delicate threads of a shiny granular
substance radiate in a star-like manner, and terminate in the
chlorophyll band by one of the groups cf starch grains. A
granular layer of the same substance lines the inside of the cell
wall, and can be seen through the microscope if it is properly
focussed. This granular substance in the cell is protoplasm.
44. Cell-sap in spirogyra. — The greater part of the interior
space of the cell, that between the radiating strands of proto-
plasm, is occupied by a watery fluid, the " cell-sap."
Demonstration 7.
45. Test for protoplasm in spirogyra. — Mount a few threads of spirogyra
in a drop of weak solution of iodine for microscopic examination.
Fig. 9.
Cell of spirogyra before treat-
ment with iodine.
Fig. io.
Cell of spirogyra after treatment
with iodine.
The iodine gives a yellowish-brown color to the protoplasm,
and it can be more distinctly seen. The nucleus is also much
more prominent since it colors deeply, and we can perceive
within the nucleus one small rounded body, sometimes more,
22 BO 7 'A NY.
the nucleolus. The iodine here has killed and stained the
protoplasm.
46. Living protoplasm resists the action of some reagents.—
If a few living threads are placed in a \<f, aqueous solution of
eosin, and after a time washed, the protoplasm remains un-
colored. This teaches that protoplasm in a living condition
resists for a time the action of some reagents. (The iodine
and eosin here used are called reagents.) But let us place
these threads for a short time, two or three minutes, in strong
alcohol, which kills the protoplasm. Then mount them in the
eosin solution. The protoplasm now takes the eosin stain.
After the protoplasm has been killed the nucleus is no longer
elliptical or angular in outline, but is rounded. The strands
of protoplasm are no longer in tension as they were when alive.
Exercise 1 1 .
47. The alga spirogyra. — Place some of the threads in a shallow vessel
of water. Note the appearance of the threads, their length. Determine if
branches are present or not. If a small hand lens is convenient, spread some
of the threads out between two glass slips, and holding the preparation toward
a lighted window look at it through the lens. Describe what is seen. Lift
some of the threads with the aid of a needle, and notice how long and delicate
they are. Feel of some between the thumb and finger. Pinch some of the
threads and again place them in the water. Write an account of the observations.
Place some threads in a small quantity of alcohol and let remain for
several minutes. Does the alcohol become colored green ? Why ?
Place some of the threads in a solution of iodine for a few moments. Rinse
them in water. Do the threads hold the color ? What is the color ?
Place some fresh threads in a \% solution of eosin for a few moments. Rinse
in water. Do the threads hold the stain ? Why ? Place the same threads
for a few moments in strong alcohol, and then in the eosin. Rinse in water.
Do the threads now hold the color ? Why ?
W7rite out a complete account of your experiments and observations in this
study of the gross characters of the plant spirogyra.
THE LIVING SUBSTANCE OF PLANTS.
Spirogyra
cell.
Synopsis. — The spirogyra plant occurs in quiet water.
(" A single cell, cylindrical, is a section of a long thread.
Cell wall of cellulose.
Chlorophyll band, flattened, coiled spirally around the inner side
of the wall, colored green by the chlorophyll substance.
Nucleus, granular, near centre of cell.
Small nucleolus within nucleus.
Protoplasm proper (cytoplasm) radiating in strands
Protoplasm. \ from tne nucleus ; thin wall layer next the cell
wall.
Cell-sap (watery substance) occupying the spaces
[_ between the strands of protoplasm.
I. (Starch masses in the chlorophyll band.)
The spirogyra thread is made up of many of these cells lying end to end.
Reactions of protoplasm in spirogyra:
Stains yellowish brown with iodine.
A \% aqueous solution of eosin does not stain the living protoplasm.
Alcohol kills the protoplasm, so that eosin will then stain it.
Materials. — Fresh mats of the pond-scum spirogyra, either freshly collected
from ponds or ditches, or from an aquarium where it may be kept for a week
or more in a fresh condition.
A solution of iodine.
A 1% aqueous solution of eosin.
95$ alcohol.
Watch glasses for receiving the solutions when the pupils are engaged in
exercises II. Microscope, etc.
CHAPTER V.
THE LIVING SUBSTANCE OF PLANTS— CONCLUDED.
III. PROTOPLASM ix A FUNGUS: MUCOR.
NOTE. — Omit or read this chapter, or where there is time, if the teacher so
desires, it may be studied in addition to spirogyra, or as an alternate if spiro-
gyra cannot be obtained.
Demonstration 8.
48. To obtain the black mould. — If stock cultures of the black mould
are not at hand it is well for the teacher to make some preparation several
weeks beforehand for securing the mould for the cultures.
To do this take an orange or lemon, cut in halves, and squeeze out the
juice. Let it lie exposed in the room for a day. Then place this with some
old bread in a moist chamber and set aside in a warm room for several days.
In this time several moulds will appear. Some may have a blue color, others
white, and some will probably become black. The black one is quite likely
to be the black mould. New cultures of the black mould should now be made
on fresh bread, or on the cut surface of baked potatoes. If they are made on
potatoes the following method will answer; if on bread put the pieces in a
moist chamber and sow the spores as described here for the potato cultures.
Demonstration 9.
49. To make cultures of the black mould. — Take some freshly baked
potatoes. Make a cut about \cm deep entirely around them. Break them
into halves and place these in moist chambers on damp paper with the cut
surfaces uppermost. If a platinum needle which can be flamed is not at hand,
take a dissecting needle, thrust it for a moment into strong alcohol. Hold it
in the air until it is dry. Touch the moist surface of the potato with the
needle, then touch the black heads of the fungus on the bread or fruit to catch
some of the spores. Then touch the potato surface again, repeating this sev-
eral times until spores have been put in a number of spots. ' Close the moist
24
THE LIVING SUBSTANCE OF PLANTS. 2$
chamber and set aside in a warm place. For several days observe the growth.
First there appear small spots of delicate white threads. This tuft of threads
increases in size, the threads elongate and branch.
Demonstration 1O.
50. To prepare the mycelium of the black mould for study of the proto-
plasm.— These white threads of the mould are fungus threads. They are
called the mycelium. The mycelium is the vegetative or growing portion of
the mould, while the black heads are the fruiting portion. With a needle
carefully lift a small tuft of these threads grown in the moist chamber, place
them in a drop of water on the glass slip and carefully tease them apart so that
individual threads can be seen. Prepare for study under the microscope.
When the microscope has been focussed on a suitable group of threads each
pupil can then observe the things noted in paragraphs 51-53.
51, Mycelium of the black mould. — Under the microscope
we see only a small portion of the branched threads. There is
no chlorophyll as in spirogyra. This is one of the important
characters of the group of plants to which the black mould
belongs. In addition to the absence of chlorophyll, we see
that the mycelium is not divided at short intervals into cells;
but appears like a delicate tube with branches, which become
successively smaller toward the ends.
Fig. n.
Thread of mucor, showing protoplasm and vacuoles.
52. Appearance of the protoplasm. — Within the tube-like
thread now note the protoplasm. It has the same general
appearance as that which we noted in spirogyra. It is slimy,
or semi-fluid, partly hyaline, and partly granular, the granules
consisting of minute particles (the microtomes). While in
26 BOTANY.
mucor the protoplasm has the same general appearance as in
spirogyra, its arrangement is very different. In the first place
it is plainly continuous throughout the tube. We do not see
the prominent radiations of strands around a large nucleus, but
still the protoplasm does not fill the interior of the threads.
Here and there are rounded clear spaces termed vacuoles, which
are filled with the watery fluid, cell-sap. The nuclei in mucor
are very minute, and cannot be seen except after careful treat-
ment with special reagents.
53. Movement of the protoplasm in mucor. — While examin-
ing the protoplasm in mucor wre are likely to note streaming
movements. Often a current is seen flowing slowly down one
side of the thread, and another flowing back on the other side,
or it may all stream along in the same direction.
Exercise 1 2.
54. Study of mycelium. — Use portions of the mould which have not become
black. These portions are the mycelium, mats of the fine colorless threads.
Note the color of the threads, the absence of chlorophyll. To test this
place some of the threads in strong alcohol, let stand for some time. Does
the alcohol become colored ?
Take some fresh threads and place them in the iodine solution. Remove
and rinse in water. What is the color ?
Place fresh threads in some of the \% aqueous solution of eosin, and rinse
in water. Do the threads hold the color ? Now immerse the same threads
in strong alcohol, then rinse in water, and place in the eosin solution for a
moment. Rinse in water. Do the threads now hold the stain ? Why ?
Write out a complete account of the experiments and observations.
Exercise 13.
55. To obtain the mould from fruits. — This maybe made a home exercise
if preferred. It is well whenever possible to get the pupils to do some of the
work of preparation.
Let each pupil take half an orange or lemon, squeeze out the juice, and
leave it exposed in his living room through the day. At night place it
along with some pieces of bread in a glass tumbler, first putting a wet piece
of paper in the bottom of the tumbler. Cover the vessel with a piece of
glass. Keep in a warm room. Each day observe what appears, keeping
notes, and describing the appearance of the mycelium. Observe if the black
mould appears when the growth comes to fruit.
THE LIVING SUBSTANCE OF PLANTS. 1*]
56. Protoplasm occurs in the living parts of all plants,—
The substance we have found in the alga spirogyra, in the root
hairs of the corn seedling, in the threads of the black mould, is
essentially alike in all. It may be arranged differently in the
different plants, but its general appearance is the same. It
moves quite rapidly in the cells of some plants, but so slowly
in others that we may not see the movement. Yet when we
treat the protoplasm with well-known reagents the reaction in
general is the same. It has been found by the experience of
different investigators that the substance in plants which shows
these reactions under given conditions is protoplasm. We
have demonstrated to our satisfaction then that we have seen
protoplasm in the simple alga spirogyra, in the root hairs of the
seedling, and in the threads of the black mould. If we chose
to make sections of the stems and leaves of the seedling, or of
the living parts of other higher plants, we should find that
protoplasm is present in all these living cells. We then con-
clude that protoplasm occurs in the living parts of all plants.
57. Summary of observations on protoplasm. — While we
have by no means exhausted the study of protoplasm, we can,
from this study, draw certain conclusions as to its occurrence
and appearance in plants. Protoplasm is found in the living
and growing parts of all plants. It is a semi-fluid, or slimy,
granular, substance; in some plants, or parts of plants, the
protoplasm exhibits a streaming or gliding movement of the
granules. It is irritable. In the living condition it resists
more or less for some time the absorption of certain coloring
substances. The water may be withdrawn by glycerine. The
protoplasm may be killed by alcohol. When treated with
iodine it acquires a yellowish-brown color.
Material. — Freshly formed mycelium of the common black mould (see
demonstration 8, which also see for culture material and vessels).
A solution of iodine. A \% aqueous solution of eosin. 95$ alcohol.
Watch glasses to receive small quantities of the solutions when the pupils
are engaged in exercise 12.
Microscope, etc.
CHAPTER VI.
HOW WATER MOVES IN AND OUT OF PLANT
CELLS.
ABSORPTION, DIFFUSION, OSMOSE.
Demonstration 1 1 .
58. Osmoie in spirogyra. — Mount a few threads of the alga spirogyra in
a drop of the 5$ salt solution on a glass slip, and place on a cover glass for
microscopic examination. Let each pupil examine the preparation to ob-
serve the protoplasm contracted away from the cell wall. The protoplasmic
layer contracts slowly from the cell wall, and the movement of the mem-
brane can be watched by looking through the microscope. The membrane
contracts in such a way that all the contents of the cell are finally collected
into a rounded or oval mass which occupies the centre of the cell.
Now add fresh water and draw off the salt solution. The protoplasmic
membrane expands again, or moves out in all directions, and occupies its
former position against the inner surface of the ceil wall. This indicates
that there is some pressure from within, while this process of absorption is
going on, which causes the membrane to move out against the cell wall.
The salt solution draws water from the cell-sap. There is thus a ten-
dency to form a vacuum in the cell, and the pressure on the outside of the
protoplasmic membrane causes it to move toward the centre of the cell.
When the salt solution is removed and the thread of spirogyra is again
bathed with water, the movement of the water is inward in the cell. This
would suggest that there is some substance dissolved in the cell-sap which
does not readily filter out through the membrane, but draws on the water
outside. It is this which produces the pressure from within and crowds the
membrane out against the cell wall again.
59. Turgescence. — Were it not for the resistance which the
cell wall offers to the pressure from within, the delicate proto-
plasmic membrane would stretch to such an extent that it would
WATER IN PLANT CELLS.
29
be ruptured, and the protoplasm therefore would be killed. If
we examine the cells at the ends of the threads of spirogyra we
will see in most cases that the cell wall at the free
end is arched outward. This is brought about by
the pressure from within upon the protoplasmic
membrane which itself presses against the cell wall,
and causes it to arch outward- This is beautifully
Fig. 12.
Spirogyra before
placing in salt solu-
tion.
Fig. 14.
ra from
salt solution into
water.
Spirogyra
lt soluti
Fig. 13.
Spirogyra in 5^ salt solution
shown in the case of threads which are recently broken. The
cell wall is therefore elastic; it yields to a certain extent to the
BOTANY.
pressure from within, but a point is soon reached beyond
which it will not stretch, and an equilibrium then tends to be
established between the pressure from within on the protoplas-
mic membrane, and the pressure from without by the elastic
cell wall. This state of a cell is turgescence, or such ,a cell is
said to be turgescent, or turgid.
Demonstration 12.
60. Experiment to show diffusion through an animal membrane. — For
this experiment use a thistle tube, across the larger end of which should be
stretched and tied tightly a piece of bladder mem-
brane. A strong sugar solution (three parts sugar
to one part water) is now placed in the tube so that
the bulb is filled and the liquid extends part way
in the neck of the tube. This is immersed in water
within a wide-mouth bottle, the neck of the tube
being supported in a perforated cork in such a way
that the sugar solution in the tube is on a level with
the water in the bottle or jar. In a short while the
liquid begins to rise in the thistle tube, in the course
of several hours having risen several centimeters.
The diffusion current is thus stronger through the
membrane in the direction of the sugar solution, so
that this gains more water than it loses.
61. How diffusion takes place. — We have
here two liquids separated by an animal
membrane, water on the one hand which
diffuses readily through the membrane, while
on the other is a solution of sugar which dif-
fuses through the animal membrane with
difficulty. The water, therefore, not contain-
ing any solvent, according to a general law
which has been found to obtain in such cases, diffuses more
readily through the membrane into the sugar solution, which
thus increases in volume, and also becomes more dilute. The
bladder membrane is what is sometimes called a diffusion mem-
brane, since the diffusion currents travel through it. In this ex-
periment then the bulk of the sugar solution is increased, and the
Fig. 15-
WATER IN PLANT CELLS. 31
liquid rises in the tube by this pressure above the level of the
water in the jar outside of the thistle tube. The diffusion of
liquids through a membrane is osmosis.
62. Importance of these physical processes in plants. — Now
if we recur to our experiment with spirogyra we find that exactly
the same processes take place. The proptoplasmic membrane
is the diffusion membrane, through which the diffusion takes
place. The salt solution which is first used to bathe the
threads of the plant is a stronger solution than that of the cell-
sap within the cell. Water, therefore, is drawn out of the cell-
sap, but the substances in solution in the cell-sap do not readily
move out.. As the bulk of the cell-sap diminishes the pressure
from the outside pushes the protoplasmic membrane away from
the wall. Now when we remove the salt solution and bathe the
thread with water again, the cell-sap, being a solution of certain
substances, diffuses writh more difficulty than the water, and the
diffusion current is inward, while the protoplasmic membrane
moves out against the cell wall, and turgidity again, results.
Also in the experiments with salt on the tissues and cells of the
beet (see exercise 14), the same processes take place.
These experiments not only teach us that in the protoplasmic
membrane, the cell wall, and the cell-sap of plants do we have
structures which are capable of performing these physical
processes, but they also show that these processes are of the
utmost importance to the plant, in giving the plant the power
to take up solutions of nutriment from the soil.
Exercise 14.
63. To test the effect of a 5$ salt solution on a portion of the tissues of a
beet.— Select a red beet. Cut several slices about \cm in diameter and
about $mm thick. Grasp the slices between the thumb and forefinger and
attempt to bend them by light pressure. They are quite rigid and bend but
little. Immerse a few of the slices in fresh water and a few in a 5$ salt solu-
tion. In the course of an hour or less, examine the slices again. Those in the
water remain as at first quite rigid, while those in the salt solution are more
or less flaccid or limp. They readily bend by pressure between the fingers.
The salt solution, we judge after our experiment with spirogyra, with-
32 BOTANY.
draws some of the water from the cell-sap, the cells thus losing their turgid,
ity and the tissues becoming limp or flaccid from the loss of water.
64. The beet slice becomes rigid again in water. — Now remove some of
the slices of the beet from the salt solutions, wash them with water and then
immerse them in fresh water. In the course of thirty minutes to one hour,
if we examine them again, they will be found to have regained, partly or
completely, their rigidity. Here again we infer from the former experiment
with spirogyra that the substances in the cell-sap now draw water inward ;
that is, the diffusion current is inward through the cell walls and the proto-
plasmic membrane, and the tissue becomes turgid again.
Exercise 1 5.
66. Turgor is lost when the protoplasm is dead. — Place some slices of a red
beet in alcohol ; also some in hot water near the boiling point. Do the alcohol
and the the hot water become colored ? Why ? Determine the condition of the
Fig. 16. Fig. 17. Fig. 18.
Rigid condition of fresh beet Limp condition after lying in Rigid again after lying
section. salt solution. in water.
Figs. 16-18. — Turgor and osmosis in slices of beet.
slices by pressure between the fingers. Are they rigid or flaccid ? Why ?
Place them now in fresh cold water. After a quarter of an hour or longer does
any change take place as regards their resistance to pressure between the
fingers ? What is the reason for their remaining in this condition ? In what
condition must protoplasm be in order to perform the work of a diffusion
membrane ?
Exercise 1 6.
66. Osmose experiments with leaves. — Take leaves of various plants, like
the geranium, coleus, or seedlings of the squash, pea, or bean, etc.
WATER IN PLANT CELLS.
33
Movement of water
in a single cell.
Immerse the leaves of some in water, and of another set in a 5$ salt solution.
The petioles of the leaves should not be immersed, for it is desirable to keep
the cut ends out of the water or salt solution. In fifteen minutes to half an
hour, lift the leaves and seedlings from the water and note the result, and
compare. Those which were in the salt solution now rinse in fresh water
and immerse for a time in water. Now note the result. Explain the results
of this experiment from the results obtained in the previous experiments.
Synopsis.
A strong salt solution draws water out of the cell-sap, and
the protoplasmic membrane is pushed inward. The
cell becomes flabby.
Remove the salt and surround the cell with water, and
I the cell-sap draws water inside again, so that the pro-
toplasmic membrane moves out and presses strongly
against the cell wall and the cell becomes rigid
("turgid ") again.
The cell-sap then is a solution of certain salts.
The beet slice is a cell mass, or a mass of tissue.
Placed in salt solution some of the water is drawn out
of the cell-sap of all the cells by the salt solution ;
the mass of cells, or the slice, becomes flabby.
Placed in water it becomes rigid, or turgid, again.
The action is the same as in the single cell, but all the
cells act in concert.
I The action is the same with leaves, and other soft cell
(^ masses, or plant parts.
When water and a salt, or sugar, solution are separated by an animal
membrane, the current of water is stronger toward the salt, or sugar, solu-
tion. The membrane holds back for a time the substance dissolved in the
water. So the protoplasmic membrane acts in the same way when it sepa-
rates two different liquids, where one is a stronger salt than the other, or
where one is a salt and the other is water.
When the protoplasm is killed it cannot act as a diffusion membrane.
Material. — Fresh material of spirogyra.
Fresh beets, dark red ones (winter-stored beets are good).
Leafy shoots of some succulent plants, in a fresh condition, or seedlings.
Common table salt, a 5$ solution in water.
95$ alcohol, and hot water for exercise 15.
Wide-mouth bottle, thistle tube, small piece of bladder membrane, and
sugar, for demonstration 12.
Microscope, etc.
Movement of water
in cell masses.
CHAPTER VII.
HOW PLANTS OBTAIN THEIR LIQUID FOOD.
I. WATER CULTURES.
67. How constituents of plant food are determined. — We
are now ready to inquire how plants obtain food from the soil
or water. Chemical analysis shows that certain mineral sub-
stances are common constituents of plants. By growing plants
in different solutions of these various substances it has been
possible to determine what ones are necessary constituents of
plant food. While the proportion of the mineral elements
which enter into the composition of plant food may vary con-
siderably within certain limits, the concentration of the solutions
should not exceed certain limits. A very useful solution is one
recommended by Sachs, and is as follows :
68. Formula for solution of nutrient materials. — The pro-
portions of the ingredients are here given. A larger quantity
than IQOOCC may be needed.
Water 1000 cc.
Potassium nitrate 0.5 gr.
Sodium chloride 0.5 "
Calcium sulphate 0.5 "
Magnesium sulphate 0.5 u
Calcium phosphate 0.5 "
The calcium phosphate is only partly soluble. The solution which is not
in use should be kept in a dark cool place to prevent the growth of minute
algae.
Demonstration 13.
69. To prepare the seedlings in water cultures.— Several different plants
are useful for experiments in water cultures ; peas, corn, or beans are very
34
HOW PLANTS OBTAIN THEIR LIQUID FOOD. 35
good. The seeds of these plants may be germinated, after soaking them lor
several hours in warm water, by placing them between the folds of wet paper
on shallow trays, or in the folds of wet cloth (see demonstration i). At the
same time that the seeds are placed in damp paper or cloth for germination,
one lot of the soaked seeds should be planted in good soil and kept under the
same temperature conditions, for control. When the plants have germinated
one series should be grown in distilled water, which possesses no plant food;
another in the nutrient solution, and still another in the nutrient solution to
which has been added a few drops of a solution of iron chloride or ferrous
sulphate. There would then be four series of cultures which should be
carried out with the same kind of seed in each series so that the comparisons
can be made on the same species under the different conditions. The series
should be numbered and recorded as follows :
No. i, soil.
No. 2, distilled water.
No. 3, nutrient solution.
No. 4, nutrient solution with a few drops of iron solution added.
70. How to set up tLe experiment. — Small jars or wide-mouth bottles, or
crockery jars, can be used for the water cultures, and the cultures are set up
as follows : A cork which will just fit in the
mouth of tne bottle, or which can be supported
by pins, is perforated so that there is room to
insert the seftdling, with the root projecting
below into the liquid. The seed can be
fastened in position by inserting a pin through
one side, if it is a large one, or in the case
of small seeds a cloth of a coarse mesh can
be tied over the mouth of the bottle instead of
using the cork. After properly setting up the
experiments the cultures should be arranged in
a suitable place, and observed from time to
time during several weeks. In order to obtain
more satisfactory results several duplicate series
should be set 'up to guard against the error
which might arise from variation in individual
plants and from accident. Where there are Fig. 19.
several students in a class, a single series set Culture cylinder to show position
of corn seedling (Hansen).
up by several will act as checks upon one an-
other. If glass jars are used for the liquid cultures they should be wrapped
with black paper or cloth to exclude the light from the liquid, otherwise
numerous minute algae are apt to grow and interfere with the experiment. If
crockery jars are used they will not need covering.
36 BOTANY.
71. Result of the experiment. — For some time all the plants grow equally
well, until the nutriment stored in the seed is exhausted. The numbers I, 3
and 4, in soil and nutrient solutions, should outstrip number 2, the plants in
the distilled water. No. 4 in the nutrient solution with iron, having a perfect
food, compares favorably with the plants in the soil.
Exercise 1 7.
72. Notes on the water cultures. — When the water cultures are set up the
members of the class can take notes on them. Then from time to time for
several months the plants should be inspected and the members of the class
should keep a record of the results, and should not only compare the plants in
Fig. 20. Fig. 21. Fig. 22. Fig. 23.
In soil. Nutrient solu- Nutrient solu- In distilled
tion with iron. tion without water.
iron.
Figures 20-23. — Comparison of growth of pumpkin seedlings, all started at the same time.
the different jars, but should compare them with the plants growing in the
soil which were planted at the same time. From these records let each pupil
write a complete account of the experiment.
II. How PLANTS OBTAIN FOOD FROM THE SOIL.
73. Plants take liquid food from the soil. — From these
experiments then we judge that such plants take up the food
they receive from the soil in the form of a liquid, the elements
being in solution in water.
HOW PLANTS OBTAIN THEIR LIQUID FOOD. 37
If we recur now to the experiments which were performed
with the salt solution on the cells of spirogyra, in the cells of
the beet, and the way in which these cells become turgid again
when the salt solution is removed and they are again bathed
with water, we will have an indication of the way in which
plants take up nutrient solutions of food material through their
roots.
It should be understood that food substances in solution
during absorption diffuse through the protoplasmic membrane
independently of each other and also independently of the rate
of movement^of the water from the soil into the root hairs and
cells of the roots. When the cell-sap is poor in certain sub-
stances which are dissolved in the surrounding water of the soil,
these substances diffuse inwardly more rapidly. But as the
cell-sap becomes richer in that particular food substance its
further absorption is correspondingly diminished until the cell-
sap becomes poorer again, as by diffusion this substance passes
on into other cells.
74. How food solutions are carried into the plant. — We can
see how the root hairs are able to take up solutions of plant
food, and we must next turn our attention to the way in which
these solutions are carried further into the plant. We should
make a section across the root of a seedling in the region of the
root hairs and examine it with the aid of a microscope. We
here see that the root hairs are formed by the elongation of
certain of the surface cells of the root. These cells elongate
perpendicularly to the root, and become $mm to 6mm long.
They are flexuous or irregular in outline and cylindrical, as
shown in fig. 24. The end of the hair next the root fits in
between the adjacent superficial cells of the root and joins
closely to the next deeper layer of cells. In studying the
section of the young root we see that the root is made up of
cells which lie closely side by side, each with its wall, its
protoplasm, and cell-sap, the protoplasmic membrane lying on
the inside of each cell wall.
38 BOTANY.
Demonstration 14.
75. To show the relation of the root hairs to the other cells of the root.—
The teacher can make thin sections of young roots, with a razor, through the
region of the root hairs, and mount them for microscopic study for demon-
Section of corn root, showing rhizoids formed from elongated epidermal cells.
stration before the class. Let each member of the class sketch a portion of
the section, to show the root hairs, their relation to the other cells of the root,
as well as some of the characters of the tissues of the root.
76. Action of the cell-sap. — In the absorption of the watery
solutions of plant food by the root hairs, the cell-sap, being a
more concentrated solution, gains some of the former, since the
liquid of less concentration flows through the protoplasmic
membrane into the more concentrated cell-sap, increasing the
bulk of the latter. This makes the root hairs turgid, and at the
same time dilutes the cell-sap so that the concentration is not so
great. The cells of the root lyin^ inside and close to the base ol
HOW PLANTS OBTAIN THEIR LIQUID FOOD. 39
the root hairs have a cell-sap which is now more concentrated
than the diluted cell-sap of the hairs, and consequently gain some
of the food solutions from the latter, which tends to lessen the
content of the root hairs and also to increase the concentration of
the cell-sap of the same. This makes it possible for the root hairs
to draw on the soil for more of the food solutions, and thus, by
a variation in the concentration of the substances in solution in
the cell-sap of the different cells, the food solutions are carried
along until they reach the vascular bundles, through which the
solutions are carried to distant parts of the plant. In this way a
pressure is produced which causes the liquid to rise in the plant.
77. How the root hairs get the watery solutions from the
soil. — If we examine the root hairs of a number of seedlings
which are growing in the soil under normal conditions, we shall
Fig 25.
Uoot hairs of corn seedling with soil particles adhering closely.
that a large quantity of soil readily clings to
the roots. We should note also that unless the
soil has been recently watered there is no free water in it; the
soil is only moist. We are curious to know how plants can
obtain water from soil which is not wet. If we attempt to
wash off the soil from the roots, being careful not to break
4O BOTANY.
away the root hairs, we find that small particles cling so
tenaciously to the root hairs that they are not removed.
Placing a few such root hairs under the microscope it appears
as if here and there the root hairs were glued to the minute
soil particles.
In soil most suitable for the growth of land plants the water is
not in excess. It is in the form of a thin film surrounding the
soil particles. Some of the soil particles being "glued" to
the root hairs, this portion of the water film is brought into
close contact with the root hairs so that it can be absorbed.
Plants cannot remove all the water from the soil.
NOTE. — Some plant food is in solution in the water of the soil, but much
of it is in an insoluble form (minute particles, or rocks, containing mineral
substances), or in the form of organic matter (as leaves, stems, or other plant
parts, or animal matter). The organic matter in the soil is in process of
decay because certain microscopic fungi, and especially bacteria, feed upon
it and change some of it into a form which can be taken up as food by the
higher plant. The insoluble particles, containing mineral substances, are
constantly being corroded by the action of certain acids, especially carbonic
acid, which is constantly being formed in the soil. The walls of the root hairs
are also saturated with this acid, and thus they are able to dissolve some of
these mineral substances. This corroding action of the roots can be well
shown by placing a small marble plate in a pot; then plant beans or peas on
the plate, and cover with earth. In lieu of the marble plate the peas may be
planted in clam, or oyster, shells, which are then buried in the soil of the
pot, so that the roots from- the seedlings will come in contact with the smooth
surface of the shell, or of the marble if that is used. After the plants have
been growing two or three weeks, remove the soil, and wash the surface of
the marble or shell. Hold the surface now toward the window in such a
way as to see the light reflected from the ' surface. The surface has been
etched by the action of the roots.
Demonstration 1 5 (or Exercise).
78. Plants can obtain water from soil which appears dry.— Use small pots
with well-grown seedlings. Place the pots in a dry room. Supply no water
to the soil. From day to day observe the condition of the soil, and feel of it
to note the condition of dryness. Can plants live and grow in a soil which
looks and feels dry ?
When the plants have wilted remove them from the soil. Weigh the pot
of soil. Then place it in an oven and bake it. Weigh again. Has it lost
HOW PLANTS OBTAIN THEIR LIQUID FOOD. 41
weight ? Can plants remove all the moisture irom the soil by absorption
through their roots ?
Demonstration 1 5a (or Exercise).
78a. To demonstrate the action of a root hair. — Take a long potato, cutoff
the ends squarely, and bore a smooth hole
from one end nearly through to the other
end, being careful not to split the potato.
Now pare off the sides to make a tube closed
at one end. Rest the closed end in a vessel
of water, as shown in fig. 250, after having
filled the tube with sugar. After five or
six hours examine. The sugar inside of the
potato tube draws water inward from the
vessel, imitating the action of a root hair.
Exercise 18.
79. Salt particles cling to root hairs.- potato
Have at hand small pots of seedlings the tainmg sugar
cavty con.
standing in vessel of
,-,... j. water. B, section of potato tube
SOll Of which IS not wet. Pull, or dig, up a showing cavity only partly filled with
seedling. Observe the soil clinging to the susar- <After MacDougal.)
roots. Agitate it to remove as much of the soil as possible. Wash the roots
by rinsing in water. Are all the soil particles removed ? To what portions
of the roots does most of the soil cling ? Why ? Compare with seedlings
grown in a germinator free from soil.
III. STRONG SOLUTIONS OF PLANT FOOD ARE INJURIOUS.
Exercise 1 9 (or Demonstration).
80. To show the effect on plants of food solutions which are too strong. —
Potassium nitrate is one of the food substances used in the water cultures.
It is also one of the necessary food substances from which nitrogen is
obtained for the plant. Take strongly concentrated solutions, say a 5$, a 10^,
and a 20$ solution. Label three pots of seedlings to correspond with the
solutions. Pour in enough of each solution to the corresponding pots to
saturate the soil. In the course of three or four hours (or later) observe the
result. Observe the condition of the stems at the surface of the ground.
Explain the result in each case. Permit these to remain without watering
for a day to see if they will revive. Pour in water and wash through
to remove as much of the salt as possible. Set them aside for a day or two.
Do they revive ? Why ?
BOTANY.
81. Food solutions which are too strong injure plants
instead of benefiting them. — In figures 27 to 33 are shown the
results of some experiments
with strongly concentrated
food solutions. In this case
the food substance is potas-
sium nitrate. Solutions of
this salt of 2%, 5#, io#, and
2of0 were prepared. Three
pots of pumpkin seedlings
were employed. In one the
soil (which was already quite
moist in all of the pots) was
saturated with the 2%, one with
the 10$, and the other with the
2of0 solution. In a few hours
the seedlings in pots 31 and 32
had collapsed, while those in
pot 30 were still rigid. The
salt in 31 and 32, being, even
when diluted with the water in
the soil, stronger than the salts
in the cell-sap, withdrew water
Fig. 26. ' .
Pumpkin seedling removed from soil to show from the rOOt hairs> TOOtS, and
from the lower part of the
stems, so that the plants lost their rigidity. The lower part of
the stems was flabby. The plants' were then photographed as
shown in figures 30-32. Some of the 5$ solution was then
added to pot 30. In four hours (at 6 P.M.) two of the seed-
lings showed signs of collapse. On the following morning
these two had collapsed, and the photograph of the result is
shown in figure 33.
Synopsis. — Plants obtain their food either in a liquid or a gaseous form.
Plants obtain their liquid food (mostly certain mineral and nitrogenous
substances) by absorption.
HOW PLANTS OBTAIN THEIR LIQUID FOOD. 43
Fig. 27. Fig. 28. Fig. 29.
•2% solution potassium 10/6 solution potassium 20$ solution potassium
nitrate. nitrate. nitrate.
Figures 27-20. — Pumpkin seedlings, soil watered with solution of potassium nitrate of
different strengths. Photographed immediately after the application of the solution to
tVi*i cr»i1
Fig. 30. Fig. 31. Fig. 32.
•2% solution potassium io# solution potassium -20% solution potassium
nitrate. nitrate. nitrate.
Figures 30-32. — Pumpkin seedlings, soil watered with solution of potassium nitrate
of different strengths. Photographed four hours after application of the solution to
the soil.
44
BOTANY.
Plants having a root system in comparatively dry ground absorb their
liquid food through root hairs and roots.
Aquatic plants (plants in water) absorb liquid food through nearly the
entire surface in contact with the water.
The plant food must be in a very dilute solution; a strong solution injures
the plant, and, if too strong,
will kill the plant, becaxise
by the law of diffusion the
water in the plant is removed
to such an extent that the
plant becomes flabby, and if
turgor is not restored, the
plant will die.
Soil which is not saturated
with water, i.e., that which
is only moist, or even which
may seem dry, still contains
water which forms a thin film
(capillary film) around the
soil particles.
The root hairs become
firmly fixed to certain of the
soil particles and are thus
brought in close contact with
the water film which contains
mineral and nitrogenous food
Fig. 33.
Pot in which the 2% solution was poured.
After four hours a 5$ solution of potassium ni-
trate was added. This caused two of the seed- . . . ™. . ,,,
lings to collapse after about ten hours. Photo- m solution. 1 his him is con
graphed eighteen hours after last application. tinuous from one soil particle
to another in soil of the right texture and physical properties, and thus as
the root hairs absorb that portion of the film in contact with them, by capil-
larity the film draws more water through the soil from moist places.
Materials:— Potassium nitrate, sodium' chloride, calcium sulphate, mag-
nesium sulphate, calcium phosphate, for nutrient solution as per paragraph
68. A larger amount of potassium nitrate (saltpetre) for exercise 19.
Wide-mouth bottles, or small crockery jars, with perforated corks to fit, for
the water culture.
Seedlings started in a germinator.
Seedlings, grown in pots, two or three weeks old, for exercises 17 and 18.
One or more long potatoes ; sugar.
Microscope, etc. Razor.
CHAPTER VIII.
HOW SOME PLANT PARTS REMAIN RIGID.
82. Turgidity of plant parts, — In Chapter VI we found that
the turgescence of a cell depends on the absorption of water by
Fig. 34- Fig. 35.
Indian turnip plant just removed from the Same plant half an hour later. It is be-
soil. It is rigid. coining limp.
protoplasm. The protoplasm permits the cell-sap to draw the
water inward by diffusion, but the protoplasmic membrane does
not permit the water to filter out readily, and the outward pressure
45
40 BOTANY.
of the protoplasm on the elastic cell wall makes the cell turgid.
So we found in the experiments with the slices of beet in the salt
solution and water that the partial removal of the water from the
beet leaves the slices limp, while they regain their rigidity if the
salt solution is removed and the slices are placed in water. We
should now endeavor to see if water plays any part in the rigidity
of plant parts, as in the case of shoots, leaves, etc., and in what
way this rigidity may be lost and regained.
Exercise 2O.
83. Loss of turgidity in cut shoots. — From a living geranium, balsam,
coleus, or other plant, cut a leafy shoot i^cin to 2Ocm long. Leave it in a
dry room for a short while until
it partly wilts. Grasp the shoot
at the cut end and attempt to
hold it erect. How does it now
compare with its condition when
first cut from the plant ?
84. Eestoration of turgidity
in shoots. — Take the leafy shoot
used in paragraph 83. (It should
not be so wilted that any portion
of it is dry.) Cut the end fresh
again and place it in a vessel of
H,^ water, and if the room is dry,
'£ cover the vessel and shoot with
a tall glass cylinder or bell jar.
Observe the result in a few hours,
or on the following day.
85. Longitudinal tissue
tension. — For this in early
summer one may use the
young and succulent shoots
of the elder (sambucus);
Same plant photoglpheffour hours later. It Or the petioles of rhubarb
during the summer and early
autumn; or the petioles of richardia. Petioles of caladium are
HOW .SOME PLANT PARTS REMAIN RIGID. 47
excellent for this purpose, and these may be had at almost
any season of the year from the greenhouses, and are thus
especially advantageous for work
during late autumn or winter.
The tension is so strong that a
portion of such a petiole 10-
i^cm long is ample to demon-
strate it. As we grasp the lower
end of the petiole of a caladium,
or rhubarb leaf, we observe how
rigid it is, and how well it sup-
ports the heavy expanded lam-
ina of the leaf.
Exercise 2 1 .
86. To demonstrate the tissue ten-
sion.—Take a portion of the petiole of a
caladium, or of celery, or other plant,
about i$t'w long. Cut the ends off
squarely. With a knife strip off a layer
from the outside about 2-ymn in thick- p.g ^ Fig ^ pig ^
ness, and the full length of the piece. Centre of Outside Outside strip
Now attempt to replace it, comparing the Petiole' strip" attached to
centre.
length of each part. Remove another Figures 37-39. Showing longitudinal
strip lying next this one, and so on tissue tension,
until all the outer portion has been removed. Describe what takes place as
the successive strips are removed. When all are removed, compare an outside
strip with the central portion. What has happened ? Is there now a greater
difference in length between the outside strip and the central portion ? What
is the cause of this ? Describe the tensions in the outside and inner portion
of the petiole.
Cut a section of the petiole about $>cm long, remove strips on two opposite
sides and split the remainder down the middle, securing two pieces with the
center and outside portion attached. Place one of these in fresh water and
the other in a 5 per cent salt solution and note the result. If convenient
treat celery petioles in the same way. The flower stems of dandelions split
into quarters are .excellent objects to compare when placed in water, and in
a 5 per cent salt solution.
48
£ OTA NY.
Exercise 22.
87. Transverse tissue tension.— To show this take a willow shoot T,-$cm
in diameter and saw off sections about 2.cm long. Cut through the bark on
one side, and peel off the bark in one piece carefully. Now attempt to re-
place it. What has happened ? Describe the tension.
Demonstration 1 6.
88. Importance of tissue tension. — To demonstrate the efficiency of this
tension in giving support, let us take a long petiole of caladium or of rhubarb.
Hold it by one
end in a hori-
zontal position.
It is firm and
rigid, and does
not droop, or
but little. Re-
move all of the
outer portion of
the tissues, as
described
above, leaving
only the central
portion. Now
attempt to hold
it in a horizon-
tal position by
one end. It is
flabby and
Fig. 4o. S j \ droops down-
Caladium leaf petiole rigid from longitudi-
nal tensions.
ward because the longitudinal ten-
sion is removed. (See figs. 40, 41.)
Synopsis. — When plants are re-
moved from the soil, or plant parts
are removed from the shoot, they
soon become flabby and limp. pj
When these partly wilted plants Same leaf, longitudinal tension partly ren.oved
are placed with the stems in water, by the loss of two outside striPs'
they may become rigid again by the absorption of water and the restora-
tion of the rigidity of the cells.
HOW SOME PLANT PARTS REMAIN RIGID. 49
Longitudinal tissue
tension.
Transverse tissue
tension.
Succulent stems and petioles are often kept rigid be-
cause of a pull, or tension, of different layers of
cells in opposite directions. The outer layers of
cells tend to shorten, while the inner cells tend to
lengthen.
These opposite tensions, or pulls, make the shoot
rigid.
The cells of the shoots must be turgid with water or
the tension is not present.
This occurs where the outer layers of tissue are
stretched transversely instead of longitudinally.
Material. — If fresh plants cannot be obtained out-doors, use leafy shoots
of rather succulent plants from the green-house, like the coleus plant,
garden balsam, or leaves with long petioles like the caladium of the green-
house, or stored celery. The shoots should not be cut from the plant until
the pupil is ready to begin the exercise. Wide-mouthed bottles, filled with
water, and if necessary some bell jars (one large bell jar will answer for
several students).
CHAPTER IX.
HOW WATER MOVES THROUGH THE PLANT.
I. ROOT PRESSURE, OR OSMOTIC PRESSURE.
89. Flow of water from pruned vines. — It is a very common
thing to note, when certain shrubs or vines are pruned in the
spring, the exudation of a watery fluid from the cut surfaces.
In the case of the grape vine this has been known to continue
for a number of days, and in some cases the amount of liquid,
called " sap," which escapes is considerable. In many cases it
is directly traceable to the activity of the roots, or root hairs,
in the absorption of water from the soil. For this reason the
term root pressure is used to denote the force exerted in supply-
ing the water from the soil.
90. Root pressure may be measured. — It is possible to
measure not only the amount of water which the roots will raise
in a given time, but also to measure the force exerted by the
roots during root pressure. It has been found that root pressure
in the case of the nettle is sufficient to hold a column of water
about 4.5 meters (15 ft.) high (Vines), while the root pressure
of the vine (Hales, 1721) will hold a column of water about 10
meters (36.5 ft.) high, and the birch (Betula lutea) (Clark,
1873) has a root pressure sufficient to hold a column of water
about 25 meters (84.7 ft.) high.
Demonstration 1 7.
91. To demonstrate root pressure. — Use a potted begonia or balsam, the
latter being especially useful. The plants are usually convenient to obtain
from the greenhouses, to illustrate this phenomenon. Cut off rather close to
50
HOW WATER MOVES THROUGH THE PLANT. 51
the soil and attach a long glass tube to the cut end of the stem, still con-
nected with the roots, by the use of rubber tubing as shewn in figure 42. A
very small quantity of water may be poured in to mois-
ten the cut end of the stem. In a few minutes the water
begins to rise in the glass tube. In some cases it rises
quite rapidly, so that the column of water can readily
be seen to extend higher and higher up in the tube
when observed at quite short intervals. The height
cf this column of water is a measure of the force exerted
by the roots. The pressure force of the roots may be
measured also by determining the height to which it
will raise a column of mercury.
Exercise 23.
92. To make records of the experiment. —The pupils
can take notes on the experiment at the time it is set up.
Then for several days let them keep a record of the
height of the liquid in the tube, taken at several times
a day if possible.
93. Variation in root pressure. — In either
case where the experiment is continued for
several days it is noticed that the column of water or of mercury
rises and falls at different times during the same day, that is, the
column stands at varying heights; or in other words the root
pressure varies during the day. With some plants it has been
found that the pressure is greatest at certain times of the day, or at
certain seasons of the year. Such variation of root pressure ex-
hibits what is termed a periodicity, and in the case of some plants
there is a daily periodicity; while in others there is in addition an
annual periodicity. With the grape vine the root pressure is
greatest in the forenoon, and decreases from 12-6 P.M., while
with the sunflower it is greatest before 10 A.M., when it begins to
decrease. Temperature of the soilis one of the most important
external conditions affecting the activity of root pressure.
II. THE Loss OF WATER EY PLANTS (TRANSPIRATION).
94. Wilting of cut shoots. — Wre should now inquire if all the
water which is taken up in excess cf that which actually suffices
Fig. 4«.
Experiment to
show root pressure.
(Detmer.)
52 BOTANY.
for turgidity is used 'in plant growth and in the increase of plant
substance. We notice when a leaf or shoot is cut away from a
plant, unless it is kept in quite a moist condition, or in a damp,
cool place, that it becomes flaccid, and droops. It wilts, as we
say. The leaves and shoot lose their turgidity. This fact suggests
that there has been a loss of water from the shoot or leaf. It can
be readily seen that this loss is not in the form of drops of water
which issue from the cut end of the shoot or petiole. What
then becomes of the water in the cut leaf or shoot ?
Exercise 24.
95. Loss of water from excised leaves. — Take a handful of fresh, green,
rather succulent leaves, which are free from water on the surface, and place
them under a glass bell jar, which is tightly closed below but which contains
Fig. 43- Fig. 44-
Leafy shoots just covered with dry The same after four hours ; mist
bell jar. shows on inside of jar.
Figures 43, 44. — Experiment to show transpiration from leaves on cut shoots.
no water. Place this in a brightly lighted window, or in sunlight. In the
course of fifteen to thirty minutes notice that a thin film of moisture is ac-
cumulating on the inner surface of the glass jar. After an hour or more the
moisture has accumulated so that it appears in the form of small drops of
condensed water. Set up at the same time a bell jar in exactly the same
way but which contains no leaves. In this jar there will be no condensed
moisture on the inner surface. We thus are justified* in concluding that the
moisture in the former jar comes from the leaves. Since there is no visible
HOW WATER MOTES THROUGH THE PLANT. 53
water on the surfaces of the leaves, or at the cut ends, before it may have
condensed there, we infer that the water escapes from the leaves in the form
of water vapor, and that this water vapor, when it comes in contact with tha
Fig. 45- Fig- 46.
Leaves removed to show drops of water Photographed after the water has been
on inside of jar. wiped from inside of jar.
surface of the cold glass, condenses and forms the moisture film, and later
the drops of water. The leaves of these cut shoots therefore lose water in
the form of water vapor, and thus a loss of turgidity results.
Demonstration 1 8.
96. Loss of water from growing plants. — Suppose we now take a small
and actively growing plant in a pot, and cover the pot and the soil with a
sheet of rubber cloth which fits tightly around the stem of the plant (or the
pot and soil may be enclosed in a hermetically sealed vessel) so that
the moisture from the soil cannot escape. Then place a bell jar over the
plant, and set in a brightly lighted place, at a temperature suitable for
growth. In the course of a few minutes on a dry day a moisture film forms
on the inner surface of the glass, just as it did in the case of the glass jar
containing the cut shoots and leaves. Later the moisture has condensed so
that it is in the form of drops. If we have the same leaf surface here as we
had with the cut shoots, we will probably find that a larger amount of
water accumulates on the surface of the jar from the plant that is still at-
tached to its roots.
97. Water escapes from the surfaces of living leaves in the
form of water vapor. — This living plant then has lost water,
which also escapes in the form of water vapor. Since here there
54
BOTANY.
are no cut places on the shoots or leaves, we infer that the loss
of water vapor takes place from the surfaces of the leaves and
from the shoots. It is also to be noted that, while this plant is
losing water from the surfaces of the leaves, it does not wilt or
lose its turgidity. The roots by their activity and osmotic
pressure supply water to take the place of that which is given
off in the form of water vapor. This loss of water in the form
of water vapor by plants is transpiration.
Synopsis.
As a result of the law of diffusion by which water from the
soil is "drawn inside the root hairs forcibly by the cell-
sap, and is passed on through the cells of the root by
the same law of diffusion, a pressure occurs which causes
the liquid plant food to rise to some extent in the roots
and steams of plants.
The height to which water can be lifted by root pressure
varies in different plants.
Root pressure is not constant throughout the day in a
given plant, but varies.
Root pressure is usually lower at night and higher toward
midday.
Plants then show a daily periodicity in the strength of the
root pressure, but the periods are not coincident in all
plants ; that is, the time of day when one plant shows
the greatest root pressure is not necessarily the same for
another plant.
Some plants also show an annual periodicity in the strength
of the root pressure.
Living plants are constantly losing water by evaporation
(or transpiration) from the surface, unless the air is sat-
urated with moisture.
If plants are removed from the soil, or shoots are cut away,
they "wilt," or become flabby, because of the loss of
water.
This loss of water from plants, or plant parts, can be dem-
onstrated by placing the plant under a glass receiver.
The water escapes in the form of invisible water vapor.
When the plant is growing normally? the roots by absorp-
tion of water from the soil supply water to take the
place of that evaporated from the exposed plant surface.
Root pressure
or osmotic
pressure.
Transpiration.
HOW WATER MOVES THROUGH THE PLANT. 55
Material. — For root pressure : One or more potted plants like a begonia,
garden balsam, etc. A long glass tube about the same diameter as that oi
the plant stem ; some rubber tubing to connect the glass with the stem, and
to connect sections of tubing if necessary.
For transpiration : Some succulent leaves and leafy shoots, like gera-
nium, coleus, balsam, etc. Some small glass bell jars. A potted coleus
plant (or balsam), some sheet rubber to cover the pot and earth closely, and
a bell jar to cover the plant
CHAPTER X.
HOW WATER MOVES THROUGH THE PLANT—
CONCLUDED.
III. PART WHICH THE LEAF PLAYS IN TRANSPIRATION.
Demonstration 1 9.
93. Structure of a leaf. — We are now led to inquire why it is that a
living leaf loses water less rapidly than dead ones, and why less water
escapes from a given leaf surface than from an equal surface of water. To
understand this it will be necessary to examine the minute structure of a
leaf. For this purpose we will select the leaf of an ivy, though many other
leaves will answer equally well. From a por-
tion of the leaf we should make very thin
cross-sections with a razor or other sharp in-
strument. These sections should be perpen-
dicular to the surface of the leaf, and should
be then mounted in water for microscopic
examination.*
Let the pupils examine the preparations and
make sketches of the structure of the leaf,
naming the different kinds of cells, and de-
scribing the function of the different groups
of cells. (See paragraphs 99-101.)
99. Epidermis of the leaf. — In this
Fig. 47-
Section through ivy leaf show- section we see that the green part of
ing communication between sto- .
mate and the large intercellular the Jeat IS bordered On what are itS
spaces of the leaf ; stoma closed.
upper and lower surfaces by a row
of cells which possess no green color. The walls of the cells
of each row have nearly parallel sides, and the cross walls are
perpendicular. These cells form a single layer over both sur-
* Demonstrations may be made with prepared sections of leaves.
HOW WATER MOVES THROUGH THE PLANT. 57
Fig. 48. Fig 49.
Stoma open. Stoma closed.
Figures 48, 49.— Section through stomata of ivy leaf.
faces of the leaf and are termed the epidermis. Their walls are
quite stout and the outer walls are cuticularized.
100. Soft tissue of the leaf. — The cells which contain the
green chlorophyll bodies are arranged in two different ways.
Those on the upper side of the leaf are usually long and pris-
matic in form and lie
closely parallel to
each other. Because
of this arrangement
of these cells they are
termed the palisade
cells, and form what
is called the palisade
layer. The other green cells, lying below, vary greatly in size in
different plants and to some extent also in the same plant. Here
we notice that they are elongated, or oval, or somewhat irregular
in form. The most striking peculiarity, however, in their arrange-
ment is that they are not usually packed closely together, but each
cell touches the other adjacent cells only at certain points. This
arrangement of these cells forms quite large spaces between
them, the
intercellular
spaces. If
w e should
examine
such a sec-
tion of a leaf
before it is
mounted in
water we
Fig. 50.
Portion of epidermis of ivy, showing irregular epidermal cells, stoma WOUld S 6 6
and guard cells. , ' .
that the in-
tercellular spaces are not filled with water or cell-sap, but are
filled with air or some gas. Within the cells, on the other
hand, we find the cell-sap and the protoplasm.
58 &OTANV. ^
101. Stomata. — If we examine carefully the row of epidermal
cells on the under surface of the leaf, we will find here and there
a peculiar arrangement of cells shown at figs. 47-49. This
opening through the epidermal layer is a stoma. The cells which
immediately surround the openings are the guard cells. The
form of the guard cells can be better seen if we tear a leaf in
such a way as to strip off a short piece of the lower epidermis,
and mount this in water. The guard cells are nearly crescent
shaped, and the stoma is elliptical in outline. The epidermal
cells are very irregular in outline in this view. We should also
note that while the epidermal cells contain no chlorophyll, the
guard cells do.
102. The living protoplasm retards the evaporation of
water from the leaf. — If we now take into consideration a few
facts which we have learned in a previous chapter, with refer-
ence to the physical properties of the living cell, we will be able
to give a partial explanation of the comparative slowness with
which the water escapes from the leaves. The inner surfaces of
the cell walls are lined with the membrane of protoplasm, and
within this is the cell-sap. These cells have become turgid by
the absorption of the water which has passed up to them from
the roots. While the protoplasmic membrane of the cells does
not readily permit the water to filter through, yet it is saturated
with water, and the elastic cell wall with which it is in contact
is also saturated. From the cell wall the water evaporates into
the intercellular spaces. But the water is given up slowly
through the protoplasmic membrane so that the water vapor
cannot be given off as rapidly from the cell -walls as it could if
the protoplasm were dead. The living protoplasmic membrane
then, which is only slowrly permeable to the water of the cell-
sap, is here a very important factor in checking the too rapid
loss of water from the leaves.
103. Communication through intercellular spaces. — By an
examination of our leaf section we see that the intercellular
HOW WATER MOVES THROUGH THE PLANT. 59
spaces are all connected, and that the stomata, \vhere they
occur, open also into intercellular spaces. There is here an
opportunity for the water vapor in the intercellular spaces to
escape when the stomata are open.
104. Action of the stomata. — Besides permitting the escape
of the water vapor when the stomata are open they serve a very
important office in regulating the amount of transpiration.
During normal transpiration the stomata remain open, that is,
when the amount of transpiration from the leaf is not in excess
of the supply of water to the leaves. But when the transpiration
from the leaves is in excess, as often happens, and the air
becomes very dry, the stomata close, and thus the rapid trans-
piration is checked.
For further discussion of transpiration and root pressure see
the author's larger " Elementary Botany."
Synopsis.
Structure of a leaf
(cross-section).
Epidermis. The epidermal cells usually lack chloro-
phyll.
Upper epidermis, a layer of cells over the upper
surface of the leaf.
Lower epidermis, a layer of cells over the
lower surface of the leaf.
Guard cells of the stomates (openings in the
epidermis) contain chlorophyll.
(Hairs of various kinds on different leaves are
often present: see synopsis of tissues at close
of Chapter XI.)
Mesophyll (the cells of the leaf between the upper
and lower epidermis).
1. Palisade layer of cells, usually next the
upper epidermis. Contains chlorophyll.
2. Loose parenchyma cells, with large inter-
cellular spaces where the air and water
vapor can circulate. Cells contain chloro-
phyll.
(Vascular bundles are present in the "veins" oi
the leaf : see Chapter XI.)
6o
BOTANY.
Function of the leaf
in transpiration.
The living protoplasm retards the evaporation of
water somewhat from the cells.
The water escapes from the cells of the middle part
of the leaf into the intercellular spaces. From
here it passes out through the openings (sto-
mates).
When transpiration is in excess of root pressure,
the guard cells close together and shut the open-
ing, and thus greatly retard the loss of water.
The cuticle, a thin deposit on the outer surface of
the epidermal cells, also retards more or less
transpiration.
Material. — Fresh leaves of some plant like begonia, ivy, or other leaf
which is easy to section. Where preferred, permanently mounted slides of
sections of leaves may be used.
CHAPTER XI.
PATH OF MOVEMENT OF LIQUIDS IN PLANTS.
105. Course of the liquids through the steins. — In our study
of root pressure and transpiration we have seen that large quan-
tities of water or solutions move upward through the stems of
plants. We are now led to inquire through what part of the
stems the liquid passes in this upward movement, or in other
words, what is the path of the " sap " as it rises in the stem.
This we can readily see by the following trial.
Demonstration 2O.
106. To show the tracts through which the liquids rise.— Cut off leafy
shoots of various plants and insert the cut ends in a vessel of water to which
has been added a few crystals of the dye known as fuchsin to make a
deep red color (other red dyes may be used, but this one is especially good).
If the study is made during the summer, the "touch-me-not " (impatiens)
will be found a very useful plant, or the garden balsam, which may also be
had in the winter from conservatories. Almost any plant will do, however,
but we should also select one like the corn plant (Zea mays) if in the
summer.
107. These solutions color the tracts in the stem and leaves
through which they flow. — After a few hours in the case of the
impatiens, or the more tender plants, we can see through the
stem that certain tracts are colored red by the solution, and
after 1 2 to 24 hours there may be seen a red coloration of the
leaves of some of the plants used. After the shoots have been
standing in the solution for a few hours, if we cut them
at various places we shall note that there are several points in
the section where the tissues are colored red. In the impatiens
61
62 BOTANY.
perhaps from four to five, in the sunflower a larger number.
In these plants the colored areas on a cross-section of the stem
are situated in a concentric ring which separates more or less
completely an outer ring of the stem from the central portion.
If we now split portions of the stem lengthwise we see that these
colored areas continue throughout the length of the stem, in
some cases even up to the leaves and into them.
108. Arrangement of the tracts in the corn stalk.— If we
cut across the stem of a corn plant which has been in the solu-
Fig. 51.
Bioken corn stalk, showing fibro-vascular bundles.
tion, we see that instead of the colored areas being in a con-
centric ring they are irregularly scattered, and on splitting the
stem we see here also that these colored areas extend for long
distances through the stem.
Exercise 25.
109. To demonstrate the tracts in stems and petioles. — Take leaves of a
calla lily, or of a caladium, which grow in conservatories, and good leaves
of stored celery, with long petioles. Other leafy shoots which are more
accessible may be used, if desired. Place the ends of the petioles, or the
shoots, in a solution of fuchsin, or in red ink. in the course of an hour (they
may be left in a longer time if necessary) observe the petioles and leaves.
Can any of the color be seen without cutting into the stem ? (Where the
PART OF MOVEMENT OF LIQUIDS IN PLANTS. 63
shoots remain in the colored liquid for a day, or even for a less time, portions
of the leaves will show the color.) Cut across the stems, and describe the
location of the colored areas. Split the petioles or stems and trace the colored
tracts. Compare their location in the calla and the celery petiole.
110. To observe the texture of these areas in a celery petiole. — Take fresh
but rather old celery leaves (from stored celery if in the winter). Break the
petiole apart. Is the broken part ragged ? Is there any difference in the
texture or toughness of the petiole shown by any portions " stringing " out?
Describe the location of these strands. What are they ? Have they any re-
lation to the colored areas or tracts in the petiole which was in the red ink?
Break apart in a similar way a petiole which has been in the red ink
Compare. The celery represents a dicotyledenous plant.
111. The strands in a dead corn stalk.— Take a dead corn stalk (they are
easily obtained in the autumn or winter from the fields). Cut through the
outer harder portion of the stem. Break it. Compare carefully with the
broken celery petiole. The corn stem represents a monocoty ledonous plant.
112. There are definite courses through which the liquids
rise. — We thus see that instead of the liquids passing through
the entire stem they are confined to definite courses. Now that
we have discovered the path of the upward movement of water
in the stem, we are curious to see what the structure of these
definite portions of the stem is.
Demonstration 21.
113. Structure of the fibrovascular bundle. — Make quite thin cross-sec-
tions of the stem it is desired to study, and mount in water for microscopic
examination. Permanent mounts may be made in Canada balsam by those
who understand the method. Or mounted preparations may be obtained,
which will preserve for future use. Let each pupil examine cross and longi-
tudinal sections of a dicotyledon and of a monocotyledon, making out
clearly the different groups of tissues, and the kinds of cells composing them.
Paragraphs 114-123 may.be used as a guide. The description is here made
from the castor-oil bean, and the illustration from the sunflower to represent
the dicotyledon, while the corn stem is used to illustrate the monocotyledon.
It will be no disadvantage for the teacher to use other plants than those em-
ployed here for the demonstration.
114. The bundles in a dicotyledon. — To illustrate the structure of the
bundle in one type we may take the stem of the castor-oil bean. On examin-
ing these cross-sections we see that there are groups of cells which are denser
than the ground tissue. These groups correspond to the colored areas in the
former experiments, and are the vascular bundles cut across. These groups
64 BOTANY.
are somewhat oval in outline, with the pointed end directed toward the centre
of the stem. If we look at the section as a whole we see that there is a nar-
Fig. 52.
Xylem portion of bundle. Cambium portion of bundle. Bast portion of bundle.
Section of vascular bundle of sunflower stem.
row continuous ring * of small cells situated at the same distance from the
centre of the stem as the middle part of the bundles, and that it divides the
bundles into two groups of cells.
115. Woody portion of the bundle. — In that portion of the bundle on the
inside of the ring, i.e., toward the "pith," we note large, circular, or angu-
lar cavities. The walls of these cells are quite thick and woody. They are
therefore called wood cells, and because they are continuous with cells above
and below them in the stem in such a way that long tubes are formed, they
are called woody vessels. Mixed in with these are smaller cells, some of
which also have thick walls and are wood cells. Some of these cells may
have thin walls. This is the case with all when they are young, and they
are then classed with the fundamental tissue or soft tissue (parenchyma).
This part of the bundle, since it contains woody vessels and fibres, is the
wood portion of the bundle, or technically the xylem.
* This ring and the bundles separate the stem into two regions, an outer
one composed of large cells with thin walls, known as the cortical cells, or
collectively the cortex. The inner portion, corresponding to what is called
the pith, is made up of the same kind of cells and is called the medulla, or
Pith. When the cells of the cortex, as well as of the pith, remain thin-walled
the tissue is called parenchyma. Parenchyma belongs to the group of tis-
sues called fundamental.
PART OF MOVEMENT OF LIQUIDS IN PLANTS. 6$
116. Bast portion of the bundle. — If our section is through a part of the
stem which is not too young, the tissues of the outer part of the bundle will
show either one or several groups of cells which have white and shiny walls,
that are thickened as much or more than those of the wood vessels. These
cells are bast cells, and for this reason this part of the bundle is the bast
portion, or the phloem. Intermingled with these, cells may oiten be found
which have thin walls, unless the bundle is very old. Nearer the centre of
the bundle and still within the bast portion are cells with thin walls, angular
and irregularly arranged. This is the softer portion of the bast, and some
of these cells are what are called sieve tubes, which can be better seen and
studied in a longitudinal section of the stem.
117. Cambium region of the bundle. — Extending across the centre of
the bundle are several rows of small cells, the smallest of the bundle, and we
can see that they are more regularly arranged, usually in quite regular
rows, like bricks piled upon one another. These cells have thinner walls
than any others of the bundle, and they usually take a deeper stain when
treated with a solution of some of the dyes. This is because they are younger,
and are therefore richer in protoplasmic contents. This zone of young cells
across the bundle is the cambium. Its cells grow and divide, and thus in-
crease the size of the bundle. By this increase in the number of the cells of
the cambium layer, the outermost cells on either side are continually passing
over into the phloem, on the one hand, and into the wood portion of the
bundle, on the other hand.
118. Longitudinal section of the bundle. — If we make thin longisections
of the vascular bundle of the castor-oil seedling (or other dicotyledon) so
that we have thin ones running through a bundle radially, as shown in fig.
53, we can see the structure of these parts of the bundle in side view. We
see here that the form of the cells is very different from what is presented in
a cross-section of the same. The walls of the various ducts have peculiar
markings on them. These markings are caused by the walls being thicker
in some places than in others, and this thickening takes place so regularly in
some instances as to form regular spiral thickenings. Others have the thick-
enings in the form of the rounds of a ladder, while still others have pitted
walls or the thickenings are in the form of rings.
119. Vessels or ducts. — One way in which the cells in side view differ
greatly from an end view, in a cross-section in the bundle, is that they are
much longer in the direction of the axis of the stem. The cells have become
elongated greatly. If we search for the place where two of these large cells
with spiral, or ladder-like, markings meet end to end, we shall see that the
wall which formerly separated the cells has nearly or quite disappeared. In
other words the two cells have now an open communication at the ends.
This is so for long distances in the stem, so that long columns of these large
66
BOTANY.
cells form tubes or vessels through which the water rises in the steins of
plants.
120. Bast fibres.— In the bast portion of the bundle we detect the cells of
the bast fibres by their thick walls. They are very much elongated and the
i
I!
Longitudinal section of vascular bundle of sunflower stem; spiral, scalariform and pitted
vessels at left; next are wood fibers with oblique cross walls; in middle are cambium cells
with straight cross walls, next two sieve tubes, then phloem or bast cells.
ends taper out to thin points so that they overlap. In this way they serve to
strengthen the stem.
121. Sieve tubes.— Lying near the bast cells, usually toward the cambium,
are elongated cells standing end to end, with delicate markings on their cross-
walls which appear like finely punctured plates or sieves. The protoplasm
in such cells is usually quite distinct, and sometimes contracted away from
the side walls, but attached to the cross- walls, and this aids in the detection
of the sieve tubes (fig. 53). The granular appearance which these plates
present is caused by minute perforations through the wall so that there
is a communication between the cells. The tubes thus formed are there-
fore called sieve tubes, and they extend for long distances through the
bundle so that there is communication throughout the entire length of the
stem. (The function of the sieve tubes is supposed to be that for the down-
ward transportation of substances elaborated in the leaves.)
122. Bundle in the sunflower stem. — In like manner a section of the stem
of the sunflower shows similar bundles, but the number is greater than eight.
In the garden balsam the number is from four to six in an ordinary stem
3~4ww diameter. Here we can see quite well the origin of the vascular
bundle. Between the larger bundles especially in free-hand sections of stems
PART OF MOVEMENT OF LIQUIDS IN PLANTS. 6?
through which a colored solution has been lifted by transpiration, we can
see small groups of the minute cells in the cambial ring which are col-
ored. These groups of cells which form strands running through the stem are
procambium strands. The cells divide and increase just like the cambium
cells, and the older ones thrown off on either side change, those toward the
centre of the stem to wood vessels and fibres, and those on the outer side to
bast cells and sieve tubes.
123. Fibrovascular bundles in the Indian corn. — In fig. 54 is repre-
sented a fibrovascular bundle of the stem of the Indian corn. The large
cells are those of the spiral and reticulated
and annular vessels. This is the woody
portion of the bundle, or xylem. Oppo-
site this is the bast portion or phloem,
marked by the lighter colored tissue at i.
The larger of these cells are the sieve
tubes, and intermingled with them are
smaller cells with thin walls. Surround-
ing the entire bundle are small cells with
thick walls. These are elongated and the
tapering ends overlap. They are thus
slender and long and form fibres. In
such a bundle all of the cambium has
passed over into permanent tissue and the
bundle is said to be closed.
124. Rise of water in the vessels. —
During the movement of the water or
nutrient solutions upward in the stem the
vessels of the wood portion of the bundle
Fig. 54-
Transaction of fibrovascular bundle of
Indian corn. «, toward periphery of
stem ; g-, large pitted vessels ; s, spiral
vessel ; r, annular vessel ; /, air cavity
formed by breaking apart of the cells ;
/". soft bast, a form of sieve tissue ; /,
in certain plants are nearly or quite filled, thin- walled parenchyma. (Sachs.)
if root pressure is active and transpiration is not very rapid. If, however, on
dry days transpiration is in excess of root pressure, as often happens, the
vessels are not filled with the water, but are partly filled with certain gases
because the air or other gases in the plant become rarefied as a result of the
excessive loss of water. There are then successive rows of air or gas bub-
bles in the vessels separated by films of water which also line the walls of
the vessels. The condition of the vessel is much like that of a glass tube
through which one might pass the " froth" which is formed on the surface
of soapy water. This forms a chain of bubbles in the vessels. This chain
has been called Jamin's chain because of the discoverer.
125. Rise of water in the bundles is not we' 1 understood. — Why water or
food solutions can be raised by the plant to the height attained by some trees
has never been satisfactorily explained. There are several theories pro-
68
BOTANY.
pounded which cannot be discussed here. It is probably a very complex
process. Root pressure and transpiration both play a part, or at least can be
shown, as we have seen, to be capable of lifting water to a considerable height.
126. Synopsis of tissues.
Epidermis.
Epidermal
system.
Fibrovascular
system.
Fundamental
system.
Trichomes
(hairs).
Xylem.
f Simple hairs.
Many-celled hairs.
Branched hairs, often stellate.
Clustered, tufted hairs.
Glandular hairs.
I Root hairs.
Guard cells of stomates.
Spiral vessels.
Pitted vessels.
Scalariform vessels.
Annular vessels.
Wood fibres.
- Wood parenchyma.
Cambium (fascicular).
f Sieve tubes.
Phloem. \ Bast fibres.
[ Bast parenchyma.
Cork.
Parenchyma.
Ground tissue.
Interfascicular cambium.
Medullary rays.
Bundle sheath.
Sclerenchyma (thick-walled cells, in nuts, etc.). Collen-
chyma (thick-angled cells, under epidermis of succulent
stems).
Demonstration 22.*
127. If it is desired that the pupils examine under the microscope the dif-
ferent elements of the epidermal and fundamental system, the teacher can
make or procure sections to illustrate them. The pupils can then study and
make sketches to illustrate the structures.
Material. — Leaves of stored celery, the older ones with rather tough
petioles, and considerable leaf surface; or caladium leaves with long petiole
This demonstration may well be omitted-
PART OF MOVEMENT OF LIQUIDS IN PLANTS. 69
from the conservatory; old dead corn-stalks. Shoots of the garden balsam
(impatiens) are good.
A solution of fuchsin (add a few crystals to water), or use red ink. -
For study of the vascular bundles, sections may be made of the stems or
petioles of the same plants, or of fresh corn stalks, of the stem of the sun-
flower, or castor-oil bean. The teacher can make these sections either free
hand, or with a microtome; or if preferred, permanent slides to illustrate
the structure of the vascular bundles may be obtained.
If the pupils are to make their own sections for study, sharp razors will
also be required.
Microscope, etc., for demonstration 21.
CHAPTER XII.
HOW PLANTS GET THEIR CARBON FOOD.
I. THE GASES CONCERNED.
Exercise 26.
128. Gas given off by green plants in the sunlight. — Take some green
alga, like spirogyra or vaucheria, which is in a fresh condition, place one
lot in a beaker or tall glass vessel of water and
set this in the direct sunlight or in a well lighted
place. At the same time cover a similar vessel
of spirogyra with black cloth so that it will be
in the dark, or at least in very, weak light.
129. The gas is shown in the form of bab-
bles.— In a short time we that in the first
vessel small bubbles of gas are accumulating on
the surface of the threads of the spirogyra, and
now and then some free themselves and rise to
the surface of the water. Where there is quite
a tangle of- the threads the gas is apt to become
caught and held back in larger bubbles, which
on agitation of the vessel are freed.
Examine the vessel which was covered to
exclude the light, or which was placed in the
dark. Are bubbles of gas given off here?
Place the vessel in the light and note how soon
bubbles begin to pass off.
Fig. 55-
Oxygen gas given off by
spirogyra.
Exercise 27.
130. Experiment with elodea. — Take one of the higher green plants, an
aquatic plant like elodea, callitriche, etc. Place the plant in the water with
the cut end of the stem uppermost, but still immersed, the plant being weighed
down by a glass rod or other suitable object. If we place the vessel of water
70
HOW PLANTS GET THEIR CARBON FOOD. ?I
containing these leafy stems in the bright sunlight, in a short time bubbles
of gas will pass off quite rapidly from the cut end of the stem.
In the stem from which the leaves have been cut are there as many bub-
bles ? What is the reason ? What part of the leafy shoot gives rise to the
greater part of the gas ?
Demonstration 23.
131. To determine the kind of gas given off by green plants in the sun-
light.— Take quite a quantity of the plants of elodea and place them under
an inverted funnel which is immersed in water: the gas will be given off in
quite large quantities and will rise into the narrow exit of the funnel. The
funnel should be one with a short
tube, or the vessel one which is
quite deep so that a small test
tube which is filled with water
may in this condition be inverted
over the opening of the funnel
tube. Place in the bright sun-
light for several days.
With this arrangement of the
experiment the gas will rise in
the inverted test tube, slowly
displace a portion of the water,
and become collected in a suffi-
cient quantity to afford us a
test. When a considerable
quantity has accumulated in the test tube, we may close the end of the tube in
the water with the thumb, lift it from the water and invert. The gas will rise
against the thumb. A dry soft pine splinter should be then lighted, and after
it has burned a short time, extinguish the flame by blowing upon it, when
the still burning end of the splinter should be brought into the mouth of the
tube as the thumb is quickly moved to one side. The glowing of the splinter
shows that the gas is oxygen.
132. Oxygen given off by green land plants also. — If we should extend
our experiments to land plants we should find that oxygen is given off by
them under these conditions of light. Land plants, however, will not do this
when they are immersed in water, but it is necessary to set up rather com-
plicated apparatus and to make analyses of the gases at the beginning and
at the close of the experiments. This has been done, however, in a suffi-
ciently large number of cases so that we know that all gree», plants in the
sunlight,- if temperature and other conditions are favorable, give off oxygen.
Fig. 56.
Bubbles of oxygen
given off from elodea in
presence of sunlight. (Oels )
gas
Fig. 57-
Apparatus for col-
lecting quantity of
oxygen from elodea.
(Detmer.)
72 BOTANY.
133, Absorption of carbon dioxide. — We have next to
inquire where the oxygen comes from which is given off by
green plants when exposed to the sunlight, and also to learn
something more of the conditions necessary for the process.
We know that water which has been for some time exposed to
the air and soil, and has been agitated, like running water of
streams, or the water of springs, has mixed with it a consider-
able quantity of oxygen and carbon dioxide.
Demonstration 24.
134. To show the result in boiled water. — Boil spring water or hydrant
water which comes from a stream containing oxygen and carbon dioxide, for
about 20 minutes, to drive off these gases. Set this aside where it will not
be agitated, until it has cooled sufficiently to receive plants without injury.
Now place some spirogyra or vaucheria, and elodea, or otjier green water
plant, in this boiled water and set the vessel in the bright sunlight under the
same conditions which were employed in the experiments for the evolution of
oxygen. No oxygen is given off.
NOTE. — It can be demonstrated that carbon dioxide is absorbed by the
plant while the oxygen is passing off. In the case of aquatic plants the
carbon dioxide is mixed with the water, while in the case of the land plants
the carbon dioxide comes from the air. In the study of respiration we shall
find that carbon dioxide is formed within the plant. Some of the carbon
dioxide then which plants use when they are giving off oxygen comes from
within the plant itself. For some simple experiments to demonstrate the
absorption of carbon dioxide during this process see paragraphs 119-124 of
the author's larger "Elementary Botany."
135. A chemical change of the gas takes place within the
plant cell. — Since oxygen is given off while carbon dioxide, a
different gas, is necessary, it would seem that a chemical change
takes place in the gases within the plant. Since the process
takes place in such simple plants as spirogyra as well as in the
more bulky and higher plants, it appears that the changes go on
within the cell, in fact within the protoplasm. We should
remember also that this chemical change of the gases in plants
Can only take place in the presence of light.
HOW PLANTS GET THEIR CARBON fOOD.
73
Synopsis. — At temperatures suitable for growth, green plants in the sun-
light are constantly giving off a gas.
In the case of water plants this gas can be seen in the form of bubbles.
This gas is oxygen.
At the same time that oxygen is being given off by green plants carbon
dioxide (carbon and oxygen) is being absorbed by the plant.
A chemical change in the carbon dioxide takes place in the plant and
some of the oxygen is thus liberated.
Material. — Fresh mats of some alga, either spirogyra, zygnema, or vau-
cheria.
Fresh shoots of one of the higher water plants like elodea (found in the
shallow water of ponds, lakes, or streams near low ground).
Beakers with fresh spring or hydrant water to hold the plants. A funnel
and large test tube for demonstration 23. The demonstration should be
started several days in advance.
CHAPTER XIII.
HOW PLANTS GET THEIR CARBON FOOD.
CONCLUDED.
II. STARCH FORMED BY GREEN PLANTS.
Exercise 28.
136. To test for the presence of starch in green^ leaves. — Take green
leaves which have been for several hours in the bright sunlight. Boil them
in alcohol, using great care not to set the alcohol on fire. This removes the
chlorophyll. If it is desired not to use the alcohol, boil the leaves in water
for a short time. Then place them in alcohol, changing the alcohol occa-
sionally. The green color is extracted slowly by this process, It may be
extracted more rapidly if the preparation is placed in the sunlight. When
the leaves are decolorized, place them in a solution of iodine in potassium
iodide. In place of this solution, a tincture of iodine purchased at drug-
stores answers fairly well. Observe the color of the leaves. This color is
due to the presence of starch, the starch becoming dark blue or nearly
black when treated with iodine.
137. Starch is formed only in the green parts of variegated
leaves. — If we test for starch in variegated leaves like the leaf
of a coleus plant, we shall have an interesting demonstration of
the fact that the green parts of plants only form starch. We
may take a leaf which is partly green and partly white, from a
plant which has been standing for some time in bright light.
Fig. 58 is from a photograph of such a leaf. We should first
boil it in alcohol to remove the green color. Now immerse it
in the potassium iodide of iodine solution for a short time.
The parts which were formerly green are now dark blue or
nearly black, showing the presence of starch in those portions
74
HOW PLANTS GET THEIR CARBON FOOD. 75
of the leaf, while the white part of the leaf is still uncolored.
This is well shown in fig. 59, which is from a photograph of
another coleus leaf treated with the iodine solution.
138, Green parts of plants form starch when exposed to
light. — Thus we find that in the case of all the green plants we
Fig. 58- Fig. 59.
Leaf of coleus showing green and white Similar leaf treated with iodine, the starch re-
areas, before treatment with iodine. action only showing where the leaf was green.
have examined, starch is present in the green cells of those
which have been standing for some time in the sunlight where
the process of the absorption of CO., and the giving off of oxygen
can go on, and that in the case of plants grown in the dark,
or in leaves of plants which have stood for some time in the
dark, starch is absent. We reason from this that starch is the
product of the chemical change which takes place in the green
cells under these conditions. Because COa is absorbed during
this process, and because of the chemical changes which take
place in the formation of starch, by means of which the carbon
76 BOTANY.
is changed from its attraction in the molecule of carbon dioxide
to its attraction in the molecule of starch, the process has
been termed carbon assimilation. But since it is not truly an
assimilatory process, and because sunlight is necessary in the
first step of the conversion, it has also been recently termed
pKotosyntax or photosynthesis. These terms, however, seem in-
appropriate, since the synthetic part of the process is not known
to be due to the action of light. In the presence of chlorophyll
light reduces the carbon dioxide, while the synthetic part of the
process may not be influenced by light. For popular treatment
the term carbon conversion was proposed in the author's larger
" Elementary Botany." But this is also an unfortunate term,
and he would now propose the simple .term, starch formation.
But there should be no objection to the use of the term carbon
assimilation, or photosynthesis.
139. Fungi cannot form starch. — If we should extend our
experiments to the fungi, which lack the green color so charac-
teristic of the majority of plants, we should find that starch
formation does not take place even though the plants are
exposed to direct sunlight. These plants then obtain carbo-
hydrates for food from other sources, as parasites from living
plants, and as saprophytes from dead olants, or from certain
plant products.
III. CHLOROPHYLL AND CHLOROPHYLL BODIES.
140. Form of the chlorophyll bodies. — This green substance
of plants, the presence of which is necessary in the formation
of starch, is chlorophyll. It usually occurs in definite bodies,
the chlorophyll bodies. Chlorophyll bodies vary in form in
some different plants, especially in some of the low^r plants.
This we have already seen in the case of spirogyra, where the
chlorophyll body is in the form of a very irregular band, which
courses around the inner side of the cell wall in a spiral manner.
In zygnema, which is related to spirogyra, the chlorophyll
bodies are star-shaped. In the desmids the form varies greatly.
HOW PLANTS GET THEIR CARBON FOOD. TJ
In vaucheria, a branched thread-like alga, the chlorophyll bodies
are oval in outline. This form of the chlorophyll body is that
which is common to many of the green algae, and also occurs
in the mosses, liverworts, ferns, and the higher plants. It is a
more or less rounded, oval, flattened body.
Demonstration 25.
141. Chlorophyll bodies in leaves.— If it is desired to demonstrate the
chlorophyll bodies the teacher can make free-hand sections from fresh leaves
of a begonia, or from some other plant. In figure 60 are shown the chloro-
phyll bodies in the leaf of the ivy.
Fig. 60.
Section of ivy leaf, palisade cells above, loose parenchyma, with large intercellular spaces
in centre. Epidermal cells on either edge, with no chlorophyll bodies.
142. Chlorophyll. — The chlorophyll is a coloring substance
which resides in the chlorophyll body. It can be extracted from
the body by the use of alcohol. The body is a plastid of a
proteid nature, widely distributed in many plants. . The^nlasticl
when not exposed to light is usually colorless, when exposed to
light it often becomes green ; while in the roots of the carrot
and in the petals of some flowers it possesses other colors.
When it is colorless it is called a leucoplast, when green a
chloroplast, and when yellow, red, etc., a chromoplast.
143. Where starch is first formed. — The starch is first
formed in the chlorophyll bodies. The chlorophyll absorbs
78 BOTANY.
certain of the rays of light. The absorbed light is transformed
into energy which assists in the chemical changes taking place
in the carbonic acid (when the carbon dioxide of the air meets
the water in the cell it forms carbonic acid) in the cell by which
starch is built up. By mounting leaves of some mosses, or the
prothallia of ferns in water, for microscopic examination, the
starch grains can be seen within the chlorophyll bodies. They
can often be seen in the chlorophyll bodies in the leaf of
begonias when thin sections are made for observation under the
microscope.
144. Starch in other parts of plants than the leaves. —
While the larger part of the starch is formed in the green leaves,
it is often found stored in large quantities in parts of plants not
exposed to the light. It is formed in the leaves during the day,
and at night it is dissolved and transported to other parts of the
plant where it may be needed for the manufacture of other
substances used in plant growth, or it may be stored in special
receptacles in the form of starch grains again, as in the potato
tuber, the roots of the sweet potato, or in the thick leaves of
the onion, etc.
Exercise 29.
145. To test for the presence of starch in parts of the plant where it
is stored. — Cut a potato tuber, scrape some of the potato at the cut surface
into a pulp. Apply a small quantity of a solution of iodine to this pulp.
Describe the result. The color produced is the reaction for what substance ?
Where was the starch first formed in the potato plant ? How is it that later
it is found in the tubers which are underground stems ? What function for
tLe.. potato plant does this stored starch serve ?
If ilfTs^x- VM the pupils may test for starch in the enlarged roots of the
sweet potato, the grains of corn, or in the leaves of the onion.
Place a small quantity of corn starch (as much as will be lifted on the
point of a small knife blade) in a test tube. Add water to the depth of two
inches and warm over a flame, then cool by moving the end in cold water or
by holding it under the water tap. Add to the starch water a drop or two
of a tincture of iodine (iodine crystals dissolved in alcohol). Observe the
blue color. Now heat over the flame; the color disappears because the
warm water extracts the iodine from the starch grains. Now cool again.
The blue color reappears since the starch again takes up the iodine.
HOW PLANTS GET THEIR CARBON FOOD. ?9
Demonstration 26.
146. Form of starch grains. — Where starch is stored as a reserve mate-
rial it occurs in grains which usually have certain characters peculiar to the
species of plant in which they are found. They vary in size in many dif-
ferent plants, and to some extent in form also. Scrape some of the cut sur-
face of the potato tuber into a pulp and mount a small quantity in water, or
make a thin section for microscopic examination. We find large starch grains
of a beautiful structure. The grains are oval in form and more or less irregular
in outline. But the striking peculiarity is the presence of what seem to be
alternating dark and light lines in the starch grain. The lines form irregu-
lar rings, which are smaller and smaller until we come to the small central
spot termed the " hilum " of the starch grain. It is supposed that these ap-
parent lines in the starch grain are caused by the starch substance being
deposited in alternating dense and dilute layers, the dilute layers containing
more water than the dense ones ; others think that the successive layers
from the hilum outward are regularly of diminishing density, and that this
gives the appearance of alternating lines.
147. Necessity of carbon food for plants. — The starch
formed by plants is one of the organic substances manufactured
by plants. It is the basis for the formation of other organic sub-
stances. Starch contains carbon, hydrogen, and oxygen, in the
proportion of 6 molecules of carbon, 10 molecules of hydrogen,
and 5 molecules of oxygen (C8H10O5). The water in the starch
is in the proportion of 2 molecules of hydrogen to i molecule
of oxygen (H2O). For this reason it is called a carbohydrate.
The most important carbohydrates in plants are starch, the
sugars, and cellulose, the latter substance, or modifications of
it, forming the cell walls of plants. Without carbon-food
green plants cannot make any appreciable increase in plant
substance, though a considerable increase in size of the plant
may take place (see paragraph 194). Chlorophylless plants, like
the fungi and certain parasitic or saprophytic (as the Indian-
pipe, certain of the orchids, etc.) angiosperms, derive their
carbon-food from the carbohydrates manufactured by the green
plants. Animals also derive their carbohydrates through the
medium of the green plants, either directly or indirectly.
NOTE. — For further experiments and discussion of this subject see the
author's larger "Elementary Botany."
8o
BOTANY.
Starch formation, by
green plants.
Synopsis.
Carbon dioxide is absorbed by the green parts of
plants.
In the presence of chlorophyll in the cell, and under
the influence of sunlight, a chemical change takes
place in the carbonic acid (carbon dioxide united
with the water in the plant-cell).
As a result of this chemical change starch is formed
by the union of carbon, hydrogen, and oxygen ;
but all of the oxygen brought in by the carbon
dioxide is not needed in the manufacture of starch.
This portion of the oxygen is set free.
Fungi, or other plants which lack chlorophyll cannot form starch.
Parts of leaves, or parts of plants, which lack chlorophyll cannot form
starch.
Chlorophyll is the green pigment in the chlorophyll bodies (chloroplasts).
Starch is first formed in the chlorophyll bodies, and then dissolved and
carried to other parts of the plant, for food, or to be stored.
Material. — Fresh leaves of ordinary plants which have been for a few
hours in daylight (some of the seedlings which have been grown, or plants
from the greenhouse will answer); some variegated leaves of the coleus
plant if possible.
For study of chlorophyll, leaves of begonia to section are good. For
study of starch, potato tubers ; and if other objects are wanted, sweet pota-
toes, onions, etc.
If the pupils make their own sections of the begonia leaves, sharp razors
will be necessary.
Chemicals needed in the test for starch : a solution of iodine in potassium
iodide (see appendix for formula), or an ordinary tincture of iodine ob-
tained at drugstores ; alcohol.
Microscope, etc., if it is desired to demonstrate the structure of starch
grain.
CHAPTER XIV.
ROUGH ANALYSIS OF PLANT SUBSTANCE.
148. Some simple experiments to indicate the nature of
plant substance. — After these building-up processes of the plant,
it is instructive to perform some simple experiments which indi-
cate roughly the nature of the plant substance, and serve to
show how it can be separated into other substances, some of them
being reduced to the form in which they existed when the plant
took them as food. For exact experiments and results it would
be necessary to make chemical analyses.
Exercise 3O.
149. The water in the plant. — Take fresh leaves or leafy shoots or other
fresh plant parts. Weigh. Permit them to remain in a dry room until they
are what we call "dry." Now weigh. The plants have lost weight, and
from what we have learned in studies of transpiration this loss in weight we
know to result from the loss of water from the plant.
Exercise 31 .
150. The dry plant material contains water. — Take dry leaves, shavings,
or other dry parts of plants. Place them in a test-tube. With a holder rest
the tube in a nearly horizontal position, wi.th the bottom of the tube in the flame
of a bunsen burner. Very soon, before the plant parts begin to "burn,"
note that moisture is accumulating on the inner surface of the test-tube.
This is water driven cff which could not escape by drying in air, without the
addition of artificial heat, and is called " hygroscopic water."
151. Water formed on burning the dry plant material. — Light a soft-pine
or bass-wood splinter. Hold a thistle tube in one hand with the bulb down-
ward and above the flame of the splinter. Carbon will be deposited over tin-
inner surface of the bulb. After a time hold the tube toward the window
and look through it above the carbon. Drops of water have accumulated on
Si
82 BOTANY.
on the inside of the tube. This water is formed by the rearrangement of
some of the hydrogen and oxygen, which is set free by the burning of the
plant material, where they were combined with carbon, as in the cellulose,
and with other elements.
Exercise 32.
152. Formation of charcoal by burning. — Take dried leaves, and shav-
ings from some soft wood. Place in a porcelain crucible, and cover about
•^ctn deep with dry fine earth. Place the crucible in the flame of a Bunsen
burner and let it remain for about 15 minutes. Remove and empty the con-
tents. If the flame was hot the plant material will be reduced to a good
quality of charcoal. The charcoal consists largely of carbon.
153. The ash of the plant. — Place in the porcelain crucible dried leaves
and shavings as before. Do not cover with earth. Place the crucible in the
flame of the Bunsen burner, and for a moment place on the porcelain cover ;
then remove the cover, and note the moisture on the under surface from the
escaping water. Permit the plant material to burn ; it may even flame for
a time. In the course of 15 minutes it is reduced to a whitish powder,
much smaller in bulk than the charcoal in the former experiment. This is
the ash of the plant.
What has become of the carbon ? In this experiment the air was not ex-
cluded from the plant material, so that oxygen combined with the carbon as
the water was freed, and formed carbon dioxide, passing off into the air in
this form. This it will be remembered is the form in which the plant took
the carbon-food in through the leaves. Here the carbon dioxide met the
water coming from the soil, and the two united to form, ultimately, starch,
cellulose, and other compounds of carbon ; while with the addition of nitro-
gen, sulphur, etc., coming also from the soil, still other plant substances
were formed.
NOTE. — The ash of the plant contains, usually, potash, soda, lime, mag-
nesium, ferric oxide, phosphoric acid, sulphuric acid, silica, chlorine. (See
page 64 of the author's larger " Elementary Botany," 2d Ed., revised.)
Synopsis.
The living plant contains a large amount of water.
When the plant is dried in the air it still contains a considerable amount
of water.
This water of air-dried plants can only be driven off by artificial heat (at
a temperature of 100° F. for some time).
When all of the water is dried out of the plant, if the plant is burned so
that the plant substance is disorganized, several different substances
are formed.
ROUGH ANALYSIS OF PLANT SUBSTANCE. 83
1. Water is formed by the uniting of hydrogen and oxygen as these
elements are freed from the plant substance by the burning.
2. Certain gases, one of them is carbon dioxide, formed by the carbon
from the disorganized plant substance uniting with oxygen of
the air during the burning.
If the dried plant material is burned while oxygen from the air is ex-
cluded, the carbon cannot unite with oxygen to form carbon dioxide,
but remains in the form of charcoal, which is almost pure carbon.
\Vhen plant material is burned with access of oxygen the residuum is a
whitish-gray powder called the ash. (See page 64 of the author's
larger "Elementary Botany," 2d Ed., revised.)
Material. — Leafy shoots fresh; air-dried leaves, and some soft dry wood
(white pine wood, bass wood, or some similar soft wood).
Apparatus. — Bunsen burner to supply gas-flame ; small porcelain cruci-
bles with covers; supports to hold crucibles in the flame; test tubes; thistle
Vibes; some dry earth.
CHAPTER XV.
SOME OTHER WAYS IN WHICH CERTAIN PLANTS
OBTAIN FOOD.
(This chapter is for reading, or the teacher may make demon-
strations before the class if there is time.)
154. Nutrition of moulds.-^Start some growths of the black
mould as described in paragraph 49. Then for several days
observe the growth. First there appear small spots of delicate
white threads. This tuft of threads increases in size, the threads
elongate and branch. Finally upright threads appear which
bear the black heads (sporangia, sing, sporangium) and spores
again. Break the potatoes open through several of these tufts.
The threads of the mould enter the potato also. The mycelium
in the potato or in the bread absorbs food solutions from these
substances in the same way that root hairs absorb food solu-
tions. The potato and the bread are largely made up of starch
from green plants. This demonstration serves excellently to
show how the fungi which lack chlorophyll obtain their carbo-
hydrate food from the products of green plants (see paragraph
147).
155. Nutrition of the larger fungi. — If we select some one
of the larger fungi, the majority of which belong to the mush-
room family and its relatives, which is growing on a decaying
log or in the soil, we shall see on tearing open the log, or on
removing the bark or part of the soil, as the case may be, that
the stem of the plant, if it have one, is connected with whitish
strands. During the spring, summer, or autumn months,
examples of the mushrooms connected with- these strands may
usually be found readily in the fields or woods, but during the
84
HOW PLANTS OBTAIN FOOD, 8$
winter and colder parts of the year often they may be seen in
forcing houses, especially those cellars devoted to the propaga-
tion of the mushroom of commerce.
156. The fungus strands. — These strands are made up ol
numerous threads of the mycelium which are closely twisted
and interwoven into a cord or strand, which is called a myce-
Uum strand, or rhizomorph. These are well shown in fig. 61,
which is from a photograph of the mycelium strands, or
"spawn" as the grower of mushrooms calls it, of Agaricus
campestris. The little knobs or enlargements on the strands
are the young fruit bodies, or " buttons."
157. Mats of mycelium are sometimes very extensive.—
While these threads or strands of the mycelium in the decaying
wood or in the decaying organic matter of the soil are not true
roots, they function as roots, or root hairs, in the absorption of
food materials. In old cellars and on damp soil in moist
places we sometimes see fine examples of this vegetative
part of the fungi, the mycelium. But most magnificent
examples are to be seen in abandoned mines where timber has
been taken down into the tunnels far below the surface of the
ground to support the rock roof above the mining operations.
I have visited some of the coal mines at Wilkesbarre, Pa., and
here on the wood props and doors, several hundred feet below
the surface, and in blackest darkness, in an atmosphere almost
completely saturated at all times, the mycelium of some of the
wood-destroying fungi grows in a profusion and magnificence
which is almost beyond belief.
158. Form of the mushroom. — A good example for this
study is the common mushroom (Agaricus campestris).
This occurs from July to November in lawns and grassy fields.
The plant is somewhat umbrella-shaped, as shown in fig. 62,
and pos*sesses a cylindrical stem attached to the under side of
the convex cap or pileus. On the under side of the pileus are
thin radiating plates, shaped somewhat like a knife blade.
These are the gills, or lamellae, and toward the stem they are
86
BOTANY.
HOW PLANTS OBTAIN FOOD.
87
rounded on the lower angle and are not attached to the stem.
The longer ones extend from near the stem to the margin of
the pileus, and the V-shaped spaces between them are occupied
by successively shorter ones. Around the stem a little below
the gills is a collar, termed the ring or annulus.
Fig. 62.
Agaricus campestris. View of under side showing stem, annulus, gills, and margin of pileus.
159. Nutrition of parasitic fungi. — Certain of the fungi
grow on or within the higher plants and derive their food
materials from them and at their expense. Such a fungus is
called a parasite, and there are a large number of these plants,
which are known as parasitic fungi. The plant at whose
expense they grow is called the ' ' host. ' '
One of these parasitic fungi, which it is quite easy to obtain
in greenhouses or conservatories during the autumn and winter,
is the carnation rust (Uromyces caryophyllinus], since it breaks
out in rusty dark brown patches on the leaves and stems of the
carnation (see fig. 63). If we make thin cross-sections through
one of these spots on a leaf, and place them for a few minutes
in a solution of chloral hydrate, portions of the tissues of the
88
BOTANY.
leaf will be dissolved.
After a few minutes we wash the sec-
tions in water on a glass
slip, and stain them with a
solution of eosin. If the
sections were carefully
made, and thin, the threads
of the mycelium will be
seen coursing between the
cells of the leaf as slender
threads. Here and there
will be seen short branches
of these threads which
penetrate the cell wall of
the host and project into
the interior of the cell in
the form of an irregular
knob. Such a branch is a
hcustorium. By means of
this haustorium, which is
here only a short branch
of the mycelium, nutritive
substances are taken by the
fungus from the proto-
plasm or cell-sap of the
carnation. From here it
passes to the threads of the mycelium. These in turn supply
food material for the development of the dark brown gonidia,
which we see form the dark-looking powder on the spots.
Many other fungi form haustoria, which take up nutrient
matters in the way described for the carnation rust.
160. Nutrition of the dodder, — The dodder (cuscuta) is an
example of one of the higher plants that is parasitic. The stem
twines around the stems of other plants, sending short conical
processes termed haustoria in their tissues. By means of these
the nutriment is absorbed from the host. The means of absorb-
fig. 03.
Carnation rust on leaf and flower stem.
From photograph.
HOW PLANTS OBTAIN FOOD. 89
ing nutriment may be demonstrated by making sections through
both parasite and host at a point where the haustoria enter the
stem. These should then be mounted for examination with
the microscope.
Fig. 64.
Several teleutospores, showing the variations in form.
161. Carnivorous plants, or insectivorous plants, — Examples
of these are the well-known Venus fly-trap (Dionaea muscipula)
and the sundew (Drosera rotundifolia). These are illustrated
in figures 67 and 68. The lamina of the leaf of the Venus
Cell-
Fig. 65.
from the stem of a rusted carnation, showing the intercellular mycelium and haus-
toria. Object magnified thirty times more than the scale.
fly-trap resembles a steel trap, as shown open in figure 67.
When an insect alights on the leaf and touches one of the hairs
(there are three prominent hairs on the upper surface of each
9o
BOTANY.
half of the leaf), the leaf suddenly closes and captures it. It
has been found that when the hair is touched the first time no
movement of the leaf takes place, but when it is touched the
second time the leaves close up suddenly. There are small
glands on the surface of the leaf which excrete a substance that
digests the insect, when the digested portions are absorbed by
the leaf and are assimilated by the plant as food. The leaf of
the sundew is quite different in form and action. In the species
Fig. 66.
Dodder.
illustrated here the lamina of the leaf is rotund, and the upper
surface is covered with numerous long glandular hairs. The
gland is on the end of the hair, and a sticky substance is
HOW PLANTS OBTAIN FOOD.
excreted by the cells of the gland, which glistening in the sun-
light reminds one of drops of dew. For this reason the plant
is called the sundew. When an insect alights on a leaf the
viscid substance clings to it and holds it firmly so that it
cannot escape. The glandular hairs then begin slowly to curve
inward toward the centre of the leaf as shown in figure 68.
Finally the margins of the leaf become inrolled also, so that
the insect is held fast and close to the upper surface of the
leaf. Excretions from the leaf surface act as a digestive
ferment upon the insect.
162. Nutrition of bacteria. — Bacteria are very minute plants,
in the form of short rods, which are either straight or spiral,
while some are minute
spheres. They are widely
distributed; some cause dis-
eases of plants and animals,
others cause decay of organic
matter, while still others play
an important role in con-
verting certain nitrogen com-
pounds into an available form
for plant food. They absorb
their food through the sur-
face of their body,
may be obtained in
ance for study in infusions iobes
of plants or of meats.
To demonstrate bacteria in infusions take a small quantity
of hay or of meat. Place it in water and heat at about 60° C.
for an hour. Then set the vessel containing the infusion aside
in a warm room for several days. Numbers of bacteria will be
developed, some of them probably motile. With a good micro-
scope they may be demonstrated by mounting a drop of the
infusion on a glass slip and preparing for examination with the
microscope
Fig. 67.
Thev Leaf 9f Venus fly-
J trap (Dionaea musci-
ahnnd- pula), showing winged
petiole and toothed
Fig. 68.
Leaf of Drosera ro-
tundifolia, some of the
glandular hairs fold-
ing inward as a result
of a stimulus.
92 BOTANY,
Nitrogen gatherers.
163. How clovers, peas, and other legumes gather ni-
trogen.— It has long been known that clover plants, peas,
beans, and many other leguminous plants
are often able to thrive in soil where the
cereals do but poorly. Soil poor in nitro-
genous plant food becomes richer in this
substance where clovers, peas, etc., are
grown, and they are often planted for the
purpose of enriching the soil. Leguminous
plants, especially in poor soil, are almost
certain to have enlargements, in the form
of nodules, or " root tubercles." A root
of the common vetch with some of these
root tubercles is shown in fig. 6q.
Fig. 69.
Root of the common vetch, 163a. A fungal or bacterial organism
showing root tubercles. ,11 T r
in these root tubercles. — If we cut one
of these root tubercles open, and mount a small portion of the
interior in water for examination with the microscope, we shall
find small rod-shaped bodies, some of which resemble bacteria,
while others are more or less forked into forms like the letter
Y, as shown in fig. 70. These bodies are rich in nitrogenous
substances, or proteids. They are portions of a minute organ-
ism, of a fungous or bacterial nature, which attacks the roots
of leguminous plants and causes these nodular outgrowths.
The organism (Phytomyxa leguminosarum) exists in the soil
and is widely distributed where legumes grow.
164. How the organism gets into the roots of the legumes.
—This minute organism in the soil makes its way through the
wall of a root hair near the end. It then grows down the
interior of the root hair in the form of a thread. When it
reaches the cell walls it makes a minute perforation, through
which it grows to enter the adjacent cell, when it enlarges
again. In this way it passes from the root hair to the cells of
HOW PLANTS OB 7 'A IN FOOD. 93
the root and down to near the centre of the root. As soon as
it begins to enter the cells of the root it stimulates the cells of
that portion to greater activity. So the root here develops a
large lateral nodule, or "root tubercle/' As this "root
Fig. 70 Fig. 7i.
Root-tubercle organism from vetch, old con- Root-tubercle organism from Medicago
dition. clenticulata.
tubercle" increases in size, the fungus threads branch in all
directions, entering many cells. The threads are very irregular
in form, and from certain enlargements it appears that the rod-
like bodies are formed, or the thread later breaks into myriads
of these small " bacteroids. "
165. The root organism assimilates free nitrogen for its
host. — This organism assimilates the free nitrogen from the air
in the soil, to make the proteid substance which is found stored
in the bacteroids in large quantities. Some of the bacteroids,
rich in proteids, are dissolved, and the proteid substance is
made use of by the clover or pea, as the case may be. This is
why such plants can thrive in soil with a poor nitrogen content.
Later in the season some of the root tubercles die and decay.
In this way some of the proteid substance is set free in the soil.
The soil thus becomes richer in nitrogenous plant food.
The forms of the bacteroids vary. In some of the clovers
they are oval, in vetch they are rod-like or forked, and other
forms occur in some of the other genera.
CHAPTER XVI.
RESPIRATION
Exercise 33.
166. Simple experiment to demonstrate the evolution of C02 during
germination. — Where there are a number of students and a number of large
cylinders are not at hand, take bottles of a pint capacity, place in the bottom
some peas soaked for 12 to 24. hours. Cover with a glass plate which lias
been smeared with vaseline to make a tight joint with
the mouth of the bottle. Set aside in a moderately
warm place for 24. hours. Then slide the glass plate
a little to one ^ide and quickly pour in a little baryta
water so that it will run down on the inside of the
bottle. Cover the bottle again. Note the precipitate
of barium carbonate which demonstrates the presence
of CO.j in the bottle. Lower a lighted taper. It is
extinguished because of the great quantity of CO2.
Exercise 34.
Fig. 72.
Test for presence of
167. Comparison of respiration in plants and ani-
mals.— Take some of the baryta water and breathe
upon it. The same film is formed. The carbon diox-
ide which we exhale is absorbed by the baryta water
and forms barium carbonate, just as in the case of the ^itr/'ire
peas. In the case of animals the process by which (Sachs.)
oxygen is taken into the body and carbon dioxide is given off is respiration.
The process in plants which we are now studying is the same, and also is
respiration. The oxygen in the vessel was partly used up in the process and
•carbon dioxide was given off. (It will be seen that this process is exactly the
opposite of that which takes place in starch formation.)
Exercise 35 (or Demonstration).
168. Respiration is necessary for growth. — After we have performed the
experiment in paragraph 166, if the vessel has not been open too long so
94
RESPIRA TION.
95
that oxygen has entered, we may use the vessel for another experiment,
or set up a new one to be used in the course of 12 to 24 hours, after the oxy-
gen has been consumed. Place some folded damp filter paper on the ger-
minating peas in the jar. Upon this place one-half dozen peas which have
just been germinated, and in which the roots are about 2O-2$in>n long. See
figures 73, 74. The vessel should be covered tightly again and set aside in a
Fig. 73-
Fig. 74-
Fig.
Fig. 73.— Seedlings in vessels containing an excess of carbon dioxide, and very little
oxygen. No growth takes place.
Fig. 74. — Vessel with normal air used as a check. No excess of carbon dioxide, usual
amount of oxygen. Normal growth takes place.
Figures 73^ and 740. represent the condition of the peas in the experiment shown in figs.
73 and 74. a month later. The cylinders as set up for that experiment were left fora
month and then photographed. The peas in the cylinder containing normal air have
grown, producing stems which reach to the top of the cylinder, while in fig. 73^, where
the oxygen was absent, the peas have died. At this time a test was made with a lighted
taper; it burned brightly in the cylinder 74^, but was quickly extinguished in the cylinder
73«. The peas having died in this jar, decomposition had taken place and other gases than
carbon dio.xide were present, but there was not sufficient oxygen to support combustion.
warm room. A second jar with water in the bottom instead of the germinat-
ing peas should be set up as a check. Damp folded filter paper should be
supported above the water, and on this should be placed one-half dozen peas
with roots of the same length as those in the jar containing carbon dioxide.
96
BOTANY.
169. Oxygen is necessary for growth. — In 24 hours examine and note
how much growth has taken place. It will be seen that the roots have elon-
gated but very little or none in the first jar, while in the second one we see
that the roots have elongated considerably, if the experiment has been carried
on carefully. Therefore in an atmosphere devoid of oxygen or an excess of
carbon dioxide, very little growth will take place, which shows that normal
respiration with access of oxygen is necessary for growth.
170, Energy set free during respiration. — From what we
have learned of the exchange of gases during respiration we
infer that the plant loses carbon during
this process. If the process of respira-
tion is of any benefit to the plant, there
must be some gain in some direction
to compensate the plant for the loss of
carbon which takes place.
It can be shown by an experiment
that during respiration there is a slight
elevation of the temperature in the
plant tissues. The plant then gains
some heat during respiration. We
have also seen in the attempt to grow
seedlings in the absence of oxygen that very little growth takes
place. But when oxygen is admitted growth takes place
rapidly. The process of respiration, then, also sets free energy
which is manifested in one direction, by growth.
Fig. 75-
Pea seedlings ; the one
at the left had no oxygen
and little growth took
place; the one at the right
in oxygen and growth was
evident.
Demonstration 27.
171. To set up the apparatus for demonstrating respiration. -r-Soak a
double handful of peas for 12 to 24 hours in an abundance of cool water.
Prepare a small quantity of baryta water, a saturated solution, and filter some
into a short wide vial. Take a glass cylinder about ^cni high by $cm in
diameter. Select a perforated rubber cork to fit very tightly when crowded
part way in the open end of the cylinder. Prepare a long S manometer by
bending a glass tube which is about one and one-half meters long by G/HHI
inside diameter, into the form shown in figure 76. Put mercury into one
end of the manometer as shown in the figure, and if it is desired to show the
RESPIRA TION.
97
experiment at a distance in the classroom, place a small quantity of a solu-
tion of eosin r.bove each column of mercury. Insert the other end of the
manometer through the preforation in
the rubber cork. It must fit very tightly.
If there is another perforation plug it
with a glass rod. Take a wide -mouthed
small glass jar — a small glycerine jelly
jar is good — which will go inside the
cylinder. Break a few sticks of caustic
potash and drop in it. Nearly fill with
water and tie a string around the top
so that it can be lowered into the upper
part of the cylinder without spilling any
of the potash solution. Prepare a sup-
port for this by inserting a glass rod
about lyin long into a cork. Have all
the parts of the apparatus and the ma-
terial ready, and the baryta water in
the open vial, so that the apparatus
may be set up quickly. Have the cylin-
der warm and set the apparatus up in a
room where the temperature is about
20° C. (about 68° Fahr.). Place a small
quantity of damp paper (not wet) in the
bottom of the cylinder. Place in the
soaked peas to fill about 8cm to locm.
Upon these place the small vial of baryta
water. Drop in the support and press
the glass rod down far enough so that
the jar of potash solution will enter and
pass far enough below the mouth of the
cylinder to be out of the way of the
rubber cork.
Insert the rubber cork containing the
S manometer of mercury, placing be-
tween it and the side of the cylinder a
stout needle to allow the escape of air
1 .« i i . *' *&• yu.— — n t ur^muiuv; ui <: A pci 1 1 1 itru L ^
While the cork is pressed m tightly, mercury in each arm equal. No oxygen has
This allows the mercury to remain at X^-A? cUfo? experiment ; mer-
the same level in both arms of the tube <nn'v in inner arm has rist '"• Some oxygen
,T ' has been consumed.
.Now remove the needle and set the
apparatus aside where the temperature will remain at about 20° C. , and let
Fig. 76. Fig. 77.
Experiment to demonstrate respiraton.
Fig-. 76. — At beginning of experiment ;
98
BOTANY.
stand for about 24 hours. The apparatus should be set up quickly so that
forming carbon dioxide will not displace the air.
172. Carbon dioxide given off during germination while
oxygen from the air is con-
snmed. — In a short while
there can be seen a whitish
film on the baryta water in
the vial. In less than an hour
this film may become so thick
that with a little agitation it
breaks and settles as a white
precipitate. This white pre-
cipitate is barium carbonate.
Some of the carbon dioxide
given off by the peas is ab-
sorbed by the baryta water
forming the insoluble barium
carbonate. Carbon dioxide is
also absorbed by the caustic
potash solution in the bottom
of the cylinder. Owing to
the slowness with which the
carbon dioxide diffuses from
between the peas into the
potash solution an excess may
be formed. This excess of
carbon dioxide in the cylinder
produces a pressure which is
shown by the rise of the mer-
cury in the outer arm of the
Fig.78 Fig. 79. tube*
t-xperiment to demonstrate respiration.
Fig. 78.— At beginning of experiment; mer- In about 24 hours observe
the experiment. It the mer-
cury in each arm equal.
consumed in vessel.
No oxygen has been
hT/S cury is still higher in the outer
arm it shows that there is still
* When this inside pressure is produced it shows that more CO2 is
RES P IRA TION. 99
an excess of CO2 in the cylinder. At any rate lift the cylinder
with the hands in such a way as to hold firmly at the same time
the glass tube. Lift it up and down in such a way as to spill a
portion of the baryta water over against the wall of the cylinder,
and to dash the potash solution into a spray. Be careful not
to toss the mercury out of either arm of the tube. If the open
arm of the glass tube is closed with the finger (should the
apparatus be set up as indicated in fig. 78), the cylinder may
be inclined so as to let a portion of the potash solution run up
among the peas to come directly in contact with the CO,
remaining there. Now rest the cylinder" on the table and
observe the result. The mercury now, if it did not before,
stands higher in the inner arm of the S tube, showing that some
constituent of the air within the cylinder was consumed during
the formation of the CO2. This constituent of the air must be
oxygen, since the carbon can only come from the plant. Where
the baryta water was spilled over an abundance of the white
precipitate of the barium carbonate is formed.
If desired the experiment can be set up as shown- in figure
78, with the potash solution in the bottom of the cylinder, and
the peas supported on a circular piece of wire netting held in
place between two small corks inserted in a glass rod. At the
close of the experiment when the cylinder is being agitated the
escaping baryta water- forms a large quantity of the whitish
precipitate as it washes down the side of the cylinder.
being set free than oxygen is being consumed. This feature of the ex-
periment demonstrates what is known as intramolecular respiration, a kind
of respiration which can go on independently of the entrance of the oxygen.
See the author's larger " Elementary Botany " page 58.
1OO BOTANY.
Demonstration 28.
173. Respiration in a leafy plant. — We may take a potted plant which
has a well-developed k-af surface and place it under a tightly fitting bell jar.
Under the bell jar there also should be placed a
small vessel containing baryta water. A similar
apparatus should be set up, but with no plant, to
serve as a'check. The experiment must be set up
in a room which is not frequented by persons, or
the carbon dioxide in the room from respiration will
vitiate the experiment. The bell jar containing the
plant should te covered with a black cloth to prevent
starch formation. In the course of ten or twelve
Test for liberation of hours, if everything has worked properly, the baryta
carbon dioxide from leafy water under the jar with the plant will shew the film
giant during respiration,
aryta water in smaller of barium carbonate, while the other one will show
none. Respiration, therefore, takes place in a leafy
plant as well as in germinating seeds.
Synopsis. — Respiration (taking in oxygen and giving off carbon dioxide)
occurs in all plants during growth.
Respiration takes place actively in germinating seeds and opening buds
and flowers.
Respiration without access of oxygen (intramolecular respiration) takes
place, in germinating seeds for example, in addition to normal respiration.
Respiration in plants is the same process as in animals.
The carbon dioxide from respiration may be detected by testing the air in
the vessel where the plant is growing with a lighted taper (the taper is ex-
tinguished), or by baryta water (the baryta water absorbs carbon dioxide,
forming the insoluble barium carbonate), or by lime water (the lime water
absorbs carbon dioxide, forming the insoluble calcium carbonate =.- chalk).
Access of oxygen is necessary for the growth of most plants. (Some bac-
teria will only grow in the absence of oxygen.)
Respiration is a breaking-down process. (Changes take place in the pro-
toplasm, the entering oxygen uniting with some of the carbon and oxygen of
the protoplasm and forming CO,.) Compare this with the burning of plant
substance.
Respiration transforms energy in the plant, which is manifested by an
elevation of the temperature of the plant substance, so that the plant gains
some heat ; it is also manifested by growth.
RES P IRA TION.
101
Starch formation or
Photosynthesis.
Respiration.
Comparison of respiration and starch formation.
Carbon dioxide is taken in by the plant and oxygen
is liberated.
Starch is formed as a result of the metabolism, or
chemical change.
The process takes place only in green plants, and in
the green parts of plants, that is, in the presence
of the chlorophyll. (Exception in purple bacte-
rium.)
The process only takes place under the influence oi
sunlight.
It is a building-up process, because new plant sub-
stance is formed.
Oxygen is taken in by the plant and carbon dioxide
is liberated.
Carbon dioxide is formed as a result of the meta-
bolism, or chemical change.
The process takes place in all plants whether they
possess chlorophyll or not (exceptions in anaerobic
bacteria).
The process takes place in the dark as well as in
the sunlight.
It is a breaking-down process, because combustion
of plant substance occurs.
Material and apparatus. — Peas soaked for 24 hours in cold water (enough
for class and for demonstration).
Peas germinated, and with roots about 2Qmm long. A few should be
started 4 or 5 days in advance of the time they are wanted.
Wide-mouthed bottles, or cylinders, with glass plates and vaseline, to
close them, or corks (glass plates are better).
Tapers, or soft wood splinters for flaming.
Baryta water (saturated solution of barium hydrate in water) in tightly
stoppered bottle.
Watch glasses for baryta water.
For demonstration 27: glass cylinder about 35«;/high by $cm in diameter ;
perforated rubbor cork to fit very tightly ; S manometer made from glass
tubing about 6mm diameter ; mercury ; small glass jar and vial ; support
as indicated in demonstration 27 ; tome sticks of caustic potash ; baryta
water ; a stout needle.
For demonstration 28: potted plant ; bell jar to cover ; baryta water.
CHAPTER XVII.
GROWTH.
174. Meaning of growth. — By growth is usually meant an
increase in the bulk of the plant accompanied generally by an
increase in plant substance. Among the lower plants growth
is easily studied in some of the fungi.
175. Growth of roots. — For the study of the growth of roots
we may take any one of many different plants. The seedlings
of such plants as peas, beans, corn, squash, pumpkin, etc.,
serve excellently for this purpose.
Exercise 36.
176. To study growth of roots. — The seeds, a handful or so, are soaked
in water for about 12 hours, and then placed between layers of paper or
between the folds of cloth, which must be kept quite moist but not very wet,
and should be kept in a warm place. (See demonstration 2.)
The primary or first root (radicle) of the embryo pushes its way out
between the seed coats at the small end. When the seeds are well germi-
nated, select several which have the root 4-5 cm long. With a crow-quill
pen we may now mark the terminal portion of the root off into very short
sections as in fig. 81. The first mark should be not more than \mm from
the tip, and the others not more than imm apart. Now place the seedlings
down on damp filter paper, and cover with a bell jar so that they will re-
main moist, and if the season is cold place them in a warm room. At
intervals of 8 or 10 hours, if convenient, observe them and note the further
growth of the root. Sketch the root with the marks at the beginning of the
experiment, and at the different times the observations are taken. Where
does the elongation take place ? Determine this by the marks on the root
which separate. Where is the region of greatest elongation ? Does the
region of greatest elongation change ?
102
GROWTH.
103
177. The region of elongation. — While the root has elon-
gated, the region of elongation is not at the tip of the root. It
lies a little distance back from the tip, beginning at about 2mm
from the tip and extending over an area
represented by from 4 to 5 of the millimeter
marks. The root shown in fig. 66 was
marked at 10 A.M. on
July 5. At 6 P.M. of
the same day, 8 hours
later, growth had taken
place as shown in the
Fig. 81.
Root of germinating pumpkin, showing region of
elongation just back of the tip.
middle figure. At 9 A. M. on the following day, 1 5 hours later, the
growth is represented in the lower one. Similar experiments
upon a number of seedlings gives the same result : the region of
elongation in the growth of the root is situated a little distance
back from the tip. Further back very little or no elongation
takes place, but growth in diameter continues for some time,
as we should discover if we examined the roots of growing
pumpkins, or other plants, at different periods.
178. Movement of region of greatest elongation. — In the
region of elongation the areas marked off do not all elongate
equally at the same time. The middle spaces elongate most
rapidly and the spaees marked off by the 6, 7, and 8 mm marks
elongate slowly, those farthest from the tip more slowly than
the others, since elongation has nearly ceased here. The spaces
marked off between the 2-^mm marks also elongate slowly, but
soon begin to elongate more rapidly, since that region is becom-
ing the region of greatest elongation. Thus the region of
greatest elongation moves forward as the root grows, and
remains approximately at the same distance behind the tip.
IO4
BOTANY.
Exercise 37.
179. Growth of the stem. — We may use a bean seedling growing in the
soil. At the junction of the leaves with the stem there are enlargements.
These are the nodes, and the spaces on the stem between successive nodes
are the internodes. We should mark off several of these internodes, espe-
cially the younger ones, into sections about $mm long. Now observe these
at several times for two or three days, or more. The region of elongation
is greater than in the case of the roots, and extends back further from the
end of the stem. In some young garden bean plants the region of elonga-
tion extended over an area of ^.omm in one internode.
180. Force exerted by growth. — One of the marvellous
things connected with the growth of plants is the force which
is exerted by various members of the plant under certain condi-
tions. Observations on seedlings as they are pushing their way
through the soil to the air often show us that considerable force
is required to lift the hard soil and turn it to one side. A very
/^ striking illustration may be had
in the case of mushrooms which
sometimes make their way through
the hard and packed soil of walks
or roads. That succulent and
tender plants should be capable
of lifting such comparatively
heavy weights seems incredible
until we have witnessed it. Very
striking illustrations of the force
of roots are seen in the case of
trees which grow in
rocky situations, where
rocks of considerable
82t weight are lifted, or
Lever auxanometer (Dels) for measuring elongation of grnall riftS in larffe rocks
the stem during growth.
are widened by the
lateral pressure exerted by the growth of a root, which entered
when it was small and wedged its way in.
GROWTH. 105
If the season of the year is one that will permit, make some
observations on the force exerted by seedlings in coming through
the hard earth; of mushrooms coming up through dry and
hard earth; of the wedging of roots in the crevices of rocks.
Or recall and note any observations of this kind made in the
past. One has only to note the immense size and weight of
some trees to understand the force which must have been ex-
pended during their growth in lifting up the food materials for
these massive objects.
181. Energy of growth. — This is manifested in the compara-
tive size of the members of a given plant. To take the sun-
flower for example, the lower and first leaves are comparatively
small. As the plant grows larger the leaves are larger, and this
increase in size of the leaves increases up to a maximum period,
when the size decreases until we reach the small leaves at the
top of the stem. The zone of maximum growth of the leaves
corresponds with the maximum size of the leaves on the stem.
The rapidity and energy of growth of the stem is also correlated
with that of the leaves, and the zone of maximum growth is
coincident with that of the leaves. It would be instructive to
note it in the case of other plants.
Exercise 38.
182. To study zone of maximum growth. — Study the zone of maximum
growth in several plants which may be at hand. Some plants may be ob-
tained for use from conservatories. Other plants may be collected during the
growing season and preserved for this purpose. Corn plants, for example,
can be gathered at maturity in the early autumn or late summer. They
may be carefully pressed entire, and mounted on large sheets, or on paste-
lx>;ml. The zones of maximum growth of the stem as well as of the leaves
can be studied from these preserved plants. The plants in this condition
will serve this purpose for several years.
For other experiments and studies on growth see the author's
larger ' ' Elementary Botany.
io6
BOTANY.
Growth.
Synopsis.
An increase in the bulk or size of the plant.
(Parts of the plant become longer and stouter.)
Growth in length of the root takes place most actively a few
millimeters back from the tip.
The region of elongation of the root changes as the root be-
comes longer.
Growth in length is the result of the elongation of the newly
formed cells [the formative region (i.e., where new cells are
formed; is in the root .tip].
The stem grows in a similar way, but the region of elongation
extends over a greater area than in the root.
As a result of the increase in the size of plants by growth,
great force is exerted, sufficient to move considerable amounts
of hard earth ; or, in the case of trees, to even split rocks,
or to lift up during growth the entire plant material in
trunk and branches.
The energy of growth during the season, or during the life of
an annual, varies. It is low at first, as manifested by the
small size of the members, then it increases to a maximum,
then decreases.
Material and apparatus. — Seedlings of squash, or pumpkin, or peas, etc.,
grown in a germinator free from earth. The seeds should be started a
week to ten days before they are wanted, so that the roots will be about
3cm to \cm long. (See demonstration 2 for preparing seedlings.) Sev-
eral moist chambers; large corks upon which some of the seedlings can be
pinned.
India ink and crow-quill pen for marking the roots.
Seedlings grown in soil in pots with the stems just appearing above
the soil.
Potted begonias; entire corn plants (may be pressed and preserved dry);
or small but mature sunflower plants (also may be preserved dry).
CHAPTER XVIII.
MOVEMENT IN PLANTS DUE TO IRRITABILITY.
183. Movement in response to stimulus, — Beside the growth
movements which take place in plant parts, the parts of plants
show certain movements which are due to irritability. In this
kind of movement the plant is influenced by some exciting cause,
called a stimulus. The stimulus acts upon the irritable part of
the plant, and in response to this movement occurs. We can
easily study the effect of several different kinds of stimuli.
184. Influence of the earth on the direction of growth.— In
the germination of the seeds which we have used in some of the
earlier experiments it has probably been observed that the direc-
tion which the root and stem take upon germination is not due
to the position in which the seed happens to lie. Under normal
conditions we have seen that the root grows downward and the
stem upward.
Exercise 39.
185. To study the influence of the earth on roots.— Take seedlings grown
in a germinator which are free from the soil. Pin several seedlings to a cork
in such a way that the stems and roots of different ones will be lying in
different directions. Mark off the tip of the root of several with ink, as in
paragraph 176. Cut off the extreme tip from a few of the roots. Place the
cork in a moist chamber, with an abundance of water or saturated paper in
the bottom. On the following day observe the positions of the roots and
stems. Sketch and annotate. In the case of the roots marked into millimeter
spaces determine the motor zone (region of curvature) of the root. Comparing
these with the roots from which the tip was cut determine the perceptive zone
(the zone which receives the stimulus). Now turn the cork in another posi-
tion, leave for a day and note the result.
107
108 BOTANY.
Exercise 4O.
186. Influence of the earth on stems and leaves. — Place rapidly growing
potted plants horizontally. Seedlings in pots, or young plants, or potted
hyacinths are good ones to use. In the course of a day observe the positions
of the stems and leaves. Sketch some of them.
187. Gravity acts as a stimulus. — Knight found that the
stimulus which influences the root to turn downward is the force
of gravity. The reaction of the root in response to this stimulus
is geotropism, a turning influenced by the earth. This term is
applied to the growth movements of plants influenced by the
earth with regard to direction. While the motor zone lies back
of the root tip, the latter receives the stimulus, and is the per-
ceptive zone. If the root tip is cut off the root is no longer
geotropic, and will not turn downward when placed in a hori-
zontal position. Growth toward the earth is pro geotropism.
The lateral growth of secondary roots is diageotropism.
188. The result with stems. — The stem, on the other hand,
which was placed in a horizontal position has become again erect.
Fig. 83. ' Fig. 84.
Germinating pea placed in a hori- In twenty-four hours gravity has caused the.
zontal position. root to turn downward.
Figures 83, 84. — Progcotropism of the pea root.
This turning of the stem in the upward direction takes place in the
dark as well as in the light, as we can see if we start the experiment
at nightfall, or place the plant in the dark. This upward growth
of the stem is also influenced by the earth, and therefore is a case
of geotropism. The special designation in the case of upright
stems is negative geotropism, or apo geotropism, or the stems are
said to be apo geotropic. Place a rapidly growing potted plant
in a horizontal position by laying the pot on its side. The ends
MOVEMENT IN PLANTS DUE TO IRRITABILITY. 1 09
of the shoots will soon turn upward again. Young bean plants
growing in a pot began within two
hours to turn the ends of the shoots
upward.
Horizontal leaves and shoots can
be shown to be subject to the same in-
fluence, and are therefore diageoiropic.
189. Influence
of light. — Not
Fig. 85.
Pumpkin seedling showing apogeotropism. Seedling at the left placed hori-
zontally. In twenty-four hours the stem has become erect.
only is light a very important factor for plants during starch
formation, it exerts great influence on plant growth and
movement.
Demonstration 29.
190. To prepare plants grown in the dark — Three or four weeks be-
fore these plants are wanted for study the teacher may plant a sufficient
number of seeds (radish or other seeds) in small pots for the class to study.
Several different kinds of seeds may be used for comparison if desired.
Place one lot of the pots in a warm but very dark place. They may be put
in a box, and the box can be then covered with two or three layers of black
cloth, sufficient to shut out all light. Keep the box in a warm room, and oc-
casionally open it to water the plants if necessary. The lot kept in the
light should have the same temperature conditions. If preferred the pupils
can plant the seeds, and place those to be grown in the dark in a common
box. This is preferable if it is convenient for the pupils to do it.
Exercise 41 .
191. Influence of light on the growth of plants.— When the plants have
grown for about two weeks they will be ready for study. Compare the
plants grown in the dark with those grown in the light. Which lot have
the longer stems ? What influence then does light have on growth in
no
BOTANY.
length? Which plants have the larger leaves? What influence does light
have on the development of leaves ? What is the difference in color of the
plants ? What is the cause of this ? Which lot of plants have the firmer
tissues ? What is the cause of the difference in the firmness of the tissues ?
Sketch a plant grown in the dark ; sketch one to the same scale grown in
the light.
Exercise 42.
192. Influence of light on the direction of growth. — Take potted seed-
lings and place them near a window So that they will have a one-sided illu-
mination. Or place
them in a box which
has a small opening
at one side. After a
day or two observe
the position of the
seedlings. Does light
have an influence on
the direction of
growth ? What is the
direction with refer-
ence to the source of
light ? Sketch one
of the plants, and
indicate on the sheet
the direction of the
rays of light.
193. Influence Of Clark, long, slender, not green.
light on the position of leaves. — Take potte
plants with a number of leaves, and place thei
near a window for several days or a week. Ol
serve the position of the leaves at the beginning Fig. 87.
.of the experiment, and after a week's time. What „*££
is the position of the leaves with reference to the green m color. Growth re-
-,. , - ' . tarded by light,
source of light ? Can you tell why the leaves take
this position ?
194. Retarding influence of light on growth. — We have
only to return to the experiments performed in growing plants
in the dark to see one of the influences which light exerts on
plants. The plants grown in the dark were longer and more
Radish seedlings
MOVEMENT IN PLANTS DUE TO IRRITABILITY. Ill
slender than those grown in the light. Light then has a retard-
ing influence on the elongation of the
stem.
195. Influence of light on direction of
growth, — While we
are growing seed-
lings, the pots or
boxes of some of
them should
be placed
so that the
plants will
have a one-
sided illu-
Seedling of castor-oil bean, before and
after a one-sided illumination. m j
This can be
done by placing them near an open win-
dow, in a room with a one-sided illumi-
nation, or they may be placed in a box
closed on all sides but one which is facing
the window or light. In 1 2-24 hours, or
even in a much shorter time in some cases,
the stems of the seedlings will be directed
— toward the source of light. This influence
exerted by the rays of light is heltolropism, a turning influenced
by the sun or sun-
light.
196. Diaheliot-
ropism. — Horizon-
tal leaves and
shoots are diahe-
liotropic as well as _.
Uark chamber with opening at one side to show heliotropism.
did geo tropic. The (After Schleichert.)
general direction which leaves assume under this influence is
that of placing them with the upper surface perpendicular to
H2 BOTANY.
the rays of light which fall upon them. Leaves, then, exposed
tQ the brightly lighted sky are, in general, horizontal. This
position is taken in direct response to the stimulus of light.
Sunflower plant removed from
darkness, leaves extt nding under
influence of light (diaheliotro-
pism).
The leaves of plants with
a one-sided illumination,
as can be seen by trial,
are turned with their upper surfaces
toward the source of light, or per-
pendicular to the incidence of the
light rays. In this way light over-
comes for the time being the direc-
tion which growth gives to the leaves.
The so-called " sleep " of plants is
of course not sleep, though the leaves
Fi«- 9°- ' ' nod, ' ' or hang downward, in many
Sunflower plant. Epinastic
condition of leaves induced dur- cases. 1 here are many plants in
ing the day in darkness.
which we can note this drooping of
the leaves at nightfall, and in order to prove that it is not
determined by the time of day we can resort to a well-known
experiment to induce this condition during the day. The plant
which has been used to illustrate this is the sunflower. Some
of these plants, which were grown in a box, when they were
MOVEMENT IN PLANTS DUE TO IRRITABILITY. 113
about 35cm high were covered for nearly two days, so that the
light was excluded. At midday on the second day the box was
removed, and the leaves on the covered plants are well repre-
sented by fig. 90, which was made from one of them. The
leaves of the other plants in the box which were not covered
were horizontal, as shown by fig. 91. Now on leaving these
plants, which had exhibited induced "sleep" movements,
exposed to the light they gradually assumed the horizontal
position again.
Synopsis.
Irritability.
Plants are irritable, that is, they respond to certain stimuli.
The force of gravity stimulates the tip of the root, and
causes the root to turn downward.
The " motor zone," in response to this stimulus, is co-
incident with the region of elongation of the root.
The perceptive zone is in the root tip.
The force of gravity stimulates the stem to turn upwards
(or away from the earth).
f Progeotropism (in first root).
Geotropism. •? Diageotropism (in lateral roots)*
( Apogeotropism^in stems).
Stems( horizontal stems are diahelio-
tropic) grow towards the light (heli-
otropic).
Leaves turn so as to face the light (un-
less the light is very strong, when
they may turn their edge toward
the light).
Light retards growth of stems, since
Influence of light. • stems grown in the dark are longer.
Plants do not "sleep"; when the
leaves turn downward at night it is
because the influence of light is re-
moved and the leaf is free to turn in
the direction caused by growth,, the
growth being more active usually on
the upper side of the leaf after it
pushes out from the bud.
114 BOTANY.
Material and apparatus. — Seedlings, moist chambers, corks and pins, as
in Chapter XVII.
Seedlings in pots (beans, squash or pumpkin), \ocrn to \^cm high.
Potted hyacinths if they can be obtained.
Seedlings grown in pots in the dark (about three weeks old), others of the
same age grown in the light.
Some dark boxes with small opening at one side, to receive some of the
pots of seedlings.
If possible some sunflower plants grown in pots, plants about zoctn to
y>cm high, and tall dark boxes to cover them when desired.
Sunflower plants should be started two or three months in advance.
Potted oxalis, which is often grown in conservatories, is better to show in-
duced " sleep" movements.
PART II: MORPHOLOGY AND LIFE HIS-
TORY OF REPRESENTATIVE PLANTS.
CHAPTER XIX.
SPIROGYRA.
197. Convenience in studying spirogyra. — In our study of
protoplasm and some of the processes of plant life we became
acquainted with the general appearance of the plant spirogyra.
It is now a familiar object to us. And in taking up the study
of representative plants of the different groups, we shall find
that in knowing some of these lower plants the difficulties of
understanding methods of reproduction and relationship are not
so great as they would be if we were entirely ignorant of any
members of the lower groups.
198. Form of spirogyra. — We have found that the plant
spirogyra consists of simple threads, with cylindrical cells
attached end to end. We have also noted that each cell of the
thread is exactly alike, with the exception of certain "hold-
fasts" on some of the species. If we should examine threads
in different stages of growth we should find that each cell is
capable of groAvth and division, just as it is capable of perform-
ing all the functions of nutrition and assimilation. The cells
of spirogyra then multiply by division. Not simply the cells at
the ends of the threads but any and all of the cells divide as
they grow, and in this way the threads increase in length.
199. Conjugation of spirogyra. — Under certain conditions,
when vegetative growth and multiplication cease, a process of
reproduction takes place which is of a kind termed sexual
BOTANY.
reproduction. If we select mats of spirogyra which have lost
their deep green color, we are likely to find differ-
ent stages of this sexual process, which in the
case of spirogyra and related plants is called
conjugation.
Fig. 92.
Thread of spiro-
gyra, showing long
cells, chlorophyll
band, nucleus,
strands of proto-
plasm, and the
granular wall layer
of protoplasm,
Fig. 93-
Zygospores of spirogyra.
Demonstration
30.
200. To demonstrate
the conjugation of spiro-
gyra.— From a tangle of
the threads on a glass
slip, which are conjuga-
ting, mount a few in
water, tease the threads
apart, place on a cover
glass, and prepare for
observation under the
microscope. Let the
pupils sketch conju-
gating cells, and make
notes upon the different
stages of the passage of
the protoplasm, and on
the other characters of
the fruiting threads, as
outlined below.
201. Conjugation.
— If the material is
in the right condition
we will see in certain
of the cells an oval
or elliptical body.
If we note carefully
the cells in which
these oval bodies are situated, there will be seen a
tube at one side which connects with an empty cell
of a thread which lies near as shown in fig. 93. If
SPIROGYRA. 117
we search through the material \ve may see other threads con-
nected in this ladder fashion, in which the contents of the cells
are in various stages of collapse from what we have seen in the
growing cell. In some the protoplasm and chlorophyll band
have moved but little from the wall ; in others they form a mass
near the centre of the cell, and again in others we will see that
the content of the cell of one of the threads has moved partly
through the tube into the cell of the thread with which it is
connected.
This suggests to us that the oval bodies found in the cells
of one thread of the ladder, while the cells of the other thread
were empty, are formed by the union of the contents of the
two cells. In fact that is what does take place. This kind
of union of the contents of two similar or nearly similar cells is
conjugation. The oval bodies which are the result of this con-
jugation are zygotes, or zygospores. When we are examining
living material of spirogyra in this stage it is possible to watch
this process of conjugation. Fig. 94 represents the different
stages of conjugation of spirogyra.
202. How the threads conjugate, or join. — The cells of two
threads lying parallel put out short processes. The tubes from
two opposite cells meet and join. The walls separating the
contents of the two tubes dissolve so that there is an open
communication between the two cells. Each one of these cells
corresponds to a sexual organ. This process of conjugation is
a sexual process. The process here is a very simple one be-
cause any cell of the thread without any particular change in
size or form may become a sexual organ. The cell which loses
its protoplasm is the supplying cell, while the one in which the
zygospore is formed is the receiving cell. Before the movement
of the protoplasm begins we cannot tell which is to be the sup-
plying cell or the receiving cell.
The passage of the protoplasm from one cell to another can
only be seen under the most favorable conditions, and then with
living material. It is possible, however, in preserved material
BOTANY.
to find cells which have the protoplasm in some of these different
stages. When the zygospores are being studied one should
look for some cells in these stages.
Conjugation in spirogyra ; from left to right beginning in the upper row is shown the
gradual passage of the protoplasm from the supplying cell to the receiving cell.
203. The zygospore. — This zygospore now acquires a thick wall which
eventually becomes brown in color. The chlorophyll color fades out, and a
large part of the protoplasm passes into an oily substance which makes it
more resistant to conditions which would be fatal to the vegetative threads.
The zygospores are capable therefore of enduring extremes of cold and dry-
ness which would destroy the threads. They pass through a "resting''
period, in which the water in the pond may be frozen, or dried, and with the
oncoming of favorable conditions for growth in the spring or in the autumn
they germinate and produce the green thread again.
For further reading on spirogyra and its relatives see the
author's larger " Elementary Botany," Chapter XV.
SPIROG YRA.
119
Synopsis.
Vegetative stage ; single unbranched threads, composed of
cylindrical cells end to end.
Cells all alike.
Grows by division and elongation of all the cells.
Spirogyra. -j Sexual stage ; conjugation of like cells.
Receiving and supplying cells, not differentiated.
Result of conjugation, a zy go spore.
The zygospore after a period of rest produces the spirogyra
thread again.
Material. — Spirogyra in conjugation, showing different stages, as well as
the zygospores. The material may be collected fresh, or it may be preserved
in 2% formalin collected in advance or purchased from supply companies.
Microscope, etc.
CHAPTER XX.
THE GREEN FELT: VAUCHERIA.
204. Description of vaucheria. — The plant vaucheria usually
occurs in dense mats floating on the water or lying on the damp
soil. The texture and feeling of one of these mats reminds one
of " felt, " and the species are sometimes called the ' ' green felts/'
The threads are quite ^tiltSk coarse and are
branched. Upon exami- nation with the mi-
croscope we find that the /j$$i?jj tnreads are contin-
uous, that is, there are no cross-walls as in
spirogyra dividing the thread up into short
cells. The chlorophyll is il$jjijj ^n sma^ ova^ bodies
scattered over the inside Jil!?*%ilr °* t^ie wa^ °^ tne
tube. These are the char- Jllt%f^ acters of the vegeta-
tive threads. A portion of §S^li$ a vegetative thread
is shown in fig. 95, Cross- jB|jffi|if walls are formed
only where reproductive J^|w ce^s or organs are
formed, which cut them rails' °^ ^rom tne re-
Portion of branched thread of vaucheria.
mainder of the vegetative thread. This plant multiplies in
several ways which would be too tedious to detail here. The
sexual reproduction,* however, should be studied if possible,
* Oedogonium maybe studied in place of vaucheria if preferred and if
material is more easily obtained. Vaucheria is usually more abundant and
1 2O
THE GREEN FELT: VAUCHERIA. 121
since the organs of reproduction can be readily seen, usually
much easier to study than in any of the plants belonging to the
higher groups. If fresh material is not at hand, that which has
been preserved in alcohol or formalin will serve very well.
Often excellent material is to be found in greenhouses growing
on the soil of pots during the winter, especially if one obtains
from outside in the autumn some bulbs of arisaema (jack-in-the-
pulpit) with soil near them for potting. Fresh material of
vaucheria in fruit is found easily during the autumn or spring.
At this time a quantity should be preserved. The sexual
organs are usually more abundant when the threads appear
somewhat yellowish or yellow green.
Exercise 43.
205. Gross characters of vaucheria. — If fresh material is at hand which
was growing in water, note how firmly the threads are tangled together ;
compare with spirogyra in this respect. Can you make out in this condition
that the threads are branched ? This branched condition of vaucheria is
one of the reasons for the dense tangle of threads. Note the coarse feeling ;
compare with spirogyra in this respect.
If material on the soil is at hand, note that it is not necessary that all
species grow in water. Note here also the dense tangle of threads. Lift up
a tuft with the needle ; compare the effect on the threads with that of spiro-
gyra when a tuft of the latter is lifted in the same way. Compare the
" feeling " of the threads with that of spirogyra.
Demonstration 31.
206. Sexual reproduction in vaucheria. — Mount a few threads of fruiting
vaucheria in water for microscopic study. If prepared slides are at hand
they will answer for the demonstration. Let each pupil make a sketch of
the sexual organs, and make notes of the form of the same ; also note the con-
tinuity of the threads, cross-walls, only being formed in connection with the
reproductive organs. Let theip compare the different stages found in the
formation of the ripe egg.
both kinds of the sexual organs are more easily found and understood, those
of oedogonium being more complicated. See Chapters XVI and XVII of
the author's larger "Elementary Botany."
BOTANY.
207. Vaucheria sessilis; the sessile vaucheria. — In this
plant the sexual organs are sessile, that is they are not borne
on a stalk as in some other
species. The sexual organs
usually occur several in a
group. Fig. 96 represents
a portion of a fruiting
plant.
208. Sexual organs of
vaucheria. Antheridium.
— The antheridia areishort,
96. slender, curved branches
Young antheridium and oogonium of Vaucheria , . , , .
sessilis, before separation from contents of thread by irom a mam thread. A
a septum. e , , . .
septum is iormed which
separates an end portion from the stalk. This end cell is the
antheridium. Frequently it is collapsed or empty as shown in
fig. 97. The protoplasm in the antheridium forms numerous
small oval bodies each with two slender lashes, the cilia. When
these are formed the antheridium opens at the end and they
Fig. 97-
Vaucheria sessilis, one antheridium between two oogonia.
escape. It is after the escape of these spermatozoids that the
antheridium is collapsed. Each spermatozoid is a male gamete.
209. Oogonium. — The oogonia are short branches also, but
they become large and somewhat oval. The septum which
separates the protoplasm from that of the main thread is as we
see near the junction of the branch with the main thread. The
GREEN PEL T : VA UCHER1A. \ 2$
oogonium, as shown in the figure, is usually turned somewhat to
one side. When mature the pointed end opens and a bit of the
protoplasm escapes. The . ^
remaining protoplasm / ]
forms the large rounded
egg cell which fills the wall
of the oogonium. In
some of the oogonia which
we examine this egg is sur-
rounded by a thick brown fclg 9?*
J Vaucneria sessihs ; oogonium opening and emit-
Wall, With Starchy and oily «nS a bit of protoplasm ; spermatozoi<fc ; sperma-
} J tozoids entering oogonium. (After Pnngsheim and
contents. This is the fer- Goebei.)
tilized egg (sometimes called here the oospore). It is freed
from the oogonium by the disintegration of the latter, sinks
into the mud and remains here until the following autumn
or spring, when it grows directly into a new plant. The
spermatozoids are very difficult to see and one should not expect
to study them here. Fertilization is brought about by the
spermatozoids swimming in at the open end of the oogonium,
when one of them makes its way down into the egg and fuses
with the nucleus of the latter.
210. Vaucheria compared with spirogyra. — In vaucheria
we have a plant which is very interesting to compare with
spirogyra in several respects. In spirogyra growth takes place
in all cells, that is in all parts of the thread, while in vaucheria
growth is confined to the ends of the threads and the ends of
the branches. This is a distinct advance on spirogyra. Again
in spirogyra any part of the thread (any cell) may become one
of the sexual organs. In vaucheria the sexual organs are
special branches, which are short, and further, the two organs
are different in size so that they can readily be distinguished
long before the time for fertilization. Then in vaucheria the
supplying cell does not give all its content to the receiving cell,
but only a bit of the protoplasm in the form of a minute body,
the spermatozoid.
124
BOTANY.
Vaucheria. \
Sexual organs
differentiated.
Synopsis.
Vegetative stage; branched threads, continuous, growth con-
fined to the ends of the threads and ends of the branches.
Sexual stage ; fertilization of an egg by a minute sperm nu-
cleus.
Antheridium (male organ). Contains num-
bers of small spermatozoids.
Oogonium (female organ). Contains one egg.
Result of fertilization is the formation of a fertilized egg
(oospore), which after a period of rest grows into the vau-
cheria plant again.
Material. — Freshly collected material of one of the species ofvaucheria
which is in fruit. It can be obtained from the water of ponds or ditches, or
it is very often found growing on soil of pots in greenhouses. If preferred
it may be collected in advance and be preserved in 2% formalin, or it may
be purchased of supply companies.
Microscope, etc.
CHAPTER XXI.
FUNGI: THE BLACK MOULD.
Demonstration 32.
211. To grow the mould.— This plant maybe grown by placing old bread,
or partly decaying fruits, as bananas, or the peelings of lemons or oranges
in a moist chamber. Set this in a warm place for about one week. Then
the plant may be grown on potatoes as described in paragraph 49, or one
may take the material for study directly from the bread. It should be
studied before it becomes very old.
Exercise 44.
212. Mycelium. — Before the black heads of the fungus appear, note the
delicate fluffy white tufts of threads which appear on the surface of the bread
or other substance on which the fungus is growing. These threads are the
mycelium, and a single thread is a mycelium thread, or " hyp ha"
Search on the margins of old cultures where the threads come in contact
with paper (some sheets of paper should be placed by the sides of the cul-
tures) or the sides of the vessels for "runners," long threads of mycelium
which touch the place of support here and there. Are there tufts of upright
threads at the points of contact which bear black heads ? Try to find the
connection of the black threads with the creeping mycelium.
If the mycelium has not been studied in a previous chapter the teacher
can mount some here for demonstration. Let the pupils note the branched,
colorless threads, and that there are no cross-walls. Note the granular
protoplasm.
At the microscope let each pupil note the long dark-colored stalks which
bear the rounded "heads" ; the Utter are the sporangia. If the spores are
mature the sporangium wall is perhaps broken and the spores more or less
scattered. If so, note the remnant of the wall as a small collar below the
enlarged end of the stalk. The enlar-jed end of the stalk is the "colu-
mella." In the younger stages of the sporangium, note the columella
arched up within the sporangium. Trace the stalks down to their attach -
1*5
126
BOTANY.
ment with the mycelium. Is there only one at this point of attachment, or
are there several? Are there any rhizoids present at the point of attach-
ment? Sketch the different stages.
213. Description of the mucor fruit. — We shall probably
note at once that the stalks or upright threads which support
the heads are stouter th'an the threads of the mycelium.
These upright threads soon have formed near the end a cross-
Fig. 99.
Portion of banana with a mould (Rhizopns nigricans) growing on one end.
wall which separates the protoplasm in the end from the
remainder. This end cell now enlarges into a vesicle of con-
siderable size, the head as it appears, but to which is applied
the name of sporangium (sometimes called gonidangium,
because it encloses the gonidid],
At the same time that this end cell is enlarging the cross-wall
is arching up into the interior. This forms the columclla. All
the protoplasm in the sporangium now divides into gonidia,
FUNGI: THE BLACK MOULD.
127
Fig. 100.
Group of sporangia of a mucor (Rhizopus nigricans) showing rhizoids and the stolon
extending from an older group.
These are small rounded or oval bodies. The wall of the
sporangium becomes dissolved, except a small collar around
the stalk which remains attached be-
low the columella (fig. 101). By this
means the gonidia are freed. These
gonidia germinate and produce the
mycelium again.
Fig. 101.
A mucor (Rhizopus nigricans) ; at left nearly mature sporangium with columella show-
ing within ; in the middle is ruptured sporangium with some of the gonidia clinging to the
columella ; at right two ruptured sporangia with everted columella.
128
BOTANY.
214, To show the "runners" of the black mould, — If some
filter paper is placed by the side of the bread or other substance
in the moist chamber, some of the threads of the fungus may
be induced to grow over on to it. If the mould is the species
illustrated in fig. 100 there may be seen " runners " like those
in the figure with clusters 'of the sporangia at certain points.
Certain threads of the mycelium grow along on the paper like
a strawberry " runner " does over the ground. Here and there
the mycelium touches the paper and forms little rootlets, and
also a group of the sporangia. It is because of this character that
the plant is called Mucor stolonifer, the stolon bearing mould.
Or the other name of " rhizopus " is given because it is " root-
footed."
Synopsis.
Grows on old bread, decaying fruits, vegetables, etc.
Vegetative part ; delicate whitish threads, which
branch, and form a cottony-like mat, called the my-
celium.
Fruiting part ; upright stout threads bear black heads,
called sporangia.
Several fruiting threads in a cluster,
with rhizoids at base.
Sporangium.
Sporangium wall.
Columella.
Spores (or gonidia).
Sexual stage not treated of here.
Material. — Cultures of the black mould on bread or baked potatoes. See
paragraph 49 for making the cultures.
Microscope, etc.
If conjugation of a mould is desired, it may be purchased of supply com-
panies.
The black mould.
Fruiting part. -
CHAPTER XXII.
FUNGI (CONTINUED) : WHEAT RUST.
(Puccinia graminis.)
215. Importance of the rusts. — The fungi known as " rusts "
are very important ones to study, since all the species are para-
sitic, and many produce serious injuries to crops.
Exercise 45.
216. Black rust of wheat. — Dried stalks of wheat or oats with the black
spots of this stage of the rust are excellent for the study. Sketch a portion of
an affected stalk, showing the spots in natural size and form. With a hand
lens examine the spots more carefully. Observe that the black mass of color
has burst through the epidermis of the wheat. Describe the" appearance.
217. Red rust of wheat. — This stage is found abundantly on the leaves of
the wheat and oats, etc. Dried leaves which have been pressed are good
for the study. Observe the color of the spots, and compare with that of the
black-rust spots. Compare the size also. Examine with a hand lens, and
determine whether the mass of spores making up the rust color, break through
the epidermis. Sketch a portion of the leaf showing the characters observed.
218 . Cluster-cup stage on the barberry. — Leaves of the barberry maybe
pressed dry and preserved for study. Sketch a leaf showing the location and
character of the spots. Describe the form and character of the spots. Ex-
amine the spots on both sides of the leaves with a hand lens. Describe what
you see. If leaves of the barberry with the cluster cups cannot be obtained
some other cluster-cup fungus may be used, but it should be understood that
the others are not connected with the wheat rust (except some growing on
shrubs closely related to the barberry).
Demonstration 33.
219. To demonstrate the different stages of the wheat rust under the micro-
scope.— Black rust: with a knife scrape out the material from a few black
spots, tease out in water on a glass slip, and mount as usual. Red rust : pre-
129
130
BO 7 'A NY.
pare in the same way from the yellow spots. To demonstrate Jhe cluster cups,
good cross-sections of the leaf through a spot should be made, or prepared
slides should be obtained. Let the pupils sketch the form of the different
spores, and other characters, and make notes of the observations.
To demonstrate mycelium in the tissues, use the carnation rust which can
be obtained in winter in greenhouses where the carnations are grown (see
Chapter XV, paragraph 159), or» fresh wheat leaves may be preserved in
alcohol for making sections.
220. Wheat rust (Puccinia graminis). — The wheat rust is
one of the best known of these fungi, since a great deal of study
has been given to it. One form of the plant occurs in long
Fig. 106
Single
sorus.
Fig. 102. Fig. 103. Fig. 104. Fig. 105.
Wheat leaf with red Portion of leaf Black rust. Enlarged,
rust, natural size. enlarged to show
sori.
Figures 102, 103. — Puccinia graminis, red-mst stage (uredo stage).
Figures 104-106. — Black rust of wheat, showing sori of teleutospores.
reddish-brown or reddish pustules, and is known as the " red
rust" (figs. 102, 103). Another form occurs in elongated
black pustules, and this form is the one known as the " black
rust" (figs. 104-107). These two forms occur on the stems,
blades, etc., of the wheat, also on oats, rye, and some of the
grasses.
221. Teleutospores of the black-rust form. — Scrape off some
portion of one of the black pustules (sori), tease it out in
water on a slide, and examine with a microscope, to see numer-
FUNGI: WHEAT RUST.
ous spores, composed of two cells, and having thick, brownish
walls as shown in fig. 108. Usually there is a slender brownish
stalk on one end. These spores are called teleutospores. They
are somewhat oblong or elliptical, a little constricted where the
septum separates the two cells, and the end cell varies from ovate
Fig. xo8.
Teleutospores of wheat rust,
showing two cells and the pedicel.
Fig. 107.
Head of wheat showing black vrust spots
on the chaff and awns.
Fig. 109.
Uredospores of wheat rust, one
showing remnants of the pedicel.
to rounded. The mycelium of the fungus courses between the
cells, just as is found in the case of the carnation rust, which
belongs to the same family (see Chapter XV).
222. TIredospores of the red-rust form. — If we make a
similar preparation from the pustules of the red-rust form we
shall see that instead of two-celled spores they are one-celled.
132
BOTANY.
The walls are thinner and not so dark in color, and they are
covered with minute spines. They have also short stalks, but
these fall away very easily. These one-
celled spores of the red-rust form are
called* " uredospores." The uredospores
and teleutospores are sometimes found in
the same pustule.
It was once supposed that these two
kinds of spores belonged to different plants,
but now it is known that the one-celled form,
the uredospores, is a form developed earlier
in the season
than the teleu-
tospores.
223. Cluster-
cup form on
the barberry.
— On the bar-
berry is found
still another
of the
Fig. no.
Barberry leaf with two
diseased spots, natural
size.
Fig. in.
Single spot
showing cluster
cups enlarged.
split margin.
Figures 153-155. — Cluster cup stage of wheat rust.
Fig.ua
Two cluster
cups more en-
larged, showing wheat rust, the
' ' cluster Cup
stage. The
pustules on the under side of the barberry leaf are cup-shaped^
the cups being partly sunk in the tissue of the leaf, while
the rim is more or less curved backward against the leaf, and
split at several places. These cups occur in clusters on the
affected spots of the barberry leaf as shown in fig. 1 1 1. Within
the cups numbers of one-celled spores (orange in color, called
aecidiospores) are borne in chains from short branches of the
mycelium, which fill the base of the cup. In fact the wall of
the cup (peridium) is formed of similar rows of cells, which,
instead of separating into spores, remain united to form a wall.
These cups are usually borne on the under side of the leaf.
FUNGI: WHEAT RUST.
133
For a fuller study of the wheat rust and of other fungi see the
author's larger " Elementary Botany," Chapters XX, XXI.
Wheat rust.
Fig. 113.
Section through leaf of barberry at point affected with the cluster-cup stage of the wheat
rust; spermagonia above, secidia below. (After Marshall-Ward.)
Synopsis.
A parasite on grains, grasses, and on the barberry.
Vegetative part of plant ; mycelium growing within the tissues
of the host.
Fruiting part of the plant.
1st. Red rust (one-celled spores in pustules on
blades and stems of the wheat).
2d. Black rust (two-celled spores in pustules
on the blades and stems of the wheat).
Y f I 3^- Cluster cup (one-celled spores in chains
within a structure called a peridium, or
cup on leaves and stems of barberry).
4th. Spermagonia (small flask-shaped bodies
accompanying the cluster cups, of un-
known function).
Material. — Dried stalks of wheat or oats with the black -rust spots ; dried
leaves with the red-rust spots ; leaves of the barberry with the cluster cups.
(If the barberry leaves cannot be obtained, another species of cluster cup may
be used to illustrate the cecidial stage, but it should be remembered that other
cluster cups are not connected with the life history of the wheat rust.)
For satisfactory studies of the cluster-cup stage, sections through the cup
should be made from fresh material, or sections already made may be pur-
chased from the supply companies.
Microscope, etc.
CHAPTER XXIII.
FUNGI (CONCLUDED): THE WILLOW MILDEW.
(Uncinula salicis.)
224. Description of the mildew. — The willow mildew belongs
to a very interesting group of the fungi known as the powdery
mildews. These mildews are very common on the leaves, and
even stems, flowers, and fruits, of various plants. It is a very
easy matter to find them during the summer or late autumn and
to press a number of the leaves to preserve for future study.
The mycelium grows on the outside of the parts of the host,
so that it gives a whitish, "mildewed" appearance to the
affected places. Very short branches (haustoria) from the
mycelium enter the epidermal cells of the host and draw nutri-
ment from xhe leaves or other parts, and supply the fungus with
the materials for growth. This nutriment is taken at the
expense of the host, and often considerable injury to it is thus
done, which results in a sickly appearance of the host, or even
in a deformity, the leaves or stems being curled or dwarfed.
Immense numbers of small, colorless spores (gonidia) are borne
in chains on some of the threads, and these piled up on the
surface of the leaf give it a powdered appearance.
After this powdery stage of the fungus has formed,
another kind of fruit of the fungus is developed. This may be
detected by numerous minute black specks seated on the white
mycelium, as shown in fig. 114. Each one of these black
specks is a fruit body.
134
FUNGI: THE WILLOW MILDEW.
135
Exercise 46.
225. The Willow Mildew. — Take dried leaves, or those freshly collected,
which show some of the whitish mycelium, and numerous black fruit bodies.
Fig. 114.
Leaves of willow showing willow mildew. The black dots are the fruit bodies (perithecia)
seated on the white mycelium.
Observe the white mycelium. Is it scattered unevenly over the surface of the
leaf, or does it form more or less circular spots? Is there any difference in
136 BOTANY.
the color or appearance of the leaf in the spots where the mycelium is
seated ? * Try to remove some of the mycelium with a needle, to see that
it consists of threads which are on the surface of the leaf.
Fruit bodies. Observe the minute black specks seated on the mycelium.
Are all of them black, or dark* in color? If there are any yellowish ones
how do they compare with the dark ones as to size ? How do they compare
as to age ? With a hand lens examine them more carefully. Can you see
any dark-colored threads extending out from the fruit body ? Can you see
their form ?
Demonstration 34.
226. The fruit bodies. — Place a drop of water on a glass slip. Touch the
point of a scalpel or knife to the water and then scrape the surface of the
leaf gently where there are a number of the black bodies. The capillarity of'
the water will hold some of the fruit bodies to the point of the knife. From
this tease off the fruit bodies with a needle into the drop of water on the
slip. Separate them well and put on the cover glass.
Let each pupil examine the fruit bodies under the microscope. Note the
form of surface markings and the appendages. Sketch.
227. The asci and spores which they contain.— Take this same prep-
aration, crush the fruit bodies by gently pressing on the cover glass above
them, until the fruit bodies are cracked open, and some of the sacs containing
the spores are pressed out (see fig. 116). Let the pupils examine and sketch
them.
The gonidia may be demonstrated by using leaves where the fruit bodies
are not abundant, but which possess an abundance of the mycelium (see
228. Fruit bodies of the willow mildew. — On the mycelium
there appear numerous black specks scattered over the affected
places of the leaf. These are the fruit bodies (perithecia).
When examined with a low power of the microscope, each one
is seen to be a rounded body, from which radiate numerous
* If the leaves are not old the portions where the mycelium is seated may
be more or less yellow, showing an injury ; but if the leaves are quite old
and nearly ready to fall, the green color may have disappeared more rapidly
from the unaffected parts of the leaf, for the fungus gives some stimulus to the
leaf, and often this is manifested by the green color remaining longer in the
affected parts of the old leaves.
FUNGI: THE IV I L LOW MILDEW.
137
filaments, the appendages. Each one of thes.e appendages is
coiled at the end into the form of a little hook. Because of
these hooked appendages this genus is called uncinula. This
rounded body is the perithecium.
229, Asci and ascospores, — \Yhile we are looking at a few of
these through the microscope with the low power, we should
press on the cover glass with a needle until we see a few of the
Fig. 115.
Willow mildew ; bit
of mycelium with
Fig. 116.
Fruit of willow mildew, showing hooked ap-
pendages. Genus uncinula.
Fig. 117.
Fruit body of an-
other mildew with
erect < conidiophores Figures 1,6, Ti7.-Perithecia (perithecium) dichotomous appen-
bearing chain of Of two powdery mildews, showing escape of dages O e n u s
gonidia; gonidium at { containing the spores from the crushed microsphaera.
left germinating. fruit bodies.
perithecia rupture. If this is done carefully we see several
small^ovate sacs issue, each containing a number of spores, as
shown in fig. 116. Such a sac is an ascus, and the spores are
ascospores.
'33
BOTANY.
Synopsis. —
Vegetative part of the plant : mycelium on the surface of
the host sends suckers (haustoria) into the cells of the
host. '
Propagative stage of the plant: short erect threads which
Willow mildew, j bear chains of spores (gonidia).
Fruiting part of the plant (perfect stage).
Perithecium with hooked appendages.
Perithecium contains sacs (asci).
The sacs contain the spores (ascospores).
Material. — Dried and pressed leaves of willow with the white mildew, also
older stages showing the numerous black "specks," the fruit bodies, of the
mildew. Other species of the mildew may be used if preferred.
Microscope, etc.
CHAPTER XXIV.
LIVERWORTS (HEPATIC^).
(Marchantia polymorpha.)
230. Form of marchantia. — The marchantia (M. polymorpha)
has been chosen for stud)7 because it is such a common and
easily obtained plant, and also for the reason that with com-
parative ease all stages of development can be obtained. It
illustrates also very well certain features of the structure of the
liverworts.
The plants are of two kinds, male and female. The two
different organs, then, are developed on different plants. In
appearance, however, before the beginning of the structures
which bear the sexual organs they are practically the same.
The plant forms a flattened, green, leaf-like body which lies
on the damp soil or clings closely to wet rock. It is shaped
somewhat like an irregular ribbon, the margins more or less
wavy, and the plant is branched in a forked manner as shown
in fig. 1 1 8. Upon the under side are numerous hair-like
bodies, the ' ' rhizoids, ' ' which serve the purpose of root hairs
in absorbing food solutions, and they also attach the plant to
the substratum. The growing point of the thallus is in the
little depression at the free end.
For fuller studies of the liverworts and for the sexual organs
see the author's larger " Elementary Botany/7 Chapters XXII
and XXIII.
Exercise 47.
231. Male plants. — Examine both surfaces of the "thallus" as the leaf-
like body of the liverwort is called. Note where the rhizoids are attached.
Sketch the plant, showing the rhizoids, the form of the thallus, and the um-
139
140 BOTANY.
hrella-shapecl bodies on the upper surface. Note that the expanded part
of this umbrella-shaped structure is crenate on the margin, giving it a lobed
appearance, and that these lobes radiate from the centre. Search for
little pits opening on the upper surface of these structures ; these are the
opening of the chambers where the antheridia are borne. With a hand lens
examine the upper surface of the thallus. Can you see that it is marked off
into diamond-shaped areas, with a minute opening in the centre of each ?
These openings are the stomates of the thallus. Observe that the central
line of the thallus is thicker than the margins. This is the midrib.
Exercise 48.
232. Female plants. — Study these in a similar way, and compare. The
thallus is very similar, the greater point of difference being in the umbrella-
shaped structures. Note that the expanded portion is more deeply lobed,
forming prominent rays. On the under surface observe the delicate hanging
fringes. Underneath these the archegonia are borne. If material with ripe
fruit is at hand preserved in formalin, observe the rounded capsules on short
stalks which protrude from beneath these curtains. Sketch and describe all
parts of the plant.
Exercise 49.
233. Sterile plants bearing cups and gemmae. — Study these in a similar
way. Note that the umbrella-shaped structures are absent. Observe the
minute cups on the upper surface. With a hand lens note the minute flat-
tened green bodies within the cups. These are the gemmae, or buds, and
serve as one means of propagating the plant.
Demonstration 35.
( May be omitted. )
234. Sexual organs. — The teacher may make demonstrations to show the
sexual organs, and the spores and elaters. For the antheridia section the
antheridial receptacle, and for the archegonia section the archegonial recep-
tacle. Unless one is familiar with methods of sectioning these structures, it
would be better to purchase prepared sections of these organs for the demon-
stration. See fig. 123.
Demonstration 36.
235. Spores and elaters. — When the fruit is ripe (see fig. 125) and the
spores and elaters are escaping some may be mounted. They may be
mounted in glycerine jelly. Such mounts will keep for a long time if cared
LIVERWORTS. 141
for, and will serve for successive years' study. Mounts may also be made
from material preserved in formalin. Tease out a few of the spores and
elaters from the capsule with needles, in a drop of alcohol on the glass slip*
Melt a bit of glycerine jelly on a cover glass and just as the alcohol is evap-
orating from the slide lower the glycerine with the cover over them. See
figure 126.
Spores and elaters from some other liverwort may be used if more
convenient.
236. Antheridial plants. — One of the male plants is figured
at 1 1 8. It bears curious structures, each held aloft by a short
stalk. These are the antheridial re-
ceptacles. Each one is circular, thick,
and shaped somewhat like a bi-convex
lens. The upper surface is marked by
radiating furrows, and the margin is
crenate. Then we note, on careful
examination of the upper
surface, that there are
numerous minute open-
ings. If we make a thin
section of this
structure per-
pendicular t o
its surface we
shall be able to
Male plant of marchantia bearing antheridiophores.
tery of its in-
terior. Here we see, as shown in fig. 119, that each one of
these little openings on the surface is an entrance to quite a
large cavity. Within each cavity there is an oval or elliptical
body, supported from the base of the cavity on a short stalk.
This is an antheridium, and one of them is shown still more
enlarged in fig. 120. This shows the structure of the anther-
idium, and that there are within several angular areas, which
are divided by numerous straight cross-lines into countless
tiny cuboidal cells, the sperm mother cells. Each of these
142
BOTANY.
changes into a swiftly moving body resembling a serpent with
two long lashes attached* to its tail.
Fig. 119-
Section of antheridial receptacle from male plant of Marchantia polymorpha, showing
cavities where the antheridia are borne.
237, Archegonial plants. — In fig. 122 we see one of the
female plants of marchantia. Upon this there are also very
curious structures, which remind one of miniature umbrellas.
Fig. 120.
Section of antheridium of mar-
chantia, showing the groups of
sperm mother cells.
Spermatozoids of marchantia,
uncoiling and one extended,
showing the two cilia.
The general plan of the archegonial receptacle is similar to that
of the antheridial receptacle, but the rays are more pronounced,
LIVERWORTS. 143
and the details of structure are quite different, as we shall see.
Underneath the arms there hang; down delicate fringed curtains.
If we make sections of this in the same direction as we did of
the antheridial receptacle, we shall be able to find what is
Fig. 122.
Marchantia polymorpha, female plants bearing archegoniophores.
secreted behind these curtains. Here we find the archegonia,
but instead of being sunk in cavities their bases are attached to
the under surface, while the delicate, pendulous fringes afford
them protection from drying.
144
BOTANY.
238. Sporogonium of liverworts. — If the sporogonium
(spore-case) of marchantia cannot be obtained those of any
other liverwort may be used.
239. Sporogonium of marchantia. — If
we examine the plant shown in fig. 124
we shall see oval bodies which stand out
between the rays of the female receptacle,
supported on short stalks. These are the
sporogonia, or spore-cases. We can see
that some of the spore-cases have opened,
the wall splitting down from the apex
in several lines. This is caused by the
drying of the wall. These toothlike
divisions of the wall now curl backward,
and we can see the yellowish mass of the
spores in slow motion, falling here and
there. It appears also as if there were
twisting threads which aided the spores
Fi I2 in becoming freed from the capsule.
Marchantia poiymorpha, 240. Spores and elaters. — If we take
archegomum with egg; /,
curtain which hangs down a bit of this mass of spores and mount
around the archegonia; *•,
egg; v, venter of archego- it in water for examination with the
nium ; «, neck of archego-
nium. microscope, we shall see that, besides
the spores, there are very peculiar thread-like bodies, the mark-
ings of which remind one of a twisted rope. These are very
long cells from the inner part of the spore-case, and their
walls are marked by spiral thickenings. This causes them in
drying, and also when they absorb moisture, to twist and curl
in all sorts of ways. They thus aid in pushing the spores out
of the capsule as it is drying.
241. How marchantia multiplies. — New plants of mar-
chantia are formed by the germination of the spores, and
growth of the same to the thallus. The plants may also be
multiplied by parts of the old ones breaking away by the action
of strong currents of water, and when they lodge in suitable
LIVERWORTS.
145
places grow into well-formed plants. As the th'allus lives from
year to year and continues to grow and branch the older por-
tions die off, and thus separate plants may be formed from a
former single one.
242, Buds, or gemmae, of marchantia.— But there is an-
other way in which marchantia multiplies itself. If we exam-
Fig. 124.
Archegonial receptacles of marchantia bearing ripe sporo-
gcnia. The capsule of the sporogonium projects outside,
while the stalk is attached to the receptacle underneath the
curtain. In the left figure two of the capsules have burst
and the elaters and spores are escaping.
Fig 125.
Section of archegpnial receptacle of Marchantia polymorpha ; ripe
sporogonia One is open, scattering spores and elaters; two are
still enclosed in the wall of the archegonium. The junction of the
stalk of the sporogonium with the receptacle is the point of attach-
ment of the sporophyte of marchantia with the gametophyte.
ine the upper surface of such a plant as that shown in fig. 127,
we shall see that there are minute cup-shaped or saucer-shaped
BOTANY.
vessels, and within them minute green bodies. When these
green buds. free themselves from the cups they come to lie on
one side and develop into new plants. It does not matter on
Fig. 126.
Elater and spore of marchantia. j/, spore ; me, mother cell of spores*
showing partly formed spores.
what side they lie, for whichever side it is, that will develop
into the lower side of the thallus, and will form rhizoids, while
the upper surface will develop the stomates.
LIVERWORTS.
'47
Fig. 127.
M-archantia plant with cupules and gemmae ; rhizoids below.
Synopsis.
Marchantia
(A liver-
wort).
Plant body ; flattened, ribbon-like, green, with rhizoids on
under surface ; grows in moist situations.
f 1st. Plant with buds in little cups.
The buds escape and propagate the plant.
2d. Male plants.
Antheridial receptacle.
Vegetative part. Antheridial cavities.
Three forms. \ Antheridium.
Spermatozoids.
3d. Female plants.
Archegonial receptacle.
Archegonium.
Egg.
/ Capsule wall.
Fruit capsule. \ Spores.
( Elaters.
Short stalk attaching fruit body to archego-
nial receptacle.
Fruiting part.
BOTANY.
Material and apparatus.— Freshly collected plants, or if these cannot be
had, plants preserved in 2% formalin, or in alcohol, may be used. Some
plants dry are often useful if they are not to be had in any other condition.
Plants with the cups and gemmae; male plants; and female plants.
For the study of the fruit bodies plants must be had either fresh (but this is
quite impossible since they ripen in June and July) or better, plants with ripe
fruit bodies may be preserved in 2% formalin.
For the demonstration of the sexual organs, and of the spores and elaters,
the teacher may make sections, or purchase sections of supply companies.
Hand lenses, or simple dissecting microscopes.
Microscope, etc., for demonstrations 35 and 36.
CHAPTER XXV.
MOSSES (MUSCI).
(Polytricbttm, or mnium.)
243. The moss plant. — We are now ready to take up the
more careful study of the moss plant. There are a great many
kinds of mosses, and they differ greatly from each other in the
finer details of structure. Yet there are certain general re-
semblances which make it convenient to take for study almost
any one of the common species in a neighborhood, which forms
abundant fruit. Some, however, are more suited to a first
study than others.
Those mosses in which there is a marked difference between
the male and female plants, like polytrichum, bryum, mnium,
etc., are most suitable for the purpose. The male plants of
these genera have the leaves at the end of the stem in a broad
rosette. Both male and female plants should be collected, and
the fruiting plants also. The latter bear above the leafy portion
a stalked capsule. Polytrichum (known as pigeon wheat moss)
is suggested here for the practical study, while mnium is here
used to illustrate the mosses. It will be found useful occa-
sionally to study a plant that is different from the one fully
illustrated in the book, since it gives the student an opportunity
for more independent work.
THE PIGEON WHEAT Moss (POLYTRICHUM).
Exercise 5O.
244. The fruiting plant. — Take entire plants, those with leafy stems
bearing the stalked capsule. Sketch the entire plant. Note the stem (axis)
and the three rows of leaves. Search for the rhizoids at the lower end of
the stem. What is their color ? Observe the capsule, its form.
149
ISO BOTANY.
Among the material searchJfor those capsules representing several different
ages. Very young ones are often collected when there appears to be nothing
but a slender stalk, the capsule not yet being fully developed. Search on the
capsule for the hairy hood, Known as a calyptra. Remove this; note its form.
Now at the end of the capsule note the conic lid (the operculum). Remove
this, or examine older capsules where the lid has fallen away. Note the
numerous teeth. When the lid is removed, are there any small granules
(the spores) escaping ? Compare the shape of the capsules of different ages.
Exercise 51 .
245. The male plants. — Note the broad rosette of leaves at the end of the
stem. Compare the arrangement of the leaves here with those lower down-
on the stem. Sketch. The antheridia (sing, antheridium) are borne in the
centre of the rosette.
246. The female plants. — Compare with the male plants : what is the
difference in the arrangement of the leaves ? Can you suggest why the
leaves are arranged differently in the two plants ?
Demonstration 37.
( May be omitted ivhen necessary. )
247. Demonstration of spores, etc. — The teacher can prepare mounts of
the spores, and of a portion of the mouth (peristome) of the capsule for study.
If it is desired also leaves may be examined under the microscope. The
leaves are made up of a single layer of cells, except at the middle line where
the cells are several layers thick, and long and narrow. The cells in the
middle line form the "midrib" of the leaf. The teacher can also make
sections through the ends of the male and female plants to demonstrate the
sexual organs, or prepared slides representing these may be purchased for
demonstration.
DESCRIPTION OF THE Moss, MNIUM.
248. Mnium. — We will select here the plant shown in fig.
128. This is known as a mnium (M. affine), and one or
another of the species of mnium can be obtained without much
difficulty. The mosses, as we have already learned, possess an
axis (stem) and leaf-like expansions, so that they are leafy-
stemmed plants. Certain of the branches of the mnium stand
upright, or nearly so, and the leaves are all of the same
size at any given point on the stem, as seen in the figure.
MOSSES.
There are three rows of these leaves, and this is true of most of
the mosses.
249. Habit of mnium. — The mnium plants usually form
quite extensive and pretty mats of green in
shady moist woods or ravines. Here and
there among the erect stems are prostrate
ones, with two rows of prominent leaves
so arranged that they remind one of some
of the leafy-stemmed liverworts. If we
examine some of the leaves of the mnium
we will see that the greater part of the
leaf consists of a single layer of green cells,
just as is the case in the leafy-stemmed
liverworts. But along the middle line is
a thicker layer, so that it forms a dis-
tinct midrib. This is characteristic of
Fig. 128.
Portion of moss plant of Mnium affine, showing two
sporogonia from one branch. Capsule at left has just
shed the cap or operculum ; capsule at right is shedding
spores, and the teeth are bristling at the mouth. Next
to the right is a young capsule with calyptra still attached;
next are two spores enlarged.
the leaves of mosses, and is one way in which they are sepa-
rated from the leafy-stemmed liverworts, the latter never having
a midrib.
152
BOTANY*
250. The fruiting moss plant. — In fig. 128 is a moss plant
" in fruit," as we say. Above the leafy stem a slender stalk
bears the capsule, and in this capsule are borne the spores.
251. Sporogonium of the moss. — The sporogonium (spore-
s ! case) of a moss is illustrated
in fig. 1,28. The sporo-
gonium is the portion repre-
sented above the leafy part,
and consists of a stalk and
capsule. This was devel-
oped from the fertilized egg.
Fig. 129.
Female plant (gametophyte) of a moss
Fig. 130.
Male plant (gametophyte) of a moss
(mnium), showing rhizoids below, and the (mnium) showing rhizoids below and the
tuft of leaves above which protect the
archegonia.
antheridia at the centre above surrounded
by" the rosette of leaves.
The capsule is nearly cylindrical, bent downward, and supported
on a long slender stalk.
153
• • • °
Upon the capsule is a peculiar cap, shaped like a ladle or
spatula, the calyplra.
252. Structure of the moss capsule. — A^the free end on
.the moss capsule as sho\Mi in !te case of mnium in fig. 128,
after the remnant of the archegonium falls away, there is seen
a conical lid whicfrfits closely over the end. When the capsule
is ripe this lid easily falls away, and can be brushed off, so that
it is necessary to handle the plants with care if is desired to
preserve this for study.
253. Opening of the capsule. — When the lid is brushed away
as the capsule dries more, we see that the end of the capsule
covered by the lid appears ' ' frazzled. " If we examine this end
with the microscope we will see that the tissue of the capsule
here is torn with great regularity, so that there are two rows of
narrow, sharp teeth which project outward in a ring around the
opening. If we blow our " breath " upon these teeth they will
be seen to move, and as the moisture disappears and reappears
in the teeth, they close and open the mpjpth of the capsule, so
sensitive are they to the changes in the humidity of the air.
In this way all of the spores are prevented to some extent from
escaping from the capsule at one time.
254. The male and female moss plants.-1— The two plants
of mnium, shown in figs. 129, 130, are quite different, as one
can easily see, and yet they belong to the same species. One
is a female plant, while the other is a male plant. The sexual
organs, then, in mnium, as in many others of the mosses, are
borne on separate plants. The archegonia are borne at the
end of the stem, and are protected by somewhat narrower
leaves which closely overlap and are wrapped together. They
are similar to the archegonia of the liverworts.
The male plants of mnium are easily selected, since the
leaves at the end of the stem form a broad rosette with the
antheridia, and some sterile threads packed closely together in
the centre. The ends of the mass of antheridia can be seen
with the naked eye, as shown in fig. 130.
154
BOTANY.
Synopsis
Moss plant
(Polytrichum
orffther moss).
Plant body, a small leafy stem, with rhizoids.
Protonema (branched green threads
which precede the leafy stem).
Male plants with a rosette of leaves at
the end.
Antheridia.
Spermatozoids.
Female plants, leaves closed together at
the end.
Archegonia.
Archegonium contains egg.
f Capsule wall.
( Fruit capusule.
1 Stalk.
Vegetative part
of plant.
Three forms.
Fruiting part.
| Lid.
Teeth at mouth.
i Spores.
(The hood is not a part of the capsule, but is the remains
of the archegonium.)
Material and apparatus. — The pigeon wheat moss (polytrichum) is an ex-
cellent one to study, but one should not be confined to this if it is easier to
collect other species which show strong differences between male and female
plants. Male and female plants, as well as plants with fruit, some of which
should possess the "hood," should be preserved dry, or in 2% formalin.
Free hand, or prepared, sections of the sexual organs.
Apparatus, the same as in Chapter XXIV.
CHAPTER XXVI.
FERNS (FILICINE^).
(The polypody , or Christmas fern.)
255. Importance of study of ferns. — In taking up the study
of the ferns we find plants which are very beautiful objects of
nature and thus have always attracted the interest of those who
love the beauties of nature. But they are also very interesting
to the student, because of certain remarkable peculiarities of
the structure of the fruit bodies, and especially because of the
intermediate position which they occupy within the plant king-
dom, representing in the two phases of their development the
primitive type of plant life on the one hand, and on the other
the modern type. We will begin our study of the ferns by tak-
ing that form which is the more prominent, the fern plant itself.
256. Selection of fern for study. — There are several ferns
which answer equally well for study. It is important to have
the entire plant, underground stem, roots, and leaves, and what
is of especial importance, some of the leaves should have the
"fruit dots/' The common polypody (Polypodium vulgare)
is widely distributed, and will be useful for the practical study,
even though the Christmas fern here is used to illustrate the
descriptive part. There should, however, be no necessity for
limiting the study to a certain species, since in one locality
one species can be more easily obtained, while in another
locality another species may be more convenient to study.
Exercise 52.
257. The fern plant. — Take entire plants, if the common polypody, note
the creeping stem (root-stock or rhizome), the numerous brown scales cov-
155
BOTANY.
ering it, the bud at the anterior end covered also with brown scales. Ob-
serve the numerous dark slender roots.
Note the leaves, some of them perhaps plain (sterile) on the under side,
while others have numerous circular brown or blackish dots, the fruit dots
where the sporangia (spore-cases) and spores are borne. Describe the form
of the leaf. Name the different parts. Sketch the entire plant. Sketch a
portion of the under side of the spore-bearing leaf, to show the fruit dots.
Compare the polypody with several other species of ferns if possible.
Exercise 53.
258. The scattering of the spores. — If the study is made at a time when
the ferns with spores just ripe cannot be collected out doors, get some leaves
from greenhouses. Take those leaves where the fruit dots appear quite
black, and under the lens the sporangia appear like shiny rounded black
bodies. Place a leaf on white paper in a dry room, with the under side
uppermost. In the course of an hour or earlier watch for showers of spores
which are scattered around the leaf, Sometimes in a dry room these begin
to scatter in the course of a few minutes. The success of this exercise will
depend on the material being in the right condition. After a little experi-
ence in collecting it is not difficult to get the right material.
Demonstration 38.
259. To show the sporangia. — These can be shown from sporangia
which are just ripe, or from older material which has been dried, or pre-
served in formalin or alcohol. Scrape off a few of the sporangia from the
"fruit dot." Mount them in water for examination under the microscope.
LET EACH STUDENT EXAMINE the form and structure. Sketch a sporan-
gium seen from the side. Name the different parts, the slender stalk, the
enlarged spore-case. In the spore-case make out a prominent row of cells
over the back and upper part (the annulus}, note, the "lip cells " in front,
one each side of the place where the sporangium opens. If there are any
spores in this preparation note and describe them ; sketch one also. If
there are none to be seen in the preparation made for the study of the
sporangium the teacher can mount some for study if desired.
To see the snapping of the sporangium fresh ripe material may be
mounted in water ; then draw under the cover glass some glycerine and
watch the result.
260. The Christmas fern. — One of the ferns which is very
common in the Northern States, and occurs in rocky banks and
woods, is the well-known Christmas fern '(Aspidium acrosti-
FEKNS.
'57
choides) shown in fig. 131. The leaves are the most prominent
part of the plant, as is the case with most if not all our native
ferns. The stem is very short and for the most part under the
surface of the ground, while the leaves arise
very close together, and thus form a rosette
as they rise and gracefully bend outward.
The leaf
is elongate
and r e -
minds one
somewhat
of a plume
with the
pinnae ex-
tending in
two rows
on oppo-
site sides
of the midrib. These
pinnae alternate with
one another, and at the
base . of each pinna is a
little spur which projects
upward from the upper
edge. Such a leaf is said
to be pinnate. While all
the leaves have the same
general outline, we notice
that certain ones, especi-
ally those toward the centre
of the rosette, are much
narrower from the middle portion toward the end. This is
because of the shorter pinnae here.
261. Fruit "dots" (sorus, indusium). — If we examine the
under side of such short pinnae of the Christmas fern we see that
Fig. 131.
Christmas fern (Aspidium acrostichoides)'.
158
B07ANY.
there are two rows of small circular dots, one row on either
side of the pinna. These are called the ' ' fruit dots, ' ' or sori
(a single one is a sorus). If we examine it with a low power
of the microscope, or with a pocket lens, we will see that there
is a circular disk which covers more or less completely very
minute objects, usually the
ends of the latter projecting
just beyond the edge if they
are mature. . This circular
disk is what is called the
indusium, and it is a special
outgrowth of the epidermis
of the leaf here for the pro-
tection of the spore-cases.
These minute objects un-
derneath are the fruit bodies,
which in the case of the
ferns and their allies are
called sporangia. This in-
dusium in the case of the
Christmas fern, and also in
some others, is attached to
the leaf by means of a short
slender stalk which is fast-
ened to the middle of the
under side of this shield.
262. Sporangia.— If we
section through the leaf at
Fig. 132.
Rhizome with bases of leaves, and roots of the one of the fruit dots, Or if
Christmas fern.
we tease off some of the
sporangia so that the stalks are still attached, and examine them
with the microscope, we can see the form and structure of
these peculiar bodies. Different views of a sporangium are
shown in fig. 137. The slender portion is the stalk, and the
larger part is the spore-case proper. We should examine the
FEK.VJ. 1 59
structure of this spore-case quite carefully, since it will help
Uo to understand better than we otherwise could the remarkable
operations which it performs in scattering the spores.
263. Structure of a sporangium. — If we examine one of the
sporangia in side vi<.w as shown in fig. 137, we note a promi-
nent row of cells which extend around the margin of the dorsal
edge from near the attachment of the stalk to the upper front
angle. The cells are prominent because of the thick inner
walls, and the thick radial walls which are perpendicular to the
inner walls. The walls on the back of this row and on its sides
are very thin and membranous. We should make this one
Fig. 133-
Rhizome of sensitive fern (Onoclea sensibilisX
carefully, for the structure of these cells is especially adapted to
a special function which they perform. This row of cells is
termed the annulus, which means a little ring. While this is
not a complete ring, in some other ferns the ring is nearly com-
plete.
264. The lip cells. — In the front of the sporangium is another
peculiar group of cells. Two of the longer ones resemble the
lips of some creature, and since the sporangium opens between
them they are sometimes termed the lip cells. These lip cells
i6o
BOTANY.
are connected with the upper end of the annulus on one side and
with the upper end of the stalk on the other side by thin walled
cells, which may be termed connec-
tive cells, since they hold each lip cell
to its part of the opening sporangium.
The cells on the side of the sporangium
are also thin-walled. If we now ex-
amine a sporangium from the back,
or dorsal edge as we say, it will appear
as in the left-hand figure. Here we
can see how very prominent the annu-
Under sidf o'f 'pLa of Aspi- 1US ^ Tt Pr°JeCtS bey°nd the SUrfaCC °f
doMson)nulOSUm showmg fruit the other cells of the sporangium. The
spores are contained inside this case.
265. Opening of the sporangium and dispersion of the
spores. — If we take some fresh fruiting leaves of the Christmas
Fig. 135-
Four pinnae of adiantum, showing recurved margins which cover the sporangia.
fern, or of any one of many of the species of the true ferns just at
the ripening of the spores, and place a portion of a leaf on a piece
of white paper in a dry room, in a very short time we shall see
that the paper is being dusted with minute brown objects which
fly out from the leaf. Now if we take a portion of the same
FEXNS.
161
leaf and place it under the low power of the microscope, so
that the full rounded sporangia can be seen, in a short time we
note that the sporangium opens, the upper half curls backward
as shown in fig. 138, and soon it snaps quickly, to near its
former position, and the spores are at the same time thrown for
a considerable distance. This movement can sometimes be
seen with the aid of a good hand lens.
266. How does this opening and snapping of the sporan-
gium take place ? — We are now more curious than ever to see
just how this opening and
how the snapping of the
sporangium takes place.
We should now mount
some of the fresh sporangia
in water and cover with a
cover glass for microscopic
examination. A drop of
glycerine should be placed
at one side of the cover
glass on the slip so that
the edge of the glycerine
will come in touch with
the water. Now as one
looks through the micro-
scope to watch the sporan-
gia, the water should be
drawn from under the cover
glass with the aid of some
bibulous paper, like filter Fig. 136.
paper placed at the edffe .Section through sorus of Polypodium vulgare
UU6C showing different stages of sporangium, and one
of the cover glass on the multicellular caPitate Eair-
opposite side from the glycerine. As the glycerine takes the place
of the water around the sporangia it draws the water out of the
cells of the annulus, just as it took the water out of the cells of
the spirogyra as we learned some time ago. As the water is
1 62
BOTANY.
drawn out of these cells there is produced a pressure from with-
out, the atmospheric pressure upon the glycerine. This causes
the walls of these cells of the annulus to bend inward, because,
as we have already learned, the glycerine does not pass through
the \valls nearly so fast as the water comes out.
267. Working of the annulus. — Now the structure of the cells
of this annulus, as we have seen, is such that the inner walls and
the perpendicular walls are stout, and consequently they do not
Fig. 137-
Rear, side, and front views of fern sporangium. </, <?, annulus ; a, lip cells.
bend or collapse when this pressure is brought to bear on the out-
side of the cells. The thin membranous walls on the back (dorsal
walls) and on the sides of the annulus, however, yield readily to
the pressure and bend inward. This, as we can readily see, pulls
on the ends of each of the perpendicular walls, drawing them
closer together. This shortens the outer surface of the annulus
and causes it to first assume a nearly straight position, then curve
backward until it quite or nearly becomes doubled on itself.
FERNS.
I63
The sporangium opens between the lip cells on the front, and the
lateral walls of the sporangium are torn directly across. The
greater mass of spores are thus held in the upper end of the
open sporangium, and when the annulus has nearly doubled on
itself it suddenly snaps back again in position. While treating
&**~
--- ~,^
..^^W^^
s*-^-^ " - ftiNP- • S.
«$^ 0^% " &**r^ ^ :A^ ; ^~
\s O ' - " ^ x^x^ ^ ^
0^_,^ ^N^N
g^^^£^~^'
-;*^^3^m^^
Fig. 138. .
Dispersion of spores from sporangium of Aspidium acrostichoides, showing different
stages in the opening and snapping of the annulus.
with the glycerine we can see all this movement take place.
Each cell of the annulus acts independently, but often they all
act in concert. When they do not all act in concert, some of
them snap sooner than others, and this causes the annulus to
snap in segments.
164 BOTANY.
268. The movements of the sporangium can take place in
old and dried material. — If we have no fresh material to study
the sporangium with, we can use dried material, for the move-
ments of the sporangia can be well seen in dried material, pro-
vided it was collected at about the time the sporangia are
mature, that is at maturity, or soon afterward. We take some
of the dry sporangia (or we may wash the glycerine off those
which we have just studied) and mount them in water, and
quickly examine them with a microscope. We notice that in
each cell of the annulus there is a small sphere of some gas.
The water which bathes the walls of the annulus is absorbed by
some substance inside these cells. This we can see because of
the fact that this sphere of gas becomes smaller and smaller
until it is only a mere dot, when it disappears in a twinkling.
The water has been taken in under such pressure that it has
absorbed all the gas, and the farther pressure in most cases
closes the partly opened sporangium more completely.
269. The annulus can snap several times. — Now we should
add glycerine again and draw out the water, watching the
sporangia at the same time. Wre see that the sporangia which
have opened and snapped once will do it again. And so they
may be made to go through this operation several times in suc-
cession. We should now note carefully the annulus, that is,
after the sporangia have opened by the use of glycerine. So
soon as they have snapped in the glycerine we can see those
minute spheres of gas again, and since there was no air on the
outside of the sporangia, but only glycerine, this gas must, it
is reasoned, have been given up by the water before it was all
drawn out of the cells.
This movement of the annulus is a very effective provision
for the mechanical distribution of the spores of ferns. The
successive periods of wet and dry weather, or of damp or dry
air, when the sporangia are mature serves to open the sporan-
gium successively so that all the spores are scattered. This
opening and closing probably goes on for a considerable time
fEJtNS.
I65
after the dispersal of the spores; for material which has been
dried for nearly twenty years has been used to show the
snapping of the sporangium. The sporangia which remain on
the leaves out-doors snap so often with the changes of the
weather that the annulus is literally worn out.
Synopsis.
Fern plant.
Root.
Stem.
Leaf. H
Sterile leaves. 1
Petiole.
Lamina.
{ Petiole.
Fertile leaves, i.e.,
spore-bearing
leaves.
Lamina.
' Fruit dots (sorus).
I n d u s i u m when
present.
Sporangium.
Spores.
Material and apparatus. — Entire plants with the root stock, and some of
the leaves with the fruit dots, may be preserved dry.
Portions of the leaves with the fruit dots, at the time the spores have just
matured, but have not opened, may be preserved in 2% formalin. If possi-
ble, for the study of the opening of the sporangia obtain fresh material of
the mature sporangia. They may often be obtained from greenhouses, and
the leaf with the fruit dots before the sporangia have opened should be im-
mersed in water as they are taken to the laboratory or in a very damp moist
chamber, since the dry air of the room soon causes them to open and scatter
the spores.
Apparatus, the same as in Chapter XXIV.
Glycerine.
CHAPTER XXVII.
FERNS — CONCLUDED.
THE SEXUAL STAGE OF FERNS.
270. THIS CHAPTER is LARGELY FOR READING AND FOR REFER-
ENCE, though the teacher should endeavor to give demonstra-
tions of the sexual organs, in their position on the under side
of the prothallium, and also sections to show the structure.
Prepared slides may be purchased for the purpose if it is not
possible to obtain the material for making them. Prothallia
may be grown by sowing the spores of ferns collected during the
summer and saved in paper bags. If possible, a gardener in a
greenhouse where ferns are grown should be consulted. Where
they cannot be grown, it may be possible to purchase the pro-
thallia also for study. When these can be obtained the student
should make as careful an examination of the prothallium as
possible before they are examined under the microscope.
Exercise 54.
271. Prothallium. — Note the small size of the prothallium, its form,
color, delicate texture. Upon the under side observe the rhizoids. At
which end of the prothallium are the rhizoids attached ? With the aid of a
hand lens can you see any other projections from the under side of the pro-
thallium ? Where are they located? Sketch a prothallium showing the
under side and all the parts that can be seen with the aid of a hand lens.
Demonstration 39.
272. To show the sexual organs attached to the under surface of the
prothallium. Mount a prothallium with the under side uppermost in water
on a glass slip, and prepare for examination with the microscope. Study
with the low power of the microscope. Near the sinus of the heart-shaped
166
FERNS. 167
prothallium look for conic projections, the archegonia (see fig. 139) ; among
the rhizoids look for smaller but more numerous, rounded projections, the
antheridia. Compare the prothallium with the thallus of marchantia.
Sketch a prothallium under the low power of the microscope if there is time.
Among the prothallia search for some showing the young fern plant.
Demonstration 4O.
273. To show the structure of the sexual organs of ferns. Make thin
sections lengthwise of the prothallium along the middle line. These are
best made in collodion or paraffin, and mounted in balsam. If the teacher
has not the apparatus for making them, prepared slides may be purchased
for the demonstration. Let the pupils sketch the structure of an antheridium
and archegonium (see paragraphs 281 and 282), and name the parts.
If there is time and material the teacher may demonstrate young pro-
thallia soon after the germination of the spores.
The following description of the sexual stage of ferns is for
reading and study.
For further studies on the gametophyte phase of ferns, see
the author's larger " Elementary Botany," Chapter XXVI.
274. Sexual stage of ferns. — We now wish to see what the
sexual stage of the ferns is like. Judging from what we have
found to take place in the liverworts and mosses we would infer
that the form of the plant which bears the sexual organs is
developed from the spores. This is true, and if we should
examine old decaying logs, or decaying wood in damp places in
the near vicinity of ferns, we would probably find tiny, green,
thin, heart-shaped growths, lying close to the substratum.
These are also found quite frequently on the soil of pots in
plant conservatories where ferns are grown. Gardeners also in
conservatories usually sow fern spores to raise new fern plants,
and usually one can find these heart-shaped growths on the sur-
face ot the soil where they have sown the spores. We may call
the gardener to our aid in finding them in conservatories, or
even in growing them for us if we cannot find them outside.
In some cases they may be grown in an ordinary room by keep-
ing the surfaces where they are growing moist, and the air also
moist, by placing a glass bell jar over them.
l68 BOTANY.
275. The prothallium.— In fig. 139 is shown one of these
growths enlarged. Upon the under side we see numerous
thread-like outgrowths, the rhizoids, which attach the plant to
the substratum, and which act as organs for the absorption of
nourishment. The sexual organs are borne on the under side
also. This heart-shaped, flattened, thin, green plant is the
Fig. 139.
Prothallium of fern, under side, showing rhizoids, antheridia scattered among and near
them, and the archegonia near the sinus.
prothallium of ferns, and we should now give it more careful
study, beginning with the germination of the spores.
276. Spores. — We can easily obtain material for the study of
the spores of ferns. The spores- vary in shape to some extent.
Many of them are shaped like a three-sided pyramid. One of
these is shown in fig. 140. The outer wall is roughened, and
on one end are three elevated ridges which radiate from a given
point. A spore of the Christmas fern is shown in fig. 141.
The outer wall here is more or less winged.
FEKNS.
169
Fig. 140.
Spore of Pteris serru-
lata showing the three-
rayed elevation along the
side of which the spore
wall cracks during germi-
In figs. 142, 143
277. Germination of the Spores. — After the spores have been
sown for about one week to ten days we should mount a few in
water for examination with the microscope in order to study the
early stages. If germination has begun, we find that here and
there are short slender green threads, in
many cases attached to brownish bits, the
old walls of the spores. Often one will sow
the sporangia along with the spores, and
in such cases there may be found a number
of spores still within the old sporangium
wall that are germinating, when they will
appear as in fig. 142.
278. Protonema. -- These short green
threads are called protonemal threads, or
protonema, which means a first thread, and
it here signifies that this short thread only
precedes a larger growth of the same object.
are shown several stages of germination of different spores.
Soon after the short germ tube emerges from the crack in the
spore wall, it divides by the formation of a cross-wall, and as it
increases in length other cross-walls are formed.
But very early in its growth we see that a slender
outgrowth takes place from the cell nearest the
old spore wall. This slender thread is colorless,
and is not divided into cells. It is the first rhiz-
oid, and serves both as an organ of attachment
for the thread, and for taking up nutriment.
279. Growth of the pro-thallium. — Very soon,
if the sowing has not been so crowded as to
prevent the young plants from obtaining nutri-
ment sufficient, we will see that the end of this
protonema is broadening, as shown in fig. 143. This is done
by the formation of the cell walls in different directions. It
now continues to grow in this way, the end becoming broader
and broader, and new rhizoids are formed from the under surface
Fig. 141.
Spore of Aspidi-
um acrostichoides
with winged ex-
ospore.
BOTANY.
of the cells. The growing point remains at the middle of the
advancing margin, and the cells which are cut off from either
side, as they become old, widen out.
In this way the ' ' wings, ' ' or margins
of the little, green, flattened body, are
Fig. 142.
Germinating spores of
Pteris aquilina still in the
sporangium.
Fig. 143-
Young prothallium of a fern (nipho-
bolus).
in advance of the growing point, and the object is more or less
heart-shaped, as shown in fig. 139. Thus we see how the
prothallium of ferns is formed.
280, Sexual organs of ferns. — If we take ojie of the prothallia
of ferns which have grown from the sowings of fern spores, or
one of those which may be often found growing on the soil of
pots in conservatories, mount it in water on a slip, with the
FERNS.
171
under side uppermost, we can then examine it for the sexual
organs, for these are borne in most cases on the under side.
Fig. 144. Fig. 145.
Section of antheridia showing sperm cells, and spermato- Different views of spermatozoids;
zoids in the one at the right. in a quiet condition ; in motion
(Adiantum concmnum).
281. Antheridia. — If we search among the rhizoids we see
small rounded elevations as shown in figure 139 scattered
over this portion of the prothallium. These are the antheridia.
If the prothallia have not been watered for a day or so, we may
have an opportunity of seeing
the spermatozoids coming out
of the antheridium, for when
the prothallia are freshly placed
in water the cells of the antheri-
dium absorb water. This presses
on the contents of the antheri-
dium and bursts the cap cell if
the antheridium is ripe, and all
the spermatozoids are shot out.
We can see here that each one
is shaped like a screw, with the
coils at first closed. But as the
spermatozoid begins to move
this coil opens somewhat and
Fig. 146.
Archegonium of fern. Large cell in
the venter is the egg, next is the ventral
canal cell, and in the canal of the neck
are two nuclei of the canal cell.
by the vibration of the long cilia which are on the smaller end it
whirls away. In such preparations one may often see them
spinning around for a long while, and it is only when they
gradually come to rest that one can make out their form.
172
BOTANY.
282. Archegonia. — If we now examine closely, on the thicker
part of the under surface of the prothallium, just back of the
45
Fig. 147.
Mature and open archegonium of fern (Adiantum cuneatum) with spermatozoids making
their way down through the slime to the egg.
"sinus," we may see longer
stout projections from the sur-
face of the prothallium. These
are shown in fig. 139. They are
the archegonia. One of them
in longisection is shown in fig.
146. It is flask-
shaped, and
the broader
portion is sunk
in the tissue of
the prothal-
lium. The egg
ap
is in the larger Fig. 148.
rt T h P Fertilization in a fern
Pai u e (marattia). s/>, spermato-
cri«rmat^-7rn'rlc zoid fusing with the nu-
spermatozoidscleus of t^e egK (After
Fig. 149.
Young plant of Pteris serrulata still
attached to prothallium.
when they are Campbell.)
swimming around over the under surface of the prothallium
FEXNS.
173
come near the neck, and here they are caught in the viscid
substance which has oozed out of the canal of the archegonium.
From here they slowly swim down the canal, and finally one
sinks into the egg, fuses with the nucleus of the latter, and the
egg is then fertilized. It is now ready to grow and develop into
the fern plant. This brings us back to the sporophyte, which
begins with the fertilized egg.
Synopsis.
Sexual stage.
Prothallium.
(Corresponds to the
vegetative part
of the liverwort
and moss.)
Flattened, green, heart-shaped growth, with rhizoids
underneath.
Sexual organs, under side of prothallium.
Antheridium.
( Wall.
( Sperm atozoids.
Archegonium. j WalL
1 Egg-
Material and apparatus. — Prothallia of ferns, entire ; they are often found
growing in soil of pots in greenhouses where ferns are grown. Or they
may be grown by sowing the spores.
For demonstrations of the structure of the sexual organs the teacher can
make sections, or permanent ones may be obtained from supply companies.
Apparatus, same as in Chapter XXIV.
CHAPTER XXVIII.
HORSETAILS (EQUISETINEyE).
(The field equisetum.)
283. Equisetum is related to the ferns. — Among the rela-
tives of the ferns are the horsetails, so called because of the
supposed resemblance of the branched stems of some of the
species to a horse's tail, as one might infer from the plant
shown in fig. 154. They do not bear the least resemblance to
the ferns which we have been studying. But then relationship
in plants does not depend on mere resemblance of outward form,
or of the prominent part of the plant.
The field equisetum (Equisetum arvense) is a good one to
study. If desired another one may be used for comparison, the
scouring rush, or shave grass (E. hyemale).
Exercise 55.
THE FIELD EQUISETUM.
284. Fertile shoots. — The material should show the underground stem.
Note the underground stem, its branching, color ; the connection of the up-
right fertile shoot with it. Note the roots. What is the color of the fertile
shoot ? Is there much chlorophyll ?
Observe the nodes (joints) of the stem, the membranous crown (leaves)
around each node, the character of the margin of this crown. Study the
internodes, note the marking into ridges and furrows. What is the relation
of the ridges and furrows of one node with those of each adjacent node ?
What is the relation of the points of the leaves with the ridges ? Sketch a
fertile shoot.
285. The fruiting spike.— The fruiting spike at the end of the shoot.
Observe the numerous disks which are also arranged in whorls. Tease off
174
HORSETAILS. 1 75
some of these from the shoot. Note the short stalk ; how is this stalk at-
tached? Describe the sacs underneath. (These are the spore-cases.)
Sketch a spore-bearing leaf.
If some of the spores are at hand which fall out of the spore-cases when
the sporangia dry, examine them under a hand lens ; at the same time
breathe upon them. What happens ?
286. The sterile shoot. — Compare the sterile shoots with the fertile shoots.
Note the leaves arranged in the same way, but smaller. Note the branch-
ing of the plant and the arrangement of the branches. Are there leaves on
the branches ? Describe them. Sketch a sterile shoot. What is the color
of the sterile shoot ? In what part of the plant does the chlorophyll lie ?
In what part of the plant does the process of starch formation (or photo-
synthesis) take place ? ~
Compare the scouring rush (E. hyemale) if there is time.
Demonstration 41.
287. Spores and elaters. — Mount some of the spores of equisetum on a
dry glass slip. Let each pupil examine them under the microscope, sketch
and describe the form ; breathe lightly on them and watch the result.
288. The field equisetum. Fertile shoots. — Fig. 150 repre-
sents the common horsetail (Equisetum arvense). It grows in
moist sandy or gravelly places, and the fruiting portion of the
plant (for this species is dimorphic), that is the portion which
bears the spores, appears above the ground early in the spring.
It is one of the first things to peep out of the recently frozen
ground. This fertile shoot of the plant does not form its
growth this early in the spring. Its development takes place
under the ground in the autumn, so that with the advent of
spring it pushes up without delay. This shoot is from 10 to
20 cm. high, and at quite regular intervals there are slight
enlargements, the nodes of the stem. The cylindrical portions
between the nodes are the internodes. If we examine the region
of the internodes carefully we note that there are thin mem-
branous scales, more or less triangular in outline, and connected
at their bases into a ring around the stem. Curious as it may
seem, these are the leaves of the horsetail. The stem, if we
examine it further, will be seen to possess numerous ridges
BOTANY.
which extend lengthwise and which alternate with furrows.
Further, the ridges of one node alternate with those of the
internode both above and below. Likewise the leaves
of one node alternate with those of the nodes both
above and below.
289, Sporangia. — The end of this fertile shoot we
see possesses a cylindrical to conic enlargement. This
is the fertile spike, and we note that its surface is
marked off into regular areas if the spores have not
yet been disseminated. If we dissect off a few of
these portions of the fertile spike, and examine one
of them with a low magnifying power, it will appear
like the fig. 151. We see here that the angular area
is a disk-shaped' body, with a stalk attached to its
inner surface, and with several long sacs projecting
from its inner face parallel with the stalk and surround-
ing the same. These elongated sacs are
the sporangia, and the disk which bears
them, together with the stalk which at-
taches it to the stem axis, is the sporo-
phyll, and thus belongs to the leaf series.
These sporophylls are borne in close
whorls on the axis.
290. Spores. — When the spores are
ripe the tissue of the sporangium be-
comes dry, and it cracks open and the
spores fall out. In fig. 152 we see that
the spore is covered with a very singular coil which
WThen the spore dries this un-
Merely breathing
151.
Peltate sporo-
phyll of equise-
tum (side view)
showing sporan-
gia on under side.
15°-
Portion of
fertile plant jies close to the wall.
o f Equise-
tum arvense, coils and thus rolls the spore about.
whorls of upon these spores is sufficient to make them perform
leaves and
the fruiting very curious evolutions bv the twisting: of these four
spike.
coils which are attached to one place of the wall.
They are formed by the splitting up of an outer wall of the
spore.
HORSETAILS.
177
291. Sterile shoot of the common horsetail. — When the
spores are ripe they are soon scattered, and then the fertile
Fig. 152.
Spore of equisetutn
with elaters coiled up.
Fig. 153-
Spore of equisetum with elaters un-
coiled.
shoot dies down. Soon afterward, or even
while some of the fertile shoots are still in
good condition, sterile shoots of the plant
begin to appear above the ground. One of
these is shown in fig. 154. This has a
much more slender stem and is provided
with numerous branches. If we examine
the stem of this shoot, and of the branches,
we shall see that the same kind of leaves are
present and that the markings on the stem
are similar. Since the leaves of the horsetail
are membranous and not green, the stem
is green in color, and here the process of
starch formation goes on. These green
shoots live for a great part of the season,
building up material which is carried down
into the underground stems, where it goes
to supply the forming fertile shoots in the
fall. On digging up some of these plants
we see that the underground stems are often
of great extent, and that both fertile and
sterile shoots are attached to one
and the same.
292. The scouring rush, or shave
grass. — Another common species of
horsetail in the Northern States grows
Fig. 154-
Sterile plant of horsetail (Equi-
178 BOTANY.
on wet banks, or in sandy soil which contains moisture along
railroad embankments. It is the scouring rush (E. hyemale), so
called because it was once used for polishing purposes. This
plant like all the species of the horsetails has underground stems.
But unlike the common horsetail, there is but one kind of aerial
shoot, which is green in color and fertile. The shoots range as
high as one meter or more, and are quite stout. The new
shoots which come up for the year are unbranched, and bear
the fertile spike at the apex. When the spores are ripe the
apex of the shoot dies, and the next season small branches may
form from a number of the nodes.
293. Gametophyte of equisetum. — The spores of equisetum
have chlorophyll when they are mature, and they are capable
of germinating as soon as mature. The spores are all of the
same kind as regards size, just as we found in the case of the
ferns. But they develop prothaliia of different sizes, according
to the amount of nutriment which they obtain. Those which
obtain but little nutriment are smaller and develop only
antheridia, while those which obtain more nutriment become
larger, more or less branched, and develop archegonia. This
character of an independent prothallium (gametophyte) with
the characteristic sexual organs, and the also independent
sporophyte, with spores, shows the relationship of the horsetails
with the ferns. We thus see that these characters of the repro-
ductive organs, and the phases and fruiting of the plant, are
more essential in determining relationships of plants than the
mere outward appearances.
HORSETAILS.
179
Synopsis.
The field
equisetum
Root.
Shoot.
C Underground stem cr rhizome.
Sterile shoot (branched, green, later than the fertile
shoot). -
Fertile shoot (early in the spring).
f Stem with nodes and internodes, crown of mem-
branous pointed leaves at the nodes.
1 Fruiting spike.
Whorls of peltate spore-bearing leaves.
Several sporangia on inner side of the
sporophylls.
Sporangium contains
Spores each with four elaters.
(The prothallium is not described here.)
Material and apparatus. — Entire plants including the underground root
stock may be preserved dry. The fertile shoots appear earlier, and should
be collected just as they are appearing from the ground ; the sterile shoots
should be collected later when they are well formed.
Apparatus, the same as in Chapter XXIV.
CHAPTER XXIX.
QUILLWORTS (ISOETES).
Exercise 56.
294. The isoetes plant. — Sketch an entire plant. Only the leaves (resem-
bling " quills ") and the roots c^n be seen. Note the relation of the leaves,
how they overlap. Remove a few. Describe and sketch the form. Note
the thickened base, its shape like a spoon.
Upon the inner side of the thickened base note the circular depression of
a different texture. This is the spore-case. Note the thin overlapping
membrane around the edge of the spore-case. Just above the sporangium
note the small appendage. Observe the thin outer wall of the spore-case ;
that through this in many cases the large spores can be seen in many of
the spore-cases, especially the outer ones.
Section a plant longitudinally, or examine one that has been split into
halves longitudinally, in order to see the attachment of the leaves, and to
see the short stem. Note here also the spores in the spore-cases ; also the
cross-strands of tissue dividing the spore-cases into chambers.
Tease open several of the sporangia to expose the spores. Note the large
spores in some ; the small spores in others.
Demonstration 42.
295. Two kinds of spores. — Spores of each kind may be mounted in water
for demonstration. Let each pupil sketch and describe one of each kind.
It is an important thing for the student to know one of the fern-like pla-nts
which bear the two kir.ds of spores, as it helps one to understand the two
different kinds of spores in the pines and flowering plants.
296. Habit of isoetes. — The quilhvorts, as they are popularly
called, are very curious plants. They grow in wet marshy places.
They receive their name from the supposed resemblance of the
J8Q
QUILLWORTS. l8l
leaf to a quill. Fig. 155 represents one of these quillworts
(Isoetes engelmannii). The leaves are the prominent part of the
plant, and they are about all that can be seen except the roots,
without removing the leaves.
Each leaf, it will be seen, is long
and needle-like, except the basal
part, which is expanded, not very
unlike, in outline, a scale of an
onion. These expanded basal
portions of the leaves closely
overlap each other, and the very
short stem is completely covered
at all times. Fig. 157 is from
a longitudinal section of a quill-
wort. It shows the form of the
leaves from this view (side view),
and also the general outline
of the short stem, which is tri-
angular. The stem is therefore
a very short object.
297. Sporangia of isoetes. —
If we pull off some of the leaves
of the plant we see that they are
somewhat spoon-shaped as in
fig. 156. In the inner surface
of the expanded base we note a
circular depression which seems
to be of a different texture from
the other portions of the leaf.
This is a sporangium. Beside
the spores on the inside of the
sporangium, there are strands of Fig. I5S.
sterile tissue which extend across Isoetes' mature plant'
the cavity. This is peculiar to isoetes of all the members of
the class of plants to which the ferns belong, but it will be re-
182
BOTANY.
membered that sterile strands of tissue are found in some of
the liverworts in the form of elaters.
298. Microspores and macrospores. — The spores of isoetes are
of two kinds, small ones (microspores) and large ones (macro-
spores). When one kind of spore is borne in a sporangium
usually all in that sporangium are of the same kind, so that certain
sporangia bear microspores, and others bear macrospores. But
Fig. 156.
Base of leaf of isoetes,
showing sporangium with
macrospores. (Isoetes en-
gelmannii).
(\
Fig. 157-
Section of plant of Isoetes engelmanii, showing
cup-shaped stem, and longitudinal sections of the
sporangia in the thickened bases of the leaves.
it is not uncommon to find both kinds in the same sporangium.
When a sporangium bears only microspores the number is much
greater than when one bears only macrospores.
For a discussion of the club mosses (lycopodium and selagi-
nella) and for a comparison of the ferns and fern-like plants,
see the author's larger " Elementary Botany, " Chapters XXVIII
and XXX.
QUILLWORTS. 183
Synopsis.
f Root.
Quillwort
j Short stem.
Leaves long, quill-like.
Sporangium in base of each leaf.
Some sporangia with small spores.
Some sporangia with large spores.
(The prothallium is not described here.)
Material. — Entire plants, some dried, and others preserved in alcohol.
CHAPTER XXX.
GYMNOSPERMS.
THE WHITE PINE.
Exercise 57.
299. The long shoots of the pine. — Take a branch which shows the long
shoots, and several whorls of branches. Note the terminal shoot ; if in early
summer observe the scale-like leaves borne on the long shoots. Note that
the branches belong to the long shoots, and that they are arranged in a whorl
at the end of each year's growth. (This whorl is a false one.)
300. The short branches. — On the long shoots note the short branches
ending in a tuft of long green needle-like leaves. Note the short brownish
scale-like leaves on the short shoots below where the needles are attached.
In early spring if there are any pines in the vicinity note the growth of the
long shoots, and the colorless scale leaves on them, and the appearance of the
new green leaves on the new short shoots. How long do the green leaves
remain on a pine ?
Exercise 58.
301. Mature cones. — Note the form of the cone, the scales spread apart
when dry. (Before the seeds are ripe the scales closely overlap.) Note the
arrangement of the scales in spirals. Remove a few scales. Note the seeds
attached to the inner lower end of the scale, unless they have split off.
Sketch the form of a scale showing the seeds attached. Sketch a detached
seed, showing the wing-like appendage which splits off from the inner
part of the scale.
302. Young female cones. — Note the small size as compared with the
mature cones. Observe that the scales have the same arrangement as in the
mature cones. Sketch one. If you have an opportunity to see the young
cones on the tree just at the time of pollination, make a note of their posi-
tion, and the position of the scales. Some time after pollination note the
position of the cones, say any time during the summer, and the position of
184
G YMNOSP&KMS. 1 8 5
the scales. Why are the cones and scales in these different positions at these
different times ?
Remove several scales and study them carefully. Sketch the form of one
showing both sides. Upon the outer side note a small appendage (cover
scale ; if there are spruces at hand compare the difference in size of the
cover scale of the pine and spruce).
Upon the inner side note the two oval bodies at the two lower angles.
These are the ovules, and correspond to the large sporangia. Note care-
fully a forceps-like appendage at the lower end of each ovule ; a little de-
pression between them. This is the place where the pollen is drawn up
after pollination.
Observe that the seeds are developed at this same point on the scale, and
that the seed is formed from a later growth of the ovule and its parts.
Observe also that the ovules and seeds of the pine are naked, that is, they
are exposed. From this character the name of the gymnosperms, or naked
seed plants, is derived.
Exercise 59.
303. The male cones.— Observe the large clusters of the male flowers, sev-
eral cones collected together. Sketch a cluster. Sketch a separate cone. Note
that the cone is made up of an axis and scales as in the female cone, but the
scales are different in form, Remove several of the scales. Note the form.
Upon the under side note the two strong convexities. Cut across scale,
and note that there are two sacs situated here. These sacs are the spore-
cases (small sporangia). The fine granules which escape are the small
spores, or pollen.
If you have an opportunity when the pollen is ripe on a pine tree, jar the
tree to see the clouds of pollen "dust " escape. When the sacs on the under
side of the scale open in drying, note the position of the slit. Sketch such
an open scale.
Demonstration 43.
304. Pollen grains. — Mount a few of the pollen grains in water for exam-
ination with the microscope. Let each pupil observe, and sketch a pollen
grain. Observe the two large air sacs on either side of the pollen grain. Of
what use are these air sacs to the pollen ? Do insects pollinate the pines, or
are they wind pollinated?
If it is desired to demonstrate the prothallium, archegonia, and fertilization
in the pine, the teacher can either prepare or purchase slides for the pur-
pose. See the author's larger "Elementary Botany," Chapters XXI and
XXII, for further studies of the gymnosperms, and for fertilization, etc.
1 86 BOTANY.
305, General aspect of the white pine, — The white pine
(Pinus strobus) is found in the Eastern United States. In
favorable situations in the forest it reaches a height of about 50
meters (about 160 feet), and the trunk a diameter of ovei
I meter. In well-formed trees the trunk is straight and tower-
ing; the branches where the sunlight has access and the trees
are not crowded, or are young, reaching out in graceful arms,
form a pyramidal outline to the tree. In old and dense forests
the lower branches, because of lack of sunlight, have died away,
leaving tall, bare trunks for a considerable height.
306, The long shoots of the pine.— The branches are of two
kinds. Those which we readily recognize are the long
branches, so called because the growth in length each year is
considerable. The terminal bud of the long branches, as well
as of the main stem, continues each year the growth of the
main branch or shoot; while the lateral long branches arise
each year from buds which are crowded close together around
the base of the terminal bud. The lateral long branches of each
year thus appear to be in a whorl. The distance between each
false whorl of branches, then, represents one year's growth in
length of the main stem or long branch.
307. The dwarf shoots of the pine. — The dwarf branches are
all lateral on the long branches, or shoots. They are scattered
over the year's growth, and each bears a cluster of five long,
needle-shaped, green leaves, which remain on the tree for
several years. At the base of the green leaves are a number of
chaff-like scales, the previous bud scales. While the dwarf
branches thus bear green leaves, and scales, the long branches
bear only thin scale-like leaves which are not green.
308. Spore-bearing leaves of the pine. — The two kinds of'
spore-bearing leaves of the pine, and their close relatives, are so
different from anything which we have yet studied, and are so
unlike the green leaves of the pine, that we would scarcely
recognize them as belonging to this category. Indeed there is
great uncertainty regarding their origin.
G YMNOSPERMS.
I87
309. Male cones, or male flowers. — The male cones are borne
in clusters as shown in fig. 158. Each compact, nearly cylin-
drical, or conical mass is termed a cone, or flower, and each
arises in place of a long lateral branch. One of these cones is
Fig. 158.
Spray of white pine showing cluster of male cones just before the scattering of the pollen.
shown considerably enlarged in fig. 159. The central axis of
each cone is a lateral branch, and belongs to the stem series.
The stem axis of the cone can be seen in fig. 160. It is com-
pletely covered by stout, thick, scale-like outgrowths. These
scales are obovate in outline, and at the inner angle of the
JiOTAMY.
upper end there are several rough, short spines. They are
attached by their inner lower angle, which forms a short stalk
Fig. 159. Fig. 160.
Staminate cone of white Section of staminate
pine, with bud scales re- cone showing sporangia,
moved on one side.
Fig. 161.
Two sporo-
phylls removed,
showing open-
ing of sporangia.
or petiole, and continues through the inner face of the scale as
a " midrib." What corresponds to the lamina of the scale-like
leaf bulges out on each side below and makes the bulk of the
scale. These prominences on the under side are the sporangia
(micro-sporangia). There are thus two sporangia on a sporo-
phyll (micro-sporophyll). When the spores (microspores),
which here are usually called pollen grains, are mature each
sporangium, or anther locule, splits down the
middle as shown in fig. 161, and the spores are
set free.
310, Microspores of the pine, or pollen
grains. — A mature pollen grain of the pine is
shown in fig. 162. It is a queer-looking
object, possessing on two sides an air sac, formed by the
upheaval of the outer coat of the spore at these two points.
When the pollen is mature, the moisture dries out of the scale
(or stamen, as it is often called here) while it ripens. When a
limb, bearing a cluster of male cones, is jarred by the hand, or
Fig. 162.
Pollen grain
white pine
of
G YMNOSPERMS.
189
by currents of air, the split suddenly opens, and a cloud of
pollen bursts out from the numerous anther
locules. The pollen is thus borne on the
wind and some of it falls on the female
flowers.
311. Form of the mature female cone.—
A cluster of the white-pine cones is
shown in fig. 163. These are
mature, and
the scales have
Fig.
White pine, branch with cluster of
mature cones shedding the seed. A
few young cones four months old
are shown on branch at the left.
Drawn from photograph.
spread as they do when
mature and becoming
dry, in order that the
seeds may be set at
liberty. The general
outline of the cone is lanceolate, or long oval, and somewhat
curved, It measures about 10-15 cm long. If we remove one
Fig. 164.
Mature cone of white pine
at time of scattering of the
seed, nearly natural size.
19° BOTANY.
of the scales, just as they are beginning to spread, or before the
Fig. 165. Fig. 166. Fig. 167. Fig. 168. Fig. 169.
Sterile seal e. Scale with Seeds have Back of scale Winged
Seeds undevel- w e 1 1 ^ developed split off from with small cover se~ed free
oped. seeds. • scale. scale. from scale.
Figures 165-169 — White pine showing details of mature scales and seed.
seeds have scattered, we shall find the seeds attached to the
upper surface at the lower end. There are two
seeds on each scale, one at each lower angle.
They are ovate in outline, and shaped some-
what like a biconvex lens. At this time the
seeds easily fall away, and may be freed by
jarring the cone. As the seed is detached from
the scale a strip of tissue from the latter is
peeled off. This forms a "wing" for the
seed. It is attached to one end and is shaped
something like a knife blade. On the back of
the scale is a small appendage known as the
cover scale.
312. Formation of the female pine cone.—
The female flowers begin their development
rather late in the spring of the year. They
are formed from terminal buds of the higher
branches of the tree. In this way the cone may
terminate the main shoot of a branch, or of
the lateral shoots in a whorl. After growth
Female cones of the has proceeded for some time in the spring,
pine at time of pollina-
tion, about natural size. the terminal portion begins to assume the ap-
Fig. 170.
G YMNOSPERMS.
pearance of a young female cone or flower. These young
female cones, at about the time that the pollen is escaping
from the anthers, are long ovate, measuring about 6-10 mm
long. They stand upright as shown in fig. 170.
313, Form of a "scale" of the female flower. — If we
remove one of the scales from the cone at this stage we can
better study it in detail. It is flattened,
and oval in outline, with a stout " rib," if
it may be so called, running through the
middle line and terminating in a point.
The scale is in two parts as shown in fig.
173, which is a view of the under side.
The small " outgrowth " which appears as
an appendage is the cover scale, for while it
is smaller in the pine than the other portion,
in some of the relatives of the pine it is
larger than its mate, and being on the out-
side, covers it. ' (The inner scale is some-
times called the ovuliferous scale, because
it bears the ovules.)
314. Ovules, or macrosporangia, of the
Fig. 171. Fig. 172. Fig. 173.
Section of female cone Scale of white pine with the Scale of white pine seen
of white pine, showing two ovules at base of ovulif- from the outside, showing the
young ovules (macrospo- erous scale. cover scale,
rangia) at base of the ovu-
liferous scales.
pine. — At each of the lower angles of the scale is a curious oval
body with two curved, forceps-like processes at the lower and
I92
BOTANY.
smaller end. These are the macrosporangia, or, as they are called
in the higher plants, the ovules. These ovules, as we see, are
in the positions of the seeds on the mature cones. In fact the
wall of the ovule forms the outer coat
of the seed, as we will later see.
315. Pollination. — At the time when
the pollen is mature the female cones
are still erect on the branches, and the
scales, which during the earlier stages of
growth were closely pressed against one
another around the axis, are
now spread apart. As the
Branch of white pine showing young female cones at time of pollination on the ends of
the branches, and one-year-old cones below, near the time of fertilization.
clouds of pollen burst from the clusters of the male cones,
some of it is wafted by the wind to the female cones. It is here
caught in the open scales, and rolls down to their bases, where
some of it falls between these forceps-like processes at the lower
end of the ovule, At this time the ovule has exuded a drop of
GYMNOSPERMS. 193
a sticky fluid in this depression between the curved processes at
its lower end. The pollen sticks to this, and later, as this viscid
substance dries up, it pulls the pollen close up in the depression
against the lower end of the ovule. This depression is thus
known as the pollen chamber.
Now the open scales on the young female cone close up
again, so tightly that water from rains is excluded. What is
also very curious, the cones, which up to this time have been
standing erect, so that the open scale could catch the pollen,
now turn so that they hang downward. This more certainly
excludes the rains, since the overlapping of the scales forms a
shingled surface. Quantities of resin are also formed in the
scales, which exudes and makes the cone practically impervious
to water.
The female cone now slowly grows during the summer
and autumn, increasing but little in size during this time.
During the winter it rests, that is, ceases to grow. With the
coming of spring, growth commences again and at an accelerated
rate. The increase in size is more rapid. The cone reaches
maturity in September. We thus see that nearly eighteen
months elapse from the beginning of the female flower to the
maturity of the cone, and about fifteen months from the time
that pollination takes place.
Material. — §everal branches of the pine showing the long shoots and
whorls of branches. (These should be had in the laboratory if the tree can-
not be studied in the open. If fresh branches cannot be had, preserve them
dry.)
Mature cones collected in August just before the seeds fall away.
Branches with the female cones, collected from the top of the tree, in early
summer (June), preserve in alcohol.
Branches with the clusters of male cones collected late in May or early in
June just before the pollen is scattered. Preserve in alcohol.
Sections to show the female prothallium, archegonium, and fertilization
can be made by the teacher, or they may be purchased of supply companies.
Dissecting microscope, or tripod lens ; dissecting needles.
CHAPTER XXXI.
MORPHOLOGY OF THE ANGIOSPERMS : TRILLIUM;
DENTARIA.
Exercise 6O.
316. Trillium. — Note the general habit of the plant ; the short, thick,
underground stem, which is perennial ; the roots attached to this ; the
scale leaves at the anterior end around the base of the flowering stem. Note
the flowering stem ; the whorl of three green leaves on it, and the terminal
flower. Observe that there are no roots attached to the flowering stem. Is
the flowering stem perennial?
Exercise 61.
317. Flower of trillium. — Observe the difference in the parts of the
flower ; two whorls of leaf-like parts on the outside. Take these up in
order, beginning at the outside.
Outer whorl (calyx) ; note the resemblance of each member of the calyx
to the leaf. How do they compare in number with the whorl of leaves on
the stem ? Sketch one. Each one is a sepal.
318. Corolla the second whorl. — Is there any resemblartfc between the
parts of the corolla and a leaf of trillium ? How do the parts compare as to
form and number with the leaves ? Sketch one. Each part of the corolla
is a petal.
319. Third and fourth whorl (androecium). — Note here that there are six
members composing these two whorls, three in each. Is there any resem-
blance between these and the leaves ? Did you ever see any of these mem-
bers (stamens) partly changed to petals or leaves .in trillium? Did you ever
see any of them partly changed in other flowers ? in the water lily for ex-
ample. Examine a water lily when you have an opportunity. Look for
these changes in other plants when you have an opportunity.
Sketch a stamen, and name the parts, the slender stalk (filament), the
more expanded part (anther) with four long sacs (anther locules, or sacs) ;
194
ANGIOSPEKMS. 195
if they have just opened observe the great quantity of yellow "dust."
These are the pollen grains, or the small spores. (The anther sacs then must
be the small sporangia.)
320. The inner whorl (gynoecium). — Note that the structure in the centre
of the trillium flower ends in three slender points ; cut across the larger
part of this object below. Note that it has three chambers. What does this
suggest ? What do you find attached to the inner walls of these chambers ?
They are the ovules. Sketch a cross-section. Is there any relation be-
tween the three parts of this structure (pistil) and leaves ? What is this
relation ? Compare the mature fruit of trillium (if at hand) with the pistil
and ovules.
DESCRIPTION OF TRILLIUM.
321. General appearance. — As one of the plants to illustrate
this group we may take the wake-robin, as it is sometimes
called, or trillium. There are several species of this genus in
the United States; the commonest one in the eastern part is
the " white wake-robin '/ (Trillium grandiflorum). This occurs
in or near the woods. A picture of the .plant is shown in fig.
175. There is a thick, fleshy, underground stem, or rhizome
as it is usually called. This rhizome is perennial, and is marked
by ridges and scars. The roots are quite stout and possess
coarse wrinkles. From the growing end of the rhizome each
year the leafy, flowering stem arises. This is 20-30 cm. (8-12
inches) in height. Near the upper end is a whorl of three ovate
leaves, and from the centre of this rosette rises the flower stalk,
bearing the flower at its summit.
322. Parts of the flower. Calyx. — Now if we examine the
flower we shall see that there are several leaf-like structures.
These are arranged also in threes just as are the leaves. First
there is a whorl of three, pointed, lanceolate, green, leaf-like
members, which make up the calyx in the higher plants, and the
parts of the calyx are sepals, that is, each leaf-like member is a
sepal. But while the sepals are part of the flower, so called,
we easily recognize them as belonging to the leaf series.
323. Corolla. — Next above the calyx is a whorl of white or
pinkish members, in Trillium grandiflorum, which are also leaf-
196 BOTANY.
like in form, and broader than the sepals, being usually some-
what broader at the free
the corolla in the higher
the corolla is a petal
the flower, and are not
would suggest that they
324. Androecium. -
of the corolla is found
bers which do not at first
They are known in the
seen in fig. 176 each
filament), and extending
greater part of the length
side. This part of the
ridges form the anther
flower is opened, these
in the wall along the edge
see quantities of yellow-
escaping from the rup-
les. If we place some
microscope we see that it
ute bodies which resem-
rounded in form, and the
end. These make up what is
plants, and each member of
But while they are parts of
green, their form and position
also belong to the leaf series.
Within and above the insertion
another tier, or whorl, of mem-
sight resemble leaves in form.
higher plants as stamens. As
stamen possesses a stalk (=:
along on either side for the
are four ridges, two on each
stamen is the anther, and the
sacs, or lobes. Soon after the
anther sacs open also by a split
of the ridge. At this time we
ish powder or dust
tured anther locu-
of this under the
is made up of min-
ble spores; they are
175-
Trillium grandiflorum. OUter Wall is Spiny,
ANGIOSPERMS.
They are in fact spores, the microspores of the trillium, and
here, as in the gymnosperms, are, better known as pollen.
325. The stamen a sporophyll. — Since these pollen grains
are the spores, we would
infer, from what we have
learned of the ferns and
gymnosperms, that this
Fig. 176.
Sepal, petal, stamen, and pistil of Trillium
grandiflorum.
member of the flower which
bears them is a sporophyll;
and this is the case. It is in
fact what is called the micro-
sporophylL Then we see also
that the anther sacs, since they
enclose the spores, would be the sporangia
(microsporangia). From this it is now quite
clear that the stamens belong also to the leaf
series. They are just six in number, twice the
number found in a whorl of leaves, or sepals,
or corolla. It is believed, therefore,
that there are two whorls of stamens
in the flower of trillium.
326, Gyncecium. — Next above the
stamens and at the centre of the flower
is a stout, angular, ovate body which terminates in three
long, slender, curved points. This is the pistil, and at
Fig. 177.
Trillium grand-
diflorum, with
he compound
pistil expanded
into threV leaf-
1 i k e members.
At the right
these three are
shown in detail.
198
BOTANY.
present the only suggestion which it gives of belonging to the
leaf series is the fact that the end is divided into three parts,
the number of parts in each successive whorl of members of the
flower. If wre cut across the
body of this pistil and examine
it with a low power we see that
there are three chambers or cavi-
ties, and at the junction of each
the walls suggest to us that this
body may have been formed by
the infolding
of the margins
of three leaf-
like members,
the places of contact having
then become grown together.
We see also that from the incurved
margins of each division of the pistil
there stand out in the cavity oval
bodies. These are the ovules. Now the ovules, we have learned
from our study of the gymnosperms, are the sporangia (here the
macrosporangia). It is now more evident that this curious
body, the pistil, is made up of three leaf-like mem-
bers which have fused together, each member being
the equivalent of a sporophyll (here the macrosporo-
phyll). This must be a fascinating observation, that
plants of such widely different groups and of such
different grades of complexity should have members
formed on the same plan and belonging to the same
series of members, devoted to similar functions, and
stJmenSoTTnU yet carried out with such great modifications that at
antoer^ocuuls nrst we do not see this common meeting ground
: mar-m. ^hj^ a comparative study brings out so clearly.
327. Transformations of the flower of trillium. — If anything
more were needed to make it clear ihat the parts of the flower
Fig. 178.
Abnormal
trillium. The
nine parts of
the perianth
are green,
and the outer
whorls of
stamens are
expanded into
petal-like mem-
bers.
Fig. .79.
TRILLIUM. 199
of trillium belong to the leaf series we could obtain evidence
from the transformations which the flower of trillium sometimes
presents. In fig. 178 is a sketch of a flower of trillium, made
from a photograph. One set of the stamens has expanded into
petal-like organs, with the anther sacs on the margin. In fig.
177 is shown a plant of Trillium grandiflorum in which the
pistil has separated into three distinct and expanded leaf-like
structures, all green except portions of the margin.
Exercise 62.
328. Toothwort (dentaria). — Note the general habit of the plant ; the
rather long, slender, smooth, fleshy, underground, perennial root stock
(stem) ; the rudimentary leaves ; the roots ; the growing end some distance
ahead of the point where the annual flowering shoot arises ; compare with
trillium in this respect.
The flowering annual shoot ; note the slender, smooth stem, the two
opposite leaves which are three divided (trifoliate), the open raceme of
flowers terminating the shoot.
Exercise 63.
329. The flower. — Compare the parts of the flower with the leaves. The
flowers should be collected before all of them are open, since the sepals fall
away quite easily. Note that the flower parts are in twos or multiples of
two, while in trillium the parts are in threes or multiples of three. In each
case the number of parts in a whorl is the same as the number of leaves in a
whorl, so that this strengthens the view of the parts of the flower being
homologous with the leaves.
Illustrate and describe the different members of the flower. The pistil
here is also a compound pistil.
If there is time compare with other flowers like the toothwort, as the
shepherd's purse, mustard, etc.
DESCRIPTION OF THE TOOTHWORT.
330, General appearance. — For another study we may take
a plant which belongs to another division of the higher plants,
the common "pepper root," or "toothwort" (Dentaria di-
phylla) as it is sometimes called. This plant occurs in moist
20O BOTANY.
woods during the month of May, and is well distributed in the
Fig. ,81.
Flower of the toothwort (Dentaria
diphylla).
northeastern United
States. A plant is shown
in fig. 1 80. It has a
creeping underground
rhizome, whitish in color,
fleshy, and with a few
scales. Each spring the
annual flower - bearing
stem rises from one of
the buds of the rhizome,
and after the ripening of
the seeds, dies down.
The leaves are
situated a little above
the middle point of
the stem. They are
opposite and the num-
ber is two, each one
180.
Toothwort (Dentaria diphylla).
TOOTffWORT. 2O I
being divided into three dentate lobes, making what is called a
compound leaf.
331. Parts of the flower. — The flowers are several, and they
are borne on quite long stalks (pedicels) scattered over the
terminal portion of the stem. We should now examine the
parts of the flower, beginning with the calyx. Thrs we can see,
looking at the under side of some of the flowers, possesses four
scale-like sepals, which easily fall away after the opening of the
flower. They do not resemble leaves so much as the sepals of
trillium, but they belong to the leaf series, and there are two
pairs in the set of four. The corolla also possesses four petals,
which are more expanded than the sepals and are whitish in
color. The stamens are six in number, one pair lower than
the others, and also shorter. The filament is long in propor-
tion to the anther, the latter consisting of two lobes or sacs,
instead of four as in trillium. The pistil is composed of two
carpels, or leaves fused together. So we find in the case of the
pepper root that the parts of the flower are in twos, or multiples
of two. Thus they agree in this respect with the leaves; and
while we do not see such a strong resemblance between the
parts of the flower here and the leaves, yet from the presence
of the pollen (microspores) in the anther sacs (microsporangia)
and of ovules (macrosporangia) on the margins of each half of
the pistil, we are, from our previous studies, able to recognize
here that all the members of the flower belong to the leaf
series.
332. In trillium and in the pepper root we have seen that
the parts of the flower in each apparent whorl are either of the
same number as the leaves in a whorl, or some multiple of that
number. This is true of a large number of other plants, but it
is not true of all. The trillium and the dentaria were selected
as being good examples to study first, to make it very clear
that the members of the flower are fundamentally leaf structures,
or rather that they belong to the same series of members as do
the leaves of the plant.
202 BOTANY.
Material — Entire plants of trillium and dentaria in flower, with root
stock. Specimens either fresh or dried. Entire flowers of both plants
when they cannot be obtained at the right season, may be preserved in ad-
vance in formalin. A sufficient number should be prepared, depending on
the number of pupils in the class. Mature fruit may also be preserved in
formalin or alcohol. It will be useful to have entire plants of trillium col-
lected in late autumn, in the winter, or early spring before the flower stalk
rises above the ground, in order to see the condition in which the flower
passes the winter.
CHAPTER XXXII.*
PROTHALLIUM AND SEXUAL ORGANS OF
FLOWERING PLANTS.
333. The stamens and pistils are not the sexual organs.—
Before the sexual organs and sexual processes in plants were
properly understood it was customary for botanists to speak
of the stamens and pistils of flowering plants as the sexual
organs. Some of the early botanists, a century ago, found
that in many plants the seed would not form unless first the
pollen from the stamens came to be deposited on the stigma of
the pistil. A little further study showed that the pollen
germinated on the stigma and formed a tube which made its
way down through the pistil and into the ovule.
This process, including the deposition of the pollen on the
stigma was supposed to be fertilization, the stamen was looked
on as the male sexual organ, and the pistil as the female sexual
organ. We have found out, however, by further study, and
especially by a comparison of the flowering plants and the lower
plants, that the stamens and pistils are not the sexual organs of
the flower.
334. The stamens and pistils are spore-bearing leaves. — The
stamen is the spore-bearing leaf, and the pollen grains are not un-
like spores; in fact they are the small spores of the angiosperms.
The pistil is also a spore-bearing leaf, the ovule the sporangium,
which contains the large spore called an embryo sac. In the
ferns we know that the spore germinates and produces the green
heart-shaped prothallium. The prothallium bears the sexual
* This chapter is for reading and reference, but if the teacher desires to
give demonstrations of the germinating pollen grain, and of the embryo sac,
the following memorandum on material will be found of assistance.
203
204 SOT A xv.
organs. Now the fern leaf bears the spores and the spore forms
the prothallium. So it is in the flowering plants. The stamen
bears the small spores — pollen grains — and the pollen grain
Fig. 182.
Diagrammatic section of a flower. A>, calyx ; A~ corolla ; f, the filament, and «, the
anther, of the stamen ; /, pollen-cells, some in the anther, others on the stigma ; F, the
ovary, surmounted by the style, g, and the stigma, n (this ovary contains one ovule, which
has a single coat, /', enclosing the ovule-body, S) ; em,*he embryo-sac; £, germ-cell; /.?,
a pollen-tube penetrating the style, and reaching the germ-cell through the micropyle of
the ovule.
forms the prothallium. The prothallium in turn forms the sex-
ual organs. The process is in general the same as it is in the
ferns, but with this special difference : the prothallium and the
sexual organ of the flowering plants are very much reduced.
335. The male prothallium is reduced to the pollen grain.
— In fact the pollen grain is male prothallium and
sexual organ all in one, so reduced has it become.
A young pollen grain of trillium is shown in fig.
183. It has two cells. The entire pollen grain
Fj ig may be considered the antheridium, the larger cell
Nearly mature representing.: the wall while the smaller cell is the
pollen grain of tril- -
Hum. The smaller generative cell. The latter corresponds to the
cell is the genera- .... T ,,
tiveceii. central cell of the fern antheridium. In the
angiosperms it divides to form two sperm cells. These cor-
POLLINATION AND FERTILIZATION. 2OJ
respond to the spermatozoids, though they are not motile.
Sometimes the sperm cells are formed within the pollen grain.
At other times they are only formed
after the pollen grain has germinated.
In fig. 184 is a germinating pollen
grain of peltandra, showing three
nuclei. The generative cell has di-
vided to form the two sperm cells.
336. The embryo sac is the female
prothallium. — Now while the small
spore (= the pollen grain) escapes
usually from the anther, the larger
UCU LtJ IU1I11 L11C LWU
SDOre (= embryo Sac), borne in. the sperm nuclei ; vegeta-
tive nucleus in each
OVule On the plStll, never escapes COm- near the pollen grain.
pletely from the ovule, and only rarely protrudes part way.
Inside of the nucellus, which is the central part of the ovule, a
sac is formed which contains several nuclei. It is the embryo
sac, or large spore, as shown in the diagram. It is also the
female prothallium. One of these nuclei is the egg nucleus,
but the prothallium is so reduced that there is no archegonium
wall. The egg itself is perhaps the reduced archegonium.
337. Fertilization. — When the pollen tube grows down the
pistil and into the embryo sac in the ovule, as shown in the
diagram (fig. 182), one of the sperm nuclei which it bears unites
with the egg nucleus of the embryo sac. This '^fertilization.
The fertilized egg now grows to form the embryo. So the em-
bryo is formed inside of the ovule. This is what makes the seed.
The ovule with its coats contains the embryo. Since the embryo
sac containing the egg does not escape from the ovule, the sperm
cell must in some way be brought to it. This necessitates the
transportation of the pollen from the stamen to the pistil.
This transportation of the pollen from the stamen to the pistil
is pollination. Botanists now usually distinguish in this way
between pollination and fertilization.
338. Difference between organ and member, — While it is
206
BOTANY.
not strictly correct then to say that the stamen is a sexual organ,
or male organ, we might regard it as a male member of the flower,
and we should distinguish between organ and member. It is an
organ when we consider pollen production, but it is not a sexual
organ. When we consider fertilization it is not a sexual organ,
but a male member of the flower which bears the small spore.
The following table will serve to indicate these relations.
Stamen = spore-bearing leaf = male member of flower.
Anther locule = sporangium.
Pollen grain = small spore = reduced male prothallium and
sexual organ.
So the pistil is not a sexual organ, but might be regarded as
the female member of the flower.
Pistil = spore-bearing leaf = female member of flower.
Ovule = sporangium.
Embryo sac = large spore = female prothallium containing the
egg-
The egg = a reduced archegonium = the female sexual
organ.
•A C
Fig. 185.
A, represents a straight (orthotropus) ovule of polygonum; B, the inverted (anatropous)
ovule of the lily ; and C, the right angled (campylotropus) ovule of the bean. /, funicle ;
c, chalaza ; /t, nucellus ; at, outer integument ; />', inner integument ; ;«, micropyle ; em,
embryo sac.
339, Parts of the ovule.— In fig. 185 are represented three
d.ffertnt kinds of ovules, which depend on the position of the
POLLINATION AND FERTILIZATION. 2O/
ovule with reference to its stalk. The funicle is the stalk of the
ovule, the hilum is the point of attachment of the ovule with
the ovary, the raphe is the part of the funicle in contact with
the ovule in inverted ovules, the chalaza is the portion of the
ovule where the nucellus and the integuments merge at the base
of the ovule, and the micropyle is the opening at the apex of
the ovule where the coats do not meet.
340. In the pines and other gymnosperms the male and
female prothallium, as regards structure and development, are
intermediate between those of the higher plants and the ferns,
but they are nevertheless much reduced. For a full discussion
of the prothallium and sexual organs of the gymnosperms and
angiosperms see the author's larger "Elementary Botany,"
Chapters XXXI, XXXII, and XXXIV, and for pollination, see
Chapter L.
Material. — To show the male and female prothallium of angiosperms.
Pollen grains of several species may be germinated in a weak solution of
sugar in water, and these studied with the aid of the microscope, to see the
pollen tube.
The female prothallium (embryo sac in different stages) can be obtained
by making sections of ovules just before and after fertilization. The lily
is a good one to use, since there are many ovules standing at right angles
to the pistil. Cross-sections of the pistil afford many good sections of the
ovules where they are carefully made. Permanent slides can be purchased
of supply companies.
CHAPTER XXXIII.
SEEDS AND SEEDLINGS.
I. SEEDS.
This chapter is for reading and reference.
341. Parts of the seed. — The seed consists of the embryo
surrounded by the ripened ovule and certain secondary growths.
Following fertilization as the embryo is forming in the embryo
sac, a new growth of cells is formed also within the embryo
sac but surrounding the embryo. This is called the endosperm.
The young embryo derives some of its nutriment from the endo-
sperm. In some seeds the nucellus (central part of the ovule)
forms nutritive tissue, which may be consumed during the
ripening of the seed, or in some seeds a portion of it remains
outside of the endosperm, as perisperm.
342. Outer parts of the seed. — While the embryo is forming
within the ovule and the growth of the endosperm is taking
place, where this is formed, other correlated changes occur in
the outer parts of the ovule, and often in adjacent parts of the
flower. These unite in making the " seed," or the " fruit."
Especially in connection with the formation of the seed a new
growth of the outer coat, or integument, of the ovuie occurs,
forming the outer coat of the seed, known as the testa, while
the inner integument is absorbed. In some cases the inner
integument of the ovule also forms a new growth, making an
inner coat of the seed (rosaceae). In still other cases neither
of the integuments develops into a testa, and the embryo sac
lies in contact with the wall of the ovary. Again an additional
SEEDS AND SEEDLINGS. 2O$
envelope grows up around the seed; an example of this is
found in the case of the red berries of the " yew " (taxus), the
red outer coat being an extra growth, called an aril.
In the willow and the milkweed an aril is developed in the
form of a tuft of hairs. (In the willow it is an outgrowth of
the funicle, = stalk of the ovule, and is called a funicular aril;
while in the milkweed it is an outgrowth of the micropyle, =
the open end of the ovule, and is called a micropylar aril. )
343. Increase in size during seed formation. — Accompany-
ing this extra growth of the different parts of the ovule in the
formation of the seed is an increase in the size, so that the seed
is often much greater in size than the ovule at the time, of fer-
tilization. At the same time parts of the ovary, and in many
plants, the adherent parts of the floral envelopes, as in the apple;
or of the receptacle, as in the strawberry; or in the involucre,
as in the acorn; are also stimulated to additional growth, and
assist in making the fruit.
In the pine not only the ovular coat grows to form the outer
coat of the seed, the entire " scale" increases greatly in size,
and when the fruit is mature, a portion of this scale splits off
forming a " wing" to the seed (see fig. 169).
344. Endosperm in the ripe seed. — In many seeds when they
are ripe there is still a large amount of the endosperm surround-
ing the embryo (albuminous seeds).
This is the case in the violet, as
shown in fig. 186. Other examples
of this kind are found in the butter-
cup family, the grasses, the lily,
palm, jack-in-the-pulpit, etc. When
the seed germinates this endosperm
is used as food by the embryo. .
345. EndOSperm absent in the Seed of violet, external view, and
, T section. The section shows the em-
ripe seed. — In many other plants bryo lying in the endosperm.
all of the endosperm is consumed by the embryo during its
growth in the formation of the seed. This is the case in the
210 BOTANY.
rose family, crucifers, composites, willows, oaks, legumes, etc.,
as in the acorn, the bean, pea, and others. In some, as in the
bean, a large part of the nutrient substance passing from the
endosperm into the embryo is stored in the cotyledons for use
during germination (exalbuminous seeds).
346. Synopsis of the seed.
Aril, rarely present.
Ovular coats (one or two usually present), the
testa.
Funicle (stalk of ovule), raphe (portion of funicle
Ripened ovule. \ when bent on to the side cf ovule), micropyle,
hilum (scar where seed was attached to ovary).
7~vj /y
Remnant of the nucellus (central part of ovule) ;
sometimes nucellus remains as
\^Perisperm in some albuminous seeds.
Endosperm, present in albuminous seeds.
Embryo within surrounded by endosperm when this is present,
or by the remnant of nucellus, and by the ovular coats which
(_ make the testa.
See figures for parts of the ovule.
II. SEEDLINGS.
(For reading, unless exercises 1-4 have not yet been em-
ployed. In that case those exercises should be taken up now.)
347. Additional studies on seedlings, — In beginning our
studies of the life processes of plants we used a number of seed-
lings. We found it necessary to learn something about the parts
of the seedling, and in fact about the parts of mature plants in
dealing with the functions which the members of the plant per-
form. Now, however, we are dealing more strictly with the parts
of 'the plant in respect to the form of the member, and its value
as showing relationship among plants. So that studies of seeds
and seedlings is a part of our study of the form characters in the
morphology of the angiosperms. Even if one choses to complete
the practical study of the seedling under the head of the life
processes of plants, one should now take the seeds and seedlings
again into account in recognizing their relation to the new
SEEDS AND SEEDLINGS. 211
theme, and in learning the value of characters which aid us in
assigning plants to their proper categories.
348. The three seedlings to be studied, — For this reason
some of the illustrations of seedlings are introduced here, as
well as an account of their germination, and the means by which
they obtain food stored in the seed. In connection with this
reading the pupil can refer back to the plants studied in exer-
cises 1-4, and the teacher is at liberty to introduce here exer-
cises, if that seems desirable to further illustrate the subject
where there is an abundance of time. Three seedlings are
selected to illustrate the theme here ; the common garden bean,
the castor-oil bean, and the jack-in-the-pulpit.
349. The common garden bean. — The seed coats are nearly
filled with the two large cotyledons, which form the larger part
of the embryo. After the beans have been well soaked if one
is split lengthwise the young root and stem with the small
leaves will be seen lying between the cotyledons at one side.
There is no endosperm here now, since it was all used up in
the growth of the embryo, and a large part of its substance was
stored up in the cotyledons. As the seed germinates the young
plant gets its first food from that stored in the cotyledons. The
part of the stem between the cotyledons and the root (called
the hypocotyl in all seedlings) elongates, so that the cotyledons
are lifted from the soil. The hypocotyl is the part of the stem
here which becomes strongly curved, and the large cotyledons
are dragged out of the soil as shown in fig. 187. The outer
coat becomes loosened, and at last slips off completely. The
plumule (the young part of the stem with the leaves) is now
pushing out from between the cotyledons. As the cotyledons
are coming out of the ground the first pair of leaves rapidly
enlarge, so that before the stem has straightened up there is a
considerable leaf surface for the purpose of starch formation.
The leaves are at first clasped together, but as the stem becomes
erect they are gradually parted and come to stand out nearly in
a horizontal position. Fig. 187 shows the different positions.
212
BOTANY.
As the cotyledons become exposed to the light they assume a
green color. Some of the stored food in them goes to nourish
the embryo during germination, and they therefore become
smaller, shrivel somewhat, and at
last fall off.
350. The castor-oil bean, — This
is not a true bean since it belongs
to a very different family of plants
(euphorbiaceae). In the germina-
tion of this seed a very interesting
comparison can be made with that
of the garden bean. As the * ' bean ' '
swells the very hard outer coat
generally breaks open at the free
end and slips off at the
stem end. The next
coat within, which is also
hard and shining black,
splits open
at the oppo-
site end, that
Fig. 187.
How the garden bean comes out of the ground. First the looped hypocotyl, then the
cotyledons pulled out. next casting off the seed coat, last the plant erect, bearing thick
cotyledons, the expanding leaves, and the plumule between them.
is at the stem end. It usually splits open in the form of
three ribs. Next within the inner coat is a very thin, whitish
film (the remains of the nucellus, and corresponding to the
perisperm) which shrivels up and loosens from the white mass,
the endosperm, within. In the castor-oil bean, then, the
endosperm is not all absorbed by the embryo during the forma-
tion of the seed. As the plant becomes older we should note
that the fleshy endosperm becomes thinner and thinner, and at
SEEDS AND SEEDLINGS.
213
last there is nothing but a thin whitish film covering the green
faces of the cotyledons. The endosperm has been gradually
absorbed by the germinating plant through its cotyledons and
used for food.
Ariseema triphyllum.
351. Germination of seeds of jack-in-the-pulpit. —The
ovaries of jack-in-the-pulpit form large, bright red berries with
a soft pulp enclosing one to several
large seeds. The seeds are oval in
form. Their germination is interesting,
and illustrates one type of germination
of seeds common among monocoty-
ledonus plants. If the seeds are covered
with sand, and kept in
a moist place, they will
germinate readily.
Fig. 188.
Germination of castor-oil bean.
352. How the embryo backs out of the seed. — The embryo
lies within the mass of the endosperm ; the root end, near the
smaller end of the seed. The club-shaped cotyledon lies near
the middle of the seed, surrounded firmly on all sides by the
endosperm. The stalk, or petiole, of the cotyledon, like the
lower part of the petiole of the leaves, is a hollow cylinder, and
contains the younger leaves, and the growing end of the stem
or bud. When germination begins, the stalk, or petiole, of the
cotyledon elongates. This pushes the root end of the embryo
out at the small end of the seed. The free end of the embryo
2I4
BOTANY.
Seedlings of castor-oil bean casting the seed coats, and showing papery remnant of
the endosperm.
Fig. 190.
Seedlings of jack-in-the-pul-
pit ; embryo backing out of the
seed.
Fig. 191.
Section of germinating embryos of
jack-in-the-pulpit, showing young
leaves inside the petiole of the coty-
ledon. At the left cotyledon shown
surrounded by the endosperm in the
seed ; at right endosperm removed to
show the club shaped cotyledon.
SEEDS AND SEEDLINGS.
215
now enlarges somewhat, as seen in the figures, and becomes the
bulb, or corm, of the baby jack. At first no roots are visible,
but in a short time one, two, or more roots appear on the
enlarged end.
353. Section of an embryo. — If we make a longisection of
the embryo and seed at this time we
can see how the club-shaped cotyle-
don is closely surrounded by the
endosperm. Through the cotyledon,
then, the nourishment from the en-
dosperm is readily passed over to the
growing embryo. In the hollowr part
of the petiole near
the bulb can be seen
the first leaf.
Fig. 192- Fig. 193. Fig. 194.
Seedlings of jack-in-the- Embryos of jack-in-the-pulpit still Seedling of jack-in-
pulpit, first leaf arching out attached to the endosperm in seed the-pulpit; section of
of the petiole of the coty- coats, and showing the simple first the endosperm and
ledon. leaf. cotyledon.
354. How the first leaf appears. — As the embryo backs out
of the seed, it turns downward into the soil, unless the seed is
2l6 BOTANY.
so lying that it pushes straight downward. On the upper side
of the arch thus formed, in the petiole of the cotyledon, a slit
appears, and through this opening the first leaf arches its way
out. The loop of the petiole comes out first, and the leaf later,
as shown in fig. 192. The petiole now gradually straightens
up, and as it elongates the leaf expands.
355, The first leaf of the jack-in-the-pulpit is a simple one.
—The first leaf of the embryo jack-in-the-pulpit is very different
in form from the leaves which we are accustomed to see on
mature plants. If we did not know that it came from the seed
of this plant we would not recognize it. It is simple, that is it
consists of one lamina or blade, and not of three leaflets as in
the compound leaf of the mature plant. The simple leaf is
ovate and with a broad heart-shaped base. The jack-in-the-
pulpit, then, as trillium, and some other monocotyledonous
plants which have compound leaves on the mature plants, have
simple leaves during embryonic development. The ancestral
monocotyledons are supposed to have had simple leaves. Thus
there is in the embryonic development of the jack-in,*ihe-pulpit,
and others with compound leaves, a sort of recapitulation of
the evolutionary history of the leaf in these forms.
CHAPTER XXXIV.
THE PLANT BODY AND SOME OF ITS MODI-
FICATIONS.
For reading and reference.
If it is desired to study the different kinds of stems, leaves,
and roots, with their various modifications, the teacher can
arrange some exercises based on the characters and examples
given below in paragraphs 358-364.
356, The plant body. — In the simpler forms of plant life, as
in spirogyra and many of the algae and fungi, the plant bojdy is
not differentiated into parts. In many other cases the only
differentiation is between the growing part and the fruiting part.
In the algae and fungi there is no differentiation into stem and
leaf, though there is an approach to it in some of the higher
forms. Where this simple plant body is flattened, as in the
sea-wrack, or ulva, it is a frond. The Latin word for frond is
thallus, and this name is applied to the plant body of all the
lower plants, the algae and fungi. The algae and fungi together
are sometimes called the thallophytes, or thallus plants. The
word thallus is also sometimes applied to the flattened body of
the liverworts. In the foliose liverworts and mosses there is an
axis with leaf-like expansions. These are believed by some to
represent true stems and leaves, by others to represent a flattened
thallus in which the margins are deeply and regularly divided,
or in which the expansion has only taken place at regular
intervals.
357. Members of the plant body. — In the higher plants there
is usually great differentiation of the plant body, though in
217
2l8 BOTANY.
many forms, as in the duck-weeds, it is a frond. While there
is great variation in the form and function of the members of
the plant body, they are reducible to a few fundamental mem-
bers. Some reduce these forms to three, the root, stem, and
leaf, while others to two, the root and shoot, which is perhaps
the better arrangement. Here the shoot is farther divided into
stem and leaf, the leaf being a lateral outgrowth of the stem.
358. Synopsis of members of the plant in angiosperms.
f Root. f Forage leaves.
Higher plant. J Perianth leaves. ~\
1 Shoot. •! 'm' Spore-bearing leaves
Leaf. J .., . y Flower,
with sporangia.
(Sporangia sometimes I
on shoot).
359, The parts of the plant body as members or organs.—
The members of the plant body can be considered from
several standpoints. We might study them from the standpoint
of physiology, when the members would be regarded as organs
for performing certain kinds of work. As organs for nutrition
the leaves serve a purpose in transpiration and in starch for-
mation. The roots and root hairs serve as organs for absorption
of food from the soil. The bright petals of flowers often serve
to attract insects which aid in cross-pollination. The stamens
and pistils serve a purpose in the process of reproduction. The
stems serve as support for the plant, for the transport of food
materials, and for bearing the leaves and flowers. So in various
modifications of the members purposes of protection, support,
vegetative propagation, etc., are served.
In this sense the members of the plant body might be studied
in Part I, in conjunction with the study of the means by which
plants obtain their food.
From another standpoint we might consider the great variety
of form, and the numerous modifications, as expressions of the
forces of evolution, inheritance, relation to environment, etc.
(see Ecology).
THE PLANT BODY,
From still another standpoint they might be studied as indi-
cating relationships. Their form, position, arrangement, etc.,
serve to characterize certain groups of individuals so that they
can be distinguished from others.
The different forms of the members are usually designated by
special names, but it is convenient to group them in the single
series.
360. Stem Series.
Tubers, underground thickened stems, bearing buds and scale
leaves; ex., Irish potato.
Root-stocks, underground, usually elongated, bearing scales
or bracts, and a leafy shoot; ex., trillium, mandrake, etc.
Root-stocks of the ferns bear expanded, green leaves.
Runners, slender, trailing, bearing bractsr and leafy stems as
branches; ex., strawberry vines.
Corms, underground, short, thick, leaf bearing and scale
bearing; ex., Indian turnip.
Bulbs, usually underground, short, conic, leaf and scale bear-
ing; ex., lily.
Thorns, stout, thick, poorly developed branches with rudi-
ments of leaves (scales); ex., hawthorn.
Tendrils, slender reduced stems.
Flower axes (see morphology of the angiosperms).
361. Leaf series. — Besides the foliage leaves, the following
are some of their modifications :
Flower parts (see morphology of the angiosperms).
Bracts and scales, small, the former usually green (flower
bracts), the latter usually chlorophylless. Bud scales are some-
times green.
Tendrils, modifications of the entire leaf (tendrils of the
squash where the branched tendril shows the principal veins of
the leaf), modification of the terminal pinnae of the leaf (vetch),
etc.
Spines (examples are found in the cacti, where the stem is
enlarged and green, functioning as a leaf).
22O BOTANY.
Other modifications occur as in the pitcher plant, insectivor-
ous plants, etc.
362. The root shows less modification. Besides normal
roots, which are fibrous in most small plants and stout in the
larger ones, some of the modifications are found in fleshy roots,
where nourishment is stored (ex., dahlia, sweet potato, etc.),
aerial roots (ex., poison ivy, the twining form), aerial orchids,
etc.
CHAPTER XXXV.
ARRANGEMENTS OF THE PARTS OF THE
FLOWER.
This chapter is for reading and reference.
363, Relations of the parts of the flower. — In some plants
the parts of the flower are distinct, and in others they are more
or less united. Definite terms are used to indicate these rela-
tions of the parts of the flower. In trillium and dentaria which
we have studied, all the sets, or whorls of parts, axe free; i. e. ,
no one floral set is adherent to another. The pistils make one
set, the stamens another, the petals another, and the sepals
another set. These sets are sdlfree in their insertion on the
receptacle of the flower. The receptacle of the flower is that
portion of the stem where the flower parts are attached.
Further the parts of the calyx, corolla, and androecium are
distinct. That is, the parts (sepals) of the calyx, for example,
are not united together by their edges. .
In the buttercup family, represented by the marsh marigold
(figures 221, 222) all parts of the flower are both free and dis-
tinct.
364. Parts of the flower coherent. — But in both trillium and
dentaria the parts of the gynoecium are coherent, i. e. , the
carpels (three in trillium and two in dentaria) are united into a
single, compound pistil.
So in any set when the parts of that set are partly or com-
pletely united they are said to be coherent. The stamens are
coherent by their anthers in the bell flower and in most of the
flowers of the composite family, as in the aster (see fig. 242),
sunflower, golden rod, etc.
221
222
BOTANY.
In the morning-glory (fig. 195) the petals are coherent, form-
ing a "funnel-shaped corolla as shown in the figure. Such a
corolla is also said to be gamopetalous.
Where the sepals are coherent the
calyx is gamosepalous. The morning-
glory has a gamosepalous calyx also,
though the sepals are
only united near the
base. In the morn-
ing-glory the petal
parts can be distin-
guished, five in num-
ber, but they are not so prominent
as in the bluet (fig. 196), where there
are four prominent petal lobes.
Sometimes the gamopetalous corol-
la is unequally lobed, when it may
be "bilabiate," i.e., two-
lipped as in the dead nettle
(fig. 197), where there are
three petal lobes in the lower
lip and two petal lobes in the
upper lip. Such a flower is
also said to be irregular.
The gamosepalous calyx may
also be two-lipped.
365. Adherent. — In many plants one floral set is united with
another, when such sets are adherent.
This is well shown in the flowers of the evening primrose,
where the tubes of the gamopetalous corolla and gamosepalous
calyx are united to form a long tube. This tube is again at its
base adherent to the outer surface of the ovary, and above, the
stamens are adherent to the throat of the tube (fig. 198).
366. Epigynous, perigynous, and hypogynous. — Where any
portion of the calyx or corolla is adherent to the ovary, the
Fig. 195.
Morning-glory (Convol-
vulus sepium).
ARRANGEMENTS OF FLOWER PARTS. 22$
flower is said to be eptgynous, as in the evening primrose.
When the stamens or petals are borne on the calyx, the flower
is said to be perigynous, or the stamens are said to be perigy-
nous, as in the cherry (fig. 229), apple, etc. The flower is
hypogynous when all the parts of the calyx, corolla, and andrce-
Fig. 196.
The bluet (Houstonia ccerulea).
cium are free in their insertion, that is, when they are inserted
on the receptacle, "under the pistil," since the pistil termi-
nates the floral axis (example, the buttercup, etc. ).
367. Floral Formula. — A formula is sometimes written to
show at a glance the general points of agreement in the flower
224
BOTANY.
among the members of a family or group. The floral formula
of the lily family is written as follows: Calyx 3, Corolla 3,
Fig. 197.
Spray of dead-nettle (Lamium am-
plexicaule), leaves and flowers.
Fig. 198.
Section of flower of
evening primrose.
Androecium 6(3-3), Gynoecium 3. The formula may be abbre-
viated thus: Ca3,Co3,A6(3 -}- 3), 63.
368. Floral diagram. — The relation of the parts of the flower
on the axis are often represented by a diagram, as shown in
figs. 221, 237, 244, etc.
CHAPTER XXXVI.
RELATIONSHIPS SHOWN BY FLOWER AND FRUIT.
369. Importance of the flower in showing kinships among
the higher plants, — In the seed-bearing plants which we are
now studying we cannot fail to be impressed with the general
presence of what is called the flower.
While the spore-bearing members, as well as the floral
envelopes, are thus grouped into "flowers;" there is a great
diversity in the number, arrangement, and interrelation of these
members, as is suggested by our study of trillium and dentaria.
And a farther examination of the flowers of different plants
would reveal a surprising variety of plans. Nevertheless, if we
compare the flower of trillium with that of a lily for example,
or the flower of dentaria with that of the shepherd's purse
(capsella), we shall at once be struck with the similarity in the
plan of the flower, and in the number and arrangement of its
members. This suggests to us that there may be some kinship,
or relationship between the lily and trillium, and between the
shepherd's purse and toothwort. In fact it is through the
interpretation of these different plans that we are able to read
in the book of nature of the relationship of these plants.
NOTE FOR REFERENCE.
370. Arrangement of flowers. — The arrangement of the
flowers (inflorescence) on the stem is important in showing
kinships. The flowers may be scattered and distant from each
other on the plant, or they may be crowded close together in
225
226
BOTANY.
Fig. 199.
Spring beauty (Claytonia virginiana) flowers in a raceme.
RELATIONSHIPS SHOWN BY FLOWER AND FRUIT. 22/
spikes, catkins, heads, etc. Many of the flower arrangements
are dependent on the manner of the branching of the stem.
Some of the systems of branching are as follows:
371. I. DICHOTOMOUS BRANCHING. — True dichotomy (forking)
does not occur in the shoots of flowering plants, but it does
occur in some of the flower clusters.
372. II. LATERAL BRANCHING. — Two main types.
Monopodial branching. — This occurs where the main shoot
continues to grow more vigorously than the lateral
branches which arise in succession around the main
stem. Examples in shoots, horse-chestnut, pines (see
chapter on pine). The inflorescence is termed indefinite,
or indeterminate inflorescence; i.e., the flowers all arise
from lateral buds, the main axis continuing to grow.
Raceme; lateral axes unbranched, youngest flowers near
the terminal portion of long main axis; ex., choke-
cherry, currant, spring beauty, etc.
Spike; main axis long, lateral unbranched axes with
sessile and often crowded flowers; ex., plantain.
Where the main axis is fleshy the spike forms a spadix,
as in skunk's cabbage, Indian turnip, etc. ; if the
spike falls away after maturity of the flower or fruit
it is a catkin or ament (willows, oaks, etc.).
Umbel; the main axis is shortened, and the stalked
flowers appear to form terminal clusters or whorls, as
in the parsley, carrot, parsnip, etc.
Head, or capitulum; the main axis is shortened and
broadened, and bears sessile flowers, as in the sun-
flower, button-bush, etc.
Panicle; when the raceme has the lateral axes branched
it forms a panicle, as in the oat. When the panicle is
flattened it forms a corymb, as in the hawthorn.
Sympodial branching or cymose branching. — The branches,
or lateral axes, grow more vigorously than the main
axis, and form for the time false axes (form cymes).
228 BOTANY.
The inflorescence is termed cymose, or definite, or deter-
minate inflorescence because the growth of each axis is
stopped by the formation of a flower.
Fig. 200.
Single umbel of the wild carrot.
1. Monochasium ; only one lateral branch is produced
from each relative or false axis.
Helicoid cyme; when the successive lateral branches
always arise on the same side of the false axis, as in
flower clusters of the forget-me-not.
Scorpioid cyme; when the lateral branches arise alter-
nately on opposite sides of the false axis.
2. Dichasium; each relative, or false, axis produces two
branches, often forming a false dichotomy. Ex-
amples in shoots are found in the lilac, where the
shoot appears to have a dichotomous branching,
though it is a false dichotomy.
Forking cyme; flower cluster of chickweed.
j. Pleiochasium; each relative, or false, axis produces
more than two branches.
373. The fruit. — In some cases the single seed itself forms
the fruit as is the case with nuts, sunflower seeds, etc. In
other cases several seeds ripen inside of a single pistil as in the
RELATIONSHIPS SHOWN BY FLOWER AND FRUIT.
bean pod, or in several pistils united as in the apple, to form
the fruit. In the sunflower seed and the apple other parts of
the flower are also united with the pistil in forming the fruit.
The fruit of the angiosperms varies greatly, and often is greatly
Fig. 201.
Forget-me-not.
complicated. When the gynoecium is apocarpous (that is when
the carpels are from the first distinct] the ripe carpels are
separate, and each is a fruit. In the syncarpous gyncecium
(when the carpels are united) the fruit is more complicated,
and still more so when other parts of the flower than the gynoe-
cium remain united with it in the fruit.
Pericarp; this is the part of the fruit which envelops the
seed, and may consist of the carpels alone, or of the
carpels and the adherent part of the receptacle, or calyx ;
it forms the wall of the fruit.
Endocarp and exocarp. If the pericarp shows two different
layers, or zones, of tissue, the outer is the exocarp, and
the inner the endocarp, as in the cherry, peach, etc.
23O BOTANY.
Mesocarp; where there is an intermediate zone it is the
mesocarp
I. CAPSULE (dry fruits). The capsule has a dry pericarp
which opens (dehisces) at maturity. When the capsule
is syncarpous the carpels may separate along the line of
their union with each other longitudinally (septicidal
dehiscence] as in the azalea, or rhododendron; or each
carpel may split down the middle line (loculicidal dehiscence]
as in fruit of iris, lily, etc. ; or the carpels may open
by pores (poricidal dehiscence), as in the poppy.
Follicle; a capsule with a single carpel which dehisces
along the ventral, or upper, suture (larkspur, peony).
Legume or pod; a capsule with a single carpel which
dehisces along both sutures (pea, bean, etc.).
Silique; a capsule of two carpels, which separate at
maturity, leaving the partition wall persistent (tooth-
wort, shepherd 's-purse, and most others of the mustard
family) ; when short it is a silicle or pouch.
Pyxidium or pyxis • the capsule opens with a lid (plantain).
II. DRY INDEHISCENT FRUITS; do not dehisce or separate into
distinct carpels.
Nuts; with a dry, hard pericarp.
Caryopsis; with one seed and a dry leathery pericarp
(grasses).
Achene; with pericarp adherent to the seed (sunflower and
other composites).
III. SCHIZOCARP; a dry, several-loculed fruit, in which the
carpels separate from each other at maturity but do
not dehisce (umbel liferae, mallow).
IV. BERRY; endocarp and mesocarp both juicy (grape).
V. POME; mesocarp and outer portion of endocarp soft. and
juicy, inner portion of endocarp papery (apple).
VI. DRUPE, OR STONE FRUIT; endocarp hard and stony,
exocarp soft and generally juicy (cherry, walnut); in
the cocoanut the exocarp is soft and spongy.
CHAPTER XXXVII.
CLASSIFICATION (OR TAXONOMY).
374. Species. — It is not necessary for one to be a botanist in
order to recognize, during a stroll in the woods where the
trillium is flowering, that
there are many individual
plants very like each
other. They may vary
in size, and the parts may
differ a little in form.
When the flowers first
open they are usually
white, and in age they
generally become pinkish. In some
individuals they are pinkish when they
first open. Even with these variations,
which are trifling in comparison with
the points of close agreement, we
recognize the individuals to be of the
same kind, just as we
recognize the corn plants
grown from the seed of
an ear of corn as of the
same kind. Individuals
of the same kind, in this sense, form a
wake-robin, then, is a species.
But there are other trilliums which differ greatly from this
one. The purple trillium (T. erectum) shown in fig. 202 is very
231
Fig. 202.
Trillium erec-
tum(purple form),
two plants from
one root-stock.
species. The white
232 BOTANY.
different from it. So are a number of others. But the purple
trillium is a species. It is made up of individuals variable, yet
very like one another, more so than any one of them is like the
white wake-robin.
375. Genus. — Yet if we study all parts of the plant, the
perennial root-stock, the annual shoot, and the parts of the
flower, we find a great resemblance. In this respect we find
that there are several species which possess the same general
characters. In other words, there is a relationship between
these different species, a relationship which includes more
than the individuals of one kind. It includes several kinds.
Obviously, then, this is a relationship with broader limits, and
of a higher grade, than that of the individuals of a species.
The grade next higher than species we call genus. Trillium,
then, is a genus. Briefly the characters of the genus trillium
are as follows.
376. Genus trillium. — Perianth of six parts: sepals 3,
herbaceous, persistent; petals colored. Stamens 6 (in two
whorls), anthers opening inward. Ovary 3-loculed, 3-6-angled;
stigmas 3, slender, spreading. Herbs with a stout perennial
root-stock with fleshy scale-like leaves, from which the low
annual shoot arises bearing a terminal flower, and 3 large
netted-veined leaves in a whorl.
Note. — In speaking of the genus the present usage is to say
trillium, but two words are usually employed in speaking of the
species, as Trillium grandiflorum, T. erectum, etc.
377. Genus erythronium. — The yellow adder-tongue, or
dog-tooth violet (Erythronium americanum), shown in fig. 203,
is quite different from any species of trillium. It differs more
from any of the species of trillium than they do from each other.
The perianth is of six parts, light yellow, often spotted near the
base. Stamens are 6. The ovary is obovate, tapering at the
base, 3-valved, seeds rather numerous, and the style is elon-
gated. The flower stem or scape, arises from a scaly bulb deep
in the soil, and is sheathed by two elliptical-lanceolate, mottled
CLASS1FICA T10N.
233
leaves. The smaller plants have no flower and but one leaf,
while the bulb is nearer the surface. Each year new bulbs are
formed at the end
of runners from a
parent bulb. These
runners penetrate
each year deeper
in the soil. The
deeper bulbs bear
the flower stems.
378. Genus
lilium. — While the
lily differs from
either the trillium
o r erythronium,
yet we recognize a
relationship when
we compare the
perianth of six
colored parts, the
6 stamens, and the
3-sided and long
3-loculed ovary.
379. Family Fig. 203.
Adder-tongue (erythronium). At left below pistil, and three
llliaCeSB. The re- stamens opposite three parts of the perianth. Bulb at the
right.
lationship between
genera, as between trillium, erythronium, and lilium, brings us
to a still higher order of relationship where the limits are broader
than in the genus. Genera which are thus related make up the
family. In the case ot these genera the family has been named
after the lily, and is the lily family, or LiliacecE.
380. Order, class, group. — In like manner the lily family,
the iris family, the amaryllis family, and others which show
characters of close relationship are united into an order which
has broader limits than the family. This order is the lily order,
234
BOTANY.
or order Liliiflorce. The various orders unite to make up the
class, and the classes unite to form a group.
381. Variations in usage of the terms class, order, etc. -
Thus, according to the system of classification adopted
by some, the angiosperms form a group. The group angio-
sperms is then divided into two classes, the monocotyledones and
dicotyledones. (It should be remembered that all systematists
do not agree in assigning the same grade and limits to the
classes, subclasses, etc. For example, some treat of the
angiosperms as a class, and as the monocotyledons and dicoty-
ledons as subclasses; while others would divide the monocoty-
ledons and dicotyledons into classes, instead of treating each
one as a class or as a subclass. Systematists differ also in usage
as to the termination of the ordinal name; for example, some
use the word Liliales for Liliiflorce, in writing of the order.)
382. Monocotyledones, — In the monocotyledons there is a
single cotyledon on the embryo ; the leaves are parallel veined ;
the parts of the flower are usually in threes; endosperm is
A B
Fig. 204.
A. Cross-section of the stem of an oak tree thirty-seven years old, showing the annual
rings, rm, the medullary rays; /«, the pith (medulla). B. Cross-section of the stem of
a palm tree, showing the scattered bundles.
usually present in the seed; the vascular bundles are usually
closed, and are scattered irregularly through the stem as shown
by a cross-section of the stem of a palm (fig. 204), or by the
arrangement of the bundles in the corn stem (fig. 51). Thus
CLA SSI PICA TSOAT> 235
a single character is not sufficient to show relationship in the
class (nor is it in orders, nor in many of the lower grades), but
one must use the sum of several important characters.
383, Dicotyledones. — In the dicotyledons there are two
cotyledons on the embryo; the venation of the leaves is reticu-
late; the endosperm is usually absent in the seed ; the parts of the
flower are frequently in fives; the vascular bundles of the stem
are generally open and arranged in rings around the stem as shown
in the cross-section of the oak (fig. 204). There are exceptions
to all the above characters and the sum of the characters must
be considered, just as in the case of the monocotyledons.
384. Taxonomy. — This grouping of plants into species,
genera, families, etc., according to characters and relationships
is classification, or taxonomy.
To take Trillium grandiflorum for example, its position in
the system, if all the principal subdivisions should be included
in the outline, would be indicated as follows:
Group, Angiosperms.
Class, Monocotyledones.
Order, Liliiflorae.
Family, Liliaceae.
Genus, Trillium.
Species, grandiflorum.
In the same way the position of toothwort would be indicated
as follows:
Group, Angiosperms.
Class, Dicotyledones.
Order, Rhoeadinae.
Family, Cruciferae.
Genus, Dentaria.
Species, diphylla.
But in giving the technical name of the plant only two of
these names are used, the genus and species, so that for the
toothwort we say Dentaria diphylla, and for the white wake-
robin, we say. Trillium grandiflorum.
STUDIES ON PLANT FAMILIES.
CHAPTER XXXVIII.
MONOCOTYLEDONES.
Topic I : Monocotyledones with conspicuous petals
(Petaloideae).
ORDER LILIIFLOR^E.
385. The lily family (liliaceae). — Trillium grandiflorum
which we employed as a representative of the monocotyledons
in the morphology of the angiosperms, serves as one type of the
lily family. An exercise is added here on the " yellow adder's-
tongue " for those who wish to study more than one example
of the order. There is an abundance of material from the
members of the family if the teacher desires to extend further
the exercises on the liliaceae.
Yellow adder's-tongue (Erythronium americanum). (To be
used as an alternate for trillium if preferred.)
Exercise 64.
386. Entire plant. — Observe the bulb from which the flowering scape
arises ; the small scale-like leaves overlapping it ; the two large spotted leaves
on plants which have the flower. In the case of the nonflowering plants ob-
serve that there is only one large leaf. If an opportunity affords for an ex-
cursion in the woods where the plant grows, see if you can determine how
the bulbs are formed at the ends of the " runners." As to depth in the soil
compare the bulbs of the flowering and nonflowering plants.
Inflorescence. — The inflorescence is determinate, and consists of a single
terminal nodding flower on a scape.
236
LILIACEJE. 237
Flower. — Beginning with the outer whorl of members of the flower deter-
mine the number of members in each whorl, as well as their form, relation to
each other, and the relation of the different sets among themselves.
Sketch a member of the calyx, corolla, and androecium. Sketch the pistil,
naming the parts. Make a section of the pistil (preferably one in which the
seeds are nearly mature) and determine the number of carpels united to form
it. How are the number of carpels manifested in the stigma ?
Construct a floral diagram to show the relation and number of the different
members of the flower.
The flower of the adder's tongue is complete, because it possesses all the
floral sets. It \sperfect, because it-possesses both the androecium and gynoe-
cium. It is regular, because all the members of the calyx, as well as those
of the corolla, are of equal size.
387. Other examples of the lily family. — The lily family is
a large one. Another example is found in the " Solomon's-
seal, " with its elongated, perennial root-stock, the scars
formed by the falling away of each annual shoot resembling a
seal. The onion, smilax, asparagus, lily of the valley, etc.,
are members of the lily family. The parts of the flower are
usually in threes, though there is an exception in the genus
Unifolium, where the parts are in twos. A remarkable excep-
tion occurs sometimes in Trillium grandiflorum, where the
flower is abnormal and the parts are in twos.
OUTDOOR OBSERVATIONS ON SOME OF THE LILIACE^E.
If the study of the plant families is carried on during the
spring, excursions should be made, if possible, to the fields and
woods at opportune times for the purpose of studying some of
the plants in their natural surroundings. The short studies
given here will serve to indicate some of the observations that
can be made during these excursions. For other suggestions,
paragraph 455, and the author's larger " Elementary Botany"
(Part III, Ecology) should be consulted.
388. Trillium. — As this white flower with its setting of green
sepals is glinting to us out of copses and woodland»like so
many new fairies, few of us realize the long task which it has
already begun in the silent depths of the soil in order that it
238 PLANT FAMILIES: MONOCOTYLEDONS.
may suddenly blossom again in season, when springtime returns.
If we remove the old scales where the flowering stem joins the
root-stock, we see a pointed, conical, white bud, which is to
develop into the next season's leafy plant and blossom. From
June to August the new leaves and flower are slowly forming,
protected by several overlapping, thick, whitish, soft scales,
which form a conical roof to keep out water, and to protect
against too sudden changes in cold during the autumn and
winter season. In September we find that leaves and sepals are
well formed and green, the petals are already white, and within
are the six stamens and the angular pistil, all well formed.
Where the sun reaches these copses and warms the soil well in
autumn, sometimes the stamens are yellowish as early as Sep-
tember or October from the already formed pollen. In the
cooler shades the pollen is not yet formed and the stamens re-
main whitish in color. But with the first onset of warm weather
in the spring, or on warm days in the winter, before the flower
bud lifts its head from its long winter sleep, snugly ensconced
among the fallen leaves or spongy humus, the pollen quickly
forms. Now all the plant has to do is to erect its standard,
bearing aloft the opening blossom.
389. The ovules, begun in the autumn, are now being com-
pleted, pollination takes place, and later fertilization, and the
embryo begins to form in June. The pure white flowers soon
change to pinkish, the first evidence of decline. Finally they
wither, and during the summer the fruit and seed are formed
on the old flower stem, while the secret formative processes of
the new blossoms are going on anew.
390, The adder-tongue (erythronium) comes out early in the
spring to catch the sunlight gleaming through rifts in the wood-
land. It is not so forbidding as its name or its "darting"
style would suggest. The rich color of its curved petals
nodding«from the fork of the variegated leaves lends cheer and
brightness to the gray carpet of forest leaves. We are apt to
associate the formation of the flower with the early springtime.
LI LI A CE^E.
239
*.
.;•.
.
f • •
240 PLANT FAMILIES: MONOCOTYLEDONS. -:
But after the flower perishes, the bulb, deep in the soil, slowly
builds the next season's flower, which is kept through the
autumn and winter, much of the time encased in ice, waiting
for springtime that it may rise and unfold.
ORDER GYNANDR.E.
391. The orchid family (orchidaceae). — Among the orchids
are found the most striking departures from the arrangement of
the flower found in the
simpler monocotyle-
dons. An example of
this is seen in the lady-
slipper (cypripedium,
shown in fig. 208). The
ovary appears to be
below the calyx and
corolla. This is brought
about by the adhesion
of the lower part of the
Fig. 206. calyx +o the wall of the
Flower of an orchid (epipactis), l.ie infer!-, ovary nvr,rv TV>p nvarv tV«^r»
twisted as in all orchids so as to bring the upper part of ovaiT- -1 ne OVary then
is inferior, while the
calyx and corolla are epigynous. The stamens are united
with the style by adhesion, two lateral perfect ones and one
upper imperfect one. The stamens are thus gynandrous.
The sepals and petals are each three in number. One of the
petals, the * ' slipper, ' ' is large, nearly horizontal, and forms
the " lip " or " labellum " of the orchid flower. The labellum
is the platform or landing place for the insect in cross-pollina-
tion. 4b9Ye tne labellum stands one of the sepals more showy
than the others, the " banner." The two lateral " strings " of
the slipper are the two other petals. The stamens are still
more reduced in some other genera, while in several tropical
orchids three normal stamens are present.
There are thus forur striking modifications of the orchid
ORCHID A CE&.
241
flower: ist, the flower is irregular (the parts of a set are differ-
ent in size and shape); 2d, adnation of all parts with the pistil;
3d, reduction and suppression 0 t
of the stamens; 4th, the ovary is
twisted half way around so that
the posterior side of the flower
becomes anterior. Floral dia-
grams in fig. 207 show the posi-
tion of the stamens in two dis-
tinct types. The number of
orchid species is very large, and
the majority are found in tropical countries.
392. Pollination of orchids. — Some of the most marvellous
adaptations for cross-pollination by insects are found in the
Fig. 207.
Diagrams of orchid flowers. A, the usual
type ; £, of cypripedium. (Vines.)
Fig. 209.
Section of flower of cypripedium. st,
stigma ; a, at the left stamen. The insect
enters the labellum at the centre, passes
under and against the stigma, and out
through the opening b, where it rubs
against the pollen. In passing through
another flower this pollen is rubbed off
on the stigma.
orchids, or members of the orchis family.
The larger number of the members of
this family grow in the tropics. Many of
these in the forests are supported on lofty trees where they are
brought near the sunlight, and such are called "epiphytes,"
Fig. 208.
Cypripedium.
242 PLANT FAMILIES: MONOCOTYLEDONS.
A number of species of orchids are distributed in temperate
regions.
393. Cypripedium or lady-slipper. — One species of the lady-
slipper is shown in fig. 208. The labellum in this genus is
shaped like a shoe, as one can see by the section of the flower
in fig. 209. The stigma is situated at st, while the anther is
situated at a, upon the style. The insect enters about the
middle of the boat-shaped labellum. In going out it passes up
and out at the end near the flower-stalk. In doing this it
passes the stigma first and the anther last, rubbing against
both. The pollen caught on the head of the insect will not
touch the stigma of the .same, but will be in a position to come
in contact with the stigma of the next flower visited.
Exercise 65.
394. The orchid. — Take one of the orchids, the lady-slipper (cypripedium)
for example, and make out the parts of the flower, and the relation of the
different members. Study the structure of the flower with reference to the
pollination by insects, with the aid of the text, and determine the course
which the insect takes to effect cross-pollination.
Material. — Entire plants in flower, including the bulb. This is usually
buried deep in the soil, and should be collected fresh if possible. Some of
the smaller plants, not in flower, should also be at hand. The plant flowers
during May in the northeastern United States. It is represented in other
sections by different species. In sections where a species of this genus cannot
be obtained another of the orchis family may be employed. (Apparatus. Dis-
secting microscopes, or tripod lenses (the former are better), dissecting nee-
dles, scalpel. The apparatus will not be repeated for the following exercises.)
CHAPTER XXXIX.
MONOCOTYLEDONS (CONTINUED).
Topic II: Monocotyledons with flowers on a Spadix
(Spadiciflorae).
395. Lesson II. The arum family (aracese). — This family is
well represented by several plants. The skunk's cabbage
(Spathyema foetida), the " jack-in-the-pulpit, " also called
" Indian-turnip " (Arisaema triphyllum), shown in fig. 210, the
water arum (Calla palustris), and the sweet flag (Acorus cala-
mus) are members of this family, as also are the callas and
caladiums grown in conservatories. The parts of several of the
species of this family, especially the corm of the Indian turnip,
are very acrid to the taste. The floral parts are more or less
reduced.
396. Relatives of the arum family. — Related to the arum
family are the "duckweeds." Among the members of this
family are the most diminutive of the flowering plants, as well
as the most reduced floral structures.
Other related families are the cat -tails and palms. In the
latter the spathe and spadix are of enormous size. The cocoa-
nut is the fruit of the cocoanut palm.
Exercise 66.
INDIAN-TURNIP.
397. Staminate plants (sometimes called male plants). — Sketch an entire
plant showing the corm (the thickened perennial stem), the annual shoot with
leaves and spathe. Cut away one side of the spathe to expose the long com-
pact cluster of staminate (spadix) flowers within. Sketch the spadix, showing
the mass of stamens as well as the sterile part of the shoot above. Dissect off
from the axis several of the stamens. Note that the filament is very short,
and that the anther is irregularly lobed.
243
244 PLANT FAMILIES : MONOCOTYLEDONS.
398. The pistillate plants (sometimes called female plants). — Compare
with the staminate plant. How many leaves are there ? Is the number of
leaves constant on all the pistillate plants ? Cut away one side of the spathe
and expose the spadix of pistillate flowers. Sketch. Observe that each
flower consists of a single flask-shaped pistil, and that these are packed closely
together. Note the delicate brush-like stigma. Search for plants which
show both stamens and pistils on the same spadix. Where both kinds of
flowers are present on the same spadix, on what part of the spadix does each
kind appear? On the corm of different plants search for lateral buds, which
are young plants. Observe that they usually arise on directly opposite sides
of the corm ; that they easily become freed from the old corms ; that they
are young corms. Do they arise in the axils of the leaves or scale leaves
which have fallen away ?
Cut off a portion of the corm. Do not eat any portion but touch the
tongue to the cut surface. The flesh of the corm is very acrid.
DESCRIPTION OF THE INDIAN-TURNIP.
399. Indian-turnip. — The "Indian-turnip," or " jack-in-
the-pulpit " (Arisaema triphyllum), loves the cool, shady, rich,
alluvial soil of low grounds, or along streams, or on moist
hillsides. A group of the jacks is shown in figure 210 as they
occur in the rich soil on dripping rocks in one of our glens.
At their feet is a carpet of moss. Often the violet sits humbly
underneath its spreading three-parted leaves. The thin, strap-
shaped spathe, unfolded at its base, bends gracefully over the
spadix, the sterile end of which stands solitary in the pulpit
thus formed. The flowers are very much reduced, i.e., the
number of members in the sets is reduced so that they do not
appear in threes as in the typical monocotyledons. Some of
the members are also often reduced in size or are rudimentary.
The plants are " dimorphic " usually.
400. Female plants. — The large plants usually bear the
pistillate flowers, which are clustered around the base of the
spadix, each flower consisting of a single pistil, oval in form,
terminating in a brush-like stigma. The stigma consists of
numerous spreading, delicate hairs. The open cavity of the
short style is hairy also, and a brush of hairs extends into the
cavity of the ovary. Into this brush of internal hairs the necks
ARACE&.
245
of the several ovules crowd their way to the base of the style
near its opening. Even when the stigma is not pollinated the
Fig. 210.
A group of jacks.
ovary continues to grow in size, and the stigmatic brush remains
fresh for a long time.
246 PLANT FAMILIES: MONOCOTYLEDONS.
401. Male plants, — Excepting some of the intermediate sizes,
one can usually select on sight the male and female plants.
The smaller ones which have a spathe are nearly all male and
bear a single leaf, though a few have two leaves. The male
flowers are also clustered at the base of the spadix, and are very
much reduced. Each flower consists only of stamens, and
singularly the stamens of each flower are joined into one com-
pound stamen, the anther-sacs forming rounded lobes at the
end of the short consolidated filaments.
402. The female plants require more food than the male
plants. — In some plants both male and female flowers occur on
a single spadix, the lower flowers being female, while the upper
ones are male. The larger plants are nearly all female, and
many, though not all, bear two leaves. In this dimorphism of
the plant there is a division of labor apportioned to the destiny
and needs of each, and in direct correspondence with the
capacity to supply nutriment. The staminate flowers, being
short-lived, need comparatively a small amount of nutriment,
and after the escape of the pollen (dehiscence of the anthers)
the spathe dies, while the leaf remains green to assimilate food
for growth of the fleshy short stem (corm), where also is stored
nutriment for the growth in the autumn and spring when the
leaf is dead. The female plants have more wrork to do in
providing for the growth of the embryo and seed, in addition
to the growth of the corm and next season's flower. The
smaller female plants thus sometimes exhaust themselves so in
seed bearing that the corm becomes small, and the following
season the plant is reduced to a male one.
403. Growth and death of the corm. — The new roots each
year arise from the upper part of the corm. The stored sub-
stances in the base of the corm are used in the early season's
growth, and the old tissue sloughs off as the new corm is formed
above upon its remains.
Material. — Freshly collected plants should be used, the entire plant ; .small
ones as well as large ones. •
CHAPTER XL.
MONOCOTYLEDONS (CONCLUDED).
Topic III: Monocotyledons with a glume subtending
the flower (Glumiflorae).
404. Lesson III, Grass family (gramineae). Oat. — As a
representative of the grass family (gramineae) one may take the
oat plant, which is widely cultivated, and also can be grown
Fig. 215.
Flower of
oat, showing
the upper
Fig. 211. Fig. 212. Fig. 213. Fig. 214.
Spikelet of One glume re- Flower opened Section show-
oat showing moved showing showing two palets, ing ground plan palet behind,
two glumes. fertile flower. three stamens, and of flower, a, axis, and the two
two lodicules at base
of pistil.
lodicules in
front.
readily in gardens, or perhaps in small quantities in greenhouses
in order to have material in a fresh condition for study. Or we
247
248
PLANT FAMILIES : MONOCOTYLEDONS.
may have recourse to material preserved in alcohol for the
dissection of the flower. The plants grow usually in stools;
the stem is cylindrical, and marked by distinct nodes as in the
corn plant. The leaves possess a sheath and blade. The
flowers form a loose head of a type known as a panicle. Each
little cluster as shown in fig. 211 is a spikelet, and consists
usually here of one or two fertile flowers below and one or two
undeveloped flowers above. We see that there are several
series of overlapping scales. The two lower ones are
" glumes/' and because they bear no flower in their axils are
empty glumes. Within these empty glumes and a little higher
on the axis of the spike is seen a boat-shaped body, formed of
a scale, the margins of which are folded around the flowers
within, and the edges inrolled in a peculiar manner when
mature. From the back of this glume is borne usually an awn.
If we carefully remove this scale, the " flower glume," we find
that there is another scale
on the opposite (inner)
side, and much smaller.
This is the "palet."
Next above this we
have the flower, and the
most prominent part of
the flower, as we see, is
the short pistil with the
two plume-like styles, and
the three stamens at fig.
213. But if we are careful
in the dissection of the
parts we shall see, on look-
ing close below the pistil
on the side of the flower-
ing glume, that there are two minute scales (fig. 215). These are
what are termed the lodicules, considered by some to be merely
bracts, by others to represent a perianth, that is two of the
--GL
Fig. 216.
Diagram of oak spikelet. G7, glumes ; B, palets
A, abortive flower.
GRAMINEAE. 249
sepals, the third sepal having entirely aborted. Rudiments of
this third sepal are present in some of the gramineae.
405. Other members of the grass family. — To the gramineae
belong also the wheat, barley, corn, the grasses, rice, etc. It
is one of the most important families from an economic stand-
point, furnishing a great variety of food for man and other
animals. The gramineae, while belonging to the class mono-
cotyledons, are less closely allied to the other families of the
class than these families are to each other. For this reason
they are regarded as a very natural group.
Exercise 67.
406. The wheat (Triticum sativum vulgare). — The wheat plant may be
studied as an alternate for the oat plant.
The entire wheat plant. — Study the entire wheat plant, and compare with
the oat plant. Are the stems of the wheat single or are stools formed?
Since a germinating grain of wheat forms at first but a single stem, how are
the stools formed ? Examine young wheat plants to determine this.
The inflorescence, — The " head " of wheat forms a single spike. Sketch a
spike. Remove a few of the spikelets, and note the jointed and zigzag char-
acter of the axis (rachis) of the spike ; note the attachment of the spikelets.
The spikelets.— Note the empty glumes at the base ; determine how many
flowers there are in a spikelet. How many flowering glumes and palets are
there to each flower ? In a mature head of wheat determine how many of
the flowers in a spikelet ripen grain, and how many are sterile ? Are there
any of the spikelets which are completely sterile ? Where are they located ?
Using a head of wheat at the time of flowering, spread apart the members
of a flower with the aid of dissecting needles, and sketch the parts of the
flower, showing the glume, palet, the three stamens, and the pistil with the
plumose styles. Endeavor to find the lodicules. (See the description of the
oat flower for comparison.)
Sketch an empty and a flowering glume to show the " nerves" and awns.
Compare the grain of wheat with a grain of corn. (See paragraph 9.)
Material. — Entire stools of young, fresh plants (may be obtained at any
time during autumn, winter, or spring) ; mature plants in flower (if they can-
not be obtained fresh they may be dried, preserving at the same time some of
the flowering heads in alcohol or formalin) ; ripe heads of wheat.
CHAPTER XLI.
DICOTYLEDONS.
Topic IV: Dicotyledons with distinct petals, flowers
in catkins, or aments; often degenerate.
ORDER AMENTIFER^.
407. Lesson IV. The willow family (salicacese).— The wil-
lows represent a very interesting group of plants in which the
Fig. 2.7.
Spray of willow leaves, pistillate and staminate catkins (Salix discolor).
flowers are greatly reduced. The flowers are crowded on a
more or less elongated axis forming a catkin, or ament. The
250
SALICACE^E. 251
ament is characteristic of several other families also. The
willows are dioecious, the male and female catkins being borne
on different plants. The catkins appear like great masses of
either stamens or pistils. But if we dissect off several of the
flowers from the axis, we find that there are many flowers, each
one subtended by a small bract. In the male or "sterile"
catkins the flower consists of two to eight stamens, while in the
female or ' ' fertile ' ' catkins the flower consists of a single pistil.
The poplars and willows make up the willow family.
Exercise 68.
408. The willow (Salix discolor).
The leafy shoot. — Determine the arrangement of the leaves of the willow ;
sketch a leaf showing its form, the character of the margin, and of the vena-
tion. If different willows are at hand compare the color of the twigs, as well
as the character of the twigs as to brittleness or litheness.
The inflorescence. — What is the kind of inflorescence? Are both kinds of
flowers borne on the same ament (catkin), or on different aments ?
The staminate catkins. — Determine what constitutes a flower by dissect-
ing some of them off from the axis of the catkin. What parts of the flower
are present ? How many stamens in a flower ? If a hand lens is convenient
use it in making out the form of the parfs. Sketch a flower in its position on
the axis of the catkin, showing also the bract at the base of the flower. De-
scribe the character of the bract as seen under the lens.
The pistillate catkin.— WThat parts of the flower are present? Compare
with the staminate flower. Sketch a pistillate flower with the subtending
bract to sliow the form of the ovary, with the divided stigma. Is the pistil
sessile or stalked ? How many carpels make up the pistil ? Is there a small
gland (nectary) present near the base of the ovary which represents the peri-
anth ? Is there a nectary on the staminate flower?
The fruit. — Examine ripe pods of the willow. Determine what parts of
the flower unite to form the fruit. What difference between a fruit and seed
in the willow ? What means is provided for the dissemination of the seeds ?
Field observations on the willows. — At what time do the catkins of the
willow appear? Do they flower before the leaves appear? At time of flow-
ering note the character and abundance of the pollen from the stamens. Is it
in the form of " dust," or is it adhesive? How are the willows pollinated?
Do insects visit the willow flower ? Are willows easily propagated by shoots ?
What happens it a willow branch is stuck into damp soils ; when it is left in
the water for some time ?
PLANT FAMILIES: DICOTYLEDONS.
Material.— Shoots of the willow, some with leaves, some with the catkins
(the two kinds of catkins occur on different plants). If material cannot be
obtained fresh when wanted for study, the leafy shoots may be preserved dry,
and the catkins in alcohol or formalin, or dry. Ripe fruit should also be at
hand ; this may be preserved dry.
ORDER AMENTIFER^E.
409. Lesson V. The oak family (cupuliferae). — A small
branch of the red oak (Quercus rubra) is illustrated in fig. 218.
Fig. 218.
Spray of oak leaves and flowers. Below at right is staminate flower, at left pistillate
flower.
This is one of the rarer oaks, and is difficult for the beginner
to distinguish from the scarlet oak. The white oak is perhaps
CUPULIFERJE. 253
in some localities a more convenient species to study. But for
the general description here the red oak will serve the purpose.
Just as the leaves are expanding in the spring, the delicate
sprays of pendulous male catkins form beautiful objects. The
petals are wanting in the flower, and the sepals form a united
calyx, with several lobes, that is, the parts of the calyx are
coherent. In the male flowers the calyx is bell-shaped and
deeply lobed. The pendent stamens, variable in number, just
reach below its margin. The pistillate or female flowers are
not borne in catkins, but stand on short stalks, either singly or
a few in a cluster. The calyx here is urn-shaped with short
lobes. The ovary consists of three united (coherent) carpels,
and there are three stigmas. Only one seed is developed in the
ovary, and the fruit is an acorn. The numerous scales at the
base of the ovary form a scaly involucre, the cup.
The beech, chestnut, and oak are members of the oak
family.
410. Other ament bearers. — The following additional fam-
ilies among the ament bearers are represented in this country:
the birch family (birch, alder), the hazelnut family (hazelnut,
hornbeam, etc.), walnut family (hickory, walnut), and the
sweet-gale family (myrica).
Exercise 69.
411. The oak. — (The white oak or any common one in the neighborhood.)
The leaves. — Determine the arrangement of the leaves on the shoot.
Sketch a leaf showing the form, outline, and venation. Compare the young
leaves with the old ones as to texture, surface characters, etc.
The inflorescence. — What is the kind of inflorescence ? Are both kinds of
flowers in the same inflorescence or in different inflorescences ?
The staminate inflorescence. — Note the cluster of staminate aments. De-
termine a single flower and sketch it to show the parts. What parts of the
flower are present ? Determine the number of parts of each set present.
The pistillate inflorescence.— How does it differ from the staminate in-
florescence? Sketch a pistillate flower, showing the parts. What parts of
the flower are present ?
The fruit (an acorn with the cup). — Sketch an acorn in the "cup."
254 PLANT FAMILIES: DICOTYLEDONS.
What is the homology of the cup? i.e., to what part or series of members of
the plant does it belong? Could the pistillate flower of the ancestors of the
oak have been in the form of aments, and if so could the cup of the acorn
represent the degraded and consolidated ament? If so, what part of the
ament would now be represented in the cup ? (It has also been suggested
that the scales of the involucre which make up the cup are adventitious
growths accompanying the development of the fruit.)
(If the acorn has not been studied under the paragraph dealing with seeds
and fruits, and if there is time now, remove the wall of the acorn and deter-
mine the parts of the embryo. Are any parts of the embryo green while still
enclosed within the acorn ?
Field observations on the oaks.— Compare the time of appearance of the
flowers and leaves of the oak. What about the abundance of the pollen ?
How are the oaks pollinated? The ament-bearing plants are usually wind
pollinated, and for this reason there is an abundance of pollen, and always in
the form of dust. Is there an exception to this general rule ? How long
after the flowers are formed before the acorn is ripe ?
If there is time during excursions note other ament-bearing plants.
Material. — Mature leave's, leafy shoots, sprays of the flowers, both pistillate
and staminate ; fruit (the acorn in the cups).
CHAPTER XLII.
DICOTYLEDONS (CONTINUED).
Topic V: Dicotyledons with distinct petals and
hypogynous flowers.
ORDER URTICIFLOR^E.
412, Lesson VI. The elm family (ulmaceae). — The elm tree
belongs to this family. The leaves of our American elm
(Ulmus americana) are ovate, pointed, deeply serrate, and with
an oblique base as shown in fig. 219. The narrow stipules
Fig. 219.
Spray of leaves and flowers of the American elm ; at the left above is section of flower,
next is winged seed (a samara).
which are present when the leaves first come from the bud soon
fall away. The flowers are in lateral clusters, which arise from
255
256 PLANT FAMILIES: DICOTYLEDONS.
the axils of the leaves, and appear in the spring before the
leaves. They hang by long pedicels, and the petals are absent.
The calyx is bell-shaped, and 4-9-cleft on the margin. The
stamens vary also in number in about the same proportion.
A section of the flower in fig. 219 shows the arrangement of the
parts, the ovary in the centre. The ovary has either one or
two locules, and two styles. The mature fruit has one locule,
and is margined with two winged expansions as shown in the
figure. This kind of a seed is a samara.
Exercise 7O.
413. The elm (Ulmus anrericana).
Leaves. — What is the arrangement of the leaves on the shoot? Sketch a
leaf showing its attachment to the shoot, and the relation of the stipules ;
note how easily the stipules fall away.
The inflorescence. — Describe the inflorescence ; a single flower ; sketch a
single flower in the position in which it stands on the tree. Cut away the
floral envelope on one side ; determine the number of stamens ; the number
of pistils ; are the pistils single or compound ? Of how many carpels is it
composed ? Sketch a flower with the front part of the envelope and the front
stamens removed. What part of the floral envelope is present ? What is its
character and form ? What are the relations of the sets of the flower to each
other ? In time of appearance how do the flowers compare with the leaves ?
Describe the mature fruit ; how many seed are present? What parts of
the flower are united in the fruit ? What is the fruit called ?
Materials. — Spray of leaves and flowers; it maybe necessary to collect
them at different times. Leafy shoots should be collected while some of the
leaves are still young in order to preserve some with the stipules, and they
may be preserved dry and pressed. Fruits collected at the time of maturity
may be preserved dry.
OREER POLYCARPIC.&.
414. Lesson VII. The crowfoot family (ranunculaceae).—
The marsh-marigold (Caltha palustris) is a member of this
family. The leaves are heart-shaped or kidney-shaped, and the
edge is crenate. The bright golden-yellow flowers have a
single whorl of petal-like envelopes, and according to custom
in such cases they are called sepals. The number is not
RANUNCULA CE&.
257
definite, varying from five to nine usually. The stamens are
more numerous, as is the general rule in the members of the
family, but the number of the pistils is small. Each one is
separate, and forms a little pod when the seed is ripe. The
marsh-marigold, as its name implies, occurs in marshy or wet
places and along the muddy banks of streams. It is one of the
common flowers in April and
May.
Exercise 7 1 .
415. The Buttercup. — If preferred, a
species of buttercup may be studied instead
of the marsh-marigold, but a comparison
with the latter is de-
sirable.
The entire plant.
— Describe form and
habit of the plant ;
the character of the
stem ; branching ;
the form and arrangement of the
leaves ; the character of the roots
(these characters will depend on the
species).
The inflorescence. — What kind of in-
florescence ? What parts of the flower
are present? Describe the color and
form of members of the different sets of
the flower. Determine the number of
members in each set (approximately if not ac-
curately).
Sketch
Fig. 220.
Caltha palustris. marsh-mari-
gold.
Fig. 221.
Diagram of marsh-marigold
flower.
a sepal, a petal (is a nectar gland pres-
ent?), a stamen, and a pistil, noting carefully the characters of each.
Do the stamens all ripen their pollen at the same time ? Is there any ad-
vantage as regards the time of ripening of the stamens ?
What is the relation of the members of a set among themselves ? What is
the relation of the sets to each other ?
Is the flower perfect or imperfect ; complete or incomplete ? Is it regular
or irregular ; hypogynous, perigynous, or epigynous ? Are the parts of the
flower free and distinct, or adherent, or coherent ?
258 PLANT FAMILIES: DICOTYLEDONS.
If fruit is present determine the number of seed in a ripe fruit ; and also
what parts of the flower make up the fruit.
If there is time a comparison of the flowers, fruit, and leaves of different
species of the ranunculus will be found interesting, especially species from
dry and wet ground as well as some of the species which grow in the
water.
Construct the formula for the buttercup flower ; also construct the floral
diagram.
Material. — Entire plants, some flowering stems with flowers, some with
fruit. Fresh material when possible.
THE BUTTERCUP (RANUNCULUS).
416. Other crowfoots. — Many of the crowfoots or buttercups
(ranunculus) with bright yellow flowers grow in similar situa-
tions. The "wood anemone" (anemone), small plants with
white flowers, and the rue anemone (anemonella), which resem-
bles it, both flower in woods in early spring. The common
virgin's bower (Clematis virginiana) occurs along streams or on
hillsides, climbing over shrubs or fences. The vine is some-
what woody. The leaves are opposite, petioled, and are com-
posed of three leaflets, which are ovate, three-lobed, and usually
strongly toothed, and somewhat heart-shaped at the base. The
flower clusters are borne in the axils of the leaves, and therefore
may also be opposite. The clusters are much branched, form-
ing a convex mass of beautiful whitish flowers. The sepals are
colored and the petals may be absent, or are very small. The
stamens are numerous, as in the members of the crowfoot
family. The pistils are also numerous, and the achenes in fruit
are tipped with the long plumose style, which aids them in
floating in the air.
417. Character of the raimnculacese. — Some of the charac-
ters of the ranunculaceae we recognize to be the following: The
plants are mostly herbs, the petals are separate, and when the
corolla is absent the sepals are colored like a corolla. The
stamens are numerous, and the pistils are either numerous or
few, but they are always separate from each other, that is they
are not fused into a single pistil (though sometimes there is but
CRUCIFER&. 259
one pistil). All the parts of the flower are separate from each
other, and make up successive whorls, the pistils terminating
the series. When the seeds are ripe the fruit is formed, and
may be in the form of a pod, or achene, or in the form of a
berry, as in the baneberry (actaea).
ORDER RHCEADIN^E.
418. Lesson VIII. The mustard family (cruciferae). — This
is well represented by the toothwort (dentaria), which we
studied in a former chapter. (If the toothwort has been
studied, the shepherd 's-purse may be omitted.)
Exercise 72.
419. The Shepherd's purse (Capsella bursa-pastoris). — If it is desired to
study a species besides the toothwort the shepherd' s-purse will answer. It
is a common and widely distributed species, found in waste places and in
fields.
The entire plant. — Note and describe the habit and character of the plant,
i.e., the size, character of branching, character of the root, position and ar-
rangement of the leaves. Compare the "radicle" (lower) leaves with the
" cauline " (stem) leaves as to form, and insertion. The radicle leaves are
more or less deeply lobed or pinnatifid (pinnately cut), while the stem leaves
are slender, lanceolate, toothed, and often auricled (with little ears) at the base.
The inflorescence. — What is the kind of inflorescence? Determine the
parts of the flower present, as well as the number and arrangement of the
members of the flower. What figure do the petals make in the flower, which
suggests the name of the family to which the shepherd's purse and the tooth-
wort belong ?
The fruit. — What parts of the flower are united in the fruit? Compare the
plant with the toothwort.
Construct the floral diagram of the toothwort or shepherd's purse, or of
other cruciferous plant studied.
Material. — Entire plants with flowers and fruit. The plant occurs from
early spring to autumn, and can be usually obtained in a fresh condition when
wanted.
The exercise on the violet may be omitted unless it is desired
to study it in connection with some field observations, and for
the purpose of observing " cleistogamous " flowers, when the
outline here given will answer.
260 PLANT FAMILIES : DICOTYLEDONS.
ORDER CISTIFLOR/E.
420. The violet family (viblaceae), — The violet family is
represented by the common blue violet, the yellow violet, the
pansies, heart's ease, sweet violet, etc.
Exercise 73.
421. The blue violet (Viola cucullata).
The entire plant. — Describe the character and habit of the plant, the short
underground stem, the " radicle" leaves, the erect flower scapes which bear
the conspicuous blue flowers, and the short, curved stems beneath the soil or
debris which bear the closed inconspicuous flowers. Sketch a leaf, showing
the form and venation. What is the form of the leaf and the character of
the margin ?
The blue flowers. — Sketch a flower. Is the flower regular or irregular?
complete or incomplete ? perfect or imperfect ?
The calyx. — Describe the form of the calyx ; how many sepals are indi-
cated ?
The corolla. — How many petals are present ? Remove them and note care-
fully the form of each one and the position in the flower. In the " spurred"
one look for nectar glands.
The stamens. — Determine the number of the stamens. Are they united
together by their anthers ? If so the stamens are said to be syngenecious.
Are the stamens of different sizes ? Describe the fonn of the different ones
and the relation of certain peculiar ones to the spur of the corolla.
The pistil. — Describe the form of the pistil and the relation of the stamens
and pistils.
The closed (cleistogamous) flowers. — These are on shorter, curved, scapes
which hold them beneath the soil or' debris- Compare them with the blue
flowers. What parts of the flower are absent ?
The fruit. — Make a cross-section of the fruit and determine how many car-
pels are represented in the pistil. Note the numerous seeds.
Pollination of violets. — If a sweet violet flower, or the flowers of the pansy
are convenient, study the stamens and pistil of the open flowers. Remove the
corolla, and note the position of the anthers with reference to the pistil.
Note the peculiar enlarged stigma with an opening in front, and the lip below.
Move a pencil into a flower, endeavoring to imitate the entrance of an insec
and try to determine how cross-pollination takes place. Compare the blue
flowers of the blue violet.
The small closed flowers are called cleistogamous, and they are self-polli-
VIOLA CEJ£.
26l
nated, because being closed, and because of the position of the anthers around
the stigma the pollen from the opening anthers comes directly in contact with
the stigma. In the flowers of the pansy cross-pollination often takes place
Fig. 222.
Viola cucullata ; blue flowers above, cleistogamous flowers smaller and curved below.
Section of pistil at right.
through the agency of insects. While the blue flowers of the blue violet
rarely set fruit, nevertheless pollination and fertilization do take place in some
of the flowers, though fruit sets more abundantly in the cleistogamous flowers.
Material. — Entire plants with the flowers ; collect some early in the season
when the blue flowers are abundant, and some later when the small flowers
underneath the soil or leaves are formed. Mature fruit is also desirable.
CHAPTER XLIII.
DICOTYLEDONS (CONTINUED).
Topic VI: Dicotyledons with distinct petals and
perigynous or epigynous flowers.
Many trees and shrubs.
ORDER
422, Lesson X. The maple family (aceraceae). — Figure 223
represents a spray of the leaves and flowers of the sugar maple
Fig. 223.
Spray of leaves and flowers of the sugar maple.
(Acer saccharinum), a large and handsome tree. The leaves
are opposite, somewhat ovate and heart-shaped, with three to
262
ACERACE&.
263
five lobes, which are again notched. The clusters of flowers
are pendulous on long hairy pedicels. The petals are wanting.
The calyx is bell-shaped
and several times lobed,
usually five times. The
stamens are variable in
number. The ovary is
two-lobed and the style
deeply forked. The fruit
forms two seeds, each with Fig. 224.
a loner wincr like pvnarminn Seeds and flowers of sugar maple. Attherightis
a long wmg-llKC expan 1 a pistil,ate flower? in lhe ^iddlepa staminate flower,
as shown in the figure. and at the left the two seecls forming a samara.
The flowers of the maple are polygamo-dioecious, that is the
male members (stamens) and female members (carpels) may be
in the same flower or in different flowers.
Exercise 74.
423. The sugar maple (Acer saccharinum).— (Another species may be
studied if desired. )
Leaves. — Determine the form and arrangement of the leaves; sketch a leaf.
Inflorescence. — Describe the character of the inflorescence ; sketch a
flower cluster.
Flowers. — Select several different flowers, some from different trees, and
compare them carefully to see if the members of the flower are the same in
all. Sketch several to show the general character.
What parts of the flower are present ? Describe the form and character of
each set of members, and their relation to each other. Determine the number
of members in each set and their relations among themselves. Study several
flowers to make this out.
The fruit. — Sketch a fruit. What parts of the flower are united in the
fruit?
If there is time it will be found instructive to compare the flowers of an-
other species of maple, like the red maple, with the sugar maple. Examine
different flowers from several different trees in order to compare the different
sizes of the stamens and pistils in different flowers, and the facts with refer-
ence to the presence or absence of any of the members in certain of the
flowers. Compare the leaves of the red maple with those of the sugar maple
also.
264 PLANT FAMILIES: DICOTYLEDONS.
Materials. — Leafy shoots, either fresh or pressed and dried. Flowers;
fresh as they appear in the spring ; if they cannot be studied immediately they
may be preserved in alcohol or in formalin. They are better fresh.
Fruits, collected in the autumn and preserved riry.
Omit the study of the horse chestnut, unless it is desired to
study it instead of the maple, since it belongs to the same order.
424. The buckeye family (hippocastanaceae), — The horse
chestnut (^Esculus hippocastanum) is largely planted in the
Northeastern United States as an ornamental tree. It is also
self-seeding in waste places. The family is represented in
other places by other species, the buckeye, from which the
family gets its common name, for example occurs in Ohio (the
Buckeye State).
Exercise 75.
425. The horse chestnut ( JEsculus hippocastanum).
The leaves. — Note the form and arrangement of the leaves. Sketch a leaf
to show its form and the parts. What kind of a leaf is it ?
The inflorescence (mixed racemose). — The flowers. What parts of the
flower are present? Is the flower complete or incomplete ; regular or irreg-
ular ; perfect or imperfect ?
Describe the calyx ; the corolla ; describe a petal, its form and color.
How many petals present ?
The stamen. — How many present ? Sketch a stamen.
The pistil. — Describe the form of the pistil, its parts ; how many carpels
are represented in the pistil ? What is the character of the surface of the
ovary ?
The mature fruit. — What is the character of the surface of the mature
fruit ? Describe the form of the fruit. What parts of the flower are united
to form the fruit ? What is the difference between the fruit and a seed in the
horse chestnut? Examine the embryo in the seed ; note its large cotyledons
and the well developed hypocotyl. Why is the embryo not good for food for
man?
Construct the floral diagram of the horse-chestnut flower.
Material. — Sprays of leaves and flowers, collected fresh. Mature fruits.
CHAPTER XLIV.
DICOTYLEDONS (CONTINUED).
ORDER ROSIFLOR^E.
426. Lesson XI. — The rose-like flowers are an interesting
and important group. In all the members the receptacle (the
end of the stem which bears the parts of the flower) is an im-
portant part of the flower. It is most often widened, and
either cup-shaped or urn-shaped, or the centre is elevated.
The carpels are borne in the centre in the depression, or on the
elevated central part where the receptacle takes on this form.
The calyx, corolla, and the stamens are usually borne on the
margin of the widened receptacle, and where this is on the
margin of a cup-shaped
or urn-shaped recep-
tacle they are said to
be perigynous, that is,
around the gynoecium.
The calyx and corolla
are usually in fives.
There are three families,
Fig. 225.
Perigynous flower of spiraea (S. lanceolata). (From
Warming.)
as follows.
427. The rose family
(rosacese). — In this family there are five types, represented by
the following plants and illustrations: ist. In spiraea (fig. 225)
the receptacle is cup-shaped. There are five carpels, united at
the base, but free at the ends. 2d. In the strawberry the
receptacle is conic and bears the carpels (fig. 226). The conic
receptacle becomes the fleshy fruit, with the seeds in little pits
265
266
PLANT FAMILIES: DICOTYLEDONS.
Fig. 226.
Flower of Fragaria vesca with columnar
receptacle. (From Warming.)
over the surface. 3d. The raspberries, blackberries, etc.,
represented here by the flower-
ing raspberry (Rubus odoratus),
fig. 227. 4th. This is repre-
sented by the roses. The re-
ceptacle is urn-shaped and con-
stricted toward the upper por-
tion, with the carpels enclosed
in the base (fig. 228). 5th.
Here the receptacle is cup-
shaped or bell-shaped and nearly closed at the mouth as in the
agrimony.
428. Lesson XII. The almond or plum family (amygdala-
). — The members of this family are trees or shrubs. The
common choke-cherry (fig.
229) will serve to represent
one of the types. The
flowers of this species are
borne in racemes. The
receptacle is cup-shaped.
Only one seed in the single
Fig. 227.
Flowering raspberry (Rubus odoratus).
Fig. 228.
Perigynous flower of rosa. with
contracted receptacle. (From
Warming.)
carpel (sometimes two carpels) matures as the calyx falls away.
ROSIFLOR&.
26;
The outer portions of the ovary become the fleshy fruit, while
the inner portion becomes the hard stone with the seed in the
centre. Such a fruit is a drupe.
The floral formula for this family is as follows:
Ca5,Co5,Ai5-20 or 3o,Gi.
429, Lesson XIII. The apple family (pomacese).— This
family is represented by the apples, pears, quinces, june-berries,
Fig. 229.
Choke-cherry (Primus virginiana). Leaves,
flower raceme, and section of flower at right.
hawthorns, etc. The members are trees or shrubs. The
receptacle is somewhat cup-shaped and hollow. The perianth
and stamens are at first perigynous, but become epigynous
268 PLANT FAMILIES: DICOTYLEDONS.
(upon the gynoecium) by the fusion of the receptacle with the
carpels. The floral formula is thus Ca5, €05, A 10-5-5 or
Fig. 230.
Flower of pear. (After Warming.)
10-10-5,01-5. The carpels are united, but the styles are free.
In fruit the united carpels fuse more or less with the receptacle.
Omit either the strawberry, or the apple, as an exercise, if
desired.
Exercise 76.
430. The strawberry (Fragaria vesca).
Describe the appearance of the entire plant. What different stems are
there ? What purpose does each kind of stem serve ? Sketch and describe a
leaf.
The inflorescence. — WThat is the kind of inflorescence ?
The flower. — Determine the parts of the flower present. Describe each
set of members of the flower, naming the kind of calyx and corolla. Are the
sets of members free ? Are the members of each set distinct ? To take the
flower as a whole in its young condition (just opening) what is the relation as
regards position and elevation of the different sets to each other? Is the
flower perigynous or hypogynous ?
What is the end of the stem called to which the parts of the flower are
attached ?
Do all the flowers of the strawberry form fruit ? When you have deter-
mined this, determine the reason if you can.
The fruit. — What parts of the flower are united to form the fruit ? What
is such a fruit called ? What part of the flower forms the fleshy part of the
fruit ? What parts of the flower are united in the seed ? What is such a
seed called ?
LEGUMINOSM.
269
How does seed distribution come about in such plants as the strawberry?
How are strawberry plants usually propagated?
Materials. — Entire plants with runners : flowers ; fruit.
Exercise 77.
431. The apple (Pyrus malus).
Leaves. — Determine the arrangement of the leaves on the shoot ; sketch a
leaf.
The inflorescence. — Determine the kind of inflorescence.
The flower. — Study several flowers to compare the variation in the number
of the parts or members of the flower. What parts of the flower are present ?
Make a long section of the flower and sketch showing the parts and their
relation to each other.
Determine the number of members in each set ; the relation of the members
of a set to each other ; the relation of the sets among themselves. Give the
names which are applied to these relations.
The fruit. — What parts of the flower are united in the fruit? Make
longitudinal and cross-sections of an apple, name the parts and show from
which part of the flower each part of the fruit comes. What is the fruit of an
apple-tree called ?
Materials. — Spray of leaves and flowers ; mature fruit.
ORDER LEGUMINOS/E.
432. Lesson XIV. The pea family (papilionaceae). — This
family is well represented by the common pea. The flower is
butterfly-like or papilionaceous, and the showy part is made up
Fig. 231.
Details of pea flower ; section of flower, perianth removed to show the diadelphous
tamens, one single one, and nine in the other group. (From Warming.)
270
PLANT FAMILIES: D ICO >7 'Y 'LED ON S.
Fig. 232.
Corolla of pea. S. stand-
ard ; W, wings ; A", two
petals forming keel.
of the five petals. The petals have received distinct names here
because of the position and form in the flower. At fig. 232 the
petals are separated and shown in their corresponding positions,
and the names are there given. The flower
is irregular and the parts are in fives, except
the carpel, which is single. The calyx is
gamosepalous (coherent), the corolla poly-
petalous (distinct). The ten stamens are
in two groups, one separate stamen and
nirie united ; they are thus diadelphous
(two brotherhoods). The fruit forms a pod
or legume, and at maturity splits along
both edges.
There are three families in the legume-
bearing plants : ist, including the locust?,
cassias, etc. ; 2d, the pea family, including peas, beans, clovers,
ground-nuts, or peanuts, vetches, desmodium, etc. ; 3d, in-
cluding the sensitive plants like mimosa.
Exercise 78.
433. The pea (Pisum sativum).
The entire plant. — Describe the entire plant, the branching, the means for
support (compare different cultivated varieties in respect to size, habit, and
means for support if practicable).
The leaf. — Sketch a leaf; name the different parts; what kind of a leaf
is it? Does the leaf serve any purpose for the mechanical support of the
plant ? How ?
The inflorescence. — What is the kind of inflorescence ?
The flower. — Is it regular or irregular ?
The calyx. — Describe the calyx. How many sepals are indicated? Are
the sepals distinct or coherent ? What name is applied to this kind of a calyx ?
The corolla. —What are the relations of the petals to each other ? What
term is applied to indicate this relation ? Sketch a flower, and name the differ-
ent parts of the corolla ; what name is given to such a flower ?
The stamens (remove the corolla) ; how many stamens are there ? What
is their relation to each other ? What terms are used to indicate such a re-
lation of stamens to each other ?
The pistil. — How many carpels in the pistil? Is it simple or compound?
Sketch a young pistil, naming the parts.
MYRTIFLOR&.
The fruit. — What parts of the flower are united in the fruit? Describe the
fruit. What is such a fruit called ? How are the seeds freed ? What is the
difference between a fruit and a seed in the pea plant ?
The clover (trifolium). — If it is desired to study a clover, study one in a
similar way.
Nitrogen gatherers. — The pea,
clovers, etc., are often called nitrogen
gatherers (see Chapter XV). During
an excursion let the pupils dig up dif-
ferent leguminous plants, like the pea,
clover, lupine, etc. , and search for the
"tubercles" on their roots, compar-
ing the form of the tubercles on the
different kinds of plants.
Pollination. — If the flowers of cy-
tisus from a conservatory are at hand
attempt to press the point of a pencil
in between the parts of the keel in the
case of flowers where these parts are
still closed ; describe the action of the
stamens in throwing the pollen. How
could cross-pollination be brought
about in such a flower by the visits of
insects ?
Study the common lupine (Lupinus
perennis) in the same way. Study the
pea flower with the same object in
view ; has the pea flower become
adapted to self-pollination ?
Material. — Sprays of leaves and
flowers ; fruit. Material can usually
be obtained fresh early in the spring
and for some time later.
Fig. 233.
Section of flower
of CEnothera.
Topic VII: Dicotyledons with distinct petals and
epigynous flowers.
ORDER MYRTIFLOR^E.
(The study of the evening primrose may be omitted. )
434. Lesson XV. The evening-primrose family (onogracese).
—In the evening-primrose (oenothera) the flowers are arranged
2/2 PLANT FAMILIES: DICOTYLEDONS.
Fig- 234'
Evening primrose (CEnothera biennis) showing flower buds, flowers, and seed pods,
(From Kerner and Oliver.)
ONOGRACE&. 2/3
in a loose spike along the end of the stem, each one situated in
the axil of a leaf-like bract. The flowers of the family are very
characteristic, as shown here. They are sessile in the axil of
the bract, and the calyx forms a long tube by the union of the
sepals, only the end of the tube being divided into the indi-
vidual parts, showing four lobes. On the edge of the open end
of the calyx tube are seated the four, somewhat heart-shaped,
yellowish petals, and here are also seated the eight stamens.
The four carpels are united into a single pistil within the base
of the calyx tube and united with it, so that the calyx tube
seems to be on the end of the pistil. The flowers soon fade
and fall away from the pistil, and this grows into an elongated
four-angled pod. Since the lower flowers on the stem are the
older, we find nearly mature fruit and fresh flowers, with all
intermediate grades, on the same plant.
The plants grow by roadsides and in old fields. They are
from locm to a meter or more high (one to five feet). The
leaves are lanceolate or oblong, toothed and repand on the
margin. In many of the species of the family the parts of the
flower are in fours as in the evening primrose, but in others the
number is variable.
CHAPTER XLV.
DICOTYLEDONS (CONTINUED).
SYMPETAL/E.
435. In the remaining families the corolla is gamopetalout,
that is, the petals are coherent into a more or less well-formed
tube, though they may be free at the end. For this reason
they are known as the sympetala.
Topic VIII: Dicotyledons with united petals, flower
parts in five whorls.
ORDER BICORNES.
436. Lesson XVI. The whortleberry family (vacciniaceae),
—(This study may be omitted. ) — The common whortleberry,
or huckleberry (Gaylussacia resinosa), flowers in May and June.
The shrubs are from $ocm to i meter (1-3 feet) high, and are
much branched. The leaves are ovate, and when young are
more or less clammy from numerous resinous dots, from which
the plant gets its specific name (resinosa). The flowers are
borne on separate shoots from the leaves of the same season,
and hang in one-sided short racemes as shown in fig. 235.
The calyx is short, five-lobed, and adheres to the ovary. The
corolla is tubular, at length cylindrical with five short lobes,
and is whitish in color. The stamens are ten in number, and
the compound ovary has a single style. The fruit is a rounded
black, edible berry or drupe, with ten seeds.
274
LABI A T&.
275
Topic IX: Dicotyledons with united petals, flower
parts in four whorls.
ORDER TUBIFLOR^:.
437. Lesson XVII. The mint family (labiatae). — The mint
family contains a large number of genera and takes its common
name from the mints, of which there are several species belong-
ing to the genus mentha. In the figure of the " dead-nettle "
Fig. 235.
Whortleberry (Gaylussacia re-
si nosa).
ig. 236.
Spray of dead-nettle (Laminum am-
plexicaule), leaves and flowers.
(Lamium amplexicaule), which is also one of the members of
this family, we see that the lobes of the irregular corolla are
arranged in such a manner as to suggest two lips, an upper and
a lower one. From this character of the corolla, \vhich obtains
in nearly all the members, the family receives its name of
Labiatte. The calyx is iive-lobed. The stamens, four in
number, arise from the tube of the corolla, and converge in
276 PL AN 7* FAMILIES: DICOTYLEDONS.
pairs. The ovary is divided into four lobes, and at the
maturity of the seed these form four nutlets. The leaves are
rounded, crenate on the margins, the lower
ones petioled and heart-shaped, and the upper
ones sessile and clasping around the stem
beneath the flower clusters. From the clasp-
ing character of the upper leaves the plant
derives its specific name of amplexicaule. The
F»g. 237- plant occurs in waste places and is rather
Diagram of lamium
flower, common.
Of the two exercises given below one may be omitted.
Exercise 79.
438. The catnip (Nepeta cataria). — While the "dead nettle" is used
here to illustrate the mint family other species may be studied instead. The
exercise is written for the catnip (Nepeta cataria), a very common weed
occurring from July to September. If fresh material is not at hand when the
study is made, dried entire plants, and the flowers in formalin may be used,
unless it is preferred to use fresh material of some other available species.
In that case the dead nettle here illustrated, and the exercise, will serve as a
guide for the study.
The entire plant.— Note the habit, the character of the branching, the
shape of the stem, the character of the surface. Note the form and arrange -
of the leaves. Is the plant annual, biennial, or perennial ?
The inflorescence. — What is the inflorescence ? The flower ; the parts
present, the calyx, form and relation of parts ; the corolla ; form, relation of
parts ; into what two parts is the corolla divided ? the name of the two parts ?
the number of petals in each part ? Note the stamens, number, size, position
in the flower. The pistil; sketch a pistil showing the nutlets, the long style.
To study the stamens remove a corolla, split it open down one side and
spread it out on a glass slip and mount in water ; or pin it to a aork. Ex-
amine with a good hand lens, or with the lower power of the microscope.
Construct the floral diagram.
Cross pollination by insects. — Study the adaptations of the flower for this
purpose. The lower lip is the landing place, and the upper lip is the " ban-
ner/' If there are color markings on any portion of the flower which serve
to guide the insect in entering the flower, describe them and note the local ion.
With a needle imitate the entrance of an insect into the flower and determine
the way in which cross-pollination takes place.
SCROPHULAKIACE^E. 277
Compare if possible other members of the mint family in the study of cross-
pollination.
Material. — Entire plant with flowers and ripe fruit. If fresh plants are
not at hand, those that have been pressed and dried may be used for the
study of the entire plant and of the leaves. The flowers may be preserved in
formalin.
ORDER PERSONATE.
Exercise SO.
439. The figwort family (scrophulariaceae) — Toad flax (Linaria vul-
garis) — The toad flax is widely distributed, growing in waste places as a
weed from June to October.
The entire plant. — Note the short, pale green perennial root stock ; the
longer erect annual stem ; is it simple or branched ? Leaves, form and ar-
rangement.
The inflorescence. — The kind of inflorescence. The flower. — What parts
of the flower are present? Describe the different parts. The calyx. — How
many sepals indicated? what is the form of the calyx ? The corolla, — Form.
How many petals indicated ? Describe the form of the corolla and its parts.
The stamens. — How many, their position, size? What is the significance of
the difference in the size of the stamens? The pistil. — Form, parts ; form of
the ovary ; how many carpels present in the pistil ?
Study the adaptation of the flower for cross-pollination by the aid of insects ;
the lower lip of the corolla as a landing place ; since insects are supposed to
be attracted by bright colors, what portion of the flower serves thus to direct
the insect ?
Note the spur on the corolla, and the nectar inside ; what kinds of insects
visit this flower ? Imitate with the end of a pencil the entrance of an insect
in a flower and endeavor to make out how cross-pollination takes place.
Seed distribution. — Examine ripe seed pods, dry some of them, and then
take some of the dry ones and place in water. Describe the action of the
pod in scattering the seeds, and the causes.
Other members of the family are interesting to compare with the toad flax,
as the beard tongue (Penstemon pubescens), turtle head (Chelone glabra),
monkey flower (Mimulus ringens), etc.
Material. — Entire plants with the underground stems. Flowers and
fruit. If fresh material cannot be had at the time of the study, dried plants
(pressed) will answer for the study of the entire plant. Flowers may be pre-
served in formalin ; fruits dry.
CHAPTER XLVI.
DICOTYLEDONS (CONCLUDED).
ORDER AGGREGATE.
440. Lesson XX, The composite family (composite). — In
all the composites, the flowers are grouped (aggregated) into
" heads," as in the sunflower, where each head is made up of
a great many flowers crowded closely together on a widened
receptacle. The family is a large one, and is divided into
several sections according to the kinds of flowers and the differ-
ent ways in which they are combined in the head. In the
asters there is one common type illustrated in fig. 238 by the
Aster novce-anglice. In the aster, as is well shown in the
figures, the head is composed of two kinds of flowers, the
tubular flowers and the ray flowers. In the tubular flowers the
corolla is united to form a slender tube, which is five-notched
at the end, representing the five petals. In the ray flowers the
corolla is extended on one side into a strap-shaped expansion.
Together these strap-shaped corollas form the "rays" of the
head. The corolla is split down on one side,wwhich permits
the end then to expand and form the "strap." This is a
ligula, or more correctly speaking a false ligula. In fact the
ray flower is bilabiate. By counting the " teeth " of the false
ligula there are found only three, which indicates that the strap
here is made up of only three parts of the 5-merous corolja.
The two other limbs of the corolla are rudimentary, or sup-
pressed, on the opposite side of the tube. True ligulate flowers
are found in the chicory, dandelion, or in the hieracium, where
the five points are present on the end of the ligula.
278
COMPOSITE.
279
Fig. 238.
Aster novse-angliae.
441. The pappus and syngenecious stamens. — The calyx
tube in the aster, as in all of the composites, is united with the
ovary, while the limb is free.
In the aster, as in many
others, the limb is divided
into slender bristles, the/#/-
pus. (In some of the com-
posites the pappus is in the
form of scales. ) The stamens
are united by their anthers
into a tube (syngenecious)
which closely surrounds the
style. (In ambrosia the an-
thers are sometimes distinct. )
The style in pushing through
brushes out some of the
pollen from the anthers and
bears it aloft as in the bell-
flower, but the stigmatic sur-
face is not yet mature and
Fig. 239.
Head of flowers of Aster novae-angliae.
expanded, so that close pollination cannot take place. There
are usually no stamens in the ray-flowers. The ovary is com-
posed of two carpels, as is shown by the two styles, but there
is only one locule, containing an erect, anatropous, ovule.
28O
PLANT FAMILIES: DICOTYLEDONS.
The floral formula for the composite family then is as follows:
o5, A5, G2.
Fig. 240.
Ray flower of Aster
novae-angliae.
Fig. 241. Fig. 242. Fig. 243.
Tubular flower Tubular flower Syngenecious
of aster. opened to show syn- stamens opened to
genecious stamens. show style and two
stigmas.
442, Other composites. — The rattlesnake-weed (Hieracium
venosum) is an example of another type, with only one kind
of flower in the head, the true ligulate flower. The hawk-
weed, or devil's paint-brush (H. aurantia-
cum) is a related species, which is a
troublesome weed. The dandelion and
prickly lettuce are also members of the
ligulate-flowered composites. A number of
the composites have only tubular flowers, as
in the thorough wort (eupatorium) and ever-
lasting (antennaria).
443. The composites are the most highly developed plants.
— The extent to which the union of the parts of the flower has
been carried in the composites, and the close aggregation of
the flowers in a head, represent the highest stage of evolution
reached by the flowers of the angiosperms.
Fig. 244.
Diagram of composite
flower. (Vines.)
COMPOSITE. 28l
Exercise 81 .
444. The aster (Aster novae-angliae).— (Some other species may be selected
if it is more convenient.) See Exercise 82.
The entire plant. — Describe the entire plant; the character of the stem;
the position of the leaves; their form on different portions of the stem; their
attachment to the stem. Compare the " radicle" leaves with the stem leaves.
The inflorescence. — Describe the inflorescence, and the position of the
flower heads.
A single head of flowers. — Describe the involucre. What different kinds
of flowers are present ? What is the position of each kind on the head ? De-
termine the approximate number of each kind of flowers in a head.
The ligulate flowers. — Remove one from the head and sketch it, showing
the diffetent parts. How many petals are indicated in the strap? How
many petals are in the tubular portion of the ligulate flower? Is this a true
ligula ? Why ? Is the calyx present, and what represents it ? Split open
the corolla tube, and determine whether or not the stamens are present. Is
the pistil present in the ligulate flower ?
The tubular flowers. — Describe the corolla. How many petals are indi-
cated in the corolla tube ? What is such a corolla called ?
The stamens. — Split open the corolla tube down one side, and sketch to
show the position of the stamens, and their relation to each other. Split open
the anther column, spread it out, and sketch to show the relation of the
stamens to ea-:h other, and the pistil within.
Material. — Entire plants in flower ; also some of the mature fruit heads.
Exercise 82.
445. The goldenrod (solidago). — (As an alternate if desired, for Exer-
cise 81.)
If it is desired to study the goldenrod instead of the aster, it will be well
to make a comparison with the aster, and the account of the aster here given
will serve as a guide for the study of the goldenrod. The daisy is also a
good one to compare with the aster, and the outline for the study of the aster
here given will answer for the basis of such a study.
Exercise 83.
446. The dandelion (Taraxacum dens leonis).
The entire plant — Note the very short stem (the plant is sometimes said io
be acaulescent, but it has a short stem). Note the thick root ; the position of
the leaves 'often called radicle leaves because of their position on the short
stem so near the roots) . Sketch a leaf to show its form.
282 PLANT FAMILIES: DICOTYLEDONS.
The inflorescence. — What is the kind of inflorescence? Note the leafless
stem (flowering scape) which bears the head of flowers. Cut across the
stem and split it, and then describe its character.
The involucre. — How many whorls of bracts are there in the involucre?
Comparing plants in flower and at different stages of maturity, describe the
different positions of the involucre.
The flowers. — Are all the flowers strap-shaped ? Note the ligula. Why
is it a true ligula ? Describe and sketch a single flower.
The calyx. — What represents the calyx ? Describe the free portion, or
limb. What is the insertion of the calyx ?
The corolla. — What represents the corolla, and how many petals are in-
dicated ?
The stamens. — What is the relation of the stamens to each other? What
is the name applied to such stamens ? Sketch a few of the stamens to show
their relation to each other.
The pistil. — How many carpels are represented in the pistil ? What is
the indication of this ? What is the relation of the different sets of the flower
to each other, and what is their insertion ? Give the names applied to these
different relations.
The fruit. — Comparing the different stages of the ripening seed, describe
the changes which take place in the different parts of the flower and head.
What parts of the flower are united in the fruit ? What is such a fruit called ?
How many see"ds in the fruit ?
Seed distribution. — How are seeds of the dandelion adapted for seed dis-
tribution ? Take a head of ripe seeds, and blow upon it. Note how the
seeds float; observe which end falls fiwst upon the ground (see chapter on
seed distribution in Ecology).
Cross-pollination. — In some of the composites, as in the daisy, or in the
sunflower, determine what provision is present for cross-pollination. Do all
the flowers ''blossom" at the same time in a single head? Which ones
blossom first ? Do the stamens ripen and emerge from the throat of the
corolla at the same time as the stigma in the same flower? W7hy ? Com-
pare the dandelion in these respects.
Material. — Entire plants, v/ith flowers (they can be obtained all through
the spring); heads of fruit in different stages of maturity.
ECOLOGY.
INTRODUCTION.
447. Life processes in the individual plant. — In studying
the phenomena of plant life which relate to the methods of
absorption and transportation of food to different parts of the
plant, and the internal processes of metabolism concerned in
the building up of new plant material, and the formation of
waste, as well as certain of the growth phenomena and irritable
properties, we have been dealing largely with the individual
plant. A study of these life processes we term physiology.
They relate to the immediate conditions of existence and well
being of the plant.
448. Form in members of the plant body. — Beyond the very
simple plants of the lower groups, and a few reduced forms
among the higher plants, the plant body becomes more or less
bulky or enlarged, and each cell is so situated that it is unable
to participate equally in a number, or all, of the life processes.
The plant body therefore becomes more or less differentiated
into parts, which from the standpoint of physiology are organs
for the performance of distinct functions. This leads us in
the complex plant body to recognize form as an important cor-
relative of function in many cases. The immense variation
which has, through time, taken place in the development of
plants has resulted in a great diversity of form even in the
same members of the plant body. Within certain limits, how-
ever, the form of the plant parts among the individuals of a
species is the same, and they are inherited by, or handed down
to, the offspring.
283
284 ECOLOGY.
449. Form as indicating relationship. — Where the form of
a member is a constant peculiarity of the plants of one kind,
differences in form among other plants indicate that there are
other kinds, or species, of plants. So that aside from the rela-
tion which the members of the plant, as organs, bear to the
immediate life functions, the form of the members becomes the
measure of the value of relationships among kinds. The study of
form in this connection we term morphology.
450. Relation of physiology and morphology. — While physi-
ology and morphology are regarded as distinct subjects, still we
see how they are interrelated when we consider the details of
one or the other subject. It is in the broader concept that the
two subjects are fundamentally different.
451. Form and function in a broader sense than the indi-
vidual.— Just as the individual life processes relate chiefly to
the immediate conditions of existence of the plant, and as the
individualized form of the members relates to the immediate
conditions of relationship; so the life processes in general, on
a grand scale or as affected by seasons, or mutual relations, as
well as form on a grand scale, relate to more extended condi-
tions of existence, and to relationships, the measure of which
is not the form of the plant itself, but the form of the plant
community, showing a relationship of different kinds under like
conditions of existence. In this sense we are concerned with
those processes and forms which are influenced by, or lay hold
on, environment. By the environment is meant all the sur-
rounding objects, conditions, and forces operating in nature,
either temporary, seasonal, or permanent.
452. Mutual and environmental relationships. — While we
are engaged with the study of the life processes concerned
in nutrition and growth of plants, with the details of form, struc-
ture, and systematic relationship, we should not overlook the
mutual relationships which exist among plants in their natural
habitat, and the phenomena of growth recurring with the
seasons, and influenced by environment, or due to inherent
IN TROD UCTION. 285
qualities. By a study of the life histories of plants, their habits
and behavior under different conditions of environment, we
shall broaden our concept of nature and cultivate our aesthetic,
observational, and reasoning faculties. The subject is too
large for full treatment within the limits of a part of an elemen-
tary book. The way here can only be pointed out, and the few
examples and illustrations, it is hoped, will serve to open the
book of nature to the young student, and lead him to study
some of the problems which are presented by every region.
This study of plants, in their mutual and environmental rela-
tionships, is ecology.
453. Some of the factors of environment. — In carrying on
studies of this kind one should bear in mind the factors which
influence plants in these relationships, that is, what are called
the ecologic factors; in other words, those agencies which make
up the environmental conditions of plants, all of which play a
greater or lesser role in the habit or status of the plant con-
cerned, and which, acting on all plants concerned, give the
peculiar color or physiognomy to the plants of a region or of a
more restricted community.
Such factors are climate, with its modifying meteorological
conditions; texture, chemistry, moisture content, covering,
topography, exposure, etc., of the soil; influence of light and
heat; of animals, of plants themselves, and so on.
454. Suggestions for outdoor studies. — For beginning
classes, where only a small part of the time is available, excur-
sions can be made from time to time during the year for this
purpose, taking certain subjects for each excursion. For
example, in the autumn one may study means for the dissemi-
nation of seeds, protection of seeds, plant formations, zonal
distribution of plants, formation of early spring flowers, etc. ;
in the winter, twigs and buds, protection of plants against the
cold; and in the spring, opening of the buds and flowers,
pollination, etc., and further studies on plant societies, relation
of plants to soil, topography, etc.
286 ECOLOG Y.
455. Topics for ecological study, — Some of the topics for
ecological study and observation which can be taken up by
beginning classes are suggested here. The order in which they
may be taken up for study may be dependent to a large extent
on the time of the year at which the study is made, and also
upon the nearness of the school to the supply of material. But
in any place, even in large -cities, there are abundant supplies
of material for several topics, and by foresight preparation can
be made in advance for others.
STUDIES IN PERENNIAL SHOOTS, trie annual growth as determined
by the ring scars, or position of branches.
Trees.
Trees with the main shoot continued through as a central
trunk, as in the pines, spruces, larches, etc.
Trees with a deliquescent trunk, where the main shoot is
lost by continual branching, as in the elm, etc.
External character of the bark of different trees, and the
variation in character of the bark of certain species at
different ages.
Branching of shoots, different types of, in trees, shrubs.
Underground shoots, as in certain ferns like the brake, sensi-
tive fern, where long horizontal shoots are formed, or in
the mandrake, the toothwort, etc.
Creeping shoots or runners, or trailing shoots as in the poly-
pody, the strawberry plant, the clematis, grape vine, club
mosses, and others.
Perennial underground shoots which bear aerial annual
shoots, as in trillium, the mandrake, jack-in-the-pulpit,
blood-root, etc. Many of these shoots also contain stored
'nutriment for the growth of the annual shoot.
STUDIES OF LEAF ARRANGEMENT can be made from the bare
shoots by observing the positions of the leaf scars.
STUDIES OF BUDS AND BUD FORMATION, protection of buds dur-
ing the winter, opening of the buds.
INTRODUCTION-.
STUDIES IN THE RELATION OF PLANTS TO LIGHT.
Direction of shoots with reference to the source of light;
compare shoots which have illumination equally on all
sides with those which are lighted on one side only.
Direction of branches with reference to the source of light ;
compare the branching of a tree which has grown in an
open field with one of the same species which has grown
in the forest (in the forest the lower limbs die away when
they are quite small because the overgrowth of foliage at
the top of the trees shuts out the light); compare also the
branching of trees at the edge of a forest, or at the edge of
a clump of trees where one side is strongly lighted and the
other side is shaded by the adjacent trees.
Leaf position with reference to access of light can be studied
during the season when the shoots are clothed with foliage.
Compare positions of leaves on trees when the foliage is
dense; the leaves are nearly on the periphery of the tree,
or at the ends of the branches. Sometimes even in the
same species, when the foliage is thin at the ends of the
branches, a great development of leaves and young
shoots through the centre of the tree takes place.
Compare position of leaves with reference to position of
sun at different times of day. On some species the
leaves are strongly turned, to face the sun, while on
others the upper leaf surface faces the field of diffused
light. Compare the compass plant (Lactuca scariola).
Compare positions of leaves on prostrate stems, and on the
upright branches of the same.
Compare the lengths of petioles when leaves are clustered
at the base of the shoot, or on a short shoot.
Compare the positions of the flowers on trees and other
plants with varying density of foliage.
STUDIES IN THE RELATION OF PLANTS TO WATER. (Water is
one of the most important factors in influencing plant life.)
During the growing season observe the effect on different
288 ECOLOG Y.
plants in the variation of water-supply; for example in dry
periods when the soil becomes dry, observe how much
more quickly some plants wilt than others on bright days.
Observe the difference in the character of the leaves of
these different plants, and determine what peculiarity of the
leaf in the one case favors the loss of water, while in the
other case water is conserved, or the leaf does not lose
water readily.
With reference to the adaptations of plants to the giving
off of water, or of conserving water, Shimper divides
them into three classes:
1. The Xerophytes; plants which love dry places, or
usually grow in dry places. They possess means
for conserving water, or for checking rapid trans-
piration. ' The plants are either perennial or
annual, and the leaves are not easily wilted. In
some of the plants the leaves are absent, or rudi-
mentary or reduced to spines, as in the cacti.
The larger number of the xerophytes occur in dry
regions.
Xerophytic structures. Some of the xerophytic
structures are thick and succulent stems, or
leaves; leaves with a thick cuticle, with a thick-
ened epidermis; covering for the leaf, or stem, in
the form of hairs or scales: narrow thick leaves;
inrolled edges of leaves; the stomates are often
protected by being sunk in deep cavities.
2. The Hygrophytes; plants which love damp situations,
or grow in damp or wet situations. They possess
means for giving off water, or for ready transpira-
tion; there is a large water content usually in the
tissues. Hygrophytes are perennial or annual.
The leaves are easily wilted.
3. The Tropophytes; the plants usually grow in tem-
perate regions. They possess means for conserv-
IN TROD UC TION. 289
ing water at some seasons and for losing water at
others. The plants are all perennial. The peren-
nial parts are xerophytic, while the annual parts
are hygrophytic. Examples: trees and shrubs
which possess foliage leaves in summer and in the
winter the shoots are devoid of leaves. The plants
are thus enabled to turn from one condition to
another. (The first part of the word tropophyte
means to turn, while the latter part means plant.)
Compare such plants astrillium, jack-in-the-pulpit,
etc., with underground perennial shoots, and aerial
annual shoots.
The pines, spruces, etc., are protected from rapid
transpiration during the winter by having
narrow and thick leaves, and also by some in-
ternal changes in the leaf as winter comes on.
This division of plant forms into classes as xerophytes, hygro-
phytes, and tropophytes is often very marked in wride regions.
The coastal plains and the mountain regions of the tropics are
characterized by hygrophytes; the steppes, deserts, polar
regions, and alpine regions of the temperate zones by xero-
phytes; while the greater part of the North Temperate zone is
characterized by tropophytes.
Between these classes there are intermediate forms which
break down any attempt to draw a hard and fast line between
them; yet such a classification, even if it is arbitrary, is con-
venient. Also the plants of one class may occur in regions
where another class is dominant. For example, the touch-me-
not (impatiens) is a hygrophyte, and it occurs in the region
dominated by the tropophytes. The parsley (portulaca), the
mullein (verbascum) are xerophytes, and they also occur in the
same region; while the heaths, the labrador tea, etc., which
occur in sphagnum moors are also xerophytes, and yet occur
in the region dominated by the tropophytes. (See Chapter
LII.)
ECO LOG Y.
STUDIES IN THE RELATION OF PLANTS TO SOIL.
Observations can be made on the plants occurring on differ-
ent kinds of soil, as sandy, clay, loam, rocky soil, poor or
rich soil, in waste places, uncared parts of fields or gardens,
etc.
One very important condition of the soil is its varying
physical condition of texture, and the presence of
various chemical substances, which influence greatly the
character of the vegetation; but this subject could not
well form one for study by young students, since a
knowledge of the constituents of the soil would be
necessary.
Warming divides plants into four classes:
1. Mesophytes, those plants which occupy a middle posi-
tion with reference to the water-supply.
2. Hydrophytes, those plants which grow in damp or wet
situations.
3. Xerophytes, those plants which grow in dry situa-
tions.
4. Halophytes, those plants which grow in soil or water
which contains an excess of certain salts.
Some soils contain such an abundance of certain salts that only
certain plants grow there. These plants are known as halo-
phytes (salt loving). The salt lands in the great Salt Lake
basin, the alkaline lands of California, Nebraska, and Dakota
may be cited as examples. Certain families of plants, like the
goose-foots, are peculiarly adapted to growing in such soil,
though there are plants from a number of families which are
found in such situations. The great amount of salt in the soil
renders the absorption of water difficult by the plant, so these
plants are provided with means for checking transpiration, or
they would wilt. In this respect the halophytes resemble the
xerophytes, and the structures for checking rapid transpiration
are similar. The plants growing in the salt water are also
halophytes, and those which have parts that are constantly out
IN TROD UC T20N. 29 1
of the water, also possess xerophytic structures for the purpose
of checking transpiration.
STUDIES OF PLANTS IN THEIR RELATION TO ANIMALS.
Studies in cross-pollination by the aid of insects would come
under this head.
STUDIES IN POLLINATION brought about in other ways.
STUDIES OF NUTRITION as shown in parasitic plants, in sym-
biosis, etc. (See Chapter XV. )
STUDIES IN THE RELATION OF LIFE HISTORIES of plants to sea-
sonal changes as suggested in Chapter XXXVIII. Com-
pare in this respect plants which flower at different seasons of
the year.
STUDIES IN THE STRUGGLE BETWEEN PLANTS for the occupation
of the land. (See Chapter XL VIII. )
STUDIES IN SOIL FORMATION by plants. (See Chapter L. )
STUDIES IN ZONAL DISTRIBUTION of plants and in plant com-
munities. (See Chapter XLIX. )
STUDIES IN THE RELATION OF PLANTS TO CLIMATE. (See
Chapter LI I.)
456. Suggestions. — Brief discussions of a few of these topics
are given here to suggest how such studies may be carried on
with young pupils. For a fuller discussion of the topics
enumerated above, the student is referred to the author's larger
" Elementary Botany " and to the works dealing more largely
with the subject of ecology cited in the Appendix. But it
should be borne in mind that the beginning student cannot in
a few excursions make any systematic ecological study, since
some special knowledge of botany would be necessary as a
foundation. Some of the general truths, however, can be
observed.
CHAPTER XLVII.
SEED DISTRIBUTION.
457, Means for dissemination of seeds. — During late summer
or autumn a walk in the woods or a field often convinces us of
the perfection and variety of means with which plants are pro-
vided for the dissemination of
their seeds, especially when we
discover that several hundred
seeds or fruits of different plants --szyg^ K
Fig. 245.
Bur of bidens or bur-marigold, show-
ing barbed seeds.
Fig. 246.
Seed pod of tick-treefoil (desmodium); at
the right some of the hooks greatly magnified.
are stealing a ride at our expense and annoyance. The hooks
and barbs on various seed-pods catch into the hairs of passing
animals and the seeds may thus be transported considerable
distances. Among the plants familiar to us, which have such
contrivances for unlawfully gaining transportation, are the
292
SEED DISTRIBUTION*.
293
beggar-ticks or stick-tights, or sometimes called bur-marigold
(bidens), the tick-treefoil (desmodium), or cockle-bur (xan-
thium), and burdock (arctium).
458, Dissemination by water. — Other plants like some of
the sedges, etc., living on the margins of streams and of
lakes, have seeds which are provided with floats. The wind
or the flowing of the water transports them often to distant
points.
459. Dissemination by animals. — Many plants possess at-
tractive devices, and offer a substantial reward, as a price for
Fig. 247.
Seeds of geum showing the hooklets where the end of the style is kneed.
the distribution of their seeds. Fruits and berries are devoured
by birds and other animals; the seeds within, often passing
unharmed, maybe carried long distances. Starchy and albumi-
nous seeds and grains are also devoured, and while many such
seeds are destroyed, others are not injured, and finally are
lodged in suitable places for growth, often remote from the
original locality. Thus animals willingly or unwillingly become
agents in the dissemination of plants over the earth. Man in
294
ECOLOG Y.
the development of commerce is often responsible for the wide
distribution of harmful as well as beneficial species.
460. Mechanisms for ejecting seeds. — Other plants are more
independent, and mechanisms are employed for violently eject-
ing seeds from the pod or fruit. The unequal tension of the
pods of the common vetch (Vicia sativa) when drying causes
the valves to contract unequally, and on a dry summer day the
valves twist and pull in opposite directions until they suddenly
Fig. 248.
Touch-me-not (Impatiens fulva) ; side and front view of flower below ; above unopened
pod, and opening to scatter the seed.
snap apart, and the seeds are thrown forcibly for some distance.
In the impatiens, or touch-me-not, as it is better known, when
the pods are ripe, often the least touch, or a pinch, or jar, sets
the five valves free, they coil up suddenly, and the small seeds
are whisked for several yards in all directions. During autumn,
on dry days, the pods of the witch hazel contract unequally,
and the valves are suddenly spread apart, when the seeds, as
from a catapult, are hurled away.
Other plants have learned how useful the " wind " may be if
SEED DISTRIBUTION.
295
the seeds are provided with " floats/' " parachutes," or winged
devices which buoy them up as they are whirled along, often
miles away. In
late spring or early
summer the pods
of the willow burst
open, exposing the
seeds, each with a
tuft of white hairs
making a mass of
soft down. As the
delicate hairs dry,
they straighten out
in a loose spread-
ing tuft, which frees
the individual seeds
from the compact
mass. Here they
are caught by cur-
rents of air and
float off singly or
in small clouds.
461. The prickly
lettuce. — In late
summer or early
autumn the seeds
of the prickly let-
tuce (Lactuca sca-
riola) are caught
up from the road-
sides by the winds,
and carried to
fields where they
This plant is shown
Fig. 249.
Lactuca scariola.
are unbidden as well as unwelcome guests.
in fig. 249.
296 ECOLOG y.
462, The wild lettuce. — A related species, the wild lettuce
(Lactuca canadensis) occurs on roadsides and in the borders of
fields, and is about one meter in height. The heads of small
yellow or purple flowers are arranged in a loose or branching
panicle. The flowers are rather inconspicuous, the rays pro-
jecting but little above the apex of the enveloping involucral
bracts, which closely press together, forming a flower-head
more or less flask -shaped.
At the time of flowering the involucral bracts spread some-
what at the apex, and the tips of the flowers are a little more
prominent. As the flowers then wither, the bracts press closely
together again and the head is closed. As the seeds ripen the
bracts die, and in drying bend outward and downward, hugging
the flower stem below, or they fall away. The seeds are thus
exposed. The dark brown achenes stand over the surface of
the receptacle, each one tipped with the long slender beak of
the ovary. The " pappus," which is so abundant in many of
the plants belonging to the composite family, forms here a
pencil-like tuft at the tip of this long beak. As the involucral
bracts dry and curve downward, the pappus also dries, and in
doing so bends downward and stands outward, bristling like the
spokes of a fairy wheel. It is an interesting coincidence that
this takes place simultaneously with the pappus of all the seeds
of a head, so that the ends of the pappus bristles of adjoining
seeds meet, forming a many-sided dome of a delicate and
beautiful texture. This causes the beaks of the achenes to be
crowded apart, and with the leverage thus brought to bear upon
the achenes they are pried off the receptacle. They are thus in
a position to be wafted away by the gentlest zephyr, and they
go sailing away on the wind like a miniature parachute. As
they come slowly to the ground the seed is thus carefully
lowered first, so that it touches the ground in a position for
the end which contains the root of the embryo to come in con-
tact with the soil.
463. The milkweed, or silkweed. — The common milkweed,
SEED DISTRIBUTION. 297
or silkweed (Asclepias cornuti), so abundant in rich grounds,
is attractive not only because of the peculiar pendent flower
Fig. 250.
Milkweed (Asclepias cornuti) ; dissemination of seed.
clusters, but also for the beautiful floats with which it sends its
seeds skyward, during a puff of wind, to finally lodge on the
earth.
464. Means for floating the seeds. — The large boat-shaped,
tapering pods, in late autumn, are packed with oval, flat-
tened, brownish seeds, which overlap each other in rows
like shingles on a roof. These make a pretty picture as
the pod in drying splits along the suture on the convex
side, and exposes them to view. The silky tufts of numerous
long, delicate white hairs on the inner end of each seed, in
298
ECOLOGY.
drying, bristle out, and thus lift the seeds out of their en-
closure, when they are borne, buoyant as vapor, , bearing the
embryo plant, which is to take its place as a contestant in
the battle for existence.
Fig. 251.
Seed distribution of virgin's bower (clematis).
465. The virgin's bower. — The virgin's bower (Clematis
virginiana), too, clambering over fence and shrub, makes a
SEED DISTRIBUTION. 299
show of having transformed its exquisite white flower clusters
into grayish-white puffs, which scatter in the autumn gusts into
hundreds of arrow-headed, spiral plumes. The achenes have
plumose styles, and the spiral form of the plume gives a curious
twist to the falling seed (fig. 251).
CHAPTER XLVIII.
STRUGGLE FOR OCCUPATION OF LAND.
466. Retention of made soil. — In the struggle of plants for
existence, there are a number of species which stand ready to
rush in where new opportunities present themselves by changed
conditions, or by newly made soil. The permanent drainage of
ponds or marshes brings changed conditions, and the flora there
undergoes remarkable transformations. The deposits of the
washings of streams in protected places along the shores, or at
their mouths, where deltas or lateral plateaus are made by the
accumulations of soil scoured off the banks of the stream, or
washed off the fields during rains, make new ground. With
such banks of newly made ground are deposited seeds carried
along with the soil, or dropped there by the wind, by birds, or
other agencies of seed distribution.
467. Vegetation of sand dunes. — Along the sandy beaches
of lakes, or of the ocean, drift piles of the fine sand are formed,
which often are moved onward by the wind. The surface par-
ticles are moved onward to the leeward of the drift, and so on.
The form and location of the sand dune gradually changes.
Such drifts sometimes slowly but surely march along over soil
where a rich vegetation grows, and over valuable land. Even
on these ^and dunes there are certain plants which can gain a
foothold and grow. When a sufficient number obtain a foot-
hold in auch places they retain the sand and prevent the move-
ment of the dune.
468. Reforestation of lands. — When by the action of fire or
wind, or through the agency of man, portions of forests are
300
OCCUPATION OF LAND.
1
302
ECO LOG Y.
partially or completely destroyed, a new set of conditions is
presented over these areas. One of the most important is that
light is admitted where before towering trees permitted but a
limited and characteristic undergrowth to remain. Hundreds
of forms, which for years have been dormant, are now awakened
.from their long sleep, and new and recent importations of seeds,
which are constantly rushing in, spring into existence to fill the
gap, multiply their numbers, and make more sure the perpetua-
tion of their kind.
469. The weaker ones are overcome. — The earliest to appear
are not always the ones to endure the longest, and a battle
Fig. 253-
Abandoned field in Alabama, growing up to broom-sedge and trees. (Photograph by
Prof. P. H. Mell.)
royal takes place during years for supremacy. The weaker
ones are gradually overcome by the more vigorous, and a new
crop of trees, which often springs up in such places, finally
usurps again the domain, in the name of the same or of a
different species.
470. Feral plants in neglected fields. — Domestic plants pro-
OCCUPATION OF LAND.
303
tected by man occupy cultivated fields. When cultivation
ceases, or the crop is removed, or the fields are neglected,
hundreds of species of feral plants, which are constantly spring-
ing up, now nourish, bear seed, and take more or less complete
Fig. 254.
Abandoned field, Alabama, self reforested by pines. (Photograph by Prof. P. H. Mell.)
possession of the soil. Impoverished land, abandoned by man,
becomes nurtured by nature. Weeds, grass, flowers spring up
in great variety often. Some can thrive but little better than
the abandoned crops, while others, peculiarly fitted because of
one or another adapted structure or habit, flourish. Crab-grass
304
ECO LOG Y.
and other low-growing plants often cover and protect the soil
from the direct rays of the sun, and thus conserve moisture.
Fig- 255-
Self-sown white pine in abandoned orchard ; trees 9-20 years old. Near Ithaca. (Photo-
graph by the author.)
The clovers which spring up here and there, by the aid of the
minute organisms in their roots, gather nitrogen. The meli-
lotus, the passion flower, and other deep-rooted plants reach
down to virgin soil and lift up plant food. Each year plant
OCCUPATION OF LAND. 305
remains are added to, and enrich, the soil. In some places
grasses, like the broom-sedge (andropogon), succeed the weeds,
and a turf is formed.
471, Trees follow weeds and grasses, — Seeds of trees in the
mean time find lodgment. During the first few years of their
growth they are protected by the herbaceous annuals or peren-
nials. In time they rise above these. Each year adds to their
height and spread of limb, until eventually forest again stands
where it was removed years before. In the Piedmont section
of the Southern States such a view as is presented in fig. 253
represents how abandoned fields are taken by the broom-sedge,
to be followed later by pines, and later by a forest as shown in
fig. 254.
472, Self-sown white pines. — In New York State many
abandoned hillsides are being reforested slowly by nature with
the white pine. Fig. 255 represents a group of self-sown pines
ranging from three to six meters high (10-20 feet), growing up
in an abandoned orchard near Ithaca. In this reforestation of
impoverished lands, man can give great assistance by timely
and proper planting.
CHAPTER XLIX.
ZONAL DISTRIBUTION OF PLANTS.
473. On the margins of lakes or ponds, where the slope is
gradual from the land into the water, one often has an oppor-
tunity to study the relation
of various plants to different
conditions of soil and water.
In rowing near the south
shore of Lake Cayuga, I have
often been impressed with
the definite areas occupied
by certain plants. Figure
257 is from a photograph,
taken from the boat, of the
shore distribution of these
plants. The most striking
feature here is the grouping
of certain kinds of plants in
definite lines or zones. Here
the limitations of the zones
are quite distinct, so that the
transition from one zone to
another is quite abrupt,
though there is some mixture
of the kinds at the zone of
transition, or tension line.
474. Zonal arrangement.
— This arrangement of plants
under such environmental influences is termed " zonal distribution
of plants. ' ' The slope where this photograph was taken is so
306 .
Fig. 256.
Sagittaria variabilis.
ZONAL DISTRIBUTION OF PLANTS.
307
308
ECOLOG Y.
symmetrical that plants suited by their long habit of growing at
certain depths of water, or in soil of a certain moisture content,
are readily drawn into zones parallel with the shore line.
Fie. 258.
Sagittaria variabilis.
Several zones can be readily made out in this region; two of
them at least do not show in the picture since they are sub-
merged.
475, Submerged zones in the foreground, — If we treat of the
ZONAL DISTRIBUTION OF PLANTS. 309
two submerged zones, the first one is in the rear of the point
from where the photograph was taken, and consists of extensive
areas of chara in four to five meters of water. The second zone
Fig. 259.
Sagittaria heterophylla. Often forms a zone just outside of the Sagittaria variabilis.
then is in the water shown in the foreground of the picture.
The plants here are also submerged, or only a small portion
reaches the surface of the water, and so the zone does not
3 16 ECOLOGY.
show. In this zone occurs the curious Vallesneria spiralis,
with its corkscrew flower stem, and various potamogetons.
476. The visible zones, — In the third zone, or the first one
which shows in the picture, are great masses of the arrow-leaf
(sagittaria) so variable in the form of its leaves. Next is the
fourth zone, made up here chiefly of bullrushes (scirpus), and
occasionally are clumps of the cattail flag (typha). Behind
this is the fifth zone, only to be distinguished at this distance
by the bright flower heads of the boneset (Eupatorium perfolia-
tum) and joepye-weed (Eupatorium purpureum), and the blue
vervain (Verbena hastata), which occurs on the land. Willows
make a compact and distinct sixth zone, while at the right, the
oaks on the hillside beyond form a seventh zone, and still
farther back is a zone of white pines, making the eighth.
CHAPTER L.
SOIL FORMATION IN ROCKY REGIONS AND
IN MOORS.
Lichens.
477. The lichen, parmelia. — Many of the lichens are small
and inconspicuous. They often appear only as bits of color
on tree trunk or rock. One of the conspicuous ones on stones
lying on the ground is the grayish-green thallus of Parmelia
contigua (fig. 260). Its pretty, flattened, forking lobes ra-
diate in all directions, advancing at the margin, and covering
year by year more and more of the stone surface. Numerous
cup-shaped fruit bodies (apothecia) are scattered over the
central area. The thallus clings closely to the rock surface by
numerous holdfasts from the under side, which penetrate minute
crevices of the rock. The lichen derives its food from the air
and water. By its closely fitting habit it retains in contact with
the rock certain acids formed by the plant in growth, or in the
decay of the older parts, which slowly disintegrate the surface
of the rock. These disintegrated particles of the rock, mingled
with the lichen debris, add to the soil in those localities.
478. Lichens are among the pioneers in soil making. — The
habit which many lichens have of flourishing on the bare rocks
fits them to be among the pioneers in the formation of soil in
rocky regions which have recently become bared of ice or snow.
The retreat of glaciers from peaks long scoured by ice, or the
unloading of broken rocks along its melting edge, exposes the
rocks to the weathering action of the different elements. Now
311
312
ECOLOGY.
the lichens lay hold on them and invest them with fantastic
figures of varied color. Disintegrating rock, debris of plants
and animals, join to form the virgin soil. Certain of the blue-
green algae, as well as some of the mosses, are able to gain a
foothold on rocks and assist in this process of soil formation.
Fig. 260.
Rock lichen (Parmelia contigua).
A view of rocks thrown down by the melting and retreating
edge of a glacier in Greenland is shown in fig. 261. These
rocks at the time the photograph was taken had no plant life
on them. At other places in the vicinity of this glacier, rocks
SOIL FORMATION: ROCK DISINTEGRATION. 3!3
longer uncovered by ice \vere being covered by plant life. One
of the Greenland rock lichens is shown in fig. 262.
479. Other plants of rocky regions. — Certain of the higher
plants also find means of attachment to the bare rocks of the
Fig. 261.
Edge of glacier in Greenland, showing freshly deposited rocks. (From Prof. R. S. Tarr.)
arctic and mountain regions. The roots penetrate into narrow
crevices in the rock, and are able to draw on the water which is
elevated by capillarity. Such plants, however, which live on
bare rocks, whether in the arctic or in mountain regions, have
ECO LOG Y.
leaves which enable them to endure long periods of drought.
These plants have either succulent leaves like certain of the
stone-crops (sedum), or small thick leaves which are closely
overlapped as in the Saxifraga oppositifolia.
Few of us, unfortunately, can make the trip to the arctic
regions to study these interesting plants which play such an
Fig. 262.
Rock lichen (umbilicaria) from Greenland.
important role in the economy of nature. Rocky places, how-
ever, or loose stones are common nearer home. Observation
of their flora, and the means by which such plants derive nutri-
ment, store moisture, or protect themselves from drought, will
well repay outdoor excursions.
SOIL FORMATION: ROCK DISINTEGRATION. 31!)
3l6 ECOLOGY.
480. Filling of ponds by plants. — Not only are plants im-
portant agencies in the formation of soil in rocky regions, they
are slowly but surely playing a part in the changes of soil and
in the topography of certain regions. This is very well marked
in the region of small ponds, where the bottom slopes gradually
out to the deeper water in the centre. Striking examples are
sometimes found where the surface of the country is very
broken or hilly with shallow basins intervening. In what are
termed morainic regions, the scene of the activity of ancient
glaciers, or in the mountainous districts, we have opportunities
for studying plant formations, which slowly, to be sure, but
nevertheless certainly, fill in partly or completely these basins,
so that '.the water is confined to narrow limits, or is entirely
replaced by plant remains in various stages of disintegration,
upon which a characteristic flora appears.
481. A plant atoll. — In the morainic regions of central New
York there are some interesting and striking examples of the
effects of plants on the topography of small and shallow basins.
These formations sometimes take the shape of *' atolls," though
plants, and not corals, are the chief agencies in their gradual
evolution. Fig. 263 is from a photograph of one of these plant
atolls about 15 miles from Ithaca, N. Y., along the line of the
E. C. & N. R. R. near a former flag station known as Chicago.
The basin here shown is surrounded by three hills, and is
formed by the union of their bases, thus forming a pond with
no outlet.
482. Topography of the atoll moor. — The entire basin was
once a large pond, which has become nearly filled by the
growth of a vegetation characteristic of such regions. Now
only a small, nearly circular, central pond remains, while
entirely around the edge of the earlier basin is a ditch, in many
places with from ^o-6ocm. of water. There is a broad zone of
land then lying between the central pond and the marginal
ditch. Just inside of the ring formed by the ditch is an elevated
ring extending all around, which is higher than any other part
SOIL FORMATION: ROCK DJSINTEGA'A 7^JON.
of the atoll. On a portion of this ring grow certain grasses and
carices. The soil for some depth shows a wet peat made up of
decaying grasses, carices, and much peat moss (sphagnum).
In some places one element seems to predominate, and in other
cases another element. On some portions of the outer ring are
shrubs one to three meters in height, and occasionally small
trees have gained a foothold.
Next inside of this belt is a broad, level zone, with Carex
filiformis, other carices, grasses, with a few dicotyledons.
Intermingled are various mosses and much sphagnum. The
soil formation underneath contains remains of carices, grasses,
and sphagnum. This intermediate zone is not a homogeneous
one. At certain places are extensive areas in which Carex
filiformis predominates, while in another place another carex,
or grasses predominate.
483. A floating inner *zone. — But the innermost zone, that
which borders on the water, is in a large measure made up of
the leather-leaf shrub, cassandra, and is quite homogeneous.
The dense zone of this shrub gives the elevated appearance to
the atoll immediately around the central pond, and the
cassandra is nearly one meter in height, the " ground " being
but little above the level of the water. As one approaches
this zone, the ground yields, and by swinging up and down,
waves pass over a considerable area. From this we know that
underneath the mat of living and recent vegetation there is
water, or very thin mud, so that a portion of this zone is
" floating."
The inner, or cassandra, zone is more unstable, that is, it is
all '* afloat," though firmly anchored to the intermediate zone.
The roots of the shrubs interlace throughout the zone, firmly
anchoring all parts together, so that the wind cannot break it
up. Between the tu^ts of the cassandra are often numerous
open places, so that the water or thin mud on which the zone
floats reaches the surface, and one must exercise care in walk-
ing to prevent a disagreeable plunge. No resistance is offered
ECOLOG Y.
il
I
I
m
SOIL FORMATION: ROCK DISINTEGRATION. 319
to a pole two or three meters long in thrusting it down these
holes. Grasses, carices, mosses, sphagnum, and occasionally
moor-loving dicotyledons occur, anchored for the most part
about the roots of the cassandra. Standing at the inner margin
of the cassandra zone, one can see the mud, resembling a black
ooze, formed of the titrated plant remains, which have floated
out from the bottom of the older formations. In some places
this lies very near the surface, and then certain aquatic plants
like bidens, and others, find a footing. Upon this black ooze
the formation can continue to encroach upon the central pond.
Agitated by the wind, more and more of the ooze passes out-
ward, so that in time there is a likelihood that the pond will
cease to exist, yielding, as it has in other places, the right of
possession to the contentious vegetation.
484. How was the atoll formed?— In the early formation of
the atoll, it is possible that certain of the water-loving carices
and grasses began to grow some distance (three to four meters)
from the shore, where the water was of a depth suited to their
habit. The stools of these plants gradually came nearer the
surface of the water. As they approach the surface, other
plants, not so strong-rooted, like mosses, sphagnum, etc., find
anchorage, and are also protected to some extent from the
direct rays of sunlight. Partial disintegration of the dead plant
parts and mingling with the soil gradually fill on the inside of
the zone, so that the depth of the water there becomes less.
Now the zone of the carices can be extended inward.
The continued growth of the sphagnum and the dying away
of the lower part of the plant add to the bulk of the plant
remains in the zone, and finally quite a firm ground is formed,
shutting off the shallow water near the shore from the deeper
water of the pond. As time goes on other plants enter and
complicate the formation, and even make new ones, as when
the cassandra takes possession.
The original pond here was rather oblong, and one end possi-
bly much shallower than the other, so that it filled in much
ECOLOGY.
more rapidly, leaving the central pond at the east end. Over
a portion of the west end there is an extensive cassandra forma-
tion, with some ledum (labrador tea), but separated from the
circular cassandra zone by an intermediate zone. In this end-
cassandra formation other shrubs, and white pines five to fifteen
years old, are gaining a foothold, and in a quarter of a century
or more, if left undisturbed, one may expect considerable
changes in the flora of this atoll. It is possible that a rise of
the water for a number of years when the earlier zones were
floating accounts for the circular elevation and atoll forma-
tion, or that the dense shade from forest trees years ago may
have checked the growth of plants in the margin, thus leaving
a marginal depression.
485. A black-spruce moor. — A somewhat similar but more
advanced plant formation occurs east of Freeville, N. Y., and
about nine miles distant from Ithaca. The centre of the basin,
which was perhaps shallower than the former one, has become
completely filled, and all of the central formation is more
elevated than the margin by the shore of the basin. All around
the margin in wet weather the ground is more or less sub-
merged, while all the central portion is so elevated that the
numerous stools or hummocks of grasses like eriophorum, with
its white tufts sparkling in the sunlight like a firmament of
stars, shrubs like cassandra, pyrus, nemopanthes, etc., support
one in walking above the water which rises in the intervening
spaces. Sphagnum, polytrichum, and other mosses grow,
especially in the stools of the other plants, where they now are
shaded by the larger growth, and in drier seasons catch the
water which trickles down during rain.
Years ago the forest encroached on this formation, and trees
of the hemlock-spruce, black spruce, larch, etc., ot consider-
able size gained a footing, first along the margin, then along
the more elevated zone a short distance within. The black
spruce trees spread all over the centre of the formation, attain-
ing a height of one to six or eight meters, while the trees of the
SOIL FORMATION: ROCK DISINTEGRATION. 321
marginal zone
where they first
entered, and the
ground is some-
what more eleva-
ted, attained a
much greater
height.
486. Fall of
the trees on the
marginal zone
when the wind jr
break was re- |"
moved. — T h e s e §
ft
large trees of the |
marginal zone, J
though they were w
rooted to a great Jl
extent in loose °\ -•
soil, nevertheless jf
were protected §
from winds by the <»
forests on the sur- |
rounding hills. g.
When, however, 8*
these hills on three
sides were cleared
for cultivation the
wind had full
sweep, and many
of the large trees
were uprooted by
the force of the
gales. This view
is supported by the
fact that the west-
322
ECOLOG Y.
ern hill is still covered by forest, and large spruce trees of the
marginal zone are still standing, though several were up-rooted
September, 1896, during a fierce southeastern gale, the wind
from this direction having full play upon them.
487. Dying of the spruce of the central area. — This removal
of the forests from the surrounding hills very likely had its
influence in hastening the melting of the winter snows on the
hills, so that excessive quantities of water from this source
FiK. -266.
Dying black spruce in moor. (Photograph by the author.)
rushed quickly down into the swamp, flooding it at certain
seasons much higher than the normal high-water mark during
former times, when the hills were forest-covered. Also during
rains the water would now rush quickly down into the swamp,
flooding it at these times. This greater quantity of water has
had its effect, probably, in causing many of the young spruces
over the centre of the formation to die off,
SOIL FORMATION: ROCK DISINTEGRATION: 323
488. Effect of fire, — This may also have been hastened by
fires which would now more often sweep over the swamp during
dry seasons. In partial evidence of this are many young spruce
trees with scars near the ground where the bark has been
destroyed. This gives admittance to wood-boring insects which
farther aid in the process of weakening and debilitating the
trees. The dying off of the lower limbs of these marsh spruces
suggests the action of fire, as well as excessive moisture at
times. Many of them now present only a small convex top of
living branches. It is interesting to observe the gradation in
this respect in different trees.
489. Weird aspect of dead spruces. — The weird aspect pre-
sented by a clump of these dying young spruce trees is height-
ened also by the changes in the form of the branches as they
die. The living branches have a graceful sigmoid sweep with
their free ends curving upwards as in many conifers. As the
branches die, the free ends curve downward more and more, all
gradations being presented in a single tree. A group of such
dying spruce trees is shown in fig. 266. Some have been long
dead; only the knotted, weather-beaten trunks still remain
tottering to their final condition. Others with leafless, dried,
sprawling branches go swirling with every wind, while a few
struggle on in the presence of these untoward conditions.
490. Other morainic moors. — In other basins, where the
hills on all sides are still forest-clad, more equable temperature
and moisture conditions are conserved. This permits plants to
flourish here which in the exposed basins are disappearing from
the formations or -only leading a miserable existence. This is
strikingly true of some sphagnum formations. In the atoll
formation described the evidence suggests that sphagnum
formerly played a more active part in the evolution of that type
of moor than has been the case since the hills were denuded of
their trees. So also in the spruce moor, sphagnum probably
was at one time a prominent factor in the formation of the early
vegetation. But excessive drought during certain seasons, and
324
ECOLOG Y.
full exposure to the sun and wind, have served to lessen its
influence and importance. But where protected from the
wind, to a large extent from the
heat of the sun, and supplied with
a suitable moisture condition, the
sphagnum flourishes. It grows
either alone in shallow water, en-
croaching more and more on the
centre of the basin, or follows after
and anchors among water-loving
grasses and carices. In some cases
it may thus largely cover such earlier
formations. An examination of the
sphagnum plant shows us how well it
is adapted to flourish under such con-
ditions. The main axis of the plant
bears lateral branches nearly at right
angles, but with a graceful downward
sweep at the extremity. These pri-
mary lateral branches bear secondary
branches, which arise, usually several,
from near the point of attachment
to the main axis. They hang down-
ward, overlap on those below, and
completely cover the main axis or
stem. The leaves of sphagnum are
peculiarly adapted for the purpose of
taking up quantities of water. Not
all the cells of the leaf are green,
but alternate rows of cells become
Fj 2(, broadened, lose their chlorophyll,
TWO fruiting plants of sphagnum, and their protoplasm collapses on the
(From Kerner and Oliver.)
inner faces of the cell walls in such
a way as to form thickened lines, giving a peculiar sculpturing
effect to them, Perforations also take place in the walls. These
SOIL FORMATION: ROCK DISINTEGRATION. 32$
empty cells absorb large quantities of water, and by capillarity
it is lifted on from one cell to another. These pendent branches,
then, which envelop the sphagnum stem, lift water up from the
Fig. 268.
Where isoetes grows. A small morainic basin near Ithaca. (Photograph by the author.)
moist substratum to supply the leaves and growing parts of the
plant which are at the upper extremity.
491. Increase each year, — Year by year the extension of the
sphagnum increases slowly upward by growth of the ends of the
326
ECOLOGY.
individual plants, while the older portions below die off, partly
disintegrate, and pass over into the increasing solidity and bulk
of the peat. It thus happens sometimes that the centres of
Fig. 269.
Cypress knees, Mississippi. (Photograph by H. von Schrenk.)
such basins or moors are more elevated than the margins,
because here a greater amount of water exists in the depths
which is pumped up for use by the plants themselves. Such a
formation is sometimes called a " high moor."
492. Change in form. — Because of the peculiar topographic
features of these basins, together with the conditions of mois-
ture, etc., changes in their form are quite readily observed.
SOIL FORMATION: ROCK DISINTEGRA 7'ION .
But no less important are the influences of plants on soil con-
ditions on the hills, and in more level areas. Old plant parts,
and plant remains, by decay add to the bulk, fertility, and
changing texture and physical condition of the soil.
493. The bald cypress (Taxodium distichum). — Very char-
acteristic are the formations presented by the forests of the bald
cypress of the South, which grows in swampy or marshy places.
The "knees" on the roots of this cypress make grotesque
figures in the cypress forest. These take the form of upright
columnar outgrowths, broader at the base or point of attach-
ment to the horizontal root, and possess a fancied resemblance
to a knee. These knees are said to occur at points on the
horizontal root above and opposite the point where a root
branch extends downward into the soft marsh soil. They thus
give strength to the horizontal root at the point of attachment
of the branch which penetrates into the soft soil, and during
gales they hold these root branches more rigidly in position
than would be the case if the horizontal root could easily bend
at this point. The knees thus are supposed by some to
strengthen the anchor formed by the root in the loose soil.
Their development may be the result of mechanical irritation
at these points on the horizontal root, brought about by the
strain on the roots from the swaying of the tree. Others regard
them as organs for aerating the portions of the root system
which are usually submerged in water or wet soil, and in this
sense the knees are sometimes termed pneumatophores. The
knees catch and hold floating plant remains during floods, and
by the decay of this debris the fertility of the soil is increased.
CHAPTER LI.
PLANT COMMUNITIES: SEASONAL CHANGES.
494. Relations of plants. — One of the interesting subjects
for observation in the study of the habits and haunts of plants
is the relation of plants to each other in communities. In the
topography of the moors, and of the land near and on the
margins of bodies of water, we have seen how the adaptation
of plants to certain moisture conditions of the soil, and to
varying depths of the water, causes those of a like habit in this
respect to be arranged in definite zones. Often there is a pre-
dominating species in a given zone, while again there may be
several occupying the same zone, more or less equally sharing
the occupation. Many times one species is the dominant form,
while several others exist by sufferance.
495. Plants of widely different groups may exist in the
same community. — So it is that plants of widely different rela-
tionships have become adapted to grow under almost identical
environmental conditions. The reed or grass growing in the
water is often accompanied by floating mats of filamentous algae
like spirogyra, zygnema; or other species, as cedogonium, coleo-
chaete, attach themselves to these higher lords of creation; while
desmids find a lodging place on their surface or entangled in
the meshes of the other algae. Chara also is often an accom-
paniment in such plant communities, and water-loving mosses,
liverworts, and fern-like plants as marsilia. Thus the widest
range of plant life, from the simple diatom or monad to the
complex flowering plant, may, by normal habit or adapted
form, live side by side, each able to hold its place in the com-
munity.
328
PLANT COMMUNITIES: SEASONAL CHANCES.
In field or forest, along glade or glen, on mountain slope or
in desert regions, similar relationships of plants in communities
are manifest. The seasons, too, seem to vegetate, blossom,
and fruit, for in the same locality there is a succession of differ-
ent forms, the later ones coming on as the earlier ones dis-
appear.
496. Seasonal succession in plant communities. — The
wooded slopes in springtime teem with trillium, dentaria,
Azalea (Rhododendron nudicaulis).
podophyllum, and other vernal blossoms, while on the steeper
hillsides the early saxifrage is to be found. In the rocky por-
tions of the glen, which is also a favorite lodgment for this
pretty, white saxifrage, the wild columbine loves to linger and
dangle its spurred flowers. The lichen-colored ledge is wreathed
ECOLOGY.
Fig. a?i.
Walking fern, climbing down a hillside.
PLANT COMMUNITIES: SEASONAL CHANGES. 331
with moss and fern. On the partly sunlit slopes the clusters of
azalea are radiant with blossoms, while here and there the shad-
bush, or service-berry (amelanchier), with its mass of white
flower-sprays, overhangs some cliff, and the cockspur thorn
(crataegus) vies with it in the profusion of floral display. Near
by sheets of water pour themselves unceasingly on the rocks
below, scattering spray on the thirsty marchantia. Out from
the steep slopes above rise the graceful sprays of the yew (taxus),
Fig. 272.
Spray of kalmia flowers.
shaded by the towering hemlock spruces. The " walking-fern "
here, holding fast above, climbs downward by long graceful
strides.
497. Change in color with the season. — But the scene shifts,
and while these flowers cast their beauty for the season, others
put on their glory. The flowering dogwood spreads its decep-
332 ECOLOGY.
tive bracts as a halo around the clusters of insignificant flowers.
The laurel (kalmia) with its clusters of fluted pinkish blossoms
is a joy only too brief. Smaller and less pretentious ones
abound, like the whortleberries, amphicarpaea, bush-clover
(lespedeza), sarsaparilla, and so on.
498. Autumn plants.— In the autumn the glen is clothed
with another robe of beauty. With the fall of the <c sere and
yellow leaf," golden-rod and aster still linger long in beauty
Fig. 273.
Spray of witch-hazel (hamamelis) with flowers; section of flower below.
and profusion. When the leaves have fallen the witch-hazel
(hamamelis) begins to flower, and the snows begin to come
before it has finished spreading its curled yellow petals.
499. The landscape a changing panorama. — In our tem-
perate regions the landscape is a changing panorama; forest
and field, clothed with a changing verdure, don and doff their
foliage with a precision that suggests a self-regulating mechan-
ism.
In the glad new spring the mild warmth of the sun stirs the
dormant life to renewed activity. With the warming up of the
soil, root absorption again begins, and myriads of tiny root
hairs pump up watery solutions of nutriment and various salts.
PLANT COMMUNITIES: SEASONAL CHANGES. 333
These are carried to the now swelling buds where formative
processes and growth elongate the shoot and expand the leaf.
Buds long wrapped in winter sleep toss back the protecting
scales. In a multitude of ways the different shrubs and trees
Fig. 274.
Opening buds of hickory.
now discard the winter armature which has served so good a
purpose, and tiny bud leaves show a multitude of variations
from simple bud scale to perfect leaf, a remarkable diversifica-
tion in which the plant from lateral members of the stem forms
334
ECOLOG Y.
organs to serve such a variety of purpose under such diametri-
cally opposed environmental conditions.
500. Refoliation of bare forests in spring, — There is a
Fig. 275.
Austrian pine, showing young growth of branches in early spring.
certain charm watching the refoliation of the bare forests, when
the cool gray and brown tints are slowly succeeded by the light
PLANT COMMUNITIES: SEASONAL CHANGES. 335
yellow-green of the young leaves, which presents to us a warm-
ing glow of color. Then the snow-clad fields change to gray,
and soon are enveloped in a living sea of color. The quiet
hum of myriads of opening buds and flowers in harmony with
the general awakening of nature, and the trickling streamlets
which unite into the gurgling brooks, makes sweet music to
our attentive minds.
501. Contrast of color in evergreens, — The evergreens dis-
play a striking contrast of color. The leafy, fan-shaped
branches of the hemlock-spruce (tsuga) are fringed with the
light green of the new growth. The pines lift up numbers of
cylindrical shoots, with the leaf fascicles for a time sheathed in
the whitened scales, while the shoots are tipped with the brown
or flame-colored female flowers, reminding one of a Christmas
tree lighted with numerous candles. The numerous clusters of
staminate flowers suggest the bundles of toys and gifts, and one
inquires if this beautiful aspect of some pines when putting on
their new growth did not suggest the idea of the Christmas tree
at yule time,
502. The summer tints are more subdued. — As summer time
draws on the new needles of the pine are unsheathed, the light
green tints of the forest are succeeded by darker and subdued
colors, which better protect the living substance from the
intense light and heat of midsummer. The physiological
processes for which the leaf is fitted go on, and formative
materials are evolved in the countless chlorophyll bodies and
transported to growing regions, or stored for future use. In
transpiration the leaf is the terminus of the great water current
started by the roots. Here the nutrient materials, for which
the water serves as a vehicle, are held back, while the surplus
water evaporates into the air in volumes which surprise us when
we know that it is unseen.
503. Autumn colors. — As summer is succeeded by autumn,
a series of automatic processes goes on in the plant which fits
it for its long winter rest again. Long before the frosts appear,
ECOLOGY.
here and there the older leaves of certain shrubs lose more or
less of the green color and take on livelier tints. With the
disintegration of the chlorophyll bodies, other colors, which in
some cases were masked by the green, are uncovered. In other
cases decomposition products result in the formation of new
colors. These coloring substances to some extent absorb the
sun's rays, so that much of the nitrogenous substances in the
leaf may not be destroyed, but may pass slowly back into the
stem and be stored for future use.
504. Fall of the leaf. — The gorgeous display of color, then,
which the leaves of many trees and shrubs put on is one of the
many useful adaptations of plants. While this is going on in
deciduous trees, the petiole of the leaf near its point of attach-
ment to the stem is preparing to cut loose from the latter by
forming what is called a separative layer of tissue. At this
point the cells in a ring around the central vascular bundle
grow rapidly so as to unduly strain the central tissue and
epidermis, making it brittle. In this condition a light puff of
wind whirls them away in eddies to the ground. The frosts of
autumn assist in the separation of the leaf from the stem, but
play no part in the coloration of the leaf.
As the cold weather of autumn and winter draws slowly on,
these trees and shrubs cast off their leaves, and thus get rid of
the extensive transpiration surface, or in some cases the dead
leaves may cling for quite a long period to the trees, However,
in the death and fall of the leaves of these deciduous trees and
shrubs, or the dying back of the aerial shoots of perennial
herbaceous plants, there is a most useful adaptation of the
plant to lay aside, for the cold period, its extensive transpira-
tion surface. For while the soil is too cool for root absorption,
should transpiration go on rapidly, as would happen if the leaf
surface remained in a condition for evaporation, the plants
would lose all their water and dry up.
CHAPTER LII.
ADAPTATION OF PLANTS TO CLIMATE.
505, Some characteristics of desert vegetation. — One of the
important factors in plant form and distribution is that of
clmate, which is modified by varying conditions, as tempera-
ture, humidity of the air, dryness, etc. In desert regions where
the air and soil are very dry, and plants are subject to long
periods of drought, there is a very characteristic vegetation, and
a variety of forms have become adapted to resist the drying
action of the climate.
Some of the plants, especially the larger ones, have very suc-
culent stems or trunks, or they are more or less expanded but
thickened, while the leaves are reduced to mere spines or hairs,
as in the cacti. If plants in desert regions had thin and broadly
expanded leaves, transpiration would be so rapid, and so great,
as to kill them. In these succulent stems there is a propor-
tionately small surface area exposed, so that transpiration is
reduced. The chlorophyll resides here in the stems, and they
function as foliage leaves in many other plants do.
Other plants of the desert, which do not have succulent
stems, are provided with closely appressed and small, thick,
scale-like leaves. The leaves in many of these plants have an
epidermis of several layers of cells, so that transpiration does
not take place so rapidly. In addition to this the stomata are
sunk in pits, or cavities, so that the guard cells are not so
exposed to the drying action of currents of air at the surface.
In still other cases the leaves and stems are covered with a
dense felt of hairs which serves as a cushion to protect them
337
33$ ECOLOGY.
from the direct rays of the sun, and also from the fierce blasts
of dry air which frequently sweep over these regions. The hairs
are so close, and so interwoven, that the air caught in the
interstices is not easily displaced, and the leaves are not then
subject to the drying effects of the passing winds.
506. Some plants of temperate regions possess characters of
desert vegetation. — Even in temperate regions in localities
where the climate is more equable, certain plants, strangely, are
similarly modified, or provided with protecting armor. The
common purslane (portulaca) is an example of a succulent
plant, and we know how well it is able to resist periods of
drought, even when cut free from the soil. With the oncoming
of rains it revives, and starts new growth, while in wet weather
cutting it free from its roots scarcely interferes with its growth.
Similarly the common mullein (Verbascum thapsus), the
leaves and stems of which are so densely covered with stellate
hairs, is able to resist dry periods. One can see how efficient
this panoply of trichomes is by immersing the leaves in water.
It is very difficult to remove the air from the interstices of the
interwoven trichomes so as to wet the epidermis.
507. Alpine plants with desert characteristics. — Alpine
plants (those on high mountains), as well as arctic plants, are
similarly modified, having usually either succulent stems and
leaves, or small, thick and appressed leaves, or leaves covered
with numerous hairs. Cassiope, occurring on mountain sum-
mits of the northeastern United States, and far northward, has
numerous needle-shaped, closely imbricated leaves. The plants
need the protection afforded them by these peculiarities in
these alpine and arctic regions because of the dry air and winds,
as well as because of the bright sunlight in these regions.
Because of the bright sunlight in alpine and arctic regions
many of the plants are noted for the brilliant colors of the
flowers.
508. Low stature of alpine plants a protection against
wind and cold. — Another protection to plants from winds and
ADAPTATION TO CLIMATE.
339
Fig. 276.
Birch trees from Greenland, one third natural size.
340
ECOLQG Y.
' Fig. 277.
Willows from Greenland, one third natural size.
ADAPTATION TO CLIMATE. 34!
from the cold in such regions is their low stature. Many of the
herbaceous plants have very short stems, and the leaves lie close
to the soil, the plants and flowers sometimes half covered with
the snow. The heat absorbed by the soil is thus imparted to
the plant. Trees in such regions (if the elevation or latitude
is not beyond the tree line) have very short and crooked stems,
and sometimes are of great age when only a foot or more high,
and the trunk is quite small. In figure 276 are shown some
birch trees from Greenland, one third natural size, the entire
tree being here shown. Similarly figure 277 represents some
of the arctic willows, one third natural size.
509. Some plants of swamps and moors present characters
of arctic or desert vegetation. — Many of the plants of our
swamps and moors have the characters of arctic or of desert
vegetation, i.e., small, thick leaves, or leaves with a stout
epidermis. The labrador tea (Ledum latifolium), an inhabitant
of cold moors or mountain woods, has thick, stout leaves with
a hard epidermis on the upper side, and the lower side of the
leaves is densely covered with brown, woolly hairs. Transpira-
tion is thus lessened. This is necessitated because of the cold
soil and water of the moor surrounding the roots, which under
these conditions absorb water slowly. Were the leaves broad
with a thin and unprotected epidermis, transpiration would be
in excess of absorption, and the leaves would wither. Cassan-
dra, or leather-leaf, and chiogenes, or creeping snowberry, are
other examples of these shrubs growing in cold moors.
510. Hairs on young leaves protect against cold and wet.
— Hairs on young leaves in winter buds afford protection from
cold and from the wet. The young leaves of the winter buds
of many of our ferns are covered with a dense felt of woolly
hairs. In species of osmunda- this is very striking. The leaves
are quite well formed, though small, during the autumn, and
the sporangia are nearly mature. The hairs are so numerous,
and so closely matted together, that they can be torn off in the
form of a thick woolly cap.
APPENDIX.
COLLECTION AND PRESERVATION OF MATERIAL.
Spirogyra may be collected in pools where the water is
present for a large part of the year, or on the margins of large
bodies of water. To keep fresh, a small quantity should be
placed in a large open vessel with water in a cool place fairly
well lighted. In such places it may be kept several months in
good condition.
Some species of vaucheria occur in places frequented by
oedogonium or spirogyra, while others occur in running water,
or still others on damp ground. Frequently fine specimens of
vaucheria in fruit may be found during the winter growing on
the soil of pots in greenhouses. The jack-in-the-pulpit, also
known as Indian turnip, growing in damp ground I have found
when potted and grown in the conservatory yields an abundance
of the vaucheria, probably the spores of the alga having been
transferred with the soil on the plants. When material cannot
be obtained fresh for study, it may be preserved in advance in
formalin or alcohol.
Wheat rust. — The cluster-cup stage may be collected in
May or June on the leaves of the barberry. Some of the
affected leaves may be dried between drying-papers. Other
specimens should be preserved in 2% formalin or in 70$ alcohol.
If the cluster cup cannot be found on the barberry, other species
may be preserved for study.
The uredospore and teleutospore stages can usually be found
abundantly on wheat and oats, especially on late-sown oats
343
344 APPENDIX.
minute black specks on the surface of the leaf. The leaves
should be preserved dry after drying under pressure.
Liverworts.
Marchantia. — The green thallus (gametophyte) of marchan-
tia may be found at almost any season of the year along shady
banks washed by streams, or on the wet low shaded soil. Plants
with the cups of gemmae are found throughout a large part of
the year. They are sometimes found in greenhouses, especially
where peat soil from marshy places is used in potting. In May
and June male and female plants bear the gametophores and
sexual organs. These can be preserved in *\% formalin or in
70$ alcohol. If one wishes to preserve the material chiefly for
the antheridia and archegonia a small part of the thallus may be
preserved with the gametophores, or the gametophores alone.
In July the sporogonia mature. When these have pushed out
between the curtains underneath the ribs of the gametophore,
they can be preserved for future study by placing a portion of
the thallus bearing the gametophore in a tall vial with 2$ for-
malin. Plants with the sporogonia mature, but not yet pushed
from between the curtains on the under side, can be collected in
a tin box which contains damp paper to keep the plants moist.
Here the sporogonia will emerge, and by examining them day
b'y day, when some of the sporogonia have emerged, these plants
can be quickly transferred to the vials of formalin before the spo-
rogonia have opened and lost their spores. In this condition the
plant can be preserved for several years for study of the gross
character of the sporogonia and the attachment to the gameto-
phyte. From some of the other plants permanent mounts in
glycerine jelly may be made of the spores and elaters.
Biccia. — Riccia occurs on muddy, usually shaded ground.
Some species float on the surface of the water. It may be pre-
served in 2^ formalin or 70$ alcohol.
Cephalozia, ptilidium, bazzania, jungermannia, frullania, and
Other foliose liverworts may be found on decaying logs, on the
COLLECTION AND PRESERVATION OF MATERIAL. 345
trunks of trees, in damp situations. They may be preserved in
formalin or alcohol. Some of the material may also be dried
under pressure.
Mosses are easily found and preserved. Male and female
plants for the study of the sexual organs should be preserved in
formalin or alcohol. In all these studies whenever possible living
material freshly collected should be used.
Ferns.
For the study of the general aspect of the fern plant, polypo-
dium, aspidium, onoclea, or other ferns may be preserved dry
after pressure in drying sheets. A portion of the stem with the
leaves attached should be collected. These may be mounted on
stiff cardboard for use. The sporangia and spores can also be
studied from dried material, but for this purpose the ferns should
be collected before the spores have been scattered, but soon after
the sporangia are mature. But when greenhouses are near it is
usually easy to obtain a few leaves of some fern when the sporangia
are just mature but not yet open. To prevent them from opening
and scattering the spores in the room before the class is ready to
use them, immerse the leaves in water until ready to make the
mounts ; or preserve them in a damp chamber where the air is
saturated with moisture.
For study of the prothallia of ferns, spores should be caught
in paper bags by placing therein portions of leaves bearing ma-
ture sporangia which have not yet opened. They should be
kept in a rather dry but cool place for one or two months.
Then the spores may be sown on well-drained peat soil in pots,
and on bits of crockery strewn over the surface. Keep the pots
in a glass-covered case where the air is moist and the light is
not strong. If possible a gardener in a conservatory should be
consulted, and usually they are very obliging in giving sugges-
tions or even aid in growing the prothallia.
Lycopodium, equisetum, selaginella, isoetes, and other pteri-
dophytes desired may be preserved dry and in 70$ alcohol.
Pines. — The ripe cones should be collected before the seeds
APPENDIX.
scatter, and be preserved dry. Other stages of the development
of the female cones should be preserved either in 70$ alcohol or
in 2\% formalin. The male cones should be collected a short
time before the scattering of the pollen, and be preserved either
in alcohol or formalin.
Angiosperms. — In the study of the angiosperms, if it is de-
sired to use trillium in the living state for the morphology of the
flower before the usual time for the appearance of the flower in
the spring, the root-stocks may be collected in the autumn, and
be kept bedded in soil in a box where the plants will be sub-
jected to conditions of cold, etc. , similar to those under which
the plants exist. The box can then be brought into a warm
room during February or March, a few weeks before the plants
are wanted, when they will appear and blossom. If this is
not possible, the entire plant may be pressed and dried for the
study of the general appearance and for the leaves, while the
flower may be preserved in 2 \% formalin, of course preserving a
considerable quantity. Other material for the study of the plant
families of angiosperms may be preserved dry, and the flowers
in formalin, if they cannot be collected during the season while
the study is going on.
Demonstrations. — Upon some of the more difficult subjects in
any part of the course, especially those requiring sections of the
material, demonstrations may be made by the teacher. The ex-
tent to which this must be carried will depend on the student's
ability to make free-hand sections of the simpler subjects, upon
the time which the student has in which to prepare the material
for study, and the desirability in each case of giving demostra-
tions on the minuter anatomy, the structure of the sexual organs
and other parts, in groups where the material should be killed
and prepared according to some methods of precision, now used
in modern botanical laboratories. The more difficult demonstra-
tions of this kind should be made by the instructor, and such
preparations once made properly can be preserved for future
demonstrations. Some of them may be obtained from persons
who prepare good slides, but in such cases fancy preparations of
COLLECTION AND PRESERVATION OF MATERIAL. 347
curious structures should not be used, but slides illustrating the
essential morphological and developmental features. Directions
for the preparation of material in this way cannot be given, in
this elementary book, for want of space.
Method of taking notes, etc. — In connection with the prac-
tical work the pupil should make careful drawings from the
specimens ; in most cases good outline drawings, to show form,
structure etc., are preferable, but sometimes shading can be
used to good advantage. It is suggested that the upper 2/3 of
a J sheet be used for the drawings, which should be neatly made
and lettered, and the lower part of the page be used for the
brief descriptions, or names of the parts. The fuller notes and
descriptions of the plant, or process, or record of the experi-
ment should be made on another sheet, using one, two, three,
or more sheets where necessary. Notes and drawings should be
made only on one side of the sheet. The note-sheets and the
drawing-sheets for a single study, as a single experiment, should
be given the same number, so that they can be bound together
in the cover in consecutive order. Each experiment may be
thus numbered, and all the experiments on one subject then
can be bound in one cover for inspection by the instructor.
For example, under protoplasm, spirogyra may be No. i, mucor
No. 2, and so on. In connection with the practical work the
book can be used by the student as a reference book ; and dur-
ing study hours the book can be read with the object of arrang-
ing and fixing the subject in the mind, in a logical order.
The instructor should see that each student follows some well-
planned order in the recording of the experiments, taking notes,
and making illustrations. Even though a book be at hand for
the student to refer to, giving more or less general or specific
directions for carrying on the work, it is a good plan for every
teacher to give at the beginning of the period of laboratory
work a short talk on the subject for investigation, giving general
directions. Even then it will be necessary to give each indi-
vidual help in the use of instruments, and in making prepara-
tions for study, until the work has proceeded for some time,
when more general directions usually answer.
APPENDIX.
APPARATUS AND GLASSWARE.
The necessary apparatus should be carefully planned and be
provided for in advance. The microscopes are the most expen-
sive pieces of apparatus, and yet in recent years very good mi-
croscopes may be obtained at reasonable rates, and they are
necessary in any well-regulated laboratory, even in elementary
work.
Microscopes. If the students are provided with microscopes
the number will depend on the number of students in the class,
and also on the number of sections into which the class can be
conveniently divided. In a class of 60 beginning students I have
made two sections, about 30 in each section ; and 2 students work
with one microscope. In this way 1 5 microscopes answer for the
class of 60 students. It is possible, though not so desirable, to
work a larger number of students at one microscope. Some can
be studying the gross characters of the plant, setting up appa-
ratus, making notes and illustrations, etc. , while another is en-
gaged at the microscope with his observations.
The writer does not wish to express a preference for any pat-
tern of microscope. It is desirable, however, to add a little to
the price of a microscope and obtain a convenient working
outfit. For example, a fairly good stand, two objectives (2/3
and 1/6), one or two oculars, a fine adjustment, and a coarse
adjustment by rack and pinion, and finally a revolver, or nose-
piece, for the two objectives, so that both can be kept on the
microscope in readiness for use without the trouble of removing
one and putting on another. Such a microscope, which I have
found to be excellent, is Bausch & Lomb's AAB (which they
recommend for high schools), costing about $25.00 to $28.00.
I have compared it with some-- foreign patterns, and the cost of
these is no less, duty free, for an equivalent outfit. Of course,
one can obtain a microscope for $18.00 to $20.00 without some
of these accessories, but I believe it is better to have fewer
microscopes with these accessories than more without them.
APPARATUS AND GLASSWARE. 349
Of the foreign patterns the Leitz (furnished by Wm. Krafft,
411 W. 59th St., N. Y. ) and the Reichert are good, while Queen
& Co., Philadelphia, Pa., and Bausch & Lomb, Rochester,
N. Y. , furnish good American instruments.
Glass slips, 3X1 inch ; and circle glass covers, thin, 3/4 in.
diameter.
Glass tubing of several different sizes, especially some about
$mm inside diameter and ^mm outside measurement, for root-
pressure experiments.
Rubber tubing to fit the glass tubing, and small copper wire
to tighten the joints.
Watch glasses, the Syracuse pattern (Bausch & Lomb), are
convenient.
U tubes, some about 2omm diameter and io-i$cm long.
Corks to fit.
Small glass pipettes ( ' ' medicine droppers ' ' ) with rubber
bulbs.
Wide-mouth bottles with corks to fit. Reagent bottles. (Small
ordinary bottles about locm X Acm with cork stoppers will an-
swer for the ordinary reagents. The corks can be perforated
and a pipette be kept in place in each ready for use. Such
bottles should not be used for strong acids.)
A few medium glass cylinders with ground top, and glass
plates to cover.
Small vials with corks for keeping the smaller preparations
in.
Small glass beakers or tumblers.
A few crockery jars for water cultures.
Fruit jars for storing quantities of plant material.
Glass graduates; i graduated to looocc, i graduated to
i oocc.
Funnels, small and medium (6 and 16 m in width). Test
tubes. Bell jars, a few tall ones and a few low and broad.
Thistle tubes. Chemical thermometer.
Balance for weighing. A small hand-scale furnished by
3 SO APPENDIX.
Eimer & Amend, 205-211 3d Ave. , N. Y. , is fairly good
($2.00).
Wax tapers or soft-wood splinters.
Glass cylinder, perforated rubber cork for demonstration 27
(see Chapter XVI).
Small porcelain crucibles with covers, and protected wire
triangles to support the porcelain dishes while heafmg.
Apparatus stand, small, several, with clamps for holding test
tubes, U tubes, etc.
Agate trays, very shallow, several centimeters long and wide.
Agate pans, deep, for use as aquaria, etc., with glass to cover.
Mercury, for manometer in demonstration of respiration.
Sheet rubber, or prepared vessels for enclosing pots to pre-
vent evaporation of water from surface during transpiration
experiments.
Litmus paper, blue, kept in a tightly stoppered bottle.
Filter paper for use as absorbent paper. Lens paper (fine
Japanese paper) for use in cleaning lenses; benzine for first
moistening the surface, and as an aid in cleaning.
For materials for culture solution, see Chapter VII.
REAGENTS.
Glycerine, alcohol of commercial (95$) strength, formalin or
formalose of 40^ strength, iodine crystals, eosin crystals,
fuchsin crystals, potassium iodide, potassium hydrate, potash
alum, barium hydrate, caustic potash sticks, vaseline. It is
convenient also to have on hand some ammonia, sulphuric
acid, nitric acid, and muriatic acid in small quantity.
REAGENTS READY FOR USE AND FOR STORING PLANT MATERIAL IN.
Alcohol. Besides the 95$ strength, strengths of 30$, 50$,
and 70$, for killing material and bringing it up to 70^ for
storage.
APPARAJ^US AND GLASSWARE. 35 1
Formalin. Usually about a 2\% is used for storing material,
made by taking 97^ parts water in a graduate and filling in 2^
parts of the 40^ formalin.
Salt solution 5$; sugar solution 15$ (for osmosis).
Iodine solution. Weak — to $oocc distilled water add 2 grams
iodide of potassium; to this add
i gram iodine crystals.
Strong — use less water.
Eosin. Alcoholic solution. Distilled water $occ, alcohol
$occ, eosin crystals ^ gram, potash alum 4 grams.
Aqueous solution. Distilled water IQOCC, eosin
crystals i gram.
STUDENT LIST OF APPARATUS.
One scalpel.
One pair forceps, fine points.
" Two dissecting needles (may be made by thrusting with aid
of pincers a sewing needle in the end of a small soft pine stick).
Lead-pencils, one medium and one hard.
Note paper; a good paper, about octavo size, smooth, un-
ruled, with two perforations on one side for binding. Several
manila covers or folders to contain the paper, perforated also.
Enough covers should be provided so that notes and illustrations
on different subjects can be kept separate.
REFERENCE BOOKS.
The following books are suggested as suitable ones to have
on the reference shelves, largely for the use of the teacher, but
several of them can with profit be consulted by the students
also. There are a number of other useful reference books in
German and French, and also a number of journals, which
might be possessed by the more fortunate institutions, but
which are too expensive for general use, and they are not listed
here.
352 APPENDIX.
Kerner and Oliver, Natural History of Plants. 4 vols., 8vo.
Henry Holt & Co., New York, 1895.
Strasburger, Noll, Schenck and Schimper, A Text Book of
Botany, translated by Porter. The Macmillan Co., New York,
1898.
Vines, Student's Text Book of Botany. The Macmillan Co.,
New York, 1895.
Atkinson, G. F., Elementary Botany (larger edition). Henry
Holt & Co., New York, 1898.
Atkinson, The Biology of Ferns. The Macmillan Co., New
York, 1894.
Britton and Brown, Illustrated Flora of the Northern States
and Canada. Charles Scribner's Sons, New York.
MacDougal, D. T. , Studies in Plant Physiology. Asa Gray
Bulletin, Vol. VII, 1899.
MacDougal, Experimental Plant Physiology. Henry Holt
& Co., New York, 1895.
Spalding, Introduction to Botany. D. C. Heath & Co.,
Boston, 1895.
Bessey, Essentials of Botany. Henry Holt & Co., New
York, 1896.
Goebel, Outlines of Classification and Special Morphology of
Plants. Oxford, Clarendon Press, 1887.
Warming and Potter, Hand Book of Systematic Botany.
Macmillan & Co., New York, 1895.
DeBary, Comparative Morphology and Biology of the Fungi,
Mycetozoa, and Bacteria. Oxford, Clarendon Press, 1887.
Underwood, Our Native Ferns and their Allies. Henry Holt
&Co., New York, 1888.
Bailey, Lessons in Plants. Macmillan & Co., New York,
1898.
Gray, Lessons and Manual of Botany. American Book Co.,
New York.
Mtiller, The Fertilization of Flowers. Macmillan & Co.,
New York.
APPARATUS AND GLASSWARE. 353
Darwin, Insectivorous Plants. D. Appleton & Co., New
York.
Darwin, The Power of Movement in Plants. D. Appleton
& Co., New York.
Darwin, Cross and Self Fertilization in the Vegetable King-
dom. D. Appleton & Co., New York.
Warming, Oekologische Pflanzengeographie. Gebriider Born-
trager, Berlin.
Schimper, Pflanzengeographie. G. Fischer, Jena.
Macmillan, Mimosate Plant Life.
Coulter, Plant Relations. D. Appleton & Co., New York.
Papers by Macmillan in the Bulletin of the Torrey Botanical
Club and Minn. Bot. Studies, by Shaler in the 6th, loth, and
1 2th Annual Reports of the United States Geological Survey,
and by Ganong in Trans. Roy. Soc. Canada, sec. ser. vol. 3,
1897-98, should be consulted by those interested in ecology.
Where materials cannot be readily collected in the region for
class use, they can often be purchased of supply companies.
The Cambridge Botanical Supply Co., Cambridge, Mass.,
supplies plant material of several groups for study, as well as
apparatus and paper.
The Ithaca Botanical Supply Co., Ithaca, N. Y., will supply-
plants for study in various groups, and upon order will prepare
permanent slides for demonstration of the more difficult topics,
such as the structure of the sexual organs of liverworts, mosses,
ferns, etc.
GLOSSARY OF TERMS USED IN THIS BOOK.
Aehene, a dry indehiscent fruit, one-seeded and with the pericarp adherent,
230.
Adherent, term used when one floral set is joined to another, 221, 222.
Ament, a spike which falls away after the maturing of the flower, 227.
Anatropous, said of ovules which are so bent on the stalk that they are in-
verted, 206.
Androecium. the stamens taken collectively, 196.
Antheridium, the male sexual organ, that is, the organ or structure which
bears the sperm cells, 122, 141, 142, 171, 173.
Apocarpous, term used when all of the pistils or carpels in the flower are
separate from each other, 229.
Apogeotropism. a turning away from the earth, said of stems to indicate the
direction of growth with reference to the earth, 108.
Archegonium, the female sexual organ of bryophytes, pteridophytes, and
gymnosperms; it contains the egg, 143, 144, 172, 173.
Aril, a secondary outgrowth of the ovular coat in some seeds, 209.
Bracts, small undeveloped leaves, 219.
Bulb, a short underground stem covered with more or less thickened leaves,
219.
Calyx, the sepals taken collectively, 195.
Gampylotropous, said of an ovule bent at right angles to its stalk, 206.
Capitulum, a flower head, formed by the close association of several flowers
sessile on a shortened axis, 227.
Capsule, a dry fruit with a pericarp which opens at maturity, 230.
Carbohydrate, said of substances containing carbon, hydrogen, and oxygen,
the two latter in the proportions in which they exist in water (H2O), 79.
Carbon dioxide, a compound of carbon and oxygen in the proportion of CO2,
72, 73, 82, 83, 94-101.
Caryopsis, an indehiscent fruit of one seed and a dry, leathery pericarp,
230.
Catkin, see Ament, 227.
Chalaza, that part of the ovule which is attached to the funicle or stalk, 207,
210.
Chlorophyll, the green pigment in the chlorophyll bodies which gives the
green color to leaves, 20, 76, 77.
355
GLOSSARY OF TERMS USED IN THIS BOOK.
Chlorophyll body, the proteid body in protoplasm which contains the pig-
ment chlorophyll, 76, 77.
Chloroplast, said of the chlorophyll-bearing body, 77.
Chromoplast, the proteid body in the protoplasm of carrots, and the petals
of~certain flowers which contains a pigment, 77.
Coherent, said of the members of one floral set when they are united, 221.
Conjugation, a process of fertilization during which the sexual cells become
yoked or united, 115, 118.
Corm, a short thick underground fleshy stem, 219.
Corolla, the petals taken collectively, 195.
Cotyledon, the first leaf, or leaves, on the embryo plant, 211-216.
Cyme, said of flower clusters, where the uppermost flower opens first, a de-
terminate inflorescence, 228.
Cymose, a kind of branching present in cymes, 228.
Diadelphous, two brotherhoods, said of stamens when they are grouped or
joined in two definite clusters, 270.
Diageotropic, said of stems and leaves which grow in a horizontal direction,
109.
Diageotropism, turning sideways, or parallel with the surface of the earth —
term used in reference to stems which grow in a horizontal direction,
108.
Diaheliotropism, term used to denote the direction of growth which stems
take when they grow perpendicular to the direction of light rays, in.
Dichasium, a false dichotomous branching, 228.
Dichotomous. said of an axis where a true forking occurs as the axis branches,
227.
Distinct, said of the members of a floral set when they are separate from
each other, 221.
Drupe, a stone fruit with a fleshy pericarp, 230.
Ecology, a study of organisms in their mutual and environmental relations,
283.
Embryo, the young plant in the seed of gymnosperms and angiosperms, 205,
208, 216.
Embryo-sac, the macrospore in angiosperms, the central cavity in the nucel-
lus of the ovule containing the egg, and other nuclei, in which the em-
bryo and the endosperm are formed, 203, 205, 206.
Endooarp, the inner zone of tissue of the pericarp, 229.
Endosperm, the tissue developed in the embryo-sac from the definitive, or
endosperm, nucleus after fertilization in angiosperms, 208, 215.
Epigynous. said of flowers where any portion of the calyx or corolla is joined
to the ovary, 222, 223, 227.
Exocarp. the outer zone of tissue of the pericarp, 229.
GLOSSARY OF TERMS USED IN This BOOK. 357
Fertilization, the union of two nuclei, one a sperm nucleus and the other an
egg nucleus, 123, 172, 173, 205, 206, 208.
Follicle, a capsule with a single carpel which opens along the ventral or up-
per suture, 230.
Free, said of floral sets where no one set is joined to another set, 221.
Frond, a nearly obsolete term sometimes applied to the leaves of ierns, but
more frequently to the flattened body of certain seaweeds, 217.
Fruit, the mature part of the flower which contains the seed, 228, 230.
Fungi, plants devoid of chlorophyll, possessing mycelium as the structural
unit (except certain unicellular forms), 125-138.
Funicle, the stalk of the ovule, 207-210.
Gamopetalous, said of the corolla when the petals are more or less united,
222.
Gamosepalous, said of the calyx when the sepals are more or less united,
222.
Geotropism, term used to express the property of stems and roots when in-
fluenced by the earth in direction of growth, 108.
Gynandrous, said of stamens when they are united with the pistil, 243.
Gynoecium, the pistils taken collectively, 197.
Head, same as capitulum, 227.
Heliotropism, a turning influenced by light, said of stems, roots, and leaves
when their position is influenced by light, ill.
Hilum, the scar on the seed where it was attached to the wall of the ovary,
207, 2IO.
Hygrophyte, term used to denote plants which grow in damp situations, and
which easily wither when the water supply is checked, 288, 289.
Hypha. a single mycelium thread, 125.
Hypocotyl, the part of the seedling between the cotyledons and the root, 211.
Hypogynous, said of flowers when no floral set is united with the ovary, 222,
223.
Inflorescence, the relation of flowers on an axis or its branches, 225-228.
Insertion, term used in speaking of the position or attachment of the parts
of the flower, 221.
Integument, the coat or coats of the ovule, 208.
Irregular, said of flowers where the different members of one or more sets
are of different size, 222.
Legume, the fruit of the pea, bean, etc., 230.
Leucoplast, the colorless proteid body in protoplasm of chlorophyll-bearing
plants, which under favorable circumstances may become green with
chlorophyll, or become a chromoplast, or may act as a centre for the
formation of starch grains where starch is stored, as in the potato tuber,
etc., 77.
3 5$ GLOSSARY OF TERMS USED IN THIS BOOK.
Ligula, the strap-shaped corolla of the flower of certain composites, 278.
Loculicidal. said of capsules which split down the middle line when ripe, 230.
Lodicule. a reduced member of the perianth in grasses, 247, 248.
Macrosporangium. a sporangium which contains the large spores, macro-
spores, or megaspores, 198, 201.
Macrospores, the large spores which develop only female prothallia, found in
certain pteridophytes, in the gymnosperms, and possibly in the angio'
sperms, 182, 188.
Mesocarp, an intermediate zone of the pericarp, when it is present, 230.
Micropyle, the opening in the free end of the ovule, 209, 210.
Microsomes, term used for the small granules in protoplasm, 25.
Microspores. the small spores in the sporangium in those plants where the
spores are differentiated in size as in certain pteridophytes, in the gym-
nosperms and angiosperms (in the two latter the pollen grains are the
microspores), 182, 201.
Monochasium, a kind of branching where one lateral branch is produced
from each relative or false axis, 228.
Monopodial, said of the branching of shoots when the main shoot grows
more rapidly than the lateral shoots, 227.
Mycelium, the vegetative part of most fungi, 25, 84-89, 125, 131, 134.
Nucellus, the central part of the ovule, 208, 210, 212.
Nucleus, a special organ in protoplasm, of a more dense structure than the
remainder of the protoplasm, 21.
Nut, an indehiscent fruit with a dry hard pericarp, 230.
Oogonium, the female sexual organ of certain low algse, as vaucheria, and
of certain fungi ; contains the egg, 122, 123.
Orthotropous, a straight ovule, 206.
Ovule, the macrosporangium of the gymnosperms and angiosperms, 191; oc-
curs usually within or upon the carpel, and at maturity contains the
embryo, if that is formed, 191, 198, 201, 205, 206, 207, 210.
Panicle, a raceme with the lateral axes branched, 227.
Pericarp, the part of the fruit which envelops the seed and which forms the
wall of the seed, 229, 230.
Perigynous, said of flowers where the stamens or petals are borne on the
calyx, 222, 223, 265, 266.
Perisperm, the remnant of the nucellus within the seed, when it is not en-
tirely consumed in the formation of the seed, 208, 210, 212.
Perithecium, the closed or nearly closed fruit body of certain ascomycetous
fungi, 136-138.
Phyllotaxy, term used to denote arrangement of leaves on the axis, 1 1.
Pistil, the member of the flower which contains the ovules, 197, 198, 203,
206.
GLOSSARY OF TERMS USED IX THIS BOOK. 359
Pleiochasium, an inflorescence where each relative or false axis produces
more than two branches, 228.
Pneumatophore, term applied to special organs of aeration, 327.
Pollination, the passage of the pollen from the stamens to the stigma of the
pistil, 192, 205, 241, etc.
Pome, the fruit of the apple, 230.
Poricidal, said of capsules which dehisce by a terminal pore, 230.
Progeotropism, a txirning toward the earth, said of roots which grow toward
the earth, 108.
Prothallium, the sexual stage of the pteridophy tes, gymnosperms, and angio-
sperms, 166, 170, 203-207.
Protonema, thread-like growth proceeding from the germinating spore of
bryophytes, and some pteridophy tes, 169.
Protoplasm, the living substance of plants and animals, 15—27.
Pyxidium, pyxis, a capsule which opens with a lid, 230.
Raphe, the part of the stalk of the ovule which is joined to the ovule where
the ovule is bent upon its stalk, 207, 210.
Respiration, an interchange of gases by the plant during growth, by which
oxygen is consumed and carbon dioxide is liberated, 94-101.
Rhizome, an underground root-stock, 200.
Runners, prostrate stems which take root here and there, 219.
Samara, a winged seed, 256.
Schizocarp. a dry several- loculed fruit in which the carpels separate from
each other at maturity but do not dehisce, 230.
Septicidal, applied to a syncarpous capsule in which the carpels separate
along the line of their union, 230.
Silique, a capsule of two carpels which separate at maturity, leaving the par-
tition wall persistent, 230.
Spadiz, a spike in which the main axis is fleshy, 227.
Sperma'.ozoid, a motile sperm cell, 122, 123, 142, 171, 172.
Sperm cell, the male cell which contains the nucleus for union with the egg
nucleus; it may be motile or non-motile, 204, 205.
Spike, an inflorescence with a long main axis, and with sessile flowers on it
or on very short lateral axes, 227.
Spikelet, a short lateral flower-branch in the grasses, 247, 249.
Sporangium, a spore case containing spores.
Sporogonium, the entire structure which is the product of the fertilized egg
in the bryophytes, 144, 145, 152.
Sporophyll, term applied to leaves in the pteridophytes, gymnosperms, and
angiosperms which bear sporangia, 176, 188, 197.
Stamens, the members of the flower which bear the pollen grains or micro-
spores, 201, 203, 206.
360 GLOSSARY OF TERMS USED IN THIS BOOK.
Sympodial, said of types of branching where the lateral axes grow more rap-
idly than the main axis, 227.
Syncarpous, said of the gynoecium when the carpels are united, 229, 230.
Testa, the outer coat of the seed, 208, 210.
Thallophytes, plants of low organization in which the plant body is a frond
or thallus, especially the algae and fungi, 217.
Tropophytes, plants, especially of the North Temperate Zone, which have
hygrophytic structures during the summer season, and during the win-
ter season change to xerophytic habit, 288, 289.
Tubers, underground thickened stems. 219.
Umbel, said of an inflorescence where the main axis is shortened and the
terminal flowers appear to form terminal clusters, 227.
Xerophytes, plants adapted to grow in dry situations, or in situations where
they absorb water with difficulty, 288, 289.
Xylem, the woody elements of the fibrovascular bundle, 64-68.
Zygospore, zygote, a resting spore, formed by the sexual union of two equal
or nearly equal cells, 117, 118.
INDEX.
Absorption. 28-33, 39-41
Acer, 262
Aceracese (a-cer-a'ce-ae), 262
Achene, 230
Acorus (a'co-rus), 243
Adder-tongue, 233, 236, 238
Adherent, 221, 222
Adiantum, 160
yEsculinese (ses-cu-lin'se), 262
^sculus (aes'cu-lus), 264
Agaricus t canapestris (a-gar'i-cus
cam-pes'tris), 85-87
Aggregate (ag-gre-ga'tse), 278
Almond family, 266
Ament, 227
Amentiferse (a-men-tifer-se), 250-
254
Amygdalacese (a-myg-da-la'ce-oe),
266
Anatropous, 206
Androecium (an-droe'ci-um), 196
Angiosperms, 194-206, 235
Antheridium (an-ther-id'i-um), 122,
141, 142, 171, 173
Apocarpous (ap-o-car'pous), 229
Apogeotropism (ap-o-ge-ot'ro-pism),
108
Apple, 269
Apple family, 267
Aracese (a-ra'ce-se), 243
Archegonium (ar-che-go'ni-um),
143, 144, 172, 173
Aril, 209
Arisaema (ar-i-sse'ma), 243-246
Arum family, 243
Asclepias (as-clep'i-as), 297
Ash, 82
Aspidium (as-pid'i-um), 155-164
Aster, 278-280
Atoll moor, 315-320
Atoll, plant, 315-320
Azalea (a-za'le-a), 329
Bacteria, nutrition of, 91
Bald cypress, 327
Berry, 230
Bicornes (bi-cor'nes), 274
Bidens (bi'dens), 292
Black mould, 24-26, 125-127
Black rust, 129-131
Blue violet, -260
Bluet, 223
Bracts, 219
Branching (dichotomous, monopo-
dial, sympodial, cymose), 227
Buckeye family, 264
Buds, 7-13
Bulbs. 219
Buttercup, 257, 258
Bur-marigold, 292
Calla, 245
Caltha, 256, 257
Calyx, 195
Campy lotropous, 206
Capitulum, 227
Capsella, 259
Capsule, 230
Carbohydrates, 79
Carbon dioxid, 72, 82, 83, 94,
101
| Carbon food of plants, 70-80
Carnation rust, 87-89
Carnivorous plants, 89-91
{ Caryopsis (ca-ry-op'sis), 230
i Castor oil bean, 212
Catkin, 227
Catnip. 275
Cat tails, 243
Cell sap, 21, 31
36l
362
INDEX.
Chalaza (cha-la'zaN, 207, 210
Chlorophyll, 20, 76, 77
Chlorophyll bodies, 76, 77
Chloroplast (chlo'ro-plast), 77
Choke cherry, 266, 267
Christmas fern, 155-164
Chromoplast, 77
Cistiflorse (cis-ti-flo'rae), 260
Class, 233, 235
Classification, 231—235
Claytonia, 226
Clematis, 298
Cluster cup, 129, 130
Coherent, 221, 222
Compositse, 278
Composite family, 278
Conjugation, 115-118
Convolvulus (con-vol'vu-lus). 221
Corms, 219
Corolla, 195
Cotyledon (cot-y-le'don), 211-216
Crow-foot family, 256-258
Cruciferae (Cru-cif er-se), 259
Cupuliferse (cu-pu-lifer-se), 252
Cyme (forking, helicoid, scorpioid),
228
Cypress knees, 326
Cypripedium (cyp-ri-pe'di-um), 240-
242
Dandelion, 281
Dehiscence, 230
Dentaria (den-ta'ri-a), 199-202
Desmodium, 292
Diadelphous (di-a-del'phous), 270
Diageotropism (di-a-ge-ot'ro-pism),
108, diageotropic, 109
Diagram (floral), 224
Diaheliotropism (di-a-he-li-ot'ro-
pism), in
Dichasium (di-cha'si-um), 228
Dicotyledones (di-cot-y-led'o-nes),
234, 235, 250-282
Diffusion, 28-33
Dioncea (di-o nce'a), 89, 91
Distinct, 221
Dodder, nutrition of, 88, 90
Drosera (dros'e-ra), 89, 91
Drupe, 230
Duckweeds, 243
Ecology (e-col'o-gy), 283-340
Elm family, 255
Embryo, 205, 208, 216
Embryo sac, 203, 205, 206
Endocarp, 229
Endosperm, 208-215
Epigynous, 222, 223, 267
Epipactis (ep-i-pac'tis), 240
Equisetinse, 174
Equisetum, 174-179
Erythronium (er-y-thro'ni um), 232,
233, 236, 238
Evening primrose, 271, 272
Exocarp, 229
Family, 233-235
Ferns, 155-173
Fertilization, vaucheria, 123 ; ferns,
172, 173; angiosperms, 205, 206,
208
Fibro-vascular bundles, 62-68
Figwort family, 277
Filicinese (fil-i-cin'e-ae), 155
Follicle, 230
Forget-me-not, 229
Formula (floral), 223
Fragaria (fra-ga'ri-a), 266
Free, 221
Frond, 217
Fruit, 228, 230
Fungi, 125-138
Funicle, 207-210
Gamopetalous (gam-o-pet'a-lous),
222
Gamosepalous (gam-o-sep'a-lous),
222
Garden bean, 211
Gaylussacia (gay-lus-sa'ci-a), 274,
275
Genus, 232
Geotropism (ge-ot'ro-pism), 108
Geum (ge'um), 293
Glumiflorse (glu-mi-flo'ne), 247
Graminese (gram-in'e-se), 247
Grass family, 247
Green felt, 120-124
Group, 235
Growth, 102-106
Gymnosperms (gym'no-sperms),
184-193
Gynandrse (gy-nan'drae), 240
Gynandrous (gy-nan'drous), 240
Gynoecium (gyn-ce'ci-um), 197
INDEX.
5C3
Hamamelis (ham-a-me'lis), 332
Hawkweed, 280
Head, 227
Heliotropism (he-li-ot'ro-pism), ill
Hickory, opening buds, 333
Hieracium (hi-er-a'ci-um), 280
Hilum, 207, 210
Hippocastanaceae (hip-po-cas-tan-a'-
ce-ae), 264
Hjrse chestnut, 264
Horsetails, 174-179
Houstonia, 223
Huckleberry (whortleberry), 274, 275
Hygrophytes (hy'gro-phytes), 288,
289
Hypha, 125
Hypocotyl (hy-po-cot'yl), 211
Hypogynous,' 222, 223
Impatiens, 294
Indian turnip, 243-246
Inflorescence, 225-228
Insectivorus plants, 89, 91
Insertion, 221
Integument, 206, 208
Irregular, 222
Irritability (movement due to), 107-
"3
Isoetes (i so'e-tes). 180-183, 325
Jack-in-the-pulpit, 213, 243-246
Kalmia (kal'mi-a), 331
Kinship, 225
Labiatse (la-bi-a'tae), 275
Lactuca (lac-tu'ca), 295, 296
Lady slipper, 240-242
Lamium, 224, 275
Leaf, 219 ; structure of, 56-59
Legume, 230
Leguminosae (leg-u-min-o'sae), 269
Leucoplast (leu'co-plast), 77
Lichen, 311, 313
Ligule, 278
Liliaceae (lil-i-a'ce-ae), 234, 240
Liliiflorae (lil-i-i-flo'rae), 236
Lilium, 233
Liverworts, 139-148
Ix)culicidal, 230
Lodicule, 247, 248
Macrosporangia, macrosporangium
(mac-ro-spor-an gium), 198, 201
Macrospores (mac'ro-spores), isoetes,
182; pine, 188
Marchantia (mar-chan'ti-a), 139-148
Marsh marigold, 256, 257
Mentha (men'tha), 275
Mesocarp, 230
Micropyle (mi'cro-pyle), 209, 210
Microsomes (mi'cro-somes), 25
Microspores (mi'cro-spores), isoetes,
182; pine, 188; trillium, 197
Mildew (willow), 134-138
Milkweed, 296, 297
Mint family, 275
Mnium (mni'um), 150-154
Monochasium (mon-o-cha'si-um), 228
Monocoty ledones ( mon-o - cot-y - led 'o-
nes), 213, 216, 234, 235, 236-249
Morning glory, 221
Mosses, 149-154
Mucor, 24-26, 125-127
Mushroom, 85-87
Mustard family, 259
Mycelium (my-ce'li-um), 25, 84-89,
125, 131, 134
Myrtiflorse (myr-ti-flo'rae), 271
Nepeta (nep'e ta), 276
Nettle (dead), 224, 275
Nitrogen (how obtained by clovers,
etc.), 92> 93
Nucellus, 208, 210, 212
Nucleus, 21
Nut, 230
Nutrition, 84-93
Oak family, 252
CEnothera (oe-no'the-ra), 271, 272
Onoclea (on-o-cle'a), 159
Onograceae (on-o-gra'ce-ae), 271
Oogonium(o-o-go'ni-um), 122, 123
Orchidaceae (or-chid-a'ce-ae), 240-
242
Order, 233-235
Orthotropous (or-thot'ro-pous), 206
Osmose, 30-32
Osmotic pressure, 50, 51
Ovule, 191, 198, 201, 205-207, 210
Oxygen, 71-73, 82, 83, 94-101
Palm (cocoanut), 243
Panicle, 227
3^4
INDEX.
Papilionacece (pa-pil-i-o-na'ce-a;),
269
Parasitic fungi (nutrition of). 87, 88
Parmelia (par-me'li-a), 31.1, 312
Pea, 270
Pea family, 269
Peltandra (pel-tari'dra), 205
Pericarp, 229, 230
Perigynous, 222, 223, 265, 266
Perisperm, 208, 210, 212
Perithecium (per-i-the'ci-um), 136-
138
Personatae (per-so-na'tae), 277
Petaloideae (pet-a-loi'de-ae), 236
Phyllotaxy, n
Pistil, 197, 198, 203, 206
Pisum (pi'sum), 270
Plant substance, 81, 83
Pleiochasium (plei-o-cha'si-um),
Plum family, 266
Pollination, 192, 193, 205, 241
Polycarpicae (pol-y-car'pi-cae), 256
Polypodium (pol-y-po'di-um), 155
Polytrichum, 149
Pomacese, 267
Pome, 230
Pneumatophore (pneu-mat'o-phore),
327
Poricidal, 230
Prickly lettuce, 295
Primrose, 224
Progeotropism (pro-ge-ot!ro-pism),
108
Prothallium (pro-thall'i-um), 203-207 ;
ferns, 166-170
Protonema (pro-to ne ma), 169
Protoplasm (pro'to-plasm), 15-27;
movement of, 26
Prunus, 267
Pteris (pter'is), 170
Puccinia (puc-cin i-a), 129, 130
Purple trillium, 231, 232
Pyrus, 269
Pyxidium, pyxis, 230
Quercus (quer'cus), 252
Quillwort, 180-183
Raceme, 227
Ranunculacese (ra-nun-cu-la'ce-ae),
256-258
Raphe, 207, 210
Raspberry, 206
Rattlesnake-weed, 280
Red rust, 129-132
Reforestation, 300-304
Relationships, 225, 232
Respiration, 94-101
Rhizome, 200
Rhizopus (rhi zo-pus), 126-128
Rhododendron (rho-do-den'dron),
329
Rhoeadinae (rhoe-a din'ae), 259
Root, 220
Root hairs, 15-18, 39-44
Root pressure, 50, 51
Root-stock, 219
Rosaceae (ro-sa'ce-ae), 265
Rose family, 265
Rosiflorae (ro-si-flo'rae), 265 i :
Rubus, 266
Runners, 219
Sagittaria, 306, 309
Salicaceae (sal-i-ca'ce-ae), 250
Salix, 251
Samara, 256
Sand dunes, 300, 301
Schizocarp, 230
Schrophulariaceae (schroph-u-la-ri-a'-
ce-se), 277
Sea-wrack, 217
Seed, 208, 210
Seed distribution, 292
Seed (germination), 1-6
vSeedlings, 210, 216
Septicidal, 230
Sexual organs ; vaucheria, 122—124 \
ferns, 170-173; angiosperms, 205-
207
Shepherd's purse, 259
Silique, 230
Silkweed, 296, 297
Skunk's cabbage, 243
Solomon's seal, 237
Spadiciflorae (spa-di-ci-flo'ras), 243
Spadix, 227
Spathyema (spath-y-e'ma), 243
Species, 231
Spermatozoids (sper-mat'o-zoids),
122, 123, 142, 171, 172
Sperm cell, 204, 205
Sphagnam, 324
Spike, 227
Spikelet, 247-249
Spines, 219
INDEX.
365
Spiraea (spi-rae'a), 265
Spirogyra, 19-23, 115-119
Sporangium (spor-an'gi-um), mucor,
126; fern, 158-163; equisetum,
176; isoetes, 181; pine, 188, 191
Sporogonium (spor-o-go'ni-um), 144,
145, 152
Sporophyll, equisetum, 176 ; pine,
188; trillium, 197
Spring beauty, 226
Spruce moor, 320-324
Stamens, 201, 203, 206
Starch, 70-80
Stem, 219
Stomates, 58, 59
Strawberry, 265, 268
Sundew, 90, 91
Sweet flag, 243
Sympetalae (sym-pet'a-lae), 274
Syncarpous (syn-car'pous), 229, 230
Taraxacum (tar-ax'a-cum), 281
Taxodium (tax-o'di-um), 327
Taxonomy (tax on'o-my), 231-235
Taxus, 209
Tendrils, 219
Testa, 208, 210
Thallophytes, 217
Thallus, 217
Thorns, 219
Tissues (syopsis of), 68
Tissue tension, 46-48
Toad flax, 277
Touch-me-not, 294
Transpiration, 51-54, 56-59
Trillium, 194
Trillium erectum, 231, 232
Tropophytes (trop'o-phytes), 288,
289
Tubers, 219
Tubiflorae (tu-bi-flo'rae), 275
Turgescence, 28-30, 45-49
Turgidity, 45-49
Turgor, 28-30, 45-49
Ulmaceae (ul-ma'ce-aa), 255
Ulmus, 255
Ulva, 217
Umbel, 227
Uncinula (un-cin'u la), 134-138
Unifolium (u-ni-fo'li-um), 237
Uromyces (u-ro-my'ces), 87, 88
Urticiflorae (ur-ti-ci-flo'rae), 255
Vacciniaceee (vac-cin-i-a'ce-?e), 274
Vaucheria (vau cher'i-a), 120-124
Venus fly-trap, 89, 91
Viola, 260
Violaceae (vi-o-la'ce-ae), 260
Violet family, 260
Virgin's bower, 298
Wake robin, 232
Walking fern, 331
Wheat rust, 129-133
White pine, 184-193
\Vhortleberry, 274
Wild lettuce, 296
Willow family, 250
Witch hazel, 332
Xerophytes (xer'o-phytes), 288, 289
Yew, 209
Zonal distribution, 306
Zygospore, zygote, 117, 118
UNIVERSITY OF TORONTO
LIBRARY
Pocket.
Acme Library Card Pocket
Under Pat. "Ref. Index File."
Made by LIBRARY BUREAU, Bo'aton
o
d-
o> 3
CO CO
o o
» 3
09) <•
P CD
0-5
Q (to
CD
•o
Live Music Archive
Librivox Free Audio
Metropolitan Museum
Cleveland Museum of Art
Internet Arcade
Console Living Room
Books to Borrow
Open Library
TV News
Understanding 9/11