A LABORATORY GUIDE

GENERAL BOTANY
GAGER

Copyright N°

COPYRIGHT DEPOSH:

aa

CON Pe : ain

a!
rye ae

eo Ae
Af

r x a i i

me %

A LABORATORY GUIDE
FOR

GENERAL BOTANY

GAGER

BY THE SAME AUTHOR

FUNDAMENTALS

OF
BOTANY

I2mo, xix + 640 Pages, 435 Illustrations. Flexible
Cloth, Round Corners, $1.50 Postpaid.

P. BLAKISTON’S SON & CO., PHILADELPHIA

A LABORATORY GUIDE

FOR

GENERAL BOTANY

BY
Bs STUART GAGER

DIRECTOR OF THE BROOKLYN BOTANIC GARDEN

PHILADELPHIA
Pe DUARISTON’ SS: SON & CO.
1012 WALNUT STREET
1916

COPYRIGHT, 1916, BY P. BLaxisTon’s Son & Co.

po =
NOV 20 1916

THE MAPLE PRESS YORK PA

©c.a446500
ene e

nig INR,

PREFACE

This LABORATORY GUIDE is intended for the use of
students in their first course in universities and colleges,
or other institutions doing work of similar grade. It is
not a teacher’s manual, and therefore does not include
information as to laboratory equipment, the purchase and
care of apparatus and materials, nor references to the
literature. The author believes that botanical instruc-
tion in America has now reached a stage where such
directions to university instructors is no longer necessary
nor appropriate.

As to the most desirable kind of laboratory directions
there is a wide diversity of opinion among teachers of ex-
perience. This GuImpE has been prepared in harmony
with the theory that the beginning student needs to learn,
in his first laboratory course, not merely botanical facts,
but how to observe and how to record his observations.
It is believed that rather full directions, such as are given
in the following pages, will accomplish this result. In
advanced courses the student should, of course, be ex-
pected to work with increasing independence, both in
his thinking and his handling of apparatus and material.
The GuIDE, substantially as here offered, has been used
with a number of large beginning classes.

The order of topics follows that in the author’s Funda-
mentals of Botany, but with only minor changes the
GUIDE may be adapted for use with any text.

The author is indebted to Dr. E. W. Olive for his care-
ful reading of portions of the page proof.

C. STUART GAGER.
BROOKLYN BOTANIC GARDEN,

October 14, 1916

CONTENTS

To the Student. .

PART.

ANATOMY AND PHYSIOLOGY

Meaning of the Terms.

A Generalized Plant (Spereoiea)

A Specialized Plant (e.g., The Bean apeciiiey
Structure of the Foliage Leaf . barre ic} TOM
Transpiration. ae

Absorption of Water ie Plants.

The Path of Water in the Plant.
Mechanical Uses of Water in the Plant .
Nutrition .

The Occurrence af @arnamy draws in peas
Formation of Carbohydrates .

Alcoholic Fermentation .

Respiration.

The Influence of Exteenal @ondiiona: on the Plant ;

PARD AI

MORPHOLOGY AND LIFE HISTORY

Meaning of the Terms.
An Outline of the Classification of Plants
Directions for Study.

Polypodium vulgare Re secicicis Toe ee

Polytrichum commune (Common hair-cap moss) .

Marchantia polymorpha (A liverwort).
Fucus vesiculosus (Bladder wrack)
Vaucheria sessilis (Green felt)
Spirogyra (Pond scum, Green silk). .
Pleurococcus vulgaris (Green slime). .
Phycomyces nitens (or Rhizopus nigricans). .
Saprolegnia (Water mold)... .
Albugo candida (Blister blight) .
Agaricus campestris (Meadow mushroom). .

} vil

PAGE

Vill CONTENTS

PAGE
Puccinia graminis (Wheat rust). i905 20 9) 4 eo
Tsoetes (Quillwort)~ 2.060 Se ee ee
Equisetum (Horsetatl): (500 62 9. ee ee
‘Lycopodium (Club-moss) .°, 2 7 ee
Selaginella (Little club-moss). 2 225 one
Zamia floridana (A cycad) § 2°.) 2 2 3)
Pinus laricio. (Austrian: pie) =o) 2) 22 ae

Trilium (Wake-robin) 2.) fee 03 ee

A LABORATORY GUIDE FOR
GENERAL BOTANY

LO; IRE STUDENT

THE NATURE AND PURPOSE OF LABORATORY WORK

A. The Laboratory:

1. The word laboratory is derived from the Latin word
labor, meaning work. A laboratory, therefore, is a
workshop. ‘The essential part of laboratory work,
however, is not the manual but the intellectual.
Handling specimens, manipulating apparatus, tak-
ing notes, and making drawings, all are essential,
but are wholly secondary to thinking. A laboratory
exercise should be regarded always and primarily as
a thought exercise. Everything else that you do
with a specimen should be secondary to thinking
about it, and done only to aid thought.

2. The aim of laboratory work is to obtain facts at first
hand. Reading books on plants is only studying
about botany. To study botany one must have the
actual plants before him. It was Louis Agassiz
who said, “If you study nature in books when you
go out of doors you cannot find her.”’ The posses-
sion of this first-hand knowledge makes the reading
of botanical books not only more easy, but vastly
more interesting. You can take more away from

the text because you bring more to it.
I

2 A LABORATORY GUIDE FOR GENERAL BOTANY

3. Another aim of laboratory work, not less important
than the one just mentioned, is to acquire scientific
habits of thought and work; to learn the method by
which knowledge of the given science is acquired.
The scientific method differs from the unscientific
in laying emphasis upon the absolute necessity of
an orderly procedure in thinking and doing, upon
willingness to put aside prejudice and preconceived
notions, upon scrupulous neatness, accuracy of
thought and work, and careful attention to minute
details. The scientific method is not peculiar to
the natural sciences: it is just as essential in history
or language-study as elsewhere, and the highest
success in any intellectual pursuit is not possible
if the requirements of the scientific method are dis-
regarded.

B. Observation:

4. Observation is not merely looking at a thing. It
means looking for a purpose. The mental attitude
of the true observer is that of a questioner. The
great Swiss botanist, de Candolle, said, “The in-
terrogation point is the key to all the sciences.”
Observation, then, consists in asking as definite
questions as possible about natural objects, and
seeking their answer, not from the instructor or
the text-book, but from the object itself.

5. Remember that your specimen is the final authority
in all matters of fact. Your first question should
never be, “What ought I to see?” “How many
parts oughi the specimen to have?” but always,
without exception, ““What doI see?” “How many
parts does the specimen have?” Possibly your
specimen may be found to differ from that of your
neighbor, or from the descriptions in the books.

> TO THE STUDENT 3

If so, record that fact, and endeavor to ascertain

whether your specimen is abnormal, or whether

your observation of it is at fault in any way.

Always try to see all you can with the unaided eye

before resorting to the aid of a hand lens or microscope.
C. Experimentation:

6. In mere observation one takes conditions as he finds
them; in experimentation, he determines, within
limits, the conditions under which the observation
ismade. It is never possible to control, absolutely,
all the conditions in any experiment, but this is

- partly compensated for by arranging side by side of
the experiment proper, a check or control. In the
experiment and control all conditions should be as
nearly alike as possible save one. The golden rule
in experimenting is: vary only one condition at a
time. ‘Then if the experiment and control give
unlike results, we are justified in attributing the
difference to the unlike factor.

7. Before beginning an experiment, the object, or aim,
of the experiment must be clearly conceived and
clearly stated. The necessary materials and ap-
paratus should next be decided upon and procured.
Then may follow the operation, that is, the arrange-
ment of the materials and apparatus in a suitable
way. This step is frequently referred to as “‘set-
ting up” the experiment. The record of it should
include an accurate statement of the conditions at
the beginning of the experiment, together with
drawings of the apparatus and material as the
experiment is set up.

Next follows the observation, which must always be
made and recorded at the time and place of the expert-
ment. It should include suitable drawings. Fin-

4 - A LABORATORY GUIDE FOR GENERAL BOTANY

ally, there may be stated the inference, that is, the
conclusion or conclusions which are thought to be
justified by the facts observed.

The record of an experiment, then, should follow
the outline given below:

1. Object.

. Materials and apparatus (with drawings).
. Operation.

. Observation (with drawings).

. Inference.

. Remarks.

D. The Note-book:

8. The Note-book serves two purposes: First, the
making of it gives you opportunity to acquire
facility in describing what you observe. This is
not an easy accomplishment, but a very essential
one. “The greatest thing a human being ever does —
in this world,” said John Ruskin, “‘is to see something,
and tell what he saw in a plain way.”

9. Secondly, the note-book serves as an index, to the
instructor, of what you have done and how well
you have done it. In addition to these two pur-
poses, the note-book will be a permanent record
for your own future use. It should contain a
complete record of all you observe, and the infer-
ences you make from these observations. It should
include written descriptions and drawings. In
both the latter the aim should be accuracy, neatness,
completeness, conciseness. Above all things, it
should be a record of your own observation, not
of your neighbor’s. If, as may happen on rare
occasions, it becomes necessary to use your neigh-
bor’s notes, always state the fact clearly and frankly
in your own book.

Am B&B W ND

Io.

TO THE STUDENT 5

In writing your notes, the aim should be to give
such a clear account of what you have seen and done
that anyone else who knew nothing of the subject
could profit by reading them. In other words,
aim to make your notes usable in the future. Your
text-book may be regarded in one sense, as the
author’s laboratory note-book. Seek to make
your laboratory note-book an accurate and readable
illustrated text on the ground covered by your
course.

E. Laboratory Drawings:

DO ae

E22.

i

14.

15:

Drawing is one of the greatest aids to observation.
This is its main purpose in the laboratory. It
is often said that ‘‘persons who cannot draw cannot
see.’ This is probably an extreme statement,
but it is undoubtedly true that one who can make
an accurate drawing of a thing has observed it
more accurately than one who cannot.

Laboratory drawings should aim to represent the
thing only as it is, not as it may impress one at
first sight. They differ in this respect from the
work of the artist. For example, to show the
exact number and location of the veins of a leaf
would ruin the artist’s picture; but without those
details the laboratory drawing would be of little
value.

As directed in the GurpE, make as thorough an
observation of the object as possible before you
begin to draw; then make the drawing.

Unless otherwise directed, make outline drawings,
shading only where absolutely necessary. In
general, every line in your drawing should represent
some fact of structure in the specimen.

Be sure to make the drawing large enough so that

16.

£7:

18.

LQ.

20.

A LABORATORY GUIDE FOR GENERAL BOTANY

all details may be included without crowding or
confusion.

First sketch in the outline lightly with a 5H drawing
pencil. In finishing a 2H pencil may sometimes be
desirable.

All drawings should be on unruled sheets, and only
on one side of the sheet. They should be labeled
and numbered consecutively throughout the course
by writing under each the abbreviation Fig.,
followed by the proper numerals, and then by the
legend or label, stating what the object is, and what
view of it is shown, as for example, ‘‘Cross-section,
end view.” Each drawing should have all of its
essential parts labeled by extending straight
horizontal dotted lines from the various parts
(using a ruler), and writing the name of the part
at the end of the line. |

The arrangement of the drawings on the page |
should receive careful attention, so as to make as
attractive and well balanced a page as possible.
Crowding should be avoided, and on any one page
should be included, only those drawings that repre-
sent parts of the same plant, or pertain to the
same subject.

The various pages of drawings should be numbered
and labeled near the top of the page at the middle
thus; Plate J. Throughout your written notes,
when describing a structure or apparatus repre-
sented by a drawing, refer to the drawing by its
proper number and the number of the Plate (e.g.,
Plate IV, Fig. 5).

At the completion of the course, arrange a ‘“‘Table
of Contents,” listing the main topics, as indicated
in the LABORATORY OUTLINE, in the order in which

TO THE STUDENT 7

they occur in the note-book, with the page number
near the right-hand edge, and a neat dotted line
extending from the subject to the page number.

F, The Microscope:
21. Full directions for the use and care of the compound

vt

microscope will be given by the instructor. The
student should clearly realize from the first that the
science does not reside in the instrument. The latter
is merely an aid to the eyes, but not to the mind,
and is made necessary by the limited range of our
unaided vision. It should be used only after one has
seen all that he possibly can with the unaided eye.
The following points should be constantly borne
in mind:

(a) Keep all parts of the instrument, especially

the lenses, scrupulously clean.

(b) Never attempt to take the instrument apart.
(c) Never remove lenses from the stand. If it
is ever absolutely necessary to do so, then

(d) Never lay a lens down on the table.

(e) Never touch the lens with the fingers or eyelids.

(f) Never try to clean the lens with the handkerchief
or anything except lens paper.

-(g) Never examine any object without covering

it with a cover-glass.

(kh) Never allow the objective to touch the cover-
glass.

(t) Never focus down while looking through the
microscope.

(k) Be sure that the slides and covers are absolutely
clean. Dirt will be magnified as well as the
object you are studying.

(1) Handle all slides and cover-glasses by the edge,
never touching their surface with the fingers.

A LABORATORY GUIDE FOR GENERAL BOTANY

(m) Don’t shut one eye* when looking through
the instrument. Ability to work with both
eyes open is easily acquired, is much less
tiring, and is an advantage in many ways.

(nx) Never use kigh powers when low powers will serve.

(0) Examine all objects with the low power first, —
then with the high power, if necessary.

(p) Never set the instrument away with a micro-
scopic slide under the objective, nor with the
high-power objective over the aperture.

(g) When the laboratory period is over, remove
the preparation you have been studying, and
leave the microscope with the low-power
objective over the aperture.

PART |
ANATOMY AND PHYSIOLOGY

I. MEANING OF THE TERMS

A. Plant physiology is that branch of botany which deals
with the vital activities of plants. But physiological
processes or functions are carried on by various parts
of the plant, and these parts all have their own char-
acteristic structure. In order to understand the proc-
esses we must know the internal as well as the
external structure of the parts concerned. This knowl-
edge requires dissection, and this phase of the science
is, therefore, called anatomy. Microscopic anatomy is
called histology. Just as the processes cannot be
intelligently considered apart from the structures
involved, so, also, the study of anatomy apart from
physiology is meaningless.

B. In the lowest (z.e., most simply organized) plants all
functions, both nutritive and reproductive, are per-
formed by every structural unit or cell; but in more
highly organized plants there are special parts or
organs for the performance of each function; for ex-
ample, roots to take in moisture, flowers to form seed.
In other words, in the higher plants there is a division
of physiological labor, or, as it is sometimes called, a
physiological division of labor. While not entirely
wanting, the division of physiological labor is less
marked in the lowest plants.

9

Io

ANATOMY AND PHYSIOLOGY

Because they are composed of organs, plants and
animals are termed organisms.
Thus we see that some plants have a generalized plant-
body, others a more highly specialized one. To under-
stand the various life-processes carried on by plants,
we must have a knowledge of their structure. A gen-
eralized plant will be studied first, then the structure
of a higher (z.e., more highly specialized) plant. This
will be followed by an elementary study of the funda-
mental life-processes involved in the nutrition and
growth of the individual. The second part of the
course will be devoted to studying the various kinds
of plants, and thetnumerous ways in which different
kinds of plants solve these same life-problems of nutri-
tion and reproduction.

II. A GENERALIZED PLANT (Spirogyra)

A. Naked-eye Characters:

1. Carefully take a small bit of this plant between the
thumb and fingers and note its “feel.” Suggest
why it is sometimes referred to as “green silk.”

2. Carefully lift up some of the material with a needle,
and describe the form of the plant. How many
centimeters long are the longest filaments you can
observe?

3. Can you detect any evidences of a differentiation
of the plant into shoot (i.e., stem and leaves) and
root ?

B. Microscopic Characters:

1. The plant as a whole.

(a) Mount two or three filaments in water.

(b) Note that the filament is composed of separate
structural units, placed end to end. These
units are cells.

(c) Are the filaments more than one cell thick?
Do they branch? Are they of uniform diame-
ter? Compare the length of the various cells
with each other. Compare the shape of the
end cell with that of the others. What is the
shape of the filament as seen in imaginary cross-
section? Very careful focussing is necessary in
order to answer this question correctly.

(d) Accurately measure the length (in millimeters)
of a piece of filament lying straight under the

cover-glass, then count the number of cells in
pout

2

(e)

)

ANATOMY AND PHYSIOLOGY

this piece. Calculate the average length of the
cells, and the number of cells in the longest
filament observed. Estimate the length of an
individual cell in terms of its diameter, and from
this calculate the diameter of the filament.
Using the low power and removing the cover-
glass, carefully cut a filament apart with the
scalpel, causing as little injury as possible. As
you do this observe the exposed end-walls of
the uninjured cells that now terminate the fila-
ment where it was broken apart. Describe and
try to account for what you see. Is there any
evidence of the existence of a force within the
cell? If so, in what direction does it act?
Make two outline drawings, showing the con-
ditions before and after cutting.

Make a diagram about 75 mm. long, illustrating
the outline of the three terminal cells of a fila-
ment, as seen in optical section. Omit all de-
tails of cell-structure.

2. The individual cell.

(a) Center your attention on any one of these cells,

and identify the following organs of the cell:
(z) A cell-wall, enclosing all other parts of the
cell. Is it transparent or not? Give a
reason for your answer. Note its relative
thickness. The wall is composed of cellu-
lose. Has each cell its own end-wall, or is
there a common end-wall for two adjacent
cells?

The substance enclosed by the cell-wall is
largely living matter, or matter in the living
state. It is called protoplasm. The unit
of protoplasm of each individual cell is

(2

od

(3)

(4)

(5)

(6)

(7)
(8)

A GENERALIZED PLANT 13

called a protoplast. Distinguish the follow-
ing parts of a protoplast:

The prominent green chlorophyll-band, or
chromatophore. Describe its form, the
number of turns it makes in the cell, and
the outline of its margin. Infer its shape
in cross-section. How many in each cell?
If more than one, do they coil in the same
direction? Can you detect free ends of the
chromatophore? Are they continuous from
cell to cell? The color of the chlorophyll-
band is due to the presence of a green pig-
ment, chlorophyll.

The denser areas within the chromatophore
are regions of starch-formation. In the
center of this area is the starch-forming
body, or pyrenoid. Surrounding the pyre-
noid are starch grains.

Make a detailed drawing, 10 mm. wide and
15 mm. long, showing the details of struc-
ture of a portion of the chlorophyll-band,
as seen under high power. Indicate on the
drawing the names of all parts shown.

At or near the center of the cell find a dense,
colorless body, the nucleus, surrounded by
a less dense layer of colorless cytoplasm.
Describe the shape of the nucleus. From
the layer of cytoplasm trace

Delicate cytoplasmic strands, extending to
the pyrenoids, and to |
The lining layer of cytoplasm. This layer
(sometimes called “ primordial utricle’’) is
in intimate contact with the entire inner
surface of the cell-wall, and is difficult to

14

(9)
(10)
(11)

(12)
(13)

(14)

ANATOMY AND PHYSIOLOGY

identify. Its two surfaces are plasma
membranes.

The clear spaces in the cell are vacuoles,
filled with cell-sap.

Make a drawing of a cell at least 10 cm. in
longest measure. .

The lining layer may be easily demonstrated
as follows: Place a drop of a 5 per cent.
solution of common salt (sodium chloride)
at one edge of the cover-glass. Be careful
that none of the solution runs over onto the
cover-glass. By placing a small piece of
blotting paper at the opposite edge of the
cover-glass, the water will be removed, and
the salt solution drawn under the cover-
glass, irrigating the specimen. Follow with
another drop if necessary. Observation
should be continuous while the specimen
is being irrigated with the solution.
Describe the effect of the salt solution on
the lining layer.

Loosening the lining layer, as above, is
termed plasmolysis (i.e., loosening the plasm).
The cell is said to be plasmolyzed.

Make a drawing, the same size as the pre-
ceding, showing a plasmolyzed cell.

(15) Before plasmolysis the lining layer was held

(16)

close against the cell-wall with a force,
already detected (e, p. 12), sufficient to
cause a rigid condition of the cell called
turgor or turgidity. |

Now replace the salt solution with fresh
tap-water, by the method described in (11)
above. Describe the effect on the cell.
What condition has been restored?

A GENERALIZED PLANT 15

3. Make a diagram, at least 25 mm. in diameter, show-
ing the appearance of a cell in imaginary cross-
section taken through the nucleus.

4. Do you think Spirogyra is a unicellular or a multi-
cellular plant? If the latter, how many cells con-
stitute one plant? Give reasons for your opinion
either way.

Note.—If time permits, the study of cell-structure may be ex-
tended by observing the cells in young leaves of Elodea, the skin
(epidermis) of onion scales, the basal cell of the hairs on any seed-
ling cucurbit, or the cells of the stamen hairs of Tradescantia.

III. A SPECIALIZED PLantT (e.g., The Bean Seedling)!

A. The plant as a hole:

I.

Examine the seedling given you and note that it is
composed of an axis with appendages; the axis, of
root and shoot; the root, of a primary root with
branches (Secondary roots); and the shoot, of a
main stem, bearing leaves. Has the main stem
branches? Is this true of all plants? What is the
difference between a stem and a branch?

. Describe fully the location of the leaves and their

attitude on the stem. Do they occur on both the
main stem and its branches? The places on the
stem where leaves grow are nodes. The spaces
between the nodes (vertically) are called internodes.

. Compare the size of the upper with that of the lower

angle made by the leaves with the stem. This
upper angle is called the leaf-axil (Latin axilla,
armpit).

. Do you find any structures in the leaf-axils? Ifso,

describe them. What are they?

. With what do the tips of the main stem and branches

terminate?

6. Describe any other outgrowths of stem or branches.

. Make a drawing of the plant as large as your draw-

ing paper will permit, showing all parts referred to
above.

1 This study may or may not be omitted, depending upon the previous
preparation of the students, and the time available.

16

IV. STRUCTURE OF THE FOLIAGE-LEAF (e.g., Lilac

Leaf)

A. External Characters:

1. Make a drawing, natural size, showing all the parts
of the foliage-leaf given you, as seen from the under
side.

2. Identify the following parts, and label them suit-

ably on your drawing:

(a)

(b

qe

(c)
(d)
(¢)

The flat, expanded blade. Describe its colora-
tion (z.e., the kind and distribution of color).
Is the blade simple (7.e., not divided into leaf-
lets), or compound (7.e., branched, divided into
leaflets)? The surface that lies uppermost, as
the leaf bends back from its position in the bud,
is the ventral surface; the under surface is the
dorsal one. ‘These terms are applied with ref-
erence to the position of the leaf in the bud.
The leaf-apex, which is also the apex of the
blade.

The margin of the blade.

The base of the blade.

The venation (distribution of veins in the blade).
Describe it as parallel-veined, pinnately netted-
veined (with a midrib), or palmately netted-
veined. Describe the difference between the
three types of venation. Is there a marginal
vein? If so, suggest what advantage it may
be to the leaf.

({) The petiole (stem of the leaf). Leaves having

a petiole are petiolate, otherwise sessile.
17

18 ANATOMY AND PHYSIOLOGY

(g) The leaf-base, the portion by which the leaf is
attached to the branch.
(k) Ti present, the stipules, outgrowths of the leaf-
base. Leaves without stipules are exstipulate.
(z) Before the next class exercise compare with the
leaf studied, as directed above, various other
types of leaves collected by yourself, making
full drawings and notes.

B. Anatomy of the Leaf:
THE LOWER EPIDERMIS!

1. As directed by the imstructor, remove a stmp of
the lower epidermis of a foliage-leaf, and mount
it in water or clearing fluid, being sure to have the
outer suriace uppermost. Record the name of
the species.

2. Note the cellular structure of the epidermis. A
group of cells, similar in structure and function,
as called a tissue. ‘The leaf-epidermis is epidermal
tissue. The cell-wall forms a box, having depth as
well as length and breadth. Note that you see
only the edges of the vertical walls. How many
are there? Are there other walls? Ti so, how
many? Are they visible? Explain Make a dia-
gram oi an epidermal cell as seen m perspective.
Are the cell-walls transparent or opaque? Give
a reason for your answer. Suggest the advantage
oi this feature to the plant.

3- Observe the somewhat lenticular openings, or
pores, each surrounded by crescent-shaped cells.

i Muss Ecxerson (Bai. Gaz., 46: 221-224. Sig08) has recommended
the leaves of the following plants 2s specially satisfactory for the study
of the epidermis and stomata: Sunflower, Fucksia speciosa, zonal Gera-
minum, and Tradescaniia zebrima.

> STRUCTURE OF THE FOLIAGE-LEAF 19

The openings are stomata (Latin singular, stoma, a
mouth). The crescent-shaped cells are guard-cells.
How many has each stoma?

4. Do the guard-cells and other epidermal cells contain
chlorophyll-bodies (chloroplasts)? Describe their
shape. ‘They are not considered identical with the
chlorophyll-band of Spirogyra, hence the different
name.

5. Note the shape and arrangement of the other
epidermal cells. Are they in the same plane as
the guard-cells? Describe, giving reasons for
your answer.

6. State the number of stomata visible in the entire
field (high power). Record three counts, each
of a different area, and the average. Why is this
desirable? After ascertaining the area of the ob-
jective of your microscope, calculate, from several
counts, the average number of stomata per square
centimeter.

7. Make a drawing showing at least three stomata
with their guard-cells and adjacent epidermal cells.
The guard-cells should be at least 15 mm. long.

THE UPPER EPIDERMIS

8. As directed in B, 1-6 above, study the structure
of the upper epidermis of the same leaf. Draw.

g. Compare the structure of the upper with that of
the lower epidermis, noting, among other features,
the relative number of stomata in each.

10. In the light of the experiments on transpiration,’
what do you think is one function of these stomata?
Of the guard-cells?

1 This takes for granted that class demonstrations of transpiration have
been given.

20

Tt.

E2.

TQ.

20.

ANATOMY AND PHYSIOLOGY

Give one explanation of the difference in the rate
of transpiration from the two surfaces of the leaf.
Is this the only explanation?

CROSS-SECTIONAL VIEW

Mount free-hand sections of a fresh leaf showing
the internal anatomy as seen im cross-section.

. Identify m your section the two epidermal layers.

How many cells thick are they? Do you find
any chloroplasts in these layers?

Are all the epidermal cell-walls of the same thick-
ness? Describe any variations observed.

. Is there a thick, continuous pellicle over the surface

of the leaf? Is it composed of cells? Such a
pellicle, when it occurs, is called cuticle.

. Compare the thickness of the cell-walls in the upper

and the lower epidermis.

. Note the stomata and guard-cells, and their relation

to the other epidermal cells.

. The tissue between the two epidermal layers is

composed chiefly of leaf-parenchyma, or mesophyil,
in which are imbedded the veims. Mesophyll, and
all other tissue containing chlorophyll, whether
found in leaves or in other organs, is also called
chlorenchyma. Note that the mesophyll is com-
posed of two distinct groups of cells, as follows:
The more compactly lying cells beneath the upper
epidermis compose the palisade layer, or palisade
parenchyma. Describe their shape, contents, rela-
tive size, and relation to each other and to the
epidermis.

Between this layer and the lower epidermis lies the
spongy parenchyma. Describe its appearance, and

21.

22.

23.

24.

STRUCTURE OF THE FOLIAGE-LEAF 21

the cells that compose it. Compare it with the
palisade layer.

What fills the space between the mesophyll-cells?
Do these spaces connect with the outside air?
If so, how?

THE VEINS

At certain regions the section passes through veins,
presenting either cross, longitudinal, or other
sections of them. Note the greater differentiation
of the cells in the veins. This differentiation marks
the distinction between fundamental tissue or
parenchyma, and transformed tissue, prosenchyma.
There are several different kinds of prosenchyma.
Using prepared slides, supplied by the instructor,
make a drawing of the cross-section of a leaf, show-
ing all features noted above. Make the drawing
at least 75 mm. long, and be careful to preserve the
natural proportions.

The experiments on transpiration have shown that
living plants are constantly losing water. What
would be the result if no more were supplied?
What problem of plant life, therefore, naturally
arises?

V. TRANSPIRATION!

A. Loss of Weight of a Growing plant:

Experiment 1.—Object:* To show that a living plant
is constantly losing weight.

1. Choose a well-watered, vigorous, potted plant.
Wrap the pot in sheet rubber or oilcloth (or paraf-
fined paper), and tie the wrapping about the stem
tightly, but not tightly enough to cause injury.
Place the plant thus prepared on a pair of balances
in a well-lighted window, and record its exact
weight in grams in the following table, which should

Weight in
grams

be copied into your note-book. After weighing,
the window should be opened (if the weather is not
too cold); direct sunlight is also desirable. Record

1 NoTtE.— Where the class is large, or the laboratory equipment limited,
and especially when the course extends over only one semester, it is rec-
ommended that most, if not all, of the physiological experiments outlined
in the remainder of Part I be performed by the instructor as demonstra-
tions in the presence of the class.

2 For directions for recording an experiment see p. 4 of this GUIDE.
In each experiment this outline is to be filled out entire, without further
directions.

22

TRANSPIRATION 23

the weight at five or six successive periods, and then,
as directed by the instructor, plot on section-paper
a curve of your readings. Lay off the observed
weights as ordinates, the time-intervals as abscis-
se. Be sure that in this and all subsequent ex-
periments your inferences are only those warranted
by your observations.

Experiment 2.—To ascertain one cause of loss of weight

a

of plants.

Take four clean, dry glass beakers or tumblers, two
pieces of cardboard large enough amply to cover the
opening of the beaker, and a vigorous green leaf
having a leaf-stalk and a perfectly dry surface.

. Fill two of the glass beakers or tumblers three-

fourths full of water, insert the leaf-stalk through
a small hole in the center of one piece of cardboard,
make the opening as tight as possible about the
leaf-stem, using cotton if necessary, and place the
cardboard over one of the water-containing beak-
ers, so that the leaf-stalk extends down into the
water. Invert one of the dry beakers over the leaf.
Arrange the other two beakers and cardboard in
the same way, only omitting the leaf and the hole
through the cardboard. This second set of beak-
ers is the control (cf. p. 3, 46).

. Place both sets of beakers in a well-lighted window,

preferably in direct sunlight, and from time to time
observe and compare the appearance of the inner —
surfaces of the inverted beakers.

. Do you notice any difference in the result on oppo-

site sides of the leaf? If so, describe.

. Can you see any water passing from the leaves?

In what state, therefore, does it pass off? From
what part of the leaf does it come? Why do you

ANATOMY AND PHYSIOLOGY

think so? What change does it undergo in order
to become visible on the surface of the beaker?
In what state does it probably exist in the leaf?
State one reason why the plant lost weight in
Experiment 1. Was this the only cause of its loss
of weight?

6. The above experiments demonstrate the fact of
transpiration. Give a definition of transpiration.

. The Control of Transpiration:

Experiment 3.—To see if the epidermis affects the rate
of transpiration.

1. Take two sound apples. Remove the skin (epider-
mis) from one of them, then ascertain accurately
and record the weight of each, in tabular form, as
follows:

Time Weight in grams

Day | Hour | Unpared | Pared
ee pace «
ie

2. Place the specimens in a convenient place, with free
access of air, and out of reach of mice.

3. Record, in a table like the above, three (or more)
subsequent observations of weight at successive
class periods.

4. Plot two curves showing the rate of loss of weight.
Include these curves and their interpretation as
part of your record of the experiment.

Experiment 4.—To demonstrate the effect of the
“‘skin”’ of a potato-tuber on transpiration.

TRANSPIRATION 25

1. Proceed as directed for Experiment 3, using two
sound potatoes instead of apples.

2. The “‘skin” of an apple is a true epidermis, having
an outer layer of cuticle, which is not readily per-
meable by water. The ‘‘skin” of a potato-tuber
is more complex, consisting of several layers, one
of which is a layer of cork-tissue. It is this corky
layer which chiefly retards the loss or water from
the tubers.

Experiment 5.—After noting the color change caused

by wetting dry cobalt paper (prepared’ by dipping
filter paper into a solution of cobalt chloride and
thoroughly drying it), maké the following experi-
ment: Place discs of the cobalt paper (e.g., as
large as a five cent piece) on opposite sides of a
lilac leaf, and hold all in place between two micro-
scopic slides (or larger pieces of glass), fastened
with rubber bands around each end. Compare the
rate of color change of the two opposite discs, and
infer the cause.
Other leaves, having structural peculiarities
similar to those of the lilac, may be used; e.g.,
hibiscus, osage orange, oleander, lizard’s tail
(Saururus).

Experiment 6.—Examine, with the microscope, strips
of both upper and lower epidermis of the leaf used
in Experiment 5, and infer the probable cause of
the differential color-change observed.

Experiment 7.—Place any suitable, well-watered potted
plant on postal scales, “‘household”’ scales, or other
convenient weighing device, after first carefully
wrapping the pot in sheet-rubber, or sheet-oil-
cloth, asin Experiment1. Record the loss of weight
at fifteen-minute (or other suitable) intervals while

26

ANATOMY AND PHYSIOLOGY

the experiment is standing for an hour, each, in (a)
direct sunlight and breeze; (6) diffuse sunlight, and
the comparatively still air of a room; (c) under a
glass bell-jar, or large box. The breeze may be
secured by placing the experiment in or near an
open window or other draught, or by means of an
electric fan.

On the basis of your observations in Experiment 7,
discuss the control of transpiration by external
conditions, and suggest differences in the condition
of the plant caused by its exposure in the various
situations suggested above, and the effect this would
have on the ratéof transpiration. Were the results
observed in the three situations strictly comparable?
Why?

C. One Effect of Transpiration:

Experiment 8.—To show the so-called “‘lifting power’’

of transpiration.

. Insert a leafy stem of a living plant (a branch of any

evergreen is excellent to use) into one end of a piece
of glass tubing about 3 ft. long, of small bore, and
full of tap-water, taking special care to have the
joint between the stem and the glass air-tight,
using rubber tubing for this purpose if neces-
sary. The experiment will be more satisfactory
if the stem is cut off under water, and the cut
end kept from contact with air, throughout the
experiment.

. After being sure that the glass tube is full of water,

place it upright in a dish of mercury, having care
not to allow any of the water to run out in so doing.

. Place the experiment in sunlight, if possible, but

do not leave it in direct sunlight for more than one-
half to three-quarters of an hour.

TRANSPIRATION 27

. At the beginning of the experiment, and at suitable

intervals thereafter, as directed by the instructor,
measure and record the height of the mercury in
the glass tube. -

. Make two drawings of this apparatus in longitudi-

nal section: (a) as soon as the experiment is set up;
(b) at the close of your final observation. Label
all essential parts.

. You have made this last experiment with a living

plant. The question now naturally arises: Is the
result observed due to the life-factor involved, or
is it merely the result of some physical condition,
as, e.g., the evaporation involved? The question
may be easily answered by setting up an experiment
similar to the preceding, but using non-living
material, as follows:

Experiment 9.—To see if evaporation exerts a ‘“‘lifting
power.”

ie 3

Tie a piece of porous animal membrane (e.g., bladder)
over a thistle-tube, being sure that there is no
chance for a leak between the glass and the
membrane.

2. Fill the thistle-tube with water.

. Prepare a dish of mercury and also a clamp to hold

the tube in place.

. Invert the thistle-tube and place the lower end in

the mercury, being sure that no air enters the tube.
By this arrangement all factors of Experiment 8
have been eliminated except evaporation, and the
evaporation takes place through only one mem-
brane, and that a non-living one. In other words,
we have Experiment 8 reduced to its lowest terms.

. Observe and record the height of the mercury in the

tube as in_Experiment 8.

28 ANATOMY AND PHYSIOLOGY

6. Make a drawing of this apparatus in longitudinal
section at the beginning and at the close of the
experiment, labeling all essential parts.

7. The conclusions drawn from this experiment should
cover an explanation of the bearing of these results
on Experiment 8.

VI. ABSORPTION OF WATER BY PLANTS

A. External Anatomy of the Root:

1. Examine roots of seedlings (mustard, flax, oats,
etc.), grown in a moist chamber (e.g, flower-pot,
or saucer of same), and kept covered with a glass
plate so as to expose them to the air as little as
possible. Note the delicate white hairs on them.
Describe their distribution and relative size. These
hairs are root-hairs.

2. Hold the root up to the light and note the more
transparent tissue on the end (root-cap), covering
the root-tip proper. How is the latter distin-
guished? Is “root-tip’ synonymous with “end of
the root?” Explain.

3. Make a drawing of the seedling, at least twice
natural size, showing these features. (The labeling
of the root-cap and root-tip may be deferred until
observation B, 3, below, has been made.)

B. Microscopic Characters of the Root:

1. With the scalpel carefully remove the terminal
5 to 6 mm. of a root, with the root-hairs, and mount
it in water. Locate the oldest and youngest root-
hairs. How are they distinguished? Do they
branch? What relation do the hairs bear to the epi-
dermis? Are they divided by cross-walls? Do they
contain nuclei? What is a root-hair, structurally?

2. Make a drawing (high power) of three or four hairs,
showing their structure and relation to the epider-
mis. The hairs should be drawn at least 50 to 75
mm. long.

29

30

ANATOMY AND PHYSIOLOGY

3. Distinguish the root-tip from the root-cap. Of

what is the latter composed? Describe it. Draw.

C. The Function of Root-hairs:

qs

Carefully pull up a mustard seedling growing in
sand and having several leaves. Without injuring
the plant, carefully and very gently shake off all
sand that readily fallsaway. Does the sand adhere
with equal firmness to all portions of the root?
Describe in detail, explain, and illustrate by a
drawing, X2.

. Pull up another seedling of the same age, and remove

all or most of the adhering sand. Replant both
seedlings in sand, water them, and set them aside
until the next period. In order to eliminate indi-
vidual differences 1t is necessary to treat several
seedlings in each of the ways above indicated.

. At the next meeting of the class observe and com-

pare the appearance of the seedlings. In thor-
oughly removing the sand from the seedlings, how
were the root-hairs affected?

. By means of what organs does a land plant obtain

most of its water? State, in a paragraph, the
reasons for your answer.

. We have ascertained the organs whose function

it is to take in water from the soil. It is now
important to inquire by what process the soil-
water passes into the plant through the organs
of absorption.

D. How the Root-hairs Take in Water; Osmosis:

1 Se

The preceding studies of the plant cell lead us to
recognize the fact that the root-hair is an individual,
elongated cell. Within is the cell-sap, a solution
of various salts; without, as the plant grows in the
soil, is the soil-water, also containing numerous sub-

«

ABSORPTION OF WATER BY PLANTS 31

stances in solution. The cell-sap of the root-hairs,
and the soil water, are solutions of different densi-
ties, and separated by layers of porous (semiper-
meable) plant substance. Name these layers.
Experiment 10.—To see what results when two liquids
of unequal density are separated by a porous mem-
brane:

. With a pen knife or a pair of scissors, remove a
portion of the shell from the large end of a hen’s
egg, taking great care not to puncture the mem-
brane that separates the white of the egg from the
shell.

. Carefully place the egg thus prepared upright in
a glass tumbler, or beaker, and pour in tap-water
until the water surface is about 1 in. above the
egg.

. By the above arrangement the solution of various
salts intermingled with the substance of the egg
serves as the more dense liquid, the water outside
as the less dense, while the membrane in the egg
acts as the porous membrane, separating the two
liquids. In other words, we have roughly imitated
the plant cell, though there is nothing in the cell
that corresponds to the shell of the egg.

. Make a careful drawing, showing the experiment
in longitudinal section, and about one-half natural
size. Label all parts.

. Make an observation at the end of an hour; of
two hours. Describe what results, and illustrate
the final result by another sectional drawing
opposite the first one.

. State as clearly as you can what has taken place
in order to produce the result observed. The
process is termed osmosis (Greek, osmos, pushing).

32

8.

Q-

ANATOMY AND PHYSIOLOGY

In this experiment, what part of the root-hair
does the egg membrane represent? the solution of
salts in the egg? the water in the beaker?

From the above study explain what takes place
when a root-hair is in moist soil. What is thus
accomplished for the plant?

to. Define osmosis.
Experiment 11.—To demonstrate osmosis in a plant

Il.

16.

oP

cell:

Mount in water several uninjured root-hairs.
Again identify (high power) the lining layer of
cytoplasm. Make a drawing of one of the root-
hairs about 50 mm. long. Leave room for two
other drawings by the side of the first one. Run
a drop of a 5 per cent. salt solution under the
cover-glass. This solution is more dense than the
cell-sap.

. Describe the effect of the salt solution « on the inne

plast.

. Make a drawing by the side of the first one, showing

what you observe. What is the process called?

. Now thoroughly irrigate the cells with fresh water,

and observe and describe the result. Explain as
fully as you can.

. By the side of your second drawing make a third,

showing the cell as it appears after irrigation with
fresh water.

In a sentence, name, in order, two processes that
take place, (@) when a living plant cell is immersed
in a solution more dense than the cell-sap; (6) when
a plasmolyzed cell is irrigated with tap-water.
What is one function of the salts dissolved in cell-
sap? What is one function of the plasma mem-
brane?

. ABSORPTION OF WATER BY PLANTS 33

Experiment 12.—Demonstration of the Osmoscope
(by the instructor).*

18. Make a drawing showing clearly all essential parts
as seen in longitudinal section, and describe the
apparatus as set up and explained by the instructor.

19. Record observations on the height of the column
of water in the tube of the osmoscope:

(a) At the beginning of the experiment.
(6b) On successive half-hours.
(c) On successive days.

20. Explain the results observed.

Experiment 13.—Demonstration of ‘‘exudation-pres-
sure”’ (by the instructor).

21. Describe and make a drawing of the experiment at
its beginning, as set up by the instructor.

22. Complete your observations and record as directed
under Experiment 12, naming the species of plant
used.

23. Compare the conditions and results in this experi-
ment with those in Experiment 12.

*It is here taken for granted that the instructor will be able to
make this demonstration (as well as that under Experiment 13) without
further suggestions, using any one of the various types of osmoscope
commonly found in botanical laboratories.

VII. Tot PATH oF WATER IN THE PLANT

Experiment 14.—To see if there are definite channels
for the passage of liquids through a stem.

1. Place the cut ends of various living, leafy shoots
(e.g., corn, plantain, lily leaves, parsnip, or seed-
lings of castor-oil plants), into a solution of fuchsin
or of eosin, and, after they have stood for a suitable
time, as determined by the instructor, observe
freshly exposed end-surfaces, and note the regions
where the colored solution appears. Does it pass
up through the whole mass of tissue, or are there def-
inite channels through which it rises? Cut sections
of the stems at various heights, and observe and
describe the distribution of the colored areas.

2. Compare the distribution of the colored areas in a
parsnip (or seedling of a castor-oil plant) and a
stalk of corn (or petiole of some lily leaf). Make
a diagram to illustrate this.

3. Examine the end of a dry corn stalk, and note the
projecting strands. What relation do they bear to
the paths of the eosin? They are composed of
fibers and vessels united, and are therefore called
fibro-vascular bundles.

4. Carefully cut the epidermis in a ring around the
petiole of a leaf of plantain, being specially careful
not to cut clear through the petiole.

5. Taking the end of the petiole in one hand and the
leaf-blade in the other, gently pull the two portions.
of the petiole a short distance apart. Describe and

34

THE PATH OF WATER IN THE PLANT 35

illustrate by a drawing what you observe. What
structures are thus disclosed?

. What relation do the fibro-vascular bundles bear
to the veins of the leaf? To the root-hairs?

. Write a clear statement of how the water passes
from the soil into the roots of a plant, and into and ~
through the leaves and out into the air, mentioning,
in order, all parts and processes studied.

VILL. Meceanicat Uses oF WATER IN THE PLANT

A. Rigidity and Matnienance of Form:
Experiment 15.—To ascertain the cause of rigidity in

ie

bo

5-

6.

beet tissue:

From a beet cut four slices about 5 mm. thick,
ro mm. wide, and 75 mm. long.

. Place the slices as follows:

(a) In tap-water.

(6) Ina ro per cent. salt solution.

(c) and (d) In boiling water for two or three min-
utes.

Then place

(c) In-tap water, and

(d) In the ro per cent. salt solution.

. At the end of fifteen minutes observe and record

the relative rigidity of the various slices, ascer-
tained by carefully bending them.

. Thoroughly rimse the slices, 6 and d, and then

transfer them to tap-water. At the end of an -
hour (or sooner) observe them again and describe
the result.

Explain your observations on the basis of your
previous experiments.

What is one mechanical use of water in a plant
tissue, and how is this accomplished?

Experiment 16—To demonstrate longitudinal tissue-

7-

tension.
Obtain a petiole of rhubarb, or burdock, or a

stalk of celery. With a scalpel make a lengthwise
36

»

=

MECHANICAL USES OF WATER IN THE PLANT 37

Io.

i

I2.

£3.

T4.

15.

cut for a distance of about 25 mm. from the end,
and just beneath the surface.

. Describe the position assumed by the severed piece.

Illustrate by a diagram, natural size.

. From another petiole cut off a portion at least

15 cm. long, with the cut surfaces normal to the
edges. Record the exact length of the piece in
millimeters.

With a scalpel carefully remove a thin strip of
outer tissue along the entire length of the piece
(or remove a strip of ‘‘bark” from a very young
woody stem). At once try to replace it. Has it
altered in length? If so, describe. Make another
similar observation at the end of ten or fifteen
minutes. What would you have to do to the
strip to make it resume its former length?
Carefully measure the length of the excised strip
about fifteen minutes after its removal. Record
,this measure, and calculate the percentage of change
‘in length.

From another portion of the petiole cut off two
strips from opposite sides (or the bark from a
portion of some young woody stem). Place one
of the excised strips in water, another in a 10
per cent. salt solution.

At the end of five or ten minutes compare the
lengths of the two strips, (a) with each other,
(0) with the portion of the stem from which they
were cut. Explain what you observe.

From the preceding studies describe the condition
of the tissues in a plant stem. To what is this
{condition due?

Of what advantage do you think this condition
would be to the plant?

38

ANATOMY AND PHYSIOLOGY

Experiment 17——To demonstrate transverse tissue-
tension.

16. Take short portions (about 15 or 20 mm. long)
of some woody stem 15 to 20 mm. in diameter,
and with the scalpel make a clean cut lengthwise
through the bark, and remove the bark, being
careful not to crack or break it.

17. At once, or at the end of four or five minutes,
try to replace the bark. Describe your success
in so doing. Draw, end view and side view.

18. What must be done to the bark in order to restore
its original length?

19. From this study what further do you know of the
condition of the tissuesin a plant stem? Explain.

IX. NUTRITION

A. The nutrition of plants is very similar to that of
animals, with the exception that all green plants
manufacture their food out of inorganic chemical com-
pounds. Animals cannot do this. They must conse-
quently receive their food ready-made. But there are
some lower organisms (doubtfully animals) that pos-
sess the ability to elaborate their food out of inorganic
compounds, while on the other hand, certain plants,
such, for example, as the mushrooms and other plants
wanting chlorophyll, lack this power.

B. The manufacture of carbohydrates is, in many respects,
the most important function of green plants. With-
out it life would be impossible, so that its study
becomes of very great interest. We will first learn
how to detect the presence of a carbohydrate such as
starch, then study its occurrence in plants, and finally
the process by which it is made out of simpler chemical
compounds.

39

X. THE OCCURRENCE OF CARBOHYDRATES IN PLANTS

A. The Test for Starch:
Experiment 18.—To ascertain the test for the presence
of starch.

7 ie

Place a bit of corn starch, about the size of a small
shot, into a test-tube one-fourth full of water.
Shake it thoroughly. Is starch soluble in cold
water? Give a reason for your answer?

. Bring the starch mixture to a boil over the flame

of an alcohol lamp, or Bunsen burner. Describe
the result. Is starch soluble in hot water? Give
a reason for your answer.

. Set this test-tube aside to cool for a moment or

two.

. Into a test-tube one-fourth full of clear water

place 3 or 4 drops of iodine solution, using a pipette.
Shake the mixture and describe the color.

. Now place 1 or 2 drops of the iodine into the

cooled, boiled starch mixture. Shake the mixture
and describe the resulting color.

. Pour one-half of this mixture into another test-tube

one-half full of water. What color appears?

. Describe a test for the presence of starch. (NOTE:

The iodine is not the #est; it is only the reagent
used.)

Experiment 19.—To see if there is starch in (a) seeds;
(b) stems; (c) roots.

40

a

OCCURRENCE OF CARBOHYDRATES IN PLANTS 4I

. Boil in water, in a test-tube, portions of the above-

mentioned parts of plants, and proceed with the
starch test, as above outlined. Record the experi-
ment as usual. Be careful to distinguish between
your observations and your inferences.

Experiment 20.—Microchemical tests for starch.
9. If time permits of individual tests by the student,

microchemical tests may be made by mounting in
water, on microscopic slides, small portions of,
first, commercial starch; second, material scraped
from any soaked seeds (e.g., corn, bean), a potato-
tuber (a stem), any convenient fleshy root, in each
case observing (and drawing) the shape, surface-
markings, and characteristic groupings of the starch
grains, then running under the cover-glass a drop
of iodine solution, and observing the color reaction.

Experiment 21.—To see if there is starch in leaves.
1o. Extract the chlorophyll from leaves of nasturtium,

It.

22.

bean seedling, or other convenient large-leaved —
plant, by placing the leaf first in hot water to facili-
tate the extraction; second, in hot alcohol, or, after
they have been dipped in hot water, the leaves may
be left in cold 80 per cent. alcohol until the following
class period.

Describe the effect of the alcohol on the color of the
leaf, and state your inferences as to the solubility
of chlorophyll.

Place the leaf in a watch-glass, and irrigate it
with iodine solution. After a few moments pour
off the iodine, and observe the color of the leaf.
This last observation is often made more striking
by placing the leaf on a small piece of glass, and
holding it to the light. State your inferences from
this observation.

42

ANATOMY AND PHYSIOLOGY

13. If preferred, de-chlorophyllized leaves may be cut

into small pieces, boiled in water in a test-tube over
a Bunsen.flame, and the water then tested for the
presence of starch.

B. Test for Sugar:

1. We have seen that starch is a practically insoluble

carbohydrate. We also know that sugar is a read-
ily soluble carbohydrate. The chemical formula for
a molecule of starch is CsHi00;. If we combine
with this molecule one molecule of water (H2O) we
have a molecule whose composition is represented
by the formula C.Hi20¢ \(CgHi00s),, “ H,O =
CeHi20¢]. This is grape sugar. Sugar, then, differs
from starch in possessing relatively more hydrogen
and oxygen in its molecule. The process of con-
verting starch into sugar is termed hydrolysis, and
since it converts an insoluble substance into a
solubile one, it is a kind of digestion.

. The sugar ordinarily used for culinary purposes is

cane sugar. Its formula is Ci2He2O1. Explain
how cane sugar differs from starch chemically.

Experiment 22.—To demonstrate a test for the presence

of grape sugar (CgHi20s).

. The reagent commonly used for this test is called

Fehling’s solution, from the name of the scientist

who first employed it. The solution is prepared

by mixing one volume of each of the following stock

solutions with two volumes of distilled water (e.g.,

10 c.c. of each, and 20 c.c. of distilled water).

(1) 17.5 grams of copper sulphate dissolved in 500 c.c.
of distilled water.

(2) 86.5 grams of iodlinih teenies (Ro-
chelle salts) in 500 c.c. of distilled water.

7:

OCCURRENCE OF CARBOHYDRATES IN PLANTS 43

(3) 60 grams of sodium hydrate in 500 c.c. of dis-
tilled water.
The mixture, properly made, has a clear blue
color.
If the Fehling’s solution is not freshly prepared,
it should be tested, before using, by heating a por-
tion in a test-tube until it boils. If a precipitate
of red copper oxide does not form the solution is
good. It is better to make this test even with fresh
solution.

. Place a very small amount of grape sugar into a test-

tube one-third full of water.

. Shake the solution and gently warm it, then add a

few drops of Fehling’s solution.

. Describe what results. The effect is due to the

grape sugar reducing (7.e., taking oxygen from)
Fehling’s solution, forming cuprous oxide.
State the test for grape sugar.

Experiment 23-—To demonstrate a test for the

8.

iiek

II.

EZ.

presence of cane sugar.

Proceed as in the preceding experiment, using cane
sugar instead of grape sugar. Observe and describe
the result.

. Prepare a second test-tube with a solution of cane

sugar.

Add several drops of hydrochloric acid, and boil the
mixture.

Now add several drops of Fehling’s solution (enough
to neutralize the acid).

State the test for cane sugar.

Experiment 24.—To demonstrate the occurrence of

£3:

sugar in plant tissues.
Test portions of onion, beet, sweet corn, sweet

ANATOMY AND PHYSIOLOGY

potato, etc., for sugar. Describe the result in each
case.

14. Write a brief summary of what you have learned
concerning the occurrence and distribution of carbo-
hydrates in plants.

XI. FORMATION OF CARBOHYDRATES

A. The Conditions Necessary for Carbohydrate Formation:
Experiment 25.—To ascertain if light is necessary for

I.

carbohydrate formation.

A green leaf, previously partly shaded by having a
strip of black cloth closely affixed to both sides, is
to be tested for starch as described under Experi-
ment 21, after having been in the sunlight for several
hours. Record as previously directed.*

Experiment 26.—Is chlorophyll necessary for carbo-

2.

hydrate formation?

As directed under Experiment 21, test a variegated
leaf, having white areas devoid of chlorophyll.
Make three drawings of the leaf, as follows: (a)
showing (by shading) the distribution of chloro-
phyll in the tissues; (6) showing the leaf decolorized;
(c) showing (by shading) the areas that gave the
starch reaction with iodine.

B. Effects of Light on Chlorophyll:
Experiment 27—To show the need of sunlight for the

I.

formation of chlorophyll by chloroplasts.

Examine a seedling of any convenient plant that
has been allowed to develop in darkness. Compare
its color with that of another seedling of the same
species grown in daylight.

. Now place the seedling in diffuse sunlight for

twenty-four to forty-eight hours. Record the re-
sult, and state your inferences.

*The “light screen,” devised by Professor Ganong, for experiments in
starch formation by leaves, is specially recommended for this experiment,

45

46 ANATOMY AND PHYSIOLOGY

C. The Exchange of Gases in Photosynthesis:

Experiment 28.—To demonstrate the evolution of gas
in photosynthesis.

1. Observe uninjured branches of Elodea growing in
water in direct sunlight. (For individual experi-
ments one or two branches in a large test-tube of
tap-water will serve.) Describe what you observe,
coming from the basal ends, or other parts of the
stems.

2. Shade the plants for a moment by interposing a
note-book or other convenient screen between them
and the sun. Describe how the process just ob-
served is affected.

3. Make a diagram of the apparatus and material,
showing what you have observed.

4. Observe the bubbles among a mass of any green
alga floating in water, and explain their presence.
Experiment 29.—To demonstrate what gas is given off

in photosynthesis.

5. With a rubber band, or other convenient means,
fasten together (not too tightly) the cut ends of 10
or 15 clean branches of Elodea, and place them into
a glass funnel, with the cut ends extending upward.
Invert the funnel into a jar of water. The surface
of the water should rise an inch or two above the
neck of the funnel.

6. Fill a test-tube with water and invert it over the

~ neck of the funnel, being careful that no air enters
the tube. ?

7. Place the apparatus in bright sunlight, and when
sufficient gas has been collected in the test-tube,
test it with a glowing splinter. How is the splinter
affected by the gas? What gas does this test indi-
cate? The best success of this experiment requires

FORMATION OF CARBOHYDRATES 47

that the gas be tested the same day that the experi-
ment is set up. Especially avoid setting up the ex-
periment in the afternoon and testing the gas on the
following morning. Why?

Experiment 30.—To demonstrate what gas is taken

8.

Io.

If.

12.

into the plant in photosynthesis.

Into each of three large glass evaporating dishes,
A, B, and C, place a glass bell-jar having a wide,
open tubulature at the top. Into two of the bell-
jars, A and B, place vigorous, green-leaved shoots.
Into C place no shoot. Under each bell-jar place
a piece of lighted candle, 2-3 in. high, supported
on a flat cork. Now pour water into the evap-
orating dishes until it rises 2 or 3 in. up the side
of the bell-jars. The burning of the candles shows
that there is enough oxygen in the jars to support
combustion.

. Now cork the bell-jars air-tight with rubber stop-

pers. What soon results to the candle flames?
What does this tell you of the amount of oxygen
now in the jars?

Cover the jar B, containing a shoot, with opaque,
black cloth, and set all three preparations in sun-
light.

State, in a well-worded paragraph, the condition in
each bell-jar as to light, chlorophyll, and the com-
position of the air.

At the end of two or three hours, carefully lower
into each jar, successively, a lighted candle attached
to the end of a long wire. Record your observation
and inference for each jar, and your final inference
as to what gas is taken into the plant in photosyn-

* thesis, and what conditions are necessary to the

process.

XII. Tat DIGESTION oF STARCH: TRANSLOCATION

A. The Starch-content of Leaves During the Day and at

Night

Experiment 31.—To find out if starch is present in
leaves gathered in darkness as well as in light.

1. Dechlorophyllized leaves of clover (or of one of the
first five plants listed in the table in the foot-note
below), collected (a) in bright sunlight, (6) several
hours after sunset, will be tested by the instructor
for the presence of starch.

2. Did both leaves probably contain starch during
the day? From this experiment what do you
know has taken place in the leaf gathered at night?
Is starch soluble? What, then, must have occurred
to the starch?

1 Miss Ecxerson (Bot. Gaz., 48: 224-228. S1gq09) recommends the
following plants for this study, since in them photosynthesis is very ac-

tive, starch disappears from their leaves in darkness with comparative
rapidity, chlorophyll is easily extracted, and the iodine reacts quickly:

| Formation of starch in
Disappearance) light (T. 20°-25°C.) |
| of starchin | : -
Name of Plant ay "=" Ga enews Geir Iodine

cE. 78°-22°C,)| P tible | i
I
Nights days Minutes | Minutes | Minutes

Cucurbita Pepo........ I ° 15 50 | 4-15
Helianthus annuus..... | = ° 30 | 420 5
Impatiens Suliant..... | z ° 30 | 120 5
Phaseolus oulgaris..... Poe ° 20 go 5
Ricinus communis...2.| 1 ° 20 60 | §-I5
Tropeolum majus..... OF I 50 i Ce
fet MAIS oon chee 3 2 30 120 | 5

> THE DIGESTION OF STARCH 49

3. Name two advantages to the plant of this new
process you have studied.

4. The changing of an insoluble substance to a soluble
one and dissolving it 1s digestion.

5. Briefly enumerate, in order, using the proper
scientific terms, the processes that you have learned
take place in a green leaf from sunrise to sunrise
again.

B. Conversion of Starch to Sugar:

Experiment 32.—To see if starch may be digested
to sugar by an enzyme.

1. Into a test-tube one-half full of a dilute starch
mixture place several drops of iodine.

2. Add to this mixture a few drops of a solution of
diastase.

3. At intervals of fifteen to twenty minutes test for
sugar. Describe all color changes observed through-
out the experiment.

C. State with special care and detail the inferences warranted

by experiments 31 and 32.1

1 Note: The study of proteins and fats is here omitted, not being con-
sidered essential in an introductory course.

XIII. ALcoHoLic FERMENTATION

A. The development of heat by alcoholic fermentation:
1. In these experiments fresh compressed yeast may
be used, and, for a fermenting substance, either
commercial molasses (20 c.c.) in water. (100 c.c.),

or Pasteur’s solution, made up as follows:

Pasteur’s Fermentation Solution

(Shape SUSAT i Ue eee ee TSO C.C;
Ammontum tartrate, 620404. 2. 1O.C.C.
Magnesium sulphate........... 2 grams
Calcium phosphate... se se 2 grams
Potassium phosphate........... 2 grams
Distilled water... <> ot ear 838 C.c.

Experiment 33.—To ascertain what temperature change
accompanies alcoholic fermentation.

2. Place about 5 grams of compressed yeast in 250
c.c. of the Pasteur’s solution, shake well, and pour
into a Dewar flask. :

3. Place a similar amount of distilled (or tap) water
in a second flask.

4. Record the temperatures of both liquids at once,
using two thermometers which should remain in
the liquids until the experiment is over.! The
experiment will work best if the liquids are at
aboutias °C.

1 The instructor will, of course, understand the necessity of carefully
comparing the initial readings of the thermometers, where two or more are
used, and of making necessary corrections in subsequent readings.

5°

> ALCOHOLIC FERMENTATION 51

5. Set the two Dewar flasks side by side where they
will not be subject to great or unequal changes
of external temperature.

6. At frequent intervals (e.g., twenty minutes) during
the next two hours, record the temperatures of
the two fluids. Continue the records over as long
a period as convenient, not exceeding twenty-four
hours.

7. Tabulate the results, and from the figures con-
struct two “‘curves,”’ showing the rate and amount
of temperature change in each flask.

8. State your inferences from this experiment.

B. The gaseous exchange in alcoholic fermentation:

Experiment 34.—To ascertain what gaseous exchange
accompanies alcoholic fermentation.

1. Place 250 c.c. of fermenting mixture into a tall
glass cylinder, and 250 c.c. of distilled water into
a similar adjacent cylinder, as a control. At
once test the air in the cylinders above the liquid
with lime water, to see if the latter turns milky,
as a result of the formation of a precipitate of
carbonate of lime.

2. After the test for COz, test the air in both cylinders
with a lighted splinter or taper, to see if it contains
sufficient oxygen to support combustion. The
taper should be rapidly lowered into and removed
from the cylinder. Why? _

1 If the members of the class are not familiar with the effect of CO, on
lime water, this should be demonstrated by the instructor, using both
chemically prepared CO: and the breath from the lungs, before proceeding
with the experiments in fermentation and respiration.

The air in the cylinder may conveniently be tested by first dipping a
small wire loop (e.g., 10 mm. in diameter) into lime water. A film of the
lime water will form across the loop, and may thus be transferred into the
cylinder.

§2 ANATOMY AND. PHYSIOLOGY

3. Place a greased glass plate over each cylinder, or
close the cylinders with a rubber stopper, and after
an interval of about one hour (at a temperature
of about 25°C.) repeat the tests for O and COQ:.
Test again after two or more hours.

4. Record and interpret your results, especially dis-
cussing any circumstances that may have operated
to affect the progress of the experiment either favor-
ably or unfavorably.

C. The Formation of Alcohol Demonstrated:
Experiment 35.—To test for the presence of alcohol.
1. After the fermentation in the last experiment has
' proceeded for twenty-four hours, distill about 150
to 200 c.c. of the fermenting liquid, and redistill the
first distillate.

2. Test a portion of the second distillate with a flame
to see if it willburn. If it will, describe and explain
the result. |

3. The presence of alcohol may also be tested, in
either the first or the second distillate, by adding to
it several drops of a mixture composed of a strong
aqueous solution of bichromate of potash, to which
have been added a few drops of sulphuric acid. If
a green color results, the presence of alcohol is
indicated.

4. Briefly summarize the products of alcoholic fer-
mentation, ascertained by the above experiments.
From where did these products come, and what
was the active agent in their formation?

XIV. RESPIRATION

A. Anaerobic Respiration:
Experiment 36.—To illustrate anaerobic respiration.

Be

Remove the seed-coats from three or four pea seeds
that have soaked in water over night.

. Fill a large glass test-tube with mercury, and

invert it in a bath of mercury.

. Place the pea seeds under the mouth of the inverted

test-tube, and allow them to float to the top. Use
every possible precaution to prevent air being car-
ried up with the peas. Can the presence of air
be entirely prevented?

. Securely fasten the test-tube in the inverted posi-

tion, with its mouth under the surface of the mer-
cury in the bath, and during the next twenty-four
to forty-eight hours observe the formation of
gas, which replaces the mercury around the seeds.

. Now introduce into the test-tube with the pea seeds

a small piece of potassium hydroxide. If the gas
given off by the seeds is CO. it will be absorbed by
the potassium hydroxide, and the mercury will rise
in the tube.

. Do these seeds respire under strictly anaerobic con-

ditions? Discuss, iny our note-book, all the pros
and cons, and endeavor to make a clear statement
of just what this Experiment does and does not
demonstrate.

B. Aerobic Respiration:
Experiment 37——To demonstrate what exchange of

gases accompanies the aerobic respiration of a living
plant.
53

54

ANATOMY AND PHYSIOLOGY

. Place a vigorous potted plant on a ground-glass

plate. By the side of it place a watch-glass full of
lime water, or baryta water; over all place a glass
bell-jar with a large tubulature at the top.

. Make the joint between the bell-jar and the ground-

glass plate air-tight by means of vaseline.

. Test the air in the jar with a lighted taper to be sure

that it contains enough oxygen to support combus-
tion.

. Insert a rubber stopper into the tubulature so as

to make it air-tight, and set the plant aside, in a
dark place. Why?

. At the next laboratory period (preferably on the

following day), and without disturbing the bell-jar,
observe the color of the lime water in the watch-
glass. What does it indicate?

. Quickly and cautiously insert a lighted taper into

the bell-jar through the tubulature. What results?
What inference is justified?

Experiment 38.—To see if all parts of a plant, and non-

Io.

green plants, respire.

. Take six cylindrical glass jars, a, b, c, d,e, and f,

provided with air-tight rubber stoppers.

. Into (a) place a quantity of green leaves; into (6)

green stems of some herb; into (c) young clean
roots of some herb; into (d) freshly picked flowers;
into (e) one or two fresh fleshy fungi; and into (/)
nothing. Confine the plant material to one side
of the jars by inserting a vertical partition of coarse
wire netting.

. Test the air in each jar to be sure that it will sup-

port combustion, then cork the jars air-tight, and
place them in a convenient place.
At the next laboratory period carefully test the air

RESPIRATION 55

in each jar with the burning taper. What infer-
ence may be drawn from the result?

11. Next, pour into each jar a bit of clear lime water,
and wash the air by tipping the jars back and forth,
holding the half containing the plant material upper-
most. What conclusion does the result justify?

12. Clearly state the general conclusion from this ex-
periment.

C. The Temperature Change Accompanying Plant Res-
piration: |

Experiment 39.—To ascertain what temperature change
accompanies the respiration of germinating seeds.

1. Place a quantity of germinating seeds (¢.g., oats,
wheat, lupine) into a Dewar flask. Into a second
Dewar flask place nothing.

2. Into each flask insert a thermometer (being sure
first to compare their readings). The bulb of the
thermometer in the flask containing the seeds
should be well covered by them. Place the flasks
where they will not be subject to great nor unequal
changes of external temperature.

3. After twenty-four hours record the temperature
indicated by each thermometer.

4. Thoughtfully discuss and interpret the results ob-
served.

5. Compare the process of fermentation with that of
respiration. What inference is suggested by this
comparison as to the real nature of respiration?

XV. THE INFLUENCE OF EXTERNAL CONDITIONS ON THE

PLANT

A. The Influence of Gravity on the Direction of Growth:
Experiment 40.—To find how gravity affects the direc-

I.

1

tion of growth of roots and shoots.
Choose two or three young seedlings of the pumpkin
or lupine, with radicles about ro mm. long.

. Pin the seedlings horizontally on a cork and place

in a moist chamber in the dark (why in the dark?)
until the next period. A Petri dish will furnish a
simple moist chamber.

. Make a drawing of the seedlings in the horizontal

position.

. At the next laboratory period observe the position

of both root and shoot. Draw.

. Do the results give any evidence that the root grew

downward and was not pulled down by gravity?
Explain.

B. Influence of Light on the Raie of Growth of Stems:

I.

Compare the lengths of the stems of seedlings of the
same age that have grown, one in the dark, the other
in the light. State the exact length of each of the
stems in centimeters.

. What do you infer is the effect of light on the rate

of growth of stems of the plants observed?

. Do you think this is true of all plants? (This point
should be discussed with the instructor, in the light

of more recent investigations on the subject. See
especially, MacDougal, “The Effects of Light and
56

INFLUENCE OF EXTERNAL CONDITIONS ON THE PLANT 57

Darkness on Growth and Development.’? Memoirs
of the New York Botanical Garden, No. 3.)
C. The Influence of Light on the Direction of Growth of Roots
and Stems:

Experiment 41.—To ascertain how one-sided illumina-
tion affects the direction of growth of roots and
stems. |

1. Fix a vigorous young seedling of white mustard
with the root extending through the mesh of a piece
of cheese-cloth stretched over the mouth of a large
salt-mouthed bottle nearly filled with tap-water.
The seedling should be as straight as possible, and
stand vertically at the beginning of the experiment,
with root extending well into the water.

2. Place the plant thus prepared into a box with a
tightly fitting cover and a narrow, vertical slit at
one side to admit the light. (A pasteboard shoe-
box with the cover on, and the slit cut vertically
in the cover will answer.)

3. Set the box and plant in a well-lighted window,
with the slit toward the light.

4. Make a diagram of the entire apparatus and plant,
in longitudinal section.

5. At the next laboratory period carefully remove the
cover from the box and observe the position of the
root and stem.

6. Draw another diagram similar to, and by the side
of the first one, showing what you observe.

7. Compare the manner of response of the root and
stem to one-sided illumination.

PART II
MORPHOLOGY AND LIFE HISTORY

I. MEANING OF THE TERMS

A. Morphology—Under Part I we considered various
physiological processes, the primary result of which was
to maintain the life of the individual plant. Most of
those processes were found to be carried on by all
plants. 1tis common knowledge, however, that plants
differ widely from each other in both structure and
habit of life. In other words, we recognize the fact of
variation. ‘This means that different plants solve the
same problems of life in different ways. That phase of
botany which concerns itself with a comparative study
of structures, and seeks to interpret the structural value
of an organ, no matter how it may be disguised, is
termed the science of form, or morphology.

B. Life History —Every plant, in the course of its exist-
ence, passes through a series of changes, in orderly
sequence. Like an animal, every plant begins life as
a single cell, the egg, or the equivalent of an egg;
the egg (except in some of the lower plants) develops
into an embyro, and the embryo grows and develops
into an adult. The adult in turn, produces an egg,
like the one from which it came, thus completing one
life cycle and initiating another. These various
changes constitute the life history of the individual.

59

60
ee

MORPHOLOGY AND LIFE HISTORY

Descent.—Just as one of the higher plants, such as a
maple tree, begins life as a single cell, and becomes
more and more complex as it matures, so the plant
kingdom as a whole, presents us with a series of organ-
isms of gradually increasing complexity from the sim-
plest one-celled forms to myriad-celled, complex forms.
This fact suggests that the entire plant kingdom, like
every individual plant, has had a developmental his- |
tory, the more complex organisms being derived from
more simple ones by a series of gradual changes. ‘This is
the theory of descent, ororganicevolution. It teaches
us that all organisms are related to each other, and
is one explanation of why we so often find the same
organ appearing again and again, under various guises,
in plants externally unlike.

. Classification—The study of morphology and life

histories enables us to recognize relationships among
plants, and hence to build up a genealogical tree,
showing lines of descent. Thus we can arrange plants,
together with their nearest relatives, in groups; and
related groups, again, in larger groups of successively
higher orders. This gives us a rational basis for the
classification of plants, and this phase of plant study
is called systematic botany, for it makes possible
the arrangement of plants into a system, which en-
deavors to show how the plant kingdom, in all its diversity,
has developed, or evolved. This greatly simplifies our
study of plants, for the number of different plants is too
great for us to study every one; but if we recognize
that each plant more or less imperfectly illustrates
a group, then we can study an illustration of each
group, and thus get a more nearly adequate picture
of the kingdom of plants as a whole. The various
systematic groups are given in E below.

MEANING OF THE TERMS

61

E. An Outline of the Classification of Plants:'

THE GREAT GROUPS OF PLANTS

Division

I. Thallophyta...

fas Hryopnvta.: ssc oo cmc bales ca

Eh. Pteridophytae.. 326. oa esc se

PVE riamGphnytacs. 2 esn.6 suecte tae

WV. ReEpidophy ta: 25.2. side eles bien

wae Cyendopltytas. cie.d 1s cslonee

1 For reference, not memorizing.

me WN &

Class

. Cyanophycee
. Chlorophycesz
. Pheophycez

. Rhodophycez#
. Myxomycetes
. Schizom ycetes

(Bacteria)

. Phycom ycetes

. Ascomycetes

- Basidiom ycetes
. Fungi imperfecti

(life histories

Order

imperfectly known)

. Hepatice........

. Eusporangiate.....

. Leptosporangiate.

. Lycopodinee.......

: Hecidedesdears ; { Ses

. Cycadofilicinee. ..
- Cycadinex’... 5.5.5.
. Bennettitinee......

. Cordaitinee......

Ricciales
Marchantiales
Jungermanniales
Anthocerotales

{ Andreales
Sphagnales
Bryales
Ophioglossales
Marratiales
Isoetales

f Filicales

' \ Marsiliales

- Sphenophyllinee.. .
. Equisetinee......
. Calamarinee.......

Sphenophyllales
Equisetales
Calamarales

Lycopodiales

Lepidodendrales
Cycadofilicales
Cycadales
Bennettitales

Ginkgoales
Gnetales

Cordaitales

62 MORPHOLOGY AND LIFE HISTORY

THE GREAT GRoUP OF PLANTS—(Continued)
Division Subdivision Class Order

A. Gymno- see Coniferales
1. Pinoidew:.. 5.52.5.

sperme Taxales
Pandanales
Naidales
Graminales
Arales
Xyridales
Liliales
Scitamnales
Orchidales
Orders, including
Salicales

1. Monocotyledonez

2. Dicotyledonee.....
VII. Spermatophyta

Apetale Rosales
Polypetale Violales
Myrtales

Um bellales
Ericales
Polemoniales
Plantaginales
Rubiales
Campanulales .

(b) Metachlamydez
Sympetale (=

32
= ee Polygonales
SPEr (a) Archichlamydez | Ranunculales
Gamopetale) |

2. DIRECTIONS FOR STUDY

Polypodium vulgare (ComMMON POLYPODY)

A. Classification:
Division III. Pteridophyta (fern plants).
Class I. Leptosporangiate.
Order. Filicales.
Family. Polypodiacez.
Genus. Polypodium.
Species. vulgare.
B. Habitat:

1. Record here your knowledge of the habitat of the
specimen studied. The information is to be ob-
tained from your own observation, and from your
reading and class work.

THE “FERN PLANT’

C. Naked-eye Characters:
1. General features.

(a) Note that the sporophyte is differentiated
into root and shoot.

(b) The leaf portion of the shoot is often called the
frond. The fibrous roots and the leaves are
borne on an underground stem (rhizome).

(c) Make a sketch of the entire sporophyte (in-
cluding only one leaf).

2. The rhizome.
(a) Describe the natural attitude (7.e., erect, or

horizontal) of the rhizome. Where does it
63

64

(0)

(c)

MORPHOLOGY AND LIFE HISTORY

grow? If it branches, describe its manner
of branching.

Does the rhizome bear any outgrowths besides
the leaves and roots? If so, describe their
structure, color, relative number, and location.
The places on the rhizome where the leaves are
borne are called nodes. What is the region
between two nodes called?

Note-—The directions below (d~) apply especially to
the bracken fern, Pieris aquilina.
(d) Observe the end of a rhizome cut squarely

_(e)

across. If preserved material is used, the cut
surface should be kept moistened during the
study. The observations may best be made
from a piece 5 to 10 mm. thick, cut transversely
and placed in a watch-glass of water. Do not
cut or injure you specimen in any way, as it
will be collected for further preservation at the
end of the study.

Distinguish the following tissue-regions:

(1) Theepidermis (black in preserved material).

(2) Underneath the epidermis a narrow, dark-
colored region of hypodermal sclerenchyma.

(3) Within the hypodermal sclerenchyma the
fundamental tissue (parenchyma).

(4) Imbedded in the parenchyma two promi-
nent elongate, dark-colored areas, the central
sclerenchyma, or stereome (sometimes fused
into one).

(5) Also imbedded in the parenchyma, and sur-
rounding the inner sclerenchyma, several
areas of fibro-vascular bundles. In fresh
specimens these areas are yellowish, in
preserved material they are lighter colored

DIRECTIONS FOR STUDY 65

than the inner sclerenchyma. How do
they appear when a section is held to the
light?

({) Identify all the areas referred to above (e, 1-5)
in a longitudinal section of the rhizome.

(g) At home, write a well-worded description of
your observations under e and f.

(h) Make a diagram, 10 cm. in longest dianeter,
showing carefully the outline of the rhizome as
seen in cross-section, and all the tissue-regions
identified. Label each region, and underneath
your drawing indicate the amount of enlarge-
ment.

(i) Underneath the first diagram make a second
one, of the same enlargement, showing the rela-
tion of the tissues of the rhizome as seen in
longitudinal section.

. The roots.

(a) Describe the location, form, length, diameter,
branching, relative number, and relation to
each other (.e., close together or not; inter-
woven or not) of the roots. Draw.

. The leaves.

(a) On what surface of the rhizome are the leaves
borne?

(b) Note their differentiation into stem-like part,
the petiole, and expanded portion, the blade.

_ (c) What is the color of the leaf? Describe and
suggest a probable reason for any differences in
color.

(d) Is the petiole glaucus (smooth, without hairs),
or pubescent (hairy) ?

(ec) Is the blade entire, or divided into pinne? If
the latter, do the clefts between the pinnz ex-

66

(f)

(g)

(z)

(7)
(f)

(2)

MORPHOLOGY AND LIFE HISTORY

tend clear to the midrib? Compare the basal
with the more distal clefts in this respect.

Do the pinne appear to be all of the same age?
If not, state reasons for considering some of
them younger than others. Find evidence in
your specimen of the method of formation of
the pinnz. Are they opposite or alternate?
Describe and compare the venation of the blade,
and of the individual pinne. Describe any
constant relationship between the venation and
manner of branching of the blade.

Do the smaller veins anastomose (7.e., have their
ends united so as to form a network), or are
their ends free? Compare the fern leaf in this
respect with the foliage-leaf of a seed-bearing
plant. :

Describe the appearance of very young, unex-
panded leaves or portions of leaves.

On the ventral surface of some of the leaves find
the brownish fruit-dots, or sori (sing. sorus).
Describe their location. Do you find them on
the midrib of the frond or on the individual
pinne? Are they between the smaller veins or
on them? If the latter, on what part of the
vein? Is their position constant (i.e., always
the same)? Are they located at the margin of
the frond or pinna, or back EEE the margin?
Describe their shape.

Do the sori occur on all the pinne of a leaf?
On all the leaves? Compare several specimens
with reference to this point.

(m) Observe, using hand lens if necessary, that the

sorus is composed of a group of small organs
(sporangia). What do sporangia produce?

DIRECTIONS FOR STUDY 67

(n) Is there a membranous expansion (indusium)

(0)

(p)
(9)

(7)

covering the sporangia in your specimen? Ex-
amine fronds of the other species of fern dis-
played in the laboratory and record your obser-
vations on this point, stating the names of the
species observed.

Leaves bearing spores are sporophylls. Fern
leaves that do not bear spores are vegetative
leaves or foliage-leaves.

Do some of the sporophylls also function as
foliage-leaves?

Examine specimens of other kinds of ferns ex-
hibited in the laboratory and see if your answer
to (p) is true of all ferns. Describe briefly any
exceptions found, giving the name of the fern.
Make drawings, natural size, illustrating all
features of the frond not clearly shown in your
first sketch.

D. Microscopic Characters:
1. The rhizome.
(a) Study prepared slides of cross-sections of the

_ (6)

(c)

rhizome. (Pteris aquilina is suggested as spec-
ially satisfactory for this study, a-g.)

With the low power survey the section and
identify the various tissue-regions already dis-
tinguished.

With the high power, study the epidermis, and
describe how many cells it is in thickness, the
variation in thickness of the cell-walls, the
middle lamella, separating the adjacent cells,
and the canals, or channels, extending from the
cell-cavity outward through the cell-wall. Do
these canals ever branch? Do they form a

68

(d)
(e)

(g)

MORPHOLOGY AND LIFE HISTORY

network? Is there any connection between

the cell-cavities of adjacent cells?

In a similar manner examine the cellular struc-

ture of the hypodermal sclerenchyma. 3

Make drawings illustrating the features ob-

served in (c) and (d), showing four cells of the

epidermis, and three or four of the underlying
sclerenchyma-cells. The cells should not be
less than 10 to 15 mm. in diameter.

Make similar studies and drawings oi the cells

of the parenchyma.

Study one of the smaller fibro-vascular bundles

and distinguish, from the circumference toward

the center:

(z) The outer bundle-sheath, or endodermis.

(2) Within the endodermis, and adjacent to it,
a single layer of starch-bearing parenchy-
matous cells, the phloem-sheath.

(3) Thick-walled bast-fibers.

(4) Larger, thin-walled cells, having their cell-
walls perforated, the sieve-tubes.

(5) Associated with the cells mentioned in
(2)-(4), parenchyma-cells (phloem-paren-
chyma), containing starch.

(6) The cells mentioned in (3)—(5) constitute
the phloem-region, of the bundle, or
phloem.

(7) Within the phloem is the xylem-region, or
xylem, composed of

(8) Large, conspicuous tracheids, whose walls
have ladder-like (scalariform) markings as
seen in longitudinal section. Each tra-
cheid is a tube, filled with air, and formed

DIRECTIONS FOR STUDY 69

by the fusion of several cells through the
disappearance of their end walls.

(9) Smaller sieve-tubes, resembling those of
the phloem.

(10) Thin-walled cells forming the wood-, or
xylem-parenchyma.

(x1) Since the tissues of the fibro-vascular
bundles are arranged circularly about a
common center, the bundle is called a
concentric bundle.

(12) Compare the various bundles and see if
they are all of similar structure.

(13) Make a careful drawing showing the
structure of the bundle, including all points
mentioned under (g), (1)—(10). This draw-
ing should be at least 75 mm. in longest
diameter.

2. The pinna.

(a)

(0)

(c)

(d)
(e)

Under the low power examine a small portion of
one of the pinne or pinnules not bearing a
sorus, and note the presence or absence of
outgrowths.

Can you observe any veins too small to be seen
with the naked eye? If so, describe their re-
lation to each other.

Mount a small bit of the lower epidermis, and
describe (a) any outgrowths; (b) the stomata
and guard-cells, stating the number, shape,
and contents of the latter. Describe the rela-
tive number and distribution of the stomata.
Compare the stomata of the fern with those of
a seed-bearing plant.

Make drawings showing all features shown

| under 2, (b)-(d).

7°

MORPHOLOGY AND LIFE HISTORY

(f) Describe a cross-section of a pinna as shown in
a prepared slide. Draw. Compare its struc-
ture with that of a foliage-leaf of a higher plant.

E. Non-sexual Reproduction:

I.

Describe the possibilities of vegetative propagation
of the sporophyte.

. With a needle remove several sporangia from a

sorus, mount them in water and study under low
power.

. Observe the differentiation of the sporangium into

a stalk (pedicle), and a spore-case, containing
spores. Note the walls of the spore-case, and the
row of thickened cells, the annulus. Describe these
cells. Note the special opening in the spore-case,
through which the spores escape between the
lip-cells.

. Make a drawing of the sporangium, about 35 mm.

in shortest diameter, showing a portion of the
pedicle.

. Study the shape and surface markings, if any, of

a single spore. Account for the shape. Are they
all of substantially the same size, z.e., is Polypodium
a homosporus pteridophyte?

. Make a drawing of the spore 15 mm. in longest

measure.

. Run a drop of glycerine under the cover-glass and

carefully watch for the snapping motion of the
sporangia by which, in nature, the spores are
expelled.

8. Explain the advantage to the species of having the

spores expelled. Why would it not be as well if
they merely dropped out of the spore-case?

9. If suitable material is at hand, study stages in the

germination of the spores.

DIRECTIONS FOR STUDY a

10. To which of the alternating generations does the
fern-plant belong? Why?
11. Into what does the spore develop?

THE PROTHALLUS

F. Habitat:

1. State the locations and conditions of growth of the

prothallus (also called prothallium), (a) in artificial
culture; (6) in nature.
G. Naked-eye Characters:

1. Describe the exact size (in millimeters), color, and
shape of the prothallus.

2. It is differentiated into a dorsal and a ventral sur-
face? Ifso, how are the two surfaces distinguished ?

3. Describe the location and character of the rhizoids.

H. Microscopic Characters:

1. Mount a prothallus in water or clearing fluid, ven-
tral side up, under.a cover-glass.

2. Describe the structure and contents of the cells.

3. Describe variations in thickness. Do you find a
thicker central portion, or cushion?

4. Observe the growing point in the notch.

5. Study the location and character of the rhizoids.
Are cross-walls present?

I. Sexual Reproduction:

1. Among the rhizoids find small, spherical elevations,
the antheridia. Describe their number and dis-
tribution.

2. Nearer the notch observe the archegonia, appearing
to be composed of four cells, surrounding an opening
or canal.

3. Make a drawing, at least 5 cm. in longest diameter,
showing all features of the prothallus thus far

72

Io.

i

MORPHOLOGY AND LIFE HISTORY ~

observed. By the side of this figure draw an out-
line of the prothallus, natural size.

In fresh specimens motile antherizoids or sperms
may be found escaping from the antheridia and swim-
ming in the water. If these are found, observe the
body of the sperm and the cilia. How many cilia
are there? Draw.

. If prepared slides are supplied, study cross-sections

of the prothallium passing through an antheridium
and an archegonium. Describe accurately, noting
the differentiation of the archegonium into a neck,
containing a neck-canal, and a venter, containing
an odsphere or egg.

. Make a diagram of the section, of the same scale

as the drawing in 3 above, and make drawings
showing details of structure of the antheridia and
archegonia as seen in longitudinal section.

. To what class of reproductive bodies do the sperm

and egg of the fern belong? To which of the alter-
nating generations does the prothallus belong?
Why? Why is it called a thallus?

. Is this fern moneecious or dicecious? Explain.
. What structure is the starting point of the sporo-

phyte?

Diagram the life history of the fern for three genera-
tions, by continuing the following diagram; letting
G = gametophyte; s = sperm; e = egg; S = sporo-
phyte; sp = asexual spore:

GC YS?, etc.
s

Make a diagram to show the life cycle of the fern,
using arrows and words, arranged in a circle.

DIRECTIONS FOR STUDY 73

K. Nutrition and Growth:

1a

Is photosynthesis carried on by both gametophyte
and sporophyte? ‘Transpiration? Absorption of
water from the soil?

. Explain the need of stomata in the sporophyte. Are

they present in the gametophyte? Explain.

. Discuss the presence or absence of a conducting

system in the prothallium and sporophyte.

. Explain how the presence of the cushion of the pro-

thallium is related to the needs of the young sporo-
phyte.

. Is the gametophyte of Polypodium ever dependent

upon the sporophyte for its nutrition? Its exist-
ence?

L. Comparison of Gametophyte and Sporophyte of Poly-
podium:
Copy the following table into your note-book, and mark

Generation

x after the word gametophyte or sporophyte in the
proper column.

TABLE I

1 oO 7) 1 Ww ie)
0 Oo Vo oO cog
3) of ;

on Sees est tie Ah ioe we
one oat 43 ae = oS =O wor
n n n ele) site} ORO
a | ei OK x b o Ko i)
soy es me o & s ies o> oun
» S 3 an ° or a, ap op eo}
4) oe ee ee ee g o | 9ag
= ° = 3 .
2G OE be = a cs a = =
S/e2iS/a | Fk] os | els! se] se] gos
~iAl/ni|eM|/al}oala |B] ma] ma | os

Polytrichum commune (ComMMON HAIR-CAP Moss)!

A. Classification:
Division II. Bryophyta (moss-plants).

Class II. Musci (mosses).

Order. Bryales.

Family. Polytrichacee.
Genus. Polytrichum.
Species. commune.

B. Habiiat:

I.

Polytrichum commune is widely distributed, growing
in the soil in fields and woods.

C. Naked-eye Characters:

4.

THE GAMETOPHYTE (THE ‘‘MosSs-PLANT’’)

. Note that there are two kinds of leafy ‘“‘moss-

plants.”” The one having the cup-like tip is the
male or antheridial plant; the other, without the
cup-like tip, is the female, or archegonial plant.
Compare the average height of the mature male
and female plants. Do you find any outgrowth
from the tip of any of the archegonial plants?

. Are the moss-plants differentiated into root and

shoot? Js the shoot further differentiated? If
so, describe.

. Briefly describe the extent and ramifications of the

“root”? system. Are these true roots, with root-
hairs?
Briefly describe the arrangement of the leaves on

1 With minor modification the outline here given for the study of the
moss will serve for species of Mnium, Funaria, or almost any other com-
mon moss.

74

POLYTRICHUM COMMUNE 75

the stem (opposite, alternate, spiral). Are the
leaves sessile or petiolate? Simple or compound?
Is there a midrib? Veins? Compare the dorsal
and ventral surfaces of the leaves. Describe
any variations in the leaves on various parts of
the stem. Describe the margin of the leaf-blade
(i.e., entire, notched, serrate, etc.), and the shape of
its apex and base.

. Compare the form of the leaves in the same regions
of the male and female plants. Note especially
the rosette of perichztz (modified leaves) at the
summit of the male plant. Compare them with
the foliage-leaves below them.

. Describe the form of the stem. Is it of uniform
diameter? Does it branch? Compare the stems
of the male and female plants.

. Make suitable drawings, illustrating all points
observed under C 1-6.

THE SPOROPHYTE

. Select an archegonial plant with sporophyte (sporo-
gonium) attached. Distinguish the long stalk
or seta, bearing at its summit the spore-case, or
sporangium. How many millimeters long is the
seta? Describe its surface; its diameter throughout;
its shape in imaginary cross-section. If it is angled,
how many angles are there? By taking hold of
the seta near its attachment to the gametophyte
and carefully pulling, separate the sporogonium
from the gametophyte. State, with full reasons,
whether or not the tissue of the foot appears to be
continuous with that of the gametophyte. Does
anything like grafting of the sporophyte onto the
gametophyte take place?

76

“EO:

Io.

EE.

MORPHOLOGY AND LIFE HISTORY

. Do you find a swelling of the seta (apophysis),

just beneath the sporangium? If so, describe and
locate it accurately. Do its cells contain chloro-
phyll? Of what function 1s, or is not, the apophysis
therefore capable?

Remove and study the cap (calyptra) that fits
over the sporangium. Describe its shape, margin,
character of surface, outgrowths, if any.

Study the color, shape, and other features of the
sporangium disclosed by removing the calyptra.
Measure its length and breadth. Describe its
attitude on the seta (7.e., erect, pendant, etc). De-

scribe its outline in imaginary cross-section. If

ne.

£2.

EA

it is angled, record the number of angles.

Describe the shape and surface of the lid (operculum)
at the end of the sporangium, and just under the
calyptra. ;

Make a drawing, ten times natural size, showing
the sporangium, the calyptra removed, and a por-
tion of the seta.

Carefully remove the operculum and preserve it.

. On the margin of the sporangium, underneath the

15.

o7.

operculum, observe the circle of teeth-like organs
(peristome). Record the number of teeth. Is
this number constant? Is it always either even
or odd?

In fresh dry specimens describe the effect of the
breath upon the position of the teeth of the peri-
stome.

Describe the membrane (epiphragm) within the
peristome, and covering the end of the capsule.
Is it perforated? What is its relation to the teeth
of the peristome?

Make a drawing, 30 mm. in diameter, illustrating

18.

IQ.

20.

2I.

22.

23.

POLYTRICHUM COMMUNE 77

an end view of the sporangium with the operculum
removed. Make a drawing of the operculum,
also 30 mm. in diameter.

With the razor carefully make a longitudinal section
of the capsule, just to one side of its central axis.
Observe the wall of the sporangium; a central
organ (columella); and, between the two, a mass
of spores.

Describe the structural relation of the columella
to the epiphragm. What, in reality, is the latter?
Describe the relative number, color and attach-
ment or non-attachment of the spores, so far as
may be ascertained without the aid of the micro-
scope. |

Make a drawing, ten times natural size, illustrating
everything observed under 18-20. —

From the above observations construct a diagram of
an imaginary cross-section of the sporangium near
the middle. Compare the diagram with an actual
cross-section.

Carefully preserve the sporophyte in a covered
watch-glass or other convenient moist (not wet)
place until the next laboratory period, or proceed at
once with the following observations (D):

D. Microscopic Characters:

I.

THE SPOROPHYTE

With a sharp scalpel remove a thin piece from the
base of the sporangium, cutting parallel to the sur-
face, and mount it in water with the outer surface
uppermost.

. Examine the mounted tissue under the low, then

under the high power, to see if stomata are present.
If they are, describe them and their distribution.

78

on

MORPHOLOGY AND LIFE HISTORY

Compare them with the stomata of a foliage-leaf
of one of the higher plants, including the number,
shape, and other characters of the guard-cells. In
like manner compare them with the stomata of the
fern. State, with reasons, which type of stomata
you consider the more primitive. Look for stomata
on the surface of the apophysis.

. Study thin cross-sections of the sporangium (sec-

tions of the half (C, 18) will serve). Identify the
parts already studied, and their characters and
relationship as seen in cross-section. Make your
drawings at least 20 mm. in radius.

. Describe the shape of the spores, and their manner

of attachment or non-attachment, as seen under
high power. Of how many cells is one spore com-
posed? Make a drawing of three spores making
each 10 mm. in longest measure.

. Mount thin cross-sections of the seta, and study

under high power.

. Distinguish the outer layer, epidermis. How

many cells thick is it? Observe the central strand,
and between this and the epidermis a thin-walled -
tissue (parenchyma), and a layer of thicker walled
cells (sclerenchyma). State how these various
tissues may be distinguished from each other. Of
what value is the sclerenchyma? The central
strand is comparable with the fibro-vascular bundle
of the seed-bearing plants. Draw.

THE GAMETOPHYTE

The Leaf.

7:

8.

Remove an entire leaf and mount it in water. Ob-
serve under low, then under high power.
How many cells thick is it. Is it of uniform thick-

» POLYTRICHUM COMMUNE 79

ness? Describe. Are stomata present? Why?
How is the midrib distinguished? Describe the
leaf-margin and apex. Describe any differences
in the two sides of the leaf.

9. Describe fully the contents of a single cell, as
observed under high power.

10. Illustrate by suitable drawings all features observed
under D, 7-9.

The Stem.

rz. Study, under the low power, cross-sections of the
stem mounted in clearing fluid (or use prepared
slides).

12. Describe the tissues observed, and their relation to
each other. Compare the structure of the game-
tophyte-stem, as seen in cross-section, with that of
the sporophyte-stem, and name the tissues of the
former, using the terms given above (D, 6).

13. Illustrate by a drawing, at least 50 mm. in diameter,
the structure of the stem as seen in cross-section.

E. Non-sexual Reproduction:

1. In some mosses a second gametophyte often devel-
ops from the tip of an older plant. This is called
proliferation. Frequently this may be repeated a
number of times, forming a chain of plants, each
younger one growing out of the apex of the next
older one. Examine the material at hand, and, if
such a condition is found, describe it, with drawing.
What kind of reproduction is this?

2. Explain the advantage to the species of the elon-
gation of the seta.

3. If stages in the germination of the spores are avail-
able, study this process. The structure imme-
diately developed from the spore is the protonema.

80

“MORPHOLOGY AND LIFE HISTORY

Describe-its color. Is it simple or branched? Are
cross-walls present?

4. At certain points on the protonema observe buds.
These buds develop into either male or female game-
tophytes (gametophores).

5. Which generation of the moss-plant always devel-
ops from the spore? Compare this with the case in
the fern.

Sexual Reproduction:
The antheridia

1. Take a male gametophyte and, with a dissecting
needle, carefully remove some of the antheridia,
borne in the rosette at the summit of the plant.
Mount them in water, and study them under the
microscope.

2. Describe the shape and other structural features
of the antheridia. What is their color? Compare ~
them with the antheridia of the fern.

Do you find paraphyses associated with the anther-
idia? If so, describe them, and state how they
may be distinguished from the antheridia.

4. If prepared slides are available, study longitudinal
sections through the tip of the male gametophyte,
observing the mode of attachment of the antheridia.

5. With high power study the sperms (spermatozoids)
within the antheridia.

6. In fresh specimens the.sperms may be seen swim-
ming about in the water. If motile sperms are
present, endeavor to make out the number and
character of their organs of locomotion (cilia). Do
the cilia precede or follow as the sperm moves for-
ward? Do the motions of the sperm appear to be
purposeful or not? Give reasons for your answer.

. POLYTRICHUM COMMUNE 81

7. Make drawings showing all features observed under
F, 1-6. The antheridia should be at least 25 mm.
long; the body of the sperms ro mm. long.

The archegonia

8. With the female gametophyte make studies as
directed above (F, 1-4).
g. In the archegonium distinguish the venter, neck,
and lid-cells. Is the archegonium sessile or stalked?
to. If prepared slides are available, identify the
odsphere, or egg, and the neck-canal. How many
cells thick is the wall of the archegonium? Is this
uniform?

11. Make a drawing, at least 35 mm. long, showing all
features observed under F, 8-10.

12. Describe the conditions, processes, and organs in-
volved in sexual reproduction in the moss. Explain
whether or not it is of advantage to the moss-plants
that they grow so close together.

13. Into what does the fertilized egg develop? Where
does it develop?

G. Nutrition and Growth:

The gameiophyte

1. Is the gametophyte of the moss capable of elabor-
ating its own carbohydrate food? Explain. Is it
dependent upon the sporophyte at any period of its
existence? Explain. |

2. How does the possession of leaves affect the surface-
area of the chlorophyll-bearing tissues? Explain
how this affects the process of photosynthesis.

1 This may be assigned for home work and serve as the basis of class
discussion, or of written work to be handed in.
6

82

Io.

2 Be

I2.

12:

14.

MORPHOLOGY AND LIFE HISTORY

. State the organs and processes by which water and

inorganic salts are taken in by the gametophyte.

. Explain the presence or absence of stomata in this

plant.

. By what organs is the respiration of the gameto-

phyte carried on?

. Does the gametophyte have to elaborate food in ex-

cess of its own needs? Explain. Explain the need
or lack of need of conducting tissues in the gameto-
phyte.

. Name two ways in which the gametophyte is kept

rigid and erect.

The sporophyte

. Can the sporophyte lead an independent existence

at any time in its history? Explain.

. By what organ or organs, by what process, and from

what source are water and dissolved food substances
taken into the sporophyte?

Is photosynthesis possible in the sporophyte at any
period of its existence? What is the source of its
carbohydrate food?

Explain the need or lack of need of conducting tis-
sues in the sporophyte. Compare the degree of
development of these tissues in the sporophyte and
gametophyte of the moss.

Explain the significance of the presence or absence
of stomata in the sporophyte.

Refer to the question in F, 13, and explain the origin
of the calyptra. To which generation does it be-
long? . Explain. |

Explain the advantage of sclerenchymatous tissue
in the sporophyte. Describe the distribution of

¥5.

16.

i7.

POLYTRICHUM COMMUNE 83

this tissue in the seta, and explain whether or not
this is an added advantage.

After the sporophyte of Polytrichum begins to de-
velop, does it grow continuously until maturity, or
does a period of prolonged rest intervene? Is the
same true with the sporophyte of the fern?

As directed in J, 10, p. 72, diagram the life history
of the moss.

Outline the life history of the moss, as described in
Yee ao Ry pe

H. Comparisons:

we

Write the following names of organs of the gameto-
phyte of the moss in a column, and opposite them,
in another column, the names of the corresponding
organs of the fern; thallus, rhizoid, antheridiophore,
archegoniophore, antheridia, sperm, archegonium,
egg, paraphyses.

. Inasimilar manner compare the organs of the sporo-

phytes of the two plants, adding the names; sto-
mata, foot, calyptra, columella, apophysis, sporan-
gium.

. Ina third column make a list of organs of the moss

not found in the fern; in a fourth column, the organs
of a fern not found in the moss.

. Compare the degree of organization of the gameto-

phytes of the fern and the moss, as illustrated by
Polypodium and Polytrichum.

. In like manner compare the sporophytes of the two

classes of plants.

. State several reasons for regarding Polytrichum as

either more or less highly organized than Poly-
podium.

Marchantia polymorpha (A LivERworT)

A. Classification:
Division II. Bryophyta (moss-plants).

Class I. Hepatice (liverworts).
Order. Marchantiales (marchantia-forms).
Family. Marchantiacee.
Genus. Marchantia.
Species. polymorpha.

THE GAMETOPHYTE

B. Habitat:

I.

This plant grows very abundantly on the soil of
flower pots and benches in nearly all greenhouses.
In places it becomes a great annoyance to gardeners,
and is very difficult to get rid of. Out of doors it
grows in moist, shady places, frequently on rocky
ledges by streams.

C. Naked-eye Characters:

1
2.

3.

Examine first a non-“‘fruiting”’ specimen.

Is the plant-body a thallus? Describe its color,
outline, and manner of branching. What term is
applied to this manner of branching? Does the
plant possess dorso-vertral differentiation? If so,
how are the dorsal and ventral surfaces distin-
guished ?

Note the texture of the es to be ascertained by
carefully breaking off a piece of fresh thallus.

4. Describe the appearance of the dorsal surface. The

84

Io.

Il.

MARCHANTIA POLYMORPHA 85

small areas into which it is marked off are areole.
In the center of each areola find evidence of a
stoma. Is there a midrib?

. The cup-shaped structures on the dorsal surface

are called cupules. Do they occur on definite
portions of the thallus (7.e., margin, midrib, etc.),
or irregularly? Describe their color, shape, height,
diameter, margin. Are they sessile or stalked?

. The non-sexual (vegetative) reproductive bodies

within the cupules are brood-buds, or gemme
(sing., gemma). Describe the color, shape and
size of one (use hand lens). How are they attached
to the plant? Do all the cupules contain them?
Explain your observation on this point.

. Examine the ventral surface of the plant. De-

scribe its color and surface markings, and compare in
these respects with the dorsal surface.

. Note the root-like filaments or rhizoids. Describe

their shape, color, dimensions, and distribution
over the ventral surface.

. Find purple, leaf-like structures (scales) among the

rhizoids, and describe their form, position, and

distribution.

Make careful ———— showing:

(a) The plant-body, natural size..

(b) The surface markings of the dorsal surface,
enlarged ten times.

(c) A cupule, side view in. Loi ng txts enlarged
ten times.

_(d) An outline of a gemma 4 enlarged ten times.

Make a diagram of an imaginary cross-section of
the plant-body, passing through one or more cupules
(ten times natural size)... Label. all :parts of the
drawings.

86 |

MORPHOLOGY AND LIFE HISTORY

D. Microscopic Characters:
1. The rhizoids.

(a)

(6)

With the forceps carefully remove a few of the
rhizoids and mount them in clearing fluid.
Examine them first under low, then under high
power.

Do you find different kinds of rhizoids? If so,
how are they distinguished? Are there cross-
walls? Describe the contents of the rhizoidis
Do they branch? Explain the shape of their
tips, and the thickness of their cell-walls.

2. The gemme2.

(a)

(0)

(c)
(d)

(e)

Remove several gemme with a scalpel, being
careful not to cut or otherwise injure them,
and mount them in a drop of water. Examine
with low power.

Are the gemmz more than one cell thick? Is
their thickness uniform? Describe. |
Find on the margin the scar, where the gemma
was attached to its pedicle, or stalk.

Find two vegetative notches, 180° apart. How
do they differ from the scar? Find papilla-like
cells in these notches. Do they contain chloro-
phyll? Do they secrete mucilage? In the
apex of each of these notches is a vegetative
point from which a new thallus will develop.
Mucilage protects it.

Are there any surface outgrowths? Is there
dorso-ventral differentiation? Compare them
in this respect with the thallus to which they
give rise. So far as you can detect, would it
make any difference which side up the gemma
lay when it was sown?

3.

MARCHANTIA POLYMORPHA 87

(f) In the cells of a gemma do you find chloroplasts?
Nucleus? Oil drops?

(g) Note the larger cells with clear contents from
which the rhizoids will develop. Do they con-
tain chlorophyll?

(h) Make a drawing 50 mm. in diameter, showing
all the features observed under D, 2.

(i) Draw the outline of an imaginary cross-section
passing through the center of a gemma.

The thallus.

(a) Under high power study the surface cells and
stomata. How many guard-cells are there?
Compare the stomata of Marchantia with those
of a foliage-leaf of a higher plant, and of the
moss and fern.

(b) Study cross-sections of the plant mounted in
clearing fluid.

(c) The careful study of the structure of the foliage-
leaf, already made, makes it unnecessary
to give detailed directions for these observa-
tions. Frame your own questions, to be
answered by observing the mounted section.
Note especially whether the tissues are differ-
entiated, and, if so, compare with a foliage-leaf
in this respect.

(d) Look for sections passing through stomata,
and compare their structure with that of the
stomata of the leaf. What causes the surface
appearance of the margins that delimit the
areole?

(e) Describe the place and mode of origin of the
rhizoids; of the cupules.

(f) Is the thallus of the same thickness throughout?

(g) Describe the chloroplasts. In. some of the

88 MORPHOLOGY AND LIFE HISTORY

cells brown oil globules may be observed.
If these are found, describe their location,
and relative size. Do the cells that contam
oil globules also contain protoplasm? Infer
the source of the oil.

(4) Make drawings to illustrate all features observed
under D, 3.

E. Vegetative Propagaiion:

1. There are two ways in which Marchaniia can
propagate itself without the intervention of gametes.
In the first place, a portion of the thallus broken
off is capable of developing into a mature individual.
Somewhat, though not sharply, distinguished from

_ this method is reproduction by means of the
gemmz. State two differences between a gemma
and a fern or moss spore.

2. Incorporate the above facts into your notes at this
point, using your own language, and state to what
kind oi reproduction each of the above methods
belongs.

F. Sexual Reproduciion:

1. Study plants having the upright stalks which bear

the sexual reproductive ——

The aniheridial branch

N. bat eae Characters:
(a) The stalks having the mushroom-shaped tops
_ bear the antheridia, and are hence called the

antheridial branches, or antheridiophores. The
- expanded portion borne at the summit of the

stalk, is the antheridial receptacle.
_ (6) Study and describe the stalks of the antheridio-
phores. On what region of the thallus are these

(c)

(d)
(e)

(f)
(g)

MARCHANTIA POLYMORPHA 89

structures borne? On which surface do they
originate? State their average height in milli-
meters. Describe the grooves on the surface.
How many are there?

Describe the color of the stalk. Are stomata
present? Epidermal hairs or other outgrowths?
If so, describe.

Do you find any antheridiophores that branch?
Describe carefully the appearance of the upper
surface of the antheridial receptacle, noting
the occurrence and distribution of any struc-
tures or surface marks.

Is this surface perfectly plane? If not, describe.
Make drawings, twice natural size, showing
all points observed under F, 1, (a)-(f), including
a cross-sectional view of the stalk.

Microscopic Characters:

(7)

(7)

(fk)

Study and describe with drawings (5 cm.
in diameter), the structure of the stalk of
an antheridiophore as seen in cross-section.
Using prepared slides, study thin longitudinal
sections passing through a receptacle and
portion of the stalk. Is there a differentiation
into epidermis and other tissues? Describe
in detail. Note the intercellular air-spaces.
In what part of the structure do they occur?
Suggest any advantage these air-spaces may be
to the plant.

Observe the chambers opening at the surface
through necks, and containing the antheridia.

- How many antheridia in eachchamber? De-

‘scribe their shape, and mode of: attachment.
‘How many cells thick is the wall of the anther-

idium? Do the -wall-cells contain chlorophyll?

go

(2)

MORPHOLOGY AND LIFE HISTORY

Describe variations in the size of the antheridia,
and explain. Locate them according to size.

(m) Do you find papille (paraphyses) at the base

(n

A

(0)

of the antheridia? Ifso, of how many cells are
they composed? Describe their shape and
appearance.

Describe the appearance of the contents of an
antheridium. In the mature antheridium the
contents are mature antherozoids or sperms.
Younger antheridia contain sperm-mother-
cells. Describe their appearance accurately.
Illustrate by suitable drawings all the features
observed under F, 1, (z)-(n).

The archegonial branch

Naked-eye Characters:

(?)

(9)

(7)

The stalks having the umbrella-shaped tops
bear the female reproductive organs or arche-
gonia, and are called archegoniophores. The
expanded portion at the top of the stalk is the
archegonial receptacle.

Do the archegonial and antheridial branches
occur on the same plants? Measure the height

of the stalks of several mature archegoniophores,

and compare their average height with the aver-
age height of the stalk of the mature antheridio-
phore. Is the stalk of the archegoniophore
grooved?

Describe the markings of the upper surface of
the receptacle, and compare it with the dorsal
surface of the thallus. Are stomata present?
Record the number of rays on your specimen.
Compare several specimens on this point.

(s)

MARCHANTIA POLYMORPHA gI

Describe the under surface. Note the fringed
membranes, (perichetium).

Microscopic Characters:

(2)

(u)

(2)

Study and describe, with drawings (5 cm. in
diameter), the structure of the stalk of an
archegoniophore as seen in cross-section. Com-
pare this with the antheridiophore (F, (h), p.
89).

Using prepared slides, study longitudinal sec-
tions of the receptacle passing through one of
its arms. If fresh or preserved material is at
hand in sufficient quantity, the study may be
made from material ‘‘teased out” on the
slide.

Study the tissues of the receptacle. Is there an
epidermis? Stomata? Describe (a) the tis-
sues just beneath the surface layer of cells;
(b) those more deeply seated.

(w) Observe the flask-shaped archegonia hang-

(x)
(y)
(z)

ing from the lower surface of the receptacle.
Can you distinguish two regions—venter and
neck. Note the passage, or neck-canal, leading
from the venter through the neck, and opening
at the summit. How many cells thick is the
wall of the archegonium? Compare with the
archegonia of mosses and ferns.

Surrounding a mature archegonium observe the
section of a cup-like structure, the perigynium.
Within the venter of an archegonium just
matured observe a single-celled ovum, or egg.
Make drawings illustrating all features shown
under (u)—(y), and preserve the mounted
section for subsequent study.

Q2

MORPHOLOGY AND LIFE HISTORY

G. Physiology:

IEA

Is photosynthesis possible with the thallus? The
antheridiophore? The ‘archegoniophore? What

correlation’ do you find between structure and

function in this respect in the archegoniophore?

. Explain the nutrition of the non-chlorophyll-bear-

ing cells of the gmme. What is their nutritive
relation to the gemma as a whole?

. Is the gametophyte capable of an independent ex-

- istence? Thoughtfully consider and then describe

the correlation between structure and function in
this respect. :

. In mature specimens sea apa es dicaaid may

often be found exuding on the dorsal surface of the
antheridiophores. This liquid contains active an-

_therizoids, or sperms. Mount some of it in water,

- and, under high power, observe the motion, organs of

motion, and other structural features of these sperms.

. When longitudinal sections of mature archegonia

are mounted in water containing active sperms the
behavior of the latter toward the former may be

readily observed. If your material is suitable,
_ make. these studies.
. How only can the sperms oe the — What

external conditions would be favorable.for this?

. Of what advantage is it to the sporophyte to have

the egg retained in the venter of the archegonium?
Would this be of as great advantage in any Aine o:
plant, as ina land plant? Why?

. Is the small size of the sperms of any = advan-
‘tage to the plant? Explain.
. Explain any advantage in the sottit hath of the

mature archegoniophore over that of the antheridio-
phore.

ee

- MARCHANTIA POLYMORPHA 93

1o. Enumerate several facts that insure a wide distribu-
tion of Marchantia.

THE SPOROPHYTE

A. Origin of the Sporophyte:

1. What is the process of the fusion of the egg and
sperm called? What is the body that results
from this fusion called? ‘This body, by successive
cell-division, develops into the sporogonium or
sporophyte.

B. Naked-eye Characters:

1. In a mature specimen observe the small bell-
shaped organs (sporangia) pendant on a stalk
between the perichetia. The sporangia and stalk
together form the sporogonium, or sporophyte stage
of Marchantia. In fresh mature specimens an
orange-colored mass containing spores is easily seen
at the end of the sporophyte. Are the sporogonia
borne on a line with the rays or between the rays?

2. Make drawings, four times natural size, showing the
archegoniophore as seen from (a) the top; (0) the
side; (c) the underside.

3. After making the drawings, as directed in B, 2,
carefully dissect out one mature sporogonium and
place it in a watch-glass to examine. Make a
drawing 50 mm. long, showing all features observed,
labeling the foot, stalk, and sporangium. Write a
brief but clear description of the sporogonium.

C. Microscopic Characters:

1. If prepared slides are available of sections passing
through the archegonia (F (w) above), find various
stages in the development of the sporophyte within
the archegonium. In nearly mature specimens

Q4 MORPHOLOGY AND LIFE HISTORY

observe the attachment of the sporophyte to the
receptacle by means of thefoot. This study may be
made to advantage with fresh or preserved material
teased out on the slide. In such preparations there
will be observed, surrounding the sporogonium, the
membrane formed by the growth of the perigynium.

2. In the mount already made (or in a fresh mount of
the orange-colored mass referred to in (B, 1, p. 93),
observe the spore-mother-cells (Sporocytes) or, in
older specimens, the spores (in strands or separate,
depending on the stage of development), and the
elongate elaters. What is the size of the spores, and
the number of cells of which they are composed?
Describe their shape, and any surface marks ob-
served. Describe any marks on the elaters. Of
how many cells is an elater composed? Mount, dry,
some of the mass that contains elaters, and observe,
under the low power, their behavior as water is
added. .

3. Are the antheridiophores and archegoniophores
sexual organs? Why? What are the sexual organs
of Marchantia?

4. Name and classify (sexual or asexual) four different
kinds of reproductive bodies produced by this plant.
Consider carefully whether the spores, produced
by the sporophyte, are sexual or asexual reproduc-
tive bodies.

D. Physiology:

1. Can photosynthesis take place in the spore phiyees
Explain your answer.

2. From what source, by what organ or organs, and
by what physical process does the sporophyte ob-
tain its water and dissolved food? Compare it
with the gametophyte in this respect.

MARCHANTIA POLYMORPHA 95

E. Comparison of Gametophyte and Sporophyite:

I.

Compare the degree of development or organiza-
tion of sporophyte and gametophyte.

2. Copy the following table into your laboratory note-
book and mark x after the word gametophyte or
sporophyte in the proper column.

TABLE II
Pia aaa ris | re eee a ee
ales /a2/e|e |$8 |3
Pasha 1H pase ad 8 2/82
a |Z Qi aes Saluece a2 on °.8
Generation ‘3 a o es 3 | a 5 weg a3
° a | ORS a o Oed | Od
Hi/ele)/eeis| gg], |sselse
@i'S|s|8a)/8)/3/8 | Shales
e|Gla|o*|alala je-*le*
Gametophy te... ... 6.25 oe oe
Sporophytes. cio oacie scien

. State reasons why you consider Marchantia higher

or lower than (a) the moss; (b) the fern.

. Diagram the life cycle of Marchantia, as directed

for the fern (J, 11, p. 72).

. Indicate the life history of Marchaniia for three gen-

erations, as directed in J, 10, p. 72.

. Does the gametophyte ever produce another game-

tophyte directly? Does the sporophyte ever pro-
duce another sporophyte directly? If so, explain
how. What phase intervenes between two gameto-
phytes in the alternation of generations? Between
two sporophytes? Is this always the case so far
as your own studies show? Explain what is meant
by the expression, “‘alternation of generations.”’

Fucus vesiculosus (BLADDER WRACK)

A. Classification:
Division I. Thallophyta.

Subdivision I. Alge.

Class III. Phzophycez (brown alge).
Order. Fucales.
Family. Fucacee.
Genus. Fucus.
Species. vesiculosus.

B. Habiiat:

I.

Ascertain the habitat of this plant ae your read-
ing and class discussions, and record it in your
laboratory notes at this place.

C. Naked-eye Characters:

I.

These characters may be best studied by floating a
fresh specimen in a dish of sea-water. Material
preserved in formalin should be rinsed under the
tap, and then floated in fresh water.

. Describe the color, shape, and size of the thallus.

Does it form lateral branches or approximately
equal terminal branches (dichotomy, forking).

. Do you find any holdfasts, or organs of fixation?

If so, describe them. State reasons why you think
they are true roots or ‘not.

. Is there a midrib? A stalk, or stipe? Do you

consider that the plant is differentiated into root,
stem, and leaf? Give reasons.

. Describe the distribution of bladders. Why is this

species called “‘veszculosus’’?
96

ro.

FUCUS VESICULOSUS 97

. Observe the swollen tips, receptacles. Do the tips

of all the branches bear receptacles? How may
they be distinguished from the bladders?

. Carefully note the dot-like projections on the re-

ceptacles. Find the circular openings in these pro-
jections, the ostioles.

. Do you find ostioles elsewhere than on the recep-

tacles? If so, describe their distribution over the
surface of the thallus. Where are they not found?

. Observe carefully the emarginate tips of the

branches that do not bear receptacles. Do you
find a groove in these tips? If so, is it in the plane
of the thallus, or not?
Make careful drawings, natural size, showing all
points noted under C.

D. Microscopic Characters:

I.

5e

7

Mount in water thin cross-sections taken through
the thin expanded portion of the thallus, and study
under the low power.

Note the differentiation of the tissue into central
tissue or medulla, and a cortical tissue. How are
the two distinguished?

. Observe that the outer layer of cells of the cortical

tissue is further differentiated into an epidermoidal
tissue. Describe it. This outer layer is not a true
epidermis, like the outer layer of cells of the leaf.
In the younger portions of the thallus its cells, by
division, give rise to the cells which form the under-
lying tissues. None of the alge possess a true
epidermis. .

. Is starch present in the cortical tissue? Chlo-

rophyll? Note the layer of cuticle on the outer
cell-walls of the epidermoidal layer.
Note that the cells in the medulla tend to form a

98

MORPHOLOGY AND LIFE HISTORY

thread-like network. Does starch occur in this
tissue? Some of the cells unite, end to end, form-
ing tubes to conduct liquids.

. Between the cells of both cortex and medulla is a

mucilaginous layer, formed by the swelling and
chemical transformation of the middle lamella,
or layer that separates adjacent cell-walls.

. Make a drawing showing the differentiation of

tissues from the surface to the center of the thallus.

. Sterile Conceptacles: Secure sections passing through

one or more of the ostioles that do not occur on the
receptacles. ‘These ostioles will be found to open
into spherical or pear-shaped cavities (conceptacles)
imbedded in the cortical tissue. In viewing a cut
end of the thallus with the naked eye, these cavities
appear as minute dots underneath the epidermoidal
layer.

. Observe in these conceptacles, under the low power,

numerous long hairs (paraphyses). Of how many
cells is each composed? Do they extend through
the ostioles to the surface? With what are they
connected?

E. Physiology:

I.

Of what advantage to an aquatic lait may the
air-containing bladders be?

. Does the plant grow attached to a substratum?

If so, how?

. How do you think the bight takes in its food ele-

ments?

. Ascertain if the plant has chlose pia Ts phate

synthesis possible?

. Would it be an advantage to this plant to nae a

system for conducting liquid nutrients from one
place to another? Is such a system present?

> FUCUS VESICULOSUS 99

In attempting to answer this last question recall
the habitat of Fucus.
F. Vegetative Propagation:

1. Vegetative propagation is accomplished by the
breaking off of branches which may float away
and become established as new individuals.

2. Frequently, by a process of regeneration, dwarf
branches are formed where portions of the thallus
have been torn away. Do you find instances of
this in the material at hand?

G. Sexual Reproduction:

1. The sexual reproductive organs of Fucus are borne
in fertile conceptacles, imbedded in the cortical
tissue of the receptacles. In Fucus vesiculosus the
conceptacles containing the female organs are on
different plants, z.e., the plants are dicecious. In
other species they are both on the same plant, while
in still other species (e.g., F. edentatus) both kinds
of organs are in the same conceptacle. In the two
latter cases the plants are moncecious.

2. The Male Conceptacles:

(a) Examine a longitudinal section of a male
conceptacle, passing through the ostiole. Note
the outline of the cavity. Describe its wall.

(b) Observe the filaments (paraphyses) within the
cavity, and describe the length, diameter,
shape, and structure of one of them. Do any
of these filaments project through the ostiole?
Explain the feeling as a receptacle is taken be-
tween the thumb and fingers.

(c) Are the filaments that pass through the ostiole
similar to those that do not? On the latter
observe the small ellipsoidal organs antheridia.
Where and how are they attached? How

100 MORPHOLOGY AND LIFE HISTORY

many on each hair? Observe their contents,
the sperms (antherozoids, spermatozoids).
(d) Make a drawing at least 50 mm. in longest
diameter, illustrating all the above structures.
3. The Female Conceptacles:

(a)

(0)

(c)

(d)
(e)

Study a longitudinal section passing through —
a female conceptacle, as directed above
(G, 2). Compare them in all points with
the male conceptacles.
Observe the egg-bearing organs, odgonia.
Describe their shape, size, color, place and
mode of attachment, and number, and
compare them in these respects with the
antheridia.
Describe the structure of the wall of the
odgonium, noting especially whether it is
composed of cells.
Study the contents (odspheres, or eggs) of
the odgonium. How many are there?
Make drawings showing all these points,
as directed in G, 2(d).

4. The Fertilization of the Egg:

(a)

(0)

Observe fresh plants that have been hang- -
ing in the air for about six hours, and see
if you can observe an orange-colored fluid
exuding from the ostioles of the male con-
ceptacles. If so, mount some of this fluid
in sea-water and examine it under the high
power. | ?
Note the antheridia floating about, and the
escaped sperms. Do the latter possess the |
power of locomotion? If so, how do they
move? Describe their shape, relative size,
and color.

(c)
(d)

(f)

(g)

(7)

FUCUS VESICULOSUS IOI

Make a drawing of three or four sperms,
with the body about 1o mm. long.

In a similar way, find the fluid exuding
from the female conceptacles. What is its
color? Mount a drop of it in sea-water
and examine with the high power.

Do you find any odgonia? Any free eggs?
If so, how are the latter freed from the
odgonia? Do they possess the power of
locomotion? Compare their size with that
of a sperm.

Make a drawing (50 mm. in diameter) of
an egg. By the side of the egg draw three
sperms to the same scale, showing the
relative size of egg and sperm.

Prepare a mount containing both eggs and
sperms, and endeavor, if possible, to fol-
low the action of the sperms toward the
egg, and the fusion of the two cells. With
what act is fertilization completed?

Do you consider Fucus a more highly or a
more lowly organized plant than Mar-
chantia? Give reasons for your answer.

Vaucheria sessilis (GREEN FELT)

A. Classification:
Division I. Thallophyta.
Subdivision I. Alge.
Class II. Chlorophycee.
Order. Siphonales (Siphon-algz).
Family. Vaucheriacee.
Genus. Vaucheria. (The only genus in
the family.)
Species. sessilis.

B. Habitat:

From your reading, class work, and material at hand,

ascertain and record at this point in your notes the

kind of localities where this plant occurs.
C. Naked-eye Characters:

Describe the color and ‘‘feel’’ of this plant, and the

general form of the plant-body. What is the signifi-

cance of the common name “‘green felt’’?
D. Microscopic Characters:

1. Mount a portion of the material in water.

2. Isthe plant branched? Ifso,isthe branching lateral
or dichotomous (i.e., forked) ?

3. Do you find cross-walls? Does the plant seem to
be composed of cells? What is the outline of its
cross-section?

4. Can you detect any signs of division into root and
shoot? Do all portions of the filaments appear
equally fresh and vigorous? Describe.

5. Do you find, on the end of any of the filaments,

I02

o VAUCHERIA SESSILIS 103

holdfasts? If so, describe them, and state their
use to the plant.

6. Can you detect one or more nuclei? Any vacuole
or vacuoles? Any individual chromatophores or
chloroplasts? If so, what is their position and
shape?

7. Describe the arrangement of the protoplasm within
the filament.

E. Physiology:

1. Explain whether, or not, photosynthesis and respira-
tion are possible with this plant.

2. Do you find any chromatophores dividing?

3. Do you find oil globules within the plant? Test
dechlorophyllized plants with iodine for starch.

4. How are mineral matter and carbon taken into this
plant? Explain the need or lack of need of special
structures for conducting food and food elements
from one part of the plant to another. Are such
structures present?

5. Why is the plant not crushed by the weight of the
water (when it grows in water), or by the cover-
glass?

6. Can you detect any movement of the protoplasm?
Observe carefully on this point.

7. Make careful drawings showing all features to which
attention has been directed under D, and E£, 2.

F, Asexual Reproduction:

1. Carefully examine the tips of numerous filaments
and see if you find any of them slightly enlarged,
and cut off from the rest of the filament by a cross-
wall. Such a differentiated portion of the thallus
of Vaucheria is a Sporangium; its contents a spore.

2. If you are fortunate enough to have material at a
suitable stage of development, you may, by care-

104 MORPHOLOGY AND LIFE HISTORY

ful observation, observe a spore escaping from the
opening in the tip of the sporangium. If so, give
careful attention to the mode of locomotion of the
spore, and describe how its locomotion is accom-
plished. Since it has motion (as animals do) it is
called a zodspore. The zodspore soon comes to
rest.

3. If the material contains germinating zodspores,
carefully describe them.

4. Make drawings illustrating all you have observed
under F.

G. Sexual Reproduction:

1. In “fruiting”? material, observe the lateral organs
that bear the gametes. ‘These are the reproductive
organs. As is seen, they are of two kinds.

2. The larger, oval-shaped organ is called theoégonium.
Is the odgonium cut off from the parent filament
by a wall? On one side observe the rostrum, or
beak, through which is an opening or pore. In
material at a suitable stage may be observed a
portion of the contents of the odgonium being
voided or discarded. The protoplasm that re-
mains in the o6gonium now becomes organized into
the larger gamete or egg (odsphere). Is its wall
composed of cells, or is it a unicellular organ?

3. By the side of the o6gonium! find a slender branch,
usually recurved at the end. Is this branch cut off
from the parent filament by a wall? Is the tip
cut off from the rest of the branch? This tip bears
small gametes, that swim about by means of two lash-
like cilia. They are the spermatozoids or sperms.

1]f the species is V. geminata, instead of V. sessilis, the reproductive

organs will be found on the same lateral branch. The above directions
will not apply in detail to any species except V. sessilis.

VAUCHERIA SESSILIS 105

What is the organ that bears the sperms called?
The base of the antheridial branch is the pedicel,
or stalk. |

. Can you detect any sperms escaping? If so,
observe and describe them carefully. See if you
can find any empty antheridia.

. Make careful drawings showing all points observed
under G.

. Is there a division of physiological labor in Vauch-
eria? Explain in detail.

. Show, by a diagram, the life cycle of Vaucheria.

. State the difference between conjugation and
fertilization.

. Draw an ideal diagram of a complete plant, showing
all structures, and stages of their development.

Spirogyra sp. (POND scuM, GREEN SILK)!

A. Classification:
Division I. Thallophyta.
Subdivision I. Alge.
Class II. Chlorophycee.
Order. Conjugales.
Family. Zygnemacee.
Genus. Spirogyra.
Species. sp. (z.e., not determined).
B. Habitat:

Ascertain from your own observations and from the

text, and record at this point in your notes, the habitat

of Spirogyra.
C. Physiology:

1. Explain, clearly but concisely, how the bodily form
of this plant is maintained. Account for any
variations in the shape of the cells.

2. Do you find any roots or other organs for anchoring
the plant to the substratum? Do you think the
plant is suitably organized for growing in running
water? Explain. State a reason why roots are
not necessary for this plant.

3. Explain the presence or absence of stomata. Do
you find a cuticle? Is photosynthesis possible with
Spirogyra? Respiration? Explain.

1 The morphological characters of this plant have already been studied
(pp. 11-15). They should now be carefully reviewed, preparatory to the
consideration of the physiology and reproduction of the plant.

2 True cuticle does not occur, but a modification of the outer portion
of the cell-wall, called the sheath, and which gives the plant its slippery
‘“‘feel,”’ is similar to cuticle, though not identical with it. This sheath
is dificult to observe directly, though it may sometimes be identified on

the outside of the filament at the places where the cross-walls occur.
106

SPIROGYRA SP. 107

»:

4. Can you detect any difference between the cells
physiologically? From your own observations do
you think there is any correlation between the struc-
ture of cells and their function? Explain clearly.

5. Is there any. evidence in Spirogyra of a correlation
between structure and envronment? Explain.

D. Asexual Reproduction in Spirogyra:

1. From what you have already learned of Spirogyra,
state the possibilities of vegetative propagation in
this plant.

E. Sexual Reproduction in Spirogyra:

1. Use fresh material, if possible; otherwise preserved
specimens, or prepared slides.

2. Observe the various stages in the fusion of two cells
(gametes). Do the fusing gametes belong to the
same, or to different filaments? Observe the
conjugation-tubes connecting adjacent filaments.
What is their function? Their relative diameter?
Try to find tubes in various stages of formation.
Are their distal ends open before they come into
contact? Howisthe opening made? Do the tubes
grow together or merely touch each other?

3. Does conjugation seem to be a function of all the
cells of the filament, or of certain cells only?

4. Do the gametes pass from either filament to the
other, or do the cells of a given filament all behave
alike in this respect? In this connection see
whether all the zygospores occur in one filament,
or not.

1 The form of conjugation described in the outline above, is termed
“‘scalariform” (ladder-like). Another type, known as ‘“‘lateral’”’ con-
jugation may frequently be met with, in which the gametes are formed by
adjacent cells of the same filament. In less frequent cases the protoplast

of a single cell organizes itself into a reproductive body (aplanospore)
without conjugation. This process is a type of parthenogenesis.

108

Io.

MORPHOLOGY AND LIFE HISTORY

. Does the cell-wall of the receiving cell serve as the

cell-wall of the zygospore, or does the latter form a
new wall? .

. In a sentence define the term supplying cell, using

the words gamete and conjugation.

. If fresh material is studied, describe any observed

differences in color between the mature zygospore
and the non-conjugating cells; any structural dif-
ferences between the cells of a supplying filament
and those of a receiving filament. Do you observe
any evidence of sexual differentiation in the
filaments?

. Explain whether Spirogyra represents a condition

of isogamy or of heterogamy.

. Make drawings of all the following features shown

by your material, with each cell about 50 mm. long.

(a) Two adjacent cells in which the conjugation-
tubes are just beginning to develop.

(6) Two adjacent cells in which the conjugation-

tubes have just met.

(c) Two adjacent cells in which the active (supply-
ing) gamete is passing through the conjugation-
tube.

(d) Two adjacent cells in which the passage is
complete.

(e) Two adjacent cells after conjugation is com-
plete. Show carefully and accurately the details
of structure of the zygospore.

Study stages in the germination of the zygospore

as shown on the chart. State, in order, the proc-

esses that take place in the formation of the
new plant (mature zygote) from the zygospore.

Compare the plant of the new generation with

its parents.

It.

r2.

ne

14.

SPIROGYRA SP. 109

Is there a physiological division of labor in this
plant? Explain in detail.
Draw a diagram showing the ancestors of a plant
of Spzrogyra for three generations.
To complete your notes on Spirogyra, write, at
home, and before the next laboratory period, as
clear and well-worded an account as you can of
the life history of the plant.
Arrange ferns, alge, mosses, liverworts, in a
vertical column in the order of the complexity of
their organization, placing the more highly organ-
ized near the top of the column. Write a clear
statement of the reasons for your arrangement
of the above classes.

Pleurococcus vulgaris (GREEN SLIME)

. Classification:
Division I. Thallophyta.

. Habitat:
i:

Subdivision I. Alge.

Class II. Chlorophycez (green alge).
Order. Ulotrichales.
Family. Chetophoracee.
Genus. Pleurococcus.
Species. vulgaris Menegh.

From the material given you, infer where this plant
grows. Leave a blank space in your note-book,
and before the next laboratory period, record further
observations on this point, made out of doors,
noting especially the following points. Does the
plant appear to be more abundant on one side of
the object on which it grows than on another?
Describe and explain. In general, what external
conditions seem to favor its growth? Do you ever
find it intimately associated with other plants?
Describe.

. Naked-eye Characters:

gE.

Describe the color of a colony of Pleurococcus.
Can you distinguish the shape or other characters
of an individual plant?

. Microscopic Characters:

rs

With the needle carefully scrape off a bit of the
plant from a piece of moist bark or wood, and

mount it in water.
IIo

. PLEUROCOCCUS VULGARIS III

. Is the body of this plant differentiated into root,

stem, and leaves? Is it composed of cells? If so,
of how many? Make a thorough study of this
point before you answer and thoroughly cons der
how many cells you think are necessary in order to
make one plant. State your opinion, with reasons.
Compare the arrangement of the cells with those in
Spirogyra.

. Describe the color and shape of manda cells.

Descr be and account for any variations observed
in the shape of the cells.

. Carefully describe all the cell-organs you can

identify in this specimen. Name all the cell-organs
you cannot find. How does the chlorophyll occur
in the cell of Pleurococcus? If you find chloroplasts
state how many, their location, and relative size.

. Make careful drawings showing all features so far

as observed, with none of the cells less than 15 mm.
in longest diameter.

E. Physiology:

y:

How does Pleurococcu= remain fixed to the sub-
stratum on which it grows? Are there special
organs for this purpose?

. Are there special organs for the taking in of nourish-
-ment from the substratum? How can the plant

accomplish this process?

. Is photosynthesis possible with Pleurococcus? Give

reasons for your answer. Are stomata present?
Why? Describe how CQ, can be taken into the
cell.

. Are there any special organs of respiration? How

can this process take place?

. Do you think Pleurococcus is sensitive to stimuli

from without? Give reasons for your answer.

II2

MORPHOLOGY AND LIFE HISTORY

F. Reproduction:

E:

Do you find any cells that appear to be dividing?
If so, carefully describe their appearance. What.
are the indications that a cell is dividing?

. Do the cells tend to remain united after cell divi-

sion? Is this true of all of them? Describe.

. Make three diagrams, showing (a) the life cycle of a

Pleurococcus plant; (b) the descendants of one plant
for six generations; (c) the ancestors of one plant for
six generations.

. Is there a division of physiological labor in this

plant, or are all life functions-performed by every
cell?

Phycomyces nitens (or Rhizopus nigricans)

. Classification:
Division I. Thallophyta.

Subdivision B. Fungi.

Class III. Phycomycetes (alga-fungi).
Order. Mucorales (the molds).
Family. Mucoracee.
Genus. Phycomyces.
Species. itens.

. Habitat:

I.

Upon what substratum is the Phycomyces growing?
What atmospheric condition seems to be most
favorable to its growth?

. Naked-eye Characters:

I.

Describe in detail the appearance of this plant as
it grows. What is its color? Describe any varia-
tions in color.

. Note the aerial filaments or hyphz. Do they

grow erect or horizontally? How many milli-
meters long are they?

. On the ends of some of them observe the enlarged

structure, the sporangium. Describe its shape.
From its name, sporangium, what do you infer that
it contains. Hyphe that bear sporangia are
sporangiophores. What does the term literally
mean?

. Compare the height of the sporangiophores bearing

young (yellowish) sporangia, with that of those
bearing more mature (dark-colored) sporangia.
Explain the significance and advantage of this.

. Using the hand lens, note the vegetative hyphz

113

II4 MORPHOLOGY AND LIFE HISTORY

that grow into the substratum (substance on which
the fungus grows), and over its surface. These
filaments constitute the mycelium. Compare their
diameter with that of the sporangiophores. Do
they appear to branch? ;

6. Make a drawing, illustrating all points observed.
Make a diagram showing, in order, the relative
heights of six sporangia of various ages. Indicate
the scale used.

D. Vegetative Propagation:

1. If Rhizopus nigricans is used, study, with the naked
eye, the formation of stolons by this plant, and
describe in full, with drawings, this process of
propagation. This plant (Rhizopus nigricans) was
at one time called Mucor stolonifer. Explain the
appropriateness of this latter specificname. The
generic name, Rhizopus (root-like foot), refers to
the branching mycelial hyphe, which form at the
tips of the stolons. Explain the significance of the
specific name nigricans (black).

2. How does Phycomyces nitens increase vegetatively ?

3. Study and draw stages in the germination of spores
that have been in sugar solution for twenty-four
hours. (Use spores of Phycomyces or Sporodinia,
as spores of Rhizopus do not germinate readily in
sugar solution.)

E. Microscopic Characters of the Mycelium:

1. Mount in water a small portion of the substratum
with the mold attached, and, if necessary, very
carefully tease it out with the needles.

2. Study the mycelium. Is it branched? Are the
mycelial hyphe of the same diameter throughout?
Are cross-walls present? If so, describe their
frequency.

ae

ah PHYCOMYCES NITENS II5

3. Make a drawing to illustrate the above points.
F, Physiology:

1. Describe the color of the sporangiophore and
sporangium as seen under the microscope, and state
whether this color is in the cell-wall or in the cell-
contents.

2. If you detect any motion of the protoplasm (best
seen in young sporangiophores) describe it accu-
rately. Is it a true circulation (7.e., in various
directions in a closed circuit), a rotation (7.e., up
one side of the filament and down the other),
or a Streaming (7.e., all currents apparently toward
one and the same end of the filament). Suggest
any advantage this motion would be in the nourish-
ing of the plant; in the formation of sporangia.

3. Make a drawing of a portion of the hypha, at least
I5 mm. wide, showing the appearance of the con-
tents, and. with arrows, the direction of motion.

4. What foods does this fungus need? From where
must they be obtained? Are they soluble? Can
Phycomyces take in solid food? What process is
necessary in our own bodies before we can utilize
solid food? Must Phycomyces perform a like
function? Is there a special organ for such a
function? Must the process go on inside or out-
side of the body of the plant? Why?

5. Is photosynthesis possible with Phycomyces? Why?
How must it get its carbohydrates?

6. Does Phycomyces respire? Give a reason for your
answer.

7. What is the most obvious and important difference
between the cells of Phycomyces and of Spirogyra?

G. Asexual Reproduction:
1. Study asporangiophore. Is it of the same diameter

116

.
MORPHOLOGY AND LIFE HISTORY

throughout? Are cross-walls anywhere present?
If so, describe their location.

. Is the sporangium borne on the tip of the sporangio-

phore, or at one side? Are its contents separated
from those of the sporangiophore? If so, how?
Compare, on this point, young and old sporangia.
Is there more-than one sporangium on a sporangio-
phore? Within the wall of the sporangium observe
the central columella, surrounded by the spores.
Describe the shape of the columella. Are the
spores numerous or few within one sporangium?
Look for cases where the wall of the sporangium,
has ruptured, and the spores are mostly scattered,
leaving the columella naked.

. Illustrate by drawings all features observed under

G,1and2. Make the sporangium at least 20 mm.
in diameter.

. Describe the shape, relative size, color, and surface

markings (if any) of the spores.

H. Sexual Reproduction:

NotEe.—For this study Sporodinia may be substituted,

as it more readily yields suitable material.

. Find conjugating branches. Describe their shape.
. Find mature conjugating branches with the end

contents cut off to form gametes. The remainder
of the branch is now called a suspensor.

. Find, on still more mature material, the gametes

fused. What is the resulting structure called?.
Describe its appearance. If the material is suitable,
describe the germination of this structure.

. Illustrate with a drawing all features observed

under H. Make the suspensors at least 25 mm.
long, and other structures in proportion.

Saprolegnia (WATER MOLD)

. Classification:
Division I. Thallophyta.

Subdivision B. Fungi.

Class III. Phycomycetes.
Order. Saprolegniales.
Family. Saprolegniacee.
Genus. Saprolegnia.
Species. sp. (i.e., not given).

. Habitat:

I.

The spores of this fungus are widely distributed,
and develop readily under suitable conditions.
Such conditions are realized when a dead fly is
placed in a dish of tap-water. The fungus will be
sufficiently developed for study within five to seven
days. .

. Naked-eye Characters:

I.

Carefully observe the aerial hyphe as they grow,
forming a halo about the body of the fly. What is
the diameter of the halo? Its shape? Does its
shape seem to be influenced by the shape of the fly’s -
body? - Do the filaments grow vertically upward
and downward or only horizontally? What is the
color of the halo?

2. Estimate the average length of the hyphe.

. Can you detect any evidences of the formation of

sporangia at the tips of some of the hyphe, and of
sexual reproductive organs near the body of the fly?
Use a hand lens if necessary.

117

118 MORPHOLOGY AND LIFE HISTORY

4. Make a drawing, about 25 mm. im longest diameter,
showing the appearance of this fungus as it grows on
the body of the fiy-

D. Micrascepic Characters:

1. With the needle or scalpel carefully remove a few
filaments and mount them m water. Examme
with the low power.

2. Make careful comparisons of the tips of hyph=
enlarged to form sporangia with those not thus
modified. Describe the appearance of the contents
in each. }

3- Do you find any cross-walls m the filaments?

4. Do you find vacuoles? Plastids? Nuclei?

5- Make a drawing showing the appearance of the tip
of a vegetative filament (10 mm. nm pee ae

E. Nutrition and Growth:

t. See if you can find hyphz bearmg comps ibeabme
If so, do you find the hypha contmumg its growth
in length withm the empty sporangium? Illus-
trate this pomt by a drawing.

2. Where-do the vegetative hyph= (mycelium) grow?
Describe the nature of the surface of the fly’s
body. How can the delicate mycelia penetrate to
the mterior of the fly?

3- Upon what does this fungus feed? State im detail
the necessary steps in the process of getting this food
into the interior of the myceltum. In. this connec-
tion make comparisons with Phycomyces (see F, 4,
under Phycomyces, p. 115)-

4. Is there any correlation here between the absence of
chlorophyll and the habitat of the plant? IE so,
explam and compare with Pkycomyces, and with
Spirogyra.

= ee

»:

SAPROLEGNIA 119

F, Asexual Reproduction:

I.

Carefully study again the terminal sporangia.
How many times longer than broad are they?
Compare the thickness of the sporangium walls
with those of the remainder of the hyphe. Can
you detect any variations in the thickness of the
sporangium walls? If so, describe and explain.
Describe and account for the shape of the free tip
of the sporangium.

. Describe the shape of the zodspores, or Swarm-

spores; their size; number in one sporangium;
color. Are they all alike in these characters?

. Endeavor to find swarm-spores escaping from a

sporangium. Do they merely float away, or have
they. power of locomotion? Look for organs of
locomotion? If you find them, describe their
number, length, action, and general appearance.
Do they precede or follow the zoéspore as it moves
through the water?

. Do the zodspores ever move up or down through

the water so as to be out of focus? If so, consider
thoughtfully the thickness of the film of water
in which they are, and try to form some conception
of the size of a body that moves vertically beyond
the range of visionina film ofsuchadepth. Briefly
discuss this point.

. Do you see any evidence that any two of these

swarm-spores are in the process of fusion? Do
their movements appear to be directed, or not?

. Make suitable drawings to illustrate all points

observed under F.

G. Sexual Reproduction:

Tt.

Under suitable conditions female reproductive
organs, Odgonia, develop on certain hyphe near the

120 MORPHOLOGY AND LIFE HISTORY

body of the fly, and each odgonium develops a
number of eggs. If odgonia are found, describe
them carefully as directed above (F,1 ) for sporangia,
making suitable drawings. Do they always occur
at the end of the hypha that bears them?

2. The male reproductive organs are antheridial fila-
ments, growing either below the odgonia or on >
adjacent hyphz.! They are of smaller diameter
then the hyphz. If you find these organs, care-
fully describe their appearance, contents, size, and
relation to the odgonia. Illustrate all points =

served with suitable drawings.
H. General Questions:

t. Do you find a physiological division of labor in
Saprolegnia? If so, describe in detail.

2. State why you consider this plant higher or lower in
in the scale of life than Phycomyces or Fucus.

3. Describe all methods of dissemination of Saprolegnia
that you can think of. .

1 The development of the egg-cell without fertilization (¢.e.. by par-
thenogenesis) is more usual than fertilization in Saprolegnia, so that fer-
tilization, or even antheridial flaments, may be wanting.

Albugo candida! (BLISTER BLIGHT)

A. Classification:
Division I. Thallophyta.
Subdivision II. Fungi.
Class V. Phycomycetes.
Order. Peronosporales.
Family. Peronosporacee.
Genus. Albugo.
Species. candida.
B. Habitat:
This fungus is parasitic on plants belonging to the
mustard family (Crucifere). It causes the“ blister-
blight,” or “white rust,” on the leaves and stems
of the ayetheed? S purse ee bursa-pastoris)
and often on the radish.
C. Naked-eye Characters:

1. Describe. the appearance (color, shape, size, etc.)
of the blisters formed by this parasite on the host-
plant. What organs of the host are affected?

2. Make drawings, natural size, showing all the
features observed.

D. Microscopic Characters:

1. Study cross-sections of the host-plant taken through
one of the blisters.

2. What causes the blisters? In what tissue or tissues
of the host does the mycelium grow?

E. Nutrition and Growth:

1. In what form must carbon be supplied to this plant?
Why?

2. In thin sections look for absorbing organs (haus-
toria), branching from the mycelium and penetrating

1 Cystopus candidus (Pers.) Lev.
121

I22

MORPHOLOGY AND LIFE HISTORY

through the cell-walls into the cells.1 Describe
their relative length, shape and general appearance.
How far do they project into the cells? What do
you infer is the function of these organs? Suggest
away in which they might be able to pierce
the cell-wall. What other function must they per-
form besides the one you have already mentioned?

. Where and how does this plant digest its food?

What foods does it need? What is their source?

. Is there any correlation between the absence of

chlorophyll and the habitat of this plant? Explain,
and compare with Phycomyces and Marchaniia.

. Make a drawing showing three cells of the host

with the adjacent mycelium and the penetrating
haustoria.

=

F. Asexual Reproduction:

I.

3.

4.

5.

Observe the chains of spores (conidia, or conidio-
spores). On what are they borne? Describe their
shape, color, size. Are they all of the same size?
Which is the youngest conidium in a chain? Why
do youthinkso? Ofhow many cellsiseach conidium
composed? Are they attached to each other? If
so, how?

. Observe the conidia-bearing hyphz (conidiophores).-

Describe their shape, and the appearance of their
contents. Do they have cross-walls? Observe
this last point carefully, and describe.

Describe in detail, from your own observations,
the method of formation of the conidia.

Make one drawing showing all points observed,
including the tissues of both host and parasite.
Make a second drawing of two conidiophores,

i The haustoria are difficult to identify, especially with poor sections,
and too much time should not be spent in trying to detect them. :

. ALBUGO CANDIDA 123

showing the attached chains of conidia and the mode
of formation of the latter. In this drawing make
the conidia at least 5 mm. in diameter.

6. Include in your notes at this point a brief descrip-
tion of the germination of the conidia. (The infor-
mation should, if possible, be obtained from
material supplied by the instructor, otherwise from
lecture or reading.)

G. Sexual Reproduction:

1. The sexual reproduction of Albugo generally occurs
in other parts of the host-plant, and later in the
season than the asexual reproduction. The tissues
of the host-plant containing the sexual organs of the
parasite are generally enlarged (hypertrophied) and
distorted.

2. In the material given you observe the large spherical

odgonium, containing a single odsphere or egg
surrounded by the so-called periplasm or epiplasm.
Is the odgonium sessile or stalked?
Closely appressed to the odgonium at some point
find the smaller antheridium. Describe its shape,
and general appearance. Are its contents separated
from those of the hypha by a cross-wall?

4. How does the male gamete (sperm) pass through
the o6gonium-wall and periplasm to the egg?

5. If your material is suitable, observe and describe
the mature fertilized egg (odsperm). After fertili-
zation the periplasm becomes transformed into the
wall of the odsperm. Note the exospore (of one
layer) and the endospore of three layers.

6. Make drawings showing all features observed un-
der G.

H. General Questions:
1. Explain how Albugo is disseminated.

I24 MORPHOLOGY AND LIFE HISTORY

2. What weather conditions would favor its dissemina-
tion?

3. The blight caused by Albugo is difficult to eradicate.
What characteristic of the plant helps to explain
this fact? 3

4. Classify the Phycomycetes you have studied as
either Zygomycetes (Section 1), or O6mycetes (Sec-
tion 2), and give a reason for your classification.
Give the literal meaning of these two new terms.

Agaricus campestris (MEADOW-MUSHROOM)! ©

A. Classification:
Division I. Thailophyta.
Subdivision B. Fungi.
Class V. Basidiomycetes.
Series. Eubasidiomycetes (true or typical Basi-
diomycetes). |
Sub-class. Hymenomycetes.
Order. Agaricales.
Family. Agaricacee.
Genus. Agaricus.
Species. campesiris.
B. Habitat: | .

1. From your own observation, and from the class
discussion and assigned readings, describe the
habitat of this plant.

C. Naked-eye Characters:

1. Form—Describe the form of your specimen. If
specimens of different ages are available, compare
their forms and describe any variations in specimens
of various ages. Is the form of the mature speci-
men constant? Is its size constant?

2. Color—Describe accurately, noting especially any
variations in color. |

3. Structure—Note the differentiation of the plant-
body (thallus) into an expanded portion (pileus),

1 The outline for the study of a fleshy fungus has been prepared with
special reference to the meadow mushroom (Agaricus campestris). It is
general enough, however, with the exception of the outline of classifica-
tion, to apply to any gill-bearing form. Indicate in your notes the exact

genus and species given you for study.
125

126

MORPHOLOGY AND LIFE HISTORY

borne on a stalk or stipe. Is there a ring of tissue
(annulus) around the stipe?
(a) The pileus. Describe the shape, size, color,

(0)

(c)

and any characteristic markings on its upper
surface. Examine carefully and describe the
margin of the pileus. Are there any charac-
teristic elevations or depressions on the pileus? —
If so, state how many and where they are.
Compare the color of the under surface in young
and old specimens.

Describe the shape, arrangement, relative
number and color of the lamelle, or gills.
Are the margins (free edges) of the gills entire
or notched? Do they extend clear to the stipe?
Are they attached to the latter? Do they all
extend clear to the margin of the pileus?
Describe any variations in size. Count the
gills in a space of 1o mm., then calculate from
the circumference of the pileus the total number
of gills.

The stipe. Describe its shape, and color, and
any variations in color and diameter. Describe
its mode of attachment to the pileus. De-
scribe the method of attachment of the plant
to the substratum. Is there a mycelium or
other special means of fixation? If so, is it

. continuous with the tissues of the stipe?

The annulus. If an annulus is present, de-
scribe its location on the stipe; its structure.
Compare its structure with that of the mem-
brane on the edge of the pileus. What is the
relation between the membrane and the annulus
in young specimens? When these structures
are united they form a veil. Is a veil present

= AGARICUS CAMPESTRIS 127

in young specimens examined by your What
do the annulus and marginal membrane repre-
sent?

(d) Make drawings, not less than life size, of both a
young and a mature specimen, as seen from the
side, labeling all parts.

(e) With a sharp scalpel or razor carefully divide
your specimen longitudinally through the
middle, and make a drawing illustrating all
features shown in longitudinal sectional view.

(f) Make a third drawing showing the structure
and outline of the stipe as seen in cross-section,
and a fourth drawing, showing the outline of the
gill as seen in cross-section.

D. Microscopic Characters:

1. When suitable material is available, note and de-
scribe the mycelium, extending through the soil.

2. The annulus and stipe. Mount (in clearing fluid
or water) thin longitudinal sections passing through
the stipe. Is the stipe composed of distinct tissues,
e.g., like the hypocotyl of Ricinus, or the thallus of
Fucus? If so, describe. Observe that the stipe is
composed of hyphe. Of what is the annulus
composed, and what is its relation to the tissue of
the stipe? Do the hyphe have cross-walls or
septa? If so, what angle do the septa make with
the walls of the hyphe? Do the hyphe branch?

Do you find spaces between the hyphe? If

so, describe their size and distribution. Make a

drawing to show the features observed under 2.

3. The pileus. Mount (in clearing fluid) a thin longi-
tudinal section passing through the stipe, pileus, and
a portion of a gill) Examine under low power.
Can you trace the hyphe of the stipeinto the pileus?

pleas. De acy cuiciek eee
4. Make a diagram, lie swe, to Deinaie the relation

ti each other of tthe Inypiee af tthe mnyodem, siupe,

Siecr Sian olf tes antic wiekiel 4s tie
pull. Distinguish i i two Hands af cells, (@) cia

Bey Sewage woe ak ‘ac Ob-

i ae ee and the mummlber aif
cls of wich they are composed. Kitkeolral
the spores comiami? To wha & the clo Gi the
gills duc? |
4. i a pilems with the sitpe remowed & pond wih
the gills down ower 2 Cea, smooth piece ol paper
(black or white according to the spenes used), them
coversd with 2 tembler @ other smizble gas
Gh, and left ower met, a pom of tthe spores, 2s
they fell from the oils, willl be found om the paper

7:

AGARICUS COMPESTRIS 129

in the morning. Study aspore-print of this species,
describe it fully and state how it was formed.

. Make accurate drawings showing all features ob-

served under £, 2 and 3.

. Sexual reproduction is unknown among the fleshy

fungi. )
Diagram the life history of the species studied.

F. Nutrition and Growth:

Tr

Ds

Could the mushroom exist independently of other
plants? Consider this question thoughtfully and
answer as fully as possible in a well-worded para-
graph. |

Suggest an explanation for the rapid growth of
mushrooms.

G. General Questions:

Bs

State whether there is a division of physiological
labor in this plant, and, if so, to what extent.

. In what ways may this plant become widely

distributed?

. State, with reasons, whether you consider the mush-

room a more or less highly developed plant than
(a) Spirogyra; (b) Polypodium.

B. Habiiai:

i. Examine the specimens exhibited m the laboratory,
and state what plants are infested with this parasite.
What is the significance of its specific mame
(gramimis)?

2. Puccimia gromimis requires two different kinds of
hosts in order to complete its Ife history. One of
these is the barberry (Berberis). The barberry-
stage, however, is not absolutely essential, for m
certain regions, e.g., Australia, the Central Western
States, and California, where the barberry does not
naturally grow, this stage may be omitted, the
fungus being perhaps Carried over the winter season
on winter oe or giro: by mycelium m

C. Naked-eye Characiers:

1. Study the infected leaf of the barberry. On its
under surface observe the Custer-cups or #cia
(sing., 2cium)-

130

4.

PUCCINIA GRAMINIS 131

. On the upper surface observe the small dots, the

pycnia (pycnidia, or spermatia), What is their
color? Their shape? What relation does their
position bear to that of the «cia?

. Study both ecia and pycnia with the aid of a hand

lens. Describe carefully the appearance of the
infected areas.

Make a drawing, life size, of the barberry leaf, show-
ing the features under C, 1-3.

. Microscopic Characters:
I.

Study longitudinal sections through an ecium,
using low power.

. How are the infested issues of the host affected by

the parasite?

. Note the geciospores. Describe their shape. Are

they all of the same shape and size? How are they
produced? What is the cause of the cluster-cups
that appear on the leaf-surface?

. Make out all you can of the details of the mycelia,

and their relation to the cells of the host-plant, and
describe.

. Make a drawing of two ecia in different stages of

development, one before the epidermis of the leaf
has been ruptured. Make the ecium at least
30 mm. in longest dimension.

. Make a study, similar to that outlined in D, 1-s,

of the pycnia, as seen in longitudinal section. Ob-
serve the slender threads and the minute spermatia.

. What is the function of the eciospore? Of the

pycnia?

UREDO-STAGE (on Wheat, Triticum vulgare)

E. Naked-eye Characters:

I.

Study the diseased spots on the leaves of the wheat.

132

2.

3-

MORPHOLOGY AND LIFE HISTORY

Use the hand lens, if necessary, to make out the
features clearly.

Is the shape of the spots (sori, sing., sorus) uniform
and characteristic?

State their color.

F. Microscopic Characters:

om

Ow

wn

Study longitudinal sections through a uredo-sorus.
If the material is not fresh, remove some of the
contents of the sorus with a needle, and mount in
water. Study under high power.

. Describe the color, shape, and relative size of the

cells. Are there any surface marks? Do you find
any remnants of the pedicle to which the uredinio-
spore was attached? What can you say of the
thickness of the cell-wall?

. Of how many cells is the urediniospore composed?
. Make careful drawings of two or three uredinio-

spores, at least 15 mm. in longest measure.

. State the function of the urediniospore.

TELIAL STAGE (on Wheat)

G. Naked-eye Characters:

i

Study the telial sori, as directed under E, above.
Describe the order of their distribution.

H. Microscopic Characters:

i
2.

Study as directed under F, above.

Include in your notes, at this point, a description
of the germination of the teliospore (teleutospore).
What is its function? State the function of the
basidium (promycelium), and of the spring-spores,
or basidiospores (sporidia).

I. General Questions:

I

. What features seem to you to make this parasite

easily distributed, and difficult to eradicate?

i PUCCINIA GRAMINIS 133

2. State, with reasons, whether you would consider
Puccinia graminis higher or lower in the scale of
life than Vaucheria (or Fucus), and Albugo (or
Mucor).

3. Write a brief summary of the life history of Puccinia
graminis, and devise a diagram to illustrate this.

NOTE

From the fern to the wheat rust we have studied plants
in the descending order, from higher to lower in the scale.

We now return to the ferns, taking the quill-wort
(soetes), illustrating the Eusporangiate.

The systematic relationship of the Isoetacez is doubt-
ful. On the basis of certain structural features of the
gametophyte (e.g., the structure of the archegonia, and
the possession of multiciliate sperms), some botanists
class them with the Pteridophyta. On the other hand,
some features of the anatomy of the sporophyte (e.g., the
possession of a ligule on the sporophyll) suggests that
they are more closely related to Selaginella (Lepido-

phyta).

Isoetes (QUILLWORT)

A. Classification:

Division III. Pteridophyta.

Class I. Eusporangiate.
Order. Isoetales.
Family. Isoetacez-.
Genus. TJsoeies.
Species. (e.g., lacusiris.)

B. Habiiai:

Some forms grow on the bottom of ponds, others in

moist meadows, or on the margins of bodies of water.

THe SPOROPHYTE

C. Naked-eye Characiers:
1. General Features.

(a) Note the differentiation of the plant into root
and shoot, and of the shoot into stem and leaf.

(b) Make a sketch, natural size, showing the
general appearance of the entire plant.

2. The Siem:

(a) Without removing any of the leaves or roots,
ascertain all you can about the shape, size,
branching, and other characters of the stem,
and describe.

(6) With a sharp scalpel, make a cross-section of
the stem through the middle, being careful not
to remove any of the leaves or roots.

(c) Describe the outline of the stem as seen in
cross-section. Note the longitudinal furrows
which give it a lobed appearance.

134

<a

ISOETES 135

(d) Are the roots attached to any special region of
the stem? If so, describe.

(e) Study the cross-section, identifying the central
(vascular) cylinder, the epidermal layer, and,
between the two, the fleshy tissue composed of
several regions that are not distinguishable
to the naked eye.

(f) Make a drawing (X 3), showing the outline of
the stem in cross-section, the tissue-regions
observed, and the attachment of the roots.

. The Roots.

(a) Describe the general appearance of a single root.
Does it taper? Note that it is slightly fleshy.
Are the branches forked at the tip (dicho-
tomous), or lateral? Dichotomous branching
of roots is very rare.

(b) Make a drawing (X 2) showing these features.

. The Leaves.

(a) Carefully remove one of the outer leaves at its
point of attachment to the stem, first noting
carefully which is its inner (ventral) surface,
and which is its outer (dorsal) surface.

State whether the leaf is sessile or petiolate.
The end by which it is attached is the leaf-
base and the remainder of the leaf is called the
lamina or blade. Note that the blade is
subulate (awl-shaped).

Describe the exact length of the leaf in milli-
meters. Observe the slight shallow groove or
flattening. On which side of the leaf is it?
Hold the leaf up to the light and observe the
single vascular bundle, surrounded by air
chambers separated into compartments by
numerous diaphragms.

(b

A

A

(c

(d

~~

136

MORPHOLOGY AND LIFE HISTORY

(e) Make a drawing (X 2) illustrating the features
mentioned in 4, (c) and (d).

(f) Make a cross-section of the blade near the
middle, and note the number of air chambers
surrounding the vascular bundle.

(g) Make a diagram, 10 mm: in diameter, showing
the leaf-structure im cross-section.

(k) On plants which grow water no stomata
occur, but they are present on leaves that grow
exposed to the air. Are stomata present in
your specimen? If so, make a drawing of
two or three, each 15 mm. in longest diameter.

(¢) Study carefully the expanded base of this leaf,
noting the membranous margins.

(k) Directly above the leaf-msertion, and on the
ventral (inner) surface, observe the cavity or
pit (fovea), containing the single sporangium.

(1) Note the thin membrane (velum) extending
over the sporangium. The velum is formed by
the projection of the margin of the fovea. It is
absent in some species, and im J. lacusiris it
does not completely cover the sporangium.
In terrestrial species there is no opening through
it. State the shape and location of this open-
ing in your specimen, using a hand lens for the
observation.

(m) Above the fovea find a flat, membranous out-
growth, the ligule. Describe its shape and
state toward which end of the leaf it projects.
The slightly swollen base of the ligule is in-
serted in a depression (foveola) smaller than the
fovea and directly above it. This last point is
not easily made out except with the aid of a
hand lens or microscope.

ISOETES 137

(x) Make drawings as follows:
(1) A leaf-base, 20 mm. at greatest breadth
showing all points observed under 4,
()-(m).

(2) A diagram, 40 mm. in greatest width, of an
imaginary cross-section, of the sporophyll,
taken through the middle of the fovea.

(3) A diagram, 15 mm. in greatest width, of
an imaginary median longitudinal section
through the base of a sporophyll.

D. Asexual Reproduction:

E.

Note that some of the sporophylls bear large spores
(megaspores), and some small spores (microspores).
Study any constant differences (a) in structure,
(b) in position on the stem, between the mega-
sporophylls and the microsporophylls. Define each
of these terms.

. How many megaspores does a megasporangium

contain?

. Measure the diameter of a megaspore in millimeters.

Study and describe its shape under the low power
(mounted in water), noting any surface marks.
Explain the presence of angles on the spore.

. Make a drawing of a megaspore, 20 mm. in diameter.

Indicate the amount of enlargement.

. Study microspores under high power, describing

their shape and surface marks. Draw two or three
to the same scale as the drawing of the macro-
spore. The number of microspores in I. echinospora
is said to be from 150,000 to 300,000; of megaspores
150 to 300.

. Why is Jsoetes a heterosporus pteridophyte?

Compare it with Polypodium vulgare in this
respect.

138

MORPHOLOGY AND LIFE HISTORY

THE GAMETOPHYTE

The germination of the spores and the development
of the male gametophyte from the microspore, and of the
female gametophyte from the megaspore, are very
dificult to follow, and will be omitted here. The struc-
tures of the gametophytes, and the process of sexual re-
production should be carefully studied in a text-book,
and demonstrated by the instructor, if material is available.
E. Nutrition and Growth:

1. Is the gametophyte at any stage dependent upon
the sporophyte? The sporophyte upon the game-
tophyte? (Consuli a text-book.)

2. It is important to remember that:

(a) The microspore begins to germinate before it is

(6)

set free, dividing into two cells, alarge one and
a small one. The smaller cell constitutes the |
entire vegetative portion of the male gameto-
phyte. The larger cell develops into an an-
theridium, consisting of four wall-cells, and four
central cells. Each of the latter develops into
a multiciliate, spirally coiled sperm, resembling
those of the true ferns.

The megaspore begins to germinate after it is set
free. It never develops chlorophyll-bearing
tissues. Jn germination the nucleus divides
into about 50 nuclei before any cells are formed.
Then cells begin to be organized about the
nuclei, forming a small-celled tissue in the apex
of the spore (where the three ridges meet),
and a larger-celled tissue below. Archegonia
then develop in the small-celled tissue, and the
larger-celled tissue serves to nourish the young

ISOETES 139

embryo-sporophyte, that develops from the
fertilized egg.

The archegonia are exposed for fertilization
by the splitting of the wall of the megaspore
along the ridges, but the prothallus itself does
not project beyond the walls of the spore.

When the sporophyte begins to develop from
the fertilized egg, it continues to grow, without
any resting period, until it is mature.

3. Diagram the life cycle of Jsoetes, as directed for
Marchantia. Let MG = male gametophyte; FG =
female gametophyte; s = sperm; e = egg; S =
sporophyte; mi = microspore; mg = megaspore.

Equisetum (HorsETAIL)

A. Classification:
Division IV. Calamophyta.
Class II. Equisetinez.
Order. Equisetales.
Family. Equisetacez.
Genus. Equisetum.
Species. (e.g.) arvense.
B. Habitat:

1. The field horsetail (Z. arvense), is common along
railway embankments, roadsides and fields. It
apparently prefers north-facing slopes, and has a
great tendency to become weedy. |

C. Naked-eye Characters:

1. The Stem.

(a) Using herbarium specimens or alcoholic material,
if fresh material is not available, observe the
underground stem (rhizome), and the upright
aerial branches.

(b) Of the latter, observe two kinds; (1) non-green,
unbranched, bearing only scale leaves, and
terminating in a prominent strobilus or cone;
(2) green and branched, bearing leaves, but
no cone.

(c) Which kind of aerial branch appears firstabove
groundinthespring? Whatadvantage may this
possess for the species?

(d) Explain the physiological significance of the
green color of the non-reproductive branches.

140

EQUISETUM 141

Of what significance, in this connection, is their
profuse branching?

(e) Describe the surface of the stem along the
internodes, noting the presence or absence of
ridges, the hardness (or otherwise), and the
“feel” of the surface. To what are the last
two characters due?

(7) If material of Equisetum hyemale (the “scour-
ing rush”’) is available, it will be instructive to
burn a portion of the stem in a Bunsen flame,
and to examine the unburned portion under
a microscope. The preservation of the cell-
walls, uninjured by the flame, is due to the
fact that they are impregnated with silica,
taken up by the plant from the soil in the
form of a silicate, and secreted by the proto-
plasm of each individual cell. It is the pres-
ence of the silica that made this species useful
for scouring cooking utensils, and thus gave it
its common name.

2. The Leaves.

(a) Describe the shape and character of the leaves;
their arrangement on the stem (7.e., opposite,
alternate, or whorled).

(b) Do the leaves function in the work of photo-
synthesis? In what organ or organs is that
function performed?

(c) To what, in the fern, are the branches of the
vegetative part of the stem analogous? To
what are they homologous? ‘To what, in the
fern, are the scales at the nodes analogous?
To what are they homologous? Explain.

3. The Roots. —
(a) Briefly describe their character and distribu-

142

MORPHOLOGY AND LIFE HISTORY

tion. Does their distribution on the rhizome
bear any constant relation to the point of origin
of the aerial branches?

4. Make drawings showing all points observed under
G13:
D.. Asexual Reproduction:
1. Vegetative Propagation.

(a)

Describe the possibility of the multiplication
of new individuals by isolating pieces of the
rhizome.

2. Reproduction by Spores.

(a)
(0)

(c)

(d)

(e)

Sketch the strobilus or cone (X 3).

Make a cross-section of the cone at about one-
third of the distance from the apex, and observe
the central axis, and the manner in which the
sporophylls are borne.

Carefully dissect off a sporophyll, and observe
(1) its stalk; (2) its peltate (shield-like) top;
(3) hanging from the under surface of the
shield, the sporangia. How many sporangia
on each sporophyll? Examine several sporo-
phylls to see if the number of sporangia is
constant. Describe the dehiscence of the
sporangia.

Examine the spores under the microscope.
Can you detect more than one size; 7.e., is
Equisetum a homosporus or a heterosporus
plant?

Describe the appendages (elaters), of the
spores. How many on each spore? They are
formed by a modification of the outer coat of
the spore. Observe their behavior when
breathed on at frequent intervals.

(f) While the spores are morphologically homo-

a a a ee

EQUISETUM 143

sporous, they give rise to dicecious gameto-
phytes. Are they, therefore, physiologically
alike?

(g) Since the spores have different sex-value, some
giving rise to antheridial, others to archegonial
prothallia, suggest the advantage of the hygro-
scopic elaters in tending to tangle up together
several spores before they germinate.

(k) Make drawings illustrating all points observed
under D, 2, (a)-(/).

E. Sexual Reproduction:

1. It is not essential, in an introductory course to
study the gametophytes, and sexual reproduction
of Equisetum, and it is seldom possible to secure
suitable material in sufficient quantity for a large
class.

2. If material is abundant and time permits, the
gametophytes may be studied, described, and
sketched, noting especially color and general form,
branching, rhizoids, Pale sont antheridia, and
the dicecious habit.

3. From prepared slides further details as to arche-
gonia, antheridia, eggs, sperms, and fertilization
may be studied, under the instructor’s direction.

F, Division of Physiological Labor:

1. Write two or three paragraphs describing the
division of physiological labor, (a) as between
various vegetative processes, and (b) between the
latter and reproductive processes. Give special
attention in this to the work of each of the three
kinds of branches.

G. Life Cycle:

1. Make a diagram, as previously for other forms,

illustrating the life cycle of Equisetum.

Lycopodium (CLUB-Moss)

A. Classification:
Division V. Lepidophyta.
Class I. Lycopodinez.
Order. Lycopodiales.
Family. Lycopodiacez.
Genus. Lycopodium.
Species. (e.g., clavatum.)
B. Habitat:

1. Nearly all the species of Lycopodium prefer moist
situations, and one or two of them are aquatic.
They are widely distributed over the earth, in both
hemispheres, from the torrid to the frigid zones,
and commonly grow in shady or partly shaded
places. Lycopodium Selago and a few other species
are epiphytic. They all prefer a substratum rich
in humus or other organic matter.

THE SPOROPHYTE

C. Naked-eye Characters:
1. General- Features.

(a) Note whether, or not, the plant is differentiated
into root and shoot, and the latter into stem
and leaves. If the stem branches, briefly
describe.

2. The Stem.

(a) Describe the attitude of the stem (e.g., erect,
trailing). Does the tip of the stem turn up,
or otherwise?

144

e LYCOPODIUM 145

(6) Describe the mode of btanching.

(c) Are there any specialized (e.g., cone-bearing)
branches?

(d) Is there a terminal bud? Lateral, or axillary
buds?

3. The Roots.

(a) Does the stem bear roots only at its posterior
end, or otherwise? Describe.

(b) Briefly characterize the roots.

4. The Leaves. |
(a) State their manner of distribution on the stem.
(b) Describe an individual leaf.

5. Make drawings as follows: (1) of a portion of the
stem, to show mode of branching, distribution of
leaves and roots, and other general features, natural
size; (2) a leaf (X 5).

. Asexual Reproduction:

1. Vegetative Propagation.

(a) Describe the method of propagation by the
annual apical growth of the stem.

(b) Does the species you are studying in the
laboratory possess buds or bulbils that may
fall away, and develop into new plants? If so,
describe their distribution on the stem; their
relation to leaves, etc.

2. Reproduction by Spores.

(a) Describe the location of sporangia, especially
their relation to leaves. Are they borne in the
leaf-axils or on the leaf-surface? If the latter,
on which surface? What relation do they bear
to the leaf-base? Is there more than one

_ sporangium to each leaf?

(b) Are there special sporophylls? If so, how do

they differ in location and characteristics
10

146

(c)
(d)

(e)
(7)

MORPHOLOGY AND LIFE HISTORY

from the foliage-leaves? Are they aggregated
in a cone? If so, what effect does the forma-
tion of the cone have on the further growth of
the branch?

Is Lycopodium a homosporus or a hetierosporus
plant?

Describe a single sporangium, its mode of
dehiscence, and the relative number (2.e.,
few or many) of spores it bears.

Into what do the spores develop?

Make drawings as follows: (1) a cone (X 4);
(2) a sporophyll, with sporangium (X 10); (3)
under the low power a few of the spores, and
(from younger sporangia) a few of the spore-
tetrads.

THE GAMETOPHYTE

E. Sexual Reproduction:

1. The gametophyte of Lycopodium is rarely seen, and

not readily obtained in artificial culture. Its
laboratory study may be omitted in a beginning
course, but the subject should be presented by
lecture, or preferably studied from a text and then
discussed in class, with demonstrations of preserved
material.

2. Diagram the life cycle of Lycopodium.

Selaginella (LitTLE cLUB-Moss)

. Classification:
Division V. Lepidophyta.
Class I]. Lepidodendrinez.
Order. Selaginellales.
Family. Selaginellacez.
Genus. Selaginella.
Species. sp. (Any available species may
be used.)
. Habitat:
1. Various species of Selaginella are common in cul-
tivation in greenhouses. In nature they usually
grow in moist situations, usually preferring shade.

THE SPOROPHYTE

. Naked-eye Characters:
1. General Features.

(a) If possible, observe plants of various species
growing in greenhouses, noting their general
appearance and habit (e.g., erect, climbing,
trailing).

2. The Stem.

(a) By breaking off a small piece from the end of
your specimen, ascertain whether the stem is
tough, brittle, fibrous, etc.

(b) Describe the mode of branching (e.g., alternate,
opposite, dichotomous (forked), etc.). Do the
branches bear any relation to the leaves, e.g.,
are they in leaf-axils?

147

148 MORPHOLOGY AND LIFE HISTORY

' © Is the branch differeniiatted nto regions? Ff
so, briefiy desonbe.

(@) Does the branch show 2 temdemcy to be dorso-
ventral? How do you detemmme tis?

(e) Do you note, m entire plants, any indications
of respomse to gravity, momsture, or the direction
of light?

2. The Lewes.

(c) Describe then positiom om the stem. Is the
flat appearamce of the stem due to the leaves
bemg opposite, or to the attitude they have
assumed 2s they mature.

(®) Ave the leaves differentiated imto petiole, blade,
etc?

(c) Describe any apparent adjustment or arrange-
ment resulting im the most favorable immmm:-
tiom of lezwes.

(@) Describe amy variations im the color of the
leawes, amd endexvor to account for it.

3. The Raois-.

(@) Is the plant rooted m the soil?

(@) Do the roots bramch? If so, desombe.

(c) Are there amy other roots besides those m the
soll? Ji so, desonbe them, and them location,
and suggest any advantage they may be to the

plant.

(@) Make drawmegs to Mlusirate all characters
observed, imcludimg (2) 2 portiom of the leafy
bramch (X 2); (2) a leaf (X 10); (3) aerial roots,

(a) Mysistun cadiee: Sekine Seb aeiauhes ee ee
ing fluid om 2 side. Observe under the micro-

SELAGINELLA 149

scope, using low and high powers, and describe
all details of leaf-structure thus brought out,
including

(b) The shape and arrangement of the cells; the
color, size, and distribution of the plastids in
the cells; any other cell contents;

(c) Variations between marginal cells, those along
the central axis, and those lying between.
Account for any constant differences observed.
Do you think any observed differences may be
attributed to environment? Explain.

(d) Can you identify a tiny, membranous flap,
the ligule, near the leaf-base? On which side
of the leaf (dorsal or ventral) is it? Be sure
to examine both sides of the leaf in this connection.

(e) Are there stomata? If so, describe their
location.

({f) Make drawings sufficiently large to illustrate
all points observed under D.

. The Stem.

(a) With the razor, make thin cross-sections of
the stem, and mount them in water or clearing
fluid.

(b) Is the stem differentiated into (1) epidermis;
(2) vascular regions; (3) fundamental tissue
(cortex)? If so, describe.

(c) Note the presence or absence of air-spaces.

(d) Compare the tissue-system of the Selaginella

F stem with those in the fern.

(e) Describe the distribution of xylem and phloem
in the vascular bundle.

(f) Do you find indications of vascular bundles
passing out to the leaves?

I5° MORPHOLOGY AND LIFE HISTORY

(zg) Draw a section of the stem (X 20), to illustrate

2, (a)-(¢).
E. Asexual Reproduction:
1. Vegetative Propagation.

(2) Describe any means of vegetative propagation
disclosed by your observations, already made.

(0) If opportunity offers, the vegetative propaga-
tion of Selaginella may be experimentally
demonstrated in the greenhouse or Wardian
case.

2. Reproduction by Spores.

(cz) Observe the “cones.” How are they dis-
tinguished? Are they terminal on the main
branches, or axillary?

(6) Draw (X 5).

(c) Place a small portion of a branch, bearing several
mature cones, under a glass bell-jar, and after
twenty-four to forty-eight hours observe the
distance to which the spores have been projected.
Note the two kinds, their relative number, and
differences in color, etc.

(d) Carefully remove sporophylls (x) from near the
base of the cone; (2) from the middle or above,
and mount in water or clearing fluid, keeping
distinct, on separate slides, those from the two
regions.

(e) Note both megasporophylls, bearing mega-
sporangia, and microsporophylls bearing micro-
sporangia. How are they distinguished?

(f) Are the sporangia inserted on the leaf, or on
the stem in the axil of the leaf? Compare with
the other plants studied in this respect.

(g) Describe the structure of the walls of the

sporangia.

<a

SELAGINELLA I51

(h) Carefully count and record the number of
megaspores in one megasporangium. Is the
number always even?

(i) Carefully observe the megaspores under a high
power, and endeavor to account for their shape.

(7) Make drawings to show all points observed
under E, 2, (a)—(h).

(k) Make a study of the microsporophylls, micro-
sporangia, and microspores, similar to those
just made under E, 2, (a)—(2).

(1) The number of microscopes is too large to
permit of their being readily counted. Sug-
gest any advantage to the plant in such a large
number of microspores. Explain the cause of
the difference in size. Suggest an advantage
to the plant in the large size of the megaspore.

(m) Mount megaspores and microspores together
and make drawings to show their relative
sizes,

(n) Make drawings to illustrate all points observed
under E£, 2, (k).

F. Sexual Reproduction:

1. The gametophytes of Selaginella are not readily
obtained in suitable form for study. If prepared
slides are available, studies may be made of:

(a) Archegonia and eggs.

(b) Antheridia and sperms.

G. Comparisons:

1. Compare the relative prominence of the gameto-
phyte and sporophyte in Selaginella. Compare,
in this respect with all the forms previously studied.

2. Compare the method of reproduction by spores in
Selaginella with that in the forms previously
studied. Why should Selaginella be considered

I52 MORPHOLOGY AND LIFE HISTORY

either higher or lower im the scale of life than ~
those forms?
H. Life Cyde:
1. Make a diagram to illustrate the life cycle of
Selaginella. Briefly state differences between this
life history and that of the fern, and of Anihoceres.

Zamia floridana (A cycapD)

. Classification:
Division VI. Cycadophyta (The Cycads).

Class II. Cycadinez (Modern Cycads).

Order. Cycadales.
Family. Cycadacez.!
Genus. Zamia.
Species. floridana.

. Habitat:

1. Most of the Cycadales occur only within the tropics,
but two genera, Zamia and Cycas, are subtropical.
_Zamia occurs in the United States only in Florida,

_ ‘where it is rather common. It is frequently culti-

vated in greenhouses.

VEGETATIVE ORGANS

. The Stem:

1. Briefly describe the stem, noting its general appear-
ance, size, relation between its diameter and height,
variations in diameter, character of the surface, its
relation to the surface of the soil. Note the pres-

ence or absence of branches.
. The Leaves:

1. Describe their arrangement on the stem, the nature
of the blade (entire, divided, etc.), the color, and

1 By some botanists the genera Zamia, Macrozamia, and Dioon, having

both staminate and carpellate cones, are assigned to a separate family
(Zamiacee), distinguished from the Cycadacee (in the narrower sense),

which bear only the microsphorophylls in cones.

153

154

3.

MORPHOLOGY AND LIFE HISTORY

the presence or absence of a petiole. Describe
accurately the vernation (condition in the bud), as
shown by young leaves just unfolding.

. Suggest any advantage to the plant of any of the

facts recorded under D, tr.
Compare the character of the leaves with that of
any of the ferns.

E. The Roois:

cm

Briefly state their location and functions.

REPRODUCTIVE ORGANS

F. The Siaminaie Cones:

I.

Describe their appearance, and, if the material is
suitable, their distribution on the plant.

. Describe, accurately, the distribution of the micro-

sporophylls (Stamens) on the main axis, or stem, of
the cone.

. Make drawings, natural size, showing (a) a surface

view of the cone; (6) the cone as seen in longitudinal
section?

. Remove one of the stamens. Describe it, and note

the microsporangia (pollen-sacs) attached to its
lower surface. Describe them, their number, dis-
tribution, mode of attachment, and manner of
opening (dehiscence).

. Make drawings (a) of a stamen with pollen-sacs

attached; (5) of two or three pollen-sacs (X 10).

. The staminate cone is in reality a primitive flower.

From this study, of what structure would you infer
that flowers are a modification?

G. The Male Gameiophyie:

I.

The young pollen-grain (microspore) begins to
germinate before it leaves the pollen-sac, two divi-

5 ZAMIA FLORIDANA 155

sions of its nucleus taking place. By the first cell-
division two cells are formed, one, the first prothal-
lial cell, representing the vegetative portion of the
male prothallus; the second, or antheridial cell
(called the ‘‘antheridial initial’? by some botanists),
divides again, forming a tube-cell and a generative
cell. By the division of the generative cell, the
stalk-cell and body-cell are formed. The division
of the body-cell gives rise to two sperm-mother-
cells, and each of these latter become transformed
into a motile sperm.

2. Complete the following diagram of the above se-
quence of cell-divisions:

Microspore
O

rae

First Proth. © O Anth. Cell
Cell

3. Mount several pollen-grains in water, and examine
them under the high power.. Describe their shape
and contents. Draw. ,

4. The study of the mature male prothallus, produced
by the formation of a pollen-tube, will be omitted
here.

H. The Young Carpellate Cone:

1. The youngest cones offered for study were collected
about March tr.

2. Describe the cone, and the distribution of the mega-
sporophylls (carpels) on its main axis, or stem.
Draw, natural size.

3. Carefully dissect! off one of the carpels. Describe

1 For economy of material, with large classes, excised carpels may be
supplied.

156

4.

MORPHOLOGY AND LIFE HISTORY

its form and surface characters, and note the num-
ber, and place and mode of attachment of the large
megasporangia (ovules). Note their color. Draw,
natural size.

Do you find smaller, undeveloped ovules? These
have probably not been pollinated.

I. The Young Ovule:

I.

Is the ovule enclosed by the carpel, or is it naked?
State why Zamia is classed as a gymnosperm.

. At the end of the ovule, opposite its point of attach-

ment, note the small, often slightly elevated, dark
spot, which marks the place of the micropyle (small ©
gateway), through which the pollen-grain passes
in order to reach the pollen-chamber within. This
process is called pollination. In Zamia, pollination
occurs about Jan. 1.

. Remove an ovule, carefully noting where and how

it is attached to the carpel.

. Describe its surface and shape. How may the

latter, in part, be accounted for? At the end
opposite the micropyle observe the scar (hilum),
where the ovule was attached. Draw.!

. With the scalpel, make a slight longitudinal incision

of the integument (wall) of the ovule, being careful
not to cut too deeply, so as to injure the delicate
structures within. Describe the character of the
tissue of the integument.

. The tissue next within the integument is the

nucellus, or megasporangium. The integuments
are outgrowths of the nucellus.

1 Arrange all the drawings, showing the ovule at different ages, serially,
on a new sheet of drawing paper, so as to facilitate the comparison of the
different stages, and to show at a glance the changes which the different
parts undergo.

ZAMIA FLORIDANA 157

7. After making a longitudinal incision, very carefully
remove the nucellus, noting the greater thickness of
the tissue at the micropylar end. ‘This tissue serves
as nourishment for the germinating pollen-grain.

8. Within the nucellus is the globular young female
gametophyte, or endosperm. Describe and (from
your reading in the text-book) account for its
consistency. |

9. With the razor make a median, longitudinal section
of the entire ovule. Study and draw, naming all
the parts.

J. Older Stages in the Development of the Ovule:

1. Examine ovules collected about April 1, as directed
under Z. Compare their size with that of the
younger ovules. Observe the fleshy texture being
assumed by the outer portion of the tissue of the
integument, and the differentiation of a harder
inner layer (endopleura).

2. Describe the changes which the nucellus has under-
gone. Account for these changes. (The appear-
ance of the nucellar tissue may be due, in part, to
its disintegration by the growing pollen-tubes.)

3. Remove the nucellus and describe the appearance
of the endosperm. Note the slight depression in
its micropylar end. What change has taken place
in its consistency? Account for the change.

4. With a scalpel cut away the endopleura, and then,
with a razor, make a clean, median longitudinal
section of the endosperm, and observe, imbedded
in its micropylar end, two or more archegonia.
These open into the depression mentioned above by
a short neck, composed of only two cells. The short
neck-canal may be seen if the section passes through
a suitable plane.

158

5.

Io.

MORPHOLOGY AND LIFE HISTORY

With a hand lens observe the wall of the arche-
gonium, and within, filling the venter, the large
ovum, or egg. ,

. As outlined above (J, 1-4), examine and describe

an ovule one month older (about May 1), carefully
noting the changes which the different parts have
undergone. Observe especially the development
of the hard inner layer of the integument. May
this feature be of any advantage to the plant?
If so, how? Does any of the nucellus remain?
If so, describe. Note, in the depression of the endo-
sperm, the openings into the archegonia. How many
are there? Draw this depression as seen in end
view.

. Construct a diagram of an ovule of this age as seen

in median longitudinal section, carefully labeling
all parts.

. Make a diagrammatic drawing of a cross-section of

the same ovule passing through the venters of the
archegonia.

. In ovules one month older (about June 1) the sac-

like proembryo may be seen, lining the walls of the
venter of the archegonium, and, growing from its
basal end into the tissue of the endosperm, the
prominent suspensor, at the free end of which the
embryo begins to develop. As the suspensor and
embryo increase in size, a cavity is formed in the
surrounding endosperm. This cavity results from
the digestion of the endosperm tissue, which goes
to nourish the growing embryo and _ suspensor.
Suggest how this digestion and subsequent nutri-
tion may be accomplished.

Make a drawing of a median longitudinal section
of the ovule at this stage.

« ZAMIA FLORIDANA 159

K . The Seed:

5 igs

The seed matures about July 1. Study the struc-
ture of a ripe seed, comparing it in every point with
the structure of the unripe ovule, as directed above
(J, 1-10).

. Note the soft, outer layer of the integument.

Describe it.

. In cutting away the hard, shell-like inner layer

(endopleura) be careful not to disturb the portion
of the nucellus that fits like a cap over the mycro-
pylar end of the endosperm. Now carefully lift
this portion of the nucellus and observe the long,
coiled suspensor attached to it, and (at its other
end) to the projecting thick, round peg (hypocotyl)
of the embryo.

. With the scalpel gradually remove one-half of the

endosperm, until you expose the embryo (young
sporophyte) imbedded in it. Is the embryo curved
or straight? Is it now confined to the venter of
the archegonium?

. Observe that the hypocotyl bears fleshy seed-leaves

(cotyledons). How many are there? Compare
their lengths.

. Does more than one embryo come to maturity in

any one seed?

. When the sporophyte of Zamia begins to develop,

is its growth continuous to maturity, or does a
period of rest intervene between two stages of
growth? Compare Zamia with the fern, moss, and
Selaginella in this respect.

. Define a seed, and state how it differs from an

unripe ovule, and from a spore.

. Suggest any advantage to the plant of the seed-

habit.

160 MORPHOLOGY AND LIFE HISTORY

L. Nutrition:

1. Describe the relative ability of the mature sporo-
phyte and the gametophyte to lead an independent
existence. Is the gametophyte ever independent
of the sporophyte? Does the sporophyte ever live
ee eee

ry0-Spo! te need a supply of
food stored in the seed?
3- Weel beet ey ee a

4. At leomee-widic'a: detent eanla Cees
undergone by a starch gram, formed im the leai of

RRL BAH AS: life nile of Zamia from
sporophyte to sporophyte. ;

Pinus laricio (AUSTRIAN PINE)

A. Classification:
Division VI. Spermatophyta.
Subdivision A. Gymnosperme.
Class I. Pinoidez.
Order. Coniferales (cone-bearing plants).
Family. Pinacez (pine family).
Genus. Pinus (the pines).
| Species. Jaricio (Austrian pine).
B. Habitat:
The Coniferales are widely distributed over the earth’s
surface, often forming extensive forests. The genus
Pinus occurs in North America throughout Canada
and the northern United States, from the Atlantic to
the Pacific coasts. The white pine (Pinus Strobus)
occurs from Canada south along the Alleghanies to
Georgia, and west to Illinois and Iowa. The western
yellow pine (P. ponderosa) extends south to western
Nebraska, Texas, Mexico, and California. The long-
leaved or “‘ Georgia pine” (P. palustris) is found near
the coast from Virginia to Florida, and Texas. The
spruce-pine (P. echinaia) also occurs as far south as
Florida, and in Illinois, Kansas, and Texas. Consider-
able forests of it are foundin southern Missouri. The
loblolly pine (P. tegda) extends along the coast from
Delaware to Texas and north up the Mississippi
Valley to Arkansas. Pinus laricio is not native to the
United States, but has been introduced into cultiva-
tion, as has also P. sylvestris, the ‘‘Scotch pine,” of
northern Europe, and other species.
Pine wood was formerly one of the most valuable and
DE 161

162 MORPHOLOGY AND LIFE HISTORY

at the same time one of the cheapest of soft-wood
timbers, but owing to an utter disregard of the prin-
ciples of scientific forestry, it is now one of the scarcest
and most expensive. Regions that were formerly
extensively forested, and the center of a prosperous
lumber industry, are now waste land, often occupied by
tall stumps, and a source of no profit. It is not neces-
sary to destroy the forests in order to obtain an abun-
dant supply of lumber, provided only that the crop be
harvested in accordance with scientific principles.

The conservation of the forests is one of the most important
economic problems confronting our country, and excellent
opportunities are now offered for well-trained foresters.

VEGETATIVE ORGANS
C. The Siem:

t. In Pinus the shoot, as usual, is composed of the
stem and the leaves. The stem is divided into a
main part, or trunk, and lateral branches. The
entire portion of the shoot, except the trunk, is
designated by foresters as the crown! of the tree.

2. The following observations (C, 3-10) of the stem
as a whole are to be made out of doors, recorded
at this place in the laboratory notes, and handed in
at the next class period.

3. Designate the type of the trunk as excurrent (i.e.,
extending, entire from the ground to the apex of the
tree), or deliquescent (7.e., extending entire for only
a short distance from the ground, and then sub-
dividing into the numerous limbs and smaller
branches of the crown?).

1The use of the term crown in this sense is quite different from its

older use by plant anatomists to designate the region (usually at or near
the surface of the ground) where the root and shoot join.

- PINUS LARICIO | 163

4. Describe variations in the diameter of the trunk.

5. Do you find prominent swellings (buttressing roots)
at. the base of the trunk? If so, suggest their

possible advantage to the tree.!

6. Describe the outline of the crown as flat, conical, or
cylindrical.

. Describe the appearance of the bark.

. Note that the lateral branches appear to be given
off in whorls, or circles, at regular intervals along
the trunk. Observe closely and state whether
these are true whorls (7.e., the component branches
in exactly the same horizontal plane), or pseudo-
whorls (i.e., the branches not really in the same
plane). |

9. Do you find enlargements on the under side of the
larger limbs at the base? Suggest any advantage
this may be to the limb; the conditions resulting
in their formation.

1o. Draw a diagram illustrating all points observed
: under C, 1-9. Make the trunk 15 dm. high.

D. The Vegetative Branches:

1. In specimens furnished, note the two kinds of vege-
tative branch: The main or “long” branch, bear-
ing scale-like leaves, and, in the axils (upper angle
made by the leaf with the branch that bears it) of
these scales, the dwarf branches, bearing the foliage-
leaves or pine “‘needles.”” In what does the long
branch terminate?

2. The Long Branch.

(a) Describe the arrangement (spiral) and dis-
tribution of the dwarf branches on the long ones.
(b) Note the rings of dry bud-scales or scale-scars

Co “I

1 The conditions favoring the formation of buttresses should be dis-
cussed in class.

amountol cach year’s srowth in leneith. Asner

’ tin the age of your specimen.

() Siete several ways im witch younger portions
of tthe stem may be Gisitmeuhe

@) For how many yours do the def Ianches
attached? The soaks thet sobiend
fdhemn? Observe the scars eit by the fllien

(¢) Tiustrate by 2 Grewine the fests: observed
under D, 2, (a@)@).

(7) Measure and record tthe amount of cach aml
prowth mn lenzth.

(g) Drew 2 horizontal line 2s memy Geometers lone
Ime into Gecimeter spaces, and at the end af each
dechneter erect 2 perpendicular 2s mmamy mol
aneters ineh 2s the branch grew Guring the come-
spondims year. Connect the ios of these
pempendiculas by 2 gently curing lime, winch
wall be the curve of auunel growth m leazih
for the pened covered.

(%) Sugpest reasons for the observed Gifierences im
ZmMoun amount of annual growth; for tthe Gmracion oi
erowth taken by the branch ait wamions times.

@) ele ee ones

> tthe mlniiwe postion of

any Chlorophyl? I so, im whet mgm & it

3. De Dwarf Bronch.
(@) Do you imd mods and miemotis, o any

other evidence thet these brenches gow @

> PINUS LARICIO 165

length each year? Find evidence that they
do not.

(b) Compare the number of needles borne by each
dwarf branch. Is the number constant? On
what part of the branch are they borne?

(c) Note the bud-scales, some of which form a
sheath about the bases of the needles.

4. The Foliage-leaves. )

(a) Describe their shape. Are they differentiated
into petiole and blade?

(b) Make a drawing, natural size, of an entire leaf,
and a diagram (X 10) of a cross-sectional view.

5. The Terminal Bud.

(a) Describe its color, coverings (bud-scales),
and shape. Draw (X 3).

(b) With the scalpel remove one of the bud-scales
at its base. Describe and draw (X 5).

(c) Now remove, one at a time, the remaining bud-
scales, having care not to break or injure the
tender inner tissues.

(d) Describe the place and mode of attachment
of the scales. .

(e) Explain how they are adapted, in structure and
position, to protect the bud. From what do
they protect it?

(f) Describe the color of the inner tissues. Can

Pinus form chlorophyll in the dark? Explain.

(g) Make a drawing (X 5) of the bud after the
_ scales have been removed.

(h) With a sharp scalpel make a median longi-
tudinal section of the bud. Observe the central,
conical axis, bearing thin membranous scales.
In the axile of each scale find a small knob-like
outgrowth.

166

MORPHOLOGY AND LIFE HISTORY

(i) Make a drawing (X 10) of the longitudinal view.

(k) Into what will the bud develop? What will
become of each of its parts?

(2) How much of your specimen represents last
year’s terminal bud? The bud of year before
last?

(m) When the annual growth of a branch ends with
the formation of a bud the growth is called
determinate. Is the growth of the dwarf
branches determinate or indeterminate? Of
the long branches?

E. Homologies:

1. Organs which perform like functions are analogous

to each other. Organs which correspond to each
other structurally, z.e., which have the same mor-
phological value, are homologous. For example,
the flat, chlorophyllous stems of cacti and the foliage
leaves of the maple tree are analogous, for they both
function as organs of photosynthesis; but they are
not homologous, for one is a stem, the other a leaf.
The bud-scales of Pinus and the pine “needles”
are homologous, 7.e., from the standpoint of struc-
tural value (morphological standpoint) they are
both leaves. But they are not analogous, for,
whereas the ‘‘needles”’ act as organs of photo-
synthesis, the bud-scales do not, as they have no
chlorophyll.

. One of the most important, and often most difficult,

problems of morphology is correctly to interpret
the structural value of an organ; in other words, to
recognize homologies; for any organ may be pro-
foundly modified, and appear so disguised as to
make it extremely difficult to recognize its morpho-
logical significance. Pinus furnishes an excellent

- PINUS LARICIO 167

illustration of the modification of organs for various
functions.

. Enumerate all the homologs of the foliage-leaf

found thus far on Pinus, and show why the organs
you name are homologous.

REPRODUCTION

. The Staminate Cone:
zr:

On which portion of the vegetative branch are the
staminate cones borne? Do they extend clear to
the tip of the branch, 7.e., are they ever terminal?
In what does the tip of the branch that bears
them terminate? Ascertain their length and
greatest diameter in millimeters.

. Are the cones subtended by (i.e., borne in the axil

of) a scale-like leaf? Note whether they are sessile
or stalked?

. Observe the spiral-like arrangement of the mi micro-

sporophylls of the cone.

. The staminate cones are modified branches. To

which of the vegetative branches are they homolo-
gous?

. Make a diagram (X 2) showing the mode of attach-

ment of the cone and the subtending scale.

. With a razor bisect a cone longitudinally and ob-

serve the central axis, bearing the microsporophylls,
or Stamens.

. With the aid of a hand lens, or dissecting micro-

scope, observe the short stalk of each stamen and,
on the under (dorsal) side of the broadened stalk,
two small pouches, the pollen-sacs (microspor-
angia), containing pollen-grains.

. Make a diagram (X 10) of the cone as seen in longi-

tudinal section.

168

r2.

MORPHOLOGY AND LIFE HISTORY

. Remove an entire stamen and observe that the

tip of it is turned up so as to fit over the end of the
stamen next above it. Suggest any advantage in
this arrangement.

. Make a drawing to illustrate this feature.
af:

Make a cross-section of the stamen and ascertain
of how many pollen-sacs it is composed. Draw.
The pollen-sacs of the stamen constitute the anther.
The structure of the staminate cone shows it to be
in reality a simple flower. It is homologous to the
staminate flower of some of the higher plants. To
what in Zamia is it homologous?

G. The Young Male Gametophyte:

I.

Mount several mature pollen-grains in water and
examine with the high power..

. Observe the body of the grain, and the two lateral

wing-like expansions, developed from the outer coat
of the pollen-grain. Suggest their use.

. Within the grain observe the tube-nucleus near the

center, and the generative cell near the wall farthest
from the wings. Look for the prothallial cell,
which frequently may be seen between the wall of
the grain and the generative cell.

. Make a drawing, 25 mm. broad, showing all features

observed under G, 1-3.

. The nuclear and cell-divisions which give rise to

these structures are steps in the germination of the
microspore. Into what does the microspore of the
heterosporus pteridophytes develop by germina-
tion? To what, then, in Isoetes or Selaginella, is
the mature pollen-grain of Pinus homologous?

. If prepared microscopic slides are available, more

detailed study may be made of the structure of the
pollen-grain.

- PINUS LARICIO 169

H. The Young Carpellate Cone:

1

Io.

If.

On which internode of the vegetative branch are
the carpellate cones borne? On what part of the
branch? Do they occur singly or in clusters? As
terminal or as lateral outgrowths?

. Note that each carpellate cone is borne at the tip

of a stalk. Describe any outgrowths on this stalk.

. Describe the attitude of the cone at the time of

pollination, as erect or pendant.

. Observe the spiral arrangement of the cone-scales,

somewhat more marked than in the staminate cone.
In fresh specimens the cone-scales are slightly
separated from each other at the time of pollina-

tion. Explain the advantage of this. )

. Make a drawing (X 2) of the cone with the stalk

that bears it.

. Make a median longitudinal section of the cone and

stalk, and represent by a drawing all parts seen.

. Carefully dissect off one of the central cone-scales,

being sure to note which is the inner (ventral) and
which the outer (dorsal) surface of the scale, and
observing the membranous bract which subtends it.

. On the inner surface of the scale, near the base,

observe with the hand lens two ovules, each with
two little prongs, between which is the pollen-
chamber; between and above the ovules a pointed
outgrowth.

. Make drawings (X 10) of the ovuliferous scale as

seen (a) from the side; (6) from the outer surface,
showing the bract; (c) from the inner surface,
showing the ovules. |

The ovules are megasporangia surrounded by a
protecting integument.

There is some evidence for considering the ovuli-

17° MORPHOLOGY AND LIFE HISTORY

Fr.

ferous scale and the bract that subtends it as a
megasporophyll, or carpel. On the basis of this
interpretation the bract would be homologous to the
ligule in Jsoetes or Selaginella. But other facts
argue against this theory, and lead to different
interpretations, so that the exact homology of the
organ isindoubt. Possibly it represents two mega-
sporophylls or carpels. Ifso, we must interpret the
carpellate cone, not as a flower, like the staminate
cone, but as inflorescence, or cluster of flowers, each
scale representing a flower. ,
The Mature Male Gameiophyie:
During the first spring pollination takes place, as
described in the text-book, and the growth of the
pollen-tube begins. Its growth is very slow, however,
until the following spring, when the growth becomes
more vigorous. The tube-nucleus passes to the tip of
the pollen-tube, which penetrates the tissues of the
nucellus (J, 6, p. 156), digesting a channel for itself as it
grows, usually branching, and feeding on the digested
tissue. The generative cell divides into a body-cell
and a Stalk-cell, and the nucleus of the body-cell
again divides into two sperm-nuclei.
The Female Gameiophyie:
Near the time of pollination the megaspore consists of
one uninucleate cell (the one-celled stage of the embryo-
sac). By repeated nuclear-divisions the nucleus of the
megaspore gives rise to a large number of nuclei, which
at first lie free in the surrounding cytoplasm; but later
each of these nuclei organizes about itself a cell,
surrounded by cell-walls. The tissue thus formed
within the embryo-sac, and enlarged by growth, forms
the young female gametophyte (endosperm). The
megasporangium, surrounding the endosperm, is called

PINUS LARICIO L7I

a

the nucellus, as in Zamia, and both these structures are

surrounded by a protecting envelope, the integument.

The pollen-chamber lies between the tip of the nucellus

and the integument. The micropyle leads through

the integument to the pollen-chamber. In the pol-
lination of Pinus the entire pollen-grain passes into
the pollen-chamber through the micropyle.

L. The Ovule:

The endosperm, nucellus, and integument together

form the young ovule. Nearly one year is required

for its development to the stage described above. In
the second spring, while the pollen-tube is rapidly
elongating, and the nuclear divisions noted above are
taking place within it, several archegonia develop in
the micropylar end of the endosperm. In the venter
of each archegonium lies the large egg.

M. Fertilization:

Eventually the pollen-tube enters the neck of an arche-

gonium (compare with the process in Zamia and other

Cycads), its contents are discharged into the venter,

and one of the sperm-nuclei fuses with the nucleus of

theegg. Thus fertilization is accomplished, about one
year after pollination. The transfer of the sperm-
nucleus to the egg by means of a pollen-tube is called
siphonogamy, and plants in which this occurs,

Siphonogamia.

The one-year-old cone, to be studied next, represents
the stage of development at about the time of fertiliza-
tion. The sperms of Pinus are non-motile.

N. The One-year-old Carpellate Cone:

1. Compare the position on the branch, and the atti-
tude of the one-year-old cones with that of the cones
at the time of pollination.

2. Study these cones as directed above (H, 1-11), com-

172 MORPHOLOGY AND LIFE HISTORY

paring the older and the younger organs. En-
deavor to explain any differences observed.

3. Record the length and greatest diameter of the one-
year-old cone, and make a drawing of it, natural
size.

O. The Two-year-old Carpellate Cone:

1. Record, its position on the branch, its attitude, and
dimensions. Compare it, in these points, with the
young, and one-year-old cones. Draw, natural
size. -

2. Make drawings of a detached scale as seen from
(a) the outer (dorsal) surface, (6) the inner (ventral)
surface, (c) the side. Describe any changes
observed in the appearance and relation of the
various points.

3. Note that the ovule has developed into a winged
seed.

P. The Seed:

1. The seeds are usually shed from the pine cone during
the third summer, about two years and a quarter
after pollination.

2. Record the dimensions, shape, and character of the
surface of the seed. The small depression in the
smaller end of the seed locates the micropyle, which
is now grown together. Draw, natural size.

3. Let fall from a height of several feet a seed of some
species having wings still attached, and note the
approximate time required to reach the ground.
Remove the wing and repeat the observation. Sug-
gest a use of the wing. Is it very firmly attached
to the seed?

4. Remove the tough, outer seed-coat (testa), which is

1 The large seeds of the nut-pine, Pinus edulis, or of Pinus pinea, may
advantageously be used for this study.

Io.

If.

I2.

PINUS LARICIO / £93

a

the mature integument, referred to in K and L
(p. 170-171). The integument is analogous to an
indusium. Why?

. Underneath the testa, observe the thin, membran-

ous inner seed-coat, formed by a separation and
differentiation of an inner layer of the tissue of the in-
tegument. Describe its color and surface-character
as seen under the hand lens. Compare with Zamia.

. Observe the small hole through the micropylar end
of the inner coat. What does this represent?
. Remove the inner seed-coat, having care not to dis-

turb the brownish, membranous cap on the micro-
pylar end of the kernel. This cap is the remains
of the nucellus (megasporangium). Note the modi-
fication of its tissue at the place through which the
pollen-tube passed on its way to the embryo-sac.
The remainder of the nucellus was consumed by
the female gametophyte during the development of
the latter.

. What is the homology of the white, fleshy kernel

of the pine seed.

. Make a drawing (X 4) of the endosperm and nu-

cellus.

Remove the nucellar tissue. Is it firmly attached
to the endosperm? Describe the appearance of the
endosperm under the nucellar cap.

Very cautiously separate the endosperm into longi-
tudinal halves. Begin the dissection at the end
opposite the micropylar end so as not to injure the
embryo-sporophyte within.

Observe that the embryo lies in a distinct cavity or
chamber, its tissues being quite distinct, anatomic-
ally, from those of the gametophyte. Can you ac-
count for the formation of this cavity ?

174

13.

14.

a

16.

r7)

18.

MORPHOLOGY AND LIFE HISTORY

Note that the embryo is composed of a main axis,
bearing a whorl of cotyledons borne near one end.
Can you detect distinct regions of the axis? If so,
how many, and how are they distinguished? How
many cotyledons are there? Is the number always
either odd or even? |
Observe that the embryo is attached at the end
opposite the cotyledons to a slender filament, the
suspensor. At this end of the embryo-chamber
may frequently be seen the disorganized remains of
other embryos that failed to develop. In rare
instances two embryos develop in one seed. This
is called polyembryony, a condition very common
in lemons, and other citrous fruits.

Make a drawing of the young sporophyte, 50 mm.
long.

Make a median longitudinal section of the embryo,
and observe that the portion of the axis below the
cotyledons (hypocotyl) is encased in an outer,
strongly developed root-cap, which completely en-
closes the hypocotyl. Note further that the coty-
ledons are borne on the hypocotyl. From its op-
posite end (radicle-end) the tap-root will develop.
The hypocotyl is the first internode of the sporo-
phyte. Where is the first node?

At the summit of the axis, above the cotyledons and
surrounded by them, observe the conical epicotyl.
It will develop into the second and subsequent
internodes. Explain the meaning of the term
epicotyl.

Construct three diagrams (X 5) showing (a) the
entire seed in longitudinal section (the embryo not
sectioned); (b) a cross-section of the seed, passing

PINUS LARICIO 175

<a

through the cotyledons and epicotyl; (c) a cross-
section of the seed passing through the hypocotyl.

Q. The “Germination”? of the Seed:
1. Observe specimens of seeds and seedlings represent-

ing various stages of germination.

. Describe (a) the changes that the various parts of

the seed undergo, in shape, size, and position; (0d)
the manner in which the seedling breaks through
the surface of the soil, and the advantage of this;
(c) the relative rate of early growth of the root and
shoot, and the significance of this; (d) color-change
in the cotyledons, its significance and whether or
not it can take place in darkness; (e) the fate of the
endosperm, and the evident rdle of this tissue; (/)
the manner of shedding the seed-coat; (g) the place
of development and character of any new organs.

. Compare the germination of a seed, with that of a

spore. What, in reality, is the germination of a
seed?

R. General Questions:

I.

To which alternating generation does the pine tree
belong?

. In a well-worded paragraph compare the relation

of gametophyte and sporophyte in the moss, fern,
Isoetes (or Selaginella), and Pinus.

. State the relative prominence of the sexual and

asexual generations in plant-groups of successively
higher organization.

. When the young sporophyte of Pznus begins growth

does it grow continuously to maturity, or does a
period of rest intervene? Compare it with Isoetes
or Selaginella in this respect.

. What changes would result in the formation of a

seed in Isoefes? What interferes with seed-forma-

176

MORPHOLOGY AND LIFE HISTORY

tion in that group? What changes would interfere
with seed-formation in Pinus?

. Define a seed. State several advantages to the

plant of the seed-habit.

. To what, in the fern, is the endosperm of the pine

seed homologous? To what in the moss? To
what, in Jsoetes or Selaginella, is the pollen-grain
homologous? To what in the fern? State, with
reasons, whether the leaves of the moss-plant are
homologous or analogous (or neither) to pine need-
les. In like manner, compare the organs of fixation
of the moss-plant, of the fern-plant, of the fern-
prothallus, and of the pine tree.

. Diagram the life cycle of Pinus as directed for

Isoetes (E, 3, p. 139), substituting pg(=pollen-
grain) for mi(=microspore), and es(=embryo-sac)
for me(=megaspore).

Trillium (WAKE-ROBIN)

A. Classification:
Division VII. Spermatophyta.
Subdivision B. Angiosperme (seeds enclosed in an
ovary).
Class I. Monocotyledonee (embryo with one
lateral cotyledon).
Order. Liliales (lily order).
Family. Liliacez (lily family).
Genus. Trillium (Latin tres, three).
Species. (e.g., sessile) (sessile flowered
_ trillium).!
B. Habitat: |
All species of Trillium occur in the woods in early
spring, and the genus has a geographic range extend-
ing from Nova Scotia westward to Manitoba, and
southward as far as Florida.

1 Any species of Trillium may be used, with minor changes in the direc-
tions; or, in fact, any other convenient genus of the Liliacee.

Note.—There are nearly 25,000 different. species of Monocotyledons.
The order Liliales, comprising about 5,000 species, contains the most
highly developed types. The lower Monocotyledons have naked flowers
(z.e., no sepals and petals), with the parts spirally arranged, as in the Gym-
nosperms. The higher ones have the parts of the flower arranged in con-
centric circles or cycles, five in number (pentacyclic), with usually three
members in each cycle. Our knowledge of the monocotyledons is not yet
adequate to make possible a satisfactory classification. ‘Taxonomists
differ in various points. The authors of Gray’s ““New Manual” (7th
Edition, 1908) subdivide the Liliacez into Tribes. Trillium is in the tribe,
Paridee. Britton (‘‘Manual of the Flora of the Northern States and
Canada”) and others, divide the Liliacez, as given in Gray, into four or
more families, the trilliums being in the Convallariacee, or Lily-of-the-
valley family.

ra ‘177

178

MORPHOLOGY AND LIFE HISTORY

C. The Shoot:
1. General.

(a)

Note its division into a main, thickened under-
ground part (rhizome), bearing numerous roots,
and a long slender aerial branch.

2. The Rhizome.

(a)

(0)
(c)

(d)

_ ©)

(f)

Describe its attitude (horizontal or erect), and
its general appearance. Compare Trillium
with the fern in this respect.

Are there branches, besides the aerial branch?
Note the thin membranous scales near the
apicalend. Record their number and position.
Carefully remove them with the scalpel. What
purpose may they serve? What is their
homology? Make a drawing of one (X 1).
Observe the nodes and internodes. What
do the nodes represent? Note the remnants of
the old scales at each node. Compare the
lengths of the internodes. What is the mean-
ing of this?

Describe any other scars on the rhizome. Are
they on nodes or internodes? What do they
represent?

State, with reasons for your opinion, the age
of your specimen.

3. The Aerial Branch.
(a) Describe its general appearance, shape, length

(0)

(compare several different specimens), color-
ation (color-pattern), and presence or absence
of branches.

At which end of the rhizome is it borne? Is
it a terminal or a lateral outgrowth? Is it an
axillary organ (7.e., borne in the axil of a leaf),
or not? Ona node or an internode?

»:

PERTEGIO MS 70) 179

a

_- (c) Make a drawing 20 mm. in diameter, showing

the distribution of the fibro-vascular bundles
as seen in cross-section.

(d) What does the branch bear at its summit?
Do you find any exceptions to this?

D. The Roots:
I

Describe their distribution on the root-stalk. Do
they occur on both nodes and internodes? State
the significance of the observed distribution.

2. Record the presence or absence of branching.
3. Compare the appearance of new roots with that

of older ones. On what part of the rhizome are
they borne?

. Describe the surface appearance of older roots.

e

Remove a root 3 to 4 cm. long, hold it by each end
and gently pull (not hard enough to break the
root). How does this affect the surface appear-
ance? How do you think the original feature
was produced? nies

With the scalpel cut a root squarely off near its
base and observe the cross-sectional view. Dis-
tinguish three tissue-systems: (a) the epidermis;
(b) the central cylinder; (c) between (a) and (8),
the cortex.

. Peel down a strip of the epidermis, and observe

whether the wrinkling is confined to it or not.

. Make a drawing, twice natural size, showing the

external features of the rhizome, together with a
portion of the aerial branch, and roots.

E. The Young Terminal Bud:'
1. Carefully remove the aerial branch and surrounding

scales and observe the terminal (apical) bud.

1On account of the large amount of material required, it is desirable
to make E and F class demonstrations by the instructor.

180 MORPHOLOGY AND LIFE HISTORY

2. Describe its color, shape, attitude, and the relation
between it and the base of the aerial branch. Draw
(2).

F, The Mature Terminal Bud:

1. Use material gathered in late autumn, and care-
fully dissect away the outer bud-scales. Identify
the parts found within.

2. Make careful drawings, and interpret the signifi-
cance of this observation.

G. The Foltage-leaves:

1. Describe the number, location, and arrangement
of the foliage-leaves. Are they petiolate or sessile?

2.. Observe:

(a) The coloration (described, for TJ. sessile, as
“‘blotched’’).

(b) The outline of the base, apex, and margin.

(c) The venation.

H. The Flower:

1. On what part of the shoot is it borne? Record
the presence or absence of a flower-stalk (peduncle).
Explain the significance of the specific name of
this species (T. sessile). Has the flower an odor?
If so, describe it.

2. Observe.

(a) The outer circle of parts (calyx) composed
of separate sepals. How many sepals are
there? Describe them as you did the leaves.
Note.—The term calyx comes from the Greek
word kalyx, a cover; the verb is kalypio, to
cover. What organ of the moss has its name
derived from the same source as calyx?

(b) The circle of parts (corolla) next within the
the calyx, composed of separate petals. How

TRILLIUM 181

many petals? Are they opposite or alternate

with the sepals? Record their color in fresh

(not preserved) specimens. Describe a petal

as you did the leaf and sepal.

(c) With the corolla, a circle of three microsporo-
phylls (stamens) each opposite a sepal. By
carefully bending back (but not removing)
the sepals and petals, observe whether or not
the other stamens are in the same circle as
the first ones, or in an inner (higher) circle.
Describe their location with reference to the
petals. Record the total number of stamens.
Note that each stamen is composed of:

(1) A stalk (filament), bearing at its tip,

(2) An anther, composed of marginal, linear
pollen-sacs (microsporangia), and connect-
ing tissue (the connective). Observe
whether the connective is prolonged be-
yond the sporangia. Note that the pollen-
sacs dehisce (open) on the inside (7.e., are
introrse). Describe their manner of de-
hiscence. |

(3) What do the pollen-sacs contain? De-

7 scribe its color.

(d) The central pistil composed of:

_ (1) The basal ovule case (ovary). How many

angles has it? How many lobes?

(2) The relatively long styles. How many?
Their inner surface is modified into

(3) A stigma. Describe this stigmatic surface
as seen both with unaided eye, and under
the low power. Usually numerous pollen-
grains may be seen adhering to it. What
process has therefore taken place?

182

MORPHOLOGY AND LIFE HISTORY

(4) The ovary is thus seen to be, not simple,
but compound. It is composed of three
carpels, bearing ovules. Since the ovules
are megasporangia, what is the homology
of the carpels? :

3. Look up in the dictionary, and record at this point,

the derivation of the names of the various parts of

a flower, studied above.

(a) It is important to note: (1) That the various
cycles are each composed of the same number
of parts; (2) that the parts of the various
cycles alternate with each other.

(b) When the other organs of a flower are inserted
below the pistil they are said to be hypogynous.
Is this true of Trillium?

(c) The more or less enlarged end of the stem (or,
in non-sessile forms, of the peduncle) on which
the organs of the flower are inserted, is the
receptacle.

. Make drawings as follows:

(1) A sepal. (X 1); a petal (X 1); a stamen (X 4)
(both dorsal and ventral views); an imagined
cross-section of an anther taken through the
middle (X 4); the pistil (X 4); an imagined
cross-section of the pistil (X 4).

_ (2) A ground-plan of the flower,.5 cm. in diameter,

first drawing five equidistant concentric cir-
cles, and filling in the. seas as directed by the
instructor. —
(3) An imaginary longitudinal section of the flower
(Kia). Co |

; Compare the ensue of the stamens with that of

the pistil. Carefully consider and state the rela-

< _ TRILLIUM 183

tive probabilities of self-pollination and cross-
pollination.

Non-sexual Reproduction:

I.

Non-sexual reproduction in Trillium is confined to
the growth of the persistent, underground rhizome.
This organ is thick and fleshy, serving for the storage
of food.

. Note the ridges and scars on its surface.
. What develops each year at the growing end?

4. A plant that is continued indefinitely, from year to

year, by means of a persistent root or stem, or both,
is a perennial; one that persists for two years only,
setting seed and dying at the end of the second sea-
son is a biennial, plants that set seed and perish at
the end of one season are annuals. Name illus-
trations of each of these three classes of plants.

Sexual Reproduction:
1. Microspores.

(a) Mount in clearing fluid (or water) on a slide
some of the pollen from an anther.

(b) Observe (first under low, then under high power)
the individual pollen-grains. Describe their
color and shape, and note the network of
ridges on the surface of each.

(c) By carefully focusing on individual grains there
may readily be detected in some of them one
nucleus, in others, two. Those in. the one-
nucleate stage are mature microspores.

. Male gametophyte. The division of the microspore-

nucleus is the first stage in the germination of the
spore. To what do microspores, when they ger-
minate, give rise? What, therefore, is the homol-
ogy of the bi-nucleate pollen-grain?

(a) The larger nucleus is the tube-nucleus, and

184

(0)

(<)

(d)

MORPHOLOGY AND LIFE HISTORY

presides over the development of the pollen-
tube. The smaller is the generative nucleus.
Make drawings, 2 cm. in diameter, of a micro-
spore and of a male gametophyte, labeling all ~
parts. :

After pollination, the formation of the pollen-
tube takes place. This is usually spoken of as
the “germination of the pollen-grain.”
The tube emerges through one of several weak
places in the wall of the grain, grows down
through the tissues of the style, digesting its
channel as it proceeds, or, in some species, fol-
lowing a canal already formed through the
style.

The generative cell (generative nucleus with its
own protoplasm) follows down the pollen-tube,
and divides into two non-motile sperm cells.
In some species, e.g., Sambucus, (elder), this
division occurs before the tube develops. The
pollen-tube passes through the micropyle, and
discharges the sperm-cells near the egg. One
of the sperm-nuclei fuses with the egg-nucleus,
thus effecting fertilization.

For convenience in handling material the
observation of the finer structure of the anther
and pollen will be deferred until after the
microscopic study of the ovary and ovules (3,
below).

3. Megasporopkylls and Megasporangia. Witha sharp

scalpel or razor make a median cross-section of the
ovary and observe: —

(a) Its outline. Each of the lobes represents the

section of one of the carpels (megasporophylls),

< | TRILLIUM 185

which together compose the tri-carpellate,
compound ovary.

(b) The number of compartments (‘‘cells”). Do
the septe (walls) that separate them meet in
the center? Compare the number of cells with
the number of carpels.

(c) The placente (sing., placenta), or surfaces of the
sept to which are attached.

(d) The ovules. Do the ovules lie in a vertical or
in a horizontal plane? Are they few or numer-
ous? In Trilliwm the ovules are borne on
parietal placentz.

(e) The funiculus (stalk) by which the ovule is
attached to the placenta. Observe (using
magnifier) that the ovules have curved through
180°, bringing their apical (micropylar) ends to
their base or point of attachment to the fun-
iculus. They are thus anatropous ovules.

(f) Make a drawing, 4 cm. in diameter, showing
the ovary (and ovules) as seen in cross-section.

4. Histology of the anther. Development of the pollen.

(a) Use prepared slides. The sections on these
slides are triple-stained with safranin, gentian-
violet, and orange. By this means the various
parts of the cell are given different colors, the
cytoplasm a grayish tinge, the- nucleolus and
chromatin threads in the nucleus red, starch
grains a deep blue.

Using slides showing the microspore- -mother-cell
stage of Lilium canadense, or other convenient
plant,

(6) Observe the outline of the section as a whole.

(c) The central portion is the connective, contain-

ing ;a.vascular bundle. ,

186

(d)

(e)
(7)

MORPHOLOGY AND LIFE HISTORY

Opposite the connective may often be seen a
cross-section of the filament, with its vascular
bundle.

The numerous, conspicuous blue-stained bodies
are Starch grains.

Note the epidermis, one cell thick. Does it
cover the entire surface? Does it contain

_ starch grains? Find numerous stomata, each

(g)

(z)

6

2)
(2)

with a small, underlying air-space.

At each side of the section will be seen two
sporangia, containing the large microspore-
mother-cells (pollen-mother-cells), with promi-
nent nucleus. Observe the network of chrom-
atin within each of these nuclei. The mother-
cells adhere more or less closely, depending
upon age. Their final separation from other
cells, and from each other, marks the first
separation of the gametophytic from the
sporophytic generation. The mature micro-
spore-mother-cell is the first stage in the develop-
ment of the male gametophyte (cf. 6 (qa).
below, p. 188).

Around the mother-cells note a layer of elong-
ate cells, radially arranged, and with nuclei
more or less disorganized. These are the
tapetal-cells. Together they form the tapetum.
Between the tapetum and epidermis lie the
middle layers of cells forming the wall of the
sporangium. How many cells thick is it?

‘Make a drawing 8 cm. in longest measure,

showing all features observed under 4, (a)—(&).
By two successive divisions each pollen-mother-
cell forms four microspores (young pollen-
grains). They thus arise in tetrads.

TRILLIUM 187

Using slides showing pollen-grains, observe:

(m) The more advanced disorganization of the

(n)

(0)

tapetal-cells, including the breaking down of
their cell-walls, and the fragmentation of their
nuclei into two or more. These cells serve
to nourish the spore-mother-cells.

The microspores. Do they lie free or con-
nected? Describe their shape, surface-features,
and number of nuclei.

State again the first stage in the germination
of the microspore. What is the resulting
structure? What is its homology?

. Megasporangia; megas pore-mother-cell.
Using prepared slides showing the megaspore-
mother-cell, observe:

(@)
(0)

(c)
(d)

a
(g)

The outline of the ovary as seen in cross-section.
The presence or absence of an epidermis;
of stomata.

The “‘cells” of the ovary, each containing, in
the section,

Two young ovules (megasporangia). Are the
ovules straight or curved?

At this stage the tissue of the ovule is chiefly
nucellus, but soon there develops at the base
of the ovule, outside of the nucellus,

The inner integument, which grows up around
the nucellus, leaving at the summit only a
small passage, -

The micropyle. Outside the inner integument
there usually develops

An outer integument. In anatropous ovules

the development of the outer integument
wholly or partially fails on the side where the
-funiculus adheres to the ovule. At the summit

188

(h)

(7)

MORPHOLOGY AND LIFE HISTORY

of the nucellus (apex of the ovule) is seen the
large

megaspore-mother-cell (embryo-sac-mother-
cell), with very prominent nucleus and
nucleolus. ;

Make a diagram of all that you have observed
under 5, (a)—(h), filling in the details for one
ovule.

6. Development of the Megaspores. |
(a) Like the microspore-mother-cell, the megaspore-

mother-cell of Trillium divides twice, giving
rise to four megaspores (tetrads), but only
one of these megaspores develops a gametophyte.
This spore enlarges, and by three successive
divisions gives rise to an eight-nucleate female
gametophyte, the embryo-sac. Three of these
nuclei organize antipodal cells at the basal
end of the embryo-sac, and three of them

- organize cells at the micropylar end. One of

-Q)

the latter is the egg, the other two thesynergids.
The two remaining nuclei fuse near the center
of the embryo-sac, forming the endosperm-
nucleus (sometimes called definitive nucleus),
but the endosperm does not develop until
after the fertilization of the egg.

Unlike the microspores, the megaspores, in
angiosperms, never become free, independent
cells, but always retain an intimate physiolog-
ical connection with the sporophyte of the
next preceding generation (¢f.. 4(g), above).

7. The Embryo-sac.

(a)

Using prepared. slides, study. the embryo-sac
in its two- to-eight-celled stages, identifying
the cells-‘mentioned in 6 above. Draw.

TRILLIUM 189

a

K. Development of the Embryo:

1. After fertilization (J, 2, (c), p. 184), the odsperm.
develops the embryo-sporophyte, and while this
is in progress the endosperm-nucleus, by successive
divisions, develops into endosperm which surrounds
the embryo, and: will serve to nourish it when it
re-awakens, at the “germination” of the seed.

L. Fruit and Seed:

1. Meanwhile, as a result of fertilization, the ovary
resumes growth, and develops into a fruit (ripened
ovary), while the ovule enlarges and undergoes
numerous changes, ripening into a seed.

2. In a concisely worded paragraph, tell what a seed
is, stating to which of the alternating generations

the seed-coats, endosperm, and embryo belong.
M. Nuirition: ;

1. Discuss the nutrition of both the gametophyte
and sporophyte of Trillium, as suggested above
(L, 1-4, p. 160) for Zamia.

N. Tabular Review:

Fill in the tables below (pp. 190 and 101), by placing

an x in the proper space, then state, in a well-

worded paragraph for each table, what may be
learned by an inspection of it.

MORPHOLOGY AND LIFE HISTORY

190

peonpar

suorpouny

uo1ze3sedoid
[enxose jo . aiqeded

sno1oaiqd

snolocouo yy

Oo o1isered AOU M
a3Aydoiods 344

[IOS 94} wI0s3

BJVUIOYS SEPT
sosisayqzUAsoyOYd

solidsay

TABLE III.—CoMPARISON OF GAMETOPHYTES

Plant

SMOIZOUNY dAI}CIOS9/A

AIze{a39A YOq sey

~_ a3A4ydoiods ay} —

O onisered Apjieg

queulysiinou soyxey

ee) cage ea
La] ft eed F ie be oat f
: ones
Leal il) ry (Oe a Ol Ue AO) Oy 8 Se Be
H SRS aude. hele
fe) a disy ee as
Leal CY ee ee ce! We |! ere
o peed ae 2
20 ee
a te eas
PET cba race te
Tce ee ee
+ Moe ee
~ Bap eet
ear
me Te
fog Gg dg 2 ct:
ot ot Sa
2 peer ety es OED Gets I
i I ea ee
& O 8 ad Bid of.
SEES3 8235 25
: Ao SD oe
2G a eo ow ee

TABLE IV.—COMPARISON OF SPOROPHYTES

MORPHOLOGY AND LIFE HISTORY

A1I®AO ae ent
@ UI pesojoUr Sspeeg|; #4 O19

eecervloeven
ceeleceo
ecveeetooee

spaes seonpolg

.
°
°
°
.
°
°
°
e
°

spoes Ou soonpolg
sno1odso1940y7

snoiodsouroyy
azyeurmopeid
SUOTZOUN} DAT}eIODOA

ayeurwmopeid
WOTZOUNJaAryoOnNpoIdey

uorzesedo1d
enxose jo oajqeded

ayAydojoures
Oo onisered AJOUM

a,Aydozoutes
Oo onisered § ApqIeg

ayAydoyaures jo
uspusdepul 4sIxe UBD

sansst} BulyoNpuod sePy

10S 9y} WoOsJ
uswuysIinou soyHe

eyeul0}s Sey

y[Aydosoyyo sey
sotidsey

Ajtinzeur jo
3e4S podojaAap AI YsIY
Jour e@:° 03 dsTUOAIG
-Uly Ue YSnoly, sesseq

a3e}S OIUO
-Aiquie A{[eizUesse ue
uofeq sossed JOAaN

e
°
eco
2
°

s ade SE hee
<q Saas Series Pld ey 8
& Pe aes * g rey Aa
Ay sanseeat : 6) 08
-8@ghdea : :
ea 3g a °
sie 0723 0 Bete
goHSPad8a
om Q,8 Acs e
oN 8 Sogo WL cs
+» 30 o §
Seas aegdo&
BINNAQARAN

eeoe eee

Trillium......

IgI

7, as .
= BE

st . ite A

Gey

Wwrsan