ABORATORY AND
ELD EXERCISES

DENSMORE

QK53

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LABORATORY AND FIELD
EXERCISES

FOR "GENERAL BOTANY"

BY

HIRAM D. DENSMORE

I'KOFESSOK OF BOTANY AT BELOIT COLLEGE

GINN AND COMPANY

?W YORK • CHICA
LAS • COLUMBUS

51167

BOSTON • NEW YORK • CHICAGO • LONDON
ATLANTA • DALLAS • COLUMBUS • SAN FRANCISCO

COPYRIGHT, 1920, BY
HIRAM D. DENSMORE

ALL RIGHTS RESERVED
320.6

<Cbt atftenatum &rte*

GINN AND COMPANY • PRO-
PRIETORS • BOSTON • U.S.A.

PREFACE

These laboratory and field exercises have been written to
accompany the author's textbook in general botany, and the
topics for the practical exercises are therefore arranged in the
same order as in the text.

;* Both the textbook and the exercises have been used with

^ several generations of students and instructors, whose criticisms

and suggestion's are embodied in this revision of the field and

laboratory exercises for publication. The topics in the practical

exercises also follow those of the text and are divided into

^ three more or less distinct parts.

Part I contains directions for some field work, laboratory
work, and experiments on the general form, structure, and
physiology of the higher green plants.

Part II is devoted to practical laboratory exercises relating

* to the general morphology and relationship of the great plant
K groups, from the algse and fungi to the highest seed plants.

^ The laboratory exercises on anatomy in Part II are designed to

• enable teachers not familiar with the methods of the new anat-
omy to direct students in the study of plant structure from the
more modern standpoint. It is hoped that the diagrams and
discussions of the text on anatomy will materially assist both
teachers and students in making the exercises clear.

Part III contains directions for field work on trees, shrubs,
and herbaceous plants, considered from a general ecological
standpoint. A brief study of plant associations has been added,
in order to introduce the student to the study of plants in their
social relations. Emphasis is also laid, in the exercises as in

iii

iv .LABORATORY AND FIELD EXERCISES

the textbook, on the study of plants as living organisms, closely
related and adapted to the environment at all seasons of the
year. The few species selected for field study are taken from
families represented in the spring flora which are of special
biological or economic interest. No attempt has been made to
outline practical studies for all important families of the spring
flora, since only a limited number of species could be studied
in an introductory course in college botany.

Although these exercises have been written to accompany
the author's textbook, they can easily be adapted for use with
any text, or to accompany lectures in an introductory course
in botany or plant biology.

CONTENTS

PART I. BIOLOGY OF THE HIGHER SEED PLANTS
SECTION I. PLANTS AND THE ENVIRONMENT

PAGE

A. THE BODY PLAN AXD FORM OF PLANTS 3

The Lilac 3

Herbaceous Plants 6

Trees (Spruces and Pines) 9

Trees (the American Elm) 13

B. ADJUSTMENT TO THE ENVIRONMENT 18

The Embryo and Seedling of the Bean 18

Experiments 20

Supplementary Studies 21

SECTION II. CELL STRUCTURE AND GROWTH

A. THE CELLULAR STRUCTURE OF PLANTS .22

Cell-Wall Thickening and Cell Differentiation 24

Protoplasm, Vacuoles, and Nuclei in Root-Tip Cells ... 26
Cell Structure and Protoplasmic Streaming in Stamen Hairs

of Tradexcantia t .27

Plastids in Plant Cells 30

B. CELL STRUCTURE AND GROWTH 31

Growth 31

C. THE CELL AND CELL DIVISION 35

Supplementary Studies 39

vi LABORATORY AND FIELD EXERCISES

SECTION III. ANATOMY

PAGE

A. ANATOMY OF STEMS 41

External Features of Woody Stems 41

Gross Structure of Mature Stems 42

Microscopic Structure of Woody Stems 45

Herbaceous Stems (Dicotyledons) 50

Herbaceous Stems (Monocotyledons) 52

B. STRUCTURE OF ROOTS 53

C. THE STRUCTURE OF THE LEAF 53

SECTION IV. PHYSIOLOGY OF PLANTS

A. PHOTOSYNTHESIS 57

B. RESPIRATION 60

C. TRANSPIRATION AND WATER ASCENT 61

SECTION V. REPRODUCTION

A. SEXUAL REPRODUCTION 64

The Flower and its Parts 64

Pollination in Papilionaceous Flowers 68

Structure of Papilionaceous Flowers 69

PART II. THE PLANT GROUPS
SECTION VI. THALLOPHYTES (ALGJG AND FUNGI)

A. THE ALG.E 75

Protococcus (Pfatrocoeciu) 75

Chlamydomonas 76

Spirogyra t 77

Vaucheria 79

(Edogonium 81

General Study of Fresh-Water Algae 82

Fucus vesiculosus . ... 83

CONTENTS vii

PAGE

B. THE FUNGI 86

Yeast 86

Bacteria • 89

Molds .'•. 92

Mushrooms and their Allies 97

Mushrooms and their Allies (Rusts and Smuts) .... 100

Lichens 101

Lilac Mildew 102

SECTION VII. BRYOPHYTA (LIVERWORTS AND MOSSES)

A. HEPATIC^ (LIVER WORTS) 103

B. Musci (MoBSKs) 108

SECTION VIII. PTERIDOPHYTA (FERNS, EQUISETA,
AND LYCOPODS)

.1. FILICALES (TRUE FERNS) 113

B. EQUISETALES (HORSETAILS) 123

C. L YCOPODIALES (CLUB MOSSES) . 126

Lycopodium 126

Selaginella 127

SECTION IX. GYMNOSPERMS

A. CYCADALES (CYCADS) 130

B. CONIFERALES (SPRUCES AND PlNES) 135

SECTION X. ANGIOSPERMS (DICOTYLEDONS)

Sporophyte 143

Capsella (Shepherd's Purse) 149

PART III. THE SPRING FLORA

SECTION XI. FIELD WORK (DICOTYLEDONS)

A. TREES AND SHRUBS 155

A Method of recording Field Observations ...... 155

viii LABORATORY AND FIELD EXERCISES

PAGE

Gymnosperms (Softwood Trees) 159

Angiosperms (Hardwood Trees) 161

B. HERBACEOUS DICOTYLEDONS 107

A Method of recording Field Observations 167

Ranunculaceae 171

Violaceae 173

Cruciferae 175

Leguminosae 177

Rosaceae 179

Compositae 181

SECTION XII. FIELD WORK (MONOCOTYLEDONS)

A. TRADESCANTIA, TULIP, AND OTHER MONOCOTYLEDONS . . 185

B. SOLOMON'S SEAL (POLYGOXATUM AND SMILACINA) . . . 188

C. IRIDACEAE AND ARACEAE 190

D. GRAMINEAE 191

SECTION XIII. PLANT ASSOCIATIONS

Nature and Composition of Plant Associations 192

Kinds of Associations 194

Origin of New Associations 195

INDEX . . 197

LABORATORY AND FIELD EXERCISES
FOR "GENERAL BOTANY"

PART I. BIOLOGY OF THE HIGHER
SEED PLANTS

SECTION I. PLANTS AND THE
ENVIRONMENT

A. THE BODY PLAN AND FORM OF PLANTS
THE LILAC

1. Leaves. Do the leaves spring from definite points on the

axis of the main stem and its branches, or are they
irregularly arranged? Are they cyclic (two or more
leaves attached at the same level) or spiral in arrange-
ment ? Are the leaves so placed as to give the maximum
light to each leaf ? Observe the shoot from above. How
many rows of leaves are there along the stem ? Be able
to explain the light relations of the leaves. Consult
Figs. 5 and 6 of the text.1

2. Buds and branches. How are the buds related to the leaves

as regards* position and arrangement on the stem and
branches ? Is there a terminal bud in the lilac ? Do
the branches have the same orderly arrangement as the
buds and leaves ? "Why ? Do branches grow from buds ?

3. Stem divisions. Is the stem divided into regular divisions

by the origin of leaves, buds, and branches from definite
points ? Consult the text under The Form and Plan of
the Plant Body concerning the nature and relation of
nodes and internodes.

a. Sketch an entire shoot of a lilac in outline to show the
orderly plan upon which it is constructed. Eemove
the leaves on the side of the branch facing you and

1 All text references are to Densmore's "General Botany."
3

LABORATORY AND FIELD EXERCISES

.Terminal bud

3 Subliminal latwal bud

indicate their position by drawing the scars left by
their removal. Note the bud above the scar, formerly
in the axil of
the leaf.

I. Read text on The
Form and Plan
of the Plant
Body. Label all
the parts of the
finished draw-
ing correctly.
Name the buds
on the basis of
position, that
is, terminal or
lateral. Con-
sult Figs. 38
and 45 of text.
4. The structure and

growth of buds,
a. Plan of the bud.
Observe the ex-
ternal surface
of the largest
buds on your FIG. 1. Parts of a shoot with a spiral
specimen. Use body plan

hand lens for The diagram represents a single year's growth
of a woody shoot. The bud-scale scars mark
details. Have the lower limit of the year's growth

the parts of the

bud a definite arrangement ? Is this arrangement the
same as that of leaves on the main stem ? Separate
the parts of the bud carefully and observe their
origin and arrangement. Is there a central axis to

BIOLOGY OF HIGHER SEED PLANTS

which the parts are attached ? This point can be
demonstrated by bisecting the bud. See Fig. 2, and
Fig. 37 (p. 68) of the text.

b. Sketch the external surface of a bud and label its parts.

c. G-rowth of buds. Do all of the buds in the axils of the

leaves grow each season ? Ex-
amine older portions of the
branch to determine this point.
Are the branches produced each
season of the same length and
vigor ? Note the forked branch-
ing due to the growth of the
two vigorous subterminal lat-
eral buds. Can you determine
the age of the branch you are
studying ? Look for the scars left
by the bud scales each season
(Fig. 1, and Fig. 38 of the text).

5. The shrubby form of the lilac. Study

the form of the branch with which
you are working, as well as that
of lilac shrubs in the field. Is the
rounded, shrubby habit of the lilac
due to the arrangement and method
of bud growth ? For example, sup-
pose the lilac shoots had a single
continuous terminal bud instead of the two subterminal
ones. Would this change the form and habit of the plant ?

6. Summary of observations. Answer the following ques-

tions in the form of a summary on your laboratory sheets :

a. What relation exists between the position and arrange-

ment of leaves, buds, and branches in the lilac ?

b. What is meant by the body plan of the plant body ?

FIG. 2. Vertical section
of a hawthorn bud

br and o, outer and inner
bud scales; i, ilt outer
and inner leaves ; g,
growing point, or meri-
stem, of the bud. From
Bergen and Caldwell's
"Practical Botany"

LABORATORY AND FIELD EXERCISES

c. What relation have the position and growth of buds to
the form of the lilac shrub ? Illustrate this point by
means of an outline sketch.

HERBACEOUS PLAXTS

Use the catnip, ragweed, aster, or similar herbaceous plants
for this study.

1. The main axis. What is the form of the entire central

axis of the plant, including both stem and root ? Is this
central axis me-
chanically adapted
to the support of
the lateral roots,
branches, and leaves ?
Be able to explain
to an instructor. Is
the main axis of the
stem the same in
shape as that of the
root ? Is the entire
axis divided into
nodes and biter-
nodes ? Are the in-
tern odes of the
same length in all
parts of the axis ?

2. Lateral members. Are

the leaves cyclic or
spiral in arrange-
ment ? How many
of the lateral buds
have produced branches ? Have these lateral branches
the same plan and leaf arrangement as the main

FIG. 3. Cyclic body plan and leaf dis-
play of the milkweed (Asclepias)

Note that the cyclic leaf arrangement
secures the maximum light exposure. Pho-
tograph by Jesse L. Smith. From Bergen
and Caldwell's "Introduction to Botany "

BIOLOGY OF HIGHER SEED PLANTS 7

axis ? Have the lateral roots the same arrangement
as the leaves and branches ? Have they any definite
arrangement ?

3. Bud structure, arrangement, and growth.

a. Structure. How do the buds of an herbaceous plant,

like the catnip, ragweed, or aster, differ from those of
a woody plant like the lilac ? Can you give reasons
for the differences observed, based upon the annual
and perennial habits of the two plants ?

b. Arrangement and growth. Compare the buds of the

herbaceous plant examined with those of the lilac as
regards arrangement and mode of growth. Is the form
of the plant you are examining determined by the
differences in the time and rate of growth of the ter-
minal and lateral buds ? For example, why are the
upper branches shorter than the lower ? Why is the
main axis longer than any of the branches ? How
explain the conical or rounded form of herbaceous
plants 011 the basis of bud growth?

4. Light, air, and soil relations. What is the form of the

entire plant under examination ? Are the leaves, flowers,
and seeds effectively displayed to sunlight and to air
currents ? Are the tips of the lateral absorbing roots
properly placed for absorbing water and soil salts ?
Consult Figs. 8 and 9 of the text.

a. Construct an accurate outline drawing of the plant you
are studying, indicating the following points :

(1) The form of the main central axis and the arrange-

ment of lateral members.

(2) The plan of the lateral branches, including the posi-

tion of leaves, flowers, and fruits if present.

(3) The general form of the entire plant and the display

of absorbing leaf and root surfaces.

PLANT BODY

INCOttE

OUTGO

l ENERGY

b Liquid

c Solids in i
• Solution}

FIG. 4. Diagram illustrating the general nature of the income and outgo
of a green plant from the forces and materials of its environment

The student is expected to fill in the details under the captions Energy, Gases

Liquids, and Solids (consult Chapter I in the text). Do not fill in a detail unless

it is correct to do so. The diagram is merely suggestive

BIOLOGY OF HIGHER SEED PLANTS 9

THE RELATION OF THE CATNIP, EAGWEED, OR ASTER TO
THE ENVIRONMENT

1. Read Chapter I of the text carefully. Indicate in connec-

tion with a diagram of a catnip, ragweed, or aster the
income and outgo of the plant as outlined in Fig. 4
of these exercises.

2. Summarize in your notes the essential differences between

the income and outgo of the plant sketched and that of
a man. Consult Figs. 2 and 3 of the text and the
accompanying discussion in Chapter I.

TREES
SPRUCES AND PINES

1. Form and general arrangement of parts.

a. Are the pines and spruces of the erect or of the spreading

type ? Compare them with oaks, maples, and similar
trees. What determines the fact that the pine has
a continuous excurrent trunk ? What determines
the uniform gradation in the length of the branches
from the apex to the base of the tree ? Do the
branches appear to have any regular arrangement on
the trunk ? Eecall your work on the growth of buds
and branches in the lilac.

b. Are the leaves properly disposed over the crown to

secure the maximum amount of sunlight ? Does the
form and the angle of divergence of the upper and
lower branches from the tree trunk contribute to the
exposure of the leaves to light ? Are the cones and
seeds favorably situated for seed dispersal?

c. Sketch the spruce or pine tree examined, in a manner

similar to that outlined for the lilac and the herb.

10 LABORATORY AND FIELD EXERCISES

Draw a few branches with leaves on the upper,
middle, and lower portions of the trunk. Indicate
the position of the remaining branches by circles or

frogeotropic
taproot

Dingeotropic roots

FIG. 5. Pine trees illustrating the erect type

a, a young pine ; 6, a mature pine. Observe the excurrent trunk, the false whorls
of branches, and the pyramidal form. Consult the text for the main factors con-
cerned in the seasonal growth (1-7) and the development of these external features
of the pine

other symbols. Consult Fig. 5 above and the text
discussion on the form and development of the pine.
d. Summarize briefly the facts relating to bud and branch
growth which determine the erect pyramidal form
of the pines and spruces.

BIOLOGY OF HIGHEK SEED PLANTS 11

2. The plan and development of the branches. Select the
terminal portion of a branch of a spruce or pine rep-
resenting three or four years of growth in length.
The spruce is best for this study, but a pine branch
may be used.

a. The parts and their arrangement.

(1) Are the leaves cyclic or spiral in their arrange-
ment ? This is most easily determined on naked
portions of the twigs by means of the leaf scars.
What is the number and position of the buds?
Is there a bud in the axil of each leaf, as in the
lilac ? Are the branches disposed like the buds on
the main axis? Are the smaller twigs arranged
like the main branches ? Is the relation between
leaves, buds, and branches the same as in the
lilac and the herbaceous plant studied ?

b. Seasonal growth of buds and branches.

(1) Determine the limits of each season's growth in

length on the main axis and the lateral branches.
Is there a uniform number of buds which grow
each season to continue the central axis and to
produce lateral branches ? Are some branches
more vigorous than others ? Do the vigorous
lateral branches produce twigg and buds disposed
like those on the main central axis of the branch ?
Observe old branches of pine and spruce. What
becomes of the lateral branches produced each
season ? Do the leaves persist on the main axis
between the annual branches ? The clusters of
lateral annual branches in the pine and spruce
are called false whorh of branches.

(2) Sketch the entire branch examined above, to illus-

trate the points outlined under a and b. Illustrate

12 LABORATORY AND FIELD EXERCISES

the arrangement of the leaves on a small portion
of a single twig. Label all parts correctly.
(3) Sketch, in outline merely, a long mature branch.

Label correctly.
3. The plan and development of the tree.

a. Compare the arrangement of the branches and buds on

a small tree with those of the branches just studied.
Are the branches grouped on the tree trunk as the
smaller branches and twigs are grouped on the main
axis of a branch ? Compare the tree with the larger
branch sketched above. Did these groups of branches
on the main trunk arise originally from lateral buds
as on the branch studied above ? Why are they
called false whorls of branches, instead of true
whorls ? Are there smaller branches on the trunk
between the false whorls of vigorous branches ?
Compare the spruce and the pine in this respect.
How do you account for the naked portions of the
trunk of the pine between the false whorls of
branches ? How do you account for the naked trunk
below the lowermost branches ?

b. Observe the spruce and the pine from a short distance.

Can you determine the limits of the last season's
growth at the apex of a tree ? How many buds
grew last season, including the terminal bud and
those which produced vigorous lateral branches ?
Can you determine the limits of each season's growth
along the tree trunk ? Where are the nodes and
internodes on the main central axis of the pine or
the spruce ?

c. Sketch the last three or four years' growth at the

extreme apex of a pine or a spruce. Label the parts
correctly.

BIOLOGY OF HIGHER SEED PLANTS 13

d. Summarize the relation of the following factors in the
development of the conical form and the false whorls
in the spruce and pine:

(1) The number and position of the buds that grow

each season.

(2) The spiral plan of the pine and the spruce, and its

relation to the false whorls of branches.

(3) The effects of pruning. Consult the text (pp. 19

and 20) on the development of the pine.

THE AMERICAN ELM

Select a terminal shoot of an elm representing three or four
years of growth, and observe the following points, as in the
pine and spruce just studied :

1. The plan and development of an elm branch.
a. Leaves and buds.

(1) Compare the leaf and bud arrangement on the elm

branch with that of the lilac, ragweed, and spruce.
Are the leaves and buds in the elm arranged like
those of any one of the plants thus far studied ?
Is the leaf arrangement favorable to the maximum
exposure to light ? Observe an entire elm branch
from above. Observe the leaf petioles. Do they
curve so as to bring all of the leaves in one
plane ? Observe the buds. Is there a true ter-
minal bud or is it subtemiinal, that is, just below
the apex of the shoot ?

(2) Sketch a single terminal twig of the elm to illus-

trate the arrangement of buds and leaves and the
light relation of the leaves. Label parts carefully.
1. Seasonal growth of buds and branches.

(1) Determine the age of the main axis and of the
lateral branches by means of bud-scale scars.

14 LABORATORY AND FIELD EXERCISES

(2) Study the annual growth of the main central axis and

of the larger lateral branches. How many seasons
of growth in length are represented in each ?

(3) How many buds, including the subterminal and

lateral buds, grew to produce the central axis and
lateral branches of the last season's growth at the
end of the shoot ? How many buds, including the
subterminal and lateral buds, grew into branches
in each of the previous seasons represented on
the shoot you are examining ? Is there a general
similarity in the number and size of the branches
produced each season ? Did the main axis of the
branch grow equally each season ? (See Fig. 6.)

c. Vigorous buds and branches. Are the larger branches

produced at about the same place, and are there
approximately the same number each season ? Is
there any similarity in the number and position of
weaker branches produced annually ?
(1) Study the buds laid down on the main axis and
the lateral branches for next season's growth.
Are some larger than others ? Have these larger
buds the same relative position as the stronger
branches on the annual growths of previous years ?
As the branch grows larger, what becomes of the
vigorous lateral branches and of the weaker ones
of each season? Observe a large branch to deter-
mine this point.

d. Comparisons. Compare the elm branch and that of the

spruce or pine already studied as regards the annual
growth of buds into branches. To what do the vigo-
rous seasonal branches of the elm correspond in
the pine ? Did you find anything in the pine or spruce
corresponding to the weaker annual branches in the

BIOLOGY OF HIGHER SEED PLANTS 15

elm. ? Be able to explain any difference observed in
this respect. As the elm branch grows, what becomes
of the stronger and the weaker branches ?
e. Drawing. Remove the leaves from the branch under
observation. Draw the entire branch in outline,
indicating clearly the following structures :

(1) The limits of each season's growth in the length of

the main axis and the lateral branches.

(2) The vigorous and the weaker branches of each season.

(3) The vigorous and the weaker buds in the terminal

twig of the main axis and one or two lateral
branches.

2. The plan and development of the tree. Study young and
mature elm trees in the field, beginning observations
with a young elm.
a. Younj elms.

(1) Observe carefully the main trunk or central axis

of a young elm and the arrangement of the
branches. Compare the arrangement of the vigor-
ous and the weaker branches of the tree with
that of the branch studied above. Can you
determine the limits of annual growth on the
main trunk, as you can on a branch, by the vigor-
ous lateral branches produced each season ? Are
the weaker branches being pruned by shading ?
Consult Fig. 6 and the text discussion on page 21.

(2) Do you find anything corresponding to the false

whorls of branches of the pines and spruces?
How does the elm differ from the latter trees
in the production of false whorls of vigorous
branches ? Did the trunk of the elm below the
present branches ever have lateral branches ? If
so, why is the trunk smooth now ?

16

LABORATORY AND EIELD EXERCISES

FIG. 6. Growth of the American elm, an illustration of the spreading
type of trees

The letters from left to right show several stages in the development of the
elm. The ultimate form is determined by the hody plan, the method of bud
growth, and the pruning effects. The corresponding letters on each figure in-
dicate the vigorous (and so successful) branches produced each season. For
further discussion consult the text

(3) Sketch a young elm to show the vigorous branches,
which correspond to false whorls in the pines,
the annual growths in the length of the main
axis, and the weaker branches. Indicate also the
scars or other markings where branches have
already been naturally or artificially pruned.

BIOLOGY OF HIGHER SEED PLANTS IT

b. Older elm trees.

(1) Examine older trees of the American elm with the
points iii view which you observed above in
young elms. Is the main crown of an old elm
tree formed entirely from the so-called false whorls
of vigorous branches laid down in the young elm ?
Study the mode of growth of the main branches
from base to apex. Do they repeat in their growth
the history of the tree? Consult Fig. 6 (a-/),
and Figs. 12 and 25 of the text.

c. Summary. Summarize briefly the part played by

each of the following factors in the development
of the elm :

(1) The spiral body plan and the differences in the buds

produced each season as regards size and vigor.

(2) The unequal growth of the buds each spring and

the difference in the development of the branches
produced by them.

(3) The effects of natural and artificial pruning.

(4) The annual leaf display.
Consult the summary in the text (p. 23).

SUPPLEMENTARY THEE STUDIES

Some trees illustrate the above principles relating to tree
development more strikingly than the elm. This is particularly
true of young Norway maples and the Carolina poplar. Study the
development of these and other deciduous trees with reference to
the three principles deduced from the study of the pine and the
elm. These principles are the body plan or arrangement of leaves,
buds, and branches ; the unequal vigor and growth of buds and
branches ; the effects of pruning in eliminating all but the most
vigorous branches, which then occur in false whorls resembling
those of the pine.

18 LABORATORY AND FIELD EXERCISES

B. ADJUSTMENT TO THE ENVIRONMENT
THE EMBRYO AND SEEDLING OF THE BEAN

1. Structure of the seed and embryo.

a. Eemove the protective seed coat from a soaked seed of

a garden bean and study the embryo. The parts of
the bean embryo are similar to those of the pea
(Fig. 13 of the text). Compare with A and B, Fig. 7.

b. Find the two large food-storing leaves, or cotyledons,

comprising the bulk of the embryo. Remove one
cotyledon. Observe the plumule, or terminal bud of
the embryo, composed of two or three delicate leaves.
Find also the hypocotyl, or stem which bears both
cotyledons and plumule. The first, or primary, root
also grows from the end of the hypocotyl.

c. Draw the parts of the embryo as they appear with one

cotyledon removed.

2. Adjustment of the embryo by tropisms or movements.

a. Emergence of the embryo from the soil. How is this

accomplished ? Sketch a plant which has just emerged
from the soil, indicating the position assumed by the
various organs. Contrast the bean with the pea and
morning-glory (Fig. 7). Label correctly.

b. Adjustment of the organs of the bean to the environment.

(1) Study two or three stages in the development of

growing seedlings of beans. Observe the changes
in the position of hypocotyl, epicotyl, leaves, and
roots as development proceeds,

(2) Sketch the most mature seedling observed, and also

younger seedlings, to show the positions assumed
by the organs at each stage. Label all parts
correctly.

BIOLOGY OF HIGHER SEED PLANTS
I

19

FIG. 7. Seed and seedlings of morning-glory

A, section of seed, showing the embryo surrounded by the endosperm ; B, C, D,

stages in the development and adjustment of the embryo to light and soil; cot,

cotyledons; pi, plumule

c. Special motor organs, or pulvini.

(I) Observe the pulvini of the bean leaves (Figs. 15 and
16 of the text). How do they differ from the
remainder of the petiole ? Study the form of the
pulvinus on leaves in different positions. Do you

20 LABORATORY AND FIELD EXERCISES

observe changes in the form of the pulvini cor-
responding to the positions assumed by the leaves ?
How does the pulvinus effect the movement of
the leaf blade ?
(2) Draw a leaf with pulvini greatly magnified. Label

all parts of your drawing.

d. Naming of stimulus and response. Label the parts of
the largest seedling drawn in such a manner as to
indicate the tropism and response of each organ in
accordance with the nomenclature given on page 30
in the text.
3. Experiments. Observe the following experiments on the

tropisms of the bean seedling :

a. Place one growing seedling of a bean in a horizontal
position, and another in an erect position, in a place
where the lighting will be uniform on all sides.
Observe at successive laboratory periods until both
plants are adjusted in their positions. Write up the
experiment after the following plan, indicating actual
results by drawings properly labeled to indicate the
kinds of stimuli and the nature of the response in
each instance.

(1) Object in view in performing the experiment. What

do you expect to prove ?

(2) The method and conditions under which the experi-

ment is performed. Make outline drawings of the
two plants to indicate the position of leaves and
stems at the beginning of the experiment.

(3) Actual results observed on each plant after several

hours. State the changes observed in each plant.
Indicate these changes by outline drawings. Ex-
plain the mechanism of the response in the case
of each organ. Label each organ, indicating the

BIOLOGY OF HIGHER SEED PLANTS 21

nature of the stimulus and response ; for exam-
ple, apogeotropic. Consult the text discussion
(pp. 28-31) concerning the mechanism of response
in plants and the naming of stimulus and response.
(4) Conclusions. State briefly your conclusions from
the above experiment as to the relations existing
between the bean plant and some of the forces
of the environment.

b. Place two plants before a window. Rotate one on a

clinostat. Observe and record as indicated above
after several hours, when the plants have become
adjusted to the new environmental conditions.

c. TJie gravity sense. Observe germinating seeds of corn

or beans with protruding roots which are rotated on
a clinostat, as in Fig. 18, a-d, of the text. Compare the
position assumed by the rotated roots and hypocotyls
with positions taken by these organs in seeds pinned
to a stationary disk, Record the object, method,
results, and conclusions as in experiment a, above.

SUPPLEMENTARY STUDIES

Adjustments of common plants to the environment. Observe
common plants in the field and in the laboratory, and record the
positions assumed by the various organs. Eecord the results of
your observations and your conclusions in a manner similar to
tluit indicated above for writing up experiments on movements.
The dandelion (Taraxacum\ white sweet clover (Melilotiis),
cultivated geranium, and some climber, such as the ivy, are
good species for observation. At least one such plant should
be assigned to each student to work up independently and hand in
with appropriate drawings and notes.

SECTION II. CELL STRUCTURE AND GROWTH

A. THE CELLULAR STRUCTURE OF PLANTS

1. Mounting sections. Mount sections of cork, pith, or similar

materials as follows for microscopic observation : Clean
a slide and cover glass as directed by an instructor.
With the point of your scalpel or with a small brush
place a section of pith or cork in the center of a glass
slide. Add a drop of alcohol with a pipette. Take a
clean cover glass with forceps, or grasp it by its edges
between thumb and forefinger. Place one edge of the
cover glass on the slide at the edge of the drop of alcohol
and gently lower the cover glass over a specimen.
This method of placing a cover glass over an object
avoids air bubbles, which appear under a cover glass as
dark rings with light centers. Now observe your section
with the compound microscope as indicated below.

2. Low-power study. Place the section, mounted as directed

above, on the stage of the microscope for observation.
Adjust your mirror until you have a white field, and
make the following observations and drawings:

a. Compare the appearance of your section with that of a

similar section of a honeycomb. Is it made up of
cells, like a honeycomb, with similar bounding walls
and cavities ? Compare your section with a piece of
honeycomb if the latter is available.

b. Make an accurate drawing of a portion of your section

as it appears under a low power. Label the parts
with appropriate terms corresponding to similar
structures in a honeycomb.

BIOLOGY OF HIGHER SEED PLANTS

23

c. Who made the first observations similar to the one
you have just made ? What conclusions did he
draw concerning the structure of plants ? Consult
the text (Chapter IV, p. 54).

3. High-power study. Observe a portion of the above section
under high power, being careful to secure good light.

B D

FIG. 8. Cell and tissue differentiation in plant organs

A, cross section of a root with dark pith, light vascular bundles, and dotted
cortex ; B, cross section of flower stalk with tissues as in A but with an outer
layer (dark) of thick-walled strengthening collenchyma cells ; C, single-celled alga
with nucleus (n) ; I), cross section of a square-stemmed plant (col, collenchyma,
as in B ; fv, fibrovascular bundles ; pith and cortex dotted)

a. Cell ivalls. Note their thickness, color, and connections
in adjacent cells. Is the cell wall split at the junc-
tion of adjacent cells to leave minute spaces, called
intercellular spaces ?

fi. Cell cavities. Note their size, shape, and , contents. Are
the cell cavities of adjacent cells similar in these
respects ? Do the cavities of these cells contain
anything besides air ?

24

LABORATORY AND FIELD EXERCISES

c. Draw two or three cells greatly magnified (half an inch
in diameter), to illustrate the parts of plant cells as
seen under a high power. Label all of the parts of
one cell carefully.

CELL-WALL THICKENING AND CELL DIFFERENTIATION

1. Sections of celery, corn, or a similar plant.

a. Cell differentiation. Observe the entire section with

the low power of a compound microscope. Are
the cells in different parts of the section of uniform
size and form ? Why
should one expect to
find different kinds of
cells in the cell col-
ony which makes up
the structure of any
stem, leaf, or root ?
Observe any definite
order or grouping of
similar kinds of cells.
Explain such group-
ings on the basis of
use, or function, in
a celery or corn stalk.
The regular oval cell
masses are vascular
bundles, which con-
duct water and foods up and down the stem.

b. Make an outline sketch of the entire section as it ap-

pears to the naked eye or with a hand lens. Shade
in the areas showing thick- walled cells, and outline
the vascular bundles. Consult Fig. 7. Label.

FIG. 9. Epidermis and collenchyma

ep, epidermis; col (collenchyma), the
thick-walled cortex cells; th, thick-
walled portion of collenchyma cell

BIOLOGY OF HIGHER SEED PLANTS

25

c. Cell-wall thickening. Focus with a high power on some

thick-walled cells in the section. Observe the thick-
ness of the cell wall and the size of the cell cavity.
Are there intercellular spaces as in the thin-walled
pith cells ? Consult the text
concerning the mode of cell-
wall thickening (p. 48).

d. Draw three or four thick- walled

cells.
2. Vegetable fibers in paper.

a. Examine pieces of filter paper

and newspaper under the low
power of a compound micro-
scope. What appears to be the
composition of the paper ? Make
a rough sketch to indicate the
structure as it appears under
low power.

b. Tease out a small piece of each

kind of paper with needles in
a drop of water and mount
separately on the middle of a
glass slide. Cover with a cover
glass and study with both low
and high powers of the com-
pound microscope. What is the shape of these
vegetable fibers ? Have they a cell wall and a cell
cavity ? Compare them with the thick-walled cells
observed in celery.

c. Draw two or three fibers accurately from each specimen

examined and label their parts. Consult Fig. 10 of
these exercises. The fibers of which paper is made
resemble C in structure and in shape.

ABC

FIG. 10. Thick-walled
fibrous cells

A, tracheid from pine

wood ; B and C, fibrous

cells

26 LABORATORY AND FIELD EXERCISES

d. What is the function of thick-walled cells and fibers in

plants? What function do they serve in the celery
stalk examined above ? Why is a cornstalk hard on
the outside ? What makes a bamboo fishing rod so
strong ? What is the nature of the covering of hick-
ory nuts and other similar nuts ? See Figs. 8, 9 and
10 of these exercises.

e. Summarize the functions of thick-walled cells and vege-

table fibers in plants, and state some of their important
economic uses.

PROTOPLASM, VACUOLES, AND NUCLEI IN
ROOT-TIP CELLS

1. Study of the text and sections. Read the text concerning
the nature of protoplasm, vacuoles, and nuclei. Study
these parts of the cell in sections of root tips which
have been previously stained and mounted for this pur-
pose. Transverse sections of root tips are especially
favorable for this first study of cells with protoplasmic
contents.

a. Low-power study. Study the cells immediately beneath

the outer bounding cell layer.

(1) Protoplasm and vacuoles. Find cells in different
stages of vacuole formation as described in the
text and illustrated in Fig. 27. Do you find cells
in which vacuoles are just beginning to form ?
cells in which the vacuoles are large light spaces
surrounding the nucleus ? cells which appear to
have a continuous large central vacuole? These
may be found in deeper-lying cells of the section.

b. High-potver study. Select a favorable cell and study

the following structures with a high power:

BIOLOGY OF HIGHER SEED PLANTS 27

(1) The nucleus. What is the general nature of the

nuclear protoplasm ? Does it appear granular or
homogeneous ? Compare the nuclear protoplasm
with the regular cell protoplasm or cytoplasm.
Can you detect a thin nuclear membrane, or wall,
around the nucleus, and a darker granule, the
nucleolus, within the nuclear cavity ? Is the
nucleus located in the center of the cell ? How
is it supported in this position ?

(2) Vacuoles. What forms the bounding walls of the

vacuoles ? What are they supposed to contain in
living cells ? What is the origin of vacuoles and
how do they grow ? Consult the text.

(3) The cytoplasmic sac. What is the cytoplasmic sac

and how formed ? What relation does the cyto-
plasmic sac bear to the general protoplasm of the
cell ? to the central vacuoles and to the cell wall ?

(4) Draw two cells greatly magnified (one inch in diam-

eter) to illustrate two stages in the formation of
vacuoles. Put details of the nucleus and cytoplasm
in each cell.

CELL STRUCTURE AND PROTOPLASMIC STREAMING IN
STAMEN HAIRS OF TRADESCANTIA (SPIDERWORT)

1. Mount some of the delicate, haiiiike outgrowths (stamen

hairs) which grow out from the stamens in flowers of
Tradescantia, the common spiderwort. Preserved ma-
terial may be used for the cellular structure of the
stamen hair.

2. Low-power study. What is the general cellular structure

of a stamen hair ? , How do the cells composing it differ
in size and form at the smaller apex and at the larger

28 LABORATORY AND FIELD EXERCISES

basal portion of the hair ? How are the cells joined at

the ends ? Have they cell contents ? See root-tip cells.

a. Draw a figure illustrating the form and appearance of

the cells of a stamen hair as seen under low power.

Label all parts observed.

3. High-power study. Select large cells near the base of a
stamen hair in which the internal structures are plainly
visible.

a. Compare the structure of such stamen-hair cells with
that of root-tip cells as regards the following points :

(1) Cell shape and outline. How do stamen-hair and

root-tip cells differ in form and outline ? Can you
think of a reason for the differences you see ?
What is the geometrical form of a stamen-hair
cell at the larger basal end of the hair ? at the
smaller apical end ?

(2) Cell wall. Is the cell wall smooth or roughened?

thick or thin ? colored or colorless ?

(3) 'Cell contents.

(a) The nuclei. Where are the nuclei located in

different stamen-hair cells ? Have they the
same position in all cells of a single hair ?
Can you determine by focusing whether the
nucleus is in the center of the cell or next
to the cell wall ? Try this experiment in
different cells. Eesult ? Be able to explain
to an instructor.

(b) The cytoplasm. Do you find cytoplasm around

the nucleus ? How is it disposed in other
parts of the cell ? Is it denser in some areas
than in others ? What is the character of the
cytoplasm as seen under high power ? What
parts of it are visible ? What do you conceive

BIOLOGY OF HIGHER SEED PLANTS 29

to be the structure of the cytoplasm in these
stamen hairs ? Compare with root-tip cells,
(r) The vacuoles. How many vacuoles are there in
the stamen-hair cells ? Are the cells all alike
in this respect ? Is there a cytoplasmic sac in
all stamen-hair cells ? What relation does the
nucleus sustain to the vacuole and to the
cytoplasm ?

(4) Draw the following diagrams of a stamen-hair cell
to illustrate its form and structure : Draw the
cell as it appears when the nucleus is in focus.
What kind of view of the cell is this ? Express
this view by an appropriate term. Construct a
transverse section of a cell as it would appear if
cut through the nucleus.

4. Living stamen hairs and protoplasmic streaming. Mount
living hairs of Tradescantia in water and observe with
low and high powers for protoplasmic movement.

a. Lmv-power observations. To what is the color of the

stamen-hair cells due? Can you 'detect the nucleus
and the protoplasmic strands ? Select a good cell
for observation, and focus upon it carefully with
high power.

b. Hlijli-power study of living protoplasm and its movements.

What seems to be the nature of the living protoplasm
of a stamen-hair cell ? How would you describe it ?
Does the protoplasm exhibit movements ? Is there
one general movement of the protoplasm or are there
several streams ? Is the movement definitely related
to the nucleus ?

c. Draw a stamen-hair cell showing the position of the

nucleus and cytoplasmic strands. Indicate by arrows
the direction of movement of the protoplasm.

30 LABORATORY AND FIELD EXERCISES

PLASTIDS IN PLANT CELLS

CHLOROPLASTIDS IN CELLS OF ELODEA CANADENSIS
(WATER WEED)

1. Mount in water young leaves of Elodea selected from
the apex of Elodea plants, and observe as follows :

a. Cellular structure of the Elodea leaf.

(1) What is the nature of the cells which compose the

Elodea leaf ? Are they uniform in size and shape ?
What is the color of the cell walls ? What is the
nature of the cell contents ?

(2) Draw ,an outline diagram of the Elodea leaf. Indi-

cate, by lines or by shading, the main cell areas
of the leaf. Fill in three or four cells of each area
to show the cell structure of the leaf.

b. Chloroplastids. Observe the form and appearance of

the green grains, or plastids, in the ElodeaAe&i cells.
Do these plastids occupy the same position in all
the cells'? Is there any regular or uniform position
assumed by the plastids ?

c. Protoplasmic streaming. This is usually best observed

in the elongated cells composing a central strand,
or midrib, in each leaf.

(1) Observe this streaming movement. Is there one

direction for the movement of protoplasm in
different cells in Elodea ? Does the protoplasm
stream from cell to cell through the cell wall ?
Do these cells have a cytoplasmic sac ?

(2) Draw two or three cells of Elodea accurately, indi-

cating the form and position of the plastids. Indi-
cate directions of movement by means of arrows.
Draw two or three plastids greatly magnified.

BIOLOGY OF HIGHER SEED PLANTS 31

d. Composition of cJiloroplastids. Select shoots of Elodea
which have been previously boiled to kill the plas-
tids. Place one or more shoots in a test tube in
ninety-five per cent alcohol and observe frequently.
Does the alcohol change color ? "Why ? Allow these
test tubes to stand until the next exercise. Examine
the alcohol, the plants, and the plastids. Do the
plants appear to be somewhat bleached ? Explain.
What are the parts of a chloroplastid ? Answer the
above questions in your notes, indicating the form,
parts, and function of chloroplastids in cells of Elodea.

CHROMOPLASTIDS

1. Examine chromoplastids in the cells of flowers (for ex-

ample, Nasturtium) and fruits (for example, tomato and
bittersweet berries). Draw the chromoplastids examined.

2. See the text discussion of the structure and functions of

plastids.

B. CELL STRUCTURE AND GROWTH
GROWTH

1. Growth of root tips in living roots of corn or beans.

a. Observe growing root tips which have been previously

marked with uniform millimeter spacings and then
allowed to grow for twenty-four hours or more. In
what part of the root tip has growth taken place ?
How long is the growing zone as indicated by the
millimeter spaces ? Does the root grow at the
very tip ?

b. Draw a root which has grown in the manner indicated

above. Indicate the length of the millimeter spaces

32 LABORATORY AND FIELD EXERCISES

accurately. Locate the rootcap if possible. Consult
the text on the parts of the root tip and label your
figure correctly.

2. Cellular structure and cell growth of root tips. Select
prepared slides cut lengthwise through growing root
tips and study the cellular structure of the main root-
tip areas.

a. Note the division of the root into an outer epidermal

cell layer, a central axis cylinder, and an interme-
diate cortex, each composed of similar cell elements.
Consult the text figures and Fig. 11 on the structure
of the root tip.

b. Rootcap. What is the character of the cells of the

rootcap ? Do its cells differ at the extreme apex of
the root and at its upper border ? What is the geo-
metrical form of the rootcap ? How is it related to
the growing meristem cells and the growing cell
zones above it ? What is the function of the root-
cap ? How is it renewed when worn off by the soil ?
• c. Meristem layer. What is the form and extent of the
meristem cell layer ? What are the distinctive char-
acteristics of its cells as regards size, form, and
cell contents ? Is the meristem a distinct layer of
cells or do its cells merge into the cells of the
rootcap below it and into those of the elongating
zone above it ?

d. Elongating zone. Study the cells at the lower and upper
margins of the elongating zone. How do they differ
in these two regions from the cells in the central
region of the elongating zone ? Explain the changes
which you note in the cells of the elongating zone
from its lower to its upper margin. How are these
changes in the cells brought about? How is the

BIOLOGY OF HIGIIEll SEED PLANTS

33

elongating zone renewed when its cells become con-
verted into cells of the maturing and permanent
zones of the root above it ? Consult the text.

FIG. 11. The growth of cells in a root tip

a, main areas of the root tip, shaded ; b-e, camera drawings of cells from the

various regions of the root as indicated in the figure. Note the changes in form

and si/e of the cells as growth proceeds. The nuclei grow with the cells, hut they

occupy a proportionately smaller part of the cell cavity as the cells enlarge

Permanent zone. How do the cells above the elongating
zone differ from the cells below them in form and
in cell contents ? Explain the changes which have
taken place in these cells with their growth.

34 LABORATORY AND FIELD EXERCISES

f. Drawings of cells characteristic of each root zone.

(1) Select a small group of about three cells from each

zone of the root, and outline each cell group on
the same scale as that shown in Fig. 11.

(2) Fill in the details of cytoplasmic and nuclear struc-

ture in a group of cells of the rootcap, meristem,
and elongating and permanent zones. Indicate
clearly the growth of vacuoles and the origin of
the cytoplasmic sac incident to growth. See
Fig. 11 for the proportionate size and form of
cells in the main zones of the root.

3. Elongation. Read the discussion in the text on the method

of elongation of the root by cell division and growth.
Summarize the facts relating to the cellular growth of
the root in length.

4. Structure and growth of buds.

a. Structure of buds. Review the parts of the bud of the

lilac as seen from the exterior. Cut median vertical
long sections of buds and study the cut surface with
a hand lens.

(1) Determine the parts of the bud and their relation
to each other. Is there an apical meristem as in
roots? Observe the relation of leaves to nodes
and internodes. If prepared slides are available,
observe the cellular structure of the above por-
tions of a bud. Make an accurate drawing of a
long section of a bud and compare it with that
of roots. See Figs. 37 and 40 of the text.

b. G-rowth of buds. Observe buds which are expanding

in growth. (Preserved material may be used if fresh
is not available.) What is the general method of
elongation ? Is the elongating zone in buds a con-
tinuous product of the meristem, as in the root ? Is

BIOLOGY OF HIGHER SEED PLANTS 35

the elongating zone in the bud derived from a meri-
stem, as in roots ? Be able to explain the similari-
ties and differences between roots and sterns in these
respects.

c. Summarize in your notes the similarities and differ-
ences between root growth and stem growth by
means of buds. Distinguish between the growth of
woody and herbaceous stems. Consult the text sum-
mary (pp. 69-72) on the growth of roots and stems.

C. THE CELL AND CELL DIVISION

1. Minute structure of the cell.

a. Select a well-stained cell in the cortical region just

above the meristem and study it carefully with the
highest-power ocular and objective available. Read
the text description of such a cell.

b. Do you see any indication of the mesh structure of

cytoplasm mentioned in the text ? What is the
structure of the chromatin ? Can you find the
nuclear vacuole surrounding the nucleolus ?

c. Draw the cell you are observing, greatly magnified, to

show the structure of the cytoplasm and the nucleo-
plasm (chromatin) as they appear in your section.

d. Observe the chromatin in other nuclei of the root tip.

Do you see any of the variations in its structure
noted in the text ?

2. Cell division (mitosis).

a. Prophase. Select a nucleus in a root-tip cell which
shows the condensed condition of chromatin in the
form of chromosomes.

(1) Chromosomes. Is the nuclear membrane still pres-
ent in a nucleus with chromosomes? What is

LABORATORY AND FIELD EXERCISES

the shape and color of the chromosomes ? Are
they all of the same form and color ? Have they
any definite position in the nucleus with refer-
ence to the nuclear membrane ?

(2) Spindle. Do you see any evidence of a forming

spindle at the two ends, or poles, of the nucleus
you are studying ? See the text on the origin
and structure of the spindle.

(3) Cytoplasm. Is the cytoplasm of the same struc-

ture around the nuclear membrane and at the
periphery of the cell ? If any difference is noted,
in what does the difference apparently consist ?
What is the apparent structure of the cytoplasm ?

(4) Draw a cell greatly magnified (1 or 2 inches in

length) to bring out the above points. Draw the
chromosomes very accurately.
b. Metaphase.

(1) The nucleus and the nuclear membrane. Do you

find any definite nuclear membrane and nuclear
cavity in the metaphase stage ? What changes
have taken place in the nuclear membrane since
prophase ?

(2) The chromosomes. Has their form changed since

prophase ? Have the chromosomes a definite ar-
rangement in metaphase ? How are they appar-
ently supported in their position ? If you could
see a polar view of the chromosomes in meta-
phase, what arrangement would they appear to
have ? Indicate this position of the chromosomes
in an outline drawing.

(3) The spindle. Observe the spindle carefully with a

. high power. What is its apparent structure? its
form? Can you determine any definite relation

BIOLOGY OF HIGHEK SEED PLANTS 37

of the spindle fibers to the chromosomes ? What
relation does the spindle sustain to the sur-
rounding cytoplasm ?

(4) Draw a metaphase stage. Outline the entire cell.
Draw in the spindle, the chromosomes, and the
cytoplasm in one half of the cell. Label accurately.

c. Anaphase.

(1) The chromosomes. Note the form and position of

the chromosomes in anaphase. How have the
two sets of daughter chromosomes, seen in ana-
phase, been derived from the single set observed
in metaphase ? Have the daughter chromosomes
the same form as the mother chromosomes of
metaphase? Are they as large as the mother
chromosomes ?

(2) Tlie first spindle. Are there spindle fibers between

the two sets of daughter chromosomes ? If so,
do they have the same appearance as they have
in the polar portions of the spindle ? What is
meant by traction and supporting fibers of a
spindle ? Do you see any such distinction in
the fibers of the anaphase spindle ?

(3) Draw the spindle and chromosomes in an anaphase

stage. Label all parts accurately. Indicate the
position of traction and supporting fibers.

d. Telophase.

(1) Early telophase. Observe, if possible, an early

telophase stage in which the chromosomes are

aggregated at the poles, as described in the text.

(d) Chromosomes. Have the chromosomes changed

their form since the anaphase stage ? What

relation do they sustain to each other ? Are

they separated or joined ?

51U7

38 LABORATORY AND FIELD EXERCISES

(b) Spindles. Are the spindle fibers still present in

early telophase ? Do they form a spindle ?
Are these fibers a part of the original spindle
seen in metaphase ? If so, to what part of
the metaphase spindle do they correspond ?
Do you observe any evidence of traction
fibers in telophase ?

(c) Draw an early telophase stage. Label all struc-

tures accurately.

(2) Late telophase. Select cells in which the daughter
nuclei have begun to form, preparatory to cell
division.

(a) Daughter nuclei. What is their structure ? Have

they a definite nuclear membrane ? What is
the structure of the chromatin in the daughter
nuclei ? Is there any evidence of the chromo-
somes which were seen in early telophase ?

(b) The second spindle. The spindle between the

daughter nuclei is here termed the second
spindle, to distinguish it from the first spindle,
which was concerned with the division of the
nucleus in metaphase and anaphase. What is
the form of the spindle which connects the
daughter nuclei ? Are the fibers evident in all
parts of the spindle ? Are they denser in one
part than in another ? Observe dividing cells
in which the equator of the spindle extends
completely across the cell.

(c) The cell plate. Do you find the cell plate extend-

ing across the equator of the spindle ? Does
it stain like protoplasm ? What is its sup-
posed composition? Does the plate extend
completely across the cell in your specimen ?

BIOLOGY OF HIGHER SEED PLANTS 39

If not, find a cell in which this is the case.
Note the relation of the cell plate to the
spindle.

(d) The cell cytoplasm. What is its relation to this

second spindle ? Is the cytoplasm reforming
hetween the daughter nuclei ?

(e) Draw a stage in cell division, indicating the

structure of the daughter nuclei, the spindle,
and the cell plate. Draw the cytoplasm in
one half of the cell. Make one drawing of
the spindle and cell plate in which the cell
plate extends completely across the cell.

SUPPLEMENTARY STUDIES IN MITOSIS

1. Prophase. Search for nuclei which illustrate the condensa-
tion of chromatin from the resting stage into the chromo-
some condition. See the text on the following changes
in the chromatin during prophase.

a. Irregular dense masses of chromatin. Observe and draw

one or more nuclei in which the chromatin has con-
densed into irregular dense masses. Is there any definite
arrangement of these chromatin masses ?

b. Regular spiral arrangement. Observe nuclei in which the

chromatin appears in a regular spiral thread in the
nucleus. This is usually termed the spireme stage.
Does the chromatin appear to form a continuous ribbon
or is it segmented into rods or chromosomes ? What
changes transform this ribbonlike arrangement of chro-
matin into definite chromosomes ? Is there any evidence
of a spindle's being formed at the poles of the nucleus
you are examining ?

c. Draw the nucleus with the chromatin. Indicate the begin-

ning spindle and surrounding cytoplasm, if the spindle
is forming.

40 LABORATORY AND FIELD EXERCISES

2. Daughter nuclei. Observe, if possible, one or more stages in

the transformation of daughter nuclei into resting nuclei.
See the text discussion concerning the nature of these
changes. Draw the stages of daughter nuclei which you
find, indicating carefully the chromatin changes.

3. Daughter cells. Do you find young daughter cells with re-

formed cytoplasm and nuclei ? How was the cytoplasm
reformed between the daughter nuclei ? Note the chro-
matin and the nucleoli of the daughter nuclei. Draw.

SECTION III. ANATOMY

A. ANATOMY OF STEMS
EXTERNAL FEATURES OF WOODY STEMS

Review the following important external features of shoots
of some common tree like the ash or hickory. See your pre-
vious work on the shoot and buds of lilac and elm.

1. Buds and their relation to growth.

a. How many kinds of buds, as regards position, are there

on the shoot you are studying ? Which buds are
definitely related to nodes ? Are the different kinds
of buds of the same size ? How many buds of pre-
vious years grew into the main shoot or into lateral
branches ? Are the other buds still alive ? Would
they ever have grown into branches ?

b. Age of shoots. Can you determine how many years of

growth are represented in the shoot you are study-
ing ? How are the yearly segments of growth marked
off ? What is the cause of these markings ?

2. The bark and its markings. Is the bark uniform in color

and appearance in the older and younger portions of
the shoot, representing different years of growth ? Peel
off or scrape off the outermost thin brown skin with a
scalpel; what is the color of the tissue beneath it?
Now scrape down to the wood ; do you find any new
tissue layers comprising the bark of the twig ?

3. Scars and markings on the bark.

a. What large scars and markings do you find on the bark
of the entire twig ? What is the nature and position

41

42 LABORATORY AND FIELD EXERCISES

of these scars and markings and what caused them ?
Observe the bark carefully with a hand lens ; do
you tind any minute markings ? Have they a definite
form and distribution ?

b. Drawings. Draw a portion of the shoot you are exam-
ining, representing three years of growth in length.
Indicate clearly the appearance and position of the
buds, the scars marking annual growth in length,
leaf scars, leaf-bundle scars, and lenticels. For the
meaning of these terms consult the text.

GROSS STRUCTURE OF MATURE STEMS

Study wood blocks (preferably oak) cut in cross and in long
section from branches of trees. To give the best results these
blocks should be smooth and polished. Observe with naked
eye and hand lens. Consult the text for a general discussion
of the structures observed below.

TRANSVERSE SECTIONS

1. Bark. Compare the bark of a mature branch in sectional

view and on its surface with that of the twigs observed
above. Is the epidermis still present ? the green bark ?
Compare the bark of a branch of the elm with that of
some other tree in wood blocks. What kinds of tissue
are most prominent in the bark on the branches and
trunks of trees ?

2. The cambium. Locate the position of the cambium layer,

represented by a line just outside of the wood.

3. The wood cylinder.

a. How many annual growth rings are represented in the
block you are examining ? How is the boundary line
between the summer and spring wood of successive

BIOLOGY OF HIGHER SEED PLANTS 43

years marked? What is the relative width and
texture of spring and summer wood.?

b. Observe the number and extent of the wood rays ; do

they all extend to the pith? What is their outer
terminus ?

c. The pith. Observe its size and shape.

d. Do some of your blocks show central heartwood and

outer sapwood ? Compare two or three different kinds
of woods as regards the above points, if specimens
are available.

LONGITUDINAL SECTIONS

1. Compare longitudinal sections of branches, cut in both
radial and tangential planes, with the above transverse
sections. For this purpose it is preferable to use oak
blocks which present for comparison transverse, longi-
tudinal radial, and longitudinal tangential cut surfaces.
a. Compare as follows the different surfaces of wood blocks
prepared as indicated above :

(1) Determine the transverse, radial, and tangential

surfaces of a wood block. Locate corresponding
structures in each ; namely, wood rays, annual
rings of growth, spring and summer wood, and
heartwood and sapwood if present.

(2) What are the distinctive features of radial and

tangential cuts which enable you to distinguish
them ? In a tangential section, is a wood ray
cut across its long axis or parallel with it ? In
a radial section ? What is the actual form of a
wood ray in a tree trunk ?

(3) Drawings. Make accurate sketches of the three

surfaces of a wood block to show the wood rays,

Epidermis

.Cortex
^Phloem
y-Xylem

-Bark
-Wood ray

Innual ring
-Pith
Pruned
branch

rk bark

Cortex
•Phloem
-Xylem
-Pith

Wood ray
'Cambium

Cork bark
•Phloem
'ambium

Summer wood

•ing wood
nnual ring
rptTFood ray

FIG. 12. The structure and growth of a tree

A, diagram illustrating the gross anatomy of an oak tree in long section. Note
the relation of the annual rings, the junction of the branches •with, the main trunk,
and the covering of pruned branches ; B, transverse sections of the tree shown in
A, at three levels. The figures in B are designed to illustrate the early, or pri-
mary, structure (a) and the secondary changes (b, c).

BIOLOGY OF HIGHER SEED PLANTS 45

annual rings, and spring and summer wood as
they appear in transverse, longitudinal, radial, and
tangential sections. Indicate ducts by circles,
summer wood by shading. Label these structures
in each view of the block drawn.

PRACTICAL EXERCISE

Study the various cuts of finished woods represented in the
finished woods in the tables, doors, and other wood furnishings
in the laboratory. See Figs. 48 and 50 of the text and the discus-
sions concerning the structure of finished woods.

1. Determine the different cuts of wood, namely, the radial,

tangential, and transverse cuts, represented in the finished
woods of the laboratory.

2. Determine annual rings, heartwood and sapwood, u grain,"

"silver grain," etc. in each of the above cuts.

3. Make sketches of the above structures in transverse, radial,

and tangential sections of different kinds of finished
woods. Label all structures indicated in your drawings.

MICROSCOPIC STRUCTURE OF WOODY STEMS
TRANSVERSE SECTIONS

Observe transverse sections of shoots which are more than
one year old. Use only hand lens and low power in your first
studies. In preparations which have been stained with a red
dye (safranine) the wood and the thick-walled skeletal tissues
are stained red. The remaining tissues are usually stained purple
or blue with logwood dye (heematoxylin).

1. General tissue layers in sections of living shoots.

a. The bark. Note the limits of the layers designated as
brown bark and green bark in sections of fresh twigs.
Can you distinguish the epidermis and the brown

LABORATORY AND FIELD EXERCISES

cork layer? How many tissue layers of different
appearance are there between the outer cork layer
and the outer limits of the wood ? Observe the cells
of these different layers with a low power and note
the general character of each. Consult the text and

-PUh

FIG. 13. Healing of a wound due to the severance of a branch

The healing is done hy new tissue, called callus, formed over the wound. Ohservo

the irregularity of the annual rings around the wound. Redrawn from Curtis's

" Nature and Development of Plants "

Fig. 46 for a discussion of these tissue layers belong-
ing to the bark. See also Fig. 52 of the text.
b. The wood. Note the following main tissues and struc-
tures of the wood :

(1) Note the number and relative cell width of the annual
rings of growth; the distinction between spring
and fall wood ; the wood rays. The relative length
and termination of the wood rays can now be
accurately traced. Do they extend through the
phloem ?

BIOLOGY OF HIGHER SEED PLANTS 47

(2) The pith. Note the irregularly lobed pith in some
kinds of wood. The irregularity of the pith is due
to the effect of branches and leaves on the form
of the pith.

c. Draw a sector of the section, indicating by shading and
by circles the different layers of the bark and wood.
The sector should be three or four inches from epi-
dermis to pith and two inches wide. Draw each tissue
layer accurately as regards its relative width and
extent, but do not draw cells. The spring ducts may
be indicated by circles and the summer wood by
shading.
2. Cellular structure of the tissues. (Use prepared slides.)

a. The cork (brown baric). Study the character of the

cork cells and compare them with the cork cells
studied earlier in the course. Is the epidermis still
present or has it been sloughed off after the formation
of cork ?

b. The cortex. Note its limits and the nature of its cells.

Do its cells contain protoplasm and chloroplasts ? Are
there intercellular spaces ?

c. The phloem. See Fig. 52 of the text.

(1) Outer phloem layer. Study carefully the cell walls

and the contents of the strengthening, or skeletal,
layer of the phloem (stained red with safranine).
Can you find cells with canal-like perforations of
the greatly thickened cell walls of these cells ?

(2) Inner phloem layer. Note the nature of its cells and

their gradual merging into the cambium (see
next topic).

(3) Cambium. The cambium is composed of three or

four cell layers adjoining the red stained wood
on its inner side and the phloem on its outer

48 LABORATORY AND FIELD EXERCISES

border. Determine accurately the structure of
these cambium cells. Note the orderly arrange-
ment of the tissues of the xylem and phloem
which arise from the cambium. Why is this so ?
Do the wood rays arise similarly from the cam-
bium ? Are the rays continuous from the time of
their origin to old age in a tree? Be able to
explain this point.

d. The wood. Study carefully the following cells and
tissues of the wood :

(1) Water ducts. Their size, contents, and cell-wall

thickenings. Why are they so much larger than
the surrounding cells ?

(2) Wood fibers. Are they thick-walled or thin- walled ?

Have they cell contents ? What is their function
in a living tree trunk ? Are they structurally
adapted to their function ?

(3) Annual rings. Study the relation of ducts and

fibers at the junction of two annual rings. Is the
boundary line between spring and summer wood
a sharp one ? Why is the annual ring so plainly
visible in stumps or sawn logs ?

(4) Wood rays. Observe their cell structure carefully

and compare it with that of the surrounding dead
ducts and fibers of the wood. Do you find pores
in the end walls of these cells and protoplasmic
continuity through these pores ? This can be seen
only in very thin and well-stained preparations.
What is the function of wood rays ?

(5) Wood parenchyma. Observe the amount and dis-

tribution of living cells with darkly stained con-
tents in the wood outside of the rays. Are these
cells in isolated or in connected masses ? Are

BIOLOGY OF HIGHER SEED PLANTS 49

they connected with the wood rays ? with the
ducts ? Do they have cytoplasmic and nuclear
contents ? What is the function of these cells ?
(6) Drawings.

(a) Draw a small portion of the summer and spring
wood at the junction of the two in an annual
ring. Show the details of ducts and fibers.
(&) Draw the cambium and a portion of the phloem
and xylem on either side of it, including at
least two wood rays. Indicate the, orderly
arrangement of the tissues which arise from
the cambium. Draw the cells and tissues with
great accuracy.

LONGITUDINAL SECTIONS

Study thin longitudinal sections of the wood of oak, birch,
or a similar woody stem. See Fig. 53 of the text.

1. Select a portion of your section in which you can demon-

strate most clearly the following main wood tissues in
long section : namely, ducts, fibers, living cells, and
wood rays.

2. Study and draw accurately the above tissues of the wood

in long section. Indicate in each tissue the relative
thickness and cell- wall markings, the nature of the cell
contents if present, and the shape of the cells com-
posing the tissue.

3. Observe the form and structure of the cambium cells and

the phloem cells, consulting the text figure. These
tissues are usually too difficult for accurate delineation
by beginning students.

50 LABORATORY AND FIELD EXERCISES

HERBACEOUS STEMS
DICOTYLEDONS

Study the main layers of herbaceous stems in transverse
section, contrasting them with similar layers of the woody
stems studied above.

1. Epidermis. Is the epidermis present ? What is the color

of herbaceous ste'ms ? Are they smooth or rough ?
Compare the external features of woody and herba-
ceous stems.

2. Bark. What are the layers of the bark (using the term bark

to include all tissues from the epidermis to the cam-
bium) ? Contrast these tissue layers with those of woody
stems just studied. What is the function of green bark ?

3. The wood cylinder. How does it differ from that found

in woody stems ? Is it an unbroken cylinder ? Is

it as thick as that of woody stems ? Are there annual

rings ? How do you explain your findings on this

point ? Stain your section with iodine and observe again

the tissues of the wood cylinder. Note the following :

a. Dead tissues and cells. Do these appear to be similar

to those of a woody-stemmed plant ? If they are

different, be prepared to explain how and why. Why

can an herbaceous plant get along with a smaller

amount of wood tissue than a tree or a shrub ?

1>. Living tissues of the wood. How are these distributed

in herbaceous stems ? Compare with the distribution

of similar tissues in woody stems. Compare the

amount of living storage tissues in herbaceous and

woody stems.

c. Pith. Note the relative size of the pith in herba-
ceous as compared with woody stems. Is there a

BIOLOGY OF HIGHER SEED PLANTS

51

difference be-
tween the two
stem types in
this respect ?
4. Drawing. Draw
a sector of
an herbaceous
stem in out-
line, to show
the real posi-
tion and rela-
tive width of
the main tissue
layers of the
bark, the wood,
and the pith.
Label each of
these layers,
using terms
corresponding
to those pre-
viously used in
the study of
woody stems.
Point out the
main contrast-
ing points be-
tween woody
stems and her-
baceous stems.
Consult the
summary in the
text (p. 108).

FIG. 14. • Transverse (A) and longitudinal (B)

sections of the stem of the sunflower (Helian-

thus annuus)

A : e, epidermis ; col, collenchyma of the cortex ;
p, parenchyma of the cortex ; b, fibrous phloem ;
s, sieve portion of phloem : c, cambium ; fv, ducts
of the xylem portion of the fibrovascular bundles.
B : f, fibers of the xylem ; t, dotted duct ; (,' scalar-
iform duct ; pa, wood parenchyma ; t", reticulated
ducts ; s, spiral ducts ; p, thin-walled cells of the
pith. After Miiller

LABORATORY AND FIELD EXERCISES

5. Summary of herbaceous stem structure. Summarize the
distinctive characteristics of herbaceous as compared
with woody stems, in terms of bark, cortex, vascular
cylinder, and pith.

MONOCOTYLEDONS

Study transverse sections of stems
of monocotyledons. Contrast their
structure with that of herbaceous
dicotyledons.

1. Is there a distinct bark in the

stem of the monocotyledon
that you are examining ?
a distinct wood ring and
pith ? Do you find xylem
and water ducts ? Is there
phloem connected with the
xylem ? What form is as-
sumed by the masses of
xylem and phloem, and how
are these masses (vascu-
lar bundles) distributed in
the stem ? Where is the
strengthening skeletal tis-
sue in a monocotyledonous
stem ? the storage tissue ?

2. Drawing. Be able to construct a drawing of a stem of

a monocotyledon to bring out the contrasts between
its structure and that of the stems of herbaceous
dicotyledons examined above.

3. Summarize the differences between the stems of herba-

ceous dicotyledons and monocotyledons.

FIG. 15. Structure of a root in
transverse section

e, epidermis ; c, outer layer of

the cortex (cort) ; x, xylem, and

p, phloem, arranged radially.

After Bonnier and Sablun

BIOLOGY OF HIGHER SEED PLANTS 53

B. STRUCTURE OF ROOTS

Study transverse sections of large and small roots and com-
pare their structure with that of herbaceous and woody stems
of dicotyledons.

1. Bark. Do roots possess a definite bark ? Has the bark

(including tissues between epidermis and cambium) the
same general layers as in stems ? Are these layers simi-
lar in arrangement and structure in stems and roots ?

2. Xylem and pith. Are these two regions the same in roots

and stems ? Compare young and old roots in this respect.

a. Dead tissues of the xylem. Do you find ducts and

fibrous cells ? How are they arranged in roots ? Are
there annual rings ?

b. Living tissues of roots. Are these more or less abundant

in roots than in stems? Stain fresh root sections
with iodine to demonstrate this point.

3. Cambium and phloem. Are these tissue layers present

in the root section that you are studying ? Are they
as evident as in stem sections ?

4. Drawing. Construct a drawing of a root in transverse

section (no cells), to illustrate root structure. Label the
tissue layers correctly.

5. Summary. Summarize the distinctive features of root

structure as compared with that of herbaceous stems.

C. THE STRUCTURE OF THE LEAF

For the preliminary study of the structure of a leaf use thick
leaves of Narcissus or onion, which are easily sectioned in a
fresh state.

1. Epidermis. Peel or strip the epidermis from a leaf of the
onion or Narcissus. Mount in water or dilute alcohol
and study its cellular structure.

54

LABORATORY AND FIELD EXEECISES

a. Low-power study. Are all the cells of the epidermis

alike in structure and form ? Do they have chloro-
plastids as a part of the cell contents ? Do they differ
in this respect ?

b. A high-power study.

Study the color-
less and the green
cells of the epi-
dermis very care-
fully with a high
power. Note the
shape and struc-
ture of each kind
of cell. How many
green cells are
grouped together ?
Are they separated
by a solid wall or

is there a pore _,

IIG. lo. Transverse section of a leaf

e, elt upper and lower epidermis with
thick outer wall (c) and stomate (st) ; p,
palisade cell layer with intercellular space
(o) below the stomate; sp, spongy pa-
renchyma with intercellular spaces (i) ;
ph, phloem ; x, xylem of a vein in section.
After Prantl

between them ?
c. Drawing. Draw a few
cells of the epider-
mis of the leaf ac-
curately, indicating
the detailed struc-
ture of thestomataand the surrounding epidermal cells.
2. Leaf sections of a fresh leaf. Study transverse sections of
leaves cut from fresh material. Locate the main tissue
layers of the leaf in such sections and note their gen-
eral character. Use low power and dissecting lenses
in the study of these thick sections. Is the green
tissue favorably placed for receiving light rays? Do
you find the veins and the epidermis ?

BIOLOGY OF HIGHER SEED PLANTS

55

a. Make a general drawing, omitting the cells, to show the

position of the epidermis, green mesophyll, and veins

of the section

which is under

observation.
I. Epidermis.

(1) Note its color,

thickness, and
extent as a
covering of the
leaf surface.
What is the
real form of
the en tire epi-
dermal layer
of the leaf
you are study-
ing ? Do you
find stomata?
Stomata may
frequently be

recognized as FIG. 17. Conducting cells (tracheids) of the
darker places veins of a leaf

in flio frocVi «u> midvein: 6, lateral veins ; e, termination of

111 lilt? 1 1 Coll ,, -,, .

veins ; me, areas occupied by mesophyll cells in
epidermis. De- the living leaf. After Sachs

tails of the

guard cells cannot be seen in such thick sections.

(2) What special structural feature of the epidermal

cells insures against the loss of water? Would
the same structural feature serve other protective
functions ? Search for sections of the guard cells
and of the pores of stomata. Determine the pecul-
iar cell character of the guard cells, — for example,

56 LABORATORY AND FIELD EXERCISES

the relative thickness of the cell walls as well as
the size aud the living contents of the guard cells.

c. Mesophyll.

(1) Note the character of a mesophyll cell as regards
cell wall and cell contents. Does each meso-
phyll cell come in contact with an intercellular
space ? What would be the advantage of such
an arrangement ? What is your conception of
the intercellular system of a leaf ? Is it a con-
tinuous aerating system or are the spaces seen
in a transverse section isolated spaces ? Do you
find any intercellular spaces immediately above
the stomata?

d. Veins. Study the structure of the veins. By what

kind of tissue are the ducts surrounded ? Is there
a phloem like that connected with the xylem of
stems ? What is the double function of the veins in
a leaf ?

e. The skeletal tissue. Study its distribution and the char-

acter of its cells.

/. Drawing. Construct an accurate drawing of a small
portion of your section so as to include a large vein.
Detail the tissues of the epidermis, mesophyll, veins,
and skeletal structures.

SECTION IV. PHYSIOLOGY OF PLANTS

INDIVIDUAL AND CLASS EXPERIMENTS

Two classes of experiments are outlined below : namely,
individual experiments, which are to be performed by each
member of the class, and demonstration, or class, experiments,
which are set up by -an instructor, or by some member of the
class, for observation by all members of the class. Both kinds
of experiments should be written up and handed in as a part
of the regular laboratory requirement. Unless otherwise stipu-
lated, all experiments should be written up in the following
order :

RECORDING OF EXPERIMENTS

1. Object of the experiment. State concisely the object of

the experiment.

2. Method. State the method used in the experiment, drawing

apparatus when necessary to make the method clear.

3. Actual results secured. State concisely the actual results

secured. Do not include theories and conclusions.

4. Conclusions. What does the experiment seem to you to

prove ?

A. PHOTOSYNTHESIS

1. The presence of starch in leaves of Pelargonium or a sim-
ilar plant with white areas. Individual experiment.
a. Compare fresh leaves of Pelargonium with leaves which
have been previously boiled and treated with alcohol.
Give the reason for the difference in color. Be able
to explain to an instructor.
57

58 LABORATORY AND FIELD EXERCISES

b. Place a bleached and a fresh leaf in separate watch

glasses and flood with iodine solution. After a half
hour rinse the two leaves in water and place in watch
glasses of water for observation. Test some starch
with iodine in a watch glass. Compare the starch
reaction with that of the leaf. Is starch present in
Pelargonium leaves ? If so, where is it located and
where did it originate ? How and when is the starch in
a leaf used ? Have you had any clue to the answer
to this question in your work with woody stems ?

c. Record the object, method, and results of, and the con-

clusions to be drawn from, the above experiments,
as indicated above under Recording of Experiments.
Include in the results a drawing of the bleached
leaf, showing the distribution of starch.

2. Test as above leaves of young growing corn or bean plants

about six inches high. Individual experiment.
a. Use two plants which have been in the dark overnight
or for at least six hours. Why is this precaution
necessary ?

' b. Expose one plant to bright sunlight for an hour or
more and leave another in darkness. Remove a leaf
from each plant, boil, extract chlorophyll with warm
80 per cent alcohol, and test for starch.

c. Results ? Do the two leaves show a different reaction

to iodine? If so, be able to state why. What im-
portant conclusions are to be drawn from this
experiment ?

d. Record your results and conclusion as prescribed above.

3. Gaseous exchanges in water plants during photosynthesis.

Class demonstration.

a. Observe plants of Elodt><t (water weed) which are ex-
posed under water to bright sunlight. Are bubbles

BIOLOGY OF HIGHER SEED PLANTS 59

of gas given off ? Shade the plant. Do the gas
bubbles continue ? Explain, Record the experiment
by the usual method.

b. Can you suggest a method for testing the gas given off

by Elodea and other water plants when exposed to
sunlight ? If so, perform the experiment as you have
planned it.

c. Record object, results, and conclusions in the usual

manner.
4. Gaseous exchanges in land plants.

a. Place three tubulated bell jars in three large plates or

pans which will hold water. Narrow-necked bottles
(Wolff-neck bottles are good) may be used instead of
bell jars. Place in two of the bell jars, or bottles if
these are used, vigorous leafy shoots of plants. If bell
jars are used, pour water into the plates or pans until
it rises an inch or more in each jar.

b. Lower into each jar or bottle a lighted candle, and cork

tightly with a rubber cork or a vaselined common
cork. How long does the air in the jars support com-
bustion ? Why do the candles go out ? How does the
burning of the candles change the composition of the
air in the jars ? Record answers to points (1) and (2)
under d.

c. Put all of the above jars in sunlight and cover one con-

taining a leafy plant so as to exclude light. After
two or three hours lower lighted candles into each
jar and test quickly to see whether the air in them
will support combustion. Is there a difference in the
air in the jars in this respect? P>e able to explain
any differences observed.

d. Record the experiment in the usual manner. Under

Results indicate the composition of the air in the

60 LABORATORY AND FIELD EXERCISES

three jars (1) before the candles are placed in them,
(2) immediately after the candles cease to burn,
and (3) at the close of the experiment, before the
corks are removed. Explain also the daily gaseous
income and outgo of the exposed and the covered
plants in the two jars during the period of the
experiment. How and why would they differ in
this respect?

e. Considering the results of the above experiment, how
do plants affect the air of a living room by day ? at
night ? Is it healthful to have a large number of plants
in a living room? Give reasons for your conclusions
concerning this matter.

B. RESPIRATION

1. Gaseous exchange of plant parts during respiration. Indi-
vidual experiment.

a. Select two bottles or pint fruit jars with wide mouths.

Put into one bottle or jar enough dry peas or beans
to cover the bottom. In the second receptacle place
a similar amount of germinating seeds after they have
been sterilized in a weak formalin solution. Test the
air in each receptacle with a burning match to see if
it supports combustion. Cork air-tight and set aside
for twenty-four or forty-eight hours.

b. After the above period remove the corks and test the

air again with a lighted match. Result ?

c. Write up the experiment, indicating the composition of

the air in the receptacles at the beginning and
at the end of the experiment. Indicate also the gase-
ous income and outgo of the seeds in each jar during
the time of the experiment.

BIOLOGY OF HIGHER SEED PLANTS 61

d. Class experiment. Treat green leaves, stems, buds, or
flowers as indicated above for seeds. Observe and
record results and conclusions at the end of the
experiment as indicated under c. What precaution
is necessary where green plant parts are used ?

NUTRITION AND SEASONAL LIFE

1. Study the seasonal life of common plants like the potato,

corn, onion or tulip, cherry tree, and locust tree,
a. Compare the seasonal life of the annuals with that of
the bean outlined in the text; that of the biennials
with that of the white sweet clover ; that of the per-
ennials with that of the locust and the apple.

(1) What provision does each plant make for wintering ?

for spring growth ? for summer activities and
storage ? Are the same physiological functions
characteristic of all plants at the same season in
a similar habitat ? Be able to state the main
functions or activities characteristic of the plant
in winter, spring, summer, and autumn.

(2) Be able to construct drawings similar to those of

the text, indicating the structures by which plants
winter and perform the activities of the spring
and summer seasons.

(3) Summarize the dominant nutritive activities of plants

in the different seasons. See Fig. 63 of text.

C. TRANSPIRATION AND WATER ASCENT
TRANSPIRATION

1. Record the loss of water from a leafy shoot placed in a
graduate or in a potometer made from a burette. Class
experiment.

62 LABORATORY AND EIELD EXERCISES

a. Note and record temperature, general light intensity,
and relative humidity at the time of taking each
reading. Take records at convenient intervals for
about three days.

I. Write up the experiment as usual. Under Results tabu-
late your readings to show temperatures, light inten-
sity, and relative humidity, as well as the amounts
of water lost at stated periods and for the entire period.
c. Summarize the main factors which have apparently
caused variations in the rate of transpiration in your
experiment at different periods.

2. Record the loss of water by transpiration from a potted
plant, as for the previous experiment, and record results
as explained above. Class experiment.

WATER ASCENT

1. The path and rate of water ascent. Individual experiment.
Cut off leafy herbaceous shoots or stalks of celery under
water and add eosin to make a strong colored solution,
and observe as follows : •

a. Hate of water ascent. If transparent stems of Impatient
or bleached stalks of celery are vised, the progress of
the colored solution may be observed in the stem or
in the leaf veins.

(1) After from three to five minutes remove the stem

from eosin and make cross cuts of it, beginning
at the apex, until the coloration by eosin appears
in the cross section. Measure the length of the
stem traversed by the- solution during the time
it was left in eosin.

(2) From the above data determine the rate of ascent

per hour. Compare with the rates of water ascent

BIOLOGY OF HIGHER SEED PLANTS 63

given in the text. Would the eosin rise in the
stem as rapidly as pure water ? Kecord results.
b. Path of water ascent in the stem and leaves.

(1) Cut the stem lengthwise through a node and trace

the path of the eosin from the main stem into
the leaves and branches.

(2) Draw a transverse section and a long section of the

stein, indicating the tissue in which the eosin solu-
tion moved. Did it pass up the ducts or in other
tissues of the xylem and phloem ?

(3) Plot the path in the leaf veins and veinlets.

ECOLOGICAL RKLATIOX OF PLANTS TO WATER

1. Make a list of 10 mesophytes, 10 hydrophytes, 5 xero-

phytes, and 10 tropophytes from the wild and culti-
vated plants of your own region. Be able to explain the
gross structural adaptations of these plants to their
habitat.

2. Are some of the above plants apparently not adapted to

their present habitat ? If so, how do you explain this ?
Be able to give the essential characteristics of the
mesophytes, hydrophytes, xerophytes, and tropophytes
of your region.

SECTION V. REPRODUCTION

A. SEXUAL REPRODUCTION
THE FLOWER AXD ITS PARTS

Examine some large flower like that of the mandrake and
note the nature and relation of its parts.

1. How many kinds of different parts or organs are there

in the flower ? How are they arranged with reference
to each other ? Does each set of organs form a circle,
or whorl, like cyclic leaves on a stem, or are all parts
of the flower spiral, like spirally arranged leaves ? Do
any portions of the flower resemble leaves in color,
form, or venation ?

2. Remove carefully the floral parts or organs on one side

of a flower. Place the parts thus removed in a watch
glass of water for future examination. Now examine
the flower from which the parts have been removed.
a. What is the nature of the floral axis to which the floral
parts are attached ? Has it nodes and internodes ? Is
it like the axis of a branch or bud in this respect ?
5. Observe again the relative .position of the different sets
of organs of the flower. Are the members of each
set spiral or cyclic in arrangement ? What kind of
organ (or organs) terminates the floral axis ?
c. Does the flower resemble a bud in the arrangement of its
organs on the floral axis ? Does it seem to you possible
that the flower was originally derived from a short
branch or bud ? What parts of the flower are nearly
like leaves ? What parts are highly modified ?
64

BIOLOGY OF HIGHER SEED PLANTS 65

3. Draw the entire flower as it appears on the side from

which the parts have been removed. Indicate accu-
rately in the drawing the form and relative position of
the floral parts on the floral axis.

a. Study the text and Figs. 215 and 84 and name the
parts of the flower sketched above.

4. The essential organs of the flower.

a. Anthers and pollen. Observe carefully with a hand

lens and low power the dehiscence of the anther.
Does the anther sac open crosswise or lengthwise to
shed the pollen? Do you see the dustlike pollen
grains issuing from the slit, or dehiscence line, of
the anther? How many anther sacs are there in
one anther? Draw a stamen greatly magnified to
show the mode of dehiscence of the anther sac.

b. Pollen. Dust some pollen on a slide and study its

form and structure. Is the pollen grain a cell ? Is
its wall smooth or rough ? Can you see any cell
contents? Draw the pollen, exterior view, as it
appears to you in your specimen.

c. The pistil

(1) Observe the external parts of the pistil and note

their form and structure. Observe the stigma
carefully. Is it adapted to the reception and
retention of pollen ? Draw a pistil, including an
enlarged view of the stigmatic surface, and name
all its parts.

(2) Cut a transverse section of the upper and middle

portions of the ovary. Cut also a section through
the style, if one exists. How does the ovary
differ in structure at the different levels at which
you have cut it ? How is the wall of the ovary
modified in the median, or middle, section of the

66

LABORATORY AND FIELD EXERCISES

ovary ? Are there budlike outgrowths from the
enlargement of the ovary wall in your section ?
What is the shape of these buds, or enlarge-
ments? Draw the two or three sections of the
ovary which you have made. Label the parts after
you have
studied "the
text and
Fig. 220.

5. The fruit. Study
both the exter-
nal and the in-
ternal structure
of the fruit of
the mandrake
or other plant
examined. Do
you find the
same parts in
the fruit as

FIG. 18. Section of a portion of a wheat kernel

p, pericarp; t, seed coat; al, aleurnne, or ni-

trogenous layer of the endosperm ; //, nuclei ;

st, starch-storing cells of the endosperm.

After Strasburger

you did in the
pistil ? What
forms the in-
terior of the fruit ? Where are the ovules ? the placenta ?
the ovary wall? What relation has the fruit to the
pistil ? Define a fruit. Draw a sectional view of the fruit
to show all of its parts in their proper relation. Label
the parts, using the same terms as were used for similar
parts of the ovary (see text discussion and Fig. 221).
6. Supplementary studies : gametogenesis, fertilization, and

development.

a. Microscopic structure of pollen. Mount large pollen
grains taken from some liliaceous plant, like the

BIOLOGY OF HIGHER SEED PLANTS

67,

-str

tulip, Narcissus, or Easter lily. Observe them care-
fully under low and high powers of the microscope.

(1) Does the pollen cell have one or more nuclei? Do

different pollen cells differ in this respect ? Do you
see granu-
lar cytoplasm
surrounding
the nucleus
in some pol-
len cells ?

(2) Draw a pollen

cell much en-
larged. Indi-
cate the gran-
ular condition
(Fig. 85, a) of
the cytoplasm
and the rel-
ative size of
the nucleus,
or nuclei, in
the cell. La-
bel your fig-
ure correctly.
(.">) Xtmly of pollen
tubes. If pol-
len tubes are

available, study the structure and method of
formation of pollen tubes. Draw a pollen cell
and its pollen tube. Note and draw the structure
of the tube and its cytoplasmic contents. If pos-
sible observe the nuclei in the pollen tube. This
point is difficult to determine.

- - - ou int

FIG. 19. Diagram of the ovule, embryo

sac, and embryo of shepherd' s-purse

(Capselkt)

ou int, outer integument ; in int, inner in-
tegument ; susp c, suspensor cells ; e s w,
embryo-sac wall ; r r, root region ; st r, stem
region ; s I, seed leaves. From Bergen and
Caldwell's "Practical Botany "

68 LABORATORY AND FIELD EXERCISES

b. The structure of the ovule.

(1) Gross structure. Dissect out the ovule from the

ovary of some common plant into a drop of
water on a slide. Mount and observe the essen-
tial parts of the ovule ; namely, the f uniculus, or
stalk, the body of the ovule, and the micropyle.
Ovules of the shepherd's-purse (Capselld), when
treated with a weak solution of potash, will often
show the outline of the embryo sac within the
ovule. Draw one or more ovules to show the
structure observed. Label.

(2) Microscopic structure of the ovule. If material is

available, study thin sections cut through the
ovule to show the embryo sac and micropyle ;
for example, in shepherd's-purse or mandrake.

(a) Determine the structure and thickness of the
seed coats. Do you see the micropyle of the
ovule ? What is the nature of the large cen-
tral light space of the ovule ? Is there a
nucleus in this space? Are there vacuoles
and cytoplasm ? Has this central space the
structures of a cell ?

(1} Study the structure and position of the embryo.

(c) Draw the sectional view of the ovule, indicating
the micropyle, the cellular structure of the
ovule coats, and the form and structure of
the embryo sac and embryo.

POLLINATION IN PAPILIONACEOUS FLOWERS

1. Inflorescence, or flower cluster. Examine an inflorescence

of some plant belonging to the pea family.
a. Parts of the inflorescence. Has the inflorescence axis
the same parts as the stem axis below it; namely,

BIOLOGY OF HIGHER SEED PLANTS 69

nodes and internodes ? Where do the flowers origi-
nate on the axis ? Is there any structure below the
flower stalk corresponding to a leaf ? To what part
of an ordinary leafy shoot would a flower on the
inflorescence axis correspond most nearly,- — to a leaf
a bud, or a branch ? On what evidence do you base
your conclusions ? See Fig. 212 of the text.
b. The inflorescence and pollination. Are the open flowers
at the apex or at the base of the inflorescence ? Is
the inflorescence an advantageous arrangement for
securing cross-pollination, or the transfer of pollen
from the anther of one flower to the stigma of
another flower, by insects ? Compare an inflores-
cence with solitary flowers in this respect. Sketch
an inflorescence and a portion of the stern below it.
Name the parts correctly.

STRUCTURE OF PAPILIONACEOUS FLOWERS

STRUCTURE OF THE FLOWER

Examine flowers of some member of the pea family and com-
pare their structure with that of a simple flower like that of
the mandrake.

1. Perianth. How many whorls, or sets, of organs in the

perianth ? Are the members of each whorl regular or
irregular in form ? How many parts in each whorl ?
Are the parts of each whorl united or separate ? Remove
the parts of the perianth and place them in their proper
order on the table. Sketch the parts of the corolla.

2. Essential organs. How many stamens are there ? Are

they separate or united?. How are the stamens related
to the pistil ? Study the form and external features of
the ovary, style, and stigma. Study the style and stigma

70 LABORATORY AND FIELD EXERCISES

with a hand lens. What is the nature of the stigniatic
and stylar surfaces ? Are they smooth or rough ?
3. Remove the perianth from one side of a flower so as to
expose the essential organs in their natural position.

a. Sketch the essential organs accurately and indicate in

outline the relation of the perianth to these organs.

b. Make an accurate drawing of the pistil, indicating the

position of the placenta and ovules and the peculiar
structure of the stigma and style. What advantages
are there for pollination in the structural relations
of the style and stigma ? Label all of the above
figures accurately. See Fig. 89 of the text.

CROSS-POLLINATION

Select a flower of some member of the pea family for the
following experimental study of cross-pollination :

1. Press down the keel petals with the point of a pencil or

with a dissecting needle. Eesult ? Where would an in-
sect need to alight in order to imitate the above action
of the keel, stamens, and pistil ? If an insect should
visit a series of flowers like the one experimented upon,
would cross-pollination be secured ? Be able to explain.

2. Read the account in the text (p. 170) on cross-pollination

in the common locust (Robinia pseudo-acacia).

a. Does the flower upon which you experimented possess

the contrivances of the locust flower for securing
cross-pollination ? If not, in what respect does it differ
from the locust ?

b. Construct a drawing to show the relation of the anthers

to the stigma and of both anthers and stigma to the
keel, when the latter is depressed. Compare the figure
with your first figure of the flower with one half of the
corolla removed.

BIOLOGY OF HIGHER SEED PLANTS 71

3. The fruit and seed in members of the pea family.

a. Examine the fruit of the pea, beau, locust, or some

other member of the pea family. Compare this fruit
with that of the pistil already studied. Note the
corresponding parts of fruit and ovary. Be able to
define a fruit in terms of the pistil.

b. Remove one half of the wall (carpel) of the fruit and

observe the form and attachment of the seeds to the
placenta. Sketch the inner view of the fruit or pod
with the seeds. Label the parts of your sketch accu-
rately, including the parts of the seeds. Use the same
terms as those used for the pistil and ovules.

4. Examine seeds of beans or of the locust. How has the

ovule changed to form the seed ? What advantages are
there in the changes ? Do you find the scar on the seed
caused by the breaking off of the funiculus ? Do you
find other marks near this latter scar ? Draw an exte-
rior view of the seed on the side of the hilum, or scar,
caused by the removal of the funiculus. Label accurately.

5. Cut thin sections from the cut surface of the cotyledon of

a bean. Stain with iodine. Result ? What is the func-
tion of the cotyledons ? What kind of reserve food is
most prominent as revealed with iodine ? Draw a portion,
of the section (Fig. IS).

SUPPLEMENTARY STUDY

Study some assigned flower or flowers with reference to devices
for securing cross-pollination. Construct drawings to indicate the
particular devices for pollination in the flower or flowers examined.

PART II. THE PLANT GROUPS

SECTION VI. THALLOPHYTES (ALG^ AND
FUNGI)

A. THE ALGJE
PROTOCOCCUS (PLEUROCOCCUS)

1. Habit and Habitat. Note the appearance of Protococcus

on bark, boards, or stones. Has the green incrustation
any definite form or structure comparable to that of
the higher green plants ? Do you see any evidence of
roots, stem, or leaves ? Do you know whether Proto-
coccus ever lives in water, like the other fresh-water
algse ? Is Protococcus on bark or stones xerophytic or
mesophytic in habit and habitat ?

2. Structure. Scrape off a little of the green incrustation

formed by Protococcus in a drop of water on the
center of a glass slide. Be careful not to remove
pieces of bark or dirt with the plants. Cover and
press out gently under the cover glass with a dissect-
ing needle. Examine with the low power of a com-
pound microscope.

a. What is the nature of the green masses observed under

a low power ? Are they composed of cells ? Do you
find any single green cells ? What constitutes a
Protococcus plant ? Is it unicellular or multicellular ?
Do you find chloroplasts, cell wall, etc. ?

b. Sketch two or three green masses to show their struc-

ture as you observe them. Label the parts in terms
of cells and cell structures.

75

76 LABORATORY AND FIELD EXERCISES

3. Reproduction. Study the method of reproduction outlined

and illustrated (Fig. 115) for Protococcus in the text.

a. Observe three or four stages in reproduction from your

mounts of Protococcus. Is this a vegetative or a
sexual method of reproduction ? Is it a rapid or a
slow method ? What becomes of the loose colonies
formed by reproduction when the plants are exposed
on bark, boards, or stones ?

b. Sketch three or four stages in the reproduction of Pro-

tococcus, beginning with a single-celled plant.

4. Dissemination. How does Protococcus spread from tree

to tree or from any one habitat to another ? How does
it form a large incrustation from the first few cells in
a new habitat ? Why does it usually occur on the
north side of trees and fences ? Why is it more abun-
dant on rough than 011 smooth surfaces ?

5. Nutrition. What is the source of the water, gases, and

salts which constitute the raw food materials for Pro-
tococcus plants ? How are these materials absorbed ?
Are they made into foods and used by Protococcus as
they are in a tree or a geranium plant? Be able to
indicate the income and outgo of food materials and
wastes in Protococcus plants.

6. Summary and discussion. Discuss briefly in your notes

the mam points indicated above concerning the struc-
ture, reproduction, dissemination, and nutrition of
Protococcus.

CHLA MYDOMONA S

If Chlamydomonas is available for study, compare it with
Protococcus in structure, reproduction, and dissemination. Note
particularly the rate and mode of movements in active Clilamy-
domonas plants. The brick-red eyespot and the cup-shaped
chloroplast may be observed in forms which have come to rest.

THE PLANT GROUPS 77

SPIROGYRA (WATER SILK)

1. Habitat and habit. Observe plants of the common green

scum floating in an aquarium or on ponds in the open.
Eemove a small portion of the green mass to a watch
glass. Separate somewhat and examine with a hand
lens and the low power of a compound microscope.

a. Is the green mass composed of one plant or many ?

What is the nature of the Spirogyra plant ? Has it
roots, stems, or leaves? How does it differ from
plants of Protococcus ?

b. Sketch one or two Spirogyra plants as seen under a

low power. Name all structures observed.

2. Cell structure. Study the cells of a Spirogyra plant under

high power. Are the cells composing the plant all alike
or are they differentiated for different functions ? Note
the bandlike chloroplasts. How many are there in each
cell?
a. Chloroplast and pyrenoids. Compare fresh and stained

plants of Spirogyra in the study of the pyrenoids.

Read the text concerning the structure and function

of the pyrenoids.

(1) Stain fresh plants with iodine solution after they

have been exposed to sunlight. Does the starch
sheath of the pyrenoid contain starch ? In what
part of the pyrenoid is the starch stored ?

(2) Compare your specimen with a Spirogyra plant

which has been specially stained and mounted
for study. Such preparations often show the
pyrenoids and nucleus with great distinctness.

(3) Sketch a portion of a chloroplast and two or more

pyrenoids greatly magnified. Indicate the starch
sheath and central granule of the pyrenoid and
the form and structure of the chloroplast.

78 LABORATORY AND FIELD EXERCISES

b. The nucleus. Study the nucleus in stained material.
What is the form of the nucleus and where is it
located in the cell ? Is it connected with the pyre-
noids ? Study several cells with reference to these
points. Draw a Spirogyra cell to show the nucleus
in its proper position and in its connections with
the pyreuoids. Construct a transverse section of a
Spirogyra cell cut through the nucleus. Label all
parts correctly. See Fig. 118 of the text.
3. Reproduction.

a. Conjugation of the filaments.

(1) Study early conjugating plants with a low power.

Observe the method of union of the filaments.
Do you find different stages in the formation of
protrusions from the cells and in the formation
of connecting tubes ? Observe whether the union
of the filaments affects the cytoplasm of the
uniting parent cells.

(2) Draw stages representing the union and conjugation

of the filaments in Spirogyra.

b. Formation of the gametes.

(1) Study plants in which gametes are forming. Ob-

serve as many stages in gamete formation as
possible in the material at your disposal. Do you
find male gametes forming before the female
gametes in cells united by connecting tubes ?
What is the method of gamete formation ? What
is a gametangium ? Consult the text for the
meaning of this term. How does it differ from a
gamete ? What are the structural parts of each ?

(2) Draw gametangia in which gametes are forming.

Indicate as many stages in gamete formation as
you find. Label gametangia and gametes.

THE PLANT GROUPS 79

c. Fertilization.

(1) Observe stages in which gametes are fusing to form

zygotes. What is the difference in the behav-
ior of the two gametes during fertilization ? On
what basis can one be designated as male and
the other as female ?

(2) Draw stages in fertilization as observed.

d. The zygote.

(1) Study cells in which zygotes are formed. What is
the structure of the zygote cell ? Distinguish
between pyrenoids and nuclei in the zygote cell.
Stain zygotes with iodine. What kind of reserve
food does the zygote contain ? When and for
what purpose will this food be used ? Draw
two or three zygotes to illustrate their cell
structure.

4. Life history of Spirogyra and Protococcus. Construct a
graphical life history of Spirogyra. Is it possible to
construct a similar graphical history for Protococcus ?
In what fundamental respects does the life history of
Spirogyra differ from that of Protococcus ?

VMTHERIA (GREEX FELT)

Select fruiting specimens of some species of VaucJieria for
study. Observe the following points regarding its habitat, habit,
and structure :

1. Habit. In what respect is Vaucheria peculiar in its gen-
eral structure ? Is it a simple or a branched filament ?
Is the plant body differentiated into root and shoot ?
What is its general microscopic structure ? Is it uni-
cellular or multicellular ? What kind of chloroplasts
has it?

80 LABORATORY AND FIELD EXERCISES

2. Sexual reproduction. Mount fruiting plants of Vauelieria

after teasing them apart with dissecting needles in a
drop of water. Search for reproductive branches with
a low power.

a. Female gameiangia and gametes. Search for greatly

swollen and shortened lateral branches representing
the female gametangia.

(1) Do these reproductive branches differ from the ordi-

nary branches of the plant body except in size ?
What is the nature of the protoplast and of
the embedded chloroplasts in these reproductive
branches ? Do you find a projecting beak, or ros-
trum, at one side of the reproductive branch ? It
is at this point that the cell wall of the game-
tangium breaks down and allows the male gamete
to enter the egg.

(2) In properly prepared material the nature of the

protoplast and the location of the chloroplast and
•nucleus may be seen. Observe carefully with the
high power.

b. Male gametangium. The male gametangium is usually

represented by a curved branch near the female
gametangium.

(1) Note the nature of the protoplast of the male

gametangium. Contrast it with that of the
female. Male gametes cannot usually be found
in VaucJieria. If they have been expelled, the
gametangium looks light-colored and empty.

(2) Draw a portion of a plant bearing male and female

gametangia. Detail the female gametes.

3. Vegetative and asexual reproduction. Vegetative reproduc-

tion occurs in Vauclieria by means of nonmotile repro-
ductive branches which are merely swollen, club-shaped

THE PLANT GROUPS 81

lateral branches, bright green in color. Motile, free-
swimmiug spores or zoospores are also formed in some
species as asexual bodies.

a. Vegetative reproduction. Search for the club-shaped

branches with a low power. How are they formed ?
How do they become free from the mother plant?
How would they grow into a new Vaucheria plant ?
Do you find free productive branches in your material?

b. Asexual reproduction by zoospores. These are difficult

to demonstrate in Vaucheria except in unusually
favorable material. Draw any stages of asexual repro-
duction which you have succeeded in demonstrating.
4. Life history. Write a graphical life history of Vaucheria
similar to that constructed for Spirogyra. In what
respect are the two life histories similar ? In what re-
spects different ? Which alga has the higher type of
reproductive process ? Explain. What is the function
of vegetative and asexual reproduction as contrasted
with sexual reproduction in a plant like Vaucheria ?

(EDOGONIUM

Habit. Study plants of (Edogonium and compare them
with ftpirogyra and Vaucheria as regards form and
structure. How do the cells differ in form and contents
from the other algte studied ? Draw a plant of (Edo-
gonium to illustrate its habit and cell structure.
Reproduction. Study plants in which the gametes are

forming.

a. Female gametangia and gametes. Observe one or two
stages in the formation of female gametes from single
cells of the filament as described in the text. How
is the female gamete formed ? What is its structure ?

82 LABORATORY AND FIELD EXERCISES

Sketch one or two stages in the formation of female
gametes. Label accurately.

b. Male gametangia and gametes. If material is available,

study the male gametangia and gametes as described
and figured in the text. Sketch stages demonstrated,
and label.

c. The zygote. Study the zygote of (Edogonium. Is it

adapted, by its cell structure, for carrying the plant
over an inclement period ? Note its form and con-
tents. Draw.

d. Asexual reproduction. The asexual reproductive process

is difficult to demonstrate with beginning classes and
should be studied from the text and figures.

e. Life history. Write a graphical life history of (Edogo-

nium similar to that outlined for Spirogyra. How is
this history adapted to seasonal changes ?

GENERAL STUDY OF FRESH-WATER ALG.E

1. Examine water containing free-floating algae, or algse

attached to objects covered by water. If algse are
scraped from surfaces, they should usually be separated
on the slide with needles or by gently tapping the
cover glass with needles. Mount in fresh water and
examine first with low power.

2. Form and structure. Note the number and kinds of algte

living together in one place. How many distinct kinds
or species of algre can you distinguish in the water you
are examining ? Are there unicellular forms ? many-
celled forms ? Have any species the power of movement?
Note differences in the form or color of the chloroplasts
in different species.

3. Reproduction. Are any of the species that you are ex-

amining reproducing either vegetatively, asexually, or

THE PLANT GKOUPS 83

sexually ? If so, trace out the stages of reproduction
found in your material.

4. Sketch the different species of algse observed and show
stages in reproduction where such are observed.

FUCUS VESICULOSUS (MARINE ALGA)

1. Habitat and habit.

a. Is the water habitat of Fucus more or less stable and
permanent than that of fresh-water algse ? Do you
know of fresh-water forms which attain to the size
or the structural differentiation of Fucus ? Is there
a reason, based on difference of habitat, for this
difference in habit between Fucus and fresh-water
species ? Note the differentiation of the plant body into
root and shoot portions. What is the function of the
root and shoot? How is each part adapted to its
special function ? How is it adapted to photosyn-
thesis ? to resistance to waves and water currents ? to
protection from dessication, or drying, when exposed
at low tide ?

I. Study the form and branching of Fucus. Can you de-
termine how the very regular mode of branching
occurs ? Where are the growing points ? Is there any-
thing like a bud ? Observe the swollen floats which
buoy the plant up in water.

c. Sketch a portion of a Fucus plant to show its habit and
mode of branching.

2. Microscopic structure. Examine thin sections cut across

a FufMS plant. What is its general structure ? Is there
an outer protective epidermis ? Where is the chlorophyll
layer or layers? Does the chlorophyll-bearing layer
look green? Explain the color of this layer. What
kind of tissue occupies the center of the branch as

84 LABORATORY AND FIELD EXERCISES

shown in the section ? Is Fucus composed of a true
cellular tissue like a geranium ? Make an outline
drawing of the section, shading in the chlorophyll-
bearing layer. Detail a few cells of each layer to
show the cellular structure.
3. Reproduction.

a. Reproductive branches. Eead the text description of

reproduction in Fucus.

(1) How are the reproductive branches distinguishable

from the ordinary vegetative branch tips ? Find
the male reproductive branches, covered with a
yellow exudation of slime containing the male
gametes. Learn to recognize the female branches
by the greenish exudation of slime containing
female gametangia.

(2) Ostia, or pores. Observe ostia with a hand lens on

the surface of the reproductive branches or with
a low power in thin horizontal surface sections of
reproductive branches.

b. Crametes and gametangia (living material).

(1) Male gametangia and gametes. Touch the surface

of a slide with male branches which are exuding
yellow slime. Mount and observe the saclike
male gametangia containing male gametes, which
look like yellow dots. Look for male gametes
free from the gametangia on the slide. Can you
distinguish the movement of these male gametes ?
their form and structure ? A brick-red spot, " the
eyespot," is usually visible.

(2) Draw male gametangia and gametes somewhat

magnified.

(3) Female gametangia and gametes. These may be

obtained as in the case of the male gametes. Note

THE PLANT GROUPS 85

the saclike gametangia inclosing from four to six
visible divisions of the contained protoplast. These
are the future gametes. Search for other speci-
mens in which eight eggs, or female gametes, are
rounded up inside of the gametangium membrane.
Find also free eggs which have been liberated, as
they are in nature, from the gametangium. What
is the structure of the female gamete ? How does
it compare in size with the male gamete ? Is the
female gamete motile ? What advantage is there
in the small male gametes and the large female
gamete ? Draw a gametangium containing devel-
oping gametes and a free female gamete.

c. Fertilization. The swarming of gametes around the

eggs may often be observed if the two gametes are
mounted together in sea water. The act of fertiliza-
tion is too difficult for observation by the beginner.

d. Female gametangia and gametes. Observe prepared

sections cut through female receptacles and stained.
Note the flask-shaped receptacles from the wTalls of
which the oogonia and paraphyses grow out into the
cavity of the conceptacle. Study different stages in
the formation of the female gametangia and gametes.
Do you find small gametangia with a single nucleus
and cytoplasm ? Search for other stages in which
there are many nuclei. Find stages in which cell
walls have been formed separating the cytoplasm of
the oogonium into eight gametes. Draw the stages
of the gametangium observed, illustrating different
stages in the formation of gametes.

e. Male gametangia and gametes. Observe sections cut

through male reproductive branches of Fucm. Are
the gametes visible within the gametangia ? How do

I LABORATORY AND FIELD EXERCISES

they compare in number and size with the female
gametes ? Were the male gametes formed like the
females, by cell and nuclear division ? Draw.
/. Life history. Write a graphical life history of Fucus
similar to that of tipirogyra and Vaucheria.

B. THE FUNGI
YEAST

1. Composition of compressed yeast.

a. Method. Remove a small portion of compressed yeast

to a slide and mount in a drop of water, separating
well with needles. Add weak iodine solution and
observe with low and high powers of the microscope.

b. Observation. Do you find indications of the presence of

starch in yeast cakes ? Can you distinguish the minute
yeast plants looking like dots under low power ? Ex-
amine these structures with a high power. What is the
structure of a yeast plant ? Contrast it with an alga
like Protococcus. In what respects are the two plants
similar ? In what respects are they different ? Why
is the yeast cake not made up from pure yeast plants ?

c. Make a drawing to indicate the composition of com-

pressed yeast.

2. Cellular structure.

a. Method. Cultivate yeast by adding about 1 g. of com-
pressed yeast cake to 15 cc. of a sugar solution made
up as follows : to 1 0 0 cc. of water add 2 0 cc. of com m on
molasses, or make up a 10-15 per cent sugar solution
in water. Keep the sugar solution at about 25°-28° C.
after adding the yeast in the above proportions. After
vigorous growth and fermentation have begun, add a
drop of the solution to a glass slide and cover.

THE PLAisT GKOUPS

87

b. Structure of the growing yeast plant.

(1) Study a mount of the above yeast solution with low
and with high powers of the microscope. Is the
yeast plant unicellular or is it composed of more
than one cell ? Are all the yeast plants on the
slide the same in size and in cellular structure ?

0 | & 6

0

FIG. 20. Various kinds of wine and beer yeasts

o, fo, wine yeast (S. ellipsoideus) (a, young and vigorous; b, old (1) and dead (2)) ;
c, d, beer yeast (S. cerevisise) (c, bottom yeast; d, top yeast). After Marshall

(2) Select a large unicellular plant and observe its

minute structure. Is the yeast cell like a root-
tip cell ? How does it differ from the cell of an
alga like Protococcus ? What fundamental nutri-
tive process, performed by Protococcus, is impos-
sible for yeast plants ? Draw and name the parts
of a large yeast cell.

(3) How do the small yeast cells differ from the large

cells in structure ? Draw a small yeast cell and
compare with the large cell drawn above.

! LABORATORY AND FIELD EXERCISES

3. Reproduction by budding.

a. Do you find yeast plants with two cells joined, namely,
one large cell united with a small cell ? Observe a
number of these cases of two-celled or three-celled
plants. Are the two or three united cells always
unlike in size ? Can you determine how these united
cells originate from single-celled plants ?

6. Draw a series of two-celled yeast plants representing
differences in size between the constituent cells.
Can you now determine the methqjl by which the
yeast plant reproduces itself by budding ? How does
this method of reproduction differ from that found
in Protococcus ? Is it a sexual or a vegetative method
of reproduction?

c. Observe, if possible, wild yeasts in cider or in ferment-
ing apples and make drawings to sho\v their struc-
ture and mode of reproduction.

4. Fermentation experiments. Select two flasks of equal size

and into one pour enough water to cover the bottom.
Into the other flask pour an equal amount of actively
fermenting yeast solution.

a. Test both flasks for oxygen and carbon dioxide with a

flame, with lirnewater, or with bariiun hydroxide.
Set aside for an hour, keeping both flasks at a uni-
form temperature of 25° C. At the end of an hour
test as above for oxygen and carbon dioxide. Result ?

b. Write up the above experiment in your notes, indicat-

ing the object, the actual results observed, and your
conclusions concerning what was proved with refer-
ence to the nature of fermentation by yeast. See
account of fermentation in the text.

c. Fill two fermentation- tubes with yeast solution. Keep

one at 25° C. and the other at a much lower

THE PLAXT GROUPS 89

temperature. Observe the two tubes every fifteen
minutes or at such, intervals as you find necessary.
Eesults ? How do you explain the differences ob-
served in the two tubes ? At the end of an hour
test the two tubes for carbon dioxide. Eesult?
Write up the above experiment in terms of object,
method, results, and conclusions to be drawn con-
cerning the nature of fermentation. Indicate method
and results by drawings.

5. Nutrition. Draw a diagram of a yeast plant greatly mag-
nified. Indicate the income and outgo of the yeast cell,
comparing its nutritive processes with those of Proto-
coccus and a specialized green plant. Contrast briefly
the nutrition of yeast and that of green plants like
Protococcus and Geranium (see Fig. 2 of the text).

BACTERIA

CLASS EXPERIMENTS

1. Expose a sterilized culture dish containing nutrient gelatine,
agar-agar, or other suitable substance for bacterial growth
in the classroom or laboratory for fifteen or twenty
minutes. Expose a second culture dish out of doors or
in a quiet room. Cover and observe after the cultures
have remained for twenty-four hours in a warm place.
a. Are there colonies of bacteria formed on the culture
media in both cultures ? Is there any difference in
the number and kinds of colonies in the two dishes ?
How do you account for any differences observed ?
b. Study the colonies with a hand lens or with a low
power of a compound microscope. Are there differ-
ences in the size, form, or color of the different
colonies? Can you account for such differences?

90 LABORATORY AND FIELD EXERCISES

c. Draw the colonies of one culture dish, indicating their

distribution, size, and form.

d. Conclusions. State your conclusions concerning the

following points :

(1) How do you account for the difference in the growth

of bacterial colonies in the two culture dishes
exposed to the air in the two different situations ?

(2) How are bacteria evidently distributed? "Why should

one avoid crowded rooms in time of disease
epidemics ?

(3) How do you account for the differences in the

appearance of different bacterial colonies ?
2. Expose a sterile liquid culture medium in a test tube to
the air as in the first experiment. Observe for several
days at successive class exercises. Note any changes
in the fluid which appear from day to day.

MICROSCOPICAL EXAMINATION OF BACTEKIA

1. Remove a small portion of a colony from one of the cul-

ture dishes in experiment 1 to a drop of water on a
glass slide and cover.

2. Prepare a similar slide from the liquid culture in

experiment 2.

3. Observe these preparations first with a low power and

then under the high power of a compound microscope.

a. Form types of bacteria. Consult the text figures and
discussions and observe as many of these forms of
bacteria as you can find in your preparations. Do you
find coccus, bacillus, and spirilla form types ? Note
the great variation in form and size of the bacteria,

I. M<»'<-iin'iitx. Do you find bacteria with independent
powers of movement?. What is the nature of this
movement ? The motor organs, cilia or tiagella, can

TILE PLANT GROUPS

91

only be seen with very high powers in stained prepara-
tions. Omit unless such preparations are available.
c. Cell division. Do you see any bacteria in which the
cells are dividing ? Consult Fig. 135 of the text, and
the discussion on vegetative reproduction in bacteria.

Fi<;. 21. Form types of bacteria

typ»s of bacilli; b, types of micrococci; c, types of spirilla. After Williams
From Marshall's " Microbiology "

d. If stained preparations of bacteria are available,

study the structure and form of bacteria in such
preparations.

e. Drfi"'ti/</x. Draw the form types of bacteria observed.
f. Bai'li'r'ia »f l]i<- //r///. Scrape the teeth with a sterilized

needle, or scalpel. Sterili/e first in a flnme or in
strong alcohol. Mount and observe. Do you find
more than one form of bacterial cell in your prepa-
ration? How many do you find? Make a drawing
of the bacteria found on the teeth.

92 LABOKATOKY AND FIELD EXERCISES

MOLDS
GENERAL NATURE OF MOLDS

Examine molds growing on various substances in the labora-
tory and note the following points regarding their habitat, habit,
and general structure :

1. Habitat. Upon what kinds of substances do molds grow ?

Are these substances sweet or sour ? acid or alkaline ?
solid or liquid ? How would the income and outgo of
molds in the form of gases, liquids, and solids compare
with that of a green plant like Protococcus or a Gera-
nium ? Do molds differ in the above particulars ? Com-
pare the income and outgo of a mold on bread with
that of yeast and Protococcus. Be able to point out
similarities and differences in the habitats, and in the
substances derived from them, in the three cases cited.

2. Habit. Is a mold plant on bread or apples differentiated

into organs or tissues like a higher plant ? See Figs. 139
and 140 of the text. Do different species of molds show
differences in color or structure ? To what great group
of green plants are molds most nearly related in their
general structure and differentiation ? In what impor-
tant respect do they differ from this plant group ?

3. Gross structure and growth.

a. G-rowth (use hand lens). Examine patches of mold on

apples, bread, and other media with naked eye and
hand lens. Do the patches of mold observed seem to
have any definite method of .spreading by growth ?
Can you account for the circular appearance (Fig. 143
of text) often observed in patches of mold ? Are some
patches colored ? Where is the colored portion ?

b. Eemove some of the colored and colorless portions of

different kinds of molds to different slides and mount

THE PLANT GROUPS 93

the material from each mold separately in water or
in a mixture of alcohol and glycerin. Study the
structures found in the colored and colorless portions
of your mounts. What do you conclude as to the
nature and function of these colored and colorless
portions of molds ? Are all molds which you examine
alike in the general structure of colored and colorless
parts ?

c. Draw diagrams to illustrate the structures found in the
colored and colorless parts of various molds. See text
and figures on black and blue-green molds.

4. Nutrition of molds (for example, apple mold).

a. Method. Remove some of the pulp from a decaying

apple with needles or the point of a scalpel and
place on the center of a glass slide. Add eosin solu-
tion and crush out gently under a cover glass. The
mold filaments, if present in the apple, will stain red
with eosin.

b. Observation. Do you find mold filaments (hyphse)

among the apple cells ? What is their function ? their
structure ? How are they related to the white aerial
mycelium and to the colored spores on the outside of
the apple ? Into what parts is the body of the apple
mold divided ? What is the functional relation of these
parts ? What kind of food would the mold secure
from apples ? How would it absorb it ? Compare the
income and outgo of apple mold with that of the wild
yeasts in apple or in cider. Draw a portion of the
apple mold as it appears within the apple. Include
the cells of the apple pulp surrounding the hyphae.

5. Summarize briefly the distinctive characteristics of molds

observed under the above topics, namely, Habitat, Habit,
Gross Structure and Growth, and Nutrition.

94 LABORATORY AND FIKLD EXERCISES

SPECIAL STUDIES OF MOLDS

RmZOPUS NlGRICANS (BLACK MOLD)

THE MYCELIUM AND NUTRITION

1. Spores and spore germination. Study spores which have

been growing on prune juice or some other nutrient

medium for different lengths of time ; for example,

twenty-four, forty-eight, and seventy-two-hour periods.

a. Early stages in spore germination. Use cultures which

have been grown from twenty-four to thirty-six

hours at 25° C.

(1) What is the earliest stage of spore germination that

you can find ? What change takes place in the
form and structure of a spore when it begins to
germinate? Does the entire spore cell elongate,
or only certain portions of it, to form the begin-
ning of a hypa or mold filament ? Do you find
branched hyplue growing from spores ? Note the
structure of the longer hyplue, including details
of cellular structure. Are there vacuoles ? Is
there a cytoplasmic sac or is there solid cyto-
plasm in the young hyphse ? (The nuclei of
KhizopuM cannot be seen in fresh material.) Is the
hypha produced by spore germination unicellular
or rnulticellular ?

(2) Draw two or three stages in spore germination, to

show the spore, the progressive growth of a
hypha from a spore, and the cellular structure of
the hyphal cell.

2. Development of the mycelium. Study later stages in

spore germination from cultures which have grown for
forty-eight and seventy-two hours.

PLANT GROUPS 95

a. Note the changes in the hyphpp produced after a longer

period of growth. Are they branched or unbranched ?
unicellular or inulticellular ? Have they the same
structure as in the earlier stages noted above ? Is
the spore still visible ? Draw two or three of these
older stages in spore germination. Label correctly.

b. Observe the mycelium of Jthizopus growing on bread or

some other medium. How was this mycelium pro-
duced ? How related to the branched hyphse noted
above as a result of spore germination ? How do you
account for the origin of a mycelium on moist bread
or in a moist chamber upon which no spores are
artificially sown ? Is there a submerged mycelium
within the nutrient medium and an aerial portion
exposed to the air ? What is the function of the two
parts of the mycelium? See text and Fig. 140.
3. Nutrition. How does RJiizopus differ from apple mold in
the nature of its habitat ? Are the foods of its habitat
solid or liquid ? In the case of Rhizopus growing on
bread, how does the fungus absorb and use the starch
of the bread as food ? Contrast the nutrition of the
apple mold and that of Khizopu* growing on bread.

REPRODUCTION

1. Spore formation by sporangia. Observe a mycelium upon
which round balls, or sporangia, begin to appear (Fig. 139
of text). Place a patch of this mycelium with light-
colored sporangia on a slide and observe with a low
power without mounting.

a. What is the relation of the sporangia to the hyphse ?
How are the sporangia related to the hyphte of the
mycelium ? Are they formed by any special hyphal
branches ? Consult the text and Fig. 140.

96 LABORATORY AND FIELD* EXERCISES

b. Mount the above specimen in glycerin and alcohol and

determine the relation of the sporangia to the hyphte.
What is the structure of a sporangial head ? What
is the nature of the contents of the young, light-colored
sporangia ? Consult Fig. 141 of text.

c. Bead -the text 011 asexual reproduction and spore forma-

tion in Rhizopus. Demonstrate as many of the stages
of spore formation described in the text as you can.

d. Draw at least two stages of young, light-colored sporan-

gia, including one in which spores are being formed.

2. Mature sporangia and spores. Study mature sporangia and

note the columella, the sporangium wall, and the spores.
What is the color and structure of the liypha which bears
mature sporangia ? Do you find the stolons and rootlike
hyphse connected with the liypha which bears the sporan-
gium ? See the text under Habit of Eliizopus. Draw
a mature sporangium and show its connection with
the main mycelium. Indicate stolons and rootlike out-
growths at the base of a sporangium-bearing liypha.

3. Sexual reproduction. B material is available, demonstrate

stages in the sexual process of Rliizopus. Read the text
on sexual reproduction. Demonstrate suspensors, game-
tangia, and zygotes, if seen in your material. Draw
stages observed in sexual reproduction. Label correctly.

4. Life history. Write a graphical life history of Rliizopus

similar to that already outlined for Spirogyra and other
green plants.

PENICILLIUM AND ASPERGILLUS

1. Habitat and habit. See the general nature of molds

previously studied.

2. Mycelium structure. Remove small portions of the myce-

lium of a blue mold, mount, and study. Has it the same

THE PLANT GEOUPS 97

structure as that of Rhizopus ? Is it unicellular or multi-
cellular ? Note the structure of the hyphse. Draw a
small portion of the mycelium of a blue mold, to differ-
entiate it from the mycelium of Rhizopus. Label
correctly.

3. Spore production. Eead the description of spore formation

in PenieUlium and Asperyillus (Figs. 144 and 145) in
the text. Observe spore-bearing cultures of these molds
as for Rhizopus. How do these molds differ from
Rhizopus in their method of spore formation ? How
does Penidllium differ from Aspergillus in this respect ?

4. Draw appropriate diagrams to express the methods of

spore formation in Penicillium or Aspergillus. State
concisely the difference in the method of spore forma-
tion in RkizopuB and the blue molds.

MUSHROOMS AND THEIR ALLIES

MUSHROOMS

1. Habitat. What is the habitat of mushrooms ? Be able to

name a number of habitats for mushrooms and their
allies, the bracket fungi. What forms a common
ingredient, or component, of the soil in all mushroom
habitats ?

2. Habit and parts.

a. What are the parts of a common mushroom ? What
are the submerged portions in the soil, log, or other
mushroom habitat ? See complete specimens for this,
including subterranean parts. What is the general
form, texture, and color of the aerial parts ? Observe
the underside of the umbrellalike aerial portion.
What do you find ? What is the function of these
structures on the underside of the umbrella ?

98 LABORATORY AND FIELD KXKKCISKS

b. Examine mushrooms of different ages. Is the color of

these plates, or gills, the same in young anil in old
specimens ? Compare the color change which you
observe with that of molds. What is the function or
use of the plates, or gills ?

c. Bisect a mushroom vertically through the umbrella and

its stalk. Study the relation of the gills to the umbrella.
Draw the cut surface of the mushroom and include the
subterranean and the aerial parts. (The subterranean
portions may be drawn from specially prepared material
if they are not available in the laboratory specimens.)
liead the paragraph in the text and consult Fig. 147
on the parts of the mushroom. Label correctly the
parts of your figure showing the habit of the muslin >om.

3. Nutrition. State concisely the function of each part of

the mushroom drawn above. Indicate the income and
the outgo of the mushroom in gases, liquids, and soh'ds
in connection with the above figure or in an outline
figure similar to Fig. 2, Part I, of text.

4. Growth and expansion of mushrooms. Study a series of

mushrooms of different ages. "What changes in the
size, form, and relation of parts do you find taking place
in mushrooms from young to mature stages \ What is
the apparent function, or use, of these changes ? Praw
a series of diagrams to illustrate the growth stages of
a mushroom and discuss briefly the function, or use,
of the changes indicated by your drawings.

5. Structure. Tease out on a slide portions of the stipe of a

mushroom. Mount and study. Is the mushroom cel-
lular like a higher plant, or is it an aggregation of
hypha' ? Contrast the structure of a mushroom and
that of a mold. Make drawings to indicate the structural
elements of the mushroom.

TJIE PLANT (JliOri'S 99

6. Spore formation. Select spore-forming lamellae of some

species of Coprinus. Peel off a small portion of the
s] lore-bearing surface and mount in water for study.

a. Observe with a low power the spore-bearing surface
of the lamella. l)o you find brown spores in groups
of four scattered over the surface of the lamella ?
Do you find basidia and paraphyses as described in
the text and illustrated in Fig. 148, c ?

I. Draw a portion of your section to bring out the above
points.

c. Examine the edges of your specimen for basidia bearing
sterigniata and spores. If not seen, tease the speci-
men in pieces with dissecting needles and observe
the edges of the pieces. Do you find basidia with
four sterigmata and young spores, and basidia with
sterigniata and brown spores ? How are these spores
formed at the ends of the sterigmata ? How are they
shed ? Draw a basidium with sterigmata and spores.

7. Sections. If basidia and spores are not found satisfactorily

in the above material, sections of the lamellae may
be used.

PUFFBALLS

(1KNERAL APPEARANCE, STRUCTURE, AND REPRODUCTION

1. Examine puffballs in two or three stages of development

(Fig. 150) to determine the character and limits of the
gleba and peridia. Note the changes in these two layers
as the puffballs mature.

2. Examine the contents of mature puffballs. Some puffballs

have indurated fibers, or hypha- (the capillitium), formed
in the gleba in connection with the spores.

3. Construct a drawing to show the relation of gleba and

peridia. Draw spores and capillitium.

100 LABORATORY AND FIELD EXERCISES

RUSTS

1. Examine leaves of cereals or other plants on which the

different kinds of spores of a rust are borne. Can you
see differences in color or form of the different kinds
of rust spores ? Are the spores borne in groups or
masses ? -Where is the mycelium from which these
spores originated ? How do the spores become exposed
to the air ? On how many and what kinds of hosts are
the different kinds of spores borne ?

2. Draw the stem or leaf surfaces on which spores are borne

showing the groups of spores, or sori, of each kind pro-
duced by the species being studied. Name the host and
the kind of spore in each drawing.

3. Examine the different kinds of spores of the rust micro-

scopically. How do they differ ? How are they adapted
for distribution and wintering ?

4. Draw each type of spore in some detail.

5. Life history. How many hosts are infested by the rust

you are examining ? What are the spring, summer, and
winter spores ? What is the function of each in the life
history ?

SMUTS

1. Examine corn or other cereals infested with smut. Tease
out some of the dark mass on a slide and examine micro-
scopically. What is the composition of these dark smut
masses ? Draw some smut spores. Where is the plant
which gave rise to the spores ? Is it a parasite ? How
do the spores become exposed to the air ? When and
how do these spores infect a new crop ?

THE PLANT GKOUPS 101

LICHENS

Select lichens growing on bark or stones and observe the
following points :

1. Color of upper and under surface. Moisten lichens and

note any change in color. What gives the peculiar color
to lichens ? Does the composition of the compound
plant explain its peculiar color ?

2. The form of lichens. Observe with hand lenses the lichens

on bark, rocks, etc. Do you find different kinds, or
species, of lichens recognizable by differences in size,
color, and form? See the kinds of lichens on the
display table.

3. Draw one or two lichens to illustrate their form.

4. Note the fruit cups, or apothecia, on the surface of some

of the lichens. These cups (Figs. 156 and 157 of the
text) are formed of spore sacs (asci) which bear spores
of the fungus partner of the lichen. Draw apothecia
to show their form and distribution.

5. Structure of the lichen. Moisten a small piece of a lichen

thallus and tear in pieces in' a drop of water on a slide.
Cover and crush out under a cover glass. Observe the
fungus hyphse and the algse which compose the plant
body.

a. The algae. Note their form, color, and relation to the

fungus hyphte. The latter grasp the algae with mi-
nute branches and absorb food from them. Are the
alga? multiplying by division ?

b. TJie fungus portion of the lichen. Observe the hyphae of

the fungus. What is their structure? Draw the
algae and fungus mycelium comprising the lichen.

6. Summary. Summarize the work of the two partners, the

fungus and the alga, in the life of the lichen.

102 LABORATORY AM) FIKLI) KXKllCISKS

LILAC MILDEW (MICROSPHAERA ALX/)

1. Structure. Observe the upper surface of leaves infected

with the parasite and note

a. The white mycelium covering the leaf surface with a
whitish mass of hyphse. Is this the plant body of
the fungus ? How is it anchored to the leaf and how
nourished ? "What is the structure of the body of
the plant?

2. Reproduction by ascocarps, or fruits. These are dark

bodies scattered over the surface of the leaf.

a. Distribution of the ascocarps. Outline a portion of a

leaf surface, showing the distribution of the mycelium
and the ascocarp fruits on a leaf.

b. Structure of ascocarps and asci. Remove ascocarps to a

slide in a drop of alcohol and glycerin by scraping
them from a leaf with a needle. Avoid scraping off
dirt and portions of the leaf. Note with low power

(1) The dark wall and app<'n<l<i</<'x. The structure of the

wall can be ascertained by slight crushing. Note
its cellular structure if it is not too dark. Note
the shape and attachment of the appendages to
the wall of the fruit. Draw a fruit body and one
or two appendages.

(2) Asci and ascospores. These are obtained by crush-

ing ascocarps under a cover glass with a needle.
How do asci and spores get out of the fruits in
nature ? When will spores be liberated and dis-
seminated ? How disseminated ?

(3) Spores. Note their shape and the number in each

ascus. .

3. Drawings. Draw a fruit body from which asci are being

pressed out. Draw an ascus and spores.

SECTION VII. BRYOPIIYTA (LIVERWORTS
AND M« ISSES

A. HEPATICAE (LIVERWORTS)
GAMETOPHYTE

The following outline for laboratory work is based upon the
relation of structure to function in liverworts. The outlines
are made so general in their nature that any one of several
species of thallose liverworts may be used. The term thaUus
applies to a plant body without true roots, stem, and leaves.
1. Habitat. From observations of living material and text
figures and descriptions determine whether liverworts
are typically mesophytic, hydrophytic, or xerophytic
in habitat.
i'. Habit and growth.

a. The apical meristem of liverworts is located in the

Hutches, or indentations, at the ends of the green
lobes of the plant body, or thallus. With this knowl-
edge determine the method of elongation and repeated
forking (dichotomy) of the branches. How is the
I'-Kte form or •/>}(* and similar liverworts

attained by this method of growth ? How would
new independent individuals arise from a rosette,
or colony of branches ? Is this a form of asexual or
of vegetative reproduction ?

b. Sketch a liverwort with several lobes, or branches.

c. Discuss briefly in your notes the method of growth

and the formation of rosettes and of new individuals.
103

104 LABORATORY AXD FIELD EXERCISES

3. Structure and function.

a. Adaptations for absorption.

(1) Observe with a hand lens the ventral surface of

liverworts which have been freed from soil.
What structures do you find ? Mount and study
under a compound microscope. How do these
structures (rhizoids) differ from true roots ? What
other structures do you find and how are they
related to the plant body ? Do these structures
have any particular function ?

(2) Sketch the lower surface of the liverwort, indicat-

ing the position of the structures seen. Label
rhizoids and scalelike leaves. Draw more in
detail one or more rhizoids.

b. Light relation and photosynthesis.

(1) Is the general form of the liverwort thallus adapted

for photosynthesis ? Be able to explain. Examine
the dorsal (upper) surface of the thallus with a
hand lens. Do you find anything corresponding
to stomata and the green mesophyll areas of leaves
of the higher plants? Thin surface sections
should be examined if difficulty is experienced
in determining the structure of the dorsal surface.

(2) Sketch accurately the structure of the dorsal surface

of the thallus as it appears under the hand lens
or low power.

(3) Sections. Study sections cut vertically through the

plant body, using low powers of the compound
microscope or a good dissecting microscope. Com-
pare the structure of the dorsal portion of the
liverwort with that of a green leaf. Are there
air spaces and an internal atmosphere ? What
is the disposition of green chlorophyll cells ?

THE PLANT GROUPS

105

Do you find stomata? What kind of tissue is
below the green chlorenchyma ? What is its
function ? Outline the section and detail a small
portion of its cellular structure. Label correctly.
Summarize the adaptations of the thallus of the
liverwort for photosynthesis and absorption.

FIG. 22. A common liverwort (Marchantia)

A, antheridial plant; I], archegonial plant, rh, rhizoids, and m, midrib, of the
leaf like flattened body /; c, capsules in which vegetative reproductive buds are
formed ; s, upright stalks (a, antheridial and ar, archegonial, the latter being dis-
tinguished by peculiar rays r). Slightly more than natural size. From Bergen
and Caldwell's " Practical Botany "

c. Storage and conduction. Are there any such structural
devices for storage of reserve foods and for conduc-
tion of water and foods in liverworts as we have
found in the higher plants ? Be able to explain.
4. Reproduction. If Marchantia is used for the following
study, the peculiar reproductive branches (receptacles)
will need to be explained by the teacher.
a. Distribution of sex organs.

(1) Study the distribution of sex organs on the dorsal
surface of the thallus in llicciocarpus, ConocepJmlus,

106

LABORATORY AND FIELD EXERCISES

or similar liverworts, using a hand lens. Are
the male and female organs aggregated or scat-
tered over the surface ? Are the plants monoecious

FIG. 23. The female receptacle of Marchantia

A, portion of a lengthwise section of a young receptacle
(semidiagrammatic), showing a row of archegonia hanging
down from the lower surface, the youngest heing nearest
the stalk (air chambers are present on the upper surface) ;
I, one of the ringerlike lobes back of the section (the diamond-
shaped areas indicate air chambers). B, a young sporo-
phyte within the parent archegonium (the region which is to
become the spore case is indicated by the cross lines, and
the small foot is attached to the base of the archegonium) ;
e, a special envelope developed around the archegonia of Mar-
chantia. From Bergen and Davis's " Principles of Botany "

(with male and female organs in separate groups
on the same thallus) or dicecious (with male and
female organs on separate plants ? If the organs
are separate, how is fertilization to take place ?
(2) Sketch plants, showing the distribution of sex
organs. Label.

THE PLANT GROUPS 107

b. Archegonia and antlieridia (structure of sex organs).
Study sections of plants cut so as to show the form
and structure of the sex organs.

(1) Note in each organ an outer layer and a central

column of cells. What is the cellular structure
of these two groups of cells ? the function of
each ? Are these cell groups alike in the female
organ, or archegonium, and in the male organ,
or antheridium ? If sex organs of different ages
are availahle, note the method of liberating sperms
and exposing the eggs for fertilization.

(2) Comparisons. How do the archegonia and the antlie-

ridia of the liverwort differ from the gametangia
(oogonia and antheridia) of alga? and fungi ? Are
archegonia and antheridia better adapted for secur-
ing the development of gametes and fertilization
in amphibious plants like liverworts than the
gametangia of algffi and fungi ? Be able to explain.

(3) Write a brief summary of the structure and adapta-

tions of the sex organs in liverworts. Indicate
also the important distinctions between arche-
gonia and antheridia and the gametangia of algse
and fungi.

(4) Draw diagrams illustrating the structure of each.

Study the structure of the sex organs in the text
and label parts of your figures accurately.

SPOROPIIYTE AXD LIFE HISTORY

1. Sporophyte. Study sporophytes of Ricciocarpus or other

liverworts by dissection and in sections.
a. Structure. What kinds of tissues and cells are found
in the sporophyte that you are examining ? What
is the apparent function of the tissues and cells

108 LABORATORY AND FIELD EXERCISES

observed ? Draw the sporophyte or the sporophyte and
surrounding tissues if studied in section. Label the
parts according to function.

b. Dissemination of spores. Are there any distinct devices

for spore dissemination in the sporophyte that you
are studying ? How would the spores be liberated ?
What is the nature of the spore cell and how is it
adapted for dissemination and for withstanding dessi-
cation, or drying, by wind and sun ?

c. Comparisons. Is the sporophyte a new structure in

plants studied thus far ? What is its particular use,
or function, in the life history of the amphibious
liverworts ? Would such a structure be equally use-
ful in the life history of the fresh-water algse ?
2. Life history. Write a graphical life history of the liver-
wort that you are studying, similar to the life histories
already written for Spirogyra and fungi. Explain in
your notes the special adaptations of the gametophyte
and the sporophyte to seasonal conditions and changes.

B. MUSCI (MOSSES)
GAMETOPHYTE

1. Habitat. What is the usual habitat of mosses ? Are they
for the most part mesophytes, hydrophytes, or xero-
phytes in habitat and structure ? Do you know of
exceptions to the general rule ? Can you think of ad-
vantages to be derived from the clustered habit of
growth of the mosses ? Would this habit be of any
advantage in securing food, moisture, and light, or in
insuring fertilization of eggs by the motile sperms of
mosses ? Summarize your ideas of habitat in your
notes.

THE PLANT GROUPS 109

2. Habit. Wash the earth from some moss plants and pre-

pare them for study. Observe the parts of the plant

body and compare them with those of higher seed plants.

a. Plan of the plant body. Is the central axis divided

into regular nodes and intemodes ? Are there lateral

and terminal buds ? Are the leaves cyclic or spiral

in arrangement ? Have the hairlike roots, or rhizoids,

any definite points of origin on the stem ? Do roots

and leaves have any definite tropic response ? Sketch

a stem, using outline figures, to indicate the relation

of parts of the plant body of the moss.

b. Study the microscopic structure of the leaves and

rhizoids and indicate the cellular structure of these

organs by accurate drawings.

3. Reproduction. Study plants which have antheridia and

archegonia in the terminal buds. The males may be
recognized as open disks, or clusters of antheridia, ter-
minating the stem. The female plants have similar
clusters of archegonia borne in closed buds.
a. Male disks and antheridia. Cut off the male head and
dissect it out in a drop of water on a slide.

(1) What is the shape of the moss antheridium ? its

structure ? Is it composed of different cell layers ?
How do these layers differ in structure ? What
function do you consider that each cell group,
or layer, has in the development and liberation
of sperms ? Do you find other cell structures
among the antheridia ? Sterile cell chains, called
paraphyses, exist among the antheridia of most
mosses, which probably protect the developing
antheridia.

(2) Draw antheridia and paraphyses. Label the parts of

the antheridium according to position and function.

110 LABORATORY AND FIELD EXERCISES

(3) If sections of antheridia are available, study in some
detail the structure of the outer protective layers
of the antheridium and the inner sperm mother
cells. Make an accurate drawing of a section of
an antheridium.

b. Female heads. Observe the difference in appearance of
male and female heads in mosses. Dissect out
female heads, as for the males above, or study
sections cut through female heads of a moss.

(1) Sections. If .sections are studied, note the origin of

the archegonia from the apical meristem of the
rnoss stem. What is the form and structure of
the archegonium ? Is there an outer protective
layer and a central column of cells as in the
antheridium ? Find the egg in the basal swollen
part (venter) of the archegonium. Detail one or
more archegonia and cells of the meristem from
which they arise.

(2) Dissections. If slides are not available, archegonia

may be dissected out of female heads as for
antheridia above. Draw archegonia if found by
this method, indicating the structure of the outer
protective layer and of the central column of
cells. See the account of the structure of the
archegonium under Ricciocarpus and the moss
in the text.

(3) Comparisons. Compare the archegonium of the moss

and the oogonium (gametangium) of algte. How
do they differ ? In what respects is the arche-
gonium better adapted for insuring fertilization
in land plants than the simple gainetangia of
the algae ?

THE PLA^T GROUPS 111

SPOROPHYTE

1. Mature sporophyte. Select a moss plant bearing a mature
sporophyte and study the relation of the gametophyte
and sporophyte.

a. Cut away the gametophyte on one side so as to expose
the base of the sporophyte. Is the sporophyte a para-
site on the gametophyte ?
b. Parts of the sporophyte.

(1) Study sporophytes carefully with the naked eye

and with a hand lens. Is the enlarged part (cap-
sule) differentiated into parts ? Note its connection
with the gametophyte. Draw the sporophyte and
label its parts after reading the text description
of the sporophyte.

(2) Operadum, peristome, and spores. With dissecting

needles remove the operculum and expose the
peristome. What is its structure in the moss
that you are studying ? How many teeth are
there in the peristome ? Breathe on the peristome
teeth and observe quickly under low power.
What is the nature of the movement of the
teeth ? What is the function of this movement
in the scattering of spores ? Draw a portion of
the peristome as seen under low and high powers.

(3) Spores. Remove spores from a capsule with needles

and note their size, form, and structure. Is a
spore a cell ? Is it a reproductive cell ? How is
it adapted to dissemination and to resistance to
the effects of sun and drought ? How do these
spores differ from spores of the algae ?

(4) Spore germination. What, do moss spores produce

when they germinate ? See text and laboratory

112 LABORATORY AND FIELD EXERCISES

material if available. How does the leaf}- moss

gametophyte arise ?

2. Embryo and young sporophyte. Study stages in the
development of the sporophyte. What relation does
the old archegonium wall sustain to the growing sporo-
phyte ? to the mature capsule ? Draw stages in the
development of the sporophyte. Label sporophyte and
old archegonium after reading the text discussion of
these structures.

LIFE HISTORY AND SEASONAL HISTORY

1. . What are the two alternating generations of the moss,
and how do they differ from similar stages in Ricdo-
carpus ? See the life history of Ricciocarpus in the text.

2. Write a graphical life history of the moss plant, using

outline figures. Indicate in the history the protonema
and gametophyte, and stages in the development of
the sporophyte.

3. Seasonal history and alternation of generations.

a. Are the mosses annuals, biennials, or perennials in

habit ? How do they pass the winter ? Determine
the main nutritive and reproductive seasonal activities
of common mosses. Contrast the seasonal history
of mosses with that of higher plants outlined in an
earlier part of the text. Are the alternating genera-
tions related to seasonal life ? If so, how ? Would
tli is seasonal relation be different in different mosses ?
Investigate this point for yourself as far as possible
by studies of mosses out of doors and in textbooks.

b. Write a brief account of your findings on the above

points and hand in with your drawings.

SECTION VIII. PTERIDOPHYTA (FERNS,
EQUISETA, AND LYCOPODS)

The Pteridophyta, as indicated in the text, are the plants
from which the higher plants had their origin in geologic
periods earlier than the present era. Their organization and
life history are therefore of especial interest in interpreting the
structure, ecology, and life history of the higher plants. In
order to make clear the contrasts and similarities between the
Filicales, or true ferns, and the higher seed plants, the following
laboratory directions are written, from the same standpoint and
with similar headings and references as the directions on the
higher herbaceous and woody plants of Part I. Constant refer-
ence is also made to the earlier work of the student, and to
the text dealing with the organization and adaptations of higher
plants to the environment.

A. FILICALES
SPOROPHYTE

Select for study one or more species of common wild and
cultivated ferns which show both mature and young, growing
leaves. Wash the earth carefully from stem and roots of at
least one specimen and study as follows :

1. Plan of the plant body. Compare the general plan of

the plant body of a fern with that of herbaceous and

woody plants studied earlier in the course, and with

such seed plants as may be available for comparison.

a. Is the central axis, or stem, divided into nodes and

internodes, with regular points of origin for leaves

113

114 LABOKAT011Y AND FIELD EXERCISES

and roots ? Are there lateral and terminal buds ?
How does the terminal bud of ferns differ from that
of higher plants ? Can you think of reasons for the
differences observed ? Are there lateral branches,
and if so, have they a definite arrangement ? Observe
the ramenta, or brown scales, characteristic of ferns
on the stem, leaf bases, and young leaves. What is
the probable function of these ramenta as the ter*
minal bud unfolds in the spring ?

2. Leaves.

a. Mature leaves. Contrast the mature leaves of ferns with

those of higher plants in size, form, texture, and
venation. What are the distinctive characteristics
of fern leaves accessible to you, and of fern leaves
known to you, as compared with those of higher
seed plants ? Study the mode of venation and the
termination of the veins, comparing ferns and some
common seed plants in this respect.

b. Young leaves. Study the growth and form of young

leaves of the terminal bud. What are the distinctive
characters of young fern leaves as regards form and
method of growth ?

3. Roots. Study the mode of brandling of roots. Is there

any distinctive feature which characterizes ferns in
this respect as compared with higher plants ? Deter-
mine also the origin and distribution of roots on
the stem.

4. Adjustments to the environment by tropisms (see the

text, Part I, and earlier laboratory work on tropisms).
Determine the tropisms of the stem, roots, and leaves
of ferns and apply proper terms to indicate the nature
of stimulus and response, — for example, protropic,
apotropic, and diatropic.

THE PLANT GROUPS 115

5. Distinctive characteristics. Summarize in your notes
under the above headings (namely, body plan, leaves,
roots, and the tropisms of the central axis and lateral
organs) the distinctive characteristics of ferns as com-
pared with higher plants.
0. Drawings.

a. Make an. accurate drawing of the fern examined.
I. Bring out as largely as possible, in the main drawing
and, where necessary, by detailed drawings of certain
organs (for example, leaves), the distinctive charac-
teristics of ferns named above under 5.
c. Draw an outline figure, indicating the positions assumed
by_the organs in a cultivated or wild fern. Indicate
stimuli and the nature of the response of the plant
organs by use of the proper terms, as in the earlier
studies of seed plants in Part I.
7. Habitat, habit, and environment.

a. Habitat. What is the common habitat of ferns in your

region ? Are they typically mesophytic, xerophytic,
or liydrophytic ? Do you know of exceptions to the
general rule ?

b. Environment. Compare the environment of common

wild ferns growing on the forest floor with ferns
growing in homes, and with common seed plants
growing in the open. How would these three habi-
tats compare as regards heat, light, soil water, food
elements in the soil, and the relative humidity of
the air ? Answer these questions in a paragraph
in your notes.

c. Habit. How is the habit of wild ferns especially adapted

to the above environment as regards the form, size,
and texture of the leaves ? Do cultivated ferns mani-
fest a different structure ?

116 LABORATORY AND FIELD EXERCISES

d. Seasonal life. Are ferns annuals, biennials, or peren-

nials in habit ? How do they pass the winter ? What
is the function of the rhizome in the winter season ?
Be able to indicate the seasonal activities of the fern
in a manner similar to that outlined for the bean,
clover, and apple in Part I of the text.

e. Summarize the principal seasonal activities of the fern

plant during summer, spring, and winter, indicating

the main plant organs concerned.

8. Anatomy of maidenhair fern (Adiantum). Examine with
a hand lens and low powers of the microscope trans-
verse sections of a fern stem, or rhizome, like that of
Adiantum, with a tubular vascular cylinder of phloem
and xylem.

a. Gross arrangement of tissues. Do you find the same

general tissue layers in the fern rhizome as in the
herbaceous stems studied earlier in the course ?
(Consult figures and text discussion on herbaceous
stems.) Are there the same general subdivisions of
the cortex into stereome and storage tissues, and of
the vascular ring into phloem, cambium, and xylem
as in herbaceous stems ? Note the relative width of
the cortex, vascular cylinder, and pith in the fern
and in herbaceous and woody stems.

b. Leaf traces and leaf gaps. Study sections of a fern

rhizome cut through the point of exit of a leaf.
(1) Is the vascular cylinder broken, forming a break,
or gap, with a small leaf bundle (the leaf trace)
in section opposite the gap ? Consult the text
descriptions and fix clearly in mind the nature
and relations of leaf trace, leaf gap, and the vas-
cular cylinder as a whole. See also the text
figures on the anatomy of Adiantum.

THE PLANT GROUPS 117

(2) Root traces. The root bundles which enter the

lateral roots may sometimes be found leaving
the vascular cylinder. Do they leave a gap as in
the leaf bundle ?

(3) Drawing. Outline your entire section, indicating

the main tissue layers and their subdivisions and
the relations of leaf trace, leaf gap, and cen-
tral cylinder. How does Adiantum differ from
an herbaceous plant like Salvia in its gross
anatomy ? Consult the text discussion of Salvia
in Part I.
e. Minute structure of the tissues.

(1) Epidermis, cortex, and pith. Draw in detail a few

characteristic cells of each of the above layers
and their main subdivisions, to show the dis-
tinctive cell characteristics of each tissue. Label
the parts of the cells. What is the function of
eacli cell type in the rhizome, and how is its
structure adapted to its function ?

(2) Vascular cylinder. Study the following tissues of

the vascular ring and leaf trace critically with
low power :

(«) Xylem. Characterized by large water-carrying
cells resembling ducts in higher plants.
These xylem cells, or tracheids, stain red
where sections are stained with safranin
(the dye commonly used in staining xylem).
Are there rays or other living tissues in the
xylem of ferns, as in that of higher seed
plants previously studied ?

(7>) Pldoe'm. Surrounding the xylem. The sieve
tubes are the large cells seen in the phloem
flanking the xylem on either side.

118 LABORATORY AND FIELD EXERCISES

(c-) Cambium. Is there any evidence of a cambium
composed of regular cells as in higher plants ?

(d) Endodermis. A dark-brown layer surrounding
the phloem, beneath which is a single cell
layer containing starch, called the pericycle.

(Y) Does the leaf trace have the same structure as
the main vascular cylinder ?

(3) Drawing. Make a cellular drawing of a small por-

tion of the main vascular cylinder, or of the leaf
trace to show the structure of the tissue elements.
Label correctly.

(4) Summary. Summarize the distinctive features of

the tissue arrangements in the fern as compared
with that of herbaceous dicotyledons. See the
summary of the anatomy of herbaceous stems in
Part I of the text.
9. Anatomy of eagle fern (Pteris aquilind).

a. Gross anatomy. Study transverse sections of the eagle

fern, as indicated above for Adiantum, using a hand

lens first and then low powers of the microscope.

Compare the main tissue layers with those of the

maidenhair fern.

(1) Epidermis and cortex. Are both epidermis and cor-

tex present, and do they have the same cell char-
acteristics as in the maidenhair fern ? Is there
an exoskeleton in Pteris?

(2) Vascular ring. Study the vascular system carefully

with a hand lens and low power. Is there any-
thing corresponding to the single vascular ring of
Adiantum ? What kinds of tissue masses occupy
the pith region ? Do you find central skeletal, or
strengthening, masses and vascular strands ? See
text discussion of the eagle fern (Pteris aquilina).

THE PLANT GROUPS 119

(3) Drawings. Construct an outline figure (no cells)
of the cross section of the stem of Pteris. Label
the parts accurately. Discuss briefly the distinc-
tive features of the anatomy of the eagle fern as
compared with that of Adiantum.
o. Minute anatomy.

(1) Transverse sections. Work out and draw the cellu-

lar structure of one vascular strand of the rhizome
in Pteris and label accurately. Draw also a few
cells of the epidermal, of the skeletal, and of the
storage tissues.

(2) Long sections.

(a) /Skeletal tissue. Work out and draw a few cells
of the strengthening, or skeletal, tissue as
seen in long section. Are these cells living ?
What are their most distinctive structural
characteristics? Explain in your notes.

(5) Vascular tissues. Study the vascular tissues
in long section. Find the sieve tubes of the
phloem and water-conducting cells, or
tracheids, of the xylem. Determine the
« shape, size, and wall markings of each type

of cell element.

(c) Sieve tubes. Find in the sections the abundant

sieve plates. Consult text figures. Be able
to discuss the structure and function of the
sieve plates. Draw accurately one or more
sieve tubes and the adjoining cells.

(d) Tracheids. Study the form, cell contents, and

cell-wall thickening of the tracheids. How
does the tracheid differ from the duct, or
vessel, of the higher plants ? Is it as efficient
in water conduction as the vessels are?

120 LABORATORY AND FIELD EXERCISES

Determine with care the thick and thin
areas of the wall. Which area constitutes
the greater portion of the entire wall of the
tracheid? What is the function of each in
the work of the tracheid and the stem?
(e) Summary. Draw and discuss briefly the struc-
ture and functions of the tracheids as com-
pared with the ducts of the higher plants.
10. Asexual reproduction.

a. The sorus. Observe the lower (abaxial) surface of fern
leaves for clusters of fern sporangia, or sori.

(1) What is the position of the sori with reference to

the veins ? Can you think of a reason for this
position ? Are the sori numerous or infrequent
on the leaves that you are examining? What
advantages has the fern sporophyte over the moss
sporophyte in the production of spores ? See text
discussion for the number of fern spores pro-
duced by a single sporophyte annually.

(2) Structure of the sorus. With hand lens and low

power of the microscope determine the structure
of the sorus. Has it a covering ? Do sori of dif-
ferent ages have a different color and appearance ?
To what is this difference in color due ? Where
there is a membranous covering (indusium), note
its form in young sori, and the method by which
the brown sporangia became exposed to the air
in older sori. If different species of ferns are
available, observe sori and indusia of different
shapes and forms. Draw a single pinnule of a fern
to show the form, structure, and distribution of
the sori. Compare the indusia in your specimens
with those shown in the text (Figs. 168 and 176).

THE PLA^T GROUPS 121

b. Sporangia and spores.

(1) Dissect out sporangia into a drop of water on a

slide. Mount and study the cellular structure of
the sporangium carefully. Are the cells all alike
in structure and in function? To demonstrate
this point remove sporangia to a dry slide. Breathe
on them gently and observe quickly under low
power. Result? Consult the text discussion of
spore dissemination.

(2) Draw accurate diagrams of a closed and an open

sporangium as you observe them in your own
preparations. Be prepared to explain the peculiar
structure and mechanism of the annulus.

SUPPLEMENTARY STUDIES

1. Sporogenesis. If slides are available, the essential stages in
sporogenesis, or spore forumtion, may be worked out, illustrating
the archesporium and tapetum, the sporogenous and spore mother-
cell stages, and the formation of tetrads and spores.

2. Analysis and classification. Each student should learn to
use the analytical key and analyze a few species of common ferns.
Record your analyses as follows :

«. Family —

b. Genus —

c. Species: scientific name, ; common name,

GAMETOPHYTE

After examining growing fern gametophytes, determine and
record the following points concerning the habitat and nature
of the gamete-bearing plant, or gametophyte generation, of
the ferns. :

1. Habitat. AVhat is the natural habitat of these little plants
in nature ? Does, your observation indicate that fern

122 LABORATORY AND FIELD EXERCISES

gametophytes are abundant iu their natural habitat ?
Why not, since ferns produce abundant spores ?

2. Habit. What group of plants already studied have game-

tophytes most similar to those of ferns ? Is this group
closely related to ferns ? What is the most striking
difference between the ferns and the Hepaticae as
regards their gametophyte and sporophyte plants ?

3. Structure. Wash the soil from the underside of mature

gamete plants. Determine the structure of the plant
body and the nature of the absorbing organs.

4. Sex organs.

a. Study the position of the archegonia and antheridia on

the ventral side of the gametophyte. Observe in
models and in the text the structure of these organs.
Are they essentially the same as those in the Bry-
ophyta ? How would fertilization be effected ? Is the
position of these sex organs favorable for insuring
fertilization ? Be able to explain.

b. If sections are available, the student should study sec-

tions cut through the gametophyte and the sex
organs for a more exact knowledge of the structure
of the archegonia and antheridia.

c. Development of the gametophyte. Study germinating

spores which show early stages in the formation of
the gametophyte. Draw and label stages observed.

THE EMBRYO AND THE LIFE HISTORY

1. Embryo. Study young sporophytes growing from game-
tophytes. What are the parts of the spore plant ? How
are they attached to the gamete plant ? What relation
does this young spore plant bear to the adult sporophyte ?
Consult the text figures on this point.

THE PLANT GROUPS 123

2. Life history.

a. Construct a graphical life history of the fern similar to

that of Ricciocarpus.

b. Contrast briefly in your notes the alternating genera-

tions of the fern and the bryophyte.

B. EQUISETALES (HORSETAILS)
SPOROPHYTE

Compare the main subdivisions of the plant body of some
species of Equisetum with that of the true ferns as regards
both form and function.

1. The plant body and its plan.

a. Main subdivisions. Has the Equisetum plant the same

divisions into horizontal rhizome, aerial green leaves,
and roots as the true ferns ? What organs perform the
functions of photosynthesis, absorption, conduction,
and storage ? What portions would carry the plant
over winter or extreme drouth ? How does Equisetum
differ from ferns as regards the above points ?

b. Vegetative parts. Is the main stem segmented into

regular nodes and iuternodes ? Is the leaf-and-
brauch arrangement cyclic or spiral ? Determine
the origin of lateral buds and branches with refer-
ence to the leaves. Is it the same as in higher
plants ? Compare the aerial and underground stem
and lateral branches in these respects. Are they
all constructed on the same plan ? Note any varia-
tions that may occur. Observe the origin and nature
of the roots.

c. Strolili, or reproductive cones. Observe these structures

and their position on the plant. Are their parts
(as seen externally) arranged on the same plan as

124 LABORATORY AND FIELD EXERCISES

the leaves on the main axis, thus following the
general body plan ? Is the strobilus placed in the
right position on the shoot for spore dissemination?

2. Adjustments to the environment. Are there the same

responses to environmental forces by tropisms in Equi-
setum as in ferns ? Be able to explain the relation
between the responses of the various organs and the
functions which they perform.

3. Drawings. Make an accurate drawing of the Equisetum

plant studied, to indicate the subdivisions and plan of
the plant body. Indicate by proper terms the responses
and adjustments of the various organs to environ-
mental forces.

4. Analysis. Analyse one or more species of Equisetum and

record analyses under family, genus, and species, as
in ferns.

5. Habitat and habit.

a. What is the usual habitat of the equiseta ? Are there
variations in habitat ? Determine these points by
field studies and by reference to texts and analytical
keys. Does the habitat of species growing in ponds
or lakes correspond to the form and structure of
these species ? How can you explain the evident
discrepancy between habitat and habit in these cases ?

6. Seasonal history. Are equiseta annuals, biennials, or

perennials ? herbaceous or woody plants ? In what
form do they pass the winter ? How do they differ
from ferns in these respects ?

7. Summary.

a. Summarize the distinctive characteristics of equiseta

which differentiate them from true ferns.

b. Explain the apparent discrepancy between habitat and

habit in species growing in water.

THE PLANT GROUPS 125

SUPPLEMENTARY STUDY

Equisetum arvense
SPOROPHYTE

1. Dimorphic character of the aerial stems.

a. Compare aerial vegetative and reproductive shoots of

Equisetum arvense as to body plan, lateral organs, and
color. What is the apparent advantage of this division
of labor in aerial stems ? Do the reproductive and the
vegetative shoots grow at the same time of the year ?
Which has the longer life ?

b. Construct a diagram to show the relations of the under-

ground and the dimorphic aerial portions of Equisetum
arvense. Label parts correctly.

2. Structure and reproduction.

a. Structure. Cut thin sections across the stems of Equi-

setum arvense. Mount and study with a low power.

(1) Locate the main tissue layers : namely, epidermal, skele-

tal (or supporting), vascular (or conducting), and stor-
age tissues. How does the general arrangement of
tissues differ from that found in the fern ? Can you
relate the position of the various tissues to their use,
or function, in the plant body, — for example, the
skeletal and the green tissue ? Why are both of
these tissues placed on the outside of the stem ? Why
is the vascular tissue so small in amount ? What are
the advantages of the large intercellular spaces ?

(2) Make an outline drawing (no cells) of your section

illustrating the position of the various tissues.

(3) Summarize the adaptive features of the structure of

the stem.

b. Asexual reproduction.

(1) Compare the arrangement of the parts of the stro-
bilus of Equisetum arvense with that of the species
examined above as to plan and arrangement of parts.

126 LABOKATOKY AND FIELD EXERCISES

(2) Bisect a strobilus. What are the parts of a strobilus

thus exposed ? Is the strobilus a modified shoot ?
Are there nodes, internodes, and lateral members,
as in the main central axis ?

(3) Sporangiophores and sporangia. The sporangiophores

are the shield-shaped lateral organs of the strobilus
which bear the sporangia. They are not true sporo-
phylls, or modified leaves. How many sporangia
are there on a single sporangiophore ? How are they
arranged ? What is the shape of a sporangium ?
Dissect sporangia out on a slide to determine this
point. Can you determine the mode of opening
in rather mature sporangia? Draw sporangia to
show the line of dehiscence.

(4) Spores and elaters. Dissect spores out on a slide (let

them dry if preserved material is used). Breathe
on them gently. Result ? Study the structure of
the spores. Draw them. See the text for a descrip-
tion of spore structure. Label your drawing.
3. Life history and relationships. Study the life history of
Equisetum in the text.

a. Why are these plants classified with the ferns under the

common group Pteridophyta ?

b. In what respects are the ferns and equiseta alike in their

life history ? Summarize your conclusions respecting
a and b in your notes.

C. LYCOPODIALES (CLUB MOSSES)— LYCOPODIUM
SPOROPHYTE

1. The plan of the plant body. Compare with that of true
ferns and equiseta. Are there characters concerned
with the central axis or the lateral members (leaves,
roots, and branches) which distinguish lycopods from
the other Pteridopliyta already studied?

THE PLANT GROUPS 127

2. Asexual reproduction.

a. Observe the strobili of a lycopod which is bearing spores.

What is the position of the strobilus on the stem?
Are its parts of the same general nature and arrange-
ment as those of the main axis?

b. Structure of strobilus, sporangia, and spores. Determine

these points by dissecting the leaves, or sporophylls,
from strobili. How is the sporangium related to the
scalelike leaves (sporophylls) which bear them ? How
and where do the sporangia open (dehisce) to shed
the spores ? Are the spores numerous and all of one
kind, namely, homosporous ?

c. Draw a single sporophyll with its sporangium.

3. Analysis. Analyze two or more species of lycopods and

record your analyses as for ferns and equiseta.

4. Distinctive characters. Summarize the characters which

seem to you to distinguish lycopods from other Pteri-
dophyta studied.

SELAGINELLA
SPOROPHYTE

Study one or more species of Selaginella with reference
to the following more important and distinctive features of
these plants:

1. Body plan and adjustment of organs to the environment.
a. Leaves.

(1) Note their arrangement and adjustment to light.

If erect and creeping species are available, com-
pare them in these respects.

(2) Note the ligule, a small outgrowth on the adaxial side

near the stem. This is an ancestral character which
existed in the lycopods of early geologic periods.

128 LABORATORY AND FIELD EXERCISES

b. Rhizophores and roots. The rhizophores are naked, stem-
like organs which Lear the roots at the tip, where
the rhizophores come in contact with the soil. What

FIG. 24. Selaginella martensii

A, branch bearing cones and showing the leaf arrangements ; B, inner face
of a megasporophyll, showing the large megasporangium containing a group
of four megaspores (tetrad) ; C, two views of megaspores; I), inner face of mi-
cro.sporophyll, showing microsporangium ; E, microspores ; F, diagram of a
longitudinal section of cone, illustrating position of microsporophylls and megaspo-
rophylls and their microsporangia and megasporangia. From Bergen and Davis's
" Principles of Botany "

would be the function of these rhizophores in the
natural habitat of Selaginella ? The rhizophore is
also an ancient organ which occurred in the early
relatives of Selaginella.

THE PLAXT GROUPS 129

c. Draw a portion of a Selaginella plant to illustrate the
above points.

2. Asexual reproduction.

a. Strobili. Do the species of Selaginella that you are
examining bear distinct strobili? What is the nature
of the sporophylls ? Do they resemble ordinary
leaves in form and color ? Why are they called
sporophylls ?

I. Sporangia and spores.

(1) Remove sporophylls from different parts of the stro-

bilus and examine the sporangia. Are the sporangia
all alike in appearance and in the number of spores
which they bear ? Dissect spores from several spo-
rangia to determine this point. What do you find?
Have we studied any plants before which bore two
kinds of spores ? Do any particular portions of
the strobilus bear a particular kind of sporangium
and spore ?

(2) Draw the two kinds of sporangia and sporophylls

found in the strobili that you are examining.
Draw the two kinds of spores. Eead the text
on asexual reproduction of Selaginella and label
your figures correctly.

(3) Study of sections. If sections of strobili of Sela-

ginella are available, study the relations of the
microsporangia and megasporangia to the main
axis of the strobilus and to the sporophylls.
Observe the structure of the sporangia and
spores. Draw and label your figure.

3. Life history. Study the text figures and discussions con-

cerning the gametophytes, sex organs, and life history
of Selaginella.

4. Distinctive characteristics. Summarize the new and dis-

tinctive characters of Selaginella.

SECTION IX. GYMNOSPERMS

A. CYC AD ALES (CYC ADS)
SPOROPHYTE

1. Habitat and relationships.

a. Consult the text and assigned readings concerning

the habitat, classification, and relationships of the
Cycadales. What is the natural habitat of the
cycads in the United States ? Were they ever more
abundant and important as a part of the world's
vegetation than they are at the present time ? What
position in classification do they occupy among
living plants ? What ancestral relationships have
they which make them important to study in a
course in plant evolution ?

b. Summarize answers to the above questions in your

notes.

2. Habit and body plan.

a. What is the body plan of cycads ? See the arrange-

ment of leaf bases and green leaves on the stem.
Do you know of ferns or seed plants which the
cycads resemble in general habit? Are the cycads
closely related to such plants ?

b. Leaves. Study young and mature leaves of cycads.

In what respects do cycad leaves resemble those of
ferns ? If leaves are unfolding, notice the method
of unfolding of the entire leaf and of the pinnules.
If possible, note the venation of leaves of Cycas and
Zamia, Are the resemblances of cycad leaves to
130

THE PLANT GROUPS 131

those of ferns a matter of chance or one of blood
relationship ?

c. Roots. Are the roots of cycads distinctive ? If so, in
what respects ?

3. Asexual reproduction. Study living or preserved material

or museum specimens.

a. Strobili. Determine the position of strobili on the
main axis, the distribution of male and female
strobili on the same or on different plants, and the
general nature of the strobili.

(1) Are the strobili terminal or lateral in origin ? Are

the plants monoecious or dioecious as regards the
distribution of strobili?

(2) Are the parts of the strobilus arranged on the same

plan as those of the main plant body ? To what
parts of the plant body do the main parts of the
strobilus correspond ? Are there sporophylls and
a central axis as in the lycopods and Selaginellal
Are the sporophylls cyclic or spiral?

4. Sporophylls and sporangia.

a. Microsporophylls, sporangia, and spores.

(1) Sporophylls. Note the form and relation of the

sporophylls. Compare (by means of specimens
or figures) the sporophylls of different kinds of
Cycadales. Are any of them leaflike ? To what
do these sporophylls correspond in ferns ? in
Selaginella and lycopods ?

(2) Microsporangia. Are the microsporangia abaxial or

adaxial on the sporophyll? Has their position
any relation to spore-shedding? Is there any
definite arrangement into sori ?

(3) Spores. Searcli for sporangia shedding spores. Is

there a definite line of dehiscence? Study spores

132 LABORATORY AND FIELD EXERCISES

and compare them with those of ferns and
Selayinella. Do cycad spores differ in structure
or in function from those of Pteridophyta ?
(4) Drawings. Draw the ventral (abaxial) view of a
microsporophyll and its sporangia. Label. Draw
two or three microspores. .

b. Megasporophylls and sporangia.

(1) Eemove entire sporophylls with their megaspo-

raiigia, or ovules, from the female strobili. Note
young or undeveloped megasporangia if found.
Are these megasporangia, or ovules, similar to
the ovules of the mandrake and the bean studied
earlier in the text ? Consult these earlier figures
and text descriptions. If they are the same, are
all ovules and seeds megasporangia ?

(2) Gross structure of the megasporangium. Bisect the

megasporangia of Zamia and study their structure
as shown on the cut surface. Compare the Zamia
megasporangium with that of the mandrake. Do
you find integuments, micropyle, and funiculus
in the megasporangium of Zamia ? What fills
the center of the sporangium ? Do you find
structures looking like archegonia, or eggs? Use
hand lens and examine your specimen carefully.

c. Conclusions. What conclusions do you draw as to the

nature of the megasporangium and its contents ?
Does it contain spores or structures belonging to a
gametophyte generation ? Does the sporangium ever
open (dehisce) as in the microsporangia ? State in
summary form your conclusions as to relation of
the megasporangia of Zamia to ovules of the man-
drake, locust, and bean studied in Part I, and to
megasporangia in the heterosporous Selaginella.

THE PLANT GROUPS 133

GAMETOPIIYTE

Study text figures and descriptions of the megasporangium
of Zamia. With the aid of such descriptions study your
specimen with a hand lens and determine the relation of the
following structures :

1. The integument layers and the micropyle. How do the

layers of the integument differ? Is the micropyle of
appreciable width ?

2. The pollen chamber and the remnant of the sporangium.

Do you find these structures in your specimen ? How
are they related to the gametophyte and the arche-
gonial chamber ?

3. The gametophyte.

a. Is the gametophyte of Zamia as large as that of the

fern ? Has it the same functions ? What was the
source of its food supply ? How was this in the fern ?
in Selaginella ? Test the gametophyte with iodine.
Does it contain reserve starch?

b. Archegoma. How many archegonia are there on a

single gametophyte of Zamia ? How do they compare
in structure with the archegonia of Selaginella, ferns,
and mosses ? Have any structures common to the
earlier archegonia been lost ? Note the archegonial
chamber. What is its special function at the time
of fertilization ? Draw the upper third of the mega-
sporangium and gametophyte to bring out the above
structures. Label.

4. Pollination and fertilization. How is pollination effected

in Zamia 1 Is self-pollination or cross-pollination the
rule? How does the pollen grain reach the pollen
chamber ? What is the function of the pollen tube ?
How is fertilization effected in Cycadales ? In what

134 LABORATORY AND FIELD EXERCISES

respects is the process in cycads intermediate between
that in ferns and that in the mandrake.

5. Structure of the seed. Study the structures of the seed

in Zamia from specimens or from figures. Compare its
structure with that of the mandrake and the pea. What
sporophytic and gametophytic structures are comprised
in the seed of Zamia ? If specimens are available, draw
a sectional view of the cycad seed to show the parts of
the embryo and the remaining structures of the seed.

6. Seed germination. The method of seed germination in

cycads is well illustrated by the germination of the
acorns, or seeds, of the oak. The important things to
note are

a. The structure of the seed and embyro.

b. The exit of the embyro from the hard seed coat.

c. The function of the cotyledons and the exit of the

plumule.

d. The final adjustment of the young plantlet in the

soil and air.

If the acorn is used, make appropriate drawings to
illustrate stages a-d.

7. Life history. Study the text diagrams in the graphical

life history of Zamia. Be able to label and explain
each stage of the life history illustrated in the diagram.

8. Summary. Summarize briefly the following points relat-

ing to the structure and reproduction of Zamia and
the Cycadales.

a. Summarize the fernlike characteristics of Cycadales

which indicate their pteridophyte ancestry.

b. Summarize their new gymnosperm characters.

c. Give briefly the characteristics in which Cycadales are

intermediate between PteridopJiyta and the higher
seed plants.

THE PLANT GROUPS 135

B. CONIFERALES (CONE-BEARERS). SPRUCE AND PINE
SPOROPHYTE

1. Habitat (Field study).

a. What is the nature of the habitat of the spruces and
pines of your region as regards soil, drainage, and
climate ? Do they grow best on lowlands or on well-
drained slopes and uplands? What is the distribu-
tion of spruces and pines in the United States ? What
is their natural habitat as regards soil and climate ?
Are they mesophytic or xerophytic in general habit ?
How do you explain the apparent discrepancy between
habitat and habit in these trees ? Consult manuals
and assigned readings 011 the above points.

I. Summarize the above points in your notes under habitat,
including geographical distribution and habit.

2. Habit.

a. Form and body plan of the spruce and pine trees. Eeview

the text discussion in Part I on the body plan and
mode of growth of the spruce and pine trees. Be able
to account for the erect conical form, the excurrent
trunk, and the false whorls of branches of spruces
and pines. Why is the trunk excurrent ? What de-
termines the conelike form of the entire tree ? How
do the false whorls arise ? Is the entire leafage well
exposed to light ?

b. Summarize the above points under Habit in terms of

body plan, methods of growth of buds and branches,
and tropistic responses of leaves and branches.
For a general discussion of the habitat, distribution, and com-
mercial importance of the spruces and pines the student should
consult the text and figures under Gymnosperms in Part III
of text. See also the general map of forest areas (Fig. 223).

136 LABORATORY AKD FIELD EXERCISES
ANATOMY OF THE SPRUCE STEM

TRANSVERSE SECTIONS

Cut thin transverse sections from living spruce twigs about
one eighth of an inch in diameter. Mount some sections in
alcohol and some in iodine solution. Observe the latter sections
for starch storage, wood rays, pith, etc.

1. The main tissue layers of the spruce.

a. Compare the tissue layers of the spruce with those of

the lilac and fern. Which stem does the spruce most
nearly resemble in structure ? Does the spruce pos-
sess both a cork cambium and the cambium which
forms phloem and xylem ? Note carefully the rela-
tions of corky bark, green cortex, phloem, cambium,
xylem, and pith.

b. Leaf gaps and traces. Observe the shape of the pith.

Do you find lobes of the pith (leaf gaps) extending
into the xylem ? If so, note their extent and the
nature of the xylem ring opposite them. Leaf traces,
•looking like wide wood rays, often appear opposite
these pith lobes or leaf gaps in the spruce. Consult
the text figures.

c. Observe sections stained with iodine for starch-storage

areas. Where is starch stored in the spruce ?

d. Make an accurate drawing of your section in outline

(no cells), indicating the main tissue areas and their
limits. Include wood rays, annual rings, leaf gaps,
and leaf traces. Study the text and label your
drawing accurately.

e. Summary. Write an accurate and concise summary of

the structure of the spruce stem in the form indicated
for herbaceous dicotyledons and for the fern. Indicate

THE PLANT GROUPS 137

in the summary the particulars in which the spruce
stem resembles that of the fern, and the significance
of this resemblance. Consult the text on the structure
of the spruce stem.

2. Structure of the tissues (prepared slides). Observe with
low and high powers of the microscope the tissue layers
and tissue elements in stained preparations of spruce
stems.

a. The cork lark. Of what kinds of tissue is it composed ?

Is there an apparent tendency to form separating
scales ? Are the cells of the cork bark living or
lifeless ? The cork cambium forms an inner layer of
rectangular living cells on the inner side of the cork
layers in the spruce.

b. Cortex. Observe the character of its cells and the struc-

ture of the large resin canals with a lining layer of
small resin secreting cells.

c. Phloem and cambium. Can you differentiate the phloem

and cambium layers ? Does the phloem show annual
growth layers corresponding to those of the xylem ?
What marks the outer boundary of each annual layer
of phloem (this outer limit of the phloem can be
determined by the outer limit of the wood rays) ?

d. Xylem.

(1) Annual rings, composed of spring and summer wood.
Compare these with similar structures of woody
dicotyledons. How do the tissue elements of the
spring and summer wood differ in the spruce
from similar structures in lilac and alder ? Which
kind of wood is better adapted for rapid water
conduction ? Is the wood structure adapted to
the leaf structure and transpiration requirements
in the spruce ?

138 LABORATORY AND FIELD EXERCISES

(2) Storage tissues of the xylem. Is the spruce as well

provided with storage tissues as the above-
mentioned stems ? How does it compare with
the storage system of the fern stem ? Is the
spruce intermediate in this respect between
the alder and the fern ? Be able to explain.

(3) Drawings. Outline a sector of a transverse section

of the spruce stem. Detail in this sector the cork
layer, a small portion of the xylem at the junction
of two annual rings, a leaf gap, and a leaf trace.

LONG SECTIONS

Study thin sections cut from spruce or pine to determine the
structure of the water-carrying tracheids and of the wood rays.
Mount in alcohol if freshly prepared material is used.

1. Tracheids. What is the nature of the conducting elements,

or tracheids, making up the wood of pine or spruce ?
Are they single cells ? What is their shape ? What are
their surface markings ? How do they differ from the
vessels, or trachea?, of the higher plants studied earlier
in the course ? Compare the ducts of the lilac and alder
with the tracheids in your slide. Do the wall mark-
ings of tracheids differ from those of ducts ? Study the
bordered pits on the walls of the tracheids, consulting
the text concerning their structure. On which walls
of the tracheids are the bordered pits, the tangential
walls or the radial walls ?

2. Wood rays. If rays are seen in radial sections, note the

differentiation of their cells into living starch-bearing
cells and dead water-conducting tracheids.

3. Drawings. Draw a small portion of your section accurately

to show the structure of tracheids and wood rays.

THE PLANT GROUPS 139

ASEXUAL REPRODUCTION

1. Ovulate strobili of the spruce. Study surface views of

mature dry strobili of the spruce and median long
sections of preserved strobili.
a. Gross parts.

(1) Are the parts of the spruce strobilus the same as

those of strobili in lycopods and cycads ? Are
there sporophylls ? a central axis ? ovules or
megasporangia ? Is the strobilus cyclic or spiral
in plan ? Study both surface and sectional views
of the strobilus to determine the above points.

(2) Seeds. Do you find seeds or ripened megasporangia

in the mature strobili? How are they adapted
to dissemination?

(3) Drawings. Draw surface and sectional views of

portions of the strobilus about one inch in
length. Draw the median section very accu-
rately. Label the parts in terms of sporophylls
and sporangia.

1. Megasporopliyll, sporangium, and bract. Piemove sporo-
phylls from strobili and determine the relations of
the above structures. Construct a vertical sectional
view of bract, megasporophyll, and megasporangium.
Consult the text concerning the morphology of the
spruce strobilus. Is it a simple strobilus like that of
the lycopod or is it a branch system with bracts
corresponding to regular leaves ? To what do the cone
scales correspond ?

2. Staminate strobili.

a. Gross parts. Have the staminate strobili the same parts,
with a similar arrangement, as the ovuliferous strobili?
Have they both bracts and sporophylls ?

140 LABORATORY AND FIELD EXERCISES

b. Sporangia, Are the inicrosporangia abaxial or adaxial ?

How many sporangia are there on a sporophyll ?
Determine the mode of dehiscence in mature spo-
rangia. Is the abaxial position an advantage in the
dissemination of spores ? Note the growth in length
of the internodes of the strobilus when the micro-
spores are ready for dissemination.

c. Microspores. Study the structure of the microspores.

How is it adapted to dissemination ?

d. Drawings. Draw an abaxial view of a microsporophyll

with its sporangia. Draw a microspore.
3. Pollination, fertilization, and carpotropic movements. If
material is available, study young pine and spruce
cones at the pollination stage.

a. Pollination. What is the position of the strobilus at this

stage ? What is the position of the sporophylls ?

b. Fertilization. Compare the size and position of the

strobili at pollination with that of similar strobili
at the time of fertilization and seed-shedding. Note
the changes in position of the strobili due to carpo-
tropic movements after pollination is effected. Com-
pare the pine and the spruce in these respects.

c. Make outline sketches to illustrate changes in the size

and position of pine or spruce strobili at the polli-
nation, fertilization, and fruiting stages.

GAMETOPIIYTES

1. Male gametophyte. Study the structure of the microspore

and of the male gametophyte from prepared slides.
a. TJie microspore. How does the microspore differ in
structure from an ordinary cell ? Note the charac-
ter of the cell wall, nucleus, and cytoplasm. Draw
a microspore in section.

THE PLANT GKOUPS 141

b. Crametophyte. Study the structures within a germi-

nated microspore. Do you find the two-celled male
gametophyte ? the generative cell ? If possible, find
specimens in which the generative cell has formed
a stalk cell and a body cell.

c. Comparisons. Compare the above structures with the

male gametophyte and antheridia of Selaginella and
cycads. What structures have been lost ? Why are
the lost structures not necessary in pine or spruce ?
To what in the germinated microspore of Selaginella
do the generative cell and the stalk cell of the spruce
correspond ?

d. Draw a germinated microspore and male gametophyte

of the pine or spruce. Summarize answers to ques-
tions under c.

Female gametophyte. Study median long sections of
megasporangia in which the female gametophyte has
formed. Study the section with hand lens and low
power, comparing it with similar sections of cycad
megasporangia.

a. Megasporangium. What structures of the old megaspo-

raugium are found in the section you are studying?
Are there integuments, a micropyle, and sporangial
tissue proper ? Do they have the same relation to
each other as in the cycad ? Is there a distinct
pollen chamber ?

b. G-ametopliyte. Study the gametophyte tissue, the arche-

gonia, and the gametes. What is the nature of the
gametophyte tissue ? What is the structure of the
archegonia ? Have they protective wall cells con-
sisting of neck and venter ? How many of the usual
central cells (namely, neck canal cells, ventral canal
cells, and gamete cells) are there ?

142 LABORATORY AND FIELD EXERCISES

c. Comparisons. How does the gametophyte of the spruce

compare with those of the cycads ? Has there been
any further reduction in the archegonia ?

d. Draw your section and label its parts correctly. Draw

a single archegonium enlarged. Label.

3. The seed and embryo.

a. Cut median long sections of seeds of pine or spruce

which have been softened in water. Study the sec-
tion of the seed which shows the embryo most plainly.

b. Seed structure. Compare the structure of the seed with

that of the ovules just studied. What structures of
the ovule remain in the seed ? What structures are
changed ? From what did the embryo arise ?

c. Embryo structure. Compare the structure of the embryo

with that of seeds previously studied. Do you find
hypocotyl and cotyledons ?

d. Draw your section and label the parts of both seed

and embryo.

4. Seed germination. Study seeds in process of germination

and make sketches to illustrate these phenomena:

a. Exit of the embryo from the seed. What part of the

embryo emerges from the seed first ? Do any parts
remain in the seed ?

b. Exit of the embryo from the soil. How is this effected

and by what parts of the embryo ? Compare this
stage with a similar stage in peas illustrated in
Part I of the text.

c. Adjustment of the embryo to light and soil. Compare

with peas as above.

d. Make appropriate drawings to illustrate a, b, c, above.

5. Life history. Write a graphical life history of the spruce,

indicating the main stages of the gametophyte and
sporophyte generations.

SECTION X. ANGIOSPERMS (DICOTYLEDONS)

SPOROPHYTE

Examine typical dicotyledons in the laboratory and in the
field, and review previous work on dicotyledons such as beans,
mandrake, locust, and elm. Determine as follows the distinc-
tive characteristics of dicotyledons which distinguish them
from Pteridophyta and gymnosperms.

1. Habitat. What is the prevailing habitat of dicotyle-

donous plants of your region ? Be able to name some
mesophytes, xerophytes, and hydrophytes among them.
Is your region typical for the habitat of dicotyledons in
the United States ? Consult the text under Descriptive
Terms for figures and the meaning of terms used below.

2. Habit (geranium and similar dicotyledons).
a. Leaf form and venation.

(1) Compare the leaves of dicotyledons with those

of Pteridophyta and gymnosperms, including
spruces and pines. Are the dicotyledons large
leaved as a group ? What terms describe the
form, margin, apex, and base of the leaves you
are examining? Consult Fig. 208 of text.

(2) Hold a leaf toward the light and study the venation.

Is it pinnately or palmately veined ? Do the veins
end free in the margin (open venation) or are
they united (closed venation) ? See text, p. 415.

(3) /Structure. Review the structure of leaves in Chap-

ter VI of the text in connection witli Fig. 208.

3. Anatomy (herbaceous type, for example, geranium). Re-

view the structure of herbaceous stems in Part I of
143

144 LABORATORY AXD FIELD EXERCISES

the text. Cut thin transverse sections of young and
mature portions of stems of any cultivated geranium or
of a similar herbaceous stem.

a. General features. Do the stem sections of the geranium

correspond to the summary of the herbaceous stem
structure of Salvia ? Do you find tissue layers in
the stem sections of geranium not present in Salviai.
If so, what are they and in what main tissue zone
do they occur, epidermis, cortex, vascular cylinder,
or pith ?

b. Secondary growth by cambiums. Compare transverse

sections cut from young and mature portions of the
stem of a geranium. What differences do you find
between the young and the mature stem sections ?
Locate both the cork and the vascular cambiums,
and the secondary tissues produced by them. Does
the geranium plant produce corky bark ? Examine
both the sections and the surface of old portions of
geranium plants concerning this point.

c. Leaf gaps and leaf traces. Study sections cut through a

node or just below it. Do you find interruptions, or
gaps, in the vascular cylinder where the leaf trace
is given off ? Large branch gaps may also be found,
caused by an outgoing branch. Do you think that
the irregular contour of the vascular ring is caused
in part by leaf gaps and branch gaps ?

d. Tissues of the vascular ring. Compare these with those

of the spruce just studied. Do you find wood rays?
annual-growth rings ? wood parenchyma ? Compare
the ducts with the tracheids of spruce.

e. Storage tissues of lite gerctnhtm stem. Determine the

places where starch is stored in sections treated
with iodine.

THE PLANT GROUPS 145

f. Drawings.

(1) Construct outline drawings of sectors of the young

and old stems of geranium.

(2) Detail the cork cambium and its products.

(3) Detail a small portion of the vascular cylinder of a

section of the older portion of the stem.

g. Long sections. If long sections of geranium are avail-

able, study the tissue of the xylem, noting especially
the structure of the ducts. Draw spiral and dotted
ducts and adjacent tissues.

SUMMARY

Summarize the structure of the geranium stem, modifying the
summary given for Sal via (p. 108 of text), as you think it should
be, to characterize the primary structure and secondary growth
of a geranium stem.

WOODY TYPE (ANATOMY)

1. Review the work previously done on the structure and
growth of trees in Part I of the text (Fig. 55 and
discussion).

a. Comparisons. In what respects is the woody dicotyle-

don better equipped for conducting water and for stor-
ing food than the spruces and pines ? In what respects
does it differ from the herbaceous dicotyledon ?

b. Summarize the distinctive features of the woody dicoty-

ledon which characterize it as the most highly
organized living plant. How is it adapted structur-
ally to perform the functions of support, storage, and
conduction ? Where are the supporting, storage, and
conducting tissues located in trees and shrubs?
How do they differ in this respect from herbs like
Salvia and geranium ?

146 LABORATORY AND FIELD EXERCISES

REPRODUCTION

1. The flower and its parts. Consult the text under repro-
duction and review the floral parts outlined in Part I.
See also Descriptive Terms, at the beginning of Part III
of the text.

a. Structure of the flower. Determine which of the follow-
ing terms apply to the flower you are studying. These
terms are denned under Descriptive Terms, Part III
of the text.

(1) Is the flower you are studying hypogynous, perigy-

nous, or epigynous ? Is it perfect, imperfect, com-
plete, or incomplete ? Is it regular or irregular ?

(2) Are its parts arranged in spiral or cyclic form ? How

many parts are there in each set of protective and
essential organs ? What is the floral plan ?

(3) Construct a ground plan of the flower. Record

the answers to questions asked above under (1)
and (2).

(4) The flower as modified strobilus. Bisect the flower

and receptacle vertically, and note the arrange-
ment of its parts on the receptacle. Does the
flower correspond to a strobilus in the nature
and arrangement of its parts ? Compare with
strobili of spruce. To what does the receptacle
of the flower correspond in a strobilus ? To what
do the stamens, pistil, and perianth correspond ?
What are the ovules and the anthers morpho-
logically ? What fundamental differences exist
between the strobili of the spruce and the flower
you are examining? What new structures are
found in flowers of the angiosperms as compared
with the strobili of gymnosperms.

THE PLANT GROUPS

147

(5) Summary. Summarize in terms of axis, perianth,

sporophylls, and sporangia the similarities and
differences between the strobili of the spruce and
the flower you are examining.

(6) Definition. Write a definition of a flower, consid-

ering the above facts concerning its morphology.

FIG. 25. The lily (Lilium philadelphicum)

A, dissected flower, showing the pistil and stamens: p, parts of the perianth
which have been cut away; s, bases of stamens cut off. J5, floral diagram:
p, perianth, composed of two circles of similar and petal-like parts; s, stamens,
likewise in two circles ; section of ovule case (ovary) shown in the center, com-
posed of three carpels (c) so united as to form three locules containing the
ovules. From Bergen and Davis's "Principles of Botany"

(7) Drawings. Draw a vertical long section of the
flower and label the parts with terms corre-
sponding to those used for strobili of Selaginella,
cycads, and spruce. Draw a ground plan of the
flower (Fig. 217 of text).

148 LABORATORY AND FIELD EXERCISES

b. Morphology and structure of stamens. Study the struc-

ture and mode of dehiscence of the anther. To what
do the filament and anther correspond in the fern,
in Selaginella, and in the spruce? Draw and label
the parts of the stamen in terms of sporophyll and
sporangia.

c. Microsporangia. Study transverse sections of anthers

of the buttercup, mandrake, or a similar dicotyledon.

(1) Sporogenesis. How many microsporangia are seen

in a transverse section of a young anther ? Where
is the sporophyll tissue 'and how is it differen-
tiated ? Is there a supplying vascular bundle and
surrounding cortex and epidermis ? Do the spo-
rangia have the same general tissues as sporangia
of ferns and microsporangia of Selaginella, cycads,
and spruce ? Are there wall cells, tapetum, and
sporogenous cells, or spore mother cells, in each
microsporangiurn of an anther ? Note carefully the
cell structure, including cytoplasm, nucleus, and
chromatin, of the cells in each of these layers.

(2) Drawing. Outline the entire section. Detail the

cellular structure of one microsporangium, show-
ing the cells of the tapetum and the sporogenous
cells magnified. Label correctly in terms usually
applied to microsporophylls and microsporangia.

(3) Spore dissemination. Study transverse sections of

mature anthers. What changes have occurred in
the microsporangia during sporogenesis ? How
many microsporangia unite to form one anther
sac ? How is dehiscence provided for ? Study the
wall cells of the anther sacs. Is the layer beneath
the epidermis structurally adapted for opening
the anther sacs for spore dissemination ? What

THE PLANT GROUPS 149

is the structure of these cells and how would
they work in opening and closing the anther sacs ?
(4) Microspores. Xote the structure of the microspores
or pollen grains. What is the nature of the outer
wall, or extine ? Outline one half of your section
and detail the cell structure of wall cells and
microspores on a part of the section. Label
correctly.
d. Pistil and fruit.

(1) Study the pistil, noting particularly the nature and

extent of the ovary, style, and stigmatic surface.
Is each pistil simple or compound ? Observe the
megasporangium, or ovule, best seen in mature
fruiting pistils. Compare* the megasporophyll
and sporangium with that of Caltha in the text.

(2) Drawing. Draw the pistil so as to show the stigmatic

surface magnified and the relation of megasporo-
phyll and megasporangium.

(3) Fruit. Make a drawing to illustrate the nature and

parts of the fruit.

CAP SELL A (SHEPHERD'S PURSE)

Study the flower and inflorescence of the shepherd's purse as
outlined above under Reproduction, 1, a (see Fig. 251, p. 400,
of text). Make the following special study of pistil, megaspo-
rangium, megaspore, and embryo sporophyte. Consult the text
discussion of Capsella (p. 345 of text, and Fig. 203).
1. Pistil.

a. Study young and mature pistils on the inflorescence
of Capsella and determine the relation of stigma,
style (if present), and ovary. Is the ovary simple
or compound ? How many placentae are there and

160 LABOR A TOE Y AND FIELD EXERCISES

how many rows of ovules or megasporangia ? Deter-
mine this point by gross studies of the external
features of the pistil, and by examining gross trans-
verse sections of the pistil made with a scalpel or
safety-razor blade.

b. Draw a lateral view of the pistil and a transverse section
of the ovary. Label the parts in terms of megasporo-
phylls (carpels) and megasporangia (ovules).

2. Megasporangia, or ovules. Dissect out a considerable

number of ovules from both young and mature ovaries
on a slide in a drop of water. Eemove half of the
ovules to a second slide and mount in a weak potash
solution. Cover and study your two preparations to
determine the following points :

a. Parts of the meyasporangium, or ovule. Observe the

funiculus, ovule proper, integuments, and micropyle.
The embryo sac may often be seen in outline in
specimens treated with potash. Compare the form
of young and mature sporangia and note the gradual
curvature of the entire sporangium and spore as the
ovule matures.

b. Embryo sporophyte. The embryo can often be seen, in

specimens bleached in potash, lying above the micro-
pyle. It may be obtained free on the slide by slight
pressure on the cover glass.

c. Drawings. Draw the ovules of Capsella to show as

many of the above structures as you have been able
to demonstrate, including the embryo and its parts.
Name all parts correctly, consulting the text figure
and the description of parts there represented.

3. Female gametophyte and sporophyte of Capsella. Study

the female gametophyte, embryo sac, and sporophyte
in prepared slides of ovaries of Capsella. Work out as

THE PLA^T GftOUPS 151

far as possible the cellular structure and relations of the
following structures :
a. Megas2)orangia and female gametophyte.

(1) If sections are available, study the female gameto-

phyte, consisting of the egg apparatus, polar nuclei,
and antipodal cells. If such slides are not avail-
able, read the history of the development of the
megaspores in angiosperms in the text and com-
pare the history with that of megaspores in
Selaginella and the spruce.

(2) Drawing. If sections are studied, draw and label

the parts of the megasporangium, embryo sac,
and gametophyte cells.

PART III. THE SPRING FLORA

SECTION XI. FIELD WORK (DICOTYLEDONS)

A. TREES AND SHRUBS
A METHOD OF RECORDING FIELD OBSERVATIONS

In the following outline for the study of trees in the field
the same general plan is followed as in the description of typi-
cal species of willows, oaks, and maples in the text.

The directions should usually be followed for the study of
one typical species in each family until the student is familiar
with the methods employed in such work. Additional species
should then be worked out by the students independently.

A convenient form for recording field observations and labo-
ratory studies on trees and shrubs is submitted below in the
form of what are termed Species Eecord and Family Record.
If this plan is adopted, the record of the initial species studied
in each family should be entered, as indicated in the outline,
by checking, in the blank spaces following the terms employed,
each term, or character, that applies to the species being
studied. Outline sketches should also be made after such a
plan as that indicated under Figs. 10, 11, and 12, pages 20~23,
of text. See also the figure of the Carolina poplar (Populus
deUoides) (Fig. 26).

It is convenient for class use to have the Species Record
(p. 156) and the outline for Figures (p. 157) printed on two
sides of a single field sheet. These field sheets can then be given
to each member of the class for recording the results of field
and laboratory work. The Family Record (p. 158) can be used
in a similar manner, the outline for several species being printed
on one sheet with the familv characteristics at the end.

156 LABORATORY AND FIELD EXERCISES

SPECIES RECORD
I. ANALYSIS

Family...

Scientific name

Common name ...

II. CHARACTERISTICS

fa. Local: mesophytic xerophytic hydrophytic.

t: U Geographical

2. Habit: erect spreading large: small medium __

a. Bark : color, smooth, flaky, furrowed, etc.

(1) Trunk

(2) Branches .

b. Twigs : color stout slender smooth hairy..

c. Buds : size, color, smooth, hairy, resinous, etc.

(1) Terminal

(2) Lateral

d. Leaf: form margin size phyllotfixy

simple compound netted parallel pinnate

palmate leaf scar

e. Lenticels: color shape size Drawing

3. Reproduction

a. Inflorescence : determinate indeterminate kind

b. Flower characters: hypogynous perigynous epigynous..

perfect imperfect regular irregular complete...

incomplete

c. Pollination features

(1) Close cross odor nectar color irregular...

monoacious dioecious.. .polygamous protandrous.

protogynous heterostylous

(2) Means: wind insects contact gravity water..

4. Distinctive recognition characters

f>. Commercial importance

THE SPRING FLORA

157

Stem section

FIG. 26. Vegetative and reproductive parts of a poplar
Designed to indicate the method of recording observations on trees

1. Twig, buds

Lenticels and scars
Stem section

FIGURES

2. Leaf characters

3. Inflorescence, flower

Long section of flower, pollination

4. Fruit and seed

Fruit class

Seed distribution.

158 LABORATORY AND FIELD EXERCISES

FAMILY RECORD

Fill in the analysis and the distinctive characteristics of each species
of any given family under I and II.

Fill in the family characteristics common to all species observed
under III.

Use habitat, habit, and reproduction as the basis for your characteri-
zation of the family.

I. ANALYSIS

Family .

Scientific name

Common name

II. DISTINCTIVK CHARACTERISTICS

IIabitat._.

Habit.

Reproduction..

II F. FAMILY CHAI

[ACTKKISTICS

THE SPKING FLORA 159

GYMNOSPERMS (SOFTWOOD TREES)

THE PINE

1. Habitat.

a. What is the nature of the habitat of the pines of your

region as regards soil, drainage, and climate ? Do
pines grow best on lowlands or on well-drained
slopes and uplands? What is the distribution of
pines in the United States ? What is their natural
habitat as regards soil and climate ? Are they
mesophytic or xerophytic in general habit ? How
do you explain the apparent discrepancy between
habitat and habit in the pines ? Consult the text,
manuals, and assigned readings on the above points.

b. Summarize the above points in your notes under the

following headings:

(1) Habitat : local geographical

(2) Habit : mesophytic xerophytic

(3) Discrepancy between habitat and habit

2. Habit.

a. Form and body plan of the pine tree.

Eeview the text discussion of the body plan and
mode of growth of the pine tree in Part I of the text.
Consult also Fig. 10. Be able to account for the
erect conical form, the excurrent trunk, and the
false whorls of branches of common pines. Why
is the trunk excurrent ? What determines the cone-
like form of the entire tree? How do the false
whorls arise ? Is the entire leafage well exposed to
light ? What factors determine this light exposure ?
Is it due to the form of the tree, to tropisms of
leaves and branches, or to other factors ?

160 LABORATORY AND FIELD EXERCISES

b. Summarize the above points under body plan, growth

methods of buds and branches, and tropistic responses
of leaves and branches.

c. Long and dwarf shoots.

Long shoots in pines are the main branches and
twigs; dwarf shoots are the small structures from
which the needle leaves arise in clusters of two,
three, or five.

(1) Study long and dwarf shoots of pines in the field.

Do the dwarf shoots arise in a spiral or cyclic
manner from the long shoots ? Study the naked
portions of a twig where the scars of dwarf
shoots show their former arrangement. Observe
the scalelike leaves on long shoots. What is
the arrangement of the scale leaves on the long
and dwarf shoots ? Do dwarf shoots arise from
the axils of scale leaves like ordinary branches ?

(2) Buds and growth. Determine the nature and posi-

tion of buds on long shoots. Are there lateral
buds ? Do dwarf shoots arise from lateral buds ?
Determine the age of a terminal portion of a long
shoot by the rings of bud-scale scars.

(3) Draw a small portion of a long shoot from which

dwarf shoots have fallen, to show their arrange-
ment on the long shoot and their relation to the
scale leaves. Draw the terminal portion of a long
shoot to show the shape and character of buds,
dwarf shoots, and needle leaves. It is best not
to draw more than one or two dwarf shoots on
the terminal shoot.

d. Strobili, or cones (see Fig. 233, p. 379, of text).

(1) Ovuliferous strobili. Observe the position of the
reproductive cones on single long shoots and on

THE SPPvIXG FLORA 161

the tree as a whole. Is their general distribution
and their individual attitude (due to tropistic
response) such as to facilitate the distribution of
seeds? Search for the seeds. What adaptation
have they for dissemination ? What is the plan
of arrangement of the cone scales on the cone
axis ? Does it correspond to the body plan of
the tree?

(2) Young strobili. Do you find strobili of different ages

on the pine ? Note the position of young strobili
How long does it take pine cones to mature ?

(3) Staminate and ovulate strobili Do you find both

staminate and ovulate strobili on the same tree?
The staminate cones can only be found in late
spring, since pollination occurs in pines about
the first of June.

(4) Make simple sketches to illustrate the positions

on the branches and the attitudes assumed by
strobili of different ages and kinds.

ANGIOSPERMS (HARDWOOD TREES)

FIELD STUDIES
1. Habitat.

a. Local habitat. Study the conditions under which the

species grows in the local habitat, including the soil,

water supply, and drainage conditions. Which one

of the following habitats does it occupy ?

(1) MesopJiytic habitats. Does it live in typical upland

mesophytic conditions or is it found on lowlands

such as flood plains, river banks, and the borders

of lakes and ponds ? Note that ornamental trees

are frequently not growing in their natural habitat.

L.VBOKATOEY AND FIELD EXEK< ISES

(2) Xerophytic habitats. Does it occupy exposed dry

cliffs and hillsides, sandy regions, or mountain
sides without adequate water supply ? Is it
found in marshes or swamps which are physio-
logically dry on account of the condition <>f the
bog water ?

(3) Hydrophytic habitat. Does the species live in soil

flooded or saturated with water ?

b. Geographical habitat and <K*tnb*tion. Determine the
natural habitat and distribution of the species on
the American continent by means of manuals and
maps. Consult maps and descriptions in Hough's
" Handbook of North American Trees " if this work
is available. Consult the text, Fig. 223, and the
discussion of trees and shrubs.
2. Habit.

a. Is the species being studied mesophytic, xerophytic,

hydrophytic, or tropophytic in habit ?

b. Size and form. Is it large or small as compared with

other trees in the region ? Is it erect or spreading in
habit ? Is there a single excurreut trunk or does the
trunk divide above into two or more secondary axes ?

c. Body plan and development. Review the text discus-

sion in Part I on the development of trees and its
relation to body plan, bud growth, and pruning in
the spruce and elm. See Fig. 11 of text.

d. Study the relation of the following four main factors,

which determine the form of a tree, to the ultimate
form assumed by the species you are observing, as
indicated below:

(1) Body plan. Is the species you are studying cyclic
or spiral in leaf and bud arrangement ? If spiral,
is the phyllotaxy J, f , f , or a higher fraction ?

THE SPUING FLOEA 103

(2) Buds and growth. Is there a main terminal bud,

as in the pine, producing a single excurrent
trunk, or is the main terminal bud superseded
by one or more laterals which produce a sub-
division of the trunk above ? How many lateral
buds produce strong shoots each season? Consult
the growths of the last four or five years on the
terminal portions of branches. How many buds
remain latent or produce weak lateral twigs
each season ?

(3) Pruning •#'•••*#. Determine the effect of natural

and artificial pruning on the form of the tree.
Do small unsuccessful twigs or shoots continue
to form a part of the crown of the tree or is
the crown composed wholly of the more vigorous
shoots of past seasons ?

(4) Adju*tmt'ntx t" tie- i-nrir»nment by tropisms. Observe

the position of branches in the upper, middle, and

lower thirds of the crown. Is the form of the

branches and their position "with reference to

the main or to the secondary axes different in

the above portions of the crown ? Is the response

mainly to light or to gravity ? Do the positions

assumed by the branches secure a better light

exposure for the leaves and a better position for

the dissemination of fruits and seeds ?

e. Baric. Compare the bark on the main trunk and its

branches. Is there a marked difference in color, and

in smoothness or roughness, between the bark on

the branches of the upper and middle portions

of the crown and that of the main trunk and its

larger subdivisions -? Is the difference such as to

form a distinctive characteristic of the species under

CANOtf BIRCH BEECH

Chalky white horizontal lines Smooth, qr&y, mettled

n

CHESTNUT WHITE OAK

Long eorvfluent ridges Long narrow yiat scales

UMBRELLA TREE
Smooth, blister like

SASSAFRAS
Rough broken ridges

Three kinds of bark — smooth, ridged, and scaly. (After Mathews)

THE SPRING FLOKA 165

examination ? Is the bark on the trunk rough or
smooth, furrowed or flaky, corky or indurated, in
texture ?

f. Leaves and the liyht relation. Observe the form and

texture of the leaves and their arrangement with
reference to light. Have they distinct differences in
form and arrangement which facilitate lighting by
the sun ? Have they distinct organs or methods for
tropistic response which expose them favorably to
light ? Do they form mosaics ?

g. Outline sketch. Draw an outline sketch, similar to the

figures of the elm in Part I, to illustrate the above
points relative to habit. For the first studies the
student may well draw a series of figures, similar to
Fig. 11, a-f, to show the relation of body plan, growth,
and pruning to the ultimate form and leaf exposure
of the tree.

3. Reproduction. Study the inflorescence, flowers, fruits, and
seeds of the species you are observing, as follows :

a. Inflorescence. Are the flowers solitary in the axils of

leaves or are they borne in clusters ? In the latter
case determine the kind and the general structure
of the inflorescence. Consult the text description
of the kinds of inflorescence under Descriptive Terms.

b. Floivers. Study the structure, floral plan, and pollina-

tion features of the flowers under the following
headings, determining which terms are applicable to
the species being studied. Consult the text under
Descriptive Terms.

(1) Structure. Are the flowers complete or incomplete,
perfect or imperfect, regular or irregular in form ?
Are they hypogynous, perigynous, or epigynous
in the relation of their floral parts ?

166 LABORATORY AND FIELD EXERCISES

(2) Floral plan. Are the flowers spiral or cyclic in the

arrangement of their parts on the receptacle?
Are they on the plan of 3, 4, or 5 ?

(3) Pollination features. Study the adaptations, if any,

which the flowers possess for securing pollination,
as well as the means or agents by which pollina-
tion is secured. Be able to designate those of the
following terms which apply to the flowers under
observation. Are they close-pollinating, cross-
pollinating, or self-pollinating ? Have they color,
odor, nectar, or any other attractive features for
securing insect pollination ; that is, are they ento-
mophilous ? Are they adapted for wind pollina-
tion ; that is, are they anemophilous ? If so, be
able to state the adaptation.

c. Fruit and seed. Study the nature of the fruit and its

origin from the pistil. Are there special devices for
seed and fruit dissemination ? Do you know of any
wild tract which has been seeded by fruits dissemi-
nated from near or distant trees of the species you
are studying ? In what places in your region are
trees most successful in producing offspring by seed
dissemination ? In what places in other regions ?
Considering the large number of seeds produced by
each tree, why are trees not more abundant ?

d. Drawings. Make sketches to illustrate the structure,

floral plan, and pollination features of the flower. Draw
the fruits and label all parts correctly. These draw-
ings can be made separately or with other drawings
of the species, as in the poplar, on the Species Record.
4. Anatomy. Cut gross transverse sections of twigs or small

branches. Observe the nature of the wood, phloem,

and bark.

THE SPRING FLORA 167

a. Is the wood porous or dense ? ring porous (with pores

in the spring wood) or diffuse porous (with pores in
both spring and summer wood) ? Is the wood hard or
soft ? Do you think it would be commercially valua-
ble ? Draw. See drawings of the poplar for a model.

b. Commercial importance. Find out if possible the com-

mercial importance of the wood in the species being
studied. See figures and discussions in the text on
the above points.

5. Distinctive recognition characters. What distinctive char-

acters would enable you to recognize the tree you are
studying in the field ? Are there distinctive characters
of the species other than gross external ones ? Summarize
the distinctive characters under the record of results.

6. Analysis. Analyze the species, to determine the family

to which it belongs and the scientific and common
species names. Record the family, genus, and species
on the Species Record.

B. HERBACEOUS DICOTYLEDONS
A METHOD OF RECORDING FIELD OBSERVATIONS

The method submitted below of recording field observations
for herbaceous plants is similar to that indicated for trees
and shrubs. The plan may be followed for a part of the field
work if desired, until the student is familiar with methods of
observing and recording results. It should not be carried to
the point of becoming mechanical. After the first detailed
studies have been recorded on the Species Record form, teachers
may prefer to use the Family Record exclusively. Loose-leaf
sheets for species and family records are convenient and are
used by the author in field work. These can be printed by a
local printer from the outlines in these exercises.

168 LABORATORY AND FIELD EXERCISES

SPECIES RECOKD
I. ANALYSIS

Family

Scientific name

Common name Locality

II. CHARACTERISTICS : monocotyledon dicotyledon

1. Habitat: mesophytic xerophytic hydrophytic

2. Habit: mesophyte jxerophyte hydrophyte

a. Stem : caulescent... branching... height. acaulescent___

erect horizontal prostrate climbing rhizome

bulb.._corm___tuber__.
Tropisms : pro dia apo

b. Leaves: large small medium__^__simple compound

(1) Venation : netted parallel pinnate palmate

(2) Position : radicaL__cauline_._spiral.._cyclic.— decussate

(3) Orientation : horizontal vertical oblique rosette____

mosaics

(4) Light tropisms: pro dia apo

c. Roots: primary __. lateral ___fibrous...fleshy___ surface___deep.__.

Gravity tropisms : pro dia apo

3. Reproduction

a. Inflorescence : solitary determinate indeterminate

kind..

It. Flower characters: hypogynous perigyiious epigynous

perfect imperfect regular irregular

c. Pollination features

(1) Cross : odor.____nectar____color____irregular____unisexual

(2) Close: odor nectar color regular bisexual

(3) Special features: protandry...protogyny.___heterostyly._.

(4) Means : wind insects contact gravity water.

4. Distinctive characters

THE SPRING FLORA 169

FIGURES

1. Stem, root, leaf •>• Inflorescence and flower

Ihihit and tropisms Long sections and ground plan

Pollination features

Detail : anther dehiscence,
carpels, placenta;, ovules

2 Stem section

Epidermis, cortex, vascular
cylinder, stem, pith

4. Fruit and seed

Fruit class

Seed dispersal

170 LABORATORY AND FIELD EXERCISES

FAMILY RECORD

Fill in the analysis and the distinctive characteristics of each species
of any given family under I and II.

Fill in the family characteristics common to all species observed
under III.

Use habitat, habit, and reproduction as the basis for your characteri-
zation of the family.

I. ANALYSIS

Family

Scientific name

Common name

II. DISTINCTIVE CHARACTERISTICS

•
Habitat....

Habit..

Reproduction.

III. FAMILY CHARACTERISTICS.

THE SPKING FLOKA 171

RANUNCULACEAE (BUTTERCUP FAMILY)
BUTTERCUP OR HEPATICA

Select one or more species of buttercups for field study.

1. Habitat. Determine the following facts concerning the

habitat of buttercups :

a. Soil, water supply, and drainage of their habitat at
different seasons of the year.

&. Plant associates. With what other plants are the
buttercups associated ? Does their association with
these plants affect their relation to light, soil mois-
ture, and soil food ? Would these relations be different
at different seasons of the year ? Be able to explain
the relation of this association to the spring flower-
ing period of buttercups or hepaticas. *

2. Habit. Use Ranunculus fascicularis for this study if it

is available. Other species may be used. Study plants
of Ranunculus fascicularis in the field ; remove some
plants from the soil with a trowel so as not to injure the
root system, and observe as follows :

a. Stem, roots, and leaves. Note the origin of the roots

and leaves from the short (acaulescent) stem. Are
the leaves cyclic or spiral in arrangement ?

b. Light relation. What position do the leaves assume

with reference to light? Are they advantageously
placed ? Is this favorable placing of the leaves a re-
sultant of both body plan and adjustment by tropisms,
as in peas, dandelions, and trees studied earlier in the
text ? Be able to explain.

c. Soil relation. Study the root system of Ranunculus

fascicularis. What different kinds of roots do you
find ? What is the apparent function of each ? At

172 LABORATORY AND FIELD EXERCISES

what season do the different kinds of roots originate?
Note the place of origin of each kind of root from
the stem in young and mature plants. Do they
originate at the same time and in the same manner?
Save your specimen for a drawing in connection
with the seasonal life of the buttercup.
d. Summarize the above facts relating to habitat and
habit in your notes or on a Field Species Record.

3. Reproduction.

a. Flower scapes. Note the origin, and the position

assumed by the flower scapes. What outside forces
act as stimuli in orienting the flower scapes ? Are
they adjusted so as to expose the flowers and fruits
properly for pollination and seed dissemination ?

b. Flowers. What is the floral plan of the flowers luider
* observation ? What are the adaptations for pollination ?

Is the flower self-pollinating, close-pollinating, or
cross-pollinating? Note any special devices for
pollination.

c. Eecord your observations in the Species Eecord under

Pollination features. Construct suitable drawings to
show the pollinating device.

d. Fruit and seeds. To what class of fruits do the fruits

of the plants you are observing belong ? Consult
the text, under Descriptive Terms in Part III, and
Fig. 221. Eecord your results by drawings and terms
giving the kind and class of the fruit.

4. Seasonal life. Are the buttercups and hepaticas annual,

biennial, or perennial plants ? What advantage is it to
them that they flower in spring ? Consider this point
in connection with their plant associates and their
habitat. Is their active food-building, like their repro-
ductive functions, carried on mainly in the spring?

THE SPRING FLORA 173

What is the function of the fleshy roots of Ranunculus
fasdcularis in its seasonal history ? Construct figures
corresponding to those of the white sweet clover
(Fig. 65) and the dandelion (Fig. 24) in Part I of the
text, to express the habit and the seasonal life of
Ranunculus fascicularis or the other species observed.
Summarize these facts in your notes or in the Species
Record.
5. Analysis. Analyze one or more species of Ranunculaceae.

FLORAL MODIFICATIONS IN RAxrx<TLACEAE:
COLUMBINE (AQUILEGIA)

1. Compare the columbine (AquUegid) with typical Ranun-

culaceae as regards habitat, habit, and reproduction,
noting the variations in the columbine from buttercups
and the marsh marigold.

2. Reproduction.

a. Pollination. What floral arrangements facilitate polli-
nation ? Are the flowers protandrous or protogy nous ?
Is self-pollination possible? Make a sketch to illus-
trate the method of pollination in Aquilegia and
compare it with Fig. 250. Summarize the devices
for securing cross-pollination which obtain in the
columbine.

l>. Fruit and seed. Compare with that of the buttercup.
What is the method of shedding and disseminating
seed ?

VIOLACEAE

1. Habitat and habit. Study the habitat and habit of the

Violaceae in the same manner as that outlined for

the buttercup. What are their plant associates ? Would

• violets have as good an opportunity for flowering and

174 LABORATORY AND FIELD EXERCISES

setting seed in the summer and autumn as in the
spring? Be able to explain this point.

2. Seasonal life.

a. Compare the seasonal life of violets and buttercups.

What are the principal activities of the violet plant
in spring, autumn, summer, and winter ? What por-
tions of the plant are active at each season? Consult
the text, Part I, on seasonal life.

b. Summarize the above facts relating to the seasonal

history of violets.

3. Reproduction. The flower and its modifications for secur-

ing pollination.

a. Study the parts of the flower and their modifications.

What modifications do you find in the perianth and
the essential organs ? Remove the parts of the peri-
anth and observe their form and structure. Note
the relation of the stamens to the perianth and
to the pistil.

b. Cut a transverse section across a flower in the region of

the ovary. Study the section and construct a ground
plan of the violet flower which will show the relation
of the parts of the perianth and the essential organs.

c. Pistil and stamens.

(1) Dissect away all of the petals except the lower one

with the spurlike nectary. Examine the stigma
and anthers with a hand lens. Where is the stig-
matic surface ? How is it related to the anthers
and to the canal leading to the nectary ? Where
is the pollen shed ?

(2) Bisect a flower longitudinally and study the above

relation of pistil, stigma, and anthers to the nec-
tary and the lower petal. Consult Fig. 253 of
text and the discussion on pollination.

THE SPKING FLOBA 175

d. Pollination. How is pollination secured through the

agency of visiting insects ?

e. Drawing. Draw a median long section of the flower

to show the relation of the floral parts which insure
cross-pollination. Label accurately.

f. Summarize under the following headings the mechanisms
of the violet which adapt it for cross-pollination.

(1) Perianth modifications.

(2) The relation of the pistil, stigma, and anthers.

(3) The anther tube and pollen shedding.

(4) The relation of a visiting insect to the flower in

securing nectar.

4. Analysis. Analyze one or more species of violets, record-
ing the family, scientific, and common name.

CRUCIFERAE

Study the habitat and habit of some of the important
members of the cruciferous family.

1. Habit.

a. Stem and roots. What are the distinctive features of the

stems and roots of the Cruciferae that you are study-
ing ? Are there characteristics which are unusual ?
What is the nature of the juice or sap ?

b. Leaves. Observe any distinctive characteristics of leaves

in members of the family under observation.

2. Reproduction.

a. Determine the nature of the inflorescence and the

structure of the flower.

b. Drawings. Draw a ground plan of a flower of some one

of the Cruciferae. Draw a median long section of a
flower to show the relation of the perianth, stamens,
and pistil.

176 LABORATORY AND FIELD EXERCISES

c. Pollination.

1. What are the special devices for securing pollina-

tion ? To determine this point study flowers of
different ages and note the relation of the differ-
ent lengths of stamens to the stigmatic surface.
Does this relation change as the flower matures ?

2. Construct outline drawings to illustrate any devices

for self-pollination, close-pollination, or cross-
pollination which you discover.

d. Fruit and seed. Study and classify fruits 011 one or

more species of the Qruciferae. Construct a diagram
of the fruit to show its method of dehiscence.

3. Seasonal life. Study the seasonal life of some of the more

important cultivated species of the Cruciferae in the
field and by consulting text references. See, for example,
Bailey's "Encyclopedia of Horticulture," Robbins's
" Botany of Crop Plants," and Sargent's " Plants and
their Uses."

a. Are the members of the family mainly annuals, bien-

nials, or perennials ? How do the biennials and peren-
nials pass the winter ?

b. Construct a series of diagrams to illustrate the seasonal

life of one important commercial variety of the Cru-
ciferae. Consult the text, Part I, on the seasonal life
of the bean, clover, and locust.

4. Commercial importance. Make a list of the more important

species of Cruciferae and indicate the use of each species.

5. Analysis. Analyze species of the Cruciferae^ recording

the family, species, and common name.

6. Distinctive characteristics. Summarize under habit, repro-

duction, and seasonal life. The above data may be
recorded on a Species Eecord or a Family Eecord sheet
if desired.

THE SPRING FLORA 177

LEGUMINOSAE

See Pollination devices in papilionaceous flowers in Part I
of the text, and the seasonal history of the bean and the white
sweet clover. See also previous laboratory work and drawings
011 the locust and sweet pea. Study the distinctive recognition
characters of representative species of Leguminosae in the field
and be able to summarize them under the following headings :

1. Habit.

a. Stems. Are the stems all herbaceous in character or
are there some common trees and shrubs belonging
to the family ?

./>. Leaves. What are the distinctive structural and physio-
logical features of the leaves of all Leguminosae
which distinguish them from other families of plants
with which you are familiar ? Study the leaves of
several species and their reactions to light. Are
they simple or compound ? Have they special motor
organs ?

c. Roots. Dig up the root system of the common red
clover, of the pea, or of the bean. Do you find en-
largements on various parts of the root system in the
form of nodules? These nodules contain the nitrogen-
gathering bacteria which enable these plants to use
free nitrogen from the soil. Observe also the extent
of the root system as compared with the leaf system.
Is the root surface exposed to the air ?

2. Reproduction.
a. Flowers.

(1) Structure. Have the'flowers of the family a common
structure, floral plan, and form ? Note any floral
modifications from the usual type of the flowers
of the family illustrated in the text.

178 LABORATORY AND FIELD EXERCISES

(2) Pollination. Are all of the flowers of the family
cross-pollinated ? Compare the methods of pollina-
tion in peas, clovers, and vetches.

b. Fruits and seeds. Do you find all fruits in the family

similar to that of the pea, bean, and locust ?

c. Summary. Summarize the distinctive characteristics of

the Leguminosae under the above headings and in
the order indicated in the directions. This may be
done on a Family Record sheet if desired.
3. Economic importance. Study species which are of economic
and commercial importance in the family as indicated
under the Cruciferae. List several important commer-
cial species and the particular uses of each species.

SUPPLEMENTAKY STUDY

Each student should be assigned some species of the Leyuminosae,
such as the common red clover, vetch, or lupine, for individual
study and report. The report should include drawings to show
the following structures :

1. Habit.

a. Leaves. Observe the mechanism for adjustments of leaves

to light, including the position of leaves in the morn-
ing, at noon, and at night. Make a brief statement of
the mechanism of movement in leaves with pulvini.

b. Roots. Drawings of roots with tubercles.

c. Reproduction. Observe and record the following facts

relating to the flowers, fruits, and pollination :

(1) The structure of the flower and pollinating mechanisms.

(2) Fruit and methods of seed dispersal.

(3) A brief discussion of the pollinating mechanism and

of seed dispersal in such a species as the common
red clover.

d. Analysis. Analyze two or more species of

and record as usual.

THE SPRING FLORA 179

ROSACEAE
STRAWBERRY (FRAG ARIA] OR POTENTILLA (CINQUEFOIL)

1. Habit.

a. Observe the general habit of the strawberry, noting
the relations of stem, leaves, and roots.

2. Reproduction.

a. Vegetative reproduction. Study the origin of the run-
ners, and their general morphology. Do they origi-
nate, like stems, from the axils of the leaves? Have
they nodes, internodes, and leaves? How do the
runners produce offspring ?

b. Construct a diagram to illustrate the origin, morphol-

ogy, and mode of reproduction by runners.

c. The flower. Study the floral plan and structure of

the flower. Be able to construct a ground plan of
a flower.

d. Pollination features. Read the text on Fragaria and

consult the figures. Determine the method of polli-
nation in the species or variety that you are study-
ing. Construct figures to illustrate the method of
pollination observed.

e. Flower and fruit.

(1) To what class of fruits does the strawberry belong ?

What are its parts and how are they related to
the similar parts of the flower ? Bisect a fruit
lengthwise and compare it with a similar section
of the flower. Be able to name corresponding
parts in the flower and the fruit.

(2) Drawings. Draw a median vertical section of the

flower and fruit of the strawberry and name
the corresponding parts.

180 LABORATORY AND FIELD EXERCISES

THE CULTIVATED APPLE (MALUS)

1. Habit.

a. Form and body plan. Be able to account for the form

and leaf display of the apple tree, as for the elm
and pine in Part I of the text. Determine this on
the hasis of body plan, bud growth, pruning effects,
and adjustments of leaves and branches by tropisms.

b. Suds and fruit spurs.

(1) Where are the fruit-bearing branches (fruit spurs)

located on«the main branches of the tree ? Search
for bud-scale scars, and leaf and fruit scars on
the short fruit spurs or spur shoots. The fruit
scar is usually a large, circular scar surrounded
by smaller scars representing the scars of un-
developed fruits in the same flower cluster. How
many years old are the spur shoots that you
are examining?

(2) Draw a terminal shoot of an apple branch, indicat-

ing the position, form, and markings of the
spur shoots.

2. Reproduction.

a. Inflorescence. To what class of inflorescence does that

of the apple belong ?

b. Flower structure. Is the flower epigynous, perigyuous,

or hypogynous ? Determine the relations of recep-
tacle, perianth, stamens, and pistil.

c. Pollination. Determine the method of pollination in

the apple flower. Is the method of pollination of
economic importance ? Be able to explain this point.

d. Flower and fruit.

(1) Study transverse and long sections of the fruit.
What parts of the flower are represented in the
fruit? What parts are lacking? What parts

THE SPRING FLORA 181

have increased in size and what parts have
become otherwise changed ?

(2) Drawings. Draw a transverse and a vertical median

section of the flower of the apple, magnified
sufficiently to show clearly the parts of the ovary
and the ovules.

(3) Discuss briefly the parts of the flower which enter

into the formation of fruit, and the changes
undergone during fruit formation.

3. Reference readings. Consult various texts concerning the
history and reproduction of the cultivated strawberry
and apple. Eobbins's " Botany of Crop Plants " is
particularly valuable as a reference on the above points.
See also Bailey's ''American Horticulture."

SUPPLE ME NT A R Y STUDY

1. If time allows, the student should study the flowers and
fruits of the wild rose, cherry, raspberry, and blackberry, in order
to acquaint himself with the methods of fruit formation in
these important fruit-bearing species.

2. Commercial varieties. Study and record important commer-
cial species and varieties of the Rosaceae, as for the Cruciferae
and Leguminosae.

COMPOSITAE

THE YARROW (ACHILLEA)

Read the text discussion of the inflorescence, flowers, and
fruits of the common yarrow and confirm the points there
discussed.

1. Inflorescence. To what class of inflorescence does that of
the yarrow belong ? Bisect the inflorescence vertically
and study its parts. What is the form of the axis of
inflorescence ? What structures make up the involucre ?

182 LABORATORY AND FIELD EXERCISES

To what structures do these parts of the involucre of
the yarrow correspond in a raceme or spike ? How are
the flowers of the inflorescence differentiated ? Is there
any conceivable advantage in this differentiation ? Does
each separate flower spring from a separate bract?
Compare the parts of the inflorescence of the yarrow
with that of a raceme.

2. Flowers.

a. Central tubular flowers.

(1) Study these flowers with a hand lens and deter-

mine ttie relation of calyx, corolla, stamens, and
pistil. Is there anything corresponding to a calyx?

(2) Are the flowers hypogynous, perigynous, or epigy-

nous ? Are they perfect or imperfect ? complete
or incomplete ? regular or irregular ?

(3) Note the bract subtending each flower.

b. Outer ray flowers. What is the function of the ray

flowers ? Compare these with the central tubular
flowers. Are the essential organs present ? How is
the corolla modified ?

3. Pollination. Split the corolla of young and mature

tubular flowers with dissecting needles so as to
expose the stamen tube and style. Compare the
young and old flowers as follows (consult the text
figure) :

a. Note a stage where the upper portion of the style

is still within the anther tube. Where are the
stigmatic surfaces ? Is the pollen being shed ? Can
it reach the stigma ?

b. Observe a slightly older stage. Are the stigmatic

surfaces exposed ? Can they be self-pollinated ?
Are the flowers of the yarrow protandrous or
protogynous ?

THE SPRING FLORA 183

4. Fruit and seed. To what class of fruits does that of the

yarrow belong ? Is there any definite device for seed
and fruit dispersal ?

5. Summary. Summarize the distinctive features of the

yarrow, as a representative of the Oompositae, under
the above headings ; namely, inflorescence, flowers, polli-
nation, and fruit. Give the distinctive features only.

6. Analysis. Ascertain the scientific name of the yarrow by

means of a manual.

DAXDELIOX (TARAXACUM)

1. Habit and adjustments by tropisms.

a. Study the plants of the dandelion in flower and deter-
mine the relations of its organs to each other and to
the environment. Consult the text discussion (Part I)
concerning the adjustments of the leaves, flowers,
and fruits for photosynthesis, food absorption, polli-
nation, and seed dispersal. Confirm these points by
field observations.

2. Reproduction.

a. Vegetative reproduction.

(1) Dig up a number of plants of the dandelion. Is the

stem simple or branched ? Do you discover how
a single plant may give rise to a group of offspring
by vegetative reproduction ?

(2) Construct outline figures to illustrate what you find

in this respect.

b. Inflorescence and flowers.

(1) Compare the general structural parts of the inflores-
cence and flower of the dandelion with that of
the yarrow. In what respects are they similar ?
In what respects do they differ ?

184 LABORATORY AND FIELD EXERCISES

(2) Summarize the similarities and differences of the

inflorescence and flowers which you have observed
in comparing the dandelion with the yarrow.

(3) Pollination, Proceed as directed under the labora-

tory directions on the yarrow to find out the
mechanism of pollination in the dandelion. Com-
pare with the yarrow in this respect. Construct
figures for the dandelion similar to those of the
text on the yarrow.

c. Fruit and seed. Study the fruit and seed of the dande-
lion and compare them with the fruit and seed of
the yarrow.

(1) What special device has the fruit of the dandelion

for dispersal ? What is the origin of the parachute
of hairs ? To what part of the flower do the
hairs correspond ?

(2) Construct a series of three figures to illustrate the

development of the fruit in the dandelion, begin-
ning with closed floral heads in which the flowers
have been recently fertilized.

3. Seasonal history. Construct figures to illustrate the sea-

sonal history of the dandelion. Is it annual, biennial,
or perennial ? By what means does it spread so rapidly
in lawns and along roadsides ? Study the relations of
its leaves to the grass beneath them. State five reasons
why the dandelion is so successful in gaining and
holding a place for itself in lawns.

4. Analysis. Ascertain the species name of the dandelion

by means of a manual.

SECTION XII. FIELD WORK
(MONOCOTYLEDONS)

A. TRADESCANTIA, TULIP, AND OTHER MONOCOTYLEDONS

The most common and well-known monocotyledons include
the common grasses, sedges, and cereal grains, different mem-
bers of the lily family, palms, bananas, and bamboos. The
student should consult illustrated manuals and texts in order
to form a general idea of the habitat and habit of the mono-
cotyledons. Examine also a number of species in the field and
in the laboratory, as outlined below, in order to fix the main
distinctive characteristics of monocotyledons. Tradescantia and
the tulip may be taken as types for special examination.

1. Habitat. How many of the above-mentioned common

monocotyledons are widespread or cosmopolitan in
habitat ? How many are restricted in habitat ? Are
most of these monocotyledons mesophytic, xerophytic,
or hydrophytic in habitat and habit ? Can you name
common monocotyledons belonging to all three of
the above habitats ? Summarize the above facts in
your notes.

2. Habit. Compare monocotyledons with dicotyledons in the

following particulars of general habit and structure :
n. Lc<i/'/'x.

( I ) Form and venation. What are the distinctive features
of the leaves of monocotyledons in these respects ?
Note particularly whether monocotyledons have
open or closed marginal venation.

186 LABORATORY AND FIELD EXERCISES

(2) Study and draw leaves of one or more mono-
cotyledons to illustrate the form and mode of
venation characteristic of the group.
b. Stem.

(1) Aerial and underground stems. Do monocotyledons

generally have aerial stems as well developed as
dicotyledons ? How is this in grasses and cereals,
cultivated lilies, narcissus, tulips, onions, iris,
palm? Do they have rhizomes, bulbs, and tubers?
Study specimens and manuals to determine this
point. Are the aerial stems of monocotyledons
mostly flower-bearing stems or are they well-
developed leafy stems ? Are monocotyledons
mostly herbs, trees, or shrubs ? Compare with
dicotyledons in this respect.

(2) Study and draw the underground and aerial stem or

stems of one or more monocotyledons. Indicate
nodes, internodes, buds, and annual increments
of growth.

(3) Anatomy. Cut transverse sections of the aerial stem

of some monocotyledon and observe the sections
with low and high powers of the microscope.
Are there the usual tissue areas characteristic
of the stems of dicotyledons ; namely, epidermis,
cortex, and the vascular ring of phloem, xylem,
and pith ? Is there a cambium present ? How
do monocotyledon stems increase in thickness ?
Draw your section in outline, naming the tissue
layers and tissue groups as you think they
should be labeled. Draw a single vascular bun-
dle and label its skeletal and conducting tissues.
Summarize the distinctive features of the anatomy
of monocotyledons as for dicotyledons above. See

THE SPRING FLORA 187

the discussion of the stem structure of mono-
cotyledons in Part I of the text.
3. Reproduction.

a. The flower. Study the structure and floral plan of

flowers of one or more monocotyledons.

(1) In what respects are these flowers like the flowers

of dicotyledons already studied ? In what respects,
if any, are they different? Have the flowers of
monocotyledons and 'dicotyledons the same num-
ber of floral members in a cycle ? See your speci-
mens and illustrated manuals.

(2) Essential organs of the flower. Compare the stamens

with those of dicotyledons. Study the pistil of the
tulip or of a similar monocotyledon. Cut transverse
sections and observe the relation of megasporo-
phylls or carpels which enter into the formation
of a pistil in monocotyledons. Is the placenta
central or parietal ? Note the form and attach-
ments of the ovules. Draw the section of the
pistil and ovules greatly enlarged. Label.

(3) Ground plan. Construct a ground plan of a flower

of a monocotyledon and compare it with the
similar plan made of the flower of a dicotyledon.
In what fundamental respect are the two different ?
In what respects are they alike ?

b. Seeds and embryo. If available, study the seeds and

embryos of typical monocotyledons, including a
cereal, such as corn or wheat. In what respects
do the seeds and embryos of typical monocoty-
ledons differ from those of dicotyledons ? Con-
struct a drawing of a seed of a monocotyledon to
show the relations of the embryo, endosperm, and
seed coats.

188 LABORATORY AND FIELD EXERCISES

4. Summary and comparisons. Summarize the contrasting
characteristics of monocotyledons and dicotyledons
under the following headings :

a. Habit.

(1) Leaves : form and venation.

(2) Stem : general characters and anatomy.

(3) Roots: general characters.

b. Reproduction.

(1) Floral plan.

(2) Seed and embryo.

Consult the text discussion under the comparison of dicoty-
ledons and monocotyledons.

B. SOLOMON'S SEAL (POLYGONATUM) OR FALSE SOLOMON'S
SEAL (SMILACINA)

1. Habitat. Ascertain by field studies the natural habitat

of such forms of monocotyledons as the Solomon's
seal, in which there is a rhizome and an aerial stem.
Are they typical mesophytes or are they tropophytes
(plants which adjust themselves alternately to typical
mesophytic conditions and to dry semixerophytic condi-
tions) ? What structural provisions have the true and
false Solomon's seal for such environmental adjustment?
Is this a common adjustment in monocotyledons with
stems in the form of rhizomes or bulbs ?

2. Habit.

a. Tlie rhizome, or underground stem.

(1) Are there nodes and internodes ? leaf scars and bud-

scale scars ? scars produced by previous aerial
stems ? Are there other evidences that the rhi-
zome is a stem ?

(2) Buds and growth. What structures are produced

each season by the growth of buds on the rhizome ?

THE SPRING FLORA 189

How many years of growth are represented in
your specimen ? Is the aerial stem a product of a
terminal or of a lateral bud ? How is the growth
of the stern continued after the production of the
annual aerial stem ? Does the rhizome branch
underground ?

b. Aerial stem. Compare the general form and structure

of the aerial stem and rhizome. Are there nodes,
internodes, buds, and branches ?

c. Leaves. Study the leaves and their venation. Compare

their form and venation with that described in
the text.

(7. Drawing. Construct a drawing to illustrate the main
structural features mentioned above.

3. Anatomy. Cut transverse sections of the underground and

aerial stems and stain with, iodine.

a. Compare the two sections as regards the disposition of

the skeletal, storage, and vascular systems. What is
the main function of the rhizome ? of the aerial stem ?
Is the structure of each stem adapted for its work ?

b. Construct outline sketches of each stem to illustrate

the distribution of the three classes of tissues men-
tioned above.

4. Reproduction.

a. Inflorescence. Are the flowers solitary or do they form

• an inflorescence ? If an inflorescence is present, to
what class does it belong ?

b. Flowers.

(1) Structure and floral plan. Compare the structure
and floral plan of the flower that you are studying
with that of a typical monocotyledon, like Trades-
cantia, described in the text. Is the flower perfect,
complete, and regular?

190 LABORATORY AND FIELD EXERCISES

(2) Pollination features. Ascertain whether the flowers

are self-pollinating, close-pollinating, or cross-
pollinating. Are there special devices for securing
pollination ?

(3) Drawings. Construct a ground plan of the flower

and outline drawings of the flowers in long sec-
tion to illustrate the relation of anthers and
stigma at the time of pollination.

c. Fruit and seed. To what class does the fruit belong ?
Are there special devices for seed dissemination ?

5. Seasonal life. Is the plant you are studying an annual, a

biennial, or a perennial ? What are the seasonal func-
tions of the aerial stem and rhizome ? Construct a series
of figures to illustrate the seasonal life of Polygonatum
or Smilacina.

6. Analysis. By means of a manual ascertain the scientific

name of the species studied.

C. IRIDACEAE AND ARACEAE

1. Habitat and habit. Study one species of Iris and one of

Arum, using the same general plan as that outlined
above for Polygonatum and Smilacina. Be able to
explain the seasonal life and environmental relations
of each.

2. Reproduction. Consult the text explanations and discus-

sion of Iris and jack-iu-the-pulpit.

a. Floral plan. Determine the floral plan in each case.

b. Structure. Are the flowers hypogynous, perigynous, or

epigynous ? Are they complete, perfect, and regular ?
Distinguish between the parts of the perianth. Do
you find stamens and pistil of the regular type
characteristic of monocotyledons ?

THE SPRING FLORA 191

c. Pollination in Iris. Consult the text description and

confirm the structural arrangements there explained
concerning the pollinating mechanism in Iris.

d. Pollination in jack-in-tlic-pulpit. Be able to explain the

special devices for pollination in jack-in-the-pulpit.

3. Summary. Summarize the method and the special mechan-

isms for securing cross-pollination in Iris and jack-in-
the-pulpit.

4. Seasonal history. Be able to explain and illustrate the

seasonal history of Iris and jack-in-the-pulpit.

D. GRAMINEAE

1. Habitat and habit. Follow the plan outlined above in

the general directions for studying monocotyledons.

2. Reproduction. Study the reproductive structures of the

common cultivated oat (Avena), using the text discus-
sion and figures to assist you in understanding the
inflorescence, flower, and fruit. Make appropriate draw-
ings of inflorescence and flowers.

3. Seasonal history. Be able to illustrate the seasonal his-

tory of some common grass and explain the seasonal
functions of its main organs.

4. Economic importance. Summarize the facts relating to the

economic importance of the plants belonging to the
grasses and the grass family (G-ramineae).

SECTION XIII. PLANT ASSOCIATIONS

In a preliminary course in botany very little time is avail-
able for the study of ecology. A brief field study will, how-
ever, give the student a valuable insight into the social life
of plants and their dynamic relation to the environment. The
following studies may well be assigned early in the spring term
and followed as the season advances :

1. Nature and composition of plant associations. Make a
preliminary study of any area of soil ten or fifteen feet
square covered with vegetation, as indicated in the
following outline:

a. Kind and number of species associated together in

one area.

(1) Count the number of different kinds of plants

inhabiting the area under observation. Name
as many of the species as possible and determine
unknown species by consulting manuals.

(2) Make the same determination for a similar area

somewhat removed from the first in the same
plant association. Do you find any consider-
able variation in the two portions of the same
association ? If so, account for the variation in
number and kind of species occupying the two
areas.

b. Habitat and habit of associated plants.

(1) Determine as far as possible the environmental
factors which characterize the habitat under
observation and their effect on plant growth.
192

THE SPRING FLORA. 193

The principal factors to be considered are sun-
shine, shade, relative humidity, temperature, and
soil conditions. Determine also the nature of the
soil as far as possible, taking into account the
water content, amount of humus, acidity, mineral
salts, etc.

c. Structure and seasonal life of associated plants.

(1) Are the plants inhabiting the area under considera-

tion mesophytes, xerophytes, or hydrophytes? Are
they annuals, biennials, or perennials in habit ?
Have they any special adaptations which fit them
for life in the habitat under observation ?

(2) What are the dominant species ? Can you determine

why they are dominant? Is their dominance due
to structural adaptations of leaf, stem, or root ?
Is dominance due to vegetative or other means
of rapid propagation and dissemination ? Is it
due in any measure to a perennial or biennial
seasonal life?

d. Summary.

(1) Draw a chart to indicate the distribution and abun-

dance of the three or four dominant species of the
area examined. This may be done by using circles,
squares, and triangles of different sizes to repre-
sent different species, or by using the initial letter
of each species to represent the position of the
species in the plotted area (see Fig. 288 of text).

(2) List the species found, indicating whether they are

annuals, biennials, or perennials. Indicate also
whether they are mesophytic, xerophytic, or
hydrophytic in habit.

(3) Work out by means of outline diagrams the seasonal

history of one or two dominant species of the habitat.

194 LABORATORY AND FIELD EXERCISES

(4) Define a plant association. "What are the most
important considerations which determine the
kind of dominant species composing the associa-
tion you have just studied ?

2. Kinds of associations. Study the vegetation on the margin

of a pond, lake, or stream, including the aquatic plants,
the plants of the shore, and those of the drier regions
adjoining the shore.

a. Zonotion, Do you note any regularity in the arrange-

ment of definite types of plants in the water and
along the shore ? Are there definite associations of
plants thus arranged? Is the arrangement suffi-
ciently regular to constitute definite zones of vege-
tation ? See the text and figures illustrating the
nature of zonation.

b. Kind and number of species in each zone or association.

(1) What plants grow in the water ? Are there floating

and attached algae or seed plants ? What plants
grow along the immediate shore line ? Study the
species in each zonelike association. Do you
find any discrepancy between the habitat and
the habit of plants in any given association ?
If so, explain.

(2) Determine the nature of the habitat and the environ-

mental factors controlling the association of plants
in each zone of vegetation under consideration.
Observe the structural adaptations of the species
in the various zones.

3. Summary and conclusions.

a. Draw an outline diagram of the shore line investigated
and indicate by symbols (such as circles, squares, tri-
angles, crosses, etc.) the different zones of vegetation
and the number and kinds of plant associations found.

THE SPRING FLORA 195

b. List the dominant species of each association and indi-

cate whether they are annuals, perennials, biennials,
rnesophytes, xerophytes, or hydrophytes.

c. Discuss the relation of the habitat of each association

observed to the habit of the species comprising the
association.

d. Explain any discrepancy found between the habitat and

the habit of plants in the shore associations studied.
4. Origin of new associations.

a. Shore-line associations. Do you find indications of migra-

tion, invasion, and succession in the shore-line associa-
tions ? Are plants invading the mud or gravel of the
immediate shore zone ? If so, what kinds of plants
are they, and from what place did they come ? Are
they species with special devices for dissemination ?
Are they found in the adjacent associations or are
they migrants from distant locations ? Have they
any special adaptations for their new habitat ? Do
you see any evidence of succession, or the replace-
ment of one association by another ? Discuss in your
notes the phenomena observed.

b. Denuded areas. Select an area from which the vegetation

has been removed within a comparatively short period,
as on a denuded bank, field, garden, or roadside.

(1) What plants are invading the area ? Are they from

the adjacent vegetation ? "What are the means
by which these species originally migrated to the
new home ? Have they special adaptations for
becoming established in the new habitat? Is
there a definite relation between the habitat and
the habit of the invading species ?

(2) Discuss the above facts concerning the area being

investigated.

INDEX

(References to illustrations are indicated by asterisks accompanying page numbers

Achiliea (yarrow), 181

Adjustment to environment, 19

Algse, 75 ; general study of, 82

American elm, plan and develop-
ment, 13, 110*

Anaphase, 37

Anatomy, of Adiantum, 116 ; of
Pteris aquilina, 118

Angiosperms (dicotyledons), 143 ;
sporophyte of, 143 ; reproduction
of, 146 ; hardwood trees, 161

Anthers, 65

Apple, cultivated, 180

Araceae, 190

Aspergillus, 96

Aster, 9

Bacteria, 89, 91*

Bark, 41, 42 ; kinds of, 164*

Body plan, 3 ; of lilac, 3 ; spiral, 4*

Bryophyta, 103

Buds, section of, 5* ; structure and

growth of, 34
Buttercup, 171

Capsella, ovule and embryo, 67* ;

flower of, 149
Catnip, 9
Cell, and tissue differentiation, 23* ;

and cell division, 35
Cell division (mitosis), 35
Cell structure and growth, 31
Cells, growth of, 33*
Cellular structure, 22
Cell-wall thickening, 24*
Chlamydomonas, 76
Chloroplastids in Elodea, 30
Chromoplastids, 31
Chromosomes, 35
Cinquefoil (Potentilla), 179
Collenchyma, 24*
Columbine (Afjuiliyiti). 173

Compositae, 181
Coniferales, 135
Cross-pollination, 70
Cruciferae, 17 5
Cycadales (cycads), 130
Cyclic plan of milkweed, 6*

Dandelion, 183

Dicotyledons (angiosperms), 143 ;

stems of, 50, 51* ; trees and shrubs,

155 ; herbaceous, 167

Ecological relations of plants, 63

Elm, American, 13, 16*

Elodea canadensis, 30

Equisetales, 123 ; sporophyte of, 123

Equisetum arvense, 125 ; life history
of, 126

Experiments, on tropisms, 20 ; fer-
mentation, 88 ; on bacteria, 89

False Solomon's seal, 188

Family record, trees, 157 ; herbs, 170

Fermentation experiments, 88

Filicales, 113; sporophyte, 113; asex-
ual reproduction, 120 ; gameto-
phyte, 121 ; life history of, 122

Flower, parts of, 64 ; of angiosperms,
146, 147*

Frtii/ftrift (stra\vberry), 179

Fucus vesiculosus, 83

Fungi, 86

Gramineae, 191

Growth, of root tips, 31 ; of root-tip

cells, 33*
Gymnosperms, 130 ; softwood trees,

159

Hawthorn, bud of, 5*

H< l/init/iii.^ tmnuus, stem sections, 51*
Hepatica, 171

197

198 LABORATORY AND FIELD EXERCISES

Ilcpaticae, 103

Herbaceous dicotyledons, 107

Herbaceous plants, plan of, (i* ; body

plan of, 6 ; buds of, 7
Herbaceous steins, dicotyledons, 50 ;

monocotyledons, 52

Income and outgo, 8*
Iridaceae, 100
7m, 100

Jack-in-the-pulpit, 100

Leaf, structure of, 53, 54*, 55* ; veins

of, 55*

Leguminosae, 177
Lichens, 101
Lilac, 3

Lilac mildew, 102
Lily, flower of, 147*
Liverworts, 103, 105*, 106*
Lycopodiales, 126
Lycopodium, 126

Marchantia, 105*, 106*

Metaphase, 36

Microsphaera aini, 102

Milkweed, cyclic plan of, 6*

Mitosis, 35

Mold, Khizopuu, 94 ; PenicWium, 96 ;

Asperyillus, 96
Molds, general nature of, 92
Monocotyledons, 52 ; structure of,

52 ; field work, 185
Morning-glory, seed and seedling of,

19*

Motor organs, 19
Musci (mosses), 108
Mushrooms, 97

Nutrition and seasonal life, 61

CEdogonium, 81
Ovule of Capsdla, 67*

Papilionaceous flowers, pollination
of, 68 ; structure of, 69 ; cross-
pollination, 70

Penicillium, 96

Photosynthesis, 57
Physiology, experiments in, 57

Pine, white, 10* ; study of, 159

Pines, form of, 9

Pistil, 05

Plant associations, 192

Plastids, 30

Pollination, 68. See also Cross-
pollination

Polijgonutum (Solomon's seal), 188

Poplar, vegetative and reproductive
parts of, 157

Potentilla (cinquefoil), 179

Prophase, 35

Protococcus, 75

Pteridophyta, 113

Pteris aquilina, anatomy of, 118

Puffballs, 99

Pulvini, 19

Ragweed, 9

Ranunculaceae (buttercup family),

171 ; floral modifications of, 173
Reproduction, 64
Respiration, 60
Rhizopus, 94
Ricciocarpus, 107
Roots, structure of, 53
Root-tip cells, 26
179

Seasonal life and nutrition, 61
Seed and seedlings, morning-glory,

19*

Selcginella, 127 ; sporophyte of, 127
Selaginella martensii, 128*
Shepherd's purse, 149
Smilacina (false Solomon's seal),

188

Smuts, 100

Solomon's seal (Poli/gonalitm), 188
Species record, trees, 156 ; herbs,

168

Spindle, 36
Spirogyra, 11
Spruce, anatomy of, 136; asexual

reproduction of, 139 ; gameto-

phyte of, 141
Spruce and pine, 135; sporophyte,

135

Spruces, form of, 9
Stamen hairs of Tradescantia, 27
Strawberry, 179

INDEX 199

Telophase, 37 Water ascent, 62, 71

Thallophytes, 75 Wheat, kernel and section of, 66*

Tradescaidia, stamen hairs of, 27 Woody stems, anatomy. 41 ; micro-
Transpiration, 01 scopic structure, 45

Tree, structure and growth of, 44* Wound, healing of, 46*
Trees, spruces and pines, 9; and

shrubs, 155 Yarrow (Achillea), 181

Yeast, 86, 87*
Vegetable fibers, 25*

Violaceae, 173 Zamia, gametophyte of, 133

SOUTHERN BRANCH,

UNIVERSITY OF CALIFORNIA,

LIBRARY,

ANGELES. CALIF.