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TEACHERS'HEADQUARTERS
From the collection of the
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GUIDE
STUDY OF COMMON PLANTS
AN INTRODUCTION TO BOTANY
BY
VOLNEY M. SPALDING
PROFESSOR OF BOTANY IN THE tTNivERSiTY OF MICHIGAN
BOSTON, U.S.A.
D. C. HEATH & CO., PUBLISHEES
1894
K
COPYRIGHT, 1893,
BY VOLNEY M. SPALDING.
Typography by J. S. Gushing & Co.
Presswork by S. J. Parkhill & Co,
PREFACE.
THESE exercises have been prepared for classes in high
schools and other institutions of similar grade, and are
intended to indicate, in a general way, the nature of the
work that in the judgment of the writer should be under-
taken with young people who are just beginning the sys-
tematic study of common forms of plant life. They were
suggested by frequent inquiries of teachers regarding the
preparation in botany now required for admission to the
University of Michigan.
No originality is claimed for the subject-matter or its
treatment, although much time has been spent in the
effort to develop a natural and practicable method of
approaching the study of living things. While the study
of relationship holds the first place, the attention of the
pupil is directed at every step to the physiological signifi-
cance of observed facts ; and although this will hardly be
approved by those who attempt to separate sharply the
domain of morphology from that of physiology, it has
seemed to the writer better to follow Nature than be
cramped by such artificial barriers. Some of the exer-
cises will perhaps appear too simple -and others too diffi-
cult, but a judicious selection on the part of the teacher
will do much to correct this.
As to the ground that ought to be covered in such a
course, and the proper sequence of subjects, there is natu-
iy PREFACE.
rally great difference of opinion among practical teachers.
Theoretically it would seem best to begin with the lowest
forms of plants, and work up to the higher; but after
careful consideration, and in view of the actual state of
things in most of our preparatory schools, a different plan
has been adopted.
It is hoped that in spite of mistakes and imperfections,
sure to be brought to light if the book is used, it may never-
theless prove serviceable to a rapidly increasing number
of teachers who are desirous of improving existing methods
of instruction. To Dr. Erwin F. Smith of Washington,
D.C., and Miss Effie A. Southworth of Barnard College,
who have kindly read the proofs throughout ; to Mr.
W. H. Rush of the University of Michigan, who has criti-
cally reviewed and tested the practical directions; and
to others who have aided in various ways, the sincere
thanks of the writer are due.
CONTENTS.
PAgE
To THE STUDENT .......... ix
To THE TEACHER .......... xii
WORKS OF REFERENCE ......... xv
LABORATORY AND PERMANENT OUTFIT ...... xix
ORGANS OF FLOWERING PLANTS.
I. SEEDS ........... 1
II. GROWTH OF PLANTS FROM THE SEED. .... 20
III. ROOT 29
IV. STEM 38
V. LEAF 57
VI. FLOWER 74
VII. FRUITS 88
NATURAL GROUPS OF PLANTS.1
VIII. ALG^E . . . . . . . . . . 96
IX. MUSCINE^E 105
X. FILICINE^E 114
XI. EQUISETINE^E 123
XII. LYCOPODINE^E 127
1 Groups above families have been placed in boldface type without attempting their
coordination.
CONTENTS.
GYMNOSPERMS.
PAGE
XIII. CONIFERS . 132
MONOCOTYLEDONS.
XIV. GRAMINE^E . . .137
XV. CYPERACE^E. ........ 141
• XVI. ARACE.E 144
XVII. LILIACE^E . . 148
XVIII. AMARYLLIDACE.E ....... 150
XIX. IRIDACE*: 152
XX. ORCHIDACE^E ........ 155
DICOTYLEDONS.
XXI. SALICACE^E 161
XXII. RANUNCULACE^E 164
XXIII. CRUCIFER.E 171
XXIV. ROSACES 174
XXV. LEGUMINOS^E ........ 177
XXVI. GERANIACE^E 181
XXVII. EUPHORBIACE^: 186
XXVIII. ACERACE^ 190
XXIX. MALVACE.E 193
XXX. VIOLACE*: ... 196
XXXI. ONAGRACE^E 200
XXXII. UMBELLIFER.E 203
XXXIII. ASCLEPIADACE^E ... .... 208
XXXIV. BORRAGINACE^: 212
XXXV. LABIATE 215
CONTENTS. Vll
PAGE
XXXVI. SOLANACE^ 219
XXXVII. SCROPHULARIACE^E . . . ^ . . . . 223
XXXVIII. CAPRIFOLIACE*: ........ 228
XXXIX. CUCURBITACE^E 231
XL. COMPOSITE . 235
TO THE STUDENT.
You are beginning the* study of living things, and it is
very important that you should begin in the right way.
These practical exercises are intended to help you, but not
to do the work for you. Many of the exercises will seem
very simple, but if you actually do what is called for, it
will be plain why so much stress is laid on knowledge
gained by direct personal observation and experiment.1
There are a few things that you ought to consider at the
outset.
1. First of all, it is essential that you should learn to
see things just as they are, and to report exactly what
you have seen. Agassiz used to say to his students:
"Study to know what is; be courageous enough to say
4 1 do not know.' " Tyndall said to the teachers at South
Kensington : " In every one of your experiments endeavor
to feel the responsibility of a moral agent. ... If you
wish to become acquainted with the truth of Nature, you
must from the first resolve to deal with her sincerely."
Darwin in his autobiography2 writes: " I had during many
1 " You wish, for example, to get a knowledge of magnetism ; well, pro-
vide yourself with a good book on the subject, if you can, but do not be
content with what the book tells you ; do not be satisfied with its
descriptive woodcuts ; see the actual thing yourself. Half of our book-
writers describe experiments which they never made." — TYNDALL, Frag-
ments of Science.
2 Life and Letters, p. 71.
ix
X TO THE STUDENT.
years followed a golden rule, namely, that whenever a
published fact, a new observation or thought, came across
me, which was opposed to my general results, to make a
memorandum of it without fail and at once, for I had
found by experience that such facts and thoughts were far
more apt to escape from the memory than favorable ones."
2. When you have seen a thing clearly, be sure to express
your conception, whether by drawing, or written descrip-
tion, or both, as accurately as possible. Learn to use
scientific language with precision. Write out your obser-
vations in full, in the best English at your command.
Avoid abbreviations and every other device for saving
time. Make your drawings so that an engraver could
copy them. Do not hesitate to do your work all over
again, if it can be improved, as it probably can be, and do
not leave a thing until you have not only a complete obser-
vation, but a complete expression of it.
3. Do not be hasty in drawing conclusions. Make a
constant practice of comparing the object you are studying
with others of the same kind. Note differences and resem-
blances. Learn by the actual process what it is to acquire
a general conception. " Honesty in science means, first,
facts well proved, and then conclusions slowly and pain-
fully deduced from facts well proved."1 In all your
work stop and think. The mere accumulation of facts,
if nothing is done with them, is of little consequence.
Constantly ask the question, what does this fact mean ?
You may or may not be able to answer the question, but
that is no reason for not raising it.
4. Cultivate self-reliance, but not self-sufficiency. Study
1 J. P. Lesley, Presidential Address, Am. Assn. for the Advancement
of Science, 1885.
TO THE STUDENT. XI
things themselves rather than book descriptions of them,
but habitually use the books you are referred to, compar-
ing point by point your own observations with what the
authors have to say. The writers cited may or may not
be right ; they are more likely to be than you are ; but
both of you may be wrong. The best way is to observe for
yourself, then consult the books ; then observe again, and
continue your observations and comparisons until the exact
truth is ascertained. This is the way investigations are
conducted, and you are learning how to investigate.
5. This leads to a word on the use of books. Make it
a regular practice to look up the references that are given
with the exercises. By doing this you will not only
become acquainted with some of the most valuable botan-
ical literature, but, what is more important, you will come,
in some measure, to understand the habits and methods of
the great workers in science, and will, perhaps insensibly to
yourself, catch something of their spirit, and learn to
work as they did, honestly, accurately, and " with infinite
patience."
One of the greatest investigators who has ever lived
wrote a few years ago : " Whenever I have found out that
I have blundered, or that my work has been imperfect,
and when I have been contemptuously criticised, and even
when I have been over-praised, so that I have felt morti-
fied, it has been my greatest comfort to say hundreds of
times to myself that ' I have worked as hard and as well
as I could, and no man can do more than this.' " 1
1 Charles Darwin, Life and Letters, p. 72.
TO THE TEACHER.
MATERIAL AND METHODS.
IN order to use these exercises successfully it will be
necessary to adopt the laboratory, as distinguished from
the text-book, method of instruction. The practice, still
too common, of using ordinary recitation seats and benches
for work of this kind is extremely unsatisfactory, and
ought to be abandoned. The best arrangement is to have
places assigned at long tables — one table in front of each
window, so that every student can have a full amount of
light. North, east, and west windows are preferable, those
on the north side being the best. In every case the pupil
is to be provided with the material called for, and this
should be typical of its kind and sufficient in quantity.
In a large proportion of the exercises the plants needed
are common everywhere and easily obtained. When it is
impossible to procure them the exercise is to be omitted.
It has no significance whatever unless the thing talked
about is actually present to the eye. It will generally be
found better to secure an appropriation of a few dollars
and employ some one regularly to furnish a supply of
material than to depend on what the teacher and members
of the class can gather. In any case the things to be
studied must be systematically provided. They cost far
less, but are just as essential as the reagents and apparatus
in a chemical or physical laboratory.
TO THE TEACHER. Xlll
Too much emphasis cannot be laid on the importance
of securing at the outset a fairly complete equipment.
The necessity of following the laboratory method in science
teaching is now so universally recognized that it is to be
hoped that boards of education will generally adopt the
better way and cheerfully pay for it. Having once secured
the necessary tables, instruments, and books, the expense
from year to year is extremely small in comparison with
the result aimed at, viz. a discipline that can be attained in
no other ivay.
The use of the microscope, methods of sectioning,
mounting microscopic objects, drawing, and other prac-
tical operations of the laboratory are best learned of the
living teacher. Useful suggestions, however, will be found
in the excellent handbooks of Strasburger, Arthur, Barnes,
and Coulter, and other laboratory manuals.
DISPOSITION OF TIME.
When practicable, it is much more advantageous to
arrange the time given to laboratory work so that each
student can work two consecutive hours for a certain num-
ber of days each week. When this cannot be done with-
out seriously interfering with the school programme, the
following plan is suggested: Give four hours each week
to practical exercises, requiring each member of the class
to work independently in his own place, precisely as he
would at a table in a chemical laboratory, the teacher pass-
ing from table to table, giving personal help as it is needed,
and from time to time giving notes and directions to the
class as a whole. The remaining hour, say on Friday or
Monday, or sometimes both, may be used for recitations,
reports on laboratory work, and the dictation of notes and
TO THE TEACHER.
references. Exercises to be conducted out of school hours
may be assigned at the discretion of the teacher, but
generally it will be found that the best work is done in
the laboratory under his personal direction.
In the majority of preparatory schools half a year is
given to botany. It is very desirable that the time should
be extended, but until this is done it is recommended
that the exercises be followed substantially as here out-
lined, with the omission of a part, or possibly the whole, of
the microscopic work. If the latter is undertaken, and a
reasonable amount of time is given to the study of different
families of plants in the spring, a full year will be needed.
WORKS OF REFERENCE.
IN connection with the exercises, frequent references
are given. In a few cases books of a more or less popular
character are mentioned, and some of the most important
works in French and German are referred to, inasmuch
as they are well-nigh indispensable to the teacher. In
general, the works named are easily obtained, and ought to
have a place in any respectable school library. Several
copies of the books in constant use should be placed on
tables in the laboratory, where they can be consulted with-
out loss of time, the students being given to understand
that they are expected to look up references as habitually
and critically as they would- if reading a classical author.
One or more of the best periodicals may properly be
included in the essentials of the laboratory outfit. The
following list, by no means complete, includes some of the
most generally useful botanical works.
LABORATORY MANUALS.
Arthur, Barnes, and Coulter, Plant Dissection. Henry Holt & Co., New
York, 1886.
Bower and Vines, Practical Botany, Parts I. and II. Macmillan & Co.,
London, 1885 and 1887.
Clark, Practical Methods in Microscopy. D. C. Heath & Co., Boston, 1893.
Strasburger and Hillhouse, Practical Botany. Macmillan & Co., New
York. 1889.
These manuals are of the utmost value as laboratory guides.
The first is the simplest, and, on the whole, most suitable for
Xvi WORKS OF REFERENCE.
beginners. The third contains the latest and most approved
methods of microscopical manipulation. The last is most com-
plete, and gives the modern methods of work jvith such clearness
and detail as to render it indispensable in every botanical labo-
ratory. The original work of which it is a translation [Stras-
burger, Das kleine botanische Praktikum. Fischer, Jena] will be
preferred by those who read German.
STRUCTURAL AND PHYSIOLOGICAL.
Gray, Structural Botany (sixth edition). Ivison, Blakeman & Co., New
York, 1879.
Goodale, Physiological Botany. Ivison, Blakeman & Co., New York,
1885.
Bessey, Botany. Henry Holt & Co., New York, 1888.
DeBary, Comparative Anatomy of the Phanerogams and Ferns. Oxford,
Clarendon Press, 1884.
Vines, Physiology of Plants. Cambridge, University Press, 1886.
Sachs, The Physiology of Plants, Trans, by H. Marshall Ward. Oxford,
Clarendon Press. Macmillan & Co., 1887.
Haberlandt, Physiologische PJlanzenanatomie. Engelmann, Leipzig,
1884.
Frank, Lehrbuch der Pflanzenphysioloyie. Parey, Berlin, 1890.
Zimmermann, Die Morphologic und Physiologie der Pflanzenzelle .
Trewendt, Breslau, 1887.
Detmer, Das pjlanzenphysiologische Praktikum. Fischer, Jena, 1888.
Detmer, Manuel technique de Physiologie vegetale. C. Reinwald, Paris,
1890. Translation of the last-named work revised and extended
by the author.
Bessey 's Botany is the least expensive book that covers the
ground at all satisfactorily. With Gray's Structural and Good-
ale's Physiological Botany one is better equipped for work, inas-
much as the whole general subject of organography and physiology
is ably and clearly presented in them. Sachs' Lectures on the
Physiology of Plants is indispensable.
MORPHOLOGICAL AND SYSTEMATIC.
Goebel, Outlines of Classification and Special Morphology of Plants.
Oxford, Clarendon Press, 1887.
Luerssen, Handbuch der Systematischen Botanik. Haessel, Leipzig, 1879.
WORKS OF REFERENCE. XVII
Eichler, Bluthendiagramme. Engelmann, Leipzig, 1875.
Engler und Frantl, Die naturlichen Pflanzenfamilien. Engelmann,
Leipzig.
All of these are of great value, especially the rather expensive
work of Engler and Prantl, now in course of publication.
FLORAS.
Gray, Manual of Botany (sixth edition). Ivison, Blakeman & Co.,
New York.
Chapman, Flora of the Southern United States (second edition). Ivi-
son, Blakeman & Co., 1883.
Coulter, Manual of the Botany of the Rocky Mountain Region. Ivison,
Blakeman & Co., 1885.
Coulter, Manual of the Phanerogams and Pteridophytes of Western
Texas. U. S. Dept. Agric., 1892.
Gray, Synoptical Flora of North America. (In progress.)
Gray's Manual is commonly bound with the " Lessons " in one
volume, but may be had separate in convenient form for the
pocket. Dr. Gray's final revision of the "Lessons" has been pub-
lished under the title, Elements of Botany. Ivison, Blakeman &
Co., 1887.
CRYPTOGAMIC BOTANY.
Eaton, Ferns of North America. Cassino, Boston, 1879.
Lesquereux and James, Mosses of North America. Cassino, Boston,
1884.
Farlow, Marine Algce of New England. U. S. Fish Commission,
Washington, 1881.
Tuckerman, North American Lichens. Cassino, Boston, 1882.
DeBary, Comparative Morphology and Biology of the Fungi, Mycetozoa,
and Bacteria. Oxford, Clarendon Press, 1887.
v. Tavel, Vergleichende Morphologie der Pilze. Fischer, Jena, 1892.
Bennett and Murray, Handbook of Cryptogamic Botany. Longmans,
Green & Co., London and New York, 1889.
Plowright, British Uredinece and Ustilaginece. Kegan Paul, Trench &
Co., London, 1889.
Underwood, Our Native Ferns and their Allies. Bloomington, 111.,
1882.
XV111 WORKS OF REFERENCE.
The list of works on Cryptogamic Botany might be greatly
extended. Numerous references to the literature of the algae
will be found in Farlow's work mentioned above, and to that of
the fungi in DeBary's treatise. For other references consult Ben-
nett and Murray's Handbook.
GENERAL.
Miiller, The Fertilization of Flowers. Macmillan & Co., London, 1883.
DeCandolle, Origin of Cultivated Plants. Appleton & Co., New York,
1885.
Kerner, Flowers and their Unbidden Guests. Paul & Co., London, 1878.
Darwin, Insectivorous Plants, and other works. Appleton & Co., New
York.
Lubbock, Seedlings. Appleton & Co., New York, 1892.
Lubbock, Flowers, Fruits, and Leaves. Macmillan & Co., London,
1886.
Goodale, Wild Flowers of America. Cassino, Boston, 1882.
Sachs, History of Botany. Macmillan & Co., 1890.
Lindley and Moore, The Treasury of Botany. Longmans, London,
1874.
Kerner von Marilaun, Pflanzenleben, 2 vols. Bibliographisches Insti-
tut, Leipzig and Vienna, 1891.
M tiller's work on the Fertilization of Flowers gives references
to the immense and increasing body of literature on this subject.
Kerner's work is out of print, but may occasionally be picked up,
and is a most charming little book. All of Darwin's books
should have a place in such a list.
CURRENT LITERATURE.
The Botanical Gazette. Lake Forest, 111., $2.50 per year.
Bulletin of the Torrey Botanical Club. New York, $2.00 per year.
Annals of Botany. Oxford, Clarendon Press.
Botanisches Centralblatt. Gotthelft, Cassel.
The Botanical Gazette and Torrey Bulletin are well-known Ameri-
can journals. The Annals of Botany is a new periodical of a
high order, with original monographs, criticisms of current lit-
erature, etc. The Botanisches Centralblatt is indispensable in
botanical research.
LABORATORY AND PERMANENT OUTFIT.
1. The laboratory should be a large room, properly
ventilated, with as many windows as practicable, and used
exclusively as a laboratory. An upper room is preferable
to a lower one, since the air is clearer and there is less
liability to disturbance from passers-by.
2. The laboratory tables should be plain and solid,
oiled, but not painted or varnished, and large enough to
give each student all the space he requires without crowd-
ing. Drawers should be placed in the tables, or in a
separate case, in which the students' outfit may be kept.
3. Receptacles for waste materials, conveniently
placed and frequently emptied, and plenty of clean
water are indispensable.
4. A pair of balances, such as are employed by drug-
gists for accurate weighing, will be required.
5. Microscopes. For the compound microscope, the
so-called continental stand is preferable, on account of its
simplicity, firmness, and convenient size. Two good objec-
tives, I and J inch, or their equivalent, and two eye-pieces
are necessary. Such an instrument may be purchased of
a reliable dealer for about §30. It will hardly be practi-
cable to equip the laboratory with lower-priced ones that
will prove satisfactory.
Dissecting microscopes of simple construction are needed,
XX LABORATORY AND PERMANENT OUTFIT.
but a good hand-lens, properly mounted, will answer the
same purpose. See Arthur, Barnes, and Coulter, Plant
Dissection, p. 2.
6. Glassware and miscellaneous articles. A stock of
common plates and bowls, beakers, glass tubing, bell-jars,
test-tubes, metric rules, etc., will be required, but are best
purchased as needed, at the discretion of the teacher.
REAGENTS.
Of the reagents most employed in botanical work the
following are required : 1 -
7. Alcohol. For preserving plant-tissues, except in
cases involving the most delicate operations, three grades
of alcohol are all that will be needed. The lowest grade
(between 45 and §0 per cent) is composed of equal parts
of alcohol of commerce and distilled water. The inter-
mediate grade (between 70 and 75 per cent) is prepared
by adding 25 parts of distilled water to 75 parts of
commercial alcohol. The highest grade is the alcohol of
commerce (approximately 95 per cent).
Parts of plants to be preserved are allowed to remain
24 hours in the lowest grade of alcohol, then for the same
length of time in alcohol of intermediate strength, and
finally are placed in 95 per cent alcohol, in which they
may be kept indefinitely. It is necessary to guard against
attempting to preserve too much material in a given
quantity of alcohol, as decomposition is likely to take
place.
1 Reference may be made to various works in which reagents and
methods are discussed at much greater length. Among these are Stras-
burger and Hillhouse, Practical Botany ; Behrens, Guide to the Use of
the Microscope in Botany ; Zimmermann, Die botanische Mikrotechnik.
LABORATORY AND PERMANENT OUTFIT. XXI
8. Absolute alcohol. For finer histological work abso-
lute alcohol and a larger number of grades of commercial
alcohol more carefully prepared are necessary.
9. Iodine solution. Distilled water 10 c.c., potassic
iodide 1 gm., iodine 0.25 gm. Dilute to 250 c.c.
10. Glycerine. Pure glycerine is employed in some
cases, but equal parts of glycerine and distilled water will
generally be found most serviceable.
11. Scnulze's solution. This may be prepared accord-
ing to the rule given in Strasburger's Praktikum, but it
will be found more convenient to employ Griibler's chlor-
iodide of zinc, which may be obtained of Eimer and
Amend, New York.
12. Potash solution. One part of solid caustic potash
dissolved in 20 parts of distilled water. This reagent
attacks glass, and care should be taken to prevent its
getting on the objectives.
13. Glacial acetic acid.
14. Sulphuric acid.
15. Hydrochloric acid.
16. Picric acid.
17. Phlorog-lucin. One per cent alcoholic or watery
solution. Employed with hydrochloric acid as a test
for lignin.
18. Picric aniline blue. Add picric acid to distilled
water until a saturated solution is obtained. To this add
slowly a saturated watery solution of aniline blue until it
is of a deep blue-grSen color.
XXli LABORATORY AND PERMANENT OUTFIT.
19. Acetic methyl green. To a 2 per cent solution
of glacial acetic acid add methyl green until the solution
is deeply colored.
STUDENT'S OUTFIT.
Each pupil should be provided with the following
articles : 1 —
20. A Coddington lens or achromatic triplet. Either
of these will serve a good purpose. The cheap lenses,
mounted in horn, and sold for a dollar or less, are of
little use. A good Coddington lens may be purchased
of Bausch and Lomb, Rochester, N.Y., for $2.50, and an
excellent achromatic triplet of James W. Queen & Co.,
Philadelphia, for 14.75.
21. A good pocket knife, kept sharp.
22. Razor of good quality and medium size, hollow
ground. The Torrey razor, manufactured at Worcester,
Mass., is recommended.
23. A pair of fine forceps.
24. Slides and thin glass covers for mounting micro-
scopic objects. The glass covers should be of medium
thickness, and not less than f of an inch in diameter.
25. Needles mounted in handles.
26. Camel's-hair brushes of medium size.
27. Note-book and drawing paper. The latter should
be unruled, rather heavy, of good quality, and cut to a
convenient size for drawings.
1 In some cases it may be practicable, in order to save expense, for two
to use the same outfit ; but the practice is not to be commended, except
in case of necessity.
LABORATORY AND PERMANENT OUTFIT. XX111
28. Drawing- pencils and eraser. The pencils should
be of at least two grades, medium and hard.
If the student pays a laboratory fee, most of the
articles named above should be furnished by the school
board ; if no fee is charged, he may reasonably be required
to purchase for himself those that are liable to loss or
deterioration through use.
STUDY OF COMMON PLANTS.
I. SEEDS.1
MATERIAL REQUIRED.
Common white beans. Other varieties, such as " butter beans," etc.
Peas, oats, wheat, Indian corn, — several varieties of the latter.
Castor oil seeds.
Seeds of white pine, Norway spruce, and other conifers.
Commercial " nuts," such as chestnut, peanut, filbert, almond, Brazil
nut, and English walnut.
Seeds of coffee, date, flax, sunflower, tomato.
As many kinds as possible of seeds*with winged or hooked appendages
or other special arrangements for dissemination.
Seeds of squash, pumpkin, watermelon, muskmelon, cucumber, gourd,
and similar collections from other important families.
COMMON BEAN. Phaseolus vulgaris, Savi.
I. Compare a number of white beans, and see if they are
all alike. Select a good specimen. Observe and describe
1. The shape, surface, and color.
2. Surface markings :
a. The scar, hilum,2 marking the place where the
seed was attached.
1 General references: Gray, Structural . Botany , pp. 305-314; Stras-
burger, Practical Botany, Chaps. I and II ; Sachs, Physiology of Plants;
Haberlandt, Physiologische Pfl,anzenanatomie, pp. 277-293.
2 If any of the terms are unfamiliar and are not sufficiently explained
in the text, consult Webster's International Dictionary.
1
2. V : ; ; STUDY OF COMMON PLANTS.
'i 2>^ Near the hilum a minute orifice, micropyle, easily
seen under a lens.
c. The chalaza, the part where the seed coats blend
with each other and nutriment enters the grow-
ing seed. In this case the chalaza is located
externally by a small protuberance near the
hilum, on the opposite side from the micropyle.
II. With a sharp penknife or needle remove the integ-
ument, testa, from a bean that has been soaked in water
for a day. Near the hilum a small pointed body, the
radicle, will be found. Locate it accurately. Does it
have any relation to the micropyle ?
III. Separate the two halves, cotyledons. Examine
under a good lens. Notice
1. The form and position of the radicle.
2. The delicate structure, plumule, connected with it.
Draw the parts, taking care to represent accurately
the leaves of the plumule and their venation.
IV. Examine beans that have lain a few days on' moist
blotting paper under a bell-jar. What changes have taken
place ?
What part of the seed has developed into the primary
root ? What changes has the plumule undergone ?
V. With the common bean compare a number of other
varieties, "butter bean," "scarlet runner," etc., noting
carefully all points of likeness and difference.
VI. Study next the -common pea, comparing its struc-
ture with that of the bean.
VII. Write a detailed account of your observations of
the bean and pea. Introduce drawings or outline sketches
SEEDS. 3
whenever the description will be rendered more intelligible
by them.
CASTOR OIL SEED. Ricinus communis, L.
I. Study first the external features.
1. Shape and surface. Compare different specimens as
regards shades and distribution of color.
2. Surface markings :
a. The conspicuous, thickened protuberance at one
end, the caruncle, a structure occurring in com-
paratively few species.
b. The string-like raphe, extending from the hilum
(faintly seen at the edge of the caruncle) to
the chalaza, near the other end.
II. Remove the testa and observe the delicate inner
seed coat, endopleura, enclosing the kernel.
III. Split the kernel longitudinally, so as to expose the
embryo. Examine under a dissecting microscope, or with
a good lens. Draw the inner surface of one of the halves
so as to show
1. The outline and venation of the cotyledon.
2. The short, straight radicle.
3. The surrounding endosperm (tissue containing food
material).
IV. Record in detail what you have observed. Note
important differences between the castor oil seed and com-
mon bean.
INDIAN CORN. Zea Mays, L.1
I. Study closely the external features of the grain.
How do the two sides differ ?
1 The grain of corn is really a seed-like fruit, in which the coats of
fruit and seed are blended. Specimens for dissecting should be placed in
water the day before they are to be used.
4 STUDY OF COMMON PLANTS.
II. With a sharp knife make a median longitudinal
section perpendicular to the flat sides of the grain. Re-
peat the process, if necessary, until a good specimen is
secured. Observe on the cut surface
1. The strong external membrane composed of the unitecU
coats of the fruit and seed.
2. The endosperm, a tissue containing starch and other
food materials, very hard in the dry grain, but
easily cut in one that has lain some time in water.
3. The embryo, with its conspicuous organ of absorp-
tion, scutellum, the latter in close contact with the
endosperm.
Draw the section.
III. Remove the entire embryo from a grain that has
been soaked. Dissect out the parts enclosed in the
scutellum. Compare them with the same parts as seen
in section. Note
1. The radicle pointing toward the small end of the
grain, its end covered by the root-sheath.
2. The caulicle, attached to the scutellum, and termi-
nating above in
3. The plumule.
IV. Take a series of transverse sections and locate
each one by comparing it with a longitudinal section.
Repeat this until you are perfectly familiar with all the
parts and their relative position.
V. Study a grain of corn that has sprouted. What
changes has the embryo undergone?
VI. Collect as many varieties of corn as you can and
compare them.
SEEDS. O
VII. Study wheat in the same way that you have
Indian corn, and compare the structure of the two grains.
Compare oats with both.1 In what respects are all three
alike ? Point out the differences between them.
VIII. Write a full account of your observations of 'these
grains. Point out two important particulars in which
they differ from peas and beans.
SEEDS OF WHITE PINE. Pinus Strobus, L.
I. Observe all the external features. Draw in outline a
perfect specimen. Compare the seeds of Austrian pine or
Norway spruce.
II. Remove the testa, exposing the kernel enclosed in
the delicate inner seed coat.
III. Make both longitudinal and transverse sections of
the kernel. Notice
1. The form and position of the embryo.
2. Around this the white, oily endosperm. Draw.
IV. Remove the embryo and examine under a good
lens. How do the two ends differ? How many coty-
ledons are there ?
V. Write a complete description. In what important
particulars does the seed of the pine differ from those
previously studied?
PHYSIOLOGY OF SEEDS.
Storage of Food.
I. Cut through one of the cotyledons of a common
bean and scrape the exposed surface lightly with the
1 Cf. Arthur, Barnes, and Coulter, Plant Dissection, pp. 179, 180.
O STUDY OF COMMON PLANTS.
point of a knife. Mount in water a very small portion
of the powder thus obtained, and examine under a com-
pound microscope, first with the low, and afterward with
the high power.
1. Numerous minute bodies are seen in the field of
the microscope. These are grains of bean starch.1
Are they all of the same size ? Of the same
shape ? Draw two or three of them.
2. Focus carefully and study their structure. Are they
homogeneous ? Compare different specimens in
regard to this point.
3. Run a small drop of iodine solution under the cover
glass and observe the effect. Notice from the
outside how far the reagent has advanced, then
examine that part of the slide under the micro-
scope, and see how differently the starch granules
look after the iodine has acted upon them.
II. Mount in the same way a bit of wheat flo.ur taken
from the inside of a grain of wheat.
1. How do the starch grains compare with those of the
bean in form, size, and structure ? Are the grains
of wheat starch of uniform size ?
2. Touch the cover glass lightly with a needle until
some of the largest grains roll over. What is their
shape ? Draw a few grains in different positions
so as to represent what you find to be charac-
teristic.
3. Test with iodine solution.
III. Examine corn starch obtained in the same way
from a grain of Indian corn.
1 Useful suggestions for the microscopical examination of starch are
given by Strasburger, Practical Botany, pp. 4-15.
SEEDS. 7
1. Compare the grains of corn starch with those of the
bean and wheat. Draw.
2. Test with iodine solution.
IV. Cut a grain of oats in two, obtain some of the
starch as directed in the preceding cases, and examine
microscopically. The compound grains of starch present
a widely different appearance from the simple ones of
Indian corn, wheat, and beans. Study their structure
carefully, and draw one or more. Test with iodine.
From this and preceding observations what do you con-
clude in regard to the usual form and structure of starch ?
What as to its reaction with iodine ?
V. Cut a sunflower akene in two, and remove a small
portion of the endosperm. Mount in water and apply
slight pressure to the cover glass. Under the compound
microscope numerous highly refractive drops of oil will be
seen coming out of the broken tissue. Focus carefully on
an oil drop, and observe its sharply denned border. What
changes does it undergo as the focus is altered?
Various other oily seeds, such as those of the squash,
tomato, pine, English walnut, etc., may be studied in the
same way. Enough of these should be examined to ensure
familiarity on the part of the student with the appearance
of fatty oil under the microscope.
VI. Soak a date seed in water a day or more until it
can be cut easily. Pare off a portion of it with a knife or
scalpel, so as to expose a smooth, even surface, and then
with a razor make extremely delicate sections of the endo-
sperm. Mount some of these in glycerine, and others in
Schulze's solution. Microscopic examination shows that
the date seed consists chiefly of the greatly thickened
walls of the cells that compose its substance. Watch the
8 STUDY OF COMMON PLANTS.
action of Schulze's solution. The blue color that pres-
ently appears indicates cellulose.
VII. Examine similar sections of a coffee seed prepared
and mounted in the same way. Notice how the cell walls
differ from those of the date seed.
VIII. Remove the testa of a castor oil seed, and cut
a few thin sections from the endosperm. Mount in pure
glycerine, and examine with the high power.
1. The sections show (best on the edges where they are
very thin) the cells of the endosperm filled with
numerous rounded bodies. These are aleurone
grains. They are of frequent occurrence in oily
seeds, and constitute an important food substance.
2. Draw a cell with its contents. Examine the aleurone
grains closely, and see if you can detect any struct-
ure. The small rounded body most frequently
seen at one end of the aleurone grain is called a
globoid.
3. Run a drop of water under the cover glass and watch
the effect. Some of the aleurone grains presently
show, besides the rounded globoid, an angular
crystalloid.
Draw again a cell with its contents so as to show the
changes that have taken place.
4. After the water has had sufficient time to act on the
cell contents, it is evident that they are becoming
disorganized, and drops of oil are seen to have
passed out of the section.
NOTE. — It is important that all of these features should be sat-
isfactorily made out before proceeding farther. It may be neces-
sary to prepare a considerable number of slides, and possibly will
require several hours. The essential fact is that in the castor oil
seed two sorts of food are stored : one non-nitrogenous, in the
SEEDS. 9
form of fatty oil; the other nitrogenous, in the form of aleurone.
We shall find the same association of nitrogenous and non-nitrog-
enous food substances in other seeds.
IX. Prepare sections of the endosperm of a flax seed,
and, as before, examine some in glycerine and others in
water. How do the aleurone grains compare in size, form,
and structure with those of the castor oil seed?1
X. Make a transverse section of a grain of wheat that
has lain in water a few hours, cutting it in such a way that
the section will show the coats of the grain and a portion
of the endosperm. Mount in water. Notice
1. The large cells making up most of the endosperm.
What do they contain?
2. Outside of these a layer of cells, rectangular in sec-
tion, containing aleurone.
3. The behavior of the substances contained in the
different cells when iodine is applied. Draw a
portion of the section.
4. The arrangements for protection of the embryo,
together with its food supply, by means of the
united fruit and seed-coats. [The former consists
of several layers of cells with strongly thickened
walls, the latter of two very thin layers imme-
diately outside the cells that contain aleurone.
Tangential sections treated with sulphuric acid,
compared with the transverse sections, will make
the structure plain.]
XL Record in full what you have ascertained regarding
reserve materials and their storage in seeds. What are
the different kinds of non-nitrogenous food substances thus
1 Cf. Frank, Lehrbitch der Pflanzenphysioloyie, p. 158.
10 STUDY OF COMMON PLANTS.
far met with ? How are they recognized ? Mention cases
where you have found them associated with aleurone.1
Protection.
I. Examine an orange with reference to the protection
of the embryos. Make a transverse section of the fruit,
and note carefully all the protective arrangements.
II. Study an apple in the same way.
III. Compare a number of commercial "nuts"; e.g.
almond, chestnut, peanut, hickory nut, Brazil nut. Which
are the most effectually protected ? How do they compare
with other fruits in this respect ?
IV. Make a transverse section of a grain of Indian corn
and examine the pericarp microscopically. Notice the
multiplication of thick-walled cells and their arrangement.
Draw.
V. After observing as many other seeds as are obtain-
able, summarize your observations of the ways in which
the embryo is protected against mechanical injuries, wet-
ting, destruction by animals, attacks of fungi, etc. Are
any that you have examined poorly protected ? 2
Dispersal.
I. Examine the seeds of common milkweed, Asclepias
Cornuti, Decaisne. Compare those of the trumpet creeper,
Tecoma radicans, Juss. Make an outline sketch of both.
II. Study as many as can be obtained of the following :
Seeds of willow or poplar; fruits of elm, birch, maple,
ash, clematis, hop tree, Ptelea, iron-wood, Ostrya or Carpi-
1 Cf. Sachs, Physiology of Plants, pp. 323-340.
2 Cf. De Candolle, Origin of Cultivated Plants, p. 395.
SEEDS. 11
nus, thistle, dandelion, wild lettuce, cotton grass, Erio-
phorum.
In the air of a still room see whether any of these fall
perpendicularly from a height of a few feet. What is the
case when the air is disturbed by fanning?
III. Examine the fruits belonging to some or all of the
following genera : Agrimonia, Geum, Desmodiurn, Circaea,
Galium, Lappa, Xanthium, Echinospermum, Cynoglossum,
Bidens, Cenchrus.
Describe the various appendages and compare them as
to their efficiency.
By means of a thread suspend weights to one of the
hooked appendages of the burdock and ascertain how
great a weight the hook will bear.
IV. Write out a list of fruits attractive to animals,
taking care to include only such as you have yourself
observed.
V. Discuss any other arrangements for dispersal of seeds
with which you are familiar. Read one or more of the
references given below.1
RELATIONSHIPS INDICATED BY SEEDS.
I. Examine seeds of mustard, radish, cabbage, and
other cruciferous plants, comparing them with reference
to their form and size, form and position of the embryo,
nature of reserve material, and other points of difference
and resemblance. The study will be facilitated by com-
paring seeds that have been planted two or three days.
1 Darwin, Origin of Species, Chap. XII ; Lyell, Principles of Geology,
Vol. II, Chap. XL; Hill, Am. Nat., 1883, pp. 811, 1028; Hildebrand,
Verbreitunysmittel der PJlanzen ; AYallace, Darwinism.
12 STUDY OF COMMON PLANTS.
Draw and describe the various parts of some of the
different seeds.
II. Compare in the same way peas, beans, lima bean,
lupine, and peanut. Are they essentially alike in struct-
ure ? Mention points of difference.
III. Compare seeds of squash, pumpkin, watermelon,
muskmelon, cucumber, and gourd.
IV. Compare seeds of tomato, egg plant, pepper, stra-
monium, and hyoscyamus.
V. Compare the seed-like fruits of sunflower, dandelion,
thistle, lettuce, and salsify.
In all the groups thus studied ascertain whether the
seeds are more alike than different. Sections should be
made and drawings introduced wherever they are needed
to render the descriptions more intelligible. Some of the
groups may be omitted if necessary, but the observations
should be thorough and complete as far as they are
carried.
SPECIAL STUDIES.1
I. Polyembryony in the genus Citrus. This requires
an extended comparison of seeds of different
varieties of orange, lemon, and other citrus fruits.
II. Arillate seeds. A study of the seeds of Celastrus
scandens and other arillate species.
III. Relation of the embryo to the reserve material.
Arrangements that favor a prompt supply of food
1 A few subjects for special study are given in connection with this
and other exercises simply as examples of many that will naturally
suggest themselves. In most cases the studies suggested require inde-
pendent investigation, while others, such for example as number IV, give
opportunity for reading and reporting on papers of special interest, par-
ticularly those in recent periodical literature.
SEEDS. 13
to the embryo in early stages of germination.
Cf. Haberlandt, Physiologische Pflanzenanatomie,
p. 288 et seq.
IV. Peculiar cases of plant dissemination. Cf. Ber-
thoud, Botanical Gazette, XVII (1892), p. 321.
V. Identification of species by means of seeds. An
interesting application will be found in the deter-
mination of weed seeds of frequent occurrence in
grass and clover seed. Cf. Beal, Grasses of North
America, I, p. 215.
REVIEW AND SUMMARY.
The seeds we have studied have been selected from
three great classes of plants. To the first class belong
the bean, castor oil, and other plants, the seeds of which
have two cotyledons ; to the second, wheat, Indian corn,
and, in general, all plants with one cotyledon ; and to the
third, pines and their allies, many of which have more
than two cotyledons. The distinctions between these
classes are in many respects fundamental, so that an
examination of the seed of a given plant is generally suffi-
cient to enable us to determine its class in the vegetable
kingdom.1
Furthermore, we have found that there are more re-
stricted groups of plants, called families, the seeds of
which are in many cases, though not in all, so nearly
identical in structure as to indicate at once their family
relationship. The squash, melon, and cucumber belong
to one of these families ; the tomato, egg plant, and stra-
monium to another, and so on. We conclude, therefore,
1 Seedless or " cryptogamic " plants will be studied later. What is
said in the present chapter and those immediately following applies to
the higher or seed-bearing plants, including Gymnosperms.
14 STUDY OF COMMON PLANTS.
that the structure of seeds is an important factor in the
determination of relationship.1
This being the case, it becomes necessary to formulate
certain general conceptions of form and structure, and to
Morphology adopt descriptive language by which they may
of seeds, ke expressed with clearness.2
The essential parts of a seed are the protective coats
and the embryo with its store of food. The seed-coats
commonly show a division into an external,
hard, often colored, layer, the testa, and an in-
ternal, more delicate one, the endopleura; the former
term, however, is frequently employed to designate the
coats collectively. In many species the endopleura is
wanting. Externally the testa may be smooth and pol-
ished, as is the case with the seed of the castor oil plant,
or it may be covered with hairs, as cotton seeds are, or,
again, it may be extended into a wing, like that belong-
ing to the seeds of the catalpa, and various other modifi-
cations may occur, having, as a rule, a direct relation to
protection or dissemination. An additional coat, usually
colored and fleshy, known as the aril, is rarely present.
The parts of the embryo are the radicle, cotyledons, and
plumule. As we have seen, it may have one, two, or sev-
eral cotyledons, and accordingly is said to be
monocotyledonous, dicotyledonous, or polycoty-
ledonous. The embryo varies greatly in different species
as regards form, position, and size, being straight or
curved ; occupying the whole space within the seed-coats,
or only a small portion of it ; the cotyledons alike or dif-
1 See, for example, Rowlee, Bulletin of the Torrey Botanical Club,
XX (1893), p. 1, and Rolfs, Botanical Gazette, XVII (1892), p. 33.
2 For a more extended treatment of the morphology of seeds cf . Gray,
Structural Botany.
SEEDS. 15
fering in size or shape, and so on ; l but these peculiarities
are generally constant and characteristic in the species, or
group of species, in which they occur. Whatever the
form and position of the embryo, the radicle points towards
the micropyle.
Food materials of various kinds are stored up for the
use of the plantlet during germination. If the tissue con-
taining such reserve materials surrounds the
embryo, it is called the endosperm, or, using an
old phraseology, the seed is said to be albuminous. If, on
the contrary, the reserve materials are stored within the
embryo itself, even if they are of precisely the same
nature, the seed is said to be without endosperm, or exal-
buminous.2 The terms are not well chosen, but have be-
come so fixed as to render it necessary to recognize them.
Certain structural peculiarities are intimately connected
with the developmental history of seeds. They are at-
tached to the mother plant by a minute stalk _
, , Hilnm, rapne,
through which nutritive materials are conveyed chalaza, mi-
during their period of growth, but from which cr°Pyle-
they break away at maturity, leaving a scar called the
hilum, such as is plainly seen on the common bean. From
the hilum, in the great majority of cases, extends a fine,
fibrous bundle, the raphe, like that of the castor oil seed,
either the entire length of the seed, or for a shorter dis-
tance, ending in a point, the so-called chalaza, where the
seed coats cohere with each other and with the parts
within. The raphe is simply a continuation of the stalk
through which food materials were carried to the develop-
ing seed, the chalaza being the point where the materials
1 Cf. Lubbock, Seedlings.
2 For the rare cases in which a distinction must be made between
endosperm and perisperm, see Gray, Structural Botany, p. 310.
16 STUDY OF COMMON PLANTS.
were distributed to the interior of the seed. The hilum is
in almost all cases a conspicuous feature, readily seen by
the unaided eye, or with the help of a lens. The chalaza
and raphe, on the contrary, are frequently obscured by
the growth of the seed-coats. The micropyle is the open-
ing between the seed-coats, readily seen in early stages of
development, but often not easily recognized from the out-
side of the mature seed. Its position is most readily
determined by opening the seed and rinding the radicle,
which, as already said, points toward the micropyle.
The form of the seed is also determined largely by the
direction of growth of the ovule. In the majority of
cases, of which the castor oil seed is a good
terminedby- example, the developing ovule turns upon its
direction of longitudinal axis in such a way as to take an
inverted position, so that in the mature seed
the hilum and micropyle are close together, the chalaza at
the opposite end, and the raphe running the whole length
of the seed. Such seeds are said to be anatropous.
Others, as, for example, the seeds of stramonium, are
simply much curved, bringing both chalaza and micropyle
near the hilum, one on either side of it. This is the
so-called campylotropous form. In comparatively few
species, of which buckwheat is an example, the axis of
the ovule remains straight throughout its development,
and the seed is said to be orthotropous. Modifications,
particularly of the first and second forms, are of frequent
occurrence. Cf. Gray, Structural Botany, pp. 278, 279.
Physiologically, seeds present many points of interest.
The arrangements for dispersal, for protection,, and for
Physiological the support of the embryo in germination are
adaptations, among the most important.
A species generally has a better chance of survival if
SEEDS. 17
the seeds are conveyed to some distance from the plant on
which they are produced. By this means they
are less likely to come into as close competition
with each other as if they grew up together around the
parent plant; they are also brought into other conditions
of soil and surroundings, and the chances for cross-fertil-
ization are greater, which, as we shall see, is often a
marked advantage. Accordingly it is found that a variety
of structures exist that are directly adapted to the dis-
semination of seeds. Thus many seeds are distributed
by the action of the wind. These are most frequently
light in weight and provided with appendages in the form
of wings or hairs, such as those of the catalpa, poplar,
milkweed, and many others. Seeds distributed by animals
are often concealed within brightly colored or otherwise
attractive fruits ; in other cases they are provided with
hooks or other appendages by which they become attached
to the wool or hair of various animals, and the seeds of
many water-loving plants are carried in the mud that
adheres to the feet of aquatic birds. The seeds of still
others are washed by oceanic currents to the shores of
distant islands or continents, and, finally, the agency
of man, both intentional and unintentional, becomes a
potent factor in the distribution of plants.
By these and other agencies the forms that constitute the
vegetation of the earth have come to occupy the places in
which we now find them, and it becomes for every species
that we meet a fascinating and often intricate problem to
endeavor to ascertain how it came to be where it is.
It is plain that from the time they leave the mother plant
to the time of germination, seeds are exposed
to numerous dangers, and that they require pro-
tection. This is afforded in part by the shape of the seed,
18 STUDY OF COMMON PLANTS.
most frequently a combination of strong arches, by which
the danger of crashing is lessened; in part by the hard
testa, which sometimes has a compact, polished exterior
that resists the entrance of water and germs ; and in some
cases by bitter or otherwise distasteful substances stored
up in the seed. In addition to these means of protection
the embryo is often securely packed in the midst of
abundant endosperm, and not infrequently still other pro-
vision is made for its safety.
Microscopic examination of a seed shows the presence
of one or more kinds of reserve materials. As a rule,
Reserve starch, or some other non-nitrogeneous sub-
materials, stance, is associated with aleurone or its equiva-
lent, thus supplying all the essential food elements. Oil,
as a condensed form of food, is largely employed in small
seeds and those that are transported by the wind, since by
the use of this material greater lightness, volume for
volume, is secured than if starch were employed. Cellu-
lose takes the place of starch or oil in the date and some
other seeds, which, as Haberlandt has pointed out, are in
this way rendered less liable to decay and the attacks of
animals during their long period of germination.1 It is
also seen upon the careful study of almost any seed that
the reserve materials are so placed as to be ready for
immediate use when wanted, either lying in the cells of
the embryo itself or packed closely around it, and there
brought into immediate relation with its absorbing tissue.
Still other physiological adaptations will be apparent as
a greater number of seeds are examined and their struct-
Other adapta- ural peculiarities brought to light. As an exam-
tions, pie may fog mentioned the fact that anatropous
seeds by curving upon themselves during the early stages
1 Physiologische Pflanzenanatomie, p. 285 et seq.
SEEDS. 19
of their development bring the micropyle into such a
position as to favor the entrance of the pollen tube.
Again, the hairy appendages of numerous achenia, such
as those of the dandelion and related plants, are so placed
as to bring the radicle on the lower side as the object
alights on the surface of the ground.1 Such adaptations
are of so constant occurrence that the student can hardly
fail to receive the impression, in general a correct one,
that the simplest structural facts are likely to have some
important physiological significance. On the other hand,
there are numerous cases of " accidental " peculiarities, for
which no reason is manifest, and which at present are not
explained.
1 Cf. Rowlee, I.e.
20 STUDY OP COMMON PLANTS.
II. GROWTH OF PLANTS FROM THE SEED.
MATERIAL REQUIRED.
Seedlings of the common bean, pea, sunflower, white mustard, flax,
and hemp, from one to four weeks old.1
Seedlings of Indian corn and wheat of various ages.
Pine seedlings from a few weeks to a few months old.
Seeds of squash and other cucurbits in early stages of germination.
I. Take seedlings of different ages of the plants named
in the first list above. Wash the roots and let them stand
in a dish of water to prevent drying. Compare them and
satisfy yourself as to the following points :
1. Do they all have a taproot?
2. Do they all have a hypocotyl, i.e. a stem supporting
the cotyledons?
3. How do the cotyledons of the different plants differ
a. As to form and size ?
b. In function ? Have any of them wholly lost their
function as foliage leaves? Are there any
apparently transitional forms, as if this function
were partially lost?
4. How does the pea differ from the sunflower in the
time of unfolding the proper foliage leaves ? Can
1 The seeds should be sown at intervals of a few days, some in sand,
others in moist (not wet) sawdust, and still others on folds of damp
blotting paper under a bell-jar. There should be three or four lots of as
many different ages. Pine seedlings, which are rather difficult to raise,
may be obtained from nurseries.
GROWTH OF PLANTS FKOM THE SEED. 21
you suggest any reason for this difference? How
do the other seedlings compare in this respect?
II. Compare the seedlings of Indian corn and wheat
that have attained the height of several inches.
1. Describe the cotyledon. Has it undergone any
change during the process of germination ? l
2. Is there a taproot?
3. Mention all the points in which the two plants are
alike ; those in which they differ.
III. Compare the seedlings of the Indian corn and
wheat with those of the pea, bean, etc., previously studied.
Point out all the essential differences, noting especially
1. Number of cotyledons.
2. Venation of foliage leaves.
3. Position and form of leaves.
4. Presence or absence of a persistent taproot.
IV. Examine seedlings of the white pine or other species
of pine. In what important feature do they differ from
any of the young plants thus far studied?
V. Summarize your observations and show how the
class to which a plant belongs may be determined by
inspection of the seedling.2
VI. Comparing the seedlings of different dicotyledonous
plants (beans, sunflower, etc.), ascertain whether any of
them have the two cotyledons unlike in size or shape. Is
there anything to indicate that the form of the embryo
is determined by that of the seed ? 3
1 The protective sheath is regarded as a part of the cotyledon, while
the other part, the scutellum, remains in the grain. Cf. Lubbock, Seed-
lings, IT, p. 587.
2 Cf . Gray, Structural Botany, Chap. II.
3 Lubbock, Seedlings, I, pp. 30-34, 75-77.
22 STUDY OF COMMON PLANTS.
VII. Notice the way the different seedlings break
through the ground. Do those of all the dicotyledonous
plants behave alike? How do they compare with those
of Indian corn and other monocotyledons ? 1
VIII. Examine seedlings of squash, melon, or cucum-
ber, comparing specimens that are just rupturing the testa
with older ones. Observe the position and structure of
the " peg," and the way it aids in throwing off the seed-
coats.2
IX. Ascertain whether direction of growth is affected
by external conditions.
1. Compare mustard or other seedlings grown in the
dark with others growing in front of a window.
2. Turn on their sides some of the pots with seedlings
a few inches high, and after a day or two notice the
result.
3. Observe the effect of slow change of position in neu-
tralizing geotropism and heliotropism.3
X. Take up a seedling of wheat about two weeks old,
and examine the grain.
1. Notice how it differs from a grain that has not
sprouted.
2. Remove a small portion of the endosperm and ex-
amine under a high power of the microscope.
Compare the starch grains with those of wheat
that has not sprouted. What changes have taken
place ? Draw some of the grains that show " cor-
rosion."
1 Darwin, Power of Movement in Plants, p. 77 et seq.
2 Darwin, I.e., p. 102.
3 For this purpose an instrument known as a klinostat is employed.
Cf. Goodale, Physiological Botany, p. 408; Sachs, Physiology of Plants,
p. 684. Less expensive apparatus is easily devised.
GROWTH OF PLANTS FROM THE SEED. 23
3. Examine in the same way starch from the endosperm
of a corn seedling that has attained several inches
in height.
XI. Write a detailed account of the phenomena of
germination as far as you have observed them.
SPECIAL STUDIES.
I. How seedlings break through the ground. A
further comparison, including the study of as
many species as practicable.
II. Results of planting certain seeds wrong side up.1
III. Results of removal of cotyledons at an early stage
of growth.
IV. Whether detached embryos are capable of germi-
nation.
V. Conditions most favorable to germination.
VI. Length of time that seeds retain their vitality.
VII. How far seedlings of the same family are alike in
structure and habits.
VIII. Changes capable of demonstration under the micro-
scope that take place in reserve materials during
germination.
REVIEW AND SUMMARY.
In our study of seedlings we have found that the same
parts are present that were observed in the seed, but
marked changes have taken place in size, position, texture,
and other particulars. The distinctive features of the
1 Cf. Darwin, I.e., pp. 103, 104.
24 STUDY OF COMMON PLANTS.
great classes, however, are as strongly marked as they
were in the seed, and each class exhibits in its seedlings
characteristic, though not always distinctive, habits.
The radicle of dicotyledonous seedlings elongates and
extends downwards as the primary root, and at the same
Dicot ledo ^me *n mos^ sPecies grows upward, forming the
nous seed- " hypocotyl," at the upper extremity of which
the cotyledons are borne. In some species, as
in the pea, the hypocotyl is wanting, or is extremely short,
the cotyledons remaining in the ground instead of being
lifted into the air. In such cases a rapid development of
the "epicotyl," or first internode of the plumule, takes
place, thus securing to the young leaves as they unfold
full exposure to air and light. The hypocotyl (or, if this
is wanting, the epicotyl) breaks through the ground in the
form of an arch, an arrangement for the protection of the
delicate growing point.1
Monocotyledonous seedlings exhibit considerable variety
among themselves, although several pretty distinct types
may be recognized. In the grasses the scutel-
nous seed- lum, which represents a part of the cotyledon,
lmgSl remains enclosed in the grain, and the straight
plumule is erect, instead of arched, as it breaks through
the ground. In many other species, as for example the
date palm, a peculiar modification of this mode of germi-
nation is seen. As before, a part of the cotyledon remains
in the seed as an organ of absorption, but the other end
elongates and grows downward, forming a sheath from
which the first leaf afterward emerges.2 A more or less
conspicuous primary root may be present, as in Indian
1 Cf. Darwin, Poiver of Movement in Plants, pp. 87, 88.
2 See figures of palm seedling, Goebel, Classification and Special Mor-
phology of PI a Jits, p. 432.
GROWTH OF PLANTS FROM THE SEED. 25
corn, or it may be hardly distinguishable from the secon-
dary roots, as is the case with wheat.
Seedlings of pines and their allies (gymnosperms), aside
from the fact that many species have more than two coty-
ledons, can hardly be said to possess characters seedlings of
specially distinctive of their class. In many gymnosperms.
cases the testa is carried up on the tips of the cotyledons,
and afterwards thrown off by their bulging outwards. In
some species the cotyledons remain under ground.
Cotyledons, as a rule, perform functions widely different
from those of ordinary green leaves, and accordingly pre-
sent striking modifications of form and structure. n , . .
Cotyledons
While in some cases they unfold and deport and their mod-
themselves as foliage leaves, in others, as for lficatlonSl
example the pea and acorn, they have lost nearly all
resemblance to leaves, and serve merely as storehouses of
reserve materials ; while in still other cases, as in the grain
of corn or wheat, the cotyledon becomes largely an organ
of absorption. Interesting transitional forms are seen in
the common bean and other plants in which the cotyle-
dons rise above the surface and turn green, but soon dry
up after their reserve materials are exhausted. The
embryos of some dicotyledonous plants produce but one
cotyledon, the other being rudimentary. A curious in-
stance is that of the orange, in the seed of which several
embryos are formed with cotyledons varying greatly in
size. In various species of cacti both cotyledons are rudi-
mentary, being represented by minute bodies only a milli-
meter or two in diameter. In the latter case the radicle is
thickened and serves as a storehouse, the cotyledons be-
come superfluous, and are finally reduced to insignificant
appendages, an illustration " of the principle of compensa-
tion or balancement of growth, or, as Goethe expresses it,
26 STUDY OF COMMON PLANTS.
' in order to spend on one side, Nature is forced to econo-
mize on the other side.' " l A considerable number of
seeds, notably those of certain plants belonging to the
mustard family, have one cotyledon larger than the other,
an arrangement naturally following the way the embryo
is packed in the seed. These and various other peculiar-
ities may be seen in the embryo before germination, but
are more pronounced in the young seedling.
During germination the reserve materials stored in or
around the embryo are drawn upon for the sustenance
Chan es °^ ^e seedling. Microscopic examination of
in reserve the endosperm of a grain of wheat or Indian
corn, after the seedling is well started, shows
that the starch granules have undergone remarkable
changes due to the action of a ferment that gradually
dissolves them. Other reserve materials, such as oil,
aleurone, etc., undergo similar changes, by which they
are fitted for absorption, but these are too complicated
to be discussed in an elementary work. Those interested
in the chemistry of germination should consult Sachs,
Physiology of Plants, and later articles in various botan-
ical periodicals.
Certain external conditions are essential to germination.
Of these the most important are (1) a suitable amount of
Conditions of water, (2) proper temperature, and (3) access
germination, of oxygen. Simple experiments are easily con-
ducted to establish these facts, which are also, in part,
matters of familiar observation. Thus when a crop of
grain has been sown it is well understood that it will not
come up if the earth is too dry, and that it is more likely
to decay in the ground than to germinate if it is too wet,
1 Cf. Darwin, Power of Movement in Plants, pp. 94, 98 ; Lubbock,
Seedlings, II, p. 6.
GROWTH OF PLANTS FROM THE SEED. 27
and careful experiments go to show that seeds sprout
more promptly and surely with a less amount of water
than is commonly supplied in artificial cultures. Too
high or too low a temperature is equally unfavorable,
although there is a pretty wide range within which most
seeds will germinate. An even temperature is found to
be more favorable to prompt germination than a variable
one. Finally, if oxygen is excluded, even if all other con-
ditions are fulfilled, germination fails to take place. It is
for the purpose of securing an abundant supply of oxygen
that we leave the sawdust lying up loosely, rather than
closely packed, about the seeds, when we are raising seed-
lings in the laboratory. For the same reason, a light,
loose soil is more favorable for gardening than a compact
and heavy one. These conditions are well known, and
are taken into account in practical operations, although a
comparison of different seeds during germination estab-
lishes the equally important fact that both individual and
specific peculiarities exist. Some seeds require more
moisture than others, and the degree of temperature most
suitable for germination varies with different species, ^and
so on. An interesting series of experiments on the condi-
tions of germination and the individual peculiarities just
referred to has been carried out at the Cornell University
Experiment Station. For an account of these, see Science,
XIV (1889), p. 88.
Some of the phenomena connected with germination are
of much interest and are easily observed. The first step
consists in the forcible absorption of water, Attendant phe-
manifested by the great increase in size of ger- nomena.
minating seeds, and the pressure they exert if an attempt
is made to confine them in a closed vessel. Testing with
a thermometer shows that the process of germination is
28 STUDY OF COMMON PLANTS.
accompanied by a rise of temperature, and chemical ex-
amination indicates absorption of oxygen and exhalation
of carbon dioxide ; in other words, respiration is going on.
The length of time during which seeds retain their
vitality has been the subject of much discussion. Stories,
Duration of frequently repeated, of the growth of grain
vitality. many centuries old, taken from Egyptian tombs,
and of raspberry seeds from a Roman skeleton in England,
etc., are generally discredited, for the reason that sufficient
proof is lacking. On the other hand, a series of experi-
ments, conducted for a long period by a committee of
the British Association for the advancement of science,
shows that some seeds have certainly retained their ca-
pacity for germination from twenty to forty years, and
even longer.1
1 Report of British Association, 1857, Dublin meeting.
THE ROOT. 29
III. THE ROOT.
MATERIAL REQUIRED.
Roots of Indian corn and other seedlings used in the preceding
exercise.
The lower parts of a fully grown corn-stalk, showing the supporting
roots.
Aerial roots of English ivy, or trumpet-creeper.
Turnips and other fleshy roots from the market.
Slips of Verbena, Tradescantia, and other common conservatory
plants.
I. Examine more in detail the roots of seedlings already
studied.
1. Taking specimens of Indian corn of different ages,
note
a. Where the secondary roots arise.
b. Whether any of them have given rise to roots of a
higher order.
c. How they compare in these particulars with those
of wheat.
2. Compare the roots of the sunflower, bean, and pea
with reference to the same points.
II. Study the root-hairs of various seedlings, beginning
with some that are growing on blotting paper.
1. On what parts of the roots are they produced?
2. Remove, with a pair of fine forceps, a portion of a
root where it is thickly covered with root-hairs.
30 STUDY OF COMMON PLANTS.
(The roots of wheat or oat seedlings are excellent
for this .purpose.) Mount in water, taking care
not to injure the delicate tissue by undue press-
ure. Examine under a high power of the com-
pound microscope.
a. Observe the structure of the root-hairs.
b. Ascertain how they are connected with the body
of the root. Draw.
c. Run iodine solution under the cover glass, and
watch the effect. What do you- infer as to the
permeability of the cell membrane and the
capacity of the cell contents for absorption ?
3. Pull up a specimen that has grown in clean sand.
Shake off as many of the adherent particles as
possible. Examine under a good lens. It will be
seen that many grains of sand still remain attached.
Ascertain whether this is due in any way to the
presence of root-hairs.
III. Cut off the tips of some of the fine roots of wheat
or oats grown under a bell-jar. Mount in water, and
examine with the compound microscope. Select a good
specimen, and draw the end carefully so as to show the
root-cap.
IV. Determine in what part of the root increase in
length takes place.. Use for this purpose roots of Indian
corn, peas, or sunflower, growing on moist blotting paper
under a bell-jar. With a camel's-hair brush and India ink
make a series of marks at intervals of a millimeter, begin-
ning at the apex of the root. Replace the bell-jar, and as-
certain by subsequent observations, about a day apart,
where elongation has taken place.
V. Determine the direction naturally taken by roots.
THE ROOT. 31
1. Pull up beans or peas that have been growing in saw-
dust, and observe the entire root system. How
do the secondary roots compare with the primary
in their direction of -growth? If- roots of a higher
order have been formed, ascertain whether they
take the same direction as either of the preceding.
Would it be advantageous for the plant if all grew
downward ?
2. Take a germinating pea or squash seed, with a radi-
cle a centimeter or more in length, and fasten it
to a cork by a pin so that the radicle will point
horizontally. Keep it in a moist atmosphere under
a bell-jar, and exclude the light by covering with
a dark cloth. Observe the subsequent growth of
the radicle. Vary the experiment by turning
other specimens so that the radicle will point
nearly vertically.
3. Tie a piece of netting over the mouth of a beaker or
wide-mouthed bottle filled with water, and place on
it a number of seeds of white mustard that have
just begun to germinate. Allow the apparatus
to stand in front of a window without being dis-
turbed, filling with water occasionally, so that the
growth of the seedlings will be uninterrupted.
Observe the direction taken by the roots.
VI. Examine different roots with reference to their
mechanical functions.
1. The supporting roots of Indian corn. Notice where
they originate, their direction of growth, and their
double action as braces and guys.
2. Aerial roots of the English ivy, or trumpet-creeper.
Compare these with ordinary roots.
32 STUDY OF COMMON PLANTS.
3. Examine under a lens the structure of a blackberry
root, or that of some other common woody plant.
Cut a transverse section, and notice the position
of the wood elements. Compare this with their
arrangement in the stem. A little reflection will
show that the arrangement of the mechanical ele-
ments corresponds with the very different condi-
tions that obtain in root and stem. The former
must be so constructed as to resist a force that
tends to pull it out of the ground ; in the latter,
on the other hand, resistance to a lateral and ver-
tical force must be provided for.1
Other roots should be examined in the same way.
Those of Indian corn seedlings will be found
useful.
VII. Compare fully grown turnips and carrots, radish,
or salsify with the roots of seedlings of the same plants.
What changes of form and structure have they undergone?
VIII. Study the formation of adventitious roots, as
seen in Verbena and other plants, grown by florists from
slips. Adventitious roots of Tradescantia can be obtained
by placing a fresh branch in a closed bottle so that the
cut end will stand in a little water at the bottom.
SPECIAL STUDIES.
I. Protection of the growing point of the root. A
number of water plants furnish excellent material
for microscopic study of the root-cap. Among
them are Lemna minor, common everywhere in
stagnant waters, and Pontederia crassipes, fre-
quently grown in artificial ponds. Certain aerial
1 Cf. Haberlanclt, Physiologische Pflanzenanatomie, p. 125 ct seq.
THE ROOT. 33
roots, as those of Pandanus, commonly culti-
vated in conservatories, also have remarkably
developed root-caps.
II. Conditions affecting the formation of root-hairs.
An interesting investigation is suggested by
Haberlandt, Physiologisclie Pflanzenanatomie, p.
147 et seq.
III. Propagation of plants by slips and cuttings. Ascer-
tain what plants are regularly propagated in this
way by florists and what conditions are necessary.
IV. Reserve materials stored in roots. Examination of
the blackberry, elecampane, and other roots, to
determine the nature of the food substances con-
tained in them.
V. Influence of moisture on the direction taken by
roots. " Search for water " by roots of trees.
VI. Minute anatomy of roots. (This may be deferred
with advantage until the stem is studied micro-
scopically.)
VII. Estimate of the total length of the root system of
some common plants. Johnson, How Crops
Groiv, p. 242.
VIII. Roots of parasites. Sections of roots of Comandra
or mistletoe, with a study of their relation to the
plants on which they have fastened.
REVIEW AND SUMMARY.
Roots function as organs of absorption, as storehouses of
reserve materials, and as a mechanical means of holding
the plant firmly in its place.
34 STUDY OF COMMON PLANTS.
As organs of absorption, it is essential that they should
have a large extent of surface in contact with the soil.
Eoots as ^n PuHmg UP seedlings of different sorts it is
organs of apparent that the total length of their roots
is many times that of the aerial parts, and this
is frequently still more striking when the earth is carefully
washed away so as to expose the whole root system of
older plants. The surface is further increased by the
formation of root-hairs. These are delicate, elongated
cells, arising from the roots back of their growing point,
and so numerous under favorable conditions as to give
them a densely hairy appearance, easily noticeable to the
unaided eye. By their adhesive surface the root-hairs
attach themselves closely to the particles of soil, and by
means of acid excretions aid in preparing for absorption
the crude food materials of the earth. These substances,
in solution, are then taken up and carried to the parts
within. It is, moreover, through the agency of the root-
hairs that the enormous volume of water evaporated by
the leaves of plants in full foliage is taken up from the
soil and started on its upward course.1
The roots of many plants, particularly those that live
more than a year, fulfil an important function as reservoirs
Eoots as °f reserve materials upon which the plant draws
storehouses, when it begins anew its period of active growth.
Suitable tests show that starch and sugar are the food
substances most commonly stored in roots; inulin also
occurs, though more rarely. These and other vegetable
products are described in detail by Sachs in his Physiology
of Plants. The shape taken by roots that serve as store-
houses is sometimes quite characteristic. As examples
1 Johnson, How Crops G-row, p. 243 ; Haberlandt, Physiologische
Pflanzenanatomie, pp. 148, 149.
THE ROOT. 35
may be mentioned, the napiform roots of most turnips, the
conical roots of carrot, salsify, etc., the moniliform roots of
some pelargoniums, and so on.
Besides acting as organs of absorption and as storehouses
of reserve materials, roots fulfil a-n important function in
holding the plant firmly in its place. A study Mechanical
of the arrangement of their tissues shows a functions,
manifest adaptation to this function, the mechanical ele-
ments being placed compactly at the center, a position in
which they are able to resist to the best advantage a
pulling force that tends to break the root or draw it out
of the ground. Such aerial roots as those of the poison
ivy serve to hold the stem securely to some external sup-
port, and the prop roots of Indian corn that arise a little
above the surface of the ground constitute an admirable
system, of braces and guys, by which the stalk, with its
heavy load of ears, is enabled to maintain an erect posi-
tion. Considering the size and weight attained by a
single cornstalk with its fruit, and its exposure to heavy
winds and rain, it is difficult to conceive of a more
effective and, at the same time, more simple mechanical
arrangement.
In their mode of growth roots exhibit a remarkable
adaptation to their environment. Growth in length takes
place just behind the tip, which is thus free to Mo(Je of
turn in any direction, curving aside as it meets growth,
obstacles, and directing its way towards moisture or food,
as occasion requires, without involving any disturbance of
the older parts that have already become fixed in the soil.
The growing point is covered by the root-cap, and thus
protected from injury.
The primary root grows perpendicularly downwards,
but the secondary roots, reacting differently to the pull of
36 STUDY OF COMMON PLANTS.
gravitation, grow down obliquely, while roots of a higher
order extend indifferently in various directions. The
result is such a distribution of the root system
Primary and ' . . . „ •
secondary as to bring it into contact with the soil far more
roots, perfectly than if the roots grew down together
in a common bundle. It has been noticed, however, that if
the end of the primary root is destroyed one or more of the
secondary roots near it grow vertically downward to take
its place.1
While the branches arising from the first or primary
root are properly called secondary, the same term is also
Adventitious frequently applied to roots of a higher order,
roots, and is sometimes rather loosely extended to
those given off by the stem and other parts of the plant.
The latter, however, are commonly spoken of as adventi-
tious. Aerial roots, such as those of the ivy and trumpet-
creeper, properly fall under this head. Other adventitious
roots are of great importance in the practical operations
of florists and gardeners, enabling them to increase their
stock by taking advantage of the capacity of slips and
cuttings for promptly forming roots. The readiness with
which cuttings of willows and poplars produce adventitious
roots, together with their rapid growth, has led to their
extensive planting in the western states, and many trouble-
some weeds owe their pertinacious hold on the soil to the
same habit.
In a comparatively small number of plants, of which the
dodder is a familiar example, adventitious roots take the
Parasitic form of suckers which penetrate the tissues of
habits, other plants, on which they live as parasites.
The plant thus attacked is called the host, from the rela-
tion in which it stands to its parasite. But few flowering
1 Darwin, Power of Movement in Plants, p. 196.
THE ROOT. 37
plants have become truly parasitic, the habit, as it occurs
in the vegetable kingdom, being chiefly characteristic of
fungi.
In their microscopic structure roots exhibit essentially
the same tissues and elements as are found in the stem,
which we shall soon study in detail. There are, Minute anat.
to be sure, certain differences of arrangement, °my-
already mentioned in connection with the mechanical func-
tion of roots, that cannot here be discussed at length.
Those who wish to make a thorough study of the minute
anatomy of roots will find the necessary assistance in such
works as Strasburger's Practical Botany and De Bary's
Comparative Anatomy of the Phanerogams and Ferns.
38 STUDY OF COMMON PLANTS.
IV. THE STEM.
MATERIAL REQUIRED.
Fresh shoots of apple-tree, grape-vine, oak, elder, and basswood.
Stalks of Indian corn put up in alcohol after they have attained full
size. Stems of common greenbrier, Smilax rotundifolia, L.
Shoots of white pine from one to three years old, preserved in alcohol.
Similar specimens of arbor vitae or of red cedar.
Specimens of white oak, hickory, ash, Norway spruce, palm, and other
woods, showing transverse and longitudinal sections.
A collection of greenhouse plants, including rose geranium, primrose,
Coleus, Tradescantia, and others.
Tendrils of grape-vine, spines of honey locust, common potato, and
such other modified stems as are procurable.
STRUCTURE AND MODE OF GROWTH.
I. Study first the gross anatomy of a number of woody
stems.
1. With a sharp knife make a transverse section of a
one-year-old shoot of an apple-tree. Examine
under a good lens, and draw an enlarged outline,
showing the position and relative proportions of
pith, wood, and bark.
2. Separate the bark into its three layers,
a. External, corky layer.
b. Middle, green layer, not sharply delimited from the
c. Inner bark, or bast.
x Try the strength of these different parts by sepa-
rating and pulling upon them.
THE STEM. 39
3. Examine the wood closely. Notice the medullary
rays, appearing like lines radiating from the pith.
Careful inspection shows numerous openings in
the wood between the medullary rays. These are
the ends of vessels that convey water and air
through the stem. It can also be observed that
the pith is made up of minute cells. These struct-
ures may be seen still more readily in the grape-
vine.
4. With the stem of the apple-tree compare those of the
grape-vine, common elder, and oak, making trans-
verse sections, as before. In what respects do
they all agree ? How do they differ?
II. Examine the stem of Indian corn, making both
transverse and longitudinal sections. What part of the
stem has the firmest tissue ?
Make an outline sketch of the transverse section, show-
ing the position of the woody parts as they appear under
a good lens. Compare with this a similar section of the
stem of a palm or other monocotyledonous plant. Com-
mon greenbrier is suitable for this purpose.
III. Study shoots of white pine, two or three years old,
that have lain some time in alcohol. Indicate by means
of a diagram the relative position of pith, wood, and bark.
Using $n older, dry specimen, that has been cut so as
to show a smooth transverse section, notice the succession
of annual rings. How does the outer edge of each ring
differ from the inner? Determine the age by counting
the number of rings. Examine the stem of the arbor
vitae or red cedar, and see if it corresponds in structure
with that of the white pine.
IV. Write an account of the different stems you have
40 STUDY OF COMMON PLANTS.
studied. Show how the stem of a monocotyledon, such as
Indian corn, differs from that of the apple-tree and other
dicotyledonous plants. With which do the stems of the
conifers (pine, arbor vitse, etc.) agree ?
V. Ascertain the age of specimens of white oak, hickory,
ash, pine, and Norway spruce, by counting the annual
rings. The work must be done with care, in order to
insure accuracy. In examining large sections, draw a
straight line from the center to the periphery, and mark
off on it intervals of exactly one inch, beginning on the
outside. Count the number of rings in each division and
record them in their order. Compare the rapidity of
growth of the pine and spruce ; of the ash and hickory.1
MINUTE ANATOMY.
I. Take fresh shoots of the apple-tree, and cut a number
of transverse sections. Mount some in water, others in
glycerine, and still others in Schulze's solution for micro-
scopic study.2 Examine first with the low power. Tak-
ing the parts in order, beginning with the outside, we find
1. The outer bark, or cork, consisting of several layers
of flattened cells with reddish-brown contents.
(The remains of the epidermis outside of the cork
may be disregarded.)
2. The middle bark, or cortical parenchyma, consisting of
a broad zone of cells with green contents (chloro-
phyll). Near the inner edge of this zone are
bundles of thick-walled elements, bast fibers. The
1 Other species may of course be used if more convenient.
2 The success of the work depends upon, having good sections to study.
Worthless ones must be thrown away, and sectioning continued unt»
entirely satisfactory specimens are obtained.
THE STEM. 41
latter are nearly colorless, their very small cavity
showing as a dark point at the center.
3. The inner bark. This is best studied in stems four
or five years old. It is composed of
a. Sieve-tubes, narrow elements with light-colored
walls.
b. Bast parenchyma, much wider cells frequently con-
taining chlorophyll.
c. Bundles of bast fibers similar to those already
described.
4. Cambium. In the winter a sharp line of demarcation
between wood and bark is seen, but in spring there
is formed a zone of fresh tissue known as the cam-
bium, from the inner cells of which a new layer of
wood is produced, and from the outer ones a new
• layer of bark. See VII below.
5. The wood. In this observe the following:
a. Vessels with large openings.
b. Wood fibers, smaller elements with narrow lumen
and thick wall.
c. Wood parenchyma, This is more easily made out
on longitudinal section.
d. Medullary rays, extending from the pith outwards
and continuous with those of the inner bark.
6. Pith, consisting of very large cells marked by numer-
ous pits.
II. Prepare next a number of radial longitudinal sec-
tions, mounting as directed above, and study in the same
order, comparing them, step by step, with corresponding
parts of the transverse sections.
1. Ascertain whether the cork cells present the same
appearance on transverse and longitudinal sec-
42 STUDY OF COMMON PLANTS.
tions, and in the same way compare the cells of
the cortical parenchyma as seen in both.
2. Taking the inner bark next, the sieve-tubes are
easily recognized by their narrowness and length,
and also by their soft, light-colored walls, while
the bast parenchyma consists of much shorter and
wider cells. The medullary rays present a marked
appearance, looking, on radial sections, like brick
work.
3. Look for crystals of calcic oxalate, often found in con-
siderable numbers in cells adjacent to the sieve-
tubes.
4. The bast fibers are to be looked for in places corre-
sponding to their position in the transverse section.
They may or may not be found in some of the lon-
gitudinal sections. Why ?
When you have found them, note the points in which
they differ from all the other elements of the bark.
5. Passing to the wood, the large pitted vessels are at
once recognized. It is seen that they are com-
posed of long cylindrical cells placed end to end,
their dividing walls having been absorbed, or with
only traces of them remaining, so that they form
continuous ducts. The wood fibers also are
greatly elongated, but are much narrower. Their
walls are very thick and the ends tapering, fitting
to each other so as to make a very compact and
solid tissue.
Notice whether the medullary rays present the same
appearance in the wood as in the bark. Test the
contents with iodine solution. Cells resembling
those of the medullary rays, but extending length-
wise of the stem, will be found. These constitute
the wood parenchyma.
THE STEM. 43
6. The pith comes last, and presents no difficulties.
7. Having compared the two sections throughout, go
over them again and see if all is clearly under-
stood. Make yourself familiar with all the details
of structure. Note what cells contain chlorophyll,
where starch occurs, the action of Schulze's solu-
tion on different parts, whether the sieve-tubes
show any peculiarities corresponding to their name,
how the cork originates, the manifest resistance of
the cork cells to reagents, and so on. Write a full
account, and introduce drawings wherever they are
required to make the description clear.
8. Finally cut tangential longitudinal sections, and
compare with the preceding.
III. Stem of Indian corn. Cut thin transverse sections.
Examine first with the low and afterwards with the high
power. The following parts are seen :
1. The epidermis and sub-epidermal tissue, forming a
continuous peripheral zone of thick-walled cells.
2. Fibre-vascular bundles, more numerous near the out-
side of the stem.
3. Fundamental tissue, consisting of large cells similar to
those composing the pith of the apple-tree stem.
IV. To understand these parts it will be necessary to
compare them /carefully with the same structures as seen
in longitudinal section. Accordingly, with both trans-
verse and longitudinal sections on the slide, study each
part in detail.
1. Observe the epidermis from both points of view.
Draw a few cells.
2. The fibro-vascular bundles present a somewhat com-
plicated structure. They are bounded externally
44 STUDY OF COMMON PLANTS.
by strong bands of thick-walled cells, composing
the so-called bundle-sheath, which may be continu-
ous, or thinned out on the sides of the bundle.
The bundle itself presents two parts for study : first,
the xylem, or wood, which includes the two conspic-
uous pitted vessels (recognized by their very large
openings), and the parts immediately adjacent ;
and second, the phloem, or bast portion, marked
by the peculiar appearance of its elements on
transverse section, its small cells being fitted in at
the angles between larger ones in such a way as
to give the effect of mosaic work.*
Studying first the xylem, on both transverse and
longitudinal sections, we find that it consists of
a. The large pitted vessels already noticed. Ex-
amine their structure carefully, observing par-
ticularly the remains of the partition walls in
the form of heavy rings, indicating the origin
of the vessels in rows of cells placed end to
end. One or more smaller vessels lie between
them, and a little nearer the center of the
stem. One of these is conspicuously marked
by heavy thickenings in the form of rings, and
is called an annular vessel. Frequently the
surrounding tissue is absorbed, leaving only
the rings of the annular vessel to mark its
place.
b. Thick-walled elements lying between the large
pitted vessels.
c. Elements with thinner walls surrounding the an-
nular vessel. Some of these, as already stated,
have disappeared, leaving an irregular open
space.
THE STEM. 45
The two sorts of elements that compose the phloem
are easily recognized on both transverse and
longitudinal sections.
a. The sieve-tubes are large, with nearly or quite
transparent contents, and here and there a per-
forated transverse septum looking like a sieve.
b. The smaller cells placed at the angles of the
sieve-tabes are the cambiform, or companion,
cells. Their thicker contents, smaller diame-
ter, and the absence of sieve-plates at once dis-
tinguish them from the preceding.
Having identified all the parts that have been
named, study them closely, and after you have
become perfectly familiar with the position and
structure of the different elements, draw and de-
scribe them. Meantime, look for any additional
features to which your attention has not thus far
been specially directed. See if you can recognize
the protophloem, a small group of rather indistinct
cells lying between the phloem and the bundle-
sheath.
Study, too, more carefully, the structure of the sieve-
tubes. Try the effect of picric aniline blue on
these and other parts of the bundle. Apply
Schulze's solution to other sections, and phloro-
glucin (followed by hydrochloric acid) to still
others, and note the results. What parts of the
bundle are lignified? How about other parts of
the stem ?
3. The fundamental tissue. Examine the large cells
composing the tissue, using both transverse and
longitudinal sections. Ascertain whether the large
cells of which it is made up present the same
46 STUDY OF COMMON PLANTS.
appearance and structure in all parts of the stem.
Test the contents for starch.
V. Having become acquainted with the minute anatomy
of the stem, study it from a mechanical point of view,
endeavoring to ascertain whether the thick-walled me-
chanical elements are grouped in such a way as to secure
strength with economy of material. Notice the disposi-
tion of the heavy sub-epidermal tissue in a continuous
hollow cylinder, the arrangement of the fibro-vascular bun-
dles, and the way in which the elements composing the
bundle-sheath are distributed.1
VI. Stem of white pine. The structure of the stem of
conifers presents various interesting peculiarities, but tho
arrangement of the parts and mode of growth are nearly
identical with those of dicotyledonous stems, and, moreover,
have been so fully treated in a number of laboratory guides
as to render it unnecessary to repeat directions for their
study. The student is recommended, however, to carry
out substantially the same plan of work on the stem of the
white pine as is outlined in the section on the Scotch pine
in Arthur, Barnes, and Coulter's Plant Dissection.
VII. Cambium. Nearly all woody species in temperate
regions of the globe form distinct annual rings which
mark the growth of the wood from year to year. In order
to understand the process a study of the cambium should
be made. Shoots of the white pine four or five years old are
suitable for this purpose. They should be cut during the
season of active growth, say from June to August, and
placed in alcohol. If properly hardened, transverse sec-
tions may be obtained that show very perfectly the new
wood and bark formed by the division of the delicate
1 Cf. Strasburger, Practical Botany, p. 88, and footnote.
THE STEM. 47
cambium cells. Test for lignin, and study the mode of
development of the wood.1
PHYSIOLOGY OF THE STEM.
Protection.
I. Examine under a lens the stem of the cultivated
verbena, primrose, and other plants from the greenhouse.
II. Mount portions of the epidermis of each in water,
and examine with the compound microscope. Draw and
describe the various epidermal appendages.
III. Make a careful study of the protective arrange-
ments of the common thistle, teasel, honey locust, cactus,
and blackberry. Ascertain the morphological character
of their various protective structures.
IV. Examine various woody stems, such as those of the
hickory and oak. Notice '
1. The thickness of the bark.
2. How it accommodates itself to the growth of the
tree.
V. Enumerate any other means that you have observed
by which the stems of plants are protected.
Mechanical Support.
I. Study the arrangement of the wood elements of the
stem of the common elder. Compare it with a stalk
of wheat ; with the stem of a palm. Is the material
economically employed ?
II. Make a transverse section of the stem of coleus.
Examine with the low power of a compound microscope.
1 In connection with his study of the structure of stems, the student
should read Gray's Structural Botany, pp. 67-82.
48 STUDY OF COMMON PLANTS.
Draw an outline sketch, locating the position of the me-
chanical elements.
III. Cut through an old tendril of a grape-vine. Notice
the disposition of the wood elements. Test its strength.
IV. Study under the compound microscope the bast
fibers of basswood and other common plants.
V. Write a brief account of what you have ascertained
regarding the mechanical arrangements for the support of
the plant. Read Goodale, Physiological Botany, pp. 188-
194 ; Haberlandt, Physiologische Pflanzenanatomie, p. 96
et seq.
Transportation of Food in Solution.
I. Cut a short branch from a grape-vine. Immerse the
cut end in a colored solution, such as red ink. After
some time make transverse sections, and observe how far
and through what parts of the stem the colored fluid has
penetrated.1
II. Repeat the experiment, using a fresh leafy stem of
Tradescantia for the purpose. Place finely powdered
indigo in the water and allow the plant to be exposed to
sunlight. This time take the precaution to cut the stem
under water so as to prevent the entrance of air. If the
cut is made slanting, and the whole operation skillfully
performed, the particles of indigo can be seen under the
compound microscope as they enter the vessels of the
Tradescantia.
Storage of Food.
I. Cut a common potato in two. Make thin sections
from the exposed surface, and examine with the compound
1 On the ascent of water in woody plants, see H. Marshall Ward, Tim-
ber and Some of its Diseases, Chap. IV (Nature Series).
THE STEM. 49
microscope. Draw one or two cells with their contents,
taking care to show details of structure.
II. Examine in the same way sections from various
other underground stems, such as ginger, mandrake, etc.
III. Prepare sections from pieces of a dahlia "tuber"1
that have lain in commercial alcohol for some weeks.
Draw a few cells, showing the peculiar sphere-crystals of
inulin.
IV. In some stems, as, for example, an onion bulb, sugar
is stored. This may be tested for in the way described by
Strasburger, Practical Botany, p. 48.
•
MODIFIED STEMS.
I. Make a thorough study of the common potato, ob-
taining for the purpose a number of different varieties.
What reasons are there for considering it a stem rather
than a root? What are the "eyes"? Where are they
most abundant? Are they all alike? Find where the
potato was attached. Draw an outline and indicate by
a dotted line the direction of growth in length. Does it
ever branch? Cut a transverse section so that it will
pass through a bud. Indicate in an outline sketch the
position of pith, wood, and bark. Notice that the wood
has been reduced to a minimum. It appears to the naked
oye as a faint circular line.
Write a complete description, and discuss the mor-
phology of the potato. See Gray, Structural Botany, p. 59.
II. Study a collection of other modified stems in the
same way, endeavoring in each case to satisfy yourself as
1 This is really a root, but on account of its convenience it is selected
instead of a stem.
50 STUDY OF COMMON PLANTS.
to every morphological feature. The following and a
considerable number of additional species can usually be
obtained, — some at the florist's, others at the grocery, and
still others at the drug store : ginger, iris, geranium, onion,
crocus, Solomon's seal, aconite, calamus. Fresh indigenous
plants will furnish many more.
III. Examine specimens of as many of the following
genera as are procurable, and discuss their morphology:
Muhlenbeckia, Myrsiphyllum, Ruscus, Asparagus.
In such exercises, a hasty examination of external feat-
ures is by no means sufficient. Every species taken in
hand should be subjected to patient and thorough study.
Some of those named present difficulties that are not likely
to be overcome by a student who is unwilling to think.
GROWTH OF STEMS FROM BUDS.
I. Obtain, before they have opened in spring, well-
developed buds of lilac, maple, hickory, horse-chestnut,
Austrian pine, and other trees. Study them carefully
with regard to protective arrangements, taking account
of the structure and position of the bud-scales (imbri-
cated like the shingles of a roof), waterproofing, hairs ;
in short, whatever appears to contribute to the protec-
tion of the parts within. What part of the bud is best
protected ?
II. Study next the arrangement of the parts composing
the bud, taking first the buds of the lilac, and following
with those of the horse-chestnut and other trees. Remove
the bud-scales and undeveloped leaves in succession, and
lay them in radiating rows, following the order in which
they are placed in the bud.
THE STEM. 51
Is the arrangement of the parts of the bud advantageous
as regards economy of space ? Does it present any other
advantages?
Compare the last year's growth of the stem with the ter-
minal bud, bearing in mind that " a bud is an undeveloped
branch."
III. Examine all the marks on a horse-chestnut branch.
Three kinds of scars are to be seen ; namely, those left by
the foliage leaves, by bud-scales, and by flower-clusters.
Compare all these with each other and with what is seen
in the terminal bud, until you are thoroughly familiar with
the characters of the branch as they appear in the bud.
Carry out a similar study with the buds and branches of
other trees.1
IV. Place the cut ends of shoots of lilac, horse-chestnut,
apple, etc., in water, the latter part of winter ; keep them
in a warm room, changing the water frequently, and ob-
serve the unfolding of the buds. Notice the first observa-
ble changes as well as those occurring in later stages.
Record your observations in detail.
V. Compare the terminal buds of plants belonging to
different genera, e.g. Acer, Caiya, and Pinus, and deter-
mine whether each presents distinctive marks. Next,
compare the buds of the red, and sugar maple, noting
carefully all the differences. In the same way, compare
the buds of Austrian, Scotch, and white pine, of the black
walnut and butternut.
As opportunity offers, practice the identification of trees
in winter by means of buds and other parts.2
1 For an admirable study of the buds and branches of common trees,
see Newell, Outlines of Lessons in Botany, Part I. Ginn & Co.
2Cf.Poerste, Bot. Gaz., XVII (1892), p. 180.
52 STUDY OF COMMON PLANTS.
REVIEW AND SUMMARY.
The stems of plants exhibit certain inherited pecu-
liarities of form, structure, and habit. In some large
Fwm families, the mints, for example, the stem is
structure, square ; while in others, as the true sedges, it
is triangular. The cylindrical form, however,
which has important mechanical advantages in its favor,
is most common. Characteristic habits, manifested in
mode of growth or choice of surroundings, are also fre-
quently met with. Thus, the family to which the morn-
ing-glory belongs is particularly distinguished by its
climbing habit, the members of the water-lily family by
their aquatic habits, and so on. Structural peculiarities
are still more distinctive and far-reaching ; so that, as a
rule, we readily determine the class to which a plant
belongs by ascertaining the arrangement of the tissues
composing the stem.
The texture of the stem, as determined by the nature
of its elements, is often characteristic. Various families
Texture and °^ plants, as those to which the maple, oak,
duration, and willow belong, have woody stems ; while
others, as the pink and violet families and many others,
are herbaceous. The duration of the plant corresponds
rather closely to the nature of the stem. Woody plants
are perennial, living for an indefinite period, while herba-
ceous ones are commonly annual or biennial. These dis-
tinctions, however, are not to be pressed too far, since the
texture of the stem is subject to much variation, even in
the same species, and duration is greatly influenced by
climatic conditions.
While typical stems are distinguished by the various
characters already referred to, there are many others that
THE STEM. 53
have taken modified forms corresponding to special func-
tions that they have assumed. Thus many stems, Modified or
a large proportion of which are subterranean, derived forms,
serve chiefly as reservoirs of reserve materials, and in the
course of time have undergone striking modifications both
of form and structure. The tuber of the common potato
shows all the essential characters of a dicotyledonous stem
in the formation of buds, the concentric arrangement of
pith, wood, and bark, and in still other respects, but the
fibrous tissue has almost wholly disappeared, while the
cellular tissue has increased to such an extent as to give
the tuber the appearance of a monstrosity compared with
the ordinary branches of the same plant. Quite as strik-
ing changes are seen in branches that have taken the form
of spines and assumed the function of protection. Good
examples of these are the spines of the hawthorn and
other familiar plants. Even more remarkable modifica-
tions are presented in the leaf-like organs known as
cladophylls. In the case of the so-called smilax of the
greenhouses, the true leaves are inconspicuous scales,
while the cladophylls so perfectly simulate foliage leaves
as to deceive an inexperienced eye. Much caution is
necessary in studying the morphology of these and other
modified branches. Their position on the stem, structure,
and mode of growth, and any tendency they may exhibit
to become ordinary leaf-bearing shoots, are all to be taken
into account.
In their anatomical structure and mode of growth, stems
present well marked peculiarities, which, as already stated,
are sufficiently characteristic to admit of the Anatomical
ready determination of the great class to which ^™^e and
a plant belongs. The stems of a large propor- growth,
tion of monocotyledons are well represented by that of
54 STUDY OF COMMON PLANTS.
Indian corn. In this the fibro -vascular bundles are scat-
tered through the fundamental tissue so that there is no
Monocotyle- manifest distinction of pith, wood, and bark, and
dons, both here and in other members of the same
class certain mechanical arrangements of much interest
present themselves. In the stem of Indian corn a strong
cylindrical band of sclerenchyma is placed just beneath
the epidermis, a disposition of the mechanical elements
adapted to secure the greatest strength with the least
amount of material ; and the same principle is carried out
in the bundles themselves, the sheaths of which are much
thickened radially, thus aiding materially in preventing
bending of the stem, and also protecting the vessels and
other conducting elements.
The stem of dicotyledons presents a rather more com-
plicated structure. As seen in the apple shoot, which
may be taken as a representative, the pith,
wood, and bark are arranged concentrically.
In the bark, as a rule, three layers may be distinguished,
viz., outer bark or cork, middle bark or green layer, con-
sisting chiefly of large cells containing chlorophyll and
other materials, and inner bark or bast, characterized by
the presence of sieve-tubes, usually with bast libers and
some parenchyma. Between the inner bark and wood is
the cambium zone, which during the growing season is a
layer of delicate cells, by the multiplication of which new
wood and bark are produced. The Avood consists of the
large vessels, the openings of which are conspicuous on
transverse section, wood fibers which constitute the
greater part of its substance and give the wood its
rigidity, and the medullary rays, to which in many species
are added the wood-parenchyma cells. The pith consists
of large cells which commonly present no distinctive
THE STEM. 55
peculiarities. Since each year, in temperate regions, the
sterns of dicotyledons add a new zone of wood, it is
possible to determine the age of a tree by counting the
number of annual rings. Not infrequently the record
is obscured by irregular growth, due to drought and
other causes, but in general these rings are clearly defined.
In their mode of growth the stems of gymnosperms
agree with those of dicotyledons, but their wood elements
are peculiar, the wood being composed mainly
of elongated cells called tracheids, the radial
sides of which have numerous bordered pits, by means
of which they communicate with each other and with the
medullary rays.
The structure of stems corresponds with a number of
very important .functions performed by the elements that
compose them. Thus the epidermis, afterwards
replaced by cork, is protective, as is also the
bark, which on the trunks of most trees becomes greatly
thickened with advancing age. The medullary rays and
other parenchyma cells of wood and bark serve for storage
of various food products, and are also employed to a consid-
erable extent in conducting them from one part of the plant
to another. Bast and wood fibers serve a special purpose
as mechanical elements by which the stem is maintained
in its position, and enabled to resist forces that tend to
strain or fracture it. Finally the vessels and tracheids are
chiefly concerned in conducting water containing mineral
substances and air from the roots to the upper parts of the
plant, while the sieve-tubes of the inner bark store up
nitrogeneous food materials, and convey them to the points
where they are needed.
It will, of course, be understood that an adequate
account of the physiology of stems cannot possibly be
56 STUDY OF COMMON PLANTS.
condensed into such a summary statement as the fore-
going ; but it will at least serve to point out the important
parts played by the various elements of the stem as they
contribute, each its share, to the work of the whole. The
mechanical system is treated at length by Haberlandt,
Physiologische Pflanzenanatomie, pp. 96—143, and an ex-
tended review of the theories regarding the ascent of
water in the trunks of tall trees is given by H. Marshall
Ward, Timber and Some of its Diseases, Chap. IV.
THE LEAF. 57
V. THE LEAF.
MATERIAL KEQUIEED.
Leaves of as many kinds as are procurable. See suggestions under
"Systematic Description." Branches of basswood, elm, maple,
and horse-chestnut. Leafy plants of primrose, fuchsia, dandelion,
and geranium.
Leaves of hyacinth and English ivy.
Leaves of various hairy plants and of conifers, rushes and sedges, etc.
Leaves of different ferns and flowering plants called for under "Me-
chanical and Conducting System."
Specimens of Elodea Canadensis growing in water, and of Mnium or
other common moss.
Tropaeolum and other convenient plants growing in pots
A collection of modified leaves.
SYSTEMATIC DESCRIPTION.
Write a careful and complete description of the leaves
of ten or a dozen different plants, following, as far as it
proves serviceable, the schedule given below.
Some one has said that " there is no part of botany so
overwhelmed with cumbrous terminology as that which
relates to leaves." Nevertheless the really necessary
terms are easily learned, and the peculiarities expressed
by them are far from accidental. The form of the leaf, its
position on the stem, the venation and other structural
features are generally such as to secure the greatest effi-
ciency, and in studying these it is desirable to be able
to express one's self with exactness. The greenhouse or
58 STUDY OF COMMON PLANTS.
window garden, the drug store, collections of preceding
years, and seedlings raised in the laboratory will, even in
winter, furnish abundant material. The following may be
suggested as a partial list : English ivy, geranium, prim-
rose, verbena, rose, oxalis, maurandia, nasturtium, oak,
maple, elm, lily, Indian corn, hyacinth, amaryllis, arbor
vitse, hemlock, juniper, and different species of pines.
Schedule for Leaf Description.
1. Position. Radical 2 or cauline.
2. Arrangement. Opposite, alternate, whorled, fascicu-
late.
3. Relation to Stem. Petiolate, sessile, perfoliate,
sheathing, connate, decurrent, etc.
4. Stipules. Described as leaves. If absent, the leaf is
said to be exstipulate.
5. Form. Acicular, awl-shaped, linear, oblong, ellipti-
cal, oval, rotund, ovate, lanceolate, reniform,
obovate, oblanceolate, etc.
6. Apex and Base. For special terms see dictionary and
text-books.
7. Margin. Entire, serrate, dentate, crenate, sinuate,
irregular, lobed, cleft, parted, divided, etc.
8. Venation. Pinnate, palmate, parallel.
9. Surface. Glabrous, glaucous, pubescent, wooly, vil-
lose, hirsute, prickly, etc. (These terms apply also
to the surface of other organs.)
10. Compound Leaves. Pinnate, bi-pinnate, tri-pinnate,
palmate, bi-palmate, tri-palmate, pinnately or pal-
mately decompound, etc.
1 Gray's Lessons, Section 7, and illustrations of botanical terms in
Webster's International Dictionary should be consulted.
2 A misleading term, but fixed in the language.
THE LEAF. 59
LEAF ARRANGEMENT.
I. Take branches of basswood, elm, maple, and horse-
chestnut, and study the leaf arrangement. In winter the
position of the leaves of preceding years may be deter-
mined by the leaf -scars.
Are the leaves placed advantageously as regards expos-
ure to light ? Cf .- Lubbock, Flowers, Fruits, and Leaves,
pp. 103-114.
II. Compare other plants, e.g. primrose and fuchsia,
dandelion and geranium, with regard to this principle.
III. Try the effect of putting the leaves of one species
on the branches of another, without changing the leaf
arrangement.
MINUTE ANATOMY.
I. With a pair of fine forceps strip off a portion of the
epidermis of a hyacinth leaf. Mount in water and examine
under the high power of a compound microscope. Observe
1. The elongated epidermal cells destitute of chlorophyll.
2. The stomata, each with two reniform guard-cells con-
taining chlorophyll bodies. Draw.
II. Place a small portion of a leaf of the English ivy
between two pieces of pith, and, with a keen razor, cut a
number of transverse sections. Examine under the com-
pound microscope. Select a section that shows all the
structural details and draw accurately. Beginning with
the upper surface the section shows
1. The upper epidermis, consisting of a single layer of
thick-walled cells, destitute of chlorophyll.
60 STUDY OF COMMON PLANTS.
2. A layer or two of closely packed cells, with their
long diameter perpendicular to the surface of the
leaf, containing many chlorophyll bodies. These
constitute the palisade tissue.
3. Other chlorophyll-bearing cells essentially the same as
the preceding, but less regular in shape and more
loosely arranged, so that toward the lower surface
of the leaf large openings, intercellular passages,
occur. Some of these cells contain large stellate
crystals of oxalate of lime.
4. About midway between the upper and lower surface,
the veins, fibre-vascular bundles, cut either trans-
versely or at an angle, according to their direction
at the place where the section is made. The
thick-walled mechanical elements constitute the
bundle-sheath. The bundle itself is divided into
two adjacent parts, the xylem lying towards the
upper surface of the leaf, and the phloem towards
its lower surface. The tracheids of the xylem,
elongated tube-like structures, are easily recog-
nized.
5. The lower epidermis, similar to the upper, but with
stomata at frequent intervals. These are placed
so that each one forms an entrance to one of the
intercellular passages. (Sections of the stomata
are best studied in a hyacinth leaf.)
NOTE. — The different sections should be studied until the gen-
eral structure of the leaf is thoroughly understood. Every fact is
of physiological significance, and it is of the utmost importance
that the student should have a complete and clear knowledge of
the minute anatomy based on direct observation.
THE LEAF. 61
PHYSIOLOGY OP LEAVES.
Protection.
Leaves require protection against
1. Changes of temperature.
2. Drying.
3. Attacks of animals, fungi, etc.
4. Injury by wind and other meteorological agencies.
Cf. Lubbock, Flowers, Fruits, and Leaves, Chap.
VI ; Kerner, Flowers and their Unbidden Guests.
Some of the following observations are to be carried out
in the laboratory, while others are best conducted out of
doors.
I. Remove the epidermis from a portion of a hyacinth
leaf, or the leaf of some other fleshy plant. Notice its
texture, strength, and elasticity. After a time observe
any changes that have taken place in the part from which
the epidermis has been removed.
II. Examine the hairy covering of leaves of common
mullein. Compare other hairy plants. Examine micro-
scopically the hairs of mullein, verbena, rose geranium, and
other common species. Make a series of drawings illus-
trating the epidermal appendages of various leaves.
III. Study the leaves of the Austrian pine, common
juniper, and other conifers. Enumerate the protective
arrangements exhibited by them.
IV. Compare very young leaves of the oak, apple, or
other common tree, with older ones.
V. Many plants are protected by disagreeable or poi-
sonous substances stored in their foliage. Name any of
these that you know.
62 STUDY OF COMMON PLANTS.
VI. Some leaves exhibit remarkable "sleep move-
ments." What are these for? Cf. Darwin, Power of Move-
ment in Plants, Chap. VII.
VII. Other leaves exhibit equally remarkable "hot sun
positions." Of what use are these to the plant ? Cf. Wilson,
Contributions from the Bot. Lab. Univ. of Pa., Vol. I, No. 1.
Mechanical and Conducting System.
The skeleton or framework of the leaf serves to support
the delicate green tissue, holding it so as to expose the
largest possible surface to the sun, and, at the same time,
giving the whole structure sufficient rigidity, strength, and
elasticity to resist mechanical violence. It also serves to
conduct a constant supply of water and mineral substances
to every part of the leaf, and to convey away elaborated
food materials. It is only by keeping these principles in
mind that an intelligent study of venation can be made.
Cf. Sachs, Physiology of Plants, pp. 48-53.
I. Obtain the leaves of several ferns, e.g. Adiantum pe-
datum, Aspidium cristatum, Osmunda Claytoniana. Draw
an enlarged outline of a leaflet of one or more species,
showing the exact position of the veins.
II. Compare the venation of a number of monocotyle-
dons, e.g. Tradescantia, Alisma, Sagittaria, Pontederia,
Calla, Arissema, Smilax. Draw accurately one or more
leaves.
III. Examine the venation of the leaves of Catalpa,
Liriodendron, Fuchsia, and Nymphsea. How does it
compare from a mechanical standpoint with that of the
leaves previously studied ?
IV. Study critically the structure of the leaf of a black
oak or red oak. Measure the widest space you can find
THE LEAF. 63
that is free from veinlets. Do these end freely or anas-
tomose ? Is there any apparent advantage in this ?
Assimilation.
The chief and characteristic function of green leaves is
assimilation, that is, the production of organized food sub-
stances.
I. Examine the leaves of Elodea Canadensis under the
compound microscope. Study the form and position of
the chlorophyll bodies contained in the cells. Are they
equally numerous in all parts of the leaf ? Draw two or
more cells showing the chlorophyll bodies in place. Com-
pare with these the chlorophyll bodies of Mnium or other
common moss.
II. Take fresh leaves of the Elodea that has been
growing in a jar of water exposed to sunlight. Place
them in strong alcohol and allow them to remain until
they have lost their color and the alcohol has turned
green. Mount for microscopic study and test with iodine
solution. Starch should be found in the chlorophyll
bodies. It may be demonstrated still more easily in the
chlorophyll bands of Spirogyra and other filamentous
algse.
III. By an experiment best performed by the teacher
or by a pupil specially appointed, the necessity of light for
the production of starch, and the local nature of the pro-
cess of assimilation is demonstrated. Take a healthy
Tropseolum (u nasturtium ") growing in a flower pot, and
place it in the dark for two or three days. Test one of
the leaves for starch, which by this time should have
disappeared. Now place the plant where it will be exposed
to the bright sunlight, having previously covered a part of
64 STUDY OF COMMON PLANTS.
one or more of the leaves so as to exclude the light by
pinning flat pieces of cork closely on opposite sides. After
the plant has been in the light for a day or more, proper
tests show that starch has been formed in the parts of the
leaves exposed to light but is absent where they were
covered (except in the fibro-vascular bundles). Further
details are given by Detmer, Das pfiamenphysiologische
Praktikum, pp. 33-34 and 3T-38.
IV. Place an inverted funnel over a lot of Elodea,
growing in a glass jar, and push it down until the small
end of the funnel is beneath the surface of the water.
Fill a test-tube with water, stop it with the thumb, invert,
and (under water) bring the small end of the funnel into
it. Set the apparatus where it will be in bright sunlight.
Observe the bubbles of gas given off by the plant. After
enough has been collected in the tube, test for oxygen.
This may be done by lighting a match and blowing it out,
and then inserting it, while still glowing, into the test-
tube.
Y. The preceding observations show that starch is
formed in the chlorophyll bodies in the presence of sun-
light, and that during the process oxygen is given off.
By means of a simple experiment it may also be shown
that starch is not thus produced unless carbon dioxide is
supplied to the plant. The teacher will find the apparatus
figured and described by Detmer, Praktikum, p. 38, easily
made and entirely satisfactory.
Transpiration.
I. Take a quantity of green leaves and place them in a
wide-mouthed bottle. After a time observe the moisture
that has collected on its inner surface. Where has it
come from ?
THE LEAF. 65
II. Cut off a strong, well-developed leaf of a primrose,
immerse the blade of the leaf in water, and placing the
cut end of the petiole in the mouth, inhale forcibly. Do
you obtain any proof that the inside of the leaf is in com-
munication with the atmosphere ?
III. Take any leafy plant of convenient size that is
growing in a flower pot, cover the pot with a piece of
dentists' rubber, bringing it up around the stem of the
plant and tying it so that no water can be given off
except through the plant itself. Weigh the whole, and at
the end of twenty-four hours weigh again. To what is the
loss of weight due ?
IV. Vary the last experiment by employing different
kinds of plants, as, for example, some with leathery and
others with soft leaves ; also by placing some in the sun-
light and others in the shade, in the open air and in a
closed room. What are some of the conditions affecting
transpiration ?
Respiration.
Respiration is a function of every living cell. Hence
leaves are to be thought of as organs of respiration in so
far as they expose a very large number of active cells to
the atmosphere, although they do not really " correspond
to the lungs of animals." We may therefore employ
leaves to demonstrate the process of respiration, or we
may use flowers or germinating seeds.
Take three wide-mouthed bottles and fill each two-thirds
full, the first of fresh leaves, the second of germinating
peas, and the third of flowers. Cork and allow to stand a
few hours. Test the air in the bottles at the beginning
and close of the experiment by introducing a homoeopathic
vial containing limewater, also by inserting a lighted
match. What is the result?
66 STUDY OF COMMON PLANTS.
NOTE. — The student should carefully consider what is taking place in
the cells of green leaves, inasmuch as a great deal of confusion has arisen
through lack of clear conception and expression. Since they respire like
other parts of the plant, leaves absorb oxygen and give off carbon dioxide
both day and night. On the other hand, as organs of assimilation, they
decompose carbon dioxide in the sunlight, giving off oxygen and employ-
ing the carbon in the production of starch. A complete discussion of the
subject would require much space, but the fundamental facts are as
stated above, and should be firmly fixed in mind.
MODIFIED LEAVES.
When some other function than that of assimilation
becomes predominant, leaves exhibit marked, and in some
cases extremely peculiar, modifications.
I. Examine shoots of the common barberry. Determine
the morphology of the spines and give reasons. Compare
the spines of the common locust. Are they the same
morphologically as those of the barberry ? Examine dif-
ferent species of cacti and determine the morphology of
the parts.
II. Study the tendrils of such of the following plants as
can be obtained and ascertain which of them are to be
classed as leaves or parts of leaves: Smilax rotundifolia,
Cobcea scandens, Adlumia cirrhosa, Echinocystis lobata,
grape-vine, pea, cucumber, etc. Note particularly any cases
in which only partial modification has taken place. Cf.
Darwin, Climbing Plants, Chaps. Ill, IV.
III. Leaves of insectivorous plants. See Special
Studies.
SPECIAL STUDIES.
I. Correlation of the forms of leaves with their position
on the stem. See Lubbock, Flowers, Fruits, and
Leaves.
THE LEAF. 67
II. Extent of leaf surface. Measure accurately the
superficial area of an average leaf of a geranium or
other common plant, and estimate its entire
leaf surface.
III. Generic and specific characters drawn from leaves.
IV. Variability. Compare the leaves of any individual
plant, a rose bush, for example, and observe their
different forms.
V. Leaves of insectivorous plants. Drosera rotundifolia
is widely distributed and is easily cultivated in the
laboratory. It is a most valuable plant for pro-
longed observation and experiment. Cf. Darwin,
Insectivorous Plants.
REVIEW AND SUMMARY.
The leaf is the most characteristic, and, in some respects,
the most important part of the plant. The venation and
various peculiarities of form and structure are .
^ A cnaracter-
usually sufficient to indicate at once the class, isticpartof
and not infrequently the genus or species to thePlantl
which a plant belongs. Even those who have had no
special botanical training readily distinguish the oak,
willow, maple, and various other plants by the leaf alone.
Hence in determining relationships special attention is
given to characters drawn from leaves, and it becomes
necessary to define these with care and precision. Physio-
logically, too, the leaf is engaged in work peculiar to
plants, work of a nature that cannot be performed by
animals, and upon which they are dependent for their
continued existence on the globe. A clear conception,
68 STUDY OF COMMON PLANTS.
therefore, of the general facts of leaf structure and physi-
ology is essential to an understanding of some of the most
fundamental facts of biological science.
Beginning with form and position, we have seen that,
as a rule, leaves are so constructed and placed as to secure
Form and ^ie exposure of a large surface to the air and
position, light. The blade of the leaf is raised on a
petiole whenever this is necessary to more readily accom-
plish the end to be attained. Furthermore, the position of
leaves on the stem is such as to aid in securing the great-
est exposure. If we inspect a large tree in full foliage,
such as a maple or bass wood, it will be seen that the leaves
are placed so as to result in a minimum of interference
with each other. It will also be noticed, as Sir John
Lubbock points out, that there is a manifest correlation
between the form of the leaves and their arrangement on
the branch, so that in many cases it would be a decided
disadvantage to replace the leaves of one species by those
of another unless the leaf arrangement were changed.
Further, an examination of buds that have not yet opened
shows that the leaf arrangement is such as to economize
space. These two principles, compact disposition in the
bud, and a position on the stem that will secure full expos-
ure of leaf surface, are the determining factors in the
arrangement of leaves.1
An examination of the anatomical structure of an ordi-
1 Incidentally it results that the leaf arrangement of many plants is so
definitely fixed that it may be expressed by a mathematical formula.
Phyllotaxis, however, as usually presented, is a curious rather than a
fruitful study. "We must now acknowledge that there is no general
law which can be formulated for the arrangement of the organs on a
parent axis ; that, on the contrary, according to circumstances in each
case, special causes determine whether the relations of position turn out
to be this or that." — SACHS, Physiology of Plants, pp. 500, 501.
THE LEAF. 69
nary foliage leaf shows that both surfaces are protected by
an external layer of cells constituting the epi- ^. .
dermis. The outer wall of the epidermal cells structure,
is commonly thickened, and by taking on a EPldemis>
layer of cutin or wax becomes nearly or quite impervious
to water. The leaves of some plants, particularly of species
growing in tropical regions, have more than one layer of
cells composing the epidermis, thus securing more efficient
protection. The cells of the epidermis are, for the most
part, destitute of chlorophyll, but contain a large quantity
of water which is absorbed as required by the delicate cells
in the interior of the leaf. Additional protection is often
afforded by hairs which thickly cover the leaves of many
species, particularly those growing on the steppes and
other parts of the globe where vegetation is subject to
sudden, and extreme changes of temperature. Finally,
protection is not infrequently secured by diminishing the
amount of leaf surface, as seen in many shrubs, and in
desert grasses and sedges with cylindrical leaves.
Communication with the interior of the leaf is secured
by means of numerous openings called stomata. These
are provided with guard-cells, commonly of the
, . ' , , . \, , - Stomata,
same general lorm as those ot the hyacinth leaf,
which act as a valve, opening in sunlight while the leaf is
at work and closing, or partially closing, at' night. The
mechanism, apparently simple, is, in reality, rather diffi-
cult of complete explanation.1 The essential fact is that
by means of the stomata a free interchange of watery
vapor and gases between the interior of the leaf and the
surrounding atmosphere is effected, and that by means
of the guard-cells this interchange is obstructed when the
external conditions are unfavorable.
1 Cf . Sachs, Physiology of Plants, pp. 248-251.
70 STUDY OF COMMON PLANTS.
The internal structure of the great majority of leaves
is essentially the same as we have seen in the English ivy.
Fibro-vascu- The midrib and veins, composed of fibers and
lar bundles, tracheids, present a strong frame-work by means
of which all the parts are supported, and which also serves
as the conducting system of the leaf. The green parts
consist of chlorophyll-bearing, parenchyma cells, the chief
function of which is the manufacture of organized food
substances. An extended comparison of the leaves of
Assimilating many species of plants shows several interesting
cells. arrangements for bringing the assimilating cells
into an advantageous position as regards the light. In the
first place, the leaf itself " turns towards the light," i.e.
places itself so that the upper surface is perpendicular to
the incident rays. In the second place, the palisade cells
are themselves nearly perpendicular to the leaf surface, a
position in which their contents are brought into relation
with the light, without, however, cutting it off entirely
from the cells below. Finally, the chlorophyll bodies
vary their position in the cells according to the intensity
of the light, ranging themselves so as to expose as large a
surface as possible when the illumination is feeble, and a
less surface when it is too intense.1 In addition to these
arrangements with reference to light, the assimilating cells
are grouped in such a manner as to facilitate the convey-
ance of water to them by the fibro-vascular bundles, and
the removal of elaborated food substances through the
same channels.2
It is thus seen that the leaf is an extremely delicate
organ, adapted to the performance of certain important
functions. Their first and most characteristic function
1 Sachs, I.e., p. 617 et seq.
2 Haberlandt, Physiologische Pflanzenanatomie, p. 184 et seq.
THE LEAF. 71
is the formation of organic food products out of the crude
substances taken in from the atmosphere and Functions.
soil. In the presence of sunlight starch is Assimilation,
produced in the chlorophyll bodies. The materials from
Avhich it is formed are carbon dioxide, obtained from
the atmosphere, and water brought up from the roots.
The starch accumulates in the daytime in the cells where
it is formed, and afterwards is conveyed away in a soluble
form to the various reservoirs of reserve materials. Simple
experiments have shown the conditions under which the
formation of starch takes place and the attendant phe-
nomena. The rapid evolution of oxygen seen when a
water plant is allowed to stand in 'bright sunlight is at
once checked when the vessel containing it is brought
into the shade. The oxygen is given off in the formation
of starch arid this process ceases when light is wanting.
Again, if the water in which the plant is growing is boiled
so as to expel the carbon dioxide, it is observed that the
evolution of oxygen ceases as in the preceding experiment,
but for a different reason. The carbon dioxide being
wanting, the leaves are deprived of the carbon necessary
to the production of starch.
Water in relatively large quantities is required to carry
to the leaf, and to the other parts of the plant, the sub-
stances used in the formation of starch and Transpira-
other products. The surplus water is evapo- tion'
rated by the leaves. By simply weighing at stated inter-
vals a plant arranged so that evaporation can take place
from no other part, it is found that large amounts of
watery vapor are given off through the leaves. Transpira-
tion, then, or the evaporation of water, is another important
function of leaves, since the water thus given off is the
vehicle of transportation of the various substances used by
the plant,
72 STUDY OF COMMON PLANTS.
Still another function which the leaf shares with other
living parts of the plant, and which is characteristic of all
living cells whether plant or animal, is that of
Respiration, . _. I ,, ,
respiration. As we have seen, one ot the prod-
ucts of respiration, carbon dioxide, is easily demonstrated
by testing with limewater the air within a bottle contain-
ing a quantity of green leaves. The abundant precipitate
of carbonate of lime shows that the leaves are giving off
carbon dioxide in considerable quantity, and as this is true
whether the experiment is performed in the daytime or at
night, we infer that respiration is going on continually.
It should be said, however, that, contrary to a widely
spread popular belief, the quantity of carbon dioxide
exhaled by plants is so small in comparison with what is
given off in animal respiration that it may be disregarded
in connection with the question of keeping house plants.
They are a decided advantage in the home from a sanitary,
as well as aesthetic, point of view.
The chief functions of the leaf, then, are
1. Assimilation, or the production of organized material.
2. Transpiration, or the evaporation of water that has
served as a vehicle for the transportation of crude sub-
stances.
3. Respiration, a process common to all living things.
The first of these takes place in sunlight, or its equiva-
lent ; the second is most active in the daytime, but is not
limited to it ; and the last continues both day and night,
as long as the leaf is alive.
We have learned in our study of the barberry and a
number of other familiar plants, that leaves are subject to
various modifications corresponding to other than their
ordinary functions. These modifications are not infre-
THE LEAF. 73
quently so profound that it becomes a matter of no little
difficulty to pronounce upon the morphological Modified
character of a particular structure. Spines leaves-
and tendrils, for example, may represent either leaves or
branches. The morphological character of bud-scales, on
the other hand, is usually recognized at once from their
position, structure, and especially from the various transi-
tional forms by which they are connected with ordinary
leaves. Though often puzzling, the morphology of modi-
fled leaves is always an exceedingly interesting and profit-
able study.1
1 Cf. Gray, Structural Botany, pp. 110-118.
74 STUDY OF COMMON PLANTS.
VI. THE FLOWER.
MATERIAL REQUIRED.
Flowers of white Trillium, T. grandiflorum, Salisb. Other species may
be used.
Cultivated Fuchsia. Specimens must be selected that have not become
double.
Several pots of cultivated primroses in flower, some specimens with
long- and others with short-styled flowers.
Various wild flowers, or cultivated kinds that have not undergone
modification, may be substituted for the preceding.
TRILLIUM. T. grandiflorum, Salisb.
I. Study first the morphological characters.1
1. Is the flower complete, that is, are the calyx, corolla,
stamens, and pistil all present ?
2. What is the numerical plan as indicated by the num-
ber of sepals, petals, stamens, and carpels ?
3. Is the flower regular ?
4. Is coalescence to be observed in the members of any
whorl ?
5. Describe in detail each part of the flower, noting
shape, color, and other features.
II. Make a transverse section of the ovary. Draw it
sufficiently enlarged to show all the parts clearly. Note
particularly the form, position, and place of attachment
1 Read Gray, Lessons, pp. 79-117.
THE FLOWER. 75
of the ovules, and make out as much of their structure as
possible.
III. Construct a diagram of the flower.1
NOTE. — A correct diagram necessitates a careful study of the relation
of every part of the flower to every other part. It should be drawn with
geometrical precision, representing the parts of each whorl so as to show
their number, arrangement, relation to other whorls, and to some extent
their union or separation. Properly constructed, such diagrams serve
an important purpose by facilitating the comparison of the permanent
morphological features of flowers of the same and different families.
IV. Ascertain whether the. flower manifests any physio-
logical adaptations.
1. Is there anything protective in its form, position, or
structure ?
2. Enumerate its attractive features.
3. Is there anything to indicate whether cross- or self-
fertilization takes place ?
NOTE. — A satisfactory answer to this question may require
more experience than the pupil has yet attained. It involves
close observation of any peculiarities that seem to favor the visits
of insects or other agents of fertilization, such as grooves, guiding
lines, the presence of nectar, and so on.2
FUCHSIA. Fuchsia coccinea, etc.
I. Note carefully all external features, such as
1. Position of the flower and its direction, erect or
drooping. Compare with the flower buds.
2. Color of different whorls.
3. Union of parts
a. Of the same whorl.
b. Of different whorls.
1 Cf. Gray, Lessons, p. 82, footnote ; also Eichler, Bluthendiagramme.
2 Cf . Miiller, Fertilization of Flowers.
76 STUDY OF COMMON PLANTS.
4. The extremely long style.
5. Relative position of anthers and stigma.
6. Numerical plan.
II. Make a clean transverse section of the ovary.
Examine under the dissecting microscope. How many
carpels are there ?
III. Draw the section, taking care to represent accu-
rately
1. The position of septa and placentae.
2. Attachment and form of ovules.
IV. Make an exact longitudinal section and draw it in
outline. Note particularly
1. The conspicuous nectary.
2. Presence or absence of nectar.
3. The insertion of the filaments and their direction, so
placed as to bar out unwelcome visitors.
V. Measure the length of the calyx tube. Is the nectar
accessible to bees and similar insects ?
VI. Construct a diagram.
VII. Review the whole and describe in detail.
PRIMROSE. Primula veris, etc.
I. Study the morphological characters, such as
1. The numerical plan.
2. Regularity.
3. Symmetry.
4. Coalescence of parts.
5. Structure of ovary.
II. Construct a diagram.
THE FLOWER. 77
III. Note all protective and attractive arrangements.
IV. Compare flowers of a number of different plants
with regard to the position of the essential organs. Notice
1. The length and insertion of the stamens.
2. Length of style.
3. Form and structure of the stigma.
4. Any other particulars in which the long- and short-
styled forms differ.
V. Make longitudinal sections of the two forms and
sketch in outline. Read Darwin, Different Forms of
Flowers on Plants of the Same Species, Chap. I.
NOTE. — It will, of course, be understood that an acquaintance with
many more species will be necessary in order to obtain a general concep-
tion of the morphology of the flower, and an adequate knowledge of its
physiological adaptations. Accordingly, similar studies of other flowers
may be made before proceeding farther, or this may be postponed until
the families of flowering plants are taken up. In any case the student
should now read carefully Gray, Lessons, pp. 79-109, or the equivalent
part of the Structural Botany, by the same author. He should also make
a constant practice of referring to Miiller, Fertilization of Flowers.
POLLEN, OVULES, EMBRYO.
I. Examine with the compound microscope the pollen
of a number of different plants, such as pine, lily, pump-
kin, mallow, and others. Compare the grains as to size,
shape, and surface. Notice whether those disseminated by
the wind are characterized by different features from those
that are carried by insects or birds. Draw and describe.
II. Sow various kinds of pollen in watch glasses con-
taining sugar solution (3 to 20 per cent). At intervals of
a day or less transfer a few grains to the glass slide with
a camel's-hair brush and examine microscopically. Some
78 STUDY OF COMMON PLANTS.
of them will soon show formation of pollen-tubes. Draw
them in different stages of development.1
III. Cut transverse sections of the ovary of Trillium at
the time the flower is fading and at subsequent periods.
Under the compound microscope study the ovules in
different stages of growth. Notice
1. The anatropous form of the ovule.
2. Its two coats distinctly marked at the apex.
3. The nucellus, or mass of tissue making up the body
of the ovule.
4. The micropyle, a canal leading from the apex of the
ovule to the nucellus.
Draw and describe.
IV. Prepare similar sections of the ovary of Fuchsia,
Begonia, and various other plants, studying carefully, as
before, the structure of the ovule. Some of these will
show, lying within the nucellus, the outlines of the embryo-
sac, a large cell in which the embryo is subsequently
formed. Clearing with potash solution facilitates the
observation. Indian-pipe, Monotropa uniflora, L., when
it can be obtained, is an extremely favorable species for
the study of the embryo-sac and the structures contained
in it.2
V. Take a flower-bud of shepherd's-purse, Capsella
Bursa-pastoris, Mcench, and under a lens remove the floral
envelopes. Open the ovary and dissect out the ovules.
Treat on the slide with dilute potash solution and apply
light pressure to the cover glass. If a series of younger
1 For further hints as to culture methods, cf. Strasburger and Hill-
house, Practical Botany, p. 320 c ; Halsted, Bot. Gaz. XII (1887),
p. 287.
2Cf. Strasburger and Hillhouse, I.e., pp. 327-337.
THE FLOWER. 79
and older specimens are prepared in this way, the embryo
in various stages of development can be satisfactorily
studied. Make a series of sketches showing as many of
these stages as practicable. Compare your own figures
with those of Hanstein.1 Write a brief account of the
development of the embryo of this plant as far as you
have observed it.
SPECIAL STUDIES.2
I. Morphology of stamens.
II. Morphology of the pistil.
III. Protection against unbidden guests.
IV. Dimorphism.
V. Mechanical devices favoring cross-fertilization.
VI. Changes in the ovule after fertilization.
REVIEW AND SUMMARY.3
In the preceding study we have found that a flower is
commonly made up of four distinct whorls, or circles,
calyx, corolla, stamens, and pistil. The parts part8 Of the
of the calyx are called sepals, those of the cor- floweri
olla, petals. The stamens are spoken of collectively as the
androecium, and the pistil (or pistils) as the gynsecium.
While in most flowers all the parts are present, there are
1 Goebel, Outlines of Classification and Special Morphology, p. 397.
2 Gray, Structural Botany, pp. 215-240, 251-268 ; Kerner, Flowers and
their Unbidden Guests; Darwin, Different Forms of Flowers on Plants
of the Same Species; Strasburger and Hillhouse, Practical Botany, pp.
311-337.
3 It will probably be better to postpone the review until the flowers of
a considerable number of families have been carefully studied. After
this has been done the pupil may profitably devote some little time to the
resume and references here given.
80 * STUDY OF COMMON PLANTS.
many species in which one or more of the whorls are
absent, and each is subject to more or less modification
of form and structure.
Morphologically the flower is to be regarded as a modi-
fied branch, the members of its different whorls corre-
Its morphol- spending to so many leaves. The most obvious
°sy- reasons for this view are that the flower has the
position of a branch; that the arrangement of its parts
follows more or less strictly that of the leaves on the stem ;
that the anatomy of leaves and floral structures is essen-
tially the same ; that transitions from ordinary leaves to
floral envelopes are of frequent occurrence ; and finally
that reversions of parts of the flower to a more primitive or
leaf -like form often take place.
It is convenient, and at the same time in accordance
with the viewrs now held regarding the actual evolution of
Typical plant life, to take some such flower as that of
flower, the Trillium as a pattern or "typical" flower
with which to compare others. The Trillium, as we have
seen, has three distinct green sepals, three petals, two
whorls of stamens of three each, and a pistil composed of
three parts, each part called a carpel. We may character-
ize our pattern flower, then, as having all the parts present,
these parts distinct from each other, of the same form and
size in each whorl, and presenting throughout the same
numerical plan, most frequently three or five. In other
words, it exhibits completeness, distinctness of parts, regu-
larity, and symmetry.1
The flowers of most plants differ in one or more respects
from such a typical flower as has been described. Never-
1 The flower of Trillium departs slightly from the ideal typical flower
in the coalescence of the three carpels to form the compound ovary. Cf.
Gray, Structural Botany, pp. 176-178.
THE FLOWER. 81
theless a comparison of the flower of a given species as we
actually find it, is, as a rule, readily made with
- , . . Modifications,
tlie assumed type, and this comparison is a
necessaiy part of the morphological study of any flower.
In carrying out such a study it is found that flowers
may vary from the type in any one (or in more than one)
of its characteristic features. In the first place,
i r ,1 11- T <• i • Coalescence,
members ot the same whorl, instead 01 being
separate, may be more or less completely united. The
calyx of the primrose, the bell-shaped corolla of the cam-
panula, the united filaments of various members of the
pea family, and the compound ovary of the lily, are
familiar examples. Coalescence of parts is held by bota-
nists to indicate a higher development than has been
attained by flowers in which the parts remain free.
A still further step in the same direction is seen in the
union of contiguous parts of different circles. Thus the
flower of the Fuchsia has the calyx-tube so
, . , , .„ Adnation,
united with the ovary as to make it appear as if
inserted on its summit, and both petals and stamens are
inserted on the calyx, the filaments showing very plainly
their union with the calyx-tube. The various degrees of
adnation furnish important characters that are constantly
employed in descriptive botany.1
Again, while the typical flower is regular, having all the
parts of a given whorl alike in size and shape, the flowers
of the more highly developed species, as a rule,
T i j • 1 -4- rpi -, n Irregularity.
show marked irregularity. Ihe spurred corolla
of the violet, and the curiously irregular flowers of the
sweet pea, salvia, and snapdragon are striking cases. It is
believed that these are descendants of much simpler forms
1 Cf. Gray, Structural Botany, pp. 182-184.
82 STUDY OF COMMON PLANTS.
that in the course of an indefinite period of time have
gradually taken on shapes manifestly correlated with the
visits of insects or other agents by which pollen is carried
from one flower to another.
Many flowers have undergone the suppression of one or
more parts. In some cases a whole whorl is wanting, as
in the anemone, which is destitute of a corolla ;
Suppression, .
or several whorls may be lacking, as in the wil-
lows, the flowers of which are reduced to a single whorl.
Frequently, however, a part of a whorl only is wanting,
and in such cases it often happens that a rudiment, or
trace, of the missing parts remains to indicate a former
condition. In the common toad-flax, for example, there are
four perfect stamens and a trace of the fifth ; some of the
mints now have but two stamens, although five was the
original number ; and many plants, as the lupine and its
allies, otherwise on the plan of five, have the ovary reduced
to a single carpel.
The symmetry of the flower is interfered with, not only
by the suppression, but also by the multiplication of parts,
Multipiica- so that it not infrequently happens that the
tion. original plan, in some one whorl at least, is no
longer recognizable. The very numerous stamens of the
cacti will serve as an illustration.
The changes described are of great interest as indicating
actual steps in the developmental history of flowers. They
help us to see, if not fully yet in part, how such extraor-
dinary structures as those of a milkweed flower or an
orchid have come to be what they are.1
1 Lack of space renders it necessary to refer the student to a much
more extended discussion of the subject than can here be undertaken.
Cf. Gray, Structural Botany, pp. 179-209, which has been followed in
the main in the brief resume just given.
THE FLOWER. 83
As already intimated, the parts of the flower exhibit
the same general structure as that of the leaf, structure and
but with modifications corresponding to the Actions of
the several
special functions that each part fulfills. parts,
The calyx and corolla are protective, serving to guard
the parts within from frost and rain and the intrusion of
unwelcome visitors. They are also attractive, pioraienvei.
particularly the corolla, which is usually col- °Pes>
ored so as to attract bees and other color-loving insects.
They form, too, a part of the mechanism, often very pecu-
liar and interesting, by which pollination is effected.
The stamens are usually far more modified than the
floral envelopes. The thickened anther, corresponding to
the blade of the leaf, produces pollen, the active
agent of fertilization. The pollen consists of
rounded cells, the walls of which are variously thickened,
frequently beset with spines, and, in some instances,
winged, thus facilitating their conveyance by insects or by
the wind. The cell contents are protoplasm, with one or
more nuclei, and a considerable quantity of food material,
such as starch, oil, and sugar.
The pistil is simple or compound according as it is made
up of one or more than one carpellary leaf.1 The ovules,
which afterwards become the seeds, originate as
cellular outgrowths from the margins of the
carpel. An ovule, when fully formed, consists of a cen-
tral mass of cells, called the nucellus, around which one,
or commonly two, protective coats are formed, and within
which a cell, called the embryo-sac, arises. It is in the
embryo-sac that the young embryo is developed. An
opening between the coats, called the micropyle, leads
down to the nucellus. The parts as described at once
1 Cf . Gray, Structural Botany, p. 260 et seq.
84 STUDY OF COMMON PLANTS.
recall the seed, which is simply a fertilized and matured
ovule.
When pollen-grains have been brought by any agency
to the moist and receptive stigma of a flower of the same
species, they begin after a short interval to ger-
Fertilization, . T . n ^ i
minate. In germination pollen-tubes are pro-
duced, which rapidly elongate, growing through the loose
tissue of the stigma and downwards through the style until
they enter the ovary. Here they find their way to the
ovules, which they enter, one pollen-tube going to each
ovule and pushing its way through the micropyle, until its
end comes in contact with the nucellus and finally with
the embryo-sac. A portion of the contents of the pollen-
tube, including nuclear material, now passes into the
embryo-sac and unites with a cell in it, called the oosphere.
The oosphere now takes on a cell-membrane, increases in
size, undergoes division, and, as a result of still further
division and growth, produces the embryo. Other cells
are formed in the embryo-sac which rapidly multiply and
become the endosperm, a tissue often absorbed afterwards
by the growing embryo prior to germination. Meantime
the embryo-sac becomes many times its former size, while
the nucellus is crowded to the walls of the ovule and is
commonly absorbed, but sometimes remains as the peri-
sperm. The coats of the ovule are extended to keep up
with this increase in size, the testa takes on its character-
istic hard and usually colored condition, a further store of
food is deposited around or in the growing embryo, and
with the completion of these various processes the ovule
has become a mature seed.
The changes just described, together with some others
that chiefly affect the ovary, take place whether pollen
from the same flower or from another flower of the same
THE FLOWER. 85
species is applied to the stigma; but it has been proved
that, as a general rule, there are great advaii-
• , , J Pollination,
tages in having the pollen brought from another
flower.1 Accordingly, while self-fertilization is possible in
most plants, various arrangements exist by which cross-
fertilization is favored.
A number of external agents serve as efficient means of
pollination. The wind carries the light pollen of 'pine and
other trees to great distances, sometimes even External
hundreds of miles, insects of many different agents,
kinds are actively engaged in carrying pollen from one
flower to another, and humming birds visit a considerable
number of species. In comparatively few cases pollen is
conveyed to the stigma by the agency of water.
Flowers themselves show many remarkable adaptations
that favor cross-fertilization. The most important of these,
as discussed at length by Darwin and other Adaptations
writers, are the following: of flowers,
1. Diclinism, or the separation of stamens and pistils.
These are borne in different flowers, either on the same
plant, as in the hazel, oak, etc., or on different individuals,
as in the willows and poplars. In some families, as the
maples, both conditions prevail. Plants with staminate
and pistillate flowers on the same individual are said to
be monoecious, those in which the separated flowers are
on different individuals are dioecious, and those in which
either condition exists together with the production of
some perfect flowers are called polygamous. Of those in
which the separation is most complete, namely, perfectly
dioecious species, Darwin says, " About the origin of such
1 Cf . Darwin, Cross- and Self-fertilization in the Vegetable Kingdom ;
Miiller, Fertilization of Flowers.
86 STUDY OF COMMON PLANTS.
plants nothing is known." 1 This arrangement practically
necessitates cross-fertilization.
2. Dichogamy, or the maturing of stamens before or
after the period of receptivity of the stigma. When the
stamens shed their pollen before the stigma is receptive,
the dichogamy is proterandrous ; if, on the other hand, the
stigma is receptive before the pollen is shed, it is proter-
ogynous.. The former condition is far more common than
the latter.2
3. Prepotency of pollen from other flowers. It has
been found by experiment that pollen from another indi-
vidual is often decidedly prepotent over that produced by
the same flower. This is best shown by placing its own
pollen on the stigma of a flower, and after some hours
applying pollen of a different colored variety of the same
species. The plants, raised from seeds of flowers thus
fertilized show by the color of their flowers whether
crossing has taken place. Darwin found in a number of
cases that pollen of another individual was prepotent after
twenty-three or twenty-four hours.3
4. Heteromorphism. A considerable number of species
produce flowers of different forms. In various species of
Primula and Houstonia, certain individuals have long sta-
mens and short styles, while others have long styles and
short stamens. Such flowers are said to be dimorphic, while
those of loosestrife, Lytlirum Salicaria, L., which have
stamens and styles of three different lengths, are trimor-
phic. Both conditions involve the same principle and
favor cross-fertilization in a remarkable way.4
1 Different Forms of Flowers on Plants of the Same Species, p. 278.
2 Cf. Gray, Structural Botamj, p. 219, et seq.
8 Cross- and Self-fertilization, pp. 395, 396.
4 Cf. Darwin, Different Forms of Flowers on Plants of the Same
Species.
THE FLOWER. 87
5. Special mechanisms. Such peculiarly shaped flowers
as those of the lupine, sage, lady's-slipper, milkweed, and
many other plants exhibit special contrivances, often in
the form of an exquisitely arranged mechanism, by which
the flower is adapted to some particular visitor or class of
visitors, through whose agency it is fertilized. These are
described at length in various works, and we shall have
occasion to study some of them in detail as we take up
different families of plants.1
1 The student is given distinctly to understand that the foregoing
account is necessarily incomplete, and must be supplemented by careful
and intelligent reading of the references given, if even a fairly complete
comprehension of the subject is to be attained. It is by no means the
part of these exercises, with their brief summaries, to cover the subject
of botany, but to show the beginner how to go to work.
88 STUDY OF COMMON PLANTS.
VII. FRUITS.
MATERIAL REQUIRED.
Mature fruits of sugar maple. Pods of common locust.
Capsules of opium poppy and of Llnaria vulgaris, Mill.
Fruits of climbing bitter-sweet, Celastrus scandens, L. Cranberries.
A miscellaneous collection of fruits from the market and elsewhere.
Among1 the most easily procurable are the following : Peanut,
acorn, common plantain, coriander, colocynth, milkweed, black
pepper, juniper berries, raisins, sumac "berries," rose hip, fig,
date, banana, star anise, cardamom, cocoanut, apple, plum, mul-
berry, catalpa, spiraea, evening primrose, and mullein.
COMMON LOCUST. Robinia Pseudacacia, L.
I. Taking dry, unopened specimens, note all the ex-
ternal features, as form, surface, color, and texture. Are
there any remains of floral structures ?
II. Open the pod and draw in outline the inner surface
of one of the halves, showing the position, attachment,
and form of the seeds. Locate the funiculus and micropyle,
and indicate their position by letters and dotted lines.
III. Describe the structure and mode of dehiscence of
the fruit and classify it. How many carpels are there ?
POPPY. Papaver somniferum, L.
I. With uninjured commercial specimens note
1. The general external characters.
2. The peculiar stigma. Count the number of divisions.
3. Mode of dehiscence.
FRUITS. 89
II. Make a transverse section and examine the internal
structure. Ascertain
1. Where the seeds are attached.
2. Number and position of the placentae.
3. Number of carpels.
SUGAR MAPLE. Acer saccharinum, Wang.
I. Taking dried specimens, gathered the preceding fall,
notice
1. The form of the wings.
o
2. Their size as compared with the rest of the fruit.
3. The lightness and strength of the whole structure.
What do you infer as to the mode of dissemi-
nation ?
II. Make an outline sketch of one of the two halves,
mericarps, into which the fruit separates.
III. Soak some of the fruits in water, and after an
hour notice what changes have taken place. With a
sharp knife or scalpel remove the pericarp. How does its
outer part differ from the inner in texture? Has the seed
become wet? Describe the means of protection of the
embryo.
IV. Taking a mericarp that has soaked a longer time,
or better, one that has lain on the moist ground from
the time of its fall, remove the pericarp so as to expose
the seed in its natural position. Next remove carefully the
seed-coats and examine the embryo. Observe the way it
is folded together and the form of the radicle and coty-
ledons.
V. Classify the fruit.1
1 Cf. Goebel, Outlines of Classification and Special Morphology, p.
428 ; Gray, Structural Botany, Chap. VII.
90 STUDY OF COMMON PLANTSo
BUTTER- AND-EGGS. Linaria vulgaris, Mill.
I. Place some of the dry capsules in water and watch
them for a few minutes. Observe and record any changes
that take place.
II. Ascertain the following facts :
1. Number of carpels.
2. Position of placentae.
3. Mode of dehiscence.
CLIMBING BITTER-SWEET. Celastrus scandens, L.
I. Examine the dry fruits, noting the number, shape,
and position of the reflexed valves.
II. Compare specimens that have been soaked in water
an hour or more and note differences.
III. Ascertain the number of seeds and describe them.
They are surrounded by a brightly colored aril.1
IV. Classify the fruit and describe the mode of
dehiscence.
CRANBERRY. Vaccinium macrocarpon, Ait.
I. Note critically the external features, including the
presence or absence of floral envelopes. Can you deter-
mine by inspection of the fruit whether the ovary should
be described as superior or inferior?
II. Prepare transverse and longitudinal sections. De-
termine
1. The number of carpels.
2. Position and direction of seeds. Draw and describe,
1 Cf. Gray, Structural Botany, pp. 308, 309.
FKUITS. 91
CLASSIFICATION OP FRUITS.
After a thorough study of a few such fruits as the fore-
going, examine and classify a large number of easily pro-
curable sorts, selected so as to secure as great a variety as
possible. See list given above. Careful attention should
be given at the same time to their morphology. Endeavor
to ascertain in each case how many carpels there are, and
what modifications the parts forming the fruit have under-
gone. It is desirable to adopt some one classification and
adhere to it. That of Gray is, on the whole, the most
satisfactory.
SPECIAL STUDIES.1
I. Projection of seeds.
II. Arrangements for burying seeds.
III. Colors of fruits.
IV. Relationships indicated by fruits.
V. Variation as seen in cultivated fruits.
VI. Minute anatomy of the cherry.
VII. Development of the apple or some other common
fruit.
This last may be made an extremely interesting and
profitable study. Beginning with the flower of the apple,
cherry, or any of the common fruits, watch day by day the
changes that take place, keeping a full record of them
until the fruit is formed.
1 Botanical Gazette, Vol. VII (1882), pp. 125, 137 ; Vol. XII (1887),
p. 225 ; Lubbock, Flowers, Fruits, and Leaves, Chap. Ill ; Wallace, Dar-
winism, pp. 305-308 ; Darwin, Animals and Plants under Domestication,
Vol. I, Chap. XI ; Strasburger and Hillhouse, Practical Botany, p.
347 et seq.
92 STUDY OF COMMON PLANTS.
REVIEW AND SUMMARY.
After the process of fertilization has taken place, re-
markable changes occur aside from those of the ovule
Development already described. The corolla withers, and
of the fruit, the ovary increases in size, finally becoming the
fruit, which in ordinary cases is to be thought of simply as
the ripened ovary. In some species, however, the calyx-
tube forms a part of the fruit, and still other exceptional
forms of developmental history occur. The wall of the
ovary, which becomes the' pericarp, generally changes in
texture, becoming firm and leathery as in the bean, or
fleshy as in the cucumber, or partly fleshy and partly bony
as in the cherry, and so on. The pericarp often shows
three fairly distinct layers corresponding to the upper and
lower epidermis and intervening parenchyma of the car-
pellary leaf, the outer layer being known as the exocarp,
the middle, mesocarp, and the inner, endocarp. Thus, in
the peach, the skin is the exocarp, the fleshy part the
mesocarp, and the stone the endocarp. In the pod of a
bean or pea, the correspondence between the parts of the
pericarp and those of the carpellary leaf is still more
manifest. In many other fruits the changes that have
occurred render this relation less easily observed, and are
frequently still more fundamental in character. In some
cases in which the ovary is composed of several carpels,
only one develops, the rest becoming abortive ; in others
the ovary becomes divided by one or more septa, which
give the fruit the appearance of having arisen from a com-
pound pistil with more than the actual number of carpels.
These and other important features of the developmental
history of fruits are best understood by a careful com-
parison of their structure in different stages of growth
from the pistil to the mature condition.
FEUITS. 93
Many of the peculiarities just referred to find their expla-
nation in physiological adaptations, chiefly those connected
with protection and the dissemination of seeds, physiological
Attention has already been directed to these in adaptations,
our study of seeds, but they may now be briefly noticed
with more direct reference to the fruit. Fleshy fruits, par-
ticularly if brightly colored, are attractive to animals, and
are carried away by them in great numbers, often to very
remote places. One has only to recall the habits of birds
in distributing seeds of cherries, strawberries, and many
other fruits, to realize the importance of these common and
familiar but nicely adjusted relations. Other fruits, such
as nuts of various kinds, though less attractive externally,
are carried away by squirrels and other animals for the
sake of the abundant food stored up in them. Still other
fruits, such as the samara of the hop-tree and maple, have
the pericarp greatly modified in adaptation to dissemina-
tion by the wind, and a considerable number of dehiscent
fruits exhibit mechanical arrangements by which their
seeds are forcibly thrown to a considerable distance. Fre-
quently, too, the structure of the fruit is manifestly
adapted to secure the protection of the seed. The thick
and bitter outer covering of the walnut and its extremely
hard shell, the rind of the orange with its pungent,
aromatic oil, the extraordinarily multiplied and thickened
coverings of the cocoanut, and other arrangements of simi-
lar character, are so many means of protection against
attacks of animals, the penetration of water and fungous
germs, and injury from other destructive agents.
In systematic botany it becomes necessary, for 'the sake
of intelligible description, to employ some one of the
various classifications of fruits. At the same time, it must
be understood that such classifications are more or less
94 STUDY OF COMMON PLANTS.
artificial, and that their value is rather that of convenience
than as an expression of relationship. Nevertheless it is
Classification, the case many times that in a given group of
Mkated^by plants a certain kind of fruit prevails, not in-
fruits, frequently to the exclusion of all other kinds.
Thus the pepo is the fruit of the gourd family, the ache-
mum of the composites, and so on, so that by means of the
fruit alone it is often possible to determine the relation-
ship of the plant from which it came. Accordingly the
student is advised to familiarize himself with the various
kinds of fruits by a careful study and classification of such
a collection as that of the list in this exercise, and in his
subsequent study of special groups of plants to observe
how far the kind of fruit is characteristic. Such a mode of
procedure will give interest and meaning to what other-
wise is likely to be nothing more than a bete noire to the
beginner.
In closing our study of fruits we come back again to the
seed, with which we started, and it must already have oc-
Cycle of de- curred to those who are in the habit of stopping
flowering* ° to think, that the same plant appears at differ-
piants. eiit periods of its life under widely different
forms. The seed represents the plant in its period of rest,
but it is as truly the plant in this state as in its period of
highest activity. We may even hold, perhaps more accu-
rately, that a part of the seed — the embryo — strictly rep-
resents the entire plant, the parts around the embryo being
merely protective or food-supplying accessories that belong
in reality to the preceding generation.1 We have found it
best to study parts of many different species in order to
1 The theory of the alternation of generations and the details of
the reproductive process cannot well be discussed until the student is
acquainted with flowerless plants.
FRUITS. 95
obtain a general conception of the structure and cycle of
development of flowering plants, but if we were to take a
single seed, and watch its germination and every detail of
its subsequent life and growth, we should find its develop-
mental history a connected synopsis of what we have
learned from so many sources. This may be stated briefly
as follows: In the spermaphytes, or higher plants, the
embryo arises from a single cell, the ob'sphere, contained
in the embryo-sac. The embryo has all the essential vege-
tative parts of the mature plant, and in germination these
are unfolded, finally developing into root, stem, and leaf.
Certain buds of the plant in this later stage of its develop-
ment become ordinary branches, while others undergo ex-
traordinary modifications and become reproductive branches
or flowers. In due course of time the oosphere is formed
in the embryo-sac of the various ovules, and after fertiliza-
tion the same history is repeated in a subsequent genera-
tion. Later on in our work we shall see that plants lower
in the scale of life exhibit similar, though not identical,
phases of developmental history. Before proceeding to
these, however, we have first to study certain relationships
of the higher plants among themselves.
96 STUDY OF COMMON PLANTS.
VIII. SEAWEEDS AND THEIR ALLIES. ALG^B.
MATERIAL REQUIRED.
Green algse gathered in a fresh condition from different places.
Pains should be taken to secure the coarser, branching sorts,
common in running water, the fine, silky kinds that grow abun-
dantly in stagnant water, and the dull green felt that forms
on the damp ground and in pots in conservatories.
NOTE TO THE TEACHER. — The arrangement of families and higher
groups in the following pages is believed to indicate, as well as a lineal
arrangement can, their natural succession, and is that adopted by modern
botanical writers. In most preparatory schools, however, certainly in
those not fully equipped for microscopic work, the best results will be
attained by following a somewhat different order. After studying the
organs of flowering plants, it will be found advantageous to pass at once
to the Coniferae, then to the early flowering families of phanerogams,
taking them in the order that is most convenient, which will be deter-
mined chiefly by time of flowering and abundance of material. As a rule,
the cryptogams should be studied later, although in schools provided with
a full laboratory outfit the order followed in the book may be the best.
No attempt is made to treat all families alike. The aim is simply to
help the student in every case to ascertain existing facts and their mean-
ing. Observation should constantly be directed to the differences and
resemblances by which various degrees of relationship are determined.
The exercises on the Coniferse and Ranunculacese will serve to indicate
the prominence that may properly be given to this idea, which forms the
basis of vegetable morphology. On the other hand, observations of
distribution and physiological adaptations, too much neglected hitherto,
should receive their full share of attention. It is essential that careful
descriptions of the plants examined should be written, and that these
should be accompanied by sketches. The number of these will vary
according to circumstances and the judgment of the teacher, but they
are by no means to be omitted.
SEAWEEDS AND THEIK ALLIES. 97
SPIROGYRA. S. longata, qulnina, etc.
General Characters.
The soft, green material called " pond scum," growing
on the surface of still water, is usually made up largely
of Spirogyra, not infrequently several species together.
Notice
I. The color, varying according to conditions, so that
specimens from different places, or gathered at different
times of year, may present a wide range of shades.
II. The delicate and slippery feeling, reminding one of
silk when taken between the fingers.
III. The remarkable difference in size of the filaments
when examined with a hand lens, or even with the naked
eye, if specimens of extreme sizes are compared.
Microscopic Structure.
Mount in water and examine with the compound micro-
scope.
I. Observe that each filament is composed of a single
row of cells. Follow one of the filaments to the end.
Are the cells composing it of uniform diameter? Of
uniform length ? How does the terminal cell differ from
the others?
II. Study critically the cell structure.
1. Focus slowly and compare one cell with another
until you are satisfied as to their geometrical form.
Are they " rectangular " or cylindrical ?
2. Separate the cell-contents from the cell-membrane
by applying a plasmolyzing agent. Two per cent
98 STUDY OF COMMON PLANTS.
salt solution is suitable for this purpose. Watch
the process of plasmolysis (contraction of the proto-
plasm and its separation -from the cell-membrane) .
Sketch one or two of the cells showing the cell-
membrane in its place and the contracted proto-
plasmic contents.
3. Preparing a fresh slide, so as to have the cells in
their natural condition, study the cell-contents.
How many green bands, chlorophyll bodies, are
there in each cell? Change the focus slowly, and
follow a band from one end of the cell to the
other. What is its shape? Is its edge even or
irregular? Notice the rounded, highly refractive
bodies, pyrenoids, contained in it.
4. Treat with iodine solution, and ascertain whether
starch occurs in the cells. If so, does it stand
in any relation to the pyrenoids ?
5. Look for a nucleus. This is sometimes brought out
very plainly by the action of iodine. In some
species it may be seen with perfect clearness with-
out any treatment. Compare different specimens
until you know definitely
a. The position of the nucleus in the cell.
b. Its shape.
c. Whether it is connected in any way with other
parts of the protoplasmic contents. This is a
very interesting point, difficult to determine in
some species, but very obvious in others.
d. Its structure. A nucleolus will readily be found.
(The finer details of structure require special
methods not provided for in this course.)
SEAWEEDS AND THEIR ALLIES. 99
III. Draw one of the cells with great care large enough
to show its complete structure. This will require close
attention to details. Repeat, if necessary, until you are
satisfied that your drawing represents truthfully a Spiro-
gyra cell.
Describe fully what you have seen so far.
NOTE. — Possibly some things have escaped notice. The septa between
adjacent cells differ widely in different species. There are still other
points not likely to be observed except by comparing different forms.
Reproduction.
Spirogyra is reproduced sexually by zygospores and non-
sexually by cell-division.
I. By zygospores. These may be found in the summer
time in specimens that look faded or discolored. They
are not to be looked for in bright green material.
1. Observe the marked contrast presented by the conju-
gating filaments to those in the vegetative condition.
The filaments occur in pairs, one with empty cells,
the other containing in each of its cells a large,
commonly oval zygospore.
2. Notice the structure of the zygospore, with its heavy
wall and dense contents.
3. Compare different specimens, and try to make out the
way in which the zygospores have been produced.
Notice the connecting-tube by which the cells of
the empty filament are connected with those of the
one containing zygospores. See if there are any
cases in which it contains protoplasm. Look for
specimens in which instead of a complete tube there
are protuberances from the opposite cells of the
100 STUDY OF COMMON PLANTS.
two filaments. If the material is favorable, you
will be able by continuing such a comparison to
observe for yourself the successive stages in the
development of the zygospores.1
II. By cell-division. The nucleus undergoes a remark-
able series of changes, ending in its separating into two
new nuclei and the formation of a septum between them.
In this way a cell becomes divided into two "daughter
cells " which after attaining their full development divide
in the same way, the process continuing through a series of
generations.2
Spirogyra is one of the most abundant and widely
distributed of the green algae. It is always to be had, and
is one of the most satisfactory plants with which to begin
the study of the plant cell. Zj^gnema, recognized by its
stellate chlorophyll bodies, and Mesocarpus, in which a flat
plate takes the place of a spiral band, are both often found
with it. All of these, particularly Spirogyra and Meso-
carpus, are capable of almost unlimited use in the demon-
stration of fundamental facts of vegetable physiology.
The student will do well to read carefully what is said
of Spirogyra in the laboratory manuals, and consult the
references in Arthur, Barnes, and Coulter's Plant Dissec-
tion, and the recent periodical literature.
1 Cf. Strasburger, Practical Botany, p. 247 ; Sachs, Physiology o>
Plants, pp. 727, 728.
2 For details of the process, including nuclear changes, see Strasburger' s
admirable monograph, Ueber Kern- und Zelltheilung. Jena, 1888.
SEAWEEDS AND THEIR ALLIES, i ^ 1 J,
VAUCHERIA. V. sessilis, Yauch: ' '
General Characters.
Examine with a good hand lens the specimens that
have been gathered, some from fresh water, others from
moist soil in greenhouses. Notice
I. The coarsely filamentous appearance, and the matting
together to form a thick felt, when growing on the soil in
flower-pots.
II. The color. Compare with the bright green of some
of the finely filamentous sorts growing in water.
Microscopic Structure.
Mount some of the filaments and examine with the
compound microscope. Observe
I. The very large size of the cells, a filament, as a rule,
consisting of a single cell. Try to find the end of one.
Ascertain whether branches are formed.
II. The thick cell-wall. Run two per cent salt solution
under the cover glass, and see if the wall becomes more
plainly defined.
III. The cell-contents. These present considerable dif-
ferences, depending on the age of the plant, and the con-
ditions under which it grew. Good specimens show in
the thicker protoplasm next to the cell- wall
1. Chlorophyll bodies. Observe their shape.
2. Drops of oil. Apply iodine solution, and determine
whether starch also is present.
3. Nuclei. These require special treatment to be brought
out satisfactorily.1
1 Cf. Bower and Vines, Practical Botany, II, p. 76.
102 STUDY OF COMMON PLANTS.
Vaucheria is reproduced by oospores and also by swarm-
spores.1
I. By oospores. These are easily obtained from speci-
mens growing on damp earth, and may be satisfactorily
studied both in living and alcoholic material. Using first
the low power of the compound microscope, observe
1. The organs of reproduction generally growing close
together.
a. The cylindrical anther idium.
b. The obliquely oval oogonia, commonly two with
each antheridium. Draw.
2. The structure of both antheridium and oogonium.
Examine this more in detail, using the high power,
and, if practicable, having fresh material.
a. Early stages of development may be found. If
these are met with, make a series of sketches,
showing both oogonia and antheridia at dif-
ferent periods.
b. The process of fertilization should be observed, if
possible. It will probably involve the outlay
of considerable time, yet there are few plants
in which the process can be more satisfactorily
followed. It is even more striking in CEdogo-
nium, a plant closely related to Vaucheria, on
account of the large size of the antherozoids.2
II. By swarm-spores. These cannot always be had
when wanted, but are unusually large, and on account of
1 For other forms of vegetative reproduction, cf. Goebel, Outlines of
Classification and Special Morphology, p. 32.
2 For an account of the process and further directions, cf. Strasburger,
Practical Botany, pp. 252-254.
SEAWEEDS AND THEIE ALLIES. 103
their peculiarities are worth taking pains to secure. Stras-
burger recommends 1 that vigorous specimens of Vaucheria,
growing in running water, be obtained the day before,
placed in shallow vessels, and fresh water poured over
them. The swarm-spores are formed the following morn-
ing, and, on account of their large size, both their structure
and development are readily observed.
No further special directions will be needed beyond
those in the manuals referred to, which should be care-
fully read. As complete a study as possible should be
made of this plant, since it stands as a representative of
those algse in which the sexual reproduction has proceeded
a step farther than in Spirogyra, male and female cells
being distinctly differentiated. Many of these are also
reproduced by swarm-spores. These two modes of repro-
duction are so common that we expect, as a general rule,
to find the algae reproducing themselves both sexually and
non-sexually, a fact that continually presents itself in
studying other groups of plants, but not often in quite so
striking a way as here. The non-sexual process is a means
of rapid reproduction ; sexual reproduction, on the other
hand, commonly results, in the lower plants at least, in the
formation of a resting-spore by which the plant is carried
through various vicissitudes and dangers, and in which
by a mingling of the male and female elements in the
process of fertilization, certain other advantages, not yet
fully understood, are attained.
The brown and red algae grow in salt water in nearly all
cases, and are seaweeds properly so called. They present
many forms no less interesting than the green algae, but as
they will not be accessible to the great majority of those
1 Practical Botany, p. 250. See also Bower and Vines, Practical
Botany, II, pp. 78-80.
104 STUDY OF COMMON PLANTS.
who are likely to use this book their study has not been
introduced. The various text-books and manuals give the
necessary help for beginning their study.1
1 No provision is made in this work for the study of fungi, not because
they are unimportant, but because it is better on the whole that the
student should complete his preparatory course with the definite under-
standing that he knows nothing whatever about this vast and hetero-
geneous group.
MOSSES AND LIVERWORTS. 105
IX. MOSSES AND LIVERWORTS.
MATERIAL REQUIRED.
A collection of common mosses of different genera, e.g. Bryum,
Climacium, Mnium, Polytrichum, Cylindrothecium, Sphagnum,
and others. AVith care in selecting, and by gathering material
at different times, some specimens will be obtained in fruit,
others in the vegetative condition, and still others with arche-
gonia and antheridia.
A similar collection of liverworts, including representatives of the
genera Conocephalus, Lunularia, Riccia, Porella, etc.
MOSSES. Musci.
General Characters.
Without selecting one species for exclusive study, com-
pare the different kinds of mosses in the collection that
has been made, and ascertain what general characters they
have in common. Notice
I. Their choice of locality. By what does it appear
to be determined? Are the habits of the different species
alike in this respect?
II. Whether they grow separately or in tufts.
III. The differentiation of vegetative organs. Is there
a plain distinction of root, stem, and leaf? If so, is it
equally marked in the different species ?
IV. Differences of size, color, and other specific char-
acters.
106 STUDY OF COMMON PLANTS.
V. The fructification, — when fully developed a very
conspicuous part of the plant.
Rhizoids.
I. Examine the different species with reference to the
occurrence of roots. They are found to have the form
of hair-like bodies, root-hairs, or rhizoids. Where do they
arise ? Are they limited to any one part of the plant ?
II. Remove some of the rhizoids, mount in the usual
way, and examine under the compound microscope. Pre-
pare several slides, taking the root-hairs from different
species, and from different parts of the same plant for
comparison.
1. Notice first the color, mode of branching, and other
external features.
2. Study more closely the minute structure, observing
the form of the cells composing the rhizoids, the
character of their contents, and position of the
septa.1
3. Notice whether the younger cells of the rhizoids
differ from the older ones, and if so how. Also
whether exposure to different conditions, as a
greater or less amount of light, has any effect on
the character of the cells or their contents.
Stem.
I. Compare the stems of the different mosses, and observe
their differences of size and habit, contrasting the erect,
rigid stem of Climacium with the delicate, spreading
branches of Mnium, the minute forms of Barbula with
the coarse Polytrichum, and so on.
1 Cf. Sachs, Physiology of Plants, p. 30.
MOSSES AND LIVERWORTS. 107
II. Cut thin transverse sections of the stems of two
or three different species, and study them under the com-
pound microscope. Beginning with the outside, notice
1. The epidermis, consisting of a single layer of periph-
eral cells. Underneath this, in some of the
species, are similar, thick-walled cells, the whole
forming a cylindrical band of mechanical tissue.
2. The cortex, consisting of rounded cells, often con-
taining starch and oil.
3. The axial cylinder, an extremely simple form of fibro-
vascular bundle, occupying the center of the stem,
and made up of much narrower elements than
those composing the cortex. Longitudinal sec-
tions show that these are also much more elongated
than the cortical cells are. Observe also whether
they differ from the latter in the color of their
walls and the character of their contents.
Leaf.
I. Examine next the ordinary foliage leaves of the
different species, observing
1. Their differences of size, form, and other external
features.
2. Their relation to the stem. Are they stalked or
sessile? Is their arrangement on the stem alike
in the different species ?
3. The structure of an individual leaf, as far as this
can be observed under a good lens. Notice par-
ticularly the margins and midrib.
II. Study fresh and well-developed leaves, such as those
of new shoots of Mnium, with the compound microscope.
The cellular structure will be found beautifully distinct,
108 STUDY OF COMMON PLANTS.
the cells containing large and clearly defined chlorophyll
bodies. Notice their position in the cells ; does it appear
to be constant?
A little attention will show that the leaf is not a simple
plate of cells throughout. Examine the midrib and com-
pare with the axial cylinder of the stem.
III. Look for other kinds of leaves, scale leaves, of
frequent occurrence, especially on the lower part of the
stem, and perichaetial leaves, forming a rosette, usually at
the apex of fruiting stems.1
Fructification.
I. Taking any of the mosses in the collection that are
in fruit — several species if possible — observe
1. The slender stalk, seta, on which is borne
2. The capsule, containing spores.
Compare the capsules of different species as to size,
form, color, and other features.
II. Make a thorough study of the parts composing the
capsule, using the compound microscope when needed.
1. The calyptra, commonly a thin membrane covering
the apical part of the capsule ; rarely, as in
Polytrichum, a thick hairy cap. Notice the form,
differing in different genera.
2. The opercurum, in most genera a conical lid, fitting
closely to the end of the capsule, but thrown off
when the latter is fully ripe, thus permitting the
scattering of the spores.
3. Lightly covered by the operculum when it is in
place, but showing conspicuously when it is re-
1 For further suggestions cf. Arthur, Barnes, and Coulter, Plant .Dissec-
tion, p. 84 et seq.
MOSSES AND LIVERWORTS. 109
moved, the peristome, or circle of teeth surround-
ing the opening of the capsule. The peristome
presents a widely different appearance in the
different genera, and its structure requires careful
study. It consists of four, eight, sixteen, thirty-
two, or sixty-four teeth, plain, or variously cut and
ribbed, and often very hygroscopic. In a few
genera the peristome is wanting.
4. Within the capsule, the spores filling a cylindrical
space which surrounds a central mass of tissue
called the columella.
5. In some mosses, besides the parts already named,
there are to be observed the epiphragm, a thin,
membranaceous structure, stretching across the
mouth of the capsule ; and at the base of the
-capsule a swelling called the apophysis.
NOTE. — The structure of the capsule should be studied in detail
in a number of different mosses, and descriptions accompanied
by careful drawings should be written. The peristome, especially,
is very characteristic and furnishes important features for the sys-
tematic study of the group.
Protoiiema.
If ripe spores are sown on moist soil, or on a compact
clump of moss, and kept under a bell-jar at the temperature
of an ordinary living room, the early stages of develop-
ment of the protonema are easily observed. The spore
swells and pushes out a papilla which elongates into a
tubular cell. This increases in length, becomes septate, and
branches are formed.
The later stages of development may be followed out
with the same material ; but there are some advantages in
obtaining vigorous specimens by the simple expedient of
turning a clump of moss bottom side up, and keeping it in
110 STUDY OF COMMON PLANTS.
a moist atmosphere for a week or two. By this means the
relation of rhizoids and protonema is made clear. It is
seen that they are the same thing, the filamentous growth
taking the appearance and structure of protonema or
rhizoids according to the conditions under which it grows.
It is also seen that the protonema may originate from
other parts of the plant, as well as from the spore.
On the protonema, whether it has its origin in the spore,
or from some other part of the plant, buds arise, from which
new plants are formed.
Archegoiiia and Antlieridia.
Among the specimens, if these have been gathered at dif-
ferent times of year, some will be likely to show "flowering
heads," most frequently terminating the stem, and sur-
rounded by a more or less conspicuous rosette of leaves,
the perichaetium. The antheridia and archegonia may
occur together in the same " flower," or in separate flow-
ers, on the same or on different individuals.
The whole structure is best studied by means of longi-
tudinal sections, which are easily made with a razor, after
a little practice, without any previous preparation of the
specimen. Examining such sections under the microscope,
if we chance to have selected a male specimen we shall
find antheridia in great numbers growing at the apex of
the axis, and with them slender, filamentous bodies, para-
physes, while outside of both is the circle of perichsetial
leaves. The antheridia are sacs, usually oblong in shape,
with a wall consisting of a single layer of cells, the interior
being composed of the mother cells of the antherozoids.
The latter are ciliated, protoplasmic bodies, closely resem-
bling those of the ferns. In the examination of a female
specimen the paraphyses are seen as before, but archegonia
MOSSES AND LIVERWORTS. Ill
take the place of antheridia. A fully formed archegonium
is a flask-shaped body with an elongated neck, and an
enlarged ventral portion, within which is the oosphere.
Fertilization takes place by the mingling of the substance
of an antherozoid with that of the oosphere, after the
antherozoid has forced it way down through the long canal
of the neck. The fertilized oosphere, now called the
oospore, becomes septate, and by still further cell-division
and growth the capsule with its seta, spores, and various
parts already described, is formed.
With suitable material and sufficient time the student
can readily verify most of the facts here given.
Cycle of Development.
It will be observed that in the mosses alternation of
generations takes place. The sporophyte, or non-sexual
generation, begins with the formation of the oospore and
closes with the spore, while the oophyte, or sexual genera-
tion, begins with the germination of the spore, and includes
both protonema and leafy plant.
NOTE. — It is important that this should be perfectly clear. The
student must see for himself the various stages of development of the
mosses as far as this is practicable. He may now consult the various
text-books and manuals, particularly those of Goebel, Arthur, Barnes,
and Coulter, Bower and Vines, and the references given by them. See
further on this subject under Ferns.
t
The peat mosses, Sphagnacese, are easily obtained in
many parts of the country, and afford an opportunity for
extended and profitable comparative study. Their habits,
structure of the vegetative organs, and fructification, all
present interesting points of difference from the true
mosses.
112 STUDY OF COMMON PLANTS.
LIVERWORTS. Hepaticce.
The liverworts are closely allied to the mosses, their
cycle of development being essentially identical with that
of the latter group. Accordingly our work will be re-
stricted to a comparison of the general characters of some
of the most easily procurable liverworts. Representatives
of the genera named at the beginning of this section are
widely distributed and easily obtained through a con-
siderable part of the year. Lunularia is of almost uni-
versal occurrence in greenhouses, and while seldom if ever
found in fruit, almost always has gemmse in different
stages of development. Conocephalus is common and
abundant in moist, shady places. The floating species of
Riccia have a wide range, as do also some of the species
of Porella. These and other genera will furnish a full
supply of material for comparative study.
The student is advised to proceed with his preliminary
observations as he did with the mosses, comparing a num-
ber of different kinds, instead of confining his attention
to a single species. Differences of habit between these
and the mosses, the bilateral and dorsi-ventral frond of
the liverworts, their texture and anatomical structure, and
peculiarities of fructification should all be noted. If the
mosses have already been studied as directed, there will
be little difficulty, with suitable material and the help of
the various manuals, in obtaining a corresponding general
view of the-structure and habits of the liverworts.
Many interesting subjects for more extended investi-
gation present themselves ; among them the following
are suggested as
MOSSES AND LIVERWORTS. 113
*
SPECIAL STUDIES.
I. Development of the gemmae. Lunularia offers ex-
cellent and abundant material for this, and its
gemmse, on account of their simplicity, are among
the best objects with which to begin studies of
developmental history.
II. Comparison of the anatomy of Conocephalus with
that of Marchantia. The latter is selected because
of its being so fully described in the books. For
the former, Lunularia or some other genus may
be substituted if more convenient.
III. Rhizoids of liverworts compared with those of mosses.
IV. Structure of the mature sporocarp in the different
families of liverworts.
V. Comparison of the archegonia and antheridia of
liverworts and mosses.
VI. Alternation of generations as seen in mosses and
liverworts compared with the ferns and other
vascular cryptogams. This will naturally be post-
poned until after the study of the latter groups.-
It will be found that in the ferns the oophytic
generation is reduced to a green prothallium, and
in the club-mosses and their allies a still further
reduction takes place.
VII. Origin of the calyptra of mosses.
114 STUDY OF COMMON PLANTS.
X. FERNS. FILICINE^E.
MATERIAL REQUIRED.
Shield-fern, Aspidium cristatum, Swartz, gathered in summer when the
fructification is fully developed.
Similar specimens of maidenhair, Adiantum pedatum, L., brake, Pteris
aquilina, L., spleen wort, Asplenium Filix-fcemina, Bernh.
Representatives of other genera of ferns that are procurable, such as
Cystopteris, Woodwardia, Osmunda, Dicksonia, etc.
SHIELD-FERN. Aspidium cristatum, Swartz.
General Characters.
I. Record first what you have observed as to the habits
and habitat of the plant. Does it grow in moist or dry
ground? in shady places or in the open? How do its
habits compare with those of other ferns, as regards choice
of soil and surroundings ? l
II. Notice the parts of the plant.
1. The underground stem, from which arise
2. Large, compound leaves, fronds, and
3. Roots. Observe their origin, form, and structure.
The leaf is the most characteristic part of the fern, and is
to be studied in detail. Notice
1 Cf. Underwood, Our Native Ferns and their Allies.
FERNS. 115
I. The leaf-stalk, stipe, with many thin, brown scales.
Are these persistent or deciduous ?
II. The outline of the frond and the form of its main
divisions, pinnae.
Ill* How the pinnae are divided. Compare the descrip-
tion of this species in Gray's Manual, p. 688.
IV. The venation. Select one of the pinnae in which
this is well denned, and draw it carefully in outline, tak-
ing pains to represent accurately the exact position of the
veins, tracing them to the end of their ultimate divisions.
Fructification.
I. The conspicuous bodies on the under side of the
pinnae are the sori, or fruit-dots. Observe
1. Their position. Are they situated on the back or
alongside of the veinlet?
2. The thin, scale-like covering, indusium, protecting
the spores.
II. Taking specimens nearly or quite mature, remove
the indusium, and with a good lens look at the spore-cases,
sporangia. Mount in water in the usual way, and examine
under a low power of the compound microscope. Observe
1. The general form and structure of the sporangium, —
a flattened sac, the walls of which are composed of
distinct cells.
2. The annulus, a row of thick-walled cells, forming a
continuation of the stalk. Does the annulus ex-
tend completely around the sporangium ?
III. Examine the sporangia under a high power, observ-
ing them in different positions. Compare different speci-
mens and draw a perfect one.
116 STUDY OF COMMON PLANTS.
IV. Using material that has been kept in alcohol, mount
some of the sporangia in water as before, and examine
microscopically. Run a drop of glycerine under the cover
glass and notice the result. Repeat the experiment until
you are satisfied as to the way the spores are discharged
from the sporangium.
NOTE. — This is by no means an easy problem. Notice where the
sporangium ruptures, the form of the cells composing the annulus, and
the changes they undergo with its change of position. Try the use of
different media, such as strong salt solution, etc. Compare the sporangia
of different ferns, and see whether all have the same structure and behave
alike.
V. Under the highest power, study the form and struct-
ure of the spores. Draw one or more of them.
VI. Taking almost any sorus except the oldest ones,
study the development of the sporangium by carefully
comparing the structure at different ages. A series of
drawings should be made illustrating as many stages as
possible.1
Prothallium.
If fern spores are sown on soil, or on pieces of decayed
wood, and are kept in a moist atmosphere, they will germi-
nate, and give rise to a structure known as the prothallium.
I. The early stages of development of the prothallium
are easily observed by examining the spores at intervals
during the first few days after they have been sown.
Microscopic examination shows that the spore swells, the
outer coat, exospore, ruptures, and the inner coat, endospore,
protrudes in the form of a papilla, which rapidly elongates
into a delicate, tube-like structure, the first root-hair. The
1 Cf. Goebel, Outlines of Classification and Special Morphology, p. 217
et seq.
FEKNS. 117
spore itself elongates at the same time and becomes sep-
tate, the septa at first arising at right angles to its
direction of growth. By further growth, and a series of
divisions in different directions, the mature prothallium
is finally produced. While the prothallium is in the
early, or filamentous stage of its development, the form
and contents of its cells and other structural details are
easily observed. Full descriptions, accompanied by care-
ful drawings, should be made.1
II. The mature prothallium may be raised successfully
by taking care of the specimens that have been started
as directed above; but since they require weeks, or even
months, to attain their full development, it is more con-
venient to obtain prothallia from conservatories where
ferns are cultivated. In the pots containing ferns, or on
the surface of the moist earth near by, one can frequently
find excellent specimens. They are generally heart-shaped,
a few millimeters to a centimeter in diameter, of a delicate
green color, and so much like small liverworts as some-
times to deceive experienced collectors.
An uninjured specimen that has been carefully washed, so
as to remove the adherent particles of earth, shows under
the microscope a deep anterior depression, sinus, and back
of this a thickened portion of the prothallium, sometimes
called the cushion. The latter is several layers of cells in
thickness, while the parts nearer the margin are but one
layer thick. Rhizoids in great numbers arise from the
lower surface. The growing point is at the base of the
depression. The arrangement of the cells at this point
indicates their order of development, which is readily
1 For a model cf. Campbell, Development of the Ostrich Fern.
Memoirs, Boston Soc. Nat. Hist., Vol. IV, No. II (1887).
118 STUDY OF COMMON PLANTS.
made out if younger specimens of different ages are com-
pared.
After the points named have been observed, drawings of
the mature prothallium should be made and compared with
those of earlier stages. If the material is suitable for the
purpose, intermediate stages of development also may be
studied.
III. On the lower side of the mature prothallium arche-
gonia and antheridia are produced. These are organs of
reproduction, corresponding in function to the "essential
organs " of flowering plants. The archegonia are usually
situated near the sinus. They are flask-shaped bodies, the
lower portion of which is sunk in the tissue of the
prothallium, while the neck projects above the surface.
The neck consists of a wall made up of four longitudinal
rows of cells, surrounding a single row of canal-cells which
leacT down to the obsphere. The latter is the cell from
which, after fertilization, the embryo, i.e. the young frond,
arises.
The antheridia are, as a rule, more remote from the
sinus, and present the appearance of small, hemispherical
protuberances, consisting of a wall one layer of cells thick,
which encloses the mother-cells of the anther ozoids. The
latter are minute, ciliated, protoplasmic bodies, and are the
active agents of fertilization. They are best observed by
placing in water on a slide prothallia that have been kept
rather dry for some time. After the water has been
absorbed by the antheridium the latter ruptures, and the
antherozoids in great numbers are seen in active motion,
swarming in the field of the microscope like so many
animalcules. Under favorable circumstances they have
been seen to move towards an archegoniuni and 'enter
it, passing down through the canal-cells which have now
FERNS. 119
become mucilaginous. The union of an antherozoid with
the oosphere is necessary in order to the subsequent
development of the latter.1
Developmental History and Minute Anatomy.2
The oosphere after fertilization becomes surrounded by a
cell-membrane, and is now known as the oospore. It is
afterwards divided into two cells by a septum nearly
parallel with the axis of the archegonium. This is fol-
lowed by the formation of two additional septa at right
angles with the first and with each other, the oospore- being
thus divided into eight parts or octants. Further cell-
division takes place, and the embryo soon shows a differ-
entiation into a foot, or absorptive organ, by which it draws
nutriment from the prothallium, a first root, leaf, and stem.
The first leaf, root, and foot are temporary structures, all
of them, serving the needs of the plant for a comparatively
short period. The stem, on the other hand, is of slow
growth, but is permanent, and finally attains the size and
structure that it exhibits in the mature plant; roots and
leaves arise from it, the prothallium finally disappears, and
the so-called sporophyte takes the place of the preceding or
oophyte generation.
1 Only a bare outline is given above. For further details the student
should consult $trasburger, Practical Botany, pp. 290-296 ; Bennett and
Murray, Cryptogamic Botany, p. 64 et seq. ; Goebel, Outlines of Classifi-
cation and Special Morphology, p. 198 et seq., and references given by the
authors just named. For some of the most recent and valuable contri-
butions see Campbell, Development of the Ostrich Fern, and various
papers by the same author in the Botanical Gazette, Annals of Botany,
and other periodicals.
2 A practical study of the developmental history of ferns requires more
time than can possibly be given to it in a preparatory course, and accord-
ingly it is thought best to omit altogether directions for laboratory work,
merely giving a resume of the cycle of development as it has been worked
out by different botanists. Cf. Goebel, I.e., p. 204 et seq.
120 STUDY OF COMMON PLANTS.
The alternation of generations just referred to appears
very clearly in the ferns. The oophyte, or sexual gener-
ation, includes the stage beginning with the germination
of the spore and closing with the fertilization of the
oosphere. The sporophyte, or non-sexual generation, be-
gins with the formation of the oospore and closes with the
mature spore. The prothallium is, therefore, the charac-
teristic feature of the oophytic generation, and the leafy
plant, in this case the "fern," of the sporophytic generation.1
Full instruction for the study of the minute anatomy of
ferns is given in a number of accessible manuals, and need
not be repeated here. A quite full and satisfactory ac-
count of Pteris is given by Sedgwick and Wilson in their
General Biology ; Adiantum is well treated by Arthur,
Barnes, and Coulter in the Plant Dissection ; and Bower
and Vines give sufficient help for a thorough microscopic
study of Aspidium. It appears to the writer better, if the
time is limited, to undertake complete examination of
only one part, preferably the stem, since the leaf repeats
in its general structure much of what has already been
seen in the flowering plants. In studying the stem, most
of the time should be given to the nbro-vascular bundle,
including a comparison of its structure with that of the
bundle of Indian corn and the apple tree. The investiga-
tion may well be extended to various other plants ; but its
success will depend on the preparation and judgment of
the teacher, and the previous training of the student. On
the whole, a comprehensive study of the fibro-vascular
1 So much depends on a correct conception of the alternation of gen-
erations, that the teacher is advised to review, illustrate, and, in short, use
all means to make it clear. It stands as a prominent developmental
character, common to all the groups of plants from mosses to phanero-
gams. Cf. Sachs, History of Botany, pp. 200, 201.
FERNS. 121
bundle hardly falls within the scope of an elementary
course.
RELATIONSHIP.
A careful comparative study of a number of prominent
genera of ferns should be made. Those named above are
widely distributed, and, in general, easily procurable. For
this part of the work, dried specimens are nearly or quite
as satisfactory as fresh ones. The comparison, while in-
cluding a study of external characters, should be directed
primarily to the fructification, which presents the really
distinctive features of the different genera. It is necessary
in each of the genera studied, to observe particularly the
form of the sorus and indusium, and the way in which the
latter is attached to the leaf. If ten or a dozen different
kinds of ferns are studied in this way, with accompanying
drawings and descriptions, the student will have learned
from his own observation the salient characters of the
ferns as a group, the marks that distinguish the more
prominent genera, and the features by which the species
belonging to them are recognized.1
The ferns include three thousand or more species, vary-
ing widely among themselves in habits and external feat-
ures. With leaves of extraordinary variety and beauty ;
their texture delicate or coriaceous, or extremely thin and
translucent, as in the filmy ferns ; of various habits, creep-
ing, climbing, erect, or tree-like ; growing in every quarter
of the globe, and yet exhibiting marked preferences of soil
and surroundings ; a dominant group in earlier geological
time, and still holding a manifest supremacy among the
higher cryptogams, — they present themselves as one of the
most varied and attractive, and at the same time most easily
1 For further hints see Underwood, Our Native Ferns and their Allies.
122 STUDY OF COMMON PLANTS.
studied groups of plants. They are of special interest as
representatives of the higher flowerless plants, the vascular
cryptogams, since they share with them certain develop-
mental features that are wanting or are imperfectly seen
in phanerogams. The alternation of generations is far more
easily recognized here than in flowering plants, since both
generations are characterized by structures of considerable
size. The oophyte, or sexual generation, presents us with
the prothallium, which is a relatively conspicuous, leaf-like
body, bearing archegonia and antheridia, structures that do
not occur in the same form in phanerogams.1 The system-
atic literature is extended and rather expensive. Eaton's
Ferns of North America is the best for this country, and
the works of Hooker and Baker give the most help on
foreign species ; but with Gray's Manual or Underwood's
little book, the student will be able to identify without
difficulty the ferns indigenous to the region where he lives,
and this is suggested to him as an interesting and instruc-
tive piece of systematic work.
1 On the homologies of these organs as they exist in higher plants cf .
Bennett and Murray, Cryptogamic Botany, p. 11 et seq. ; Goebel, Out-
lines of Classification and Special Morphology ; Macraillan, Metaspermaz
of the Minnesota Valley, and recent periodical literature.
HORSETAILS. 123
XL HORSETAILS. EQUISETINE^E.
MATERIAL REQUIRED.
Common horsetail, Equisetum arvense, L. The fertile fronds must be
gathered in the spring when the spores are mature. These are
preferably examined fresh, but may be preserved in alcohol.
Sterile fronds in the early stages of development may be gathered
at the same time, but fully formed ones will have to be obtained
later in the season, unless they are pressed or put up in alcohol
the preceding year. Underground stems, with fronds attached,
should be collected.
Other species of the same genus, such as the scouring-rush, Equisetum
hie'male, L., and others.
COMMON HORSETAIL. Equisetum arvense, L.
General Characters.
I. Note first the habits of the plant, the places in which
it grows best, and the time of year when it appears above
ground.
II. Compare the two forms that arise from the same
rootstock, the fertile and sterile fronds, noting points of
likeness and difference.
III. Examine the underground stem, observing its
peculiarities of form, size, and structure as compared with
the aerial stems.
Fertile Frond.
I. Examine the fertile frond throughout, and describe
in detail its characteristic features. Notice
124 STUDY OF COMMON PLANTS.
1. The succession of nodes and inter nodes. Are there
any branches ?
2. The whorls of modified leaves arising at the nodes.
How many leaves are there at each node? Are
they separate or united? Do they differ in either
texture or color from the stem ? If so, how ?
3. Surface, form, and structure of the stem. Cut a
transverse section of an internode and examine
under a dissecting microscope. Is it solid or
hollow? Notice the openings, lacunae, and their
number and position. Are these constant in differ-
ent specimens? Is there any mechanical advantage
in such a disposition of material ?
Make an outline sketch of the section, using, if
necessary, a higher magnifying power.
II. Study next the spike terminating the stem and
bearing the fructification. It will be seen that it is a
modified portion of the stem, showing a succession of nodes
and internodes, and exhibiting more or less perfectly the
same structural features as other parts of the stem.
1. With a pair of fine forceps remove one or more of
the leaves, here called scales, and examine them
carefully. Their study will be facilitated by
making transverse and longitudinal sections of the
spike, so as to expose the scales more fully. Are
they stalked or sessile ? Draw one in outline.
2. Examine under a lens the spore-cases, sporangia,
borne on the under surface of each scale. How
many are there ? What is their shape ? Make an
outline sketch.
III. Remove carefully one of the sporangia, mount in
water, and examine with the compound microscope. Be
HORSETAILS. 125
sure to have a well-formed and uninjured specimen.
Observe the peculiar structure of the cells that compose
the sporangium wall. Ascertain, if you can, how the
sporangium opens.1 Draw carefully a few of the cells,
using the high power.
IV. Examine the spores under the high power of the
compound microscope, mounting some of them in water
and others dry. How do the dry ones differ from those in
water? Breathe gently on them, and see if any changes
take place. Draw one or more of the spores with their
slender, hygroscopic appendages, elaters.
V. Sow some of the spores in water and others on moist
soil, and at intervals examine with the microscope. Germi-
nation of the spores and the early stages of development
of the prothallium are easily observed, and should be figured
and described.
Sterile Frond.
I. Examine specimens of the sterile frond throughout,
comparing them in detail with the fertile ones. How do
they differ from the latter in size, color, texture, formation
of branches, and structure on transverse section? Is
there a "division of labor"? If so, point out what you
conceive to be the most important function of the fertile
frond; of the sterile frond.
II. Study the fibro- vascular bundles, and compare with
those of the fertile frond. Verify the details of structure
as given by Goebel, Outlines of Classification and Special
Morphology, pp. 270-272.
JCf. Newcombe, Spore-dissemination of Equisetum, Bot. Gaz., Vol.
XIII (1888), p. 173.
126 STUDY OF COMMON PLANTS.
RELATIONSHIP.
With the species already studied compare others of the
same genus, such as Eqwisetum hiemale, L., E. limosum, L.,
etc. Do these species show the same general structure ?
Do they present the same differentiation into fertile and
sterile fronds ?
Comparison with still other species of the single genus now
composing this family1 shows that the Equisetinese. possess
very marked and characteristic features by which they are
distinguished from all other families of plants. At the
same time their close relationship with the ferns is evident
when their developmental history is followed out. If the
spores of the common horsetail are sown as directed above,
the development of the prothallium, including the forma-
tion of archegonia and antheridia, can be observed in detail
in the course of a few weeks, and affords a most instructive
study.2 If this study is carried far enough to include the
formation of the embryo and growth of the young plant, it
is seen that the cycle of development is essentially identical
with that of the ferns.
1 The horsetails are remnants of a family which once flourished luxuri-
antly, reaching its highest development in the Carboniferous period, when
there were several genera, including a number of tree-like species.
2Cf. Campbell, Male Prothallium of the Common Horsetail, Arner.
Nat., 1883, p. 10.
CLUB-MOSSES AND THEIR ALLIES. 127
XII. CLUB-MOSSES AND THEIR ALLIES.
L.YCOPODINEJE.
MATERIAL REQUIRED.
Fresh specimens of Selaginella from the conservatory. A number of
species are common in cultivation, and any of them may be used.
Club-moss, Lycopodium clavatum, L., with spore-bearing spikes. Simi-
lar specimens of other species of the same genus, e.g. L. lucidu-
lum, Michx., L. complanatum, L., etc.
Any other vascular cryptogams that are procurable, as Marsilia or
Isoetes.
SELAGINELLA. S. stolonifera, denticulata, etc.
General Characters.
I. Record your observations of the plant as a whole.
Where did it grow, and under what conditions ? Point out
any peculiarities of form, texture, or habit, by which it
would readily be distinguished from ferns.
II. Examine carefully the mode of branching. Draw a
diagram to represent it. Is it dichotomous or monopodial'n
The plant is said to be bilateral and dorsi-ventral ; show
how this is true. How do you distinguish between the
dorsal and ventral aspect of the plant ? 2
III. Describe the form and arrangement of the leaves.
Are they all alike ? How many rows are there ?
IV. On well-developed specimens, slender, root-like
organs, rhizophores, are to be found. Notice where these
1 Cf. Bower and Vines, Practical Botany, I, p. 162.
2 Cf. Strasburger, Practical Botany, p. 296.
128 STUDY OF COMMON PLANTS.
arise, whether from the lower (ventral), or upper (dorsal)
side of the stem. Where their ends com'e in contact with
the soil, roots are produced. Observe their peculiar mode
of branching, unusual for roots.
Fructification.
The fertile branches are not particularly conspicuous and
may be overlooked ; they are readily recognized, however,
by their rigid, erect habit and quadrangular outline, in
contrast with the flattened and spreading sterile branches.
I. Notice the form and arrangement of the leaves.
How do they differ from those of other parts of the plant ?
II. The spore-cases, sporangia, arise singly in the axils
of the leaves. They are of two kinds, microsporangia in
the axils of the upper leaves, and macrosporangia, few in
number, in the axils of the lower leaves of the fertile
branch. Examine different specimens, under a good lens,
until you are satisfied as to the position of the two kinds
of sporangia and their external differences.
III. With a pair of fine forceps remove the upper part
of a fertile branch with its microsporangia. Dissect care-
fully on a slide, and examine with the low power of the
compound microscope. Compare the sporangia as they lie
in various positions and notice
1. The exact relation of the sporangium to the stem
and leaf, and whether it is stalked or sessile.
2. Its form and mode of dehiscence.
NOTE. — The cause of the opening of the sporangium may not
be obvious, but there is no difficulty in finding the line of dehis-
cence and observing the escape of the spores.
3. The structure of the sporangium wall.
4. The spores, set free in great numbers when the spo-
CLUB-MOSSES AND THEIR ALLIES. 129
rangium opens. From their small size, as com-
pared with those produced in the macrosporangia,
these are called microspores. With the high power,
observe
a. The form of the microspores. Are they strictly
spherical?
b. Their structure, particularly the spiny exospore
and granular contents.
IV. Remove a macrosporangium from the lower part of
a fertile branch and examine on the slide, using first a
good lens, and afterwards the compound microscope. Ob-
serve
1. The obvious external differences by which this is
distinguished from the microsporangium.
2. The number of spores contained in the sporangium.
From their relatively large size, these are called
macrospores.
3. The structure of the macrospores. This is readily
made out by simply treating with potash solution,
and dissecting away the hard external coat, as
recommended by Bower and Vines.1 Afyer removal
of the exospore, the smooth, light-colored endo-
spore is found, and the contents of the spore, chiefly
oil and aleurone grains, with the mass of cells
composing the prothallium, are plainly seen. Sec-
tioning must be resorted to, if these are shown
accurately in position; but all of them can be
recognized easily and satisfactorily by following
the treatment suggested.
NOTE. — It is important that these parts should be clearly seen
and understood. In Selaginella the prothallium is formed before
1 Practical Botany, I, p. 173.
130 STUDY OF COMMON PLANTS.
the spore has left the mother plant, and it is still for some time
enclosed in the macrospore, which also contains a large amount of
food materials. The whole structure shows a likeness on the one
hand to the spores of other vascular cryptogams, and on the other
to the embryo-sac of flowering plants.
Developmental History and Minute Anatomy.
As in the case of the fern, a laboratory study of the
developmental history requires a special investigation ex-
tending through some weeks or months. The following
important features of the cycle of development may be
mentioned: Selaginella, as well as the ferns and horse-
tails, is characterized by alternation of the. oophyte, or
sexual generation, with the sporophyte, or non-sexual gen-
eration. The latter differs widely from that of the ferns, in
that instead of one kind of spore, giving rise to prothallia
which bear both antheridia and archegonia, there are two
kinds, macrospores, or female (archegonia-bearing) spores,
and microspores, or male (antheridia-bearing) spores, are
produced, — a distinct foreshadowing of what is seen
in flowering plants, — the microspores corresponding to
pollen-grains, and the macrospores to the embryo-sac of
the ovule. The oophyte, again, as compared with that
of the ferns, is reduced in size, and all its early stages of
development are completed within the spore, reminding us
of similar facts in the developmental history of phanero-
gams. The prothallium of the microspore, in particular,
is reduced to the low.est terms, and should be compared
\vith the two or more vegetative cells (rudimentary pro-
thallium) in the pollen-grain of certain gymnosperms.
The archegonia, produced only on the prothallium of the
macrospore, are essentially like those of ferns, though
somewhat simpler, but after fertilization the first septum
of the oospore is formed at right angles to the axis
CLUB-MOSSES AND THEIR ALLIES. 131
of the archegonium, and the upper of the two cells thus
formed develops into a suspensor, a structure characteris-
tic of flowering plants, but occurring in few- cryptogams.
RELATIONSHIP.
It is desirable that at least the external characters and
fructification of one or more additional genera of vascular
cryptogams should be studied in connection with the pre-
ceding ones ; but specific directions are omitted, partly
because of uncertainty as to material likely to be procura-
ble, and partly because it is understood that by this time
the student should be in a position to make an intelligent
comparative study of at least the general characters of
any group to which he has already given special attention.
Club-mosses are as likely to be available as any of the
Lycopodinese, since they are pretty widely distributed,
and besides are extensively used for Christmas decorations.
As they appear in market in the middle of winter they are
frequently in fruit. Marsilia and Isoetes are of great
interest, and when they can be obtained may well claim
a considerable share of the time given to this group.
Aside from the manuals and text-books, the references
given below will be found serviceable to those who under-
take a further study of the vascular cryptogams.1
1 Campbell, Development of Pilularia globulifem, L., Annals of
Botany, Vol. II, p. 233 ; Contributions to the Life-History of Isoetes,
Annals of Botany, Vol. V, p. 231 ; On the Prothallium and Embryo of
Osmunda Claytoniana, L., and 0. cinnamomea, L., Annals of Botany,
Vol. VI, p. 49 ; On the Affinities of the Filicinece, Botanical Gazette,
Vol. XV (1890), p. 1 ; On the Relationships of the Archegoniata, Botani-
cal Gazette, Vol. XVI (1891), p. 323. Frequent references to other
important literature are given by the author in the papers cited.
132 STUDY OF COMMON PLANTS.
XIII. THE PINE FAMILY. CONIFERS.
MATERIAL REQUIRED.
Twigs of the following species: White pine, Pinus Strobus, L. ; Aus-
trian pine, Pinus A ustriaca, Hoess ; Norway spruce, Plcea exceka,
Lk. ; Hemlock, Tsuga Canadensis, Carr. ; Juniper, Juniperus corn-
munis, L. ; Red cedar, Juniperus Virginiana, L. ; Arbor Vitae,
Thuja occidentalis, L.
Mature fruits of the preceding, and flowers, both staminate and pis-
tillate, as far as these can be procured.
Substitutions, such as Scotch in place of Austrian pine, may be made
as occasion requires.
"WHITE AND AUSTRIAN PINE.
I. Compare branches of the two species as to surface
markings and other external characters.
II. Compare the foliage leaves.
1. How many are produced in a fascicle? Examine
specimens enough of both species to determine the
general rule, since exceptions frequently occur.
2. How do those of the two species differ in length,
thickness, rigidity, and color ?
3. With a sharp knife make a transverse section of a
leaf of each kind. Examine with a lens and note
difference of outline.
III. Examine next the different sorts of scale-like leaves.
Notice
1. Differences of size and texture.
THE PINE FAMILY. 133
2. Whether they are deciduous or persistent. Do the
two species agree in this respect?
IV. Study cones of the two species, and note the points
in which they agree or differ.
V. Extend the comparison, if practicable, to the stand-
ing trees, observing their mode of branching and other
characteristic features.
VI. Finally, passing in review all the points to which
attention has been called, summarize your observations in
a brief written description, taking care to bring out clearly
the distinctive characteristics of each species.
NORWAY SPRUCE. HEMLOCK.
Determine in what respects the Norway spruce differs
from the pines. Is the arrangement of the branches the same?
How do the leaves compare in size, form, and mode of inser-
tion with those of the pines? Compare the terminal buds.
Is there anything common to the cones of the two species
of pines riot belonging to those of the Norway spruce?
Do the seeds of the latter differ in any structural par-
ticular from those of the former ?
In the same way compare the hemlock with the different
species already studied, noting arrangement of branches,
position, form, and size of leaves, peculiarities of terminal
buds, structure of cones, and other characteristic features.
JUNIPER AND RED CEDAR.
I. Compare the two species and note all points of dif-
ference and resemblance.
1. What is the form of the leaves of the juniper?
Number of leaves in a whorl? How do those of
the red cedar compare in size, shape, and arrange-
134 STUDY OF COMMON PLANTS.
ment with those of the juniper? Are the leaves
of the red cedar all alike? Do they all exhibit
the same arrangement?
2. If the fruits are to be had, study their structure and
points of resemblance and difference.
3. If living specimens are accessible, compare the habits
of the two species. Which assumes the size and
habits of a tree ? Is this difference constant ?
II. Next compare these with the conifers previously
studied. What characters are common to the juniper
and red cedar that do not belong to the pine, spruce,
and hemlock ?
ARBOR VITJE.
I. Observe the form of the leaves and their arrange-
ment on the branches. Are the leaves all alike ? Do
they exhibit any structural peculiarity not observed in
those of the other conifers ?
II. Compare the cones with those of other genera. Is
the arrangement of the scales the same? How does it
compare with the leaf arrangement?
When the pollen of the different species begins to be
shed in May, compare the structure of the flowers, both
staminate and pistillate, of as many different conifers as
can be obtained.
I. How do the staminate flowers of the hemlock differ
from those of the Norway spruce? From those of the
pines? What peculiarities are presented by those of the
red cedar ?
II. Make a similar comparison of the pistillate flpwers?
III. Of all the species studied which are monoecious?
Are any of them dioecious ?
THE PINE FAMILY. 135
Write a brief summary of the particulars in which all the
species thus far examined agree. These, with certain
features that you have not yet observed, constitute the
family characters of the Coniferce.
RELATIONSHIP.
From the preceding study it will be easy to understand
something of the relationship of plants and the way this is
determined by botanists.
1. Plants that are related to each other show a mutual
resemblance. This may be observed in
a. External features and habits, including form, direc-
tion of growth, etc.
b. Structure.
c. Reproduction.
</. Developmental history.
e. To some extent, physiological peculiarities. But
in this respect closely related plants often show
great differences.
In our study of the conifers we have directed -our atten-
tion chiefly to external features.
2. Plants exhibit degrees of relationship, those most
closely related being most alike, while those re-
motely related are less alike.
3. Plants that are related as parents and offspring,
forming a succession of individuals not to be
distinguished from each other by any constant
differences, constitute a species. The white pine
is one species, the Austrian pine another, and
so on.
4. Closely related species constitute a genus. Thus the
various species of pines together make up the
136 STUDY OF COMMON PLANTS.
genus Pinus, and ,the different species of juniper,
the genus Juniperus. We have thus far studied
one or more representatives of each of the genera
Pinus, Juniperus, Picea, Tsuga, Thuja.
5. Closely related genera constitute a family. The
genera just named, with a number of others, make
up the Coniferse, or Pine family.
6. Closely related families constitute higher groups,
sometimes designated as orders, though the usage
is not uniform. Finally, orders (of flowering
plants) are grouped together in the great classes
gymnosperms, monocotyledons, and dicotyledons.
The relationships here pointed out are those of descent.
It is believed that just as all individuals of a species are
descendants of a common ancestor, so all the species of a
genus and all the genera of a family have a common,
though remote origin.
We shall have constant opportunity in our further study
of plants to become acquainted with specific, generic, and
family characters. Their recognition is frequently at-
tended with some difficulty, and in all cases the exercise
of careful judgment is required. In fact botanical work
consists very largely in accumulating evidence by which
degrees of relationship are determined.
THE GRASS FAMILY. 137
XIV. THE GRASS FAMILY.
MATERIAL REQUIRED.
Entire plants of cultivated wheat, soon after it has headed out.
Similar specimens bf the following grasses : Chess, Bromus secalinus, L. ;
Quick-grass, Ayropyrum repens, Beauv. ; Orchard-grass, Dactylis
ylomerata, L. ; Fowl meadow-grass, Glyceria nervata, Trin.; Barn-
yard-grass, Panicum Crus-galli, L. ; Indian rice, Zizania aquatica,
L. ; Bur-grass, Cenchrus tribuloides, L. ; Beard-grass, Andropogon
furcatus, Muhl. ; Timothy, Plileum pratense, L. ; June grass, Poa
pratensis, L.
Some of these can be obtained in a suitable condition for study early
in June in the northern States, and at a still earlier date farther
south ; others are best examined in late summer or autumn. Rye
may be used instead of wheat, and other substitutions may be
made if necessary.
WHEAT. Triticum vulgare, Villars.
General Characters.
I. Taking a number of entire and uninjured specimens,
determine first the relation of the stem and root system.
Is there anything to show whether more than one culm is
produced from a grain of wheat ? " By the process of til-
lering, or multiplication of stems from one root . . . over
fifteen hundred grains have been obtained from a single
seed." The beginnings of this process may be observed in
seedlings of wheat started in the laboratory.
II. Examine the stem, culm, and note all peculiarities of
1 The Graminese will be studied to better advantage after some other
families of monocotyledons, such, for example, as the Liliaceae,
138 STUDY OF COMMON PLANTS.
form and structure. Is any mechanical principle involved
in the disposition of material ? Observe the number and
position of the nodes (parts of the stem to which the leaves
are attached). Do they contribute in any way to the
strength of the structure ?
Bend the culm through several degrees, after stripping
off the leaves. Where are the weakest parts ? Is there
any special protection or support for these parts ?
Taken as a whole, is the stem satisfactorily constructed to
sustain the weight of the head and resist the stress of winds?
NOTE. — Microscopic examination shows a simple but effective arrange-
ment of the mechanical elements of the culm, by which great strength is
secured with a minimum of material.1
III. Take up next the relation of leaves and stem.
How are the leaves attached ? Are their sheaths entire or
slit? What is the leaf arrangement?
IV. Note the form and structure of the leaves, arid the
manner in which they twist in drying.2
Notice the appendage of the leaf at the angle made by
the blade and culm. What is it morphologically, and
what is it called ? 3
Inflorescence and Flowers.
I. Notice first the general features of the inflorescence.
It has the form of a thickened spike, composed of many
spikelets. The latter are arranged alternately on each side of
a " zigzag, jointed, channelled rachis." Remove half a dozen
or more of the lower spikelets to make this more obvious.
II. Study next the structure of one of the spikelets.
Each spikelet includes several flowers and is subtended by
1 Cf. Haberlandt, Physiologische Pflanzenanatomie, p. 114 et seq.
2 Cf. Beal, Grasses of North America, p. 29 et seq.
3 Cf. Gray, Structural Botany, p. 106.
THE GRASS FAMILY. 139
two glumes. Observe the form and texture of the glumes.
Are they symmetrical or one-sided ? Is their surface
smooth or hairy? Are there any longitudinal ribs or
" nerves "' ?
III. Ascertain how many flowers there are in a spikelet.
•Each of the fully developed flowers is subtended by a
floral glume and a palet. The former, in the bearded vari-
eties of wheat, bears at its apex a long, barbed awn.
IV. Compare carefully the floral glume and palet, not-
ing their differences of form, position, and structure.
V. Separate the floral glume and palet so as to expose
the parts of the flower within. Examine flowers of differ-
ent ages until the essential organs are found in good
condition. How many stamens are there? How many
stigmas? Look for some minute, scale-like bodies, lodi-
cules. How many are there, and where are they placed ?
VI. Construct a diagram of the flower, showing the
position of the floral glume, palet, lodicules, stamens, and
pistil.1
VII. Open different flowers of the same head, and con-
tinue the examination until the relations of anther and
stigma are ascertained. Does it appear that the flowers of
wheat are cross- or self-fertilized.2
RELATIONSHIP.
Obtain good specimens of any of the genera named
above, and compare them with wheat throughout, noting
all points of difference and agreement. Chess is excellent
1 Cf. Eichler, Bluthendiagramme, p. 119 et seq. Some interesting sug-
gestions are given by Allen, Flowers and their Pedigrees, p. 160 et seq.
2 Cf. Seal, I.e., p. 37 et seq.
140 STUDY OF COMMON PLANTS.
to begin with, on account of the simplicity and distinct-
ness of its floral structures. Many of the other genera
are likely to prove rather troublesome until the student
has had some experience.
After careful comparison of as many different kinds of
grasses as practicable, summarize your observations in a
general account of the characters of the Graminese.
This family includes some four thousand species and is
of great economical importance, since it furnishes, directly
or indirectly, by far the larger part of the food of the human
race. Botanically it presents many points of interest.
While there are many species of grasses within the tropics,
they form a characteristic "sod" only in the cooler % parts
of the world. Some depart so widely from the habits of
those we have studied as to be properly reckoned among
climbing plants. Although giving evidence of very con-
siderable modification, the flowers are, with few exceptions,
destitute of odor and attractive colors, and are either self-
fertilized or depend for fertilization on the agency of the
wind. The seeds are disseminated in a variety of ways,
some passing undigested through the alimentary canal of
herbivorous animals, others, as Cenchrus, bearing hooked
or spiny appendages, and still others, as Stipa, provided
with a twisting awn that attaches itself to the coats of
animals or buries the grain in the earth. In Tripsacum
the joints of the spike break apart and are often floated
away by water, while species of Panicum and Eragrostis
are blown about by the wind as " tumble-weeds." The
cultivation of the most important grains is prehistoric and
their origin uncertain.1
1 Cf. De Candolle, Origin of Cultivated Plants, p. 354 et. seq. ; Hackel,
The True Grasses ; Beal, Grasses of North America.
THE SEDGE FAMILY. 141
XV. THE SEDGE FAMILY. CYPERACE^E.
The study of this family involves no little difficulty, and its various
genera present such wide differences that it is impossible to select
one that may be taken strictly as a " type." Nevertheless, it is
desirable that at least the conspicuous and widely distributed
genus Carex should be familiarly known.
As a convenient representative, we select one of the most common
species.
CAREX. C. hystricina, Muhl.
General Characters.
Note the locality and choice of surroundings, the habit
of growth, whether in clumps or scattered, the height to
which the plant grows, and general resemblance, if any, to
other plants already studied.
Stem and Leaves.
I. Notice the form and structure of the culm. How
does it differ from that of wTheat and other grasses ?
II. Note the relation of stem and leaves. In how many
ranks are the latter disposed ? How do their sheaths differ
from those of the grasses ? Is there a ligule ?
III. Describe the leaves as to form and surface. Observe
their behavior in drying.
Inflorescence and Flowers.
I. How many inflorescences are there? Are they sessile
or stalked?
142 STUDY OF COMMON PLANTS.
II. Beginning with the lowest inflorescence, study care-
fully the individual flowers. Note first that each flower
is borne in the axil of a bract or scale. Describe the latter
as to form, color, and structure.
III. Each flower is further protected by a sac called the
perigynium. Examine this, observing critically its form
and surface, venation, and the long beak terminating above
in two sharp teeth.
IV. Open the perigynium and examine the pistillate
flower. It consists of a single pistil, which in some species
of Carex has two stigmas with a lenticular ovary, caryopsis,
while in others the caryopsis is triangular, and the stigmas
are three in number. Which do you find to be the case in
this species ?
V. Taking younger specimens, examine the uppermost
(staminate) spikes. How do they differ in external
features from the pistillate ones ? Is each flower sub-
tended by a scale ? Does it have a perigynium ? How
many stamens are there ?
VI. From the observed facts, what do you infer as to
the mode of fertilization ?
RELATIONSHIP.
A number of other species should, if possible, be com-
pared with the one just studied. Carex lupulina, utricu-
lata, stricta, gracillima, laxiflora, Pennsylvania, rosea, etc.,
are of common occurrence and suitable for such a com-
parison. The beginner will do well to heed Professor
Bailey's remark to the effect that this is " an exceedingly
critical genus, the study of which should be attempted
only with complete and fully mature specimens." After
THE SEDGE FAMILY. 143
becoming familiar with several representatives of the
genus Carex, some time may be given to a few other
genera of Cyperacese, as, for example, Cyperus, Eleo-
charis, Scirpus, and Eriophoruin. An intelligent compari-
son of a limited number of well-developed and well-chosen
forms will place the student in a position to continue
his work satisfactorily ; but the study of sedges demands
clear judgment and unlimited patience, and will never
prove attractive to any one who is not possessed of
these qualities. For classification, Gray's Manual, sixth
edition, will serve a good purpose. Professor L. H.
Bailey's Types of the G-enus Carex, Memoirs of the Torrey
Botanical Club, Vol. I, No. I, is the most important con-
tribution that has yet been made to our knowledge of
North American species.
144 STUDY OF COMMON PLANTS,
XVI. THE ARUM FAMILY. ARACEJE.
MATERIAL REQUIRED.
Entire plants of Indian turnip, Ariscema triphyllum, Torr., in flower.
Similar specimens of skunk-cabbage, Symplocarpus fcetidus, Salisb.
Flowers of cultivated calla, Richardia Africana, Kunth.
Other plants of this order that are procurable, such as sweet-flag,
Acorus Calamus, L., and any of the cultivated aroids.
INDIAN TURNIP. Ariscema triphyllum, Torr.
General Characters.
Examine entire specimens in a fresh condition. Note
I. The thick, rounded, underground stem, conn, more or
less wrinkled externally.
II. Long fibrous roots growing out from its upper part.
III. Above ground, the smooth, cylindrical stem with
membranaceous, sheath-like leaves below, and one or two
large, compound, foliage leaves above. Describe the latter
in detail.
IV. The peculiar venation, differing from that of a
majority of monocotyledons. Sketch one of the leaflets in
outline, and point out the mechanical advantages.
V. Note the acrid taste due to the mechanical effect of
the raphides (crystals) on the tongue and throat.
Inflorescence and Flowers.
I. The inflorescence is covered by a peculiarly shaped,
arched spathe. Compare this in a number of specimens,
and note variations.
THE ARUM FAMILY. 145
II. Open a spathe so as to explore the parts within.
Observe
1. The elongated, club-shaped, sterile portion, of the
spadix.
2. The lower, fertile part, on which the naked flowers
are borne.
III. Examine the flowers of a number of different
individuals. It will be seen that, as a rule, some have
only pistillate flowers and others only staminate ones.
Notice
1. The very simple structure of the staminate flowers
and the mode of dehiscence of their anthers.
2. The closely packed pistillate flowers, each with a
sessile, white stigma. Make sections and ascertain
the structure of the ovary, and the number and
position of the ovules.
IV. Ascertain by a further comparison of specimens
whether this species is strictly dioecious.
V. If Ariscema Dracontium, Schott., can be obtained,
compare it throughout with the species just studied,
noting carefully all points of likeness and difference.
»
SKUNK-CABBAGE. Symplocarpus fcetidus, Salisb.
General Characters.
The skunk-cabbage is in flower very early in the season.
Its striking features at once attract attention. The dis-
agreeable odor, suggesting its common name, the thick,
shell-like spathe enclosing the large, rounded spadix, the
ample leaves, and numerous long, fleshy roots, arising
from the thickened rootstock, mark this as an exceed-
146 STUDY OF COMMON PLANTS.
ingly well-defined species. Record what you have ob-
served regarding the habitat and duration of the plant,
and any other characters not mentioned above. Do its
habits indicate that it is indigenous ?
Inflorescence and Flowers.
I. In studying the plant, remove the spathe, observing
meantime whether any special devices exist for the attrac-
tion of visitors.
II. Examine the spadix carefully, comparing it in plants
of different ages. The flowers are said to be proterogynous.
Is the statement confirmed by your observation ?
III. Satisfy yourself by a further comparison of speci-
mens whether self-fertilization is possible.1
IV. Examine the individual flowers, making sections
for this purpose that will show their structure and rela-
tion to the axis of inflorescence. Are all the flowers
perfect? How do the stamens of older flowers differ from
those less developed ?
V. Construct a diagram showing the plan of the flower.
CALL A. Richardia Africana, Kunth.
Compare the inflorescence and flowers of the cultivated
calla with those of the preceding species. Note
I. The color and form of the spathe.
II. The structure of the flowers. Are they perfect?
Are there any floral envelopes ?
III. How do those of the upper part of the spadix com-
pare with those of the lower portion ?
1 Cf. Trelease, Am. Nat., September, 1879.
THE ARUM FAMILY. 147
A comparative study should be made of such other
aroids as can be procured, e.g. sweet-flag, water-arum, etc.
Aside from the peculiarities of their inflorescence, which
mark them as a unique group, the acrid properties of
many members of this family constitute a marked feature.1
1 Miiller, Fertilization of Flowers, pp. 562-565, should be consulted.
Some interesting facts and suggestions are given by Allen, Flowers and
their Pedigrees, pp. 236-266. Certain peculiarities of fruits and seeds
may be looked for as different genera are examined, such as
1. The gelatinous outer surface of the fruit of Peltandra.
2. The seeds, — albuminous in some genera and exalbuminous in
others.
3. The embryo, — green in a number of genera.
148 STUDY OF COMMON PLANTS.
XVII. THE LILY FAMILY. LILIACE^E.
MATERIAL REQUIRED.
Yellow adder's-tongue, Erythronium Americanum, Ker., in flower.
Representatives of other conspicuous genera of this family, as for
example : Convallaria, Ornithogalum, Smilacina, Uvularia, Lilium,
etc.
Taking any of the plants named above, when in full
bloom, examine the structure of the flower, studying it
whorl by whorl, as directed in the case of Trillium, Sec-
tion VI.
Comparison of even a few genera of Liliacese is sufficient
to show very wide differences of external features. At
the same time the regularity and fixed plan of the flower
afford constant and distinctive characters by which the
immediate recognition of the family is assured. The
student, however, should compare the flowers of a num-
ber of different species until their morphology is perfectly
familiar. This is the more important, inasmuch as the
flower of the Liliacese serves as a type with which to com-
pare the modified flowers of a number of related families
of monocotyledons.
The family includes about sixteen hundred species, in-
habiting chiefly the temperate and warmer regions of the
globe. Many of the most pleasing and widely cultivated
ornamental plants, among them the tulip, lily, hyacinth,
and lily-of-the-valley, belong to this family. With them
are also included such medicinal plants as aloe, sarsapa-
THE LILY FAMILY. 149
rilla, etc., and, among vegetables, the onion, asparagus,
and some others. The extraordinary extent to which the
vegetative organs have been modified, as illustrated by
the cladophylls of asparagus and Ruscus, indicate a com-
paratively remote origin, notwithstanding the relative sim-
plicity of the flowers, some of which, however, as the
Yucca, exhibit very remarkable relations to insects.
The student is advised to extend his acquaintance to as
many genera as possible, and to follow as far as opportunity
offers, the transitional stages through which it is believed
that the more highly developed ones have passed.1 See
Mliller's admirable review of the Liliaceee, Fertilization of
Flowers, pp. 558, 559, and the papers of Riley and Trelease,
third and fourth annual reports of the Missouri Botanical
Garden, 1892 and 1893.
1 A number of interesting points for comparison will present them-
selves as the family is studied.' e.g.
1. The nectaries which vary much in different genera.
2. Bulblets produced in the axils of the leaves of Lilium.
3. Wide differences of underground stems. Contrast the creeping
rootstock of Smilacina, Medeola, etc., with the bulb of Lilium and Scilla.
150 STUDY OF COMMON PLANTS.
XVIII. AMARYLLIS FAMILY.
AMARYLLLDACE^E.
MATERIAL REQUIRED.
Flowers of the cultivated Amaryllis in various stages of development.
Specimens should be selected that have just opened, others more
advanced, and still others that have been open a longer time. In
addition to these a single entire plant.
Other representatives of the family that are procurable, such as
Hypoxis, Galanthus, or Narcissus, in flower.
I. In what particular does the flower of the Amaryllis
differ from that of the lily ? From that of the Iris ?
II. How does the plant as a whole differ from those of
the Iridacese that you have studied ?
III. Compare a number of flowers of Amaryllis, in differ-
ent stages of development. What arrangements do you
find for cross-fertilization? To what class of visitors are
many of the plants of this family adapted ? 1
IV. Having examined as many plants of the Amarylli-
dacese as are to be had, enumerate the essential features
that they possess in common.
V. Finally point out the characters in which all three
families, Amaryllidacese, Iridacese, and Liliacese, agree.
The close relationship of these three families of plants is
obvious upon acquaintance with even a few species. The
i Cf . Miiller, Fertilization of Flowers, p. 560.
THE AMARYLLIS FAMILY. 151
/
first "differs from the Liliacese in the inferior ovary," and
approaches the simple forms of the Iridacese, which, how-
ever, are distinguished by having three stamens instead of
six.
NOTE. — Exercises of this kind should be introduced and frequently
repeated, as soon as the pupil is in possession of a sufficient number of
observations to make intelligent comparisons. By this means the impor-
tant fact will become impressed on the mind, that groups of related
families may be recognized by their common characters, precisely as groups
of related genera are.
152 STUDY OF COMMON PLANTS.
XIX. THE IRIS FAMILY.
MATERIAL REQUIRED.
Blue flag, Iris versicolor, L., in flower.
Blue-eyed grass, Sisyrinchium angustifolium, Mill.
Cultivated Iris, Gladiolus, and Crocus.
BLUE FLAG. Iris versicolor, L.
Distribution and General Characters.
I. Does the plant manifest a decided choice of locality?
Is there anything to indicate whether it is an indigenous
species ?
II. Notice the form and arrangement of the leaves.
They are described as equitant. When studying other
species recall this peculiarity, and observe whether it is
characteristic of the family. How do the bracts that
subtend the flowers compare -with the stem leaves?
III. Write a description of the plant as a whole, includ-
ing rootstock, stem, and leaves.
Flower.
I. Study first the morphological characters.
1. Look over the flower, whorl by whorl, and see
whether you recognize each part.
2. Determine the plan. How many divisions of the
perianth are there? How many stamens and
styles? Does the plan of the flower differ in any
particular from that of the lily (or Trillium)?
THE IRIS FAMILY. 153
3. Study carefully the modifications exhibited by this
flower, as compared with the lily taken as a type.
Have any parts been suppressed ? Does adnation
occur? What are some of the most striking pecu-
liarities of form and structure ?
II. Examine each part in detail with reference to the
arrangements for cross-fertilization.
1. Enumerate the attractive features.
2. Ascertain whether there is a store of nectar, and if so
whether there are any path-pointers to direct visit-
ing insects towards it.
3. Observe particularly the position of stamens and
stigma.
a. Position of the anther and its mode of dehiscence.
b. Location of the stigmatic surface. Examine
under a good lens.
" The curved style-branches have at their tip a small
deltoid crest which turns slightly backward. Under this
there is a thin shelf, the upper surface of which is covered
with minute hairs, and is moistened with a sticky secretion.
This shelf is the true stigma." Verify this description as
given by Dr. Goodale, Wild Flowers of America, p. 34.
What do all these peculiarities of structure, color, and
arrangement suggest? Do you regard self-fertilization as
possible in this species? If you infer that cross-fertiliza-
tion takes place, show how this is probably brought about.1
BLUE-EYED GRASS. Sisyrinchium angustifolium, Mill.
This species is widely distributed, and continues to
flower for some weeks, so that it can usually be obtained
for comparison.
1 Cf. Gray, How Plants Behave, pp. 21, 25 j Miiller,' Fertilization of
Flowers, p. 543 et seq.
154 STUDY OF COMMON PLANTS.
I. With entire specimens make a careful study of the
blue-eyed grass, noting all the points in which it agrees
with the Iris or differs from it.
1. Compare the essential organs as to number, position,
and structure.
2. How does the perianth differ from that of the Iris ?
3. Compare leaves, stem, and roots.
II. Record concisely the results of your comparative
study of the two genera, taking care to bring out the
really essential features that indicate their relationship.
In like manner compare with the two preceding species
any other plants of this family that can be procured,
as the cultivated Gladiolus or Crocus. Some of the latter
open early in the spring, and the study of the Iridacese
may begin with them if more convenient. After studying
as many representatives of the family as practicable,
summarize your observations in a brief synopsis of the
characters common to them all. As a subject of special
investigation, a comparative study of the arrangements for
fertilization in the Iridacese is suggested.
THE ORCHIS FAMILY. 155
XX. THE ORCHIS FAMILY. ORCHIDACEJE.
MATERIAL REQUIRED.
Yellow lady's-slipper, Cypripedium pubescem, Willd., and Arethusa,
Arethusa bulbosa, L., in flower. Other species of Cypripedium may
be substituted for the former, and Calopogon or Pogonia for the lat-
ter. If it is impossible to obtain indigenous species, various trop-
ical orchids can be procured through florists in the larger cities,
who will deliver them safely at a distance. The expense is of
small moment compared with what is gained by having a familiar
acquaintance with at least two or three representatives of a family
of plants in which mechanical contrivances for securing cross-
fertilization have been carried to the highest degree of perfection.
YELLOW LADY:S-SLIPPER. Cypripedium pubescens, Willd.
Flower.
Our study will be restricted to the flower, which, though
greatly modified, has departed from the type less than those
of other genera, and remains " as a record of a former and
more simple state " of the great family to which it belongs.1
I. Notice first the most conspicuous external features.
1. The nodding flower, generally single, terminating
the leafy stem.
2. The floral envelopes.
a. Three sepals, of which the upper one is the
largest, the two lower united into one, but
showing at the apex a trace of their original
separation.
1 Darwin, Fertilization of Orchids, p. 226.
156 STUDY OF COMMON PLANTS.
b. The petals, of which the two lateral ones resemble
the sepals, but are narrower and more or less
twisted, while the lower1 is developed into a
large sac, the lip or labellum.
3. The essential organs. These have been greatly
modified, and are united above into an organ
called the column. Note
a. The three stamens, the single sterile one forming
a broadly triangular body, the apex of which
projects slightly into the opening of the label-
lum, and the two lateral fertile ones, each
with a large anther on the under side.
b. The fleshy stigma, arching under the sterile
stamen, the stigmatic surface covered with
minute papillae. This is seen to better advan-
tage after the removal of »the floral envelopes.
II. Having learned the parts of the flower, endeavor
next to understand their homologies. Such a study is
extremely interesting, showing as it does " how curiously
a flower may be moulded out of many separate organs, —
how perfect the cohesion of primordially distinct parts
may become, — how organs may be used for purposes
widely different from their proper uses, — how other
organs may be entirely suppressed, or leave mere useless
emblems of their former existence, — and finally . . .
how enormous has been the amount of change which these
flowers have undergone from their parental or typical
form."2
1 "The lip (in the Orchidacese) is really the upper petal, i.e. the one
next to the axis, but by a twist of the ovary of half a turn it is more com-
monly directed forward, and brought next to the bract."
2 Darwin, I.e., p. 234.
THE OKCHIS FAMILY. 157
1. Compare the flower throughout with that of the lily
(or Trillium) previously studied, endeavoring to
ascertain the character and extent of its modifi-
cations.
a. How does the ovary compare with that of the
lily as regards adnation of the floral envel-
opes?
b. In what parts of the flower has coalescence oc-
curred ?
c. Has suppression of any parts taken place ?
d. Point out the most striking modifications of
form.1
2. Construct a diagram and compare with that of the
NOTE. — The student cannot hope to understand all of this at
once. The distance between the lily and the lady's-slipper is too
great to be bridged by a single effort of the imagination. Let him
do his best with the flower itself, then read the references, then lay
the whole matter aside, and return to it again after other representa-
tives of tthe family have been studied.
III. The striking modifications of the flower of Cypri-
pedium are correlated with the visits of insects on which
it is dependent for fertilization.
1. There are certain peculiarities likely to prove attrac-
tive to insect visitors. Enumerate these.
2. Assuming that an insect, a bee for example, is about
to pass into the interior of the labellum, where
would it be likely to enter? Would it probably
pass out by the same opening ?
3. Examine carefully the structural peculiarities of the
lip. Find where the tissue is thinnest, and accord-
1 Cf. Gray, Structural Botany, p. 179 et seq.
2 Cf. Goodale, Wild Flowers of America, p. 86 ; Darwin, Fertilization
of Orchids, pp. 234-246.
158 STUDY OF COMMON PLANTS.
ingly where the most light is admitted. If the
insect crawling on the floor of the labellum moves
towards the part that is best lighted, which direc-
tion will it take ? Are there any path-pointers ?
4. Examine more closely the pollen masses. Notice
particularly their adhesive inner surface. Observe
the form and structure of the stigma, and see
how the pollen is retained when applied to its
surface.
5. Endeavor to interpret these peculiar arrangements.
If practicable, observe the action of visiting
insects.1
ARETHUSA. Arethusa bulbosa, L.
Study the flower as directed in the case of Cypripedmm,
with reference to
I. External features, such as form and position of parts,
color, odor, etc.
II. Morphological characters.
Examine each whorl critically. Determine the plan of
the flower and no.te modifications. In what important
particular does the andrcecium differ from that of Cypripe-
dium?
Construct a diagram, and compare with that of the
flower of Cypripedium.2
III. Physiological adaptations.
While plainly dependent on insects for fertilization, the
flower of Arethusa presents a very different mechanism
from that of Cypripedium. Examine carefully the rela-
1 Cf. Miiller, Fertilization of Flowers, pp. 539-542 ; Gray, Am. Jour.
Sci., XXXIV (1862), pp. 420-429 ; Darwin, I.e., p. 230.
*Cf. Goodalc, I.e.
THE ORCHIS FAMILY. 159
tive position of anther and stigma, and endeavor to make
out for yourself how this arrangement prevents the appli-
cation of its own pollen to the stigma of a given flower,
and at the same time favors cross-fertilization.1
RELATIONSHIP.
This large family of plants includes about three thousand
species, widely distributed in both hemispheres, and show-
ing the highest specialization of the flower yet attained in
the vegetable kingdom. Many of the most conspicuous and
curious kinds are tropical epiphytes, and are frequently
cultivated in conservatories. As Miiller points out, the
family is remarkable for the great differences of habit
exhibited by the different species, the extraordinary modi-
fications of its flowers, and the great number of seeds
produced in a single fruit. The differences of habit, some
being epiphytic, others saprophytic, and so on, indicate
great capacity of the vegetative organs for variation, and
the modifications of the flowers are manifestly correlated
with the visits of insects. Cross-fertilization is the rule,
but here again " orchids show the greatest possible differ-
ences, all of which, however, are linked together by inter-
mediate conditions. We find in this order, cleistogamic
flowers and o'pen flowers ; flowers regularly or occasionally
self-fertilized ; others never self-fertilized, though quite
fertile to their own pollen if it be applied artificially ;
flowers absolutely sterile to their own pollen, though fer-
tile not only to the pollen of their own species but even to
that of other species of their own genus ; finally, species
in which pollinia and stigma of the same individual act
as fatal poisons to one another." 2
1 Cf. Gray, How Plants Behave.
2 Miiller, I.e., pp.527, 528.
160 STUDY OF COMMON PLANTS.
The homologies of the flowers of orchids have been
discussed at length by Darwin and others. The following
may be given as a brief resume of the most essential facts :
Comparing the flower of an orchid with a simpler one,
such as a lily, the several whorls are seen to have under-
gone varying degrees of modification. The three sepals
are readily identified, although they are usually petal-like
in structure, and two, or sometimes all three, may have
undergone coalescence. Of the three petals, the two
lateral ones are alike, while the third, called the lip, is
enlarged and differs widely in form from the other two.
The essential organs are consolidated into a single body,
the column. In the genus Cypripedium one stamen has
become abortive, while the two remaining ones produce
pollen ; in the other genera of the family only one stamen,
as a rule, is perfect. The ovary shows its origin in three
carpels ; but it is one-celled, and the three placentae are
parietal.
Theoretically it is held that originally the stamens were
in two whorls of three each, and that in Cypripedium the
staminode (abortive stamen) belongs to the outer whorl
and the two fertile ones to the inner, while in other
genera, in the great majority of cases, this relation is
reversed. For a brief but satisfactory statement of this,
with good diagrams, see Luerssen, Botanik, p. 469.
THE WILLOW FAMILY. 161
XXI. THE WILLOW FAMILY. SALICACEJE.
MATERIAL REQUIRED.
Branches of the earliest flowering willow, Salix discolor, Muhl., gath-
ered in the early spring before the leaves appear. Specimens
with both staminate and pistillate flowers are wanted. (Salix
cordata, or other species may be substituted.) Similar branches
of different kinds of poplar, Populus tremuloides, Michx., and
other species.
WILLOWS.
General Characters.
Beginning with the willows, observe the various exter-
nal characters, such as
1. Form and structure of buds.
2. Color of the bark. Is it smooth or rough ?
3. Texture of the twigs. Are they lithe or brittle ?
NOTE. — Such characters are frequently of much more impor-
tance than they appear to be at first sight. The twigs of some
species of willows are extremely brittle at the base, and being
easily detached serve as a means of propagation ; while their color
and surface are sometimes so characteristic as to become an impor-
tant factor in classification.
Flowers.
I. Examine first the staminate catkins.
1. Ascertain what constitutes the individual flower.
(Each flower is subtended by a small hairy scale.)
Under a lens determine
a. The shape of the scale.
b. Whether the margin is cut or entire.
162 STUDY OF COMMON PLANTS.
c. Where the numerous silky hairs are attached.
2. Study the flower itself.
a. How many stamens are there ?
b. Is a nectary (organ that secretes nectar) present?
II. Examine next the pistillate catkins.
1. In what respects do they differ from the staminate
ones ? Are the scales alike in both ?
2. Note the peculiarities of the pistil.
a. Its form.
b. Stalked or sessile ?
c. Number and form of stigmas.
d. How many carpels compose the ovary ?
e. Is there a nectary ?
III. Are the flowers visited by insects? Enumerate the
attractions adapted to secure insect visits.1
Fruits.
When the fruits are ripe, observe their structure and
mode of dehiscence, the attachment of the seeds and their
peculiarities, particularly their means of dissemination.
Comparison with Other Species.
Some days later, as soon as they are in proper condition
for examination, study the catkins of other kinds of willows
(Salix cordata, Muhl., S. lucida, Muhl., or other available
species), and note all the characters in which they agree
with the species already studied.
POPLARS.
In the same manner make a careful study of one or
more common species of poplar and compare them with
the willows.
1 Cf Muller, Fertilization of Flowers, p. 524.
THE WILLOW FAMILY. 163
I. Note first their external characters and habits, and
notice in what respects they differ from those of the wil-
lows. Compare
1. Bark.
2. Buds, particularly the surface of the bud-scales.
3. Leaves.
4. Branches, as to size, texture, and surface marking.
II. Carry out, step by step, a thorough comparison of
the inflorescence and flowers.
1. How do the scales of the poplar catkin differ from
those of the willows ?
2. Do the flowers of the poplar have any structure that
is wanting to those of the willows ?
3. Compare the number of stamens in the two genera.
4. Are their fruits and seeds essentially alike ?
III. Finally, after several species of each have been
studied, record all the characters in which willows and
poplars agree. The characters exhibited by all of them in
common are those of the willow family (Salicacese).
SPECIAL STUDIES.
I. Determination of species of poplar, by means of
winter buds.
II. Recognition of different species of willow by size,
habit, and other external features.
NOTE. — The identification of willows and poplars is attended with
some difficulty, requiring long practice and the exercise of critical judg-
ment ; but it is desirable that even beginners should observe how readily
the large-toothed aspen, Populus grandidentata, may be distinguished
from Populus tremuloides by its bud-scales, how Salix lucida is at
once recognized by its leaves, and how Salix alba and Salix nigra
are distinguishable from other species by their size and from each other
by their habit, even at a distance. Simple exercises of this sort may be
introduced occasionally with great advantage.
164 STUDY OF COMMON PLANTS.
XXII. THE CROWFOOT FAMILY,
RANUNCULACEJE.
MATERIAL REQUIRED.
Specimens of the early crowfoot, Ranunculus fascicularis, Muhl., some
in flower, others in fruit.
Similar specimens, as they can be obtained, of Anemone nemorosa, L.,
and Caltha palustris, L.
Representatives of other genera, such as Hepatica, Clematis, Aquilegia,
Actsea, Hydrastis, etc.
EARLY CROWFOOT. Rununculus fascicularis, Muhl.
Distribution.
Record what you have observed as to the habitat of this
species. For the use of the term habitat cf. Gray, Struct-
ural Botany, p. 366. Do you regard it as indigenous or
introduced ?
NOTE. — This is often a difficult question to settle. We have to de-
pend partly on recorded observations and partly on what we now see of
the habits of the plant, the places where it grows, the direction in which
it spreads, and so on. Trustworthy evidence is attained when competent
botanists actually observe for a period of years and record the stations
occupied by the species in question.
Observations of this kind are of much interest, and if properly con-
ducted may be made of great scientific value. Constant changes in the
vegetation of a given locality are taking place, due either to the introduc-
tion of foreign species or to the disappearance of indigenous plants, as
the result of changed climatic and other conditions. Some introduced
plants have so taken possession of territory invaded by them as to become
formidable rivals of the native species, and even to crowd them out. The
Canada thistle, prickly lettuce, butter-and-eggs, hound's tongue, and
THE CROWFOOT FAMILY. 165
many others are among the undesirable accessions to our native flora,
some of them extending over wide areas in the course of a few years.
In collecting data regarding the distribution of a species, you should
first of all record where you have seen the plant growing. To this add
any observations you may have made as to its choice of locality, be-
havior from year to year, increase in number, liability to extermination,
etc. To be accepted as trustworthy, notes of this kind must be accom-
panied by specimens.
With perfect specimens at hand examine the parts of
the plant in order.
Koots.
Describe their shape. What direction do they take?
How do those of last year differ frotai those of the present
year? Are there any fine, fibrous roots? if so, where do
they arise ?
NOTE. — A comparison of different specimens shows an interesting
division of labor.
The smaller fibrous roots absorb from the soil water and crude mate-
rials that are passed on to the leaves. In the latter, starch and other
reserve substances are produced, and are then carried down to the spindle-
shaped roots where they are stored until the next year. At the time of
flowering the roots of last year have already become exhausted, and look
old and wrinkled, while the new ones that are to take their place have
not nearly attained their full size. There are, then, three different sets
of roots performing as many different functions. One set is absorbing,
another is feeding the rapidly growing plant, and the third set is develop-
ing into a storehouse in which will be laid up during the summer a supply
of food for future use.
Leaves.
Most of the leaves arise from a very short stem, and
appear as if they grew directly from the roots ; accord-
ingly they are described as " radical." One or more leaves
are borne on the flowering stems and are spoken of as
"cauline,"
166 STUDY OF COMMON PLANTS.
I. Describe first the radical leaves. Compare specimens
and see whether the same description will answer for all
of them.
II. Examine the cauline leaves of a number of different
individuals and note the various forms.
III. Are there any means of protection ?
NOTE. — Do not answer the question hastily. Hairs on delicate plants
sometimes protect their tissues against cold, sometimes against small,
soft-bodied animals that might devour them or climb up to the flowers
and steal the nectar, and again, the presence of acrid juice may render
them distasteful to grazing animals. See, if you can, whether this plant
is protected in any or all of these ways.
Flower.
Study first the plan of the flower. Are all the parts
present? Is it a " regular " flower ? Has any consolida-
tion of parts taken place, or are they all free and distinct ?
Describe by a single word the insertion of the floral en-
velopes.
Next, examine and describe in detail the successive
whorls.
I. Calyx. How many sepals are there? Is this num-
ber constant? Describe their shape, color, and surface.
How does their position on the flower bud correspond with
that taken when the flowers are fully expanded ? From
its earlier condition do you infer anything as to the func-
tion of the calyx ?
II. Corolla. Does the number of petals correspond
with the number of sepals ? Remove two or three and
examine them under a lens. Draw one in outline, taking
care to represent the little scale near the point of insertion.
Examine the scale carefully. Lift up the free edge
with the point of a needle. Frequently a small drop of
THE CROWFOOT FAMILY. 167
nectar can be found at its base. The whole arrangement
constitutes a simple and efficient device for protecting the
nectar, and, at the same time, leaving it accessible to visit-
ing insects.
III. Stamens. How many? Are they all alike? In
what order do they ripen? Study under a lens the mode
of dehiscence of the anthers. It will usually be found
that such facts, apparently trivial, are really important.
In the present case, after the oldest stamens begin to
shed their pollen, some little time elapses before the
youngest ones are mature, thus ensuring a supply of
pollen for visiting insects several days in succession, and
insects climbing over the flowers can hardly fail to carry
pollen from one to another.
IV. Pistils. Study these in flowers of different ages.
It will be an advantage to make longitudinal sections of
the flower. Notice
1. The elongated axis, receptacle, on which the pistils
are inserted.
2. The shape of the pistils. Draw an enlarged outline
of one.
8. In those that have been properly sectioned the single
ovule. Examine the latter in still older specimens
and satisfy yourself regarding its form, point of
attachment, and direction taken in the ovary.
Compare mature fruits and seeds if they are to
be had.
Read Miiller, Fertilization of Flowers, p. 74 et seq.
RELATIONSHIP.
We have next to study some of the immediate relatives
of the early crowfoot. This may be done at the same
168 STUDY OF COMMON PLANTS.
time, if specimens are procurable, otherwise comparisons
should be deferred until a full supply of material is at
hand.
I. We take first the wood anemone, Anemone nemo-
rosa, L.
The anemone rises from a creeping rhizome that gives
off fine, fibrous roots. The simple stem bears a three-
leaved involucre and a single conspicuous flower. Each
leaf of the involucre is petiolate, without stipules, and
divided into three leaflets that are variously cut and
toothed, the lateral ones often divided nearly or quite to
the base. Similar radical leaves arise from the rhizome.
The flower has a calyx consisting of five or six (frequently
more) white sepals, that are often tinged with pink, many
distinct stamens, and a less number of carpels (15-20).
See if your specimens agree throughout with the de-
scription just given. Name all the points in which the
anemone and early crowfoot agree and those in which
they differ. Incidentally observe the arrangements for
securing fertilization.1
II. Continuing our comparative study, we next take
the marsh marigold, Caltha palustris, L., and in the same
way compare it throughout with the anemone and early
crowfoot, noting as before all points of difference and
resemblance. Widely as the vegetative parts differ, it
is obvious that the flowers of all three species are almost
identical in their essential structural features.
The marsh marigold presents several attractive features,
and cross-fertilization is effected through the agency of
insects, but self-fertilization may also take place. Cf.
Miiller, pp. 79, 80.
i Cf. Miiller, Fertilization of Flowers, pp. 72, 73,
THE CROWFOOT FAMILY. 169
III. If practicable, the comparison should be extended
to a number of other species belonging to different genera,
as, for example, Hepatica triloba, Chaix, Anemonella thalic-
troides, Spach, Clematis Virginiana, L., Aquilegia Cana-
densis, L., Actcea alba, Bigel, Hydrastis Canadensis, L.,
and any other plants of this family, wild or cultivated,
that may be available.
CHARACTERS OF THE RANUNCULACEJB.
After such a comparative study, embracing as many
species as possible, we may sum up the characters that
distinguish members of this family as follows :
1. Chiefly herbaceous plants.
2. Juice watery, in many species acrid and poisonous.
3. Leaves generally compound or variously cut and
divided, without true stipules, but frequently
dilated at the base.
4. All parts of the flower free and distinct. Corolla
oiten wanting, floral envelopes and numerous
stamens hypogynous.
5. Carpels numerous or few, forming achenia, berries,
or follicles in fruit.1
This family of plants is of interest in many ways.
Owing to their active properties many of the species
such as gold-thread, black hellebore, aconite, larkspur, and
Hydrastis are employed medicinally. In fact these active
properties constitute an important feature of their relation-
ship. The order furnishes a number of ornamental plants
common in cultivation, such as Clematis, columbine, monks-
hood, and others. The color of the flowers, yellow and
white in many of the simpler species, passing into red and
1 Cf. Gray, Manual, p. 34.
170 STUDY OF COMMON PLANTS.
blue iii the more highly developed ones, taken in connec-
tion with the striking modifications of form by which the
latter have become more and more perfectly adapted to
the visits of insects, gives some support to the theory
called the Law of Progressive Coloration.1
SPECIAL STUDIES.
I. Colors of flowers belonging to the Ranunculacese.
II. Various degrees of adaptation to fertilization by the
agency of insects in this family. Is self-fertiliza-
tion possible in the majority of cases ? Is it impos-
sible in any species ?
III. Fruits of the Ranunculacese.
IV. Dissemination of seeds. Special arrangements in
Clematis and other genera.
1 Cf . Grant Allen, Colors of Flowers, pp. 17-60 ; Miiller, Fertiliza-
tion of Flowers, pp. 88, 89.
THE MUSTARD FAMILY. 171
XXIII. THE MUSTARD FAMILY. CRUCIFER^.
MATERIAL REQUIRED.
Entire plants of Shepherd's-purse, Capsella Bursa-pastoris, Mcench,
with both flowers and fruit.
Specimens of any of the following species that can be obtained :
Spring Cress, Cardamine rhomboidea, DC. ; Pepper-root, Dentaria
diphylla, L. ; Water Cress, Nasturtium officinale, 11. Br. ; Sweet
Alyssum, Alyssum maritimum. Lam.; Rocket, Hesperis matronalis,
L. ; Peppergrass, Lepidium Virginicum, L. ; Hedge Mustard, Sisym-
brium officinale, Scop. ; Wild Mustard, Brassica Sinapistrum, Boiss.
SHEFHERD'S-FURSE. Capsella Bursa-pastoris, Moench.
Distribution.
Record your own observations as to the occurrence arid
habits of this plant. Does it manifest a preference for
any particular soil or locality ?
General Characters.
Write an accurate description of the root, stem, leaves,
and inflorescence.
Flower and Fruit.
I. Study the plan of the flower, noting the number and
arrangement of sepals, petals, and essential organs. Show
the application of the word "cruciform" as used to
describe the corolla. Are the stamens all alike ?
II. Examine the structure of the ovary. Compare it as
it appears in the flower, with partially and fully developed
172 STUDY OF COMMON PLANTS.
fruits. How many carpels are there ? Attachment,
direction, and form of ovules? Mode of dehiscence?
How is the fruit to be classified ?
III. Construct a diagram of the flower.
IV. Compare the views of different writers regarding
the morphology of the flower of Cruciferse.1
RELATIONSHIP.
I. Compare with shepherd's-purse such of the species
named above as can be procured, and determine what
characters they exhibit in common. Do they all have a
pungent juice? Are they all herbaceous? "Are the flowers
on the same plan ? How far do the fruits and seeds agree
in structure ?
II. Summarize the results of your observations in a
brief general description of cruciferous plants.
NOTE. — To complete this comparative study at all satisfactorily will re-
quire much time and patience. In studying the seeds it will be best to
obtain those of different genera from the seed store, sow a part of them
in moist sawdust, and dissect carefully from day to day. If the time is
short, it may be best to limit the comparison to a very few species, but
if even two or three genera are thoroughly studied, and the descriptions
accompanied by floral diagrams and sketches of the structure of fruits
and seeds, the student cannot fail to be impressed, as in no other way,
with the persistent and marked features of this remarkable group 01
plants.
The flowers of the Cruciferse, notwithstanding their
great uniformity of structure, exhibit striking physiologi-
cal differences. The number and position of the nectaries
is extremely variable. Some have a strong odor, and in at
least one species this is associated with evening expansion
1 Cf. Gray, Structural Botany, pp. 206, 207 ; Arthur, Barnes, and
Coulter, Plant Dissection, p. 238 (references in footnote).
THE MUSTARD FAMILY. 173
of the flower. One has become distinctly anemophilous,
although giving plain evidence of having descended from
entomophilous ancestors.1
1 Cf. M tiller, Fertilization of Flowers, pp. 100-114 ; Hooker, Nature,
Vol. X, p. 134 ; Eichler, Bluthendiayramme, pp. 200, 206.
174 STUDY OF COMMON PLANTS.
XXIV. THE ROSE FAMILY. KOSACEJE.
MATERIAL REQUIRED.
Flowering shoots of the cultivated cherry, and, as soon as they are
in full bloom, those of the peach, plum, apple, and pear.
Representatives of the following genera, as far as they can be ob-
tained in flower or fruit; Fragaria, Physocarpus, Potentilla, Geum,
Rubus, Rosa, Crataegus.
THE CHERRY. Prunus Cerasus, L.
Distribution.
The cultivated cherry is familiarly known in the north
temperate zone of both hemispheres. For the evidence
regarding the region to which it is indigenous, see De
Candolle, Origin of Cultivated Plants, pp. 206-210.
Flower and Fruit.
I. Study the parts of the flower in succession, noting
their form and insertion, the union of parts, and other
modifications if such exist.
II. Make a longitudinal section and draw it accurately,
Is any nectar to be found ? If so, are there any arrange-
ments for its protection ?
III. Make longitudinal sections of a number of ovaries
and transverse ones of others. Determine the number of
ovules, their form and place of attachment. Draw. Com-
pare the number of ovules in flowers just opened and in
those that are fading or have lost their corolla.
THE ROSE FAMILY. 175
IV. Construct a diagram of the flower.
V. Does the structure of the flower present any adap-
tations to the visits of insects ?
VI. How is the dissemination of seeds provided for ?
RELATIONSHIP.
I. With the cherry compare -first the cultivated plum,
in flower about the same time.
1. Note every point of difference between the two
species, giving special attention to the structure
of the flower.
2. Observe the points in which they agree.
II. Compare the flowers of the peach with those of the
cherry and plum, noting the features in which all agree
and those in which they differ.
III. Examine next the flowers of the pear or apple.
Make a longitudinal section, draw it and compare with
that of the cherry flower. Make successive cross-sections
of the ovary till one is found that shows the ovules clearly.
Draw and compare with similar sections of the ovary of
the cherry.
IV. Make a similar study of the flowers of the straw-
berry. Indicate all the points in which they differ from
those of the cherry and apple. Compare longitudinal
sections of all three.
V. Having made a further comparative study of as
many of the plants of this family as are available, sum-
marize the characters that you have found to be general,
taking leaves, fruit, etc., into account as well as the
flowers.
176 STUDY OF COMMON PLANTS.
If enough species have been examined the characters
thus derived will be those of the Rosacese or Rose Family,
a large and important natural order, furnishing a large
proportion of the fruits of the north temperate zone,
numerous ornamental species, among them the rose,
spiraea, hawthorn, and mountain-ash, and some medicinal
plants, including the wild cherry and others.
The flowers of the various genera exhibit interesting
peculiarities of color and structure corresponding to the
different degrees of adaptation to insect visitors.1
SPECIAL STUDIES.
I. Development of a cherry. This involves a study
of the ovary and its .changes during the entire
period of the formation of the fruit. Sections of
different specimens should be made at frequent
intervals, and a series of drawings kept with their
accompanying dates.
II. A similar study of the development of the apple.
III. How far the production of our domestic fruits is
dependent on the agency of insects.
IV. Evidence regarding the 4%'law of progressive colora-
tion " drawn from the flowers of this family.2
V. Collection and classification of the indigenous rosa-
ceous plants of the region in which the study is
carried on.
VI. Origin and varieties of the cultivated strawberry.
VII. Extra-floral nectaries and their use.
1 Cf. Miiller, Fertilization of Flowers, pp. 242, 243.
2 Allen, Colors of Flowers, p. 25 et seq.
THE PEA FAMILY. 177
XXV. THE PEA FAMILY. LEGUMINOS^.
MATERIAL REQUIRED.
Entire specimens of the wild lupine, Lupinus perennis, L., in flower.
Flowers, leaves, and fruits of some or all of the following species :
RoUnia Pseudacacia, L. ; Vicia Caroliniana, Walt. ; Trifolium pra-
tense, L. ; Melilotm alba, Lam. ; Lathyrus palustris, L. ; Lathyrus
odoratus, L.
WILD LUPINE. Lupinus perennis, L.
Distribution and General Characters.
Note locality and habits. Is this species indigenous or
introduced ? Describe in detail stem, leaf, and inflo-
rescence.
Flower.
I. How many divisions has the calyx? Is its surface
smooth or hairy ?
II. With a number of good specimens at hand, observe
in their natural position the parts of the corolla, their
form, color, and relations to each other. They have
received special names that must be made familiar. The
conspicuous upper petal is called the standard, vexillum,
the two lateral ones are the wings, alee, while the two lower
ones are united to form the keel, carina.
III. Examine critically each of these parts.
1. Are there any grooves or ridges on the standard? If
so notice their form and direction. See if there
178 STUDY OF COMMON PLANTS.
are any lines or dots likely to serve as path
pointers. Compare the color of the standard of a
number of flowers.
2. Observe the form and structure of the wings. Re-
move one and sketch its outline. In an unin-
jured flower, notice particularly how the wings
are fitted to the keel and standard.
IV. With a pencil, or other instrument, push the wings
downward with some force, imitating the action of a heavy
insect. Repeat the operation on different specimens until
its result is clearly seen.
V. See if you can understand how it is that the wings
and keel return to their position when the pressure is
removed, and whether there is any advantage in this.
VI. Examine next the structure and mechanism of the
essential organs.
1. Remove the floral envelopes from the side of the
flower, leaving the other parts undisturbed. The
stamens and pistil can now be studied to advan-
tage in their natural position.
2. Count the stamens. Are they monadelphous or dia-
delphous ? Are they all alike ? Compare those
of flowers about to open with younger and older
ones.
3. Look at the end of the keel of uninjured flowers.
Where is the pollen stored after the dehiscence
of the anthers ? Examine and describe the mech-
anism by which it is pushed out when the keel is
opened.
4. Observe next the shape of the pistil, the direction
taken by the style, and the surface of the latter as
seen under a lens.
THE PEA FAMILY. 179
5. Finally, with a number of perfect specimens of dif-
ferent ages, study the whole mechanism. Write
a complete account of the structure of the flower
and the mechanical arrangements favoring cross-
fertilization, making outline sketches whenever
it is necessary to render the description more
intelligible.1
RELATIONSHIP.
As the flowers of different plants belonging to the pea
family are to be had, compare their structure and mech-
anism with those of the lupine. Any of the species
named above, the common locust for example, in flower a
little later than the lupine, will present interesting points
for comparison.
1. Do corresponding whorls of the flowers of different
species agree as to position, form, and number of parts ?
2. Is the mechanism by which fertilization is accom-
plished essentially the same as in the lupine ?
3. In specimens that are past flowering, study the fruit
in early and later stages of development.
4. Observe the position and form of the ovules, and,
in older specimens, the mode of clehiscence of the fruit.
5. Aside from characters drawn from flowers and fruit,
determine whether leaves of the different species present
any common features.
6. Summarize the results of your comparative study in
a brief statement of the characters common to those mem-
bers of the Leguminosa3 that you have become acquainted
with.
1 Cf. Miiller's account of Lupinus luteus, the structure of which is
much like that of Lupinus per ennis. Fertilization of Flowers, p. 187.
180 STUDY OF COMMON PLANTS.
The Leguminosae constitute a large and remarkable
family of plants, including between six and seven thou-
sand species, distributed throughout the world, but most
abundant in tropical regions. Many of the species are of
economical interest. The various kinds of clover furnish
important forage crops, and peas, beans, and lentils form an
almost indispensable constituent of the food plants of the
world. Dye woods and drugs are yielded by a consider-
able number. Some are exceedingly poisonous, among
them the famoiis ordeal bean of Calabar. Botanically they
are of special interest for the peculiarities of the mechanism
by which their flowers are adapted to cross-fertilization.
A large proportion, too, of plants whose leaves exhibit
" sleep movements " belong to this family.
SPECIAL STUDIES.
I. Arrangements for cross-fertilization in the Legu-
minosse.
II. Extent to which the production of seeds of red
clover is dependent on the agency of insects.
III. Capacity of the common pea for self-fertilization.
IV. Occurrence of modified leaves, such as tendrils,
phyllodes, etc., among the Leguminosse.
V. Morphology of protective structures of various legu-
minous plants, e.g. spines of locust and honey
locust, prickles of Schrankia, and hairs of Des-
modium.
VI. Sleep movements of clover, lupine, and other plants
of this family.
VII. Affinities of the Leguminosse.
VIII. Causes of the wide distribution of this family.
IX. Varieties of cultivated peas and beans.
THE GERANIUM FAMILY. 181
XXVI. GERANIUM FAMILY. GERANIACE^E.
MATERIAL REQUIRED.
Specimens of horseshoe geranium, Pelargonium zonale, L., in flower.
Wild cranesbill, Geranium maculatum, L. ; Nasturtium, Tropceolum
majus, L. ; Touch-me-not, Impatiens fulva, Nutt., or cultivated
balsams that have not become double.
HORSESHOE GERANIUM. Pelargonium zonale, L.
Distribution.
The "horseshoe geranium" is universally cultivated.
In common with various other cultivated species of the
same genus, it is indigenous to southern Africa. Very
many varieties have been produced.
General Characters.
With good specimens, observe and describe the various
external features, such as
I. Mode of branching.
II. Leaf arrangement.
III. Presence or absence of stipules.
IV. Form of leaves.
Inflorescence.
Taking care to select plants the flowers of which have
not become double, compare inflorescences of different
ages, and ascertain the order of development of the flowers.
182 STUDY OF COMMON PLANTS.
NOTE. — Like many other facts usually treated as morphological, the
character of the inflorescence is of much physiological importance.
The successive opening of the flowers in regular order, instead of simul-
taneously, insures a much longer period of time during which fertilization
may take place, and their position and aspect when ready for pollination
are most frequently such as to render them conspicuous and easily acces-
sible to insect visitors. The latter, while gathering honey, are often
observed to proceed in a methodical manner corresponding to the order
of development of the flowers.
Flower.
I. Study the structure and plan of the flower. Is it
perfectly regular ?
NOTE. — Give special attention to this point. The beginnings of irregu-
larity are of great interest, since they give us a clue to the way in which
some of the most efficient mechanical contrivances in the vegetable king-
dom have originated.
II. Study next the ovary.
1. Cut transverse and longitudinal sections of ovaries of
various ages.
2. Make out the form and place of attachment of the
ovules.
3. In the partially developed fruit examine the imma-
ture seeds, and note the form and position of the
embryo, easily recognized by its green color.
4. Construct a diagram of the flower.
Physiological adaptations.
I. Examine with a good lens the surface of stem, leaves,
flower-stalk, and calyx. Are there any distinctively pro-
tective arrangements ?
II. In what ways is the inflorescence adapted to cross-
fertilization ? Notice the position of the open flowers as
contrasted with that of the flower buds. Effect of " mass-
ing."
THE (GERANIUM FAMILY. 183
III. Study the flower itself with reference to the same
question. Compare the color of different specimens and
varieties. Is there anything to indicate to a visiting insect
the way to the nectar ? Find the nectar-tube and explore
with a bristle.
NOTE. — Some specimens have a nectar-tube united with the pedicel
and easily recognizable on the outside, either by its color or by its form-
ing a longitudinal ridge. In others it is not readily found. Even flowers
of the same inflorescence differ in this respect.
IV. Compare the stigmas of older flowers with those in
which the anthers are just shedding their pollen. Are the
flowers proterandrous or proterogynous ? 1
V. Study the structure of the mature fruit, and ascer-
tain how the seeds are disseminated.
NOTE. — The geranium lends itself readily to experiments in cross-
fertilization, and the student who has opportunity is advised to cross two
widely different varieties and compare the growth and vigor of the crossed
seedlings with that of seedlings derived from self-fertilized flowers.
Read the chapter on Pollination in Professor L. H. Bailey's Nursery Book.
RELATIONSHIP.
I. Compare the plant just studied with the wild cranes-
bill, noting points of agreement and difference. Give
special attention to the flowers of the two genera, examin-
ing them whorl by whorl, until you are satisfied regarding
their differences. Record these in detail. Refer in this
connection to Miiller's2 or Lubbock's3 account of various
species of Geranium.
1 Cf. Darwin, Cross- and Self-fertilization in the Vegetable Kingdom,
p. 142.
2 Fertilization of Flowers, pp. 149-158.
8 British Wild Flowers in Eelation to Insects, pp. 43, 44, 72-74.
184 STUDY OF COMMON PLANTS.
II. Compare next the cultivated nasturtium, Tropceolum
majus, L., with the horseshoe geranium.
1. Note the very different habits of the plant, the pecu-
liarities of its foliage leaves, and means of pro-
tection.
2. Observe the structure and plan of the flower. Note
particularly the color of both calyx and corolla,
the guiding lines, nectar-tube, mode of guarding
the entrance to the latter, dichogamy, structure
of ovary, and number of carpels.1
III. In addition to the foregoing, study if possible one
or more indigenous species of Impatiens, or forms of the
cultivated " balsam " that have not become double. They
are of special interest as regards both the peculiar modi-
fications of the flower and the mechanism of seed dissemi-
nation.
1. Comparing the plan of the flower with that of the
species previously studied, try to ascertain whether
there has been consolidation or suppression of
parts, or both.
2. Does the structure imply adaptation 'to cross-ferti-
lization? Does dichogamy exist?
3. If opportunity permits, observe what visitors Impati-
ens has and their mode of operation.
4. Examine ripe fruits and investigate the mechanism
of seed dissemination. Is it the same in principle
as in Pelargonium and Geranium?2
NOTE. — " The relationship of Pelargonium with the closely
allied genus Geranium is obvious, but it differs in important
1 Cf. Lubbock, I.e., pp. 75, 76.
2 Cf. Duehartre, Elements de Botanique, p. 791.
THE GERANIUM FAMILY. 185
particulars from Tropaeolum and Impatiens, both of which, in
recognition of their wide departure from more primitive forms,
are now placed in separate families. The study of such a series
of forms is in the highest degree instructive, presenting as it
does very important evidence regarding the descent of these
peculiarly modified genera.
186 STUDY OF COMMON PLANTS.
XXVII. THE SPURGE FAMILY.
EUPHORBIACEJE.
MATERIAL REQUIRED.
Spurge, Euphorbia Cyparissias, L., and other species of Euphorbia.
Representatives of other genera of the same family as far as these
are procurable.
SPURGE. Euphorbia Cyparissias, L.
Distribution.
In what situation is this plant usually found growing ?
Have you observed anything as to its persistence from
year to year, where it has once become established ? Do
its habits indicate that it is an indigenous species ?
General Characters.
Study the general features of the plant and write a brief
description. In addition to the ordinary botanical char-
acters note particularly
1. The way in which new shoots arise.
2. The abundant latex in every part.1
3. The great variety of foliar organs — scale leaves,
foliage leaves, and floral leaves — and their form, position,
and color.
Inflorescence and Flowers.
The morphology of the flower in this family has been
the subject of much discussion and an extended literature.
1 Care should be exercised in handling spurges as the juice is poisonous.
THE SPURGE FAMILY. 187
Without attempting at the outset a critical theoretical
study, we shall simply undertake to observe the floral
organs as they are, and give to them their commonly
accepted names. Book descriptions and figures are best
left alone until the plant has been studied at first hand.
I. Observe first the general arrangement of the inflores-
cences. They are borne on long slender stalks that arise
close together near the apex of the stem, and present
collectively the general appearance of an umbel. Is it
strictly an umbel ?
II. The slender stalks each bear near their extremity a
pair of heart-shaped, yellowish, floral leaves. Notice care-
fully what there is above the floral leaves. Compare a
number of specimens of different ages. Do you find still
other floral leaves? If so, do they resemble the first pair
in shape and color ? Floral leaves of the second and third
order are of common occurrence. Do you find any of a
higher order?
III. Having found all the floral leaves, we come to the
inflorescence proper. It greatly resembles a small flower,
and was described as such by some of the older botanists.
The cup-shaped structure that looks like a calyx is really
an involucre. Notice the four "crescent-shaped glands"
and their position on the involucre.
IV. Remove enough of the involucre to expose the
small flowers within. Do this with several specimens of
different ages. With a lens, examine the minute staminate
flowers. Note their position and number, the form of the
anther, and the point where the short filament is con-
nected with the long pedicel. (Each staminate flower
consists of a single stamen, mounted on a distinct
pedicel.)
188 STUDY OF COMMON PLANTS.
V. The single pistillate flower is far more conspicuous
than the staminate ones. As the ovary develops it pro-
trudes beyond the involucre, so that the entire flower is
easily studied. Observe
1. The form of the ovary.
2. The number of styles and stigmas.
3. The number of cells in the ovary, as seen in cross-
section, and the number and position of the
ovules.
VI. With a number of entire plants review all that we
have learned about the species. See that all the facts are
clearly in mind, and that you are able to designate each
part by its proper name. Do you consider the plant well
adapted to* survive in the struggle for existence ? If so,
show how.
RELATIONSHIP.
With the species already studied compare other mem-
bers of the genus such as Euphorbia corollata, L., E.
marginata, Pursh, E. maculata, L., and one or more repre-
sentatives of other genera, as, for example, Acalypha
Virginica, L., and the cultivated castor-oil plant, Ricinus
communis, L. (The seeds of the latter are of large size,
and are more easily studied than those of the spurge.)
Having compared as many species as practicable, see
how far the characters you have found to be common
to all agree with the family characters as given in the
manuals.
Euphorbia Cyparissias is a familiar representative of a
large and peculiar family of plants. It is found in patches
by roadsides and old dwellings where it has escaped from
cultivation. Its copious milky juice, narrow leaves, and
tufted habit have given it the common name of " milk-
THE SPtJRGE FAMILY. • 189
moss," in addition to . that of " spurge," which it shares
with numerous other species of the same genus. The
family to which it belongs is chiefly tropical, and is one
of the few that are specially distinguished by their poison-
ous properties. Cases of poisoning as a result of handling
species cultivated for ornament are not infrequent. It
includes a number of species with powerful medicinal
properties, and others that furnish valuable food products,
while the fleshy Euphorbias, the Poinsettia, and others,
are well-known ornamental plants.
190 STUDY OF COMMON PLANTS.
XXVIII. THE MAPLE FAMILY. ACERACEJE.
MATERIAL ' REQUIRED.
Flowers of the different species of maples as they open in the spring.
Fruits of the sugar maple gathered after they have fallen from the
trees in the autumn. Fruits of the red and silver maples gathered
in the summer.
Leaves of all the species. Either fresh or pressed specimens of the
latter will serve.
Flowers.
The flowers of the red maple open early in the spring
arid may be taken first. Specimens should be gathered
from a number of trees so as to have the different forms of
flowers for comparison.
I. Observe the position of the flower bud and the color
and position of the bud-scales.
II. Compare the flowers of different trees. Select
first, for critical study, those that have well-developed
stamens.
1. How many divisions of the calyx are there? Of the
corolla ?
2. Is this number the same in all the specimens ? Does
it correspond with the number of stamens ?
3. How are the stamens inserted ?
4. Is there a pistil ?
5. Are there any organs for the secretion of nectar?
THE MAPLE FAMILY. 191
III. Next take specimens that have well-developed
pistils.
1. Are stamens present? If so, how do they compare
with those of the flowers previously studied ?
2. Are the floral envelopes alike in all the flowers?
3. Notice the form and structure of the pistil. How
many carpels are there? How many ovules in
each cell ?
IV. Compare with these the flowers of the silver maple,
noting carefully all the points of likeness and difference.
1. Are petals present?
2. Do .all the flowers have both stamens and pistils?
3. Is the ovary smooth or hairy ?
4. Does it agree in structure with that of the red
maple ?
5. Do different specimens exhibit any variation as to
the number of carpels ?
V. Compare flowers of the sugar maple, which open
some days later, with those of the red and silver maples.
1. Are there any differences as regards
a. Form and position of the flower clusters ?
b. Color of the calyx ?
c. Structure of the essential organs?
2. Are all the flowers of the same tree alike ? How is
it with those of the red and silver maples in this
respect ?
The maples are described as being " polygamo-dice-
cious." What is meant by this ? Do you find that
the facts correspond with the statement?
Fruits.
Study next fruits, taking first those of the sugar maple
gathered the preceding fall.
192 STUDY OF COMMON PLANTS.
With the fruits of the sugar maple, compare those of
the red and silver maples, noting all the external and
structural differences by which they may be distinguished.
Leaves.
Compare -the leaves of all three kinds until you are able
to distinguish the species at sight by means of the leaves
alone.
Finally review the observations made thus far, see if
anything is to be added, and write a complete account
of the characters common to all three species and also of
those peculiar to each.
*
SPECIAL STUDIES.
I. Critical comparison of the Box-elder, Negundo
aceroides, Mcench., with the maples. Does it have
the essential characters of a maple ?
II. Polygamous plants. Cf. Darwin, Different Forms of
Flowers on Plants of the Same Species, Chap. VII.
THE MALLOW FAMILY. 193
XXIX. THE MALLOW FAMILY. MALVACEAE.
MATERIAL REQUIRED.
Common mallow, Malva rotundifolia, L., in flower and fruit.
Other representatives of the family, such as Hollyhock, Althcea rosea,
Cav. ; Shrubby althaea, Hibiscus Syriacus, L. ; Musk mallow,
Malva moschata, L. ; Velvet-leaf, Abutilon Avicennce, Gaertn.
COMMON MALLOW. Malva rotundifolia, L.
Distribution.
In what situation is this plant generally found ? Have
you any evidence as to whether it is an indigenous or
introduced species ?
General Characters.
I. Study first the habits of the plant and note its char-
acteristic features.
1. The strong taproot.
2. Position and direction of the numerous branches.
3. Presence or absence of stipules.
4. Form and venation of leaves.
5. Position and character of inflorescence.
6. The remarkably strong bast fibers.
7'. Mucilaginous contents, particularly of the fruits.
II. Enumerate any advantages that this plant possesses
in competition with others. Is it easily eradicated? Why?
Is it attractive to grazing animals ?
194 STUDY OF COMMON PLANTS.
Flower.
I. Examine the flower in various stages of development.
Note
1. The plan of the flower and how modified.
2. The three-leaved involucel, "like an outer calyx."
3. Insertion of the corolla and the relation of the latter
to the stamen-tube (best seen on longitudinal sec-
tion).
4. The monadelphous stamens.
5. Form and mode of dehiscence of anthers.
6. Number of stigmas. Does this correspond with the
number of divisions of the ovary?
II. Ascertain whether there are any adaptations favor-
ing cross-fertilization, or any that render self-fertilization
impossible.
1. Are there any guiding lines?
2. Is nectar produced? If so, is it protected in any
way?
3. Compare flowers of different ages and ascertain
whether dichogamy exists.1
Fruit and Seed.
I. Examine the fruit, making both transverse and longi-
tudinal sections of specimens of different ages. Ascertain
1. The number of carpels.
2. Form and place of attachment of the ovules.
3. Structure and position of the embryo. (This is
easily made out with a lens by means of repeated
sections, trying different specimens until the most
favorable ones are found.)
1 Lubbock, British Wild Flowers in Relation to Insects, p. 41 ; Miiller,
Fertilization of Flowers, pp. 142, 143.
THE MALLOW FAMILY. 195
II. Ascertain approximately the number of seeds pro-
duced by a single strong plant.
RELATIONSHIP.
Compare with the common mallow at least one, and if
possible several, of the plants named above, noting the
various points of difference and likeness. Write a brief
summary of the characters common to them all.
The Malvaceae exhibit a number of interesting peculiari-
ties, some of which indicate relationship with several other
families, among them the Tiliacese. They are widely dis-
tributed in both hemispheres, but with a preference for
the warmer parts of the globe. The cotton plant is the
most important member of the family, from an economical
standpoint. A few species are of medicinal value, and a
considerable number, as Althaea, Hibiscus, Abutilon, and
others, are well-known ornamental plants.
196 STUDY OF COMMON PLANTS.
XXX. THE VIOLET FAMILY. VIOLACEJE.
MATERIAL REQUIRED.
Specimens of the cultivated pansy in flower. Indigenous species of
violets.
Flower.
Our study in the present case will be restricted to the
flower, taking first that of the pansy.
I. Compare several good specimens as to size and color,
and observe how far* they agree.
II. Study the external features of the flower in order.
Note the number of parts in each whorl, and their peculiari-
ties of form, structure, and position.
1. Form of the sepals. Aside from their size and
position are they readily distinguished from foliage
leaves ?
2. Peculiarities of the corolla. To which of the petals
does the spur belong ? Cut into it and see whether
it contains anything likely to be of use to the
flower. What do you conclude as to its function ?
3. Study the disposition of colors. Compare as many
specimens as practicable. Where do the " guiding
lines " converge ?
4. Examine the center of the flower with a lens.
Notice the thick brush of hairs on either side.
The position of the essential organs, partially
visible farther in.
THE VIOLET FAMILY. 197
III. Remove carefully the floral envelopes on one side
so as to expose the essential organs without disturbing
them. Notice the relative position of stamens and pistil,
and their structural peculiarities. The large, rounded
stigma with an orifice in front. The " lip " forming the
lower edge of. this orifice. The syngenesious anthers arid
their membranaceous connectives united into a tube just
back of the stigma. The two nectaries projecting into the
spur. The narrow canal lined with hairs leading from the
entrance of the corolla back to the spur.
Jar the btamens and see where the pollen falls out and
where it lodges.
IV. Go over all the structures again, in more than one
specimen, and see if you can determine the use of each
part of the mechanism. Imitate the action of a bee by
inserting a slender piece of quill or wood, pushing along
the groove down to the nectar cavity. Withdraw it and
see if it brings away any pollen. Insert it into another
flower and examine the stigma of the latter with a lens
before and after the operation to see if any pollen has been
left on it.1
V. Make a true longitudinal section of the flower (a
razor is best for this purpose), and sketch the parts in out-
line so as to show their relative position. Name and
locate each, using letters and guiding lines.
VI. Make a transverse section of the ovary and examine
under a lens. Note
1. The number of placentae.
2, Number, direction, and form of ovules. If practi-
cable, compare ripe capsules.
1 Cf . Sachs, Physiology of Plants, p. 795.
198 STUDY OF COMMON PLANTS.
VII. Construct a diagram of the flower. In what
respects does the pansy differ from a "typical flower,"
as described by Gray, Lessons, pp. 81, 82 ?
VIII. Write a full description of the pansy.
NOTE. — It is hardly necessary at this stage of the student's progress
to remind him that a description of such a flower involves much more
than an enumeration of the parts of each whorl, with an account of
their surface, outline, etc. An appreciation of the marvelous beauty and
exquisite adaptations here displayed, and a scientific temper that seeks
to know how all this has come to be as it is, will hardly be satisfied with
mechanically filling the blanks of some "plant analysis." Write as
though your account were to stand as the only written description of
the result of a long series of natural experiments, of which we now see
the culmination in a perfect piece of mechanism.
IX. Consult the references already given and those
named under " Special Studies " below.
RELATIONSHIP.
As the flowers of various indigenous species appear in
spring, e.g. Viola palmata, L., V. pedata, L., V. pubescens,
Ait., etc., compare them with the pansy, and note the char-
acters common to them all. If the green violet, Solea con-
color, Ging., is to be had, compare this with the true violets.
Summarize briefly the points in which all these agree.
SPECIAL STUDIES.
I. Observation of various insects that visit the pansy.
Miiller, Fertilization of Flowers, p. 118, gives an
interesting account of the habits of different bees.
II. Advantages of crossed over self-fertilized pansies.
See Darwin's experiments, Cross- and Self-fertili-
zation in the Vegetable Kingdom, pp. 123-128, 286,
296, 304.
THE VIOLET FAMILY,, 199
III. Variation as seen in the cultivated pansy. Obser-
vations of differences of size, shades, and distri-
bution of color and other peculiarities, even if
restricted to the pansies grown in a single town,
give a vivid impression of the extraordinary capac-
ity for variation and the equally remarkable per-
sistence of essential features exhibited by this
species.
IV. Dissemination of seeds by different species of violets.
See Lubbock, Flowers, Fruits, and Leaves, p. 54
et seq.
V. Cleistogamic flowers. See Darwin, Different Forms
of Flowers on Plants of the Same Species, Chap.
VIII.
200 STUDY OF COMMON PLANTS.
XXXI. THE EVENING-PRIMROSE FAMILY.
ONAGRACEJE.
MATERIAL REQUIRED.
Evening primrose, CEnothera biennis, L., in flower.
Fire-weed, Epilobium angwlifolium, L., Enchanter's-nightshade, Cir-
ccea Lutetiana, L., and other representatives of the family, such
as the cultivated Fuchsia.
EVENING PRIMROSE. CEnothera biennis, L.
Distribution.
Where were the specimens obtained? In what other
places in this country have you seen it growing? Does
it grow in any other parts of the world ? 1
Flower.
I. Examine the whorls in order and draw a diagram of
the flower. Cut a true longitudinal section, study care-
fully the relation of the parts, and draw.
II. Note particularly the very long calyx-tube, insertion
of petals and stamens, the versatile anthers, elongated
style, and four thickened divisions of the stigma.
III. Taking specimens past flowering, cut transverse
and longitudinal sections of the ovary, and observe under a
lens the number of rows of ovules in each cell, and their
form and direction.
1 Cf. Lubbock, British Wild Flowers in Relation, to Insects, p. 93.
THE EVENING-PRIMROSE FAMILY. 201
IV. Using still older specimens, observe and describe
the structure of the fruit and its mode of dehiscence.
Physiological Adaptations.
If possible, visit both in the daytime and evening the
place where the plant is growing, and study its habits.
Ascertain when the flower opens, whether its color and
odor are attractive to any particular class of insects, and
whether the length of the calyx-tube or any other struc-
tural features indicate special adaptations. Endeavor to
ascertain by direct observation how pollination is effected.
Accounts of this, so far, are very meager, but suggest a
curious keeping in tow of two or more different sorts of
visitors, some of them coming by day and others by night.1
RELATIONSHIP.
I. Obtain specimens of the great willow-herb, or fire-
weed, Epilobium angustifolium, L., often very abundant on
newly cleared land that has been burnt over, and compare
the plant throughout with what you have seen of the
evening primrose. Note
1. Habits and external characters.
2. Structure of the flower, especially its plan and the
relation of the various whorls to each other.
3. Adaptations to insect visitors. Observe particularly
the position of the style in flowers of different
ages, and the time when the stigmas open. Is this
before or after the anthers have shed their pollen ?
NOTE. — This species furnishes an excellent example of proterandrous
dichogamy.'2
1 Cf . Lubbock, I.e. ; Miiller, Fertilization of Flowers, p. 264.
2 Cf. Gray, Structural Botany, p. 222.
202 STUDY OF COMMON PLANTS.
II. Compare the enchanter's-nightshade (Circcea Luteti-
ana, L.), also in flower in midsummer, with the evening
primrose.
1. Construct a diagram of the flower and observe how
it differs from that of the latter species.
2. Examine the flower under a lens and observe
a. The conspicuous nectary. (Abundant nectar may
also be found in some flowers.)
b. The surface of the ovary. Can you suggest more
than one use of the hooked bristles with which
it is covered ?
3. Observe, if practicable, the way in which pollination
takes place.1
III. A study of the cultivated Fuchsia may be made at
any time during several months of the year, and if more
convenient may be taken as the type instead of the even-
ing primrose.
IV. Compare your observations of the various members
of the family that you have obtained for study, and note
the morphological characters common to them all.
iCf. Muller, I.e., pp. 266,267.
THE PARSLEY FAMILY. 203
XXXII. THE PARSLEY FAMILY.
UMBELLIFER^E.
MATERIAL REQUIRED.
Harbinger-of-spring, Erigenia bulbosa, Nutt., in flower.
Later in the season, representatives of other genera, such as Osmor-
rhiza, Heracleura, Pastinaca, Thaspium, Daucus, Cicuta.
Fruits of fennel, Fceniculum vulgare, Gsertn., dill, Anethum graveolens, L.,
and coriander, Coriandrum satiuum, L. (to be procured at the
drug store).
HARBINGER-OF-SPRING. Erigenia bulbosa, Nutt.
Distribution and General Characters.
I. Record what you have noticed as to the habitat of
this species. Does it appear to be indigenous or intro-
duced ?
II. With perfect specimens at hand, study the general
features of the plant, noting particularly
1. The underground stem. Describe its form and struct-
ure. As a modified stem how is it to be classi-
fied?1
2. The habit of the plant as regards size, branching,
arid any other feature that appears to be charac-
teristic.
3. Leaves. Compare a number of proper foliage leaves
and describe one that you regard as typical. Notice
a. The expanded, sheathing petiole.
b. The extent to which the leaf is compound.
1 Cf, Gray, Lessons, p. 42 et seq.
204 STUDY OF COMMON PLANTS.
c. The uppermost leaves. Those subtending a group
of inflorescences constitute an involucre, those
subtending each separate inflorescence an in-
volucel. Do the leaves of involucre and involu-
cel differ in any important particular from the
lower leaves ?
4. The character of the inflorescence, and the grouping
of several inflorescences to form a compound umbel.
Flower.
I. Examine different flowers until you are satisfied as to
what parts are present. Note the essential facts of form,
number, position, etc.
II. Write a description, and indicate all the points in
which this differs from a " typical flower."
NOTE. — In this family the inflorescence and flowers are particularly
characteristic ; it is important, therefore, that their distinctive features
should be impressed on the mind before proceeding farther.
Fruit.
Fully mature specimens are indispensable in studying
the fruit of any member of this family ; accordingly,
instead of waiting for the Erigeriia to ripen, it will be con-
venient to take commercial specimens of fennel, coriander,
and dill, which will serve as good representatives of the
fruits of umbelliferous plants. Moreover, by studying
several kinds, instead of one, we shall gain a clearer im-
pression of their really characteristic features.
I. Observe carefully the external features of the three
fruits. That of the coriander is globular, fennel is more
nearly cylindrical, while dill is much flattened. In spite,
however, of these marked differences, there are a number
of characters common to all three. Note
THE PARSLEY FAMILY. 205
1. The ready splitting of the fruit into two halves,
mericarps.
2. The strongly marked longitudinal ribs on the outer
surface of each mericarp.
3. The stylopodium, a short conical body in which the
fruit is prolonged above.
4. The carpophore, or prolongation of the pedicel ; its
two thread-like branches each supporting one of
the mericarps. (Best seen in specimens of fennel
that have lain in water an hour or two.)1
II. Compare the three fruits more in detail, using a
good lens for the purpose. Observe
1. The number and position of the ribs. Begin with
fennel, in which it is at once seen that each meri-
carp has five strong ribs, two lateral, one dorsal,
arid two intermediate. How does the dill fruit
compare in this respect ?
The coriander fruit differs remarkably from either of
the preceding. If a mericarp is carefully studied,
it will be seen to have five primary ribs, corre-
sponding to those of fennel, but wavy in outline
and less prominent than four secondary ribs alter-
nating with them.
2. Remains of floral envelopes. If uninjured specimens
are examined, it will be seen that the calyx teeth of
the coriander are conspicuously present at the apex
of the fruit. Is this true of the dill and fennel ?
III. Prepare transverse sections of the mericarps of all
three species, and examine with the low power of a com-
pound microscope. In each case it will be necessary to
take at least two sections, one near the apex of the fruit,
and one near the middle or lower down.
206 STUDY OF COMMON PLANTS.
It will be seen that all three kinds have a relatively
thick pericarp and abundant, white endosperm, within which
lies the small embryo, near the apex of the fruit, and con-
sequently not seen in sections taken lower down. In the
pericarp are a number of vittae, or oil-tubes. The corian-
der has two of these in each mericarp lying next to its in-
ner, or ventral face. In fennel and dill, in addition to
these two, there are four more vittse alternating with the
ribs of the outer, or dorsal face.
Draw in outline, representing accurately the position of
ribs and vittse. Letters and guiding lines will conduce to
clearness.
IV. Write a complete description of the three fruits,
taking care to distinguish the characters common to all,
from those that are only of specific or generic value.
RELATIONSHIP.
Later in the season many other species of umbellifers
that will serve for comparative study are easily obtained.
Thaspium, or some other common genus, may be substi-
tuted for Erigenia if found more convenient. As the
study is continued it will be apparent that the external
characters to which attention has already been directed,
although variously modified, are constantly repeated in
nearly all the genera. The hollow stem, compound leaves
with inflated petioles, flowers in umbels, and the very
marked and distinctive features of flowers and fruit occur
over and over again, sometimes in connection with specific
characters by which a given plant is easily identified, some-
times with these characters so far wanting that identifica-
tion becomes extremely difficult. All in all, the family is
one of the best marked groups in the vegetable kingdom.
It includes about thirteen hundred species, distributed
THE PARSLEY FAMILY. 207
chiefly over the temperate regions of the globe. They are
remarkable for their widely different active properties, a
considerable number being edible, a large proportion pleas-
antly (or unpleasantly) aromatic, and a comparatively small
number poisonous. It is a curious fact that while very
largely dependent upon insects for fertilization, the flowers
of umbellifers attract, as a rule, a very common lot of visit-
ors such as " short-lipped flies, beetles, and other short-
lipped insects in immense variety." l Numbers, rather
than quality, has become the rule, and while the family
has held its own, and has even established a claim to be
considered one of the dominant natural orders, it is one
of the least attractive.
The best preparation for the further study of this rather
difficult family will be made by getting together a collec-
tion of ripe fruits, especially those occurring in commerce,
and becoming thoroughly familiar with their anatomical
structure.
Useful directions for collecting and other needed sug-
gestions are given by Coulter and Rose, in their Revision
of North American Umbelliferce?
SPECIAL STUDIES.
I. Morphology of the "tuber" of Erigenia bulbosa.
A critical botanist writes : " Is it really a stem ?
Who ever examined it? It appears to me to be
half hypocotyl, and the other half a root."
II. The terminal, colored flower of Daucus Carota.
1 Mtiller, Fertilization of Flowers, p. 287.
2 Separate monograph. Issued by the Herbarium of Wabash College,
December, 1888.
208 STUDY OF COMMON PLANTS.
XXXIII. THE MILKWEED FAMILY.
ASCLEPIADACE^E.
MATERIAL REQUIRED.
Flowers of Asclepias Cornuti, Decaisne. Alcoholic specimens will
serve if fresh ones are not to be had, but there is an advantage
in having a supply of both.
MILKWEED. Asclepias Cornuti, Decaisne.
Flowers.
Our study of the milkweed will be restricted to the
flowers, which present an extraordinary mechanism for
securing cross-fertilization through the agency of insects.
They are borne in a conspicuous umbel and attract numer-
ous visitors, particularly bees, wasps, and flies. Both the
odor and color are attractive, and there is an abundant
supply of nectar. The plant is absolutely dependent on
insects for fertilization.
Observe first the form and position of the floral envel-
opes. They are reflexed and covered on their lower
surface with short, woolly hairs. (This is contrary to
the general rule noticed by Kerner, Flowers and their Un-
bidden G-uests, that plants protected by milky juice have
smooth leaves, and are without any other appliances for
the protection of their flowers from crawling animals.)
The crown is the most conspicuous part of the flower.
It consists of five hollow bodies, cuculli, each of which has
an incurved horn projecting from its opening.
THE MILKWEED FAMILY. 209
There are five anthers placed close together, each ter-
minating in a membranous appendage that projects over
the thickened stigma disk.
The anthers are separated from each other laterally by
a deep, vertical slit, bordered on either side by a thin
triangular process, the anther wing. At the upper ex-
tremity of the slit is a minute, black body, corpusculum,
which, when removed by a needle, is found to be con-
nected by means of a delicate, curved band on either side,
with a flattened, yellow, and waxy pollen-mass, pollinium.
Longitudinal swellings on the outside of each anther indi-
cate the position of the pollinia before their removal.
Each of the slits already described is continuous within
with the stigmatic chamber, into which the pollen must be
introduced in order that fertilization may take place. It
is obvious that this cannot happen unless the pollinia are
removed from the anthers, and brought into the stigmatic
chambers by some external agency.
This is accomplished by bees and other insects that visit
the flowers for honey.1 Alighting on the umbel the insect
easily gets its foot caught in the lower part of one of the
slits, and in attempting to withdraw it, one of the claws
is guided into the notch in the lower end of the corpus-
culum. With a strong pull, the latter is removed from its
place, and the insect carries away with it the two pollinia,
which by the twisting of the delicate bands, retinacula,
that connect them with the corpusculum, are now brought
into such a position as to be readily introduced into
the slit leading to the stigmatic chamber of some other
flower. If this has been done, and the insect is strong
enough, it frees itself by a vigorous pull, breaking the
1 Ilildebrand and Mtiller have given a full account of the process, the
latter writer with illustrations. Fertilization of Flowers, p. 396 et seq.
210 STUDY OF COMMON PLANTS.
retinacula, and leaving the pollen masses in the stigmatic
chamber, while it proceeds to other flowers and continues
gathering honey.
Weaker insects are frequently unable to break the
retinacula. Flies may often be seen making unavailing
efforts to extricate themselves, and honey-bees are not
infrequently found that have been caught in the same.,
way, and have died after prolonged struggles to get free.
By means of the preceding description, accompanied by
careful observation at each step, the student will be in a
position to study the entire mechanism to advantage. He
should now go over the whole independently, until every
part of the flower is perfectly familiar. The study of
external structure should be followed by a comparison
of cross and longitudinal sections (best made from alco-
holic material), with sketches to show the parts and their
relations to each other.
Several hours will be required to do this properly.
Miiller's drawings may be consulted, but they are less
easily understood than the flower itself. Nothing can
possibly take the place of direct, personal, and long-con-
tinued study of the object under investigation. Further,
it is very desirable that the pupil should not only under-
stand the mechanism, but that he should also see it in
operation. A few days in summer spent in watching the
flowers of the milkweed, as the visitors come and go, will
give full opportunity for this.
RELATIONSHIP.
The Asclepiadacese constitute a large and very remark-
able family of plants, including about thirteen hundred
species, which are largely tropical, although many repre-
THE MILKWEED FAMILY. 211
sentatives occur in the temperate regions of both hemi-
spheres. They are chiefly interesting for the extraordinary
structural modifications of their flowers, which " rival the
orchids, if not in the variety of their forms, at least in
their complexity and their perfect adaptation to insect
visitors." A study of the steps by which this gradually
increasing complexity of structure has been attained is
of the highest interest. The student should carefully com-
pare the flowers of other genera of Asclepiadacese, and
such representatives of related families as Apocynum,
Vinca, and others.
SPECIAL STUDIES.
I. It is found that only a very small proportion of the
flowers in an umbel set fruits. Why is this ? and
are those flowers which do not set fruits of any
value to the plant ?
II. Minute structure of pollinia and retinacula.
III. Morphology of the cuculli.
IV. Development of the flower.
V. Protective appliances in this family.
212 STUDY OF COMMON PLANTS.
XXXIV. THE BORAGE FAMILY.
BORRAGINACEJE.
*
MATERIAL REQUIRED.
Common hound's-tongue, Cynoglossum officinale, L., in flower.
Similar specimens of any of the following genera : Echinospermurn,
Mertensia, Lithospermum, Symphytum, Heliotropium, Myosotis.
Cultivated species of some of these, as forget-me-not and helio-
trope, will serve a good purpose.
HOUND'S-TONGUE. Cynoglossum officinale, L.
Distribution and General Characters.
I. This species is described as an introduced weed. Do
its habits confirm this statement?
II. Examine the plant with reference to general feat-
ures. Note its coarse aspect, hairy surface, and dis-
agreeable odor.
Inflorescence.
The inflorescence is characteristic and should be criti-
cally studied, as it is of a form that appears in many rep-
resentatives of this family.
I. Notice first the order of development of the flowers.
The lowest have already formed their fruits ; higher up
are the open flowers, and at the apex are the unopened
flower buds.
II. The inflorescence is apparently a one-sided raceme.
Is it really so ? Notice the position of an open flower. Is
it terminal or lateral ?
THE BORAGE FAMILY. 213
III. Compare a number of inflorescences with reference
to the occurrence of bracts. Read Gray, Structural Botany,
pp. 153-155.
IV. If they can be obtained at the same time, compare
the inflorescence of other representatives of the Borragi-
naceae, such as puccoon and forget-me-not, with that of
fyound's-tongue. Do they agree essentially in the arrange-
ment of flowers ?
Flower.
I. Note first the numerical plan of the flower. Is the
number five maintained throughout ?
II. Observe the peculiar structure of the corolla, par-
ticularly the conspicuous folds or scales arching over the
essential organs. Is the flower perfectly regular ?
III. Taking a recently opened flower, make a longi-
tudinal section so as to show the precise relation of all the
parts. Draw.
Does the position of stigma and anthers, and the mode
of dehiscence of the latter, afford any indication as to the
way in which pollination is effected?
IV. Examine the ovary, noting the number of its divis-
ions, and their form and position.
Fruit.
I. Study the fruit in different stages of development,
taking flowers of different ages for the purpose. Observe
1. Its rapid increase in size.
2. The formation of peculiar barbed appendages, thickly
covering its surface.
II. Make longitudinal sections of young fruits so as to
show the form and position of the seed. Compare with
similar sections of older fruits.
214 STUDY OF COMMON PLANTS.
RELATIONSHIP.
Compare with this species as many others of the same
family as can be obtained. Note especially
I. Any general external characters in which they agree.
II. The inflorescence, which in this family presents very
interesting peculiarities.
III. The structure of 'the flowers, differing in details in
the different genera, but showing marked agreement in
plan.
IV. The characteristic fruit.
V. Structure and position of the seeds.
Write a brief summary of the features that you consider
characteristic of the family.
The Borraginaceee include about twelve hundred species,
widely distributed throughout the world. A number of
ornamental ones are common in cultivation. Some have
been employed in medicine, and the curious doctrine of
signatures is still called to mind by such names as lung-
wort and stone wort. The marked variety of external
appearance, in connection with great persistence of essen-
tial characters, as seen, for example, by comparison of the
exquisitely beautiful and fragrant heliotrope with the
coarse and rank hound's-tongue, is interesting as suggest-
ing how widely the different genera have diverged in
externals from earlier forms, while still retaining their
most deeply seated ancestral traits.
The student will do well to make a special study of the
inflorescence as it presents itself in various members of
the family, and in the same connection review the whole
subject of floral arrangement as presented by Gray, Les-
sons, Sec. VIII, or Structural Botany, Chap. V.
THE MINT FAMILY. 215
XXXV. THE MINT FAMILY. LABIATJE.
MATERIAL REQUIRED.
Specimens of ground-ivy, Nepeta Glechoma, Benth., in flower.
Similar specimens belonging to different genera of the Mint family,
as they can be obtained. See list below.
GROUND-IVY. Nepeta Glechoma, Benth.
Distribution.
As in previous studies, notice the habitat and consider
the evidence as to whether this is an introduced or indige-
nous species. Gray, in the Manual, says "naturalized
from Europe." What is meant by this?
General Characters.
I. Observe first the most obvious characters, among
them the following:
1. The habit of the plant, its stem creeping and taking
root at short intervals. Describe the root system.
2. The characteristic odor.
3. The shape of the stem and arrangement of the
leaves.
NOTE. —The aromatic properties, square stem, and opposite
leaves are characteristic not only of this species but of the whole
family to which it belongs.
4. The relation of leaves and stem. Note particularly
the ridges connecting the bases of each pair of
petioles, and their chevaux-de-frise of bristly
216 STUDY OF COMMON PLANTS.
hairs. Which way are the latter directed ? What
do you infer as to their use ?
5. Structural features of the leaves. Describe their
form and venation. With a good lens examine
closely the surface and margin. Are they smooth
or rough ?
II. Study the plant throughout with reference to its
various means of protection and their efficiency.
Inflorescence.
I. The flowers are in small axillary clusters. How
many in each group? In what order do they open? Is
this order constant? Classify the inflorescence, giving its
appropriate name.1
II. Are there any arrangements, in addition to those
already noticed, for the protection of the flower?
Flower.
I. Study critically the plan of the flower. How many
calyx-teeth are there ? How many lobes of the corolla ?
Remove the corolla with a pair of fine forceps, and lay
it open by making a longitudinal slit its entire length,
passing through the middle of the lower lip. Fasten it
on a flat piece of cork with needles, so as to fully expose
the stamens, and examine under a dissecting microscope.
One of the stamens has been suppressed. Which ? Notice
the insertion of the style, the peculiar form of the ovary,
and the nectary surrounding its base.
II. Taking flowers of different ages, observe the fruit
in its various stages of development. How many carpels
are there ? 2
1 Cf. Gray, Structural Botany, p. 151.
2 Cf. Gray, Structural Botany, p. 296 ; Luerssen, Botanik, p. 1014.
THE MINT FAMILY. 217
III. Construct a diagram of the flower. Consult Eichler,
Bluthendiagramme, for diagrams and theoretical discussion
of the morphology of the flower of the Labiatse.
IV. Examine the flower with reference to the way in
which fertilization is accomplished.
1. Notice the spots and lines on the lower lip of the
corolla. Examine different specimens and ascer-
tain whether they are constant in position. Are
they placed so as to serve as path-pointers ?
2. Using a needle or bristle, imitate the action of an
insect inserting its proboscis so as to extract the
nectar. Would it be likely to come in contact
with anthers or stigma, or both ?
3. If practicable, examine flowers, from different locali-
ties, and compare them as to size, position of the
anthers, and other features.1
4. Nepeta is reckoned by Miiller among the genera in
which, for at least some of the species, self-fertili-
zation has become impossible. Does this appear
to be the case with Nepeta Grlechoma ?
V. Compare, if they can be obtained, the highly modi-
fied flowers of Sal via, either those of the common sage, or
of species cultivated in conservatories.2
RELATIONSHIP.
Examine as many of the following species as practicable,
comparing them with ground-ivy, and noting all common
characters.
Catnip, Nepeta Cataria, L.
1 Cf. Botanical Gazette, I, p. 41, II, p. 118 ; Miiller, Fertilization of
Flowers, p. 484.
2 Cf. Sachs, Physiology of Plants, p. 794 ; Muller, I.e., p. 477 etseq.
218 STUDY OF COMMON PLANTS.
Wood-sage, Teucrium Canadense, L.
Richweed, Collinsonia Canadensis, L.
Spearmint, Mentha viridis, L.
Wild mint, Mentha Canadensis, L.
Wild bergamot, Monarda fistulosa, L.
Skullcap, Scutellaria galericulata, L.
Motherwort, Leonurus Cardiaca, L.
Dead-nettle, Lamium maculatum, L.
Cultivated species of Salvia.
Notwithstanding the fact that the Labiatse include some
twenty-six hundred species scattered over the entire globe,
they constitute a very natural group of plants ; that is, cer-
tain strongly marked characters are so uniformly present
that it would almost seem, as some botanical writers have
suggested, that all the species might be placed in one great
genus. Accordingly the distinction of genera in this
family becomes a difficult task. The modifications of the
floral structures in those species that have become most
dependent on the agency of insects for fertilization are
peculiarly interesting. The student may profitably devote
considerable time to the comparison of the various species
of Salvia, for example, with each other and with simpler
forms. Another interesting subject of investigation, and
one throwing additional light on the relationship of groups
that apparently have but little in common, is the develop-
mental history of the fruit, which is essentially the same
in this family as in the Boraginacese.
THE NIGHTSHADE FAMILY. 219
XXXVI. THE NIGHTSHADE FAMILY.
SOLANACE^E.
MATERIAL REQUIRED.
The cultivated potato in flower. The tomato may be substituted.
Specimens of matrimony-vine, Lycium vulgare, Dunal, in flower, and
similar specimens of ground-cherry, Physalis pubescens, L., bitter-
sweet, Solarium Dulcamara, L., or other easily procurable repre-
sentatives of the family.
POTATO. Solanum tuberosum,
Distribution and General Characters.
The common potato is indigenous to a portion of the
coast region of western South America. It has been
widely cultivated in the northern hemisphere for more
than three hundred years, apparently with little specific
change, there having been no inducement to artificial
selection of any other part than the tuber, which, however,
presents many, often striking, varieties.1
In examining the cultivated plant, study its habit, not-
ing the peculiarities of stem and leaves, and the character-
istic odor.
Inflorescence.
Examine a number of specimens. Do they agree in the
character of the inflorescence? Describe this and draw a
diagram showing the position of the flowers and their
order of development.
1 Cf. De Candolle, Origin of Cultivated Plants, p. 45 et seq.
220 STUDY OF COMMON PLANTS.
See if you can find a description of this kind of inflores-
cence in any of the books of reference. Does it correspond
with that of any other family that you have studied ?
Flower.
I. Study the parts of the flower in order and describe
them. Note particularly
1. The plan of the flower and whether it is strictly
regular or not.
2. The extent to which coalescence has taken place.1
3. Whether there is adnation of any parts.
4. Form of calyx and corolla.
5. Structure, position, and insertion of the stamens, and
their mode of dehiscence.
6. Number of carpels composing the ovary. State the
evidence on which you have determined this.
II. Construct a diagram.
III. Determine whether there are any arrangements
favoring cross-fertilization, and whether self-fertilization
is possible.2
Note the persistence, for at least several hundred years,
of structures that under present circumstances are of little,
if any, use to the plant, but which if it were neglected by
man and allowed to run wild, might again be needed.
RELATIONSHIP.
I. With the potato compare other species of the same
genus, as far as these are procurable, also representatives of
other genera as Lycopersicum, Physalis, Nicandra, Lycium,
1 Cf. Gray, Structural Botany, p. 179.
2 Cf. Miiller, Fertilization of Flowers, p. 425.
THE NIGHTSHADE FAMILY. 221
and Petunia. The last two are widely cultivated, and
their flowers may be had for weeks together. Attention
should be directed to
1. Such general external features as the plants possess
in common. Between certain species and genera
this likeness in general characters is very striking,
in other cases it is not apparent.
2. Active properties, manifested in part by odor and
taste.
3. Structure of flower and fruit.
4. Structure of seeds. The seeds of different plants of
this family exhibit great likeness of form and
structure, as may be seen by comparing longitu-
dinal sections of those of tomato, egg-plant,
stramonium, etc. It is very desirable that the
student should make an extended and critical
comparison of the seeds of as many different
species as possible. This should be assigned as
a special study, and time given for a thorough
piece of work.
II. Write a summary of the characters in which all the
species examined agree.
III. Compare the characters of the Solanaceee with those
of any other families that you remember as showing resem-
blances to them. If you have already studied any of the
Scrophulariacese point out the best characters by which
the two families are to be distinguished.
In the study of every family, comparisons of this kind
should be made as fast as the necessary data are in hand.
In most cases the relationships of families among them-
selves are by no means as satisfactorily made out as could
be desired, but that is no reason for not studying them.
222 STUDY OF COMMON PLANTS.
The Solanacese include over twelve hundred species,
chiefly tropical and sub-tropical, some representatives,
however, being widely cultivated in temperate regions.
Many of them possess strongly narcotic and poisonous
properties, as the names deadly nightshade, henbane, etc.,
indicate. A few are much employed in medicine. The
potato is the most useful, the tobacco plant the most
harmful member of the family. Morphologically this
group of plants is of interest in its affinities, more or less
distinctly marked, with several conspicuous families, the
Scrophulariacese and Convolvulacese among them. Physi-
ologically it offers comparatively little of special impor-
tance, although some species exhibit interesting adaptations
for insuring fertilization.
THE FIGWORT FAMILY. 223
XXXVII. THE FIGWORT FAMILY.
SCKOPHULAKIACE^.
MATERIAL REQUIRED.
Butter-and-eggs, Linaria vulgaris, Mill., in flower.
Common species of any of the genera named below.
BUTTER-AND-EGGS. Linaria vulgaris, Mill.
Distribution.
In what situations have you seen the plant growing?
Have you made any observations as to its natural range ?
Is there anything in its habits that affords evidence as to
whether it is indigenous or introduced ?
General Characters.
I. This species is perennial. How is the fact ascer-
tained ?
II. Describe the underground portion of the plant.
The stem and leaves.
III. Is there anything about it that secures protection
from grazing animals ?
Inflorescence.
Character and kind of inflorescence. Notice the posi-
tion of the individual flowers. Do they all face outward ?
Do the position of the flowers and the order of their
development present any advantages ?
224 STUDY OF COMMON PLANTS.
Flower.
I. Study the plan of the flower. What is the original
numerical plan as indicated by the floral envelopes? Is
this plan apparent in the androecium ? In the gynsecium ?
How many perfectly developed stamens are there? See
if you can find traces of another one. If so, how does it
compare with the rest? How many carpels compose the
pistil? On what evidence is this determined?
II. Construct a diagram of the flower. If you find a
trace of a fifth stamen, mark its place with an x.
III. Examine a transverse section of an ovary from
which the corolla has fallen, and notice the arrangement
of the ovules, and the position and form of the placentae.
In a still older ovary observe the form and structure of
a young seed.
IV. When the capsules are ripe study their structure
and mode of dehiscence.
V. Study carefully the adaptations for securing fertili-
zation by the agency of insects. Begin with the corolla
and note
1. Its bilabiate form.
2. The conspicuous palate and its color as compared
with the rest of the corolla.
3. The spur. Where is the nectar? Is it easily acces-
sible to all sorts of visitors? Imitate the action
of a bee in gathering honey. Depress the lower
lip by pushing down the palate with a needle.
Are there any path-pointers ? Notice the position
of anthers and stigma.
If possible, watch a bee visiting a plant, and observe
the mutual relations of insect and flower.
THE FIGWORT FAMILY. 225
This plant has been widely introduced into the United
States, and, notwithstanding its botanical interest, is a
pernicious weed, difficult to eradicate. Aside from repro-
duction by seed, it persistently maintains itself by means
of its rhizomes, each of which sends up several or many
aerial shoots. The unpleasant odor and taste of the
plant render it distasteful to grazing animals, so that
it is efficiently protected by its own disagreeable prop-
erties.
The adaptations for securing cross-fertilization by the
agency of insects are striking, and, for the most part,
easily understood. The flowers are rendered conspicuous
by massing in a crowded raceme, and face outward, so a3
to be immediately accessible to flying insects, while the
orange-colored palate, with its smooth median groove on
the inner side, directs visitors at once to the nectar col-
lected in the spur. The anthers and stigma are so dis-
posed as to come in contact with the head and back of
the insect (commonly a bee), as it depresses the palate
and inserts its long proboscis into the spur. While thus
accessible to large insects with a long proboscis, the nectar
is protected from unbidden guests by the palate, that com-
pletely closes the throat of the flower, and springs back
to its place when the force by which it is depressed ceases
to act. It is further protected by its position, being out
of the reach of insects with a short proboscis that may
in some way have effected an entrance into the flower.
The mechanical arrangements for the dissemination of
the seeds are also of interest. The hygroscopic action of
the capsules is readily shown by placing them when dry
in water. In less than a minute the teeth at the apex
begin to bend inwards, and in a short time the capsule is
tightly closed, opening again when it has been thoroughly
226 STUDY OF COMMON PLANTS.
dried. In this way the seeds are scattered when the
weather is most favorable for their being conveyed to
some distance. On the whole, the plant with its simple
but effective means of protection, persistent subterranean
stems, admirable adaptations for cross-fertilization, and
numerous seeds with special arrangements for dissemi-
nation, is exceedingly well adapted to survive in the
struggle for existence.
RELATIONSHIP.
I. Compare several of the following plants with the
species just studied, directing attention particularly,
though not exclusively, to the flowers. (Some of these
that bloom earlier than the Linaria, as the wood-betony,
may be studied before the latter if more convenient.)
Wood-betony, Pedicularis Canadensis, L.
Painted-cup, Castilleia coccinea, Spreng.
Beard-tongue, Pentstemon pubescens, Solander.
Turtle-head, Chelone glabra, L.
Monkey-flower, Mimulus ring ens, L.
Various species of Veronica.
Some cultivated species also may be used such as
" Kenil worth ivy," Linaria Cymbalaria, Mill.
Snapdragon, Antirrhinum majus, L.
Foxglove, Digitalis purpurea, L.
How do these compare as regards
1. Plan of the flower?
2. Shape of corolla ?
3. Number of stamens ?
4. Structure of ovary ?
5. Number and position of seeds ?
THE FIGWORT FAMILY. 227
II. State concisely, and in general terms, what charac-
ters you have found to be common to all the species
studied.
There is evidence that the Scrophulariacese are an old
family of plants, and one that may fairly be reckoned to
have gained a place among the dominant groups. There
are nearly two thousand species distributed over the entire
globe. While well marked as regards family characters,
the different genera and species exhibit very wide diver-
gence of structure, often associated with peculiarities of
color that stand in evident relation to the insects on which
they have come to depend. A considerable number have
entirely lost the capacity for self-fertilization, and the
mechanical arrangements are in some cases so complicated
as to be difficult of explanation. The gradation of forms
from comparatively simple ones to others that show
remarkable adaptations to highly specialized insects, offers
a peculiarly interesting study of developmental history.1
SPECIAL STUDIES.
I. Morphology of the flower of the Scrophulariacese.
II. Peloria in this family and its significance.
III. Comparison of mechanisms by which fertilization is
effected in different genera of Scrophulariacese.
IV. Exclusion of unbidden guests as accomplished in
Pentstemon and other genera.
V. The genus Veronica. A comparison of different
species of the genus, and of the genus itself with
other representatives of the family.
1 Cf . Mtiller, Fertilization of Flowers, pp. 429-465.
228 STUDY OF COMMON PLANTS.
XXXVIII. THE HONEYSUCKLE FAMILY.
CAPRIFOLIACEJE.
MATERIAL REQUIRED.
Common elder, Sambucus Canadensis, L., in flower. Other specimens
of the same species, with the fruit partially developed. Species
of Viburnum, coming earlier in the season, may be substituted.
Any of the indigenous species of Lonicera, Diervilla, Symphoricarpus,
Linnsea, and Triosteum that are procurable.
COMMON ELDER. Sambucus Canadensis, L.
Distribution.
In what situations have you observed the plant growing ?
Is it indigenous ?
General Characters.
I. Record what you have noticed as to its mode of
growth. Is its habit that of a shrub or of a tree ?
II. Mode of branching. Differences observed in differ-
ent specimens.
III. Do the stems exhibit any peculiarities of form,
structure, or surface markings? If so, describe in detail.
NOTE. — The lenticels are generally a conspicuous feature. For an ac-
count of these, see Strasburger and Hillhou.se, Practical Botany, pp. 153,
154.
IV. Describe the leaves. Note variations.
THE HONEYSUCKLE FAMILY. 229
Inflorescence.
I. Observe the number and position of the main
branches. Compare specimens until the normal arrange-
ment is clearly understood.
II. Ascertain the order of development of the flowers.
Take a small division of the inflorescence, to avoid confu-
sion, and represent it on paper diagrarnmatically.1
III. Classify the inflorescence.2 Does such an arrange-
ment of flowers present any physiological advantages ?
Flower and Fruit.
I. What is the numerical plan of the flower ? Is this
constant in all the specimens ? Is it exhibited in all the
whorls ?
II. Note the relation of the different whorls to each
other. Is the ovary superior or inferior? Where are the
stamens attached?
III. Does the relative position of anthers and stigma
favor cross- or self-fertilization, or both ?
IV. Make transverse sections of a number of immature
fruits. Are they all alike ? Draw a section that you con-
sider typical. Compare the ripe fruits, if they are to be
had, and note the changes that have taken place. Describe
and classify the fruit.
RELATIONSHIP.
The relationship of the common elder must necessarily
be made a subject of special study rather than a piece of
class work, since the indigenous species of Caprifoliacese
1 Cf. Bessey, Botany, pp. 138, 139.
2 Cf. Gray, Structural Botany, pp. 151, 152.
230 STUDY OF COMMON PLANTS.
flower, for the most part, at widely different times, and
some of the genera exhibit among themselves such marked
structural differences as to obscure, except to a trained
eye, the common family characters. The contrast between
the simple, open flowers of the elder and the extremely
elongated corolla of species of Lonicera that have become
adapted to the visits of night-flying moths, is a striking
example. The student who wishes to familiarize himself
with this family, which presents many interesting features,
will find in the course of spring and summer enough
indigenous species of the genera named above to enable
him to make a fairly extended comparative study. The
clue to the wide divergence of form, and the remarkable
series of colors exhibited by flowers of the different genera,
is apparently found in progressive adaptation to different
insect visitors.1
Another remarkable feature is the great difference of
habit exhibited by different members of the family, as
seen, for example, in a comparison of the slender, trailing
Linnaea with the coarse, upright Triosteum, or the climb-
ing species of Lonicera with the shrubs or trees of the
genera Sambucus and Viburnum. Even within the limits
of a single genus, as in the case of Lonicera and Viburnum.,
wide differences of structure and habit present themselves,
affording an opportunity to observe adaptations that ap-
pear to have been acquired within comparatively recent
times.
1 Cf . Miiller, Fertilization of Flowers, p. 299.
THE GOURD FAMILY. 231
XXXIX. THE GOURD FAMILY.
CUCURBITACE^E.
MATERIAL REQUIRED.
The common cucumber, Cucumis sativus, L., in flower.1
Similar specimens of squash, melon, wild cucumber or gourd.
Seeds of pumpkin, melon, arid various other cucurbits.
CUCUMBER. Cucumis sativus, L.
Distribution.
The cucumber has been widely cultivated from an early
date, and presents a remarkable case of the persistence of
specific characters for an indefinite period. According to
De Candolle, it has been cultivated in India no less than
three thousand years, yet its wild form found at the foot
of the Himalayas has stems, leaves, and flowers that are
" exactly those of Cucumis sativus" 2
General Characters.
I. Note first the habit of the plant as regards position
and direction of growth. Is it capable of supporting itself
in an erect position ? How do young specimens compare
with older ones in this respect ?
II. Observe the leaf arrangement.
III. Is the plant protected in any way ? Examine the
1 Well-formed plants, with flowers and young fruits, are easily ob-
tained by sowing the seeds in flower-pots a few weeks before the speci-
mens are wanted.
2 Origin of Cultivated Plants, pp. 264-266.
232 STUDY OF COMMON PLANTS.
surface of stems, leaves, flowers, and fruit, first with the
naked eye, and then with a good lens. Imagine a soft-
bodied animal attempting to crawl up to the leaves or
flowers. Which parts are best protected ?
Tendrils.
I. Study carefully the tendrils, noting particularly their
origin, form, and mode of grasping a support. How do
they compare in their subsequent behavior with those of
bryony, described by Sachs ? 1
II. Rub one of the young tendrils and watch it for a
few minutes. Is there any movement? Does it make
any difference whether the concave or convex side is
rubbed ? 2
III. Watch a vigorous specimen long enough to observe
the spontaneous movements of its tendrils.
Inflorescence and Flowers.
I. How many flowers compose the inflorescence? Are
they all alike ? Compare those in the axils of the lower
leaves with the ones produced higher up. Is this species
monoecious or dioecious?3
II. Examine carefully the stamens, noting the form
and structure of the anthers and their peculiar mode of
cohesion.4
III. How many stigmas are there ? Examine their sur-
face with a lens.
IV. Are there any nectaries ? How far do the flowers
of the cucumber agree with those of Bryonia dioica, as
1 Physiology of Plants, pp. 663, 664.
2 Cf. Darwin, Climbing Plants, p. 127 et seq.
3 Cf. Gray, Lessons, p. 85.
* Cf. Goebel, Outlines of Classification and Special Morphology, p. 357.
THE GOURD FAMILY. 233
described by Mallei'?1 Does their structure indicate self-
or cross-fertilization ?
V. Examine the ovary of one of the oldest flowers.
Is there any external indication of the number of carpels?
Make a transverse section and notice the number of
cells, the position of the placentae, and the form and direc-
tion of the ovules. Draw the section in outline. Repre-
sent by dotted lines the commissural lines of union of the
carpellary leaves.2
RELATIONSHIP.
Seeds of squash, melon, and many other plants belonging
to this family, are easily procurable, and afford the means
of extended and instructive comparative study. Seedlings,
which may be had in the course of a few days, exhibit
with remarkable uniformity in the different genera the
characteristic contrivance by which the seed-coats are
ruptured and the cotyledons released.3 Tendrils of vari-
ous species, that may be studied anywhere a little later
in the season, are of the greatest interest, morphologically
as well as physiologically, and in their turn contribute to
the sum of characteristic features by which this famil}r is
marked. If all these are carefully studied, as well as the
flowers and fruits, and due weight is given to every well-
marked trait, it will be found that the " family characters"
include more than the structural details usually given.
The behavior of the seedlings in breaking through the
ground, the highly developed tendrils and their mode of
action, and even the active properties of some of the
1 Fertilization of Flowers, pp. 268, 269.
2 Cf. Eichlor, Bliithendiagramme, p. 306.
3 Darwin, Power of Movement in Plants, p. 102.
234 STUDY OF COMMON PLANTS.
species are as truly characteristic as various other features
upon which more emphasis is usually laid.
The student is recommended to make a special study of
seeds and seedlings of the Cucurbitacese, and to proceed
from these, as material and opportunity permit, to the
characters observable in later stages of growth.
THE COMPOSITE FAMILY. 235
XL. THE COMPOSITE FAMILY. COMPOSITE.
MATERIAL REQUIRED.
Specimens of the common dandelion in flower, others with the fruits
in different stages of development.
Similar specimens of robin's-plantain, Erigeron bellidifolius, Muhl. (or
other species of Erigeron), plantain-leaved everlasting, Antennaria
plantaginifolia. Hook., golden ragwort, Senecio aureus, L.
Later in the season, yarrow, A chillea Millefoiium, L., mayweed, Anthe-
mis Cotula, DC., oxeye daisy, Chrysanthemum Leucanthemum, L.,
wild lettuce, Lactuca Canadensis, L,
In the fall, asters, goldenrods, and various species of Bidens, Prenan
thes, and other late flowering composites.
THE DANDELION. Taraxacum officinale, Weber.
Distribution.
Where were the specimens gathered? Does the plant
manifest any choice of locality or surroundings? Is it an
indigenous or introduced species ?
General Characters.
With a perfect specimen in hand, note the several parts
of the plant and write a brief description, including an
account of the form, structure, and apparent duration of
the root, the stem (so short that the plant is said to be
acaulescent), the position and form of the leaves, the
character of the inflorescence and its support, and any
conspicuous peculiarities, such as taste, color of the latex,
etc.
236 STUDY OF COMMON PLANTS.
Inflorescence.
I. Observe first the cylindrical hollow stalk (scape)
by which the head is supported. How do those of older
specimens compare in length with those of younger ones?
Can you suggest any advantage in this ? 1
II. The head is subtended by an involucre of green,
leaf-like bracts.
1. Is there more than one row of bracts? How do the
outer differ from the inner ones?
2. Compare the position of the involucre in the early
morning with that assumed later in the day, and
finally in the evening; in clear and rainy weather.
Do these observations suggest anything as to the
function of the involucre?
III. Taking a well-developed head, not so old but that
a few of the flowers of the center are still unopened, make
a longitudinal section.
1. Observe the disk-like, expanded end of the stalk on
which the flowers are borne, the receptacle. Is it
concave or convex ? How does it compare in this
respect with the oldest receptacles from which the
seeds have fallen? Suggest advantages.
2. Note the order of development of the flowers. Cen-
tripetal or centrifugal ?
Flowers.
These should be studied in position and also separately,
removing for this purpose several flowers with a pair of
fine forceps.
I. Examine a fully developed flower throughout. With
a good lens observe
1 In this and some other cases it will be necessary to supplement the
laboratory exercises by out-of-door observations.
THE COMPOSITE FAMILY. 237
1. The seed-like ovary, its form and surface, and the
prolongation of its upper end into a short beak,
which afterwards becomes greatly elongated.
2. The calyx, with its limb of numerous fine bristles,
pappus.
3. The yellow, ligulate corolla.
4. The stamens inserted on the corolla, epipetalous,
with their anthers united in a hollow cylinder
around the style, syngenesious, the latter soon pro-
jecting beyond them and divided above into two
slender, recurved, and finally coiled branches.
(Specimens should be gathered in the morning
and also in the afternoon.)
II. Compare successively older, outer flowers with the
younger ones, approaching finally the unopened flowers at
the center. Note the different stages of development of
the flower, particularly of the stamens and pistil. Observe
1. The way the pollen is pushed out by the style.
2. The short, stiff hairs on the outer surface of the
latter.
3. The papillae on the inner, stigmatic surface of each
of its branches. (These latter require higher
magnification in order to be seen clearly.)
III. Imitate the action of a bee or other insect by
repeatedly brushing a large number of flowers. Examine
the stigma before and after the operation. Is there any-
thing to favor cross-fertilization ?
Fruit.
Study next a head in fruit. Compare the hard, seed-
like achenium with the immature ovary already examined
and note differences . What arrangements are there for
the dissemination of the fruits ?
238 STUDY OF COMMON PLANTS.
Review your observations and record them precisely.
I. In writing an account of the flower treat it first from
the morphological standpoint, including a discussion of
1. Original plan of the flower, as indicated by notches
at the end of the corolla and number of stamens.
2. Relation of calyx and ovary.
3. Other evidences of modification.
II. Enumerate the various physiological adaptations
such as
1. Protective arrangements.
2. Adaptations for securing fertilization.1
3. Means of dissemination of seeds.
ROBIN'S-PLANTAIN. Erigeron bellidifolius, Mubl.
Distribution.
Where have you noticed the plant growing most abun-
dantly ? Does it appear to be indigenous or introduced?
General Characters.
Describe the root, stem, and leaves. Note means of pro-
tection, if such exist.2 It is said to produce " offsets."
Verify the statement.
•
Inflorescence and Flowers.
I. Compare the heads with those of the dandelion.
What are the most striking differences ?
II. Make a longitudinal section and examine in their
natural position, and also separately, the purple ray flowers,
and the small, yellow disk flowers. The ray flowers are
1 Cf. Lubbock, British Wild Flowers in Relation to Insects, p. Ill
et seq. ; Mtiller, Fertilization of Floivers, pp. 316-318, 350.
2 Cf. Kerner, Flowers and their Unbidden Guests, Chap. IV.
THE COMPOSITE FAMILY. 239
ligulate, like those of the dandelion ; the disk flowers are
tubular.
Do both ray and disk flowers have stamens and pistil?
Are both fertile ?
III. In older heads examine the achenia, and observe
their form and surface.
IV. How far do the arrangements for securing fertiliza-
tion correspond with those observed in the dandelion ?
V. Compare the flowers of the two plants as regards
modification from an assumed original form.
PLANTAIN-LEAVED EVERLASTING. Antennaria
plantaginifolia, Hook.
As in preceding^ cases, note where this plant occurs, and
record any peculiarities in its mode of growth. Notice
particularly its habit of spreading by runners.
It will be observed that there are two sorts of flowering
heads, on different individuals, one, pistillate, more elon-
gated and lighter colored than the other, staminate, ones.
Study critically the flowers of the two different kinds
of heads. Note all the points in which they are unlike,
including differences of pappus and corolla, fertility,
color, size, etc.
Compare the flowers of this species with those of the
dandelion and robin's -plan tain, noting in each case points
of similarity and difference.
RELATIONSHIP.
A comparative study should be made of as many other
genera of Composite as practicable. There are so many
species, ranging in their time of flowering from spring to
240 STUDY OF COMMON PLANTS.
late autumn, that there is no difficulty in obtaining abun-
dant material. With patience and close attention to
details of structure, there is no reason why the student
should not become thoroughly familiar with the charac-
ters of this important and extremely interesting family,
although the determination of the limits of genera and
species is often a matter of great difficulty, owing to the
number of intermediate forms and the tendency to vari-
ability exhibited by many species.
When as many species have been studied as the time
will permit, write a careful summary of the morphological
characters in which they all agree. This should be accom-
panied by a resume of their physiological peculiarities,
especially the arrangements for securing fertilization and
the dispersal of seeds.
The Composite constitute the largest family of flower-
ing plants, including over one thousand different genera.
Admirably fitted to survive in the struggle for existence,
they have become distributed throughout the world, and
retain tenaciously their dominant position. Some of the
genera are represented by so many species, and are so
abundant as to form in their season a characteristic feature
of the landscape, as is the case, for example, with the
asters and goldenrods in eastern North America. " The
numerical preponderance, . . . and extreme abundance of
many of the species, are due to the concurrence of several
characters, most of which, singly, or in some degree com-
bined, we have become acquainted with in other families,
but never in such happy combinations as in the Com-
positse." See Miiller's discussion of these points in the
Fertilization of Flowers, p. 316 et seq.
REVIEW AND SUMMARY. 241
REVIEW AND SUMMARY.i
After such exercises as those outlined in the preceding
pages, even if only a small number of families have been
studied, the student can hardly fail to have Degrees of
grasped the conception of degrees of relation- relationship,
ship, a conception that lies at the ver}^ foundation of bio-*
logical science.2 If we now extend our study farther, and
compare families with each other, as we have been com-
paring their genera, we shall find that the principle is
general, and that families, as well as genera and species,
show relationships among themselves, falling naturally into
larger groups to which the term " order " is now commonly
applied.3 In some cases these groups are distinctly marked,
and the close relationship of the families composing them
is unmistakable, while in others the affinities of a family
are obscure. In an inquiry of this kind there are neces-
sarily inherent difficulties, and it must be said frankly, that,
in the present state of botanical science, it is impossible to
construct a system that will fully and truthfully represent
the relationship of families of plants to each other. Never-
theless it is desirable before proceeding farther to notice
1 It is assumed that the order recommended on page 96 has been fol-
lowed, or at least that the student has acquired a reasonably familiar
acquaintance with the prominent families of flowering plants.
2 " For myself, there comes from the eighth year memory of an
awakening to the conscious grasp and knowledge of genus and species.
I see it yet ... in my lap the shredded petals of almond, plum, and
the yellow rose of Persia, and in myself sense of a new concept and tool
for classifying and accumulating knowledge through all life." — TALCOTT
WILLIAMS, in the Century, January, 1893.
3 "Natural order" is still employed by many writers as equivalent to
family, but the usage indicated above is becoming prevalent.
242 STUDY OF COMMON PLANTS^
some of the cases in which such affinities are plainly marked.
A few of these will serve as examples of many others.
The Cruciferse, as we have seen, are so plainly defined
by their cruciform, tetradynamous flowers, pungent proper-
Groups of ties, and characteristic fruits and seeds, that we
families, naturally think of them as sharply marked off
from all other families of plants. A number of smaller
families, however," are manifestly related to them. In one
of these, the Capparidacese or caper family, the flowers are
cruciform, the plants often pungent, the pods nearly the
same as those of the Cruciferae, and the seeds similar; but
there are certain differences of the embryo and stamens
that require a separation of the two families, which other-
wise are nearly identical in their characters. In like man-
ner the members of the Rosacese, another prominent and
well-marked family, show such plain affinities with the
Saxifragacese that the differences by which the two families
are distinguished from each other seem trivial in compari-
son with their strong likeness. Again, while the Labiata?,
with their square stems, opposite leaves, bilabiate flowers,
and aromatic properties, form a most characteristic group
of plants, their relationship with the Verbenacese, which
exhibit a number of characters in common with them, is
manifest at a glance. In the same way the Asclepiadacese
and Apocynacese show a remarkable likeness, and this is
still more strikingly true of the Liliaceae and a number of
families that form with them another marked group, or
order.
These examples are sufficient to illustrate the natural
grouping of families into orders. Thus, the Labiatse with
Orders and n^De °ther families constitute the Labiatiflorse,
higher groups, the Liliacese with fifteen other families the
Liliiflorse, and so on. At present botanists recognize some
REVIEW AND SUMMARY. 243
thirty orders of dicotyledons, including about one hundred
and sixty-three families, and seven orders of monocotyle-
dons with about forty families, while the gymnosperms
include three orders with thirteen families.1 The orders
themselves are associated in higher groups, which in their
turn make up the great classes just named.2
Another fact of prime importance, that cannot well have
escaped the student's attention, is the gradually increasing
complexity of structure, particularly of the floral Progressive
organs, met with as we proceed from more prim- ^fl^f10
itive to more advanced families. Comparing a organs,
lily, for example, with an orchid, or a buttercup with a
dandelion, it is plain that the flowers of the higher families
have undergone very remarkable changes of form and
structure, although the fundamental plan may still be
recognized. These changes of structure represent, as a
rule, .progressive adaptation to cross-fertilization through
the agency of insects. It appears, too, from all we can
learn of them by comparative study, that these progressive
modifications have taken place step by step with corres-
ponding modifications of structure and habit on the part
of their visitors. The history of such a flower as that of
the sweet-pea or violet, of the milkweed or daisy, must, if
this view is correct, reach far back into the past, so far that
the imagination fails to reproduce the long series of changes
that have taken place in the succession of intervening
generations. A glimpse of this history, helpful and satis-
1 Cf. Luerssen, Botanik, Bd. 2, pp. vii-x.
2 These groups of a higher order are less satisfactorily defined. For an
attempt at their systematic presentation, see Goebel, Outlines of Classifi-
cation and Special Morphology, pp. xi, xii. The student will do well to
remember that all such attempts to represent the affinities of families and
higher groups involve more or less uncertainty, and that all classifications
are of necessity provisional.
244 STUDY OF 'COMMON PLANTS.
factory as far as it goes, is given by Miiller in his general
retrospect at the close of the Fertilization of Floivers, as
follows : " Insects must operate by selection in the same
way as do unscientific cultivators among men, who preserve
the most pleasing or most useful specimens, and reject or
neglect the others. In both cases, selection in course of
time brings those variations to perfection which corre-
spond to the taste or to the needs of the selective agent.
Different groups of insects, according to their sense of
taste or color, the length of their tongues, their way of
movement and their dexterity, have produced various
odors, colors, and forms of flowers; and insects and flowers
have progressed together towards perfection."
Turning to the lower or so-called cryptogamic plants, it
appears that precisely the same principles hold good. Ferns
and mosses, quite as plainly as plants higher in
A progressive the scale, exhibit degrees of relationship. Here,
series, ag eisewhere, closely related species fall natu-
rally into genera, closely related genera into families, and
these into orders and higher groups. Furthermore, a
review of these higher groups shows that the vegetable
kingdom as it exists to-day presents a progressive series,
rising from such simple plants as Spirogyra, and even more
primitive forms of the green algse, through the liverworts
and mosses to the vascular cryptogams, and from these by
an almost insensible step through Selaginella and its allies
up to the gymiiosperms and flowering plants. It is be-
lieved by those who have the most extended and critical
knowledge of plant life that this series corresponds closely
with the order of development of the vegetable kingdom,
and, as a matter of fact, it is found that the geological
record strikingly confirms this view. In earlier geological
times, beginning with the Silurian Age, marine algse and
REVIEW AND SUMMARY. 245
other cellular cryptogams were the dominant forms of
plant life. Vascular cryptogams appeared in the Devo-
nian ; after them came the gymnosperms ; then the mono-
cotyledons ; and finally the different classes of dicotyledons
attained their present supremacy.1
The life history of the flowering plants and higher cryp-
togams still further confirms the same view, passing as
they do through successive stages of development that
repeat in miniature the history of past ages of plant life.
The fern prothallium in its earlier stages of growth is so
nearly a filamentous green alga as to be distinguished
from one by its origin rather than by its structure; a little
later it becomes a flat expansion of cells, so like a liver-
wort as to deceive the inexperienced eye ; and these and
other phases of their developmental history may still be
recognized, not only in the gymnosperms, but in the higher
flowering plants.
From facts like these, it seems impossible to draw any
other conclusion than that there has been from the earliest
appearance of plant life on the elobe a slowly
, L , , . , 1-1 Conclusions,
progressive development irom simpler to higher
forms, and that the record of this is still preserved to us
in the natural groups that form the present vegetation of
the earth.
We are to think, then, of the plants we have studied
and those we have yet to study, as in reality all members of
one vast and ancient family, some closely, others remotely
related, some still retaining the simple forms and habits of
earlier days, and others, through a long course of selection,
exquisitely adapted to animal structures no less highly
modified and adapted to them. In this great family, we
1 Lester F. Ward, Am. Nat., August, 1885.
246 STUDY OF COMMON PLANTS.
have learned to distinguish species, genera, families, orders,
and classes ; but these are simply expressions of so many
different degrees of relationship that pass insensibly into
each other, and call for the exercise of clear judgment,
profound knowledge, and critical attention to details on
the part of those who attempt to recognize and define
them.1
This is a conception widely different from that which
supposes " that species, and even genera, are like coin from
the mint, or bank-notes from the printing press, each with
its fixed marks and signature, which he that runs may
read, or the practiced eye infallibly determine," but "there
is grandeur in this view of life, with its several powers,
having been originally breathed by the Creator into a few
forms or into one ; and that, whilst this planet has gone
cycling on according to the fixed law of gravity, from so
simple a beginning, endless forms most beautiful and most
wonderful, have been and are being evolved."2
^ After some months of such training as is outlined in the preceding
exercises, the student should be prepared to take up with profit a study
of the flora of the region in which he lives. In this way, with an indefi-
nite amount of painstaking, independent, and long-continued work, he
will gradually become more familiar with the systematic grouping of
plants and accumulate for himself the evidence that more and more con-
firms the conclusion formulated above.
2 Darwin, Origin of Species, p. 429.
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By WM. N. RICE, Prof, of Geology, Wesleyan Univ., Conn. Paper. 46 pp. Price, 86 cts.
Elementary Course in Practical Zoology.
By B. P. COLTON, A. M., Professor of Science, Illinois Normal University. Cloth.
196 pages. Price by mail, 85 cts.; Introduction price, 80 cts.
First Book of Geology.
By N. S. SHALER, Professor of Palaeontology, Harvard University. 272 pages, with 130
figures in the text. Price by mail, i.io ; Introduction price, i.oo.
The Teaching of Geology.
By N. S. SHALER, author of First Book in Geology. Paper. 74 pages. Price, 25 cents.
Astronomical Lantern and How to Find the Stars.
By REV. JAMES FREEMAN CLARKE. Intended to familiarize students with the constel-
lations, by comparing them with fac-simi!es on the lantern face. Price of the Lantern, ii?
improved form, with seventeen slides and acopy of " How TO FIND THE STARS." $4.50.
" How TO FIND THE STARS," separately. Paper. 47 pages. Price 15 cts.
Studies in Nature and Language Lessons,
±}y PROF. T. BERRY SMITH, of Central College, Fayette, MQ A combination of simple
natural-history object-lessons, with elementary work in language. Boards. 121 pages Price
so cts. Parts I. and II. 48 pages. Price, 20 cts
D C. HEATH & CO., Publishers,
BOSTON, NEW YORK AND CHICAGO.
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