Elements of botany

Front matter

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Cornell Mniversity Library

Preface

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TuE present text-book is, for the most part, an expansion of the manuscript notes which have for some years formed the basis of the botany-teaching in the Boston English High School. These notes were drawn up by Mr. Samuel F. Tower and the author, for the purpose of establishing what seemed to them a suitable half-year course in botany for pupils of the entering class in that school.

It will be found that this book differs from most American text-books designed for use in secondary schools, in endeavoring to combine in one volume the simplest possible directions for laboratory work with an outline of vegetable anatomy and physiology, and a brief statement of the principles of botanical classification. An account of the functions of the tissues or organs described usually follows as closely as may be the account of the parts in question. The attempt is made to discuss plants dynamically rather than statically, to view them as contestants in the struggle for existence, and to consider some of the conditions of success and failure in the vegetable world. While the determination of species by means of an artifical key is illustrated, preparation for this process is by no means the main object or even a principal end which the author has had in view. The tendency of botany-teaching seems to be more and more away from the old ideal of enabling one’s pupils to run down a species as expeditiously as possible, and teaching them how to preserve a properly ticketed memento of the chase.

iv PREFACE.

The illustrations drawn from nature, or redrawn expressly for this book, are mostly by Orville P. Williams or Francis M. West, recent graduates of the English High School. ‘The woodcut of Monotropa is from a photograph kindly loaned for the purpose by its maker, Rev. R. 8. Morison. Large numbers of illustrations have been reproduced from the following works, which are named in about the order of the extent to which they have been drawn upon:

Le Maout and Decaisne’s Traité Général de Botanique.

Thomé’s Structural and Physiological Botany.

Tschirch’s Angewandte Pflanzenanatomie.

Strasburger, Noll, Schenk, and Schimper’s Lehrbuch der Botanik. Kerner’s Pflanzenleben.

Figuier’s Vegetable World.

Behrens’s Text-book of General Botany.

Sachs’s Text-book of Botany.

The author is to a less extent indebted for cuts to the works of Brown, Carpenter, Darwin, Lindley, Lubbock, Potonie, Strasburger, Hartig, Host, Kny, Detmer, Martius, Baillon, and others.

For most of the subject-matter of this book —though not for the order and mode of treatment — the writer is of course indebted to a multitude of sources, only a very few of which are indicated in the subjoined bibliography. Personal assistance has been freely rendered him by Prof. George L. Goodale, Dr. Benjamin L. Robinson, Curator of the Gray Herbarium, and Mr. A. B. Seymour of the Cryptogamic Herbarium of Harvard University. Prof. George J. Pierce of Indiana, State University has given valuable aid in regard to some physiological questions. Prof. William F. Ganong of Smith College has done so much for the book that if it should prove useful its value will be largely due-to his suggestive criticisms. Thanks are due for the careful proof-reading of.

PREFACE. v

Prof. George G. Groff of Bucknell University, Lewisburg, Pa., Miss Anna A. Schryver of the Michigan State Normal School, Ypsilanti, Mr. Hermann von Schrenk of the St. Louis Manual Training School, and Mr. Marcus L. Glazer of the St. Cloud., Minn., High School.

Part II consists of a very brief key to some of the commoner orders of Phanerogams and descriptions of the characteristics of these orders with a few genera and species under each. The key is adapted (by permission) from the one in use in the elementary course in botany in Harvard University, and the descriptions were compiled by the author from the most accessible recent floras of the northern United States east of the hundredth parallel. The attempt has been made to simplify the language and condense the descriptions, but not so much as to make them hopelessly bald and unreadable. The plants chosen to constitute this greatly abbreviated flora are those which bloom during some part of the latter half of the ordinary school year, and which have a rather wide territorial range. Enough forms have been described to afford ample drill in the determination of species. Gray’s Manual of Botany or Field, Forest and Garden Botany will of course be employed by the student who wishes to become familiar with the flora of the region here touched upon. Those species which occur in the north-eastern United States only as cultivated plants are so designated, but it has not seemed best to take the necessary space to assign precise ranges or habitats to the native or introduced plants her described. :

Part II

Key anp Fiora 5 j 2 ‘ 3 - . ‘ . 1-61

ELEMENTS OF BOTANY.

INTRODUCTORY.

‘Botany is the science which endeavors to answer every reasonable question about plants.’ 1

Tue plant is a living being, provided generally with many parts, called organs, which it uses for taking in nourishment, for breathing, for protection against its enemies, and for reproducing itself and so keeping up the numbers of its own kind. The study of the individual plant therefore embraces a variety of topics, and the examination of its relation to others introduces many more subjects.

Morphology, or the science of form, structure, and so on, deals with the plant without much regard to its character as a living thing. Under this head are studied the forms of plants and the various shapes or disguises which the same sort of organ may take in different kinds of plants, their gross structure, their microscopical structure, their classification, and the successive stages in the history of the germs from which all but a few of the very simplest plants are formed.

Geographical Distribution, or botanical geography, discusses the range of the various kinds of plants over the earth’s surface. Another subdivision of botany, usually studied along with geology, describes the history of plant life on the earth from the appearance of the first plants until the present time.

1 Professor George L. Goodale.

Vegetable Physiology treats of the plant in action, how it lives, breathes, feeds, grows, and produces others like itself, and how it adjusts itself to the conditions which surround it. This division of the science also considers how the plant attacks other plants or animals (as do mildews and diseasegerms respectively, for example), or how it is attacked by them, what are its diseases and how its life is terminated by these, by old age, or by external causes like frost or drought.

Many of the topics suggested in this outline cannot well be studied in the high school. There is not usually time to take up botanical geography or to do much more than mention the important subject of Economie Botany, the study of the uses of plants to man. It ought, however, to be possible for the student to learn in his high school course a good deal about the simpler parts of morphology and of vegetable physiology. One does not become a botanist — not even much of an amateur in the subject — by reading books about botany. It is necessary to study plants themselves, to take them to pieces and make out the connection of their parts, to examine with the microscope small portions of the exterior surface and thin slices of all the variously built materials or tissues of which the plant consists. All this can be done with living specimens or with those taken from dead parts of plants that have been preserved in any suitable way, as by drying or by placing in alcohol or other fluids which prevent decay. Living plants must be studied in order to ascertain what kinds of food they take, what kinds of waste substances they excrete, how and where their growth takes place and what circumstances favor it, how they move, and indeed to get as complete an idea as possible of what has been called the behavior of plants.

Since the most familiar and most interesting plants spring from seeds, the beginner in botany can hardly do better than to examine at the outset the structure of a few familiar seeds,

INTRODUCTORY. 3 then sprout them and watch the growth of the seedlings which spring from them. Afterwards he may study in a few typical examples the organs, structure, and functions of flowering plants, trace their life-history, and so, step by step, follow the process by which a new crop of seeds at last results from the growth and.development of such a seed as that with which he began.

Meantime it will throw light on the mode of growth of flowering plants to compare them with a few very simple flowerless plants.

After the whole round of vegetable life has been outlined from seed to seed, the student may learn a little about the never-ceasing struggle against unfavorable climates, poor soils, and the direct attacks of living enemies, — in short, the many kinds of adverse influences, such as all plants must meet and overcome in order to maintain their footing on the earth.

Finally, some idea may be gained of the relationships of plants to each other, or Systematic Botany.

CHAPTER I. The Seed and its Germination

1. Germination of Squash-Seed.— Soak some squash-seeds in tepid water for twelve hours or more. Plant these about an inch deep in damp sand or pine sawdust in a wooden box which has had holes enough bored through the bottom so that it will not hold water. Put the box in a warm place (not at any time over 70° or 80° Fahrenheit), and cover it loosely with a board or a pane of glass. Keep the sand or sawdust moist, but not wet, and the seeds will germinate. As soon as any of the seeds, on being dug up, are found to have burst open, sketch one in this condition, noting the manner in which the outer seed-coat is split, and continue to make sketches at intervals of two days, until at least eight stages in the growth of the plantlet have been noted.!

Observe particularly how the-sand is pushed aside by the rise of the young seedlings, and make one sketch to show what part of the plant first appears above the surface. Suggest some reason for the manner in which the sand is penetrated by the rising stem.

The student need not feel that he is expected to make finished drawings to record what he sees, but some kind of sketch, if only the merest outline, is indispensable. Practice and the study of the illustrations hereafter given will soon give some facility even to those who have had little or no instruction in drawing. Consult here Figs. 5 and 7.

2. Examination of the Squash-Seed.— Make a sketch of the dry seed, natural size. Note the little scar at the pointed end of the seed where the latter was attached to its place of growth in the squash. Label this hilum.

Describe the color and texture of the outer coating of the seed. With

_ a scalpel or a very sharp knife cut across near the middle a seed that has been soaked in water for 24 hours. Squeeze one of the portions, held edgewise between the thumb and finger, in such a way as to s parate slightly the halves into which the contents of the seed is naturally divided. Examine with the magnifying glass the section thus reated,

1 The class is not to wait for the completion of this work (which may, if J -#irable, be done by each pupil at home), but is to proceed at once with the examina. i. n of the squash-seed and of other seeds, as directed in the following sections, and 3et some beans to sprouting, so that they may he studied along with the germinatin, -quashes.

make a sketch of it and label the shell or covering of the seed and the kernel within this.

Taking another soaked seed, chip away the white outer shell, called the testa, and observe the thin, greenish inner skin, the tegmen, with which the kernel of the seed is closely covered.

Strip this off and sketch the uncovered kernel. Note that at one end it tapers to a point.

This pointed portion, known as the caulicle, will develop after the seed sprouts into the stem of the plantlet, like that shown at hc in Fig. 1. ;

Split the halves of the kernel entirely apart from each other, noticing that they are only attached for a very little way next to the caulicle, and observe the thickness of the halves and the slight unevenness of the inner surfaces.

These halves are called seed-leaves or cotyledons.

Have ready some seeds which have been soaked for

24 hours and then left in a ee eer re cits Casita loosely covered jar on damp ieee OE Beare GommnEvons

I, longitudinal section of the ripe seed ; I, gerblotting-paper at a tenipers minating seed; he, caulicle; c, cotyledon ; ture of 70° or over until they e, nourishment stored around the cotyledons ; have begun to sprout. s, testa; 2, thickened knot at end of seed;

Split one of these seeds w, primary root; w’', secondary roots.

apart, separating the cotyledons, and observe, at the junction of these, two very slender pointed objects, the rudimentary leaves of the plumule or first bud.

3. Examination of the Bean. — Study the seed, both dry and after 12 hours’ soaking, in the same general way in which the squash-seed has just been examined.

1 The larger the variety of bean chosen, the easier it will be to see and sketch the several parts. The large red kidney bean or the horticultural bean will do well for this examination. :

Notice the presence of a distinct plumule, consisting of a pair of rudimentary leaves between the cotyledons, just where they are joined to the top of the caulicle.

Make a sketch of these leaves as they lie in place on one of the cotyledons, after the bean has been split open.

Note the cavity in each cotyledon caused by the pressure of the plumule.

‘Place that cotyledon from which the sketch was made on the stage of the compound microscope under the lowest-power objective which the microscope has (say 2-inch), with light thrown on the object from above, and sketch the plumule as thus shown.!

4, Examination of the Pea. —There are no very important points of difference between the bean and pea, so far as the structure of the seed is concerned, but the student should rapidly dissect a few soaked peas to get an idea of the appearance of the parts, since he is to study the germination of peas in some detail.

Make only one sketch, that of the caulicle as seen in position after the removal of the seed-coats.?

5. Germination of the Bean and the Pea. — Soak some beans as directed in § 3, plant them, and sketch as there directed.

Follow the same directions with some peas.?

6. Germination of the Horse-Chestnut.— Plant some seeds of the horse-chestnut or the buckeye, study their mode of germination and make out the nature and peculiar modifications of the parts.

Consult Gray’s Botanical Text-Book, vol. I, pp. 19, 20.

%. Conditions Requisite for Germination. — When we try to enumerate the external conditions which can affect germination, we find that the principal ones are light, heat, moisture, and presence of air. A few simple experiments will show what influence these conditions exert.

8. Experiment 1.4 (a) Does Light assist Germination? (b) Does Light retard Germination ? — Put a piece of blotting-paper in the bottom

1 The teacher should at this point give a short illustrated talk to explain in a general way the construction and use of the compound microscope. See Appendix A.

2The teacher will find excellent sketches of most of the germinating seeds described in the present chapter in Miss Newell’s Outlines of Lessons in Botany, Part I, and in Gray’s Lessons in Botany.

3 The pupil may economize space by planting the new seeds in boxes from which part of the earlier-planted seeds have been dug up for use in sketching, etc.

+ This may readily be made a home experiment.

- of a tumbler, and add just water enough thoroughly to soak the paper. Pour out any excess. Place on the paper a few seeds (peas, barley, wheat, oats) that have been soaked for 24 hours; cover to prevent evaporation and put the tumbler in a light place.

Put the same number of other seeds of the same sort in a cup or box which will not admit light.

Add a few drops of water from time to time, if the seeds or paper seem to be drying. Place the cup and tumbler side by side, so that they will have the same temperature, and watch for results.

Tabulate your results something like this:

No. of seeds sprouted in 24hrs. 48 hrs, 72 hrs. 96 hrs. In dark, — — — — In light, — — — —

N. B. — Take special pains to have the conditions of moisture and heat the same in the cup and in the tumbler.

9. Experiment 2.° Relation of Temperature to Germination. — Arrange several vessels asin Exp. 1. Put in each vessel the same number of soaked peas.! Stand the vessels with their contents in places where they will be exposed to different, but fairly constant, temperatures and observe the several temperatures carefully with a thermometer. The following series is merely suggested, — other values may be found more convenient. Note the rate of germination in each place and record in tabular form as follows :

No. of seeds sprouted in 24hrs. 48 hrs. 72 hrs. 96hrs. etc. At 32 degrees, At 50 degrees, At 70 degrees, At 90 degrees,”

10. Experiment 33 Relation of Water to Germination. — Arrange seeds in several vessels as follows :

In the first put blotting-paper that is barely moistened: on this put some dry seeds.

11f peas are used one year, Indian corn another year, squash-seeds another, and so on, a series of data will be obtained which may be quoted to the class after the experiment as above given has been completed.

2 Here and elsewhere throughout the book temperatures are expressed in Fahrenheit degrees, since with us, unfortunately, the Centigrade scale is not the familiar one, outside of physical and chemical laboratories.

3 May be a home experiment.

In the second put blotting-paper that has been barely moistened; on this put seeds that have been soaked for 24 hours.

In the third put water enough thoroughly to soak the paper: use soaked seeds.

In the fourth put water enough to half cover the seeds.

Place the vessels where they will have same temperature and note the time of germination.

Tabulate your results as in the previous experiments.

11. Experiment 4.*1 Will Seeds germinate without Air ?— Place some soaked seeds on blotting-paper in the bottom of .a bottle; close tightly with a perforated rubber stopyer through which has been

passed a long glass tube bent => once at right angles as shown in Fig. 2.

Exhaust the air from the bottle by attaching the tube to an air-pump or an aspirator, and after considerable pumping and while the exhaustion is going on, seal the whole air-tight by heating the tube near the bend with a Bunsen burner or alcohol lamp flame until it can be drawn. out to a thread.

Fig. 2.—Soaked Peas in Stoppered Bottle, The stopper will be more

ready for Exhaustion of Air. certain to prove air-tight if it has been well moistened with glycerine or vaseline before being inserted in the bottle.

Place other seeds of the same kind in another bottle and stopper tightly.

Place other seeds of the same kind in a third bottle ; stopper loosely.

Place the three bottles side by side, so that they will have the same conditions of light and heat. Watch for results, and tabulate as in previous experiments.

Most seeds will not germinate under water, but those of the sunflower will do so, and therefore Exp. 4 may be varied in the following manner :

1 Experiments marked thus * are to be performed by the teacher in the laboratory or class-room.

Remove the shells carefully from a considerable number of sunflower seeds.! Try to germinate one lot of these in water which has been boiled, to remove the air, and then cooled and poured into a bottle which it fills up to the (tightly fitting) rubber stopper. In this bottle then there will be only seeds and water, no airspace. Try to germinate another lot of seeds in a bottle half filled with ordinary water.

12. Germination involves Chemical Changes. —If a thermometer is inserted into a jar of sprouting seeds, for instance peas, in a room at the ordinary temperature, the peas will be found to be warmer than the surrounding air. This rise of temperature is at least partly due to the absorption from the air of that substance in it which supports the life of animals and maintains the burning of fires, namely oxygen.

The union of oxygen with substances with which it can combine, that is with those which will burn, is called owidation. This kind of chemical change is universal in plants and animals while they are in an active condition, and the energy which they manifest in their growth and movements is as directly the result of the oxidation going on inside them as the energy of a steam-engine is the result of the burning of coal or other fuel under its boiler. In the sprouting seed much of the energy produced by the action of’ oxygen upon oxidizable portions of its contents is expended in producing growth, but some of this energy is wasted, by being transformed into heat which escapes into the surrounding soil. It is this escaping heat which is detected by a thermometer thrust into a quantity of germinating seeds.

18. Experiment 5.* Effect of Germinating Seeds upon the Surrounding Air. —When Exp. 4 has been finished, insert into the air above the peas in the second bottle a lighted pine splinter, and note the effect upon its flame.

Besides the proofs of chemical changes in germinating seeds just described, there are other kinds of evidence to the same effect.

1 These are really fruits, but the distinction is not an important one at this point.

Malt, which is merely sprouted barley with its germination permanently stopped at the desired point by the application of heat, tastes much sweeter than the unsprouted grain, and can be shown by chemical tests to have suffered a variety of changes.

Germinating kernels of corn undergo great alterations in their structure (see Fig. 12).

14. The Embryo and its Development.— The miniature plant, as it exists ready-formed in the seed, is called the embryo. In the seeds so far examined the entire contents of the seed-coats consist of the embryo, but this is not the case with the great majority of seeds.

As soon as the young plants of squash, bean, and pea have reached a height of three or four inches above the ground it is easy to recognize important differences in the way in which they set out in life. \

The cotyledons of the squash increase greatly in surface, acquire a green color and a generally leaf-like appearance, and, in fact, do the work of ordinary leaves. In such a case as this the appropriateness of the name seed-leaf is evident enough, — one recognizes at sight the fact that the cotyledons are actually the plant’s first leaves. In the bean the leaf-like nature of the cotyledons is not so clear. They rise out of the ground like the squash cotyledons, but then gradually shrivel away, though they may first turn green and somewhat leaf-like for a time.

In the pea (as in the acorn, the horse-chestnut, and many other seeds) we have quite another plan, the underground type of germination. Here the thick cotyledons no longer tise above ground at all, because they are so gorged with nourishment that they could never become leaves; but the young stem pushes rapidly up from the surface of the soil.

The development of the plumule seems to depend somewhat on that of the cotyledons. The squash-seed has cotyledons

.

which are not too thick to become useful leaves, and so the plant is in no special haste to get ready any other leaves. The plumule, therefore, cannot be found with the magnifying glass in the unsprouted seed, and is almost microscopic in size at the time when the caulicle begins to show outside of the seed-coats.

In the bean and pea, on the other hand, since the cotyledons cannot serve as leaves, the later leaves must be pushed forward rapidly. In the bean the first pair are already well formed in the seed. In the pea they cannot be clearly made out, since the young plant forms several scales on its stem before it produces any full-sized. leaves, and the embryo contains only caulicle, cotyledons, and a sort of knobbed plumule, well developed in point of size, representing the lower scaly part of the stem.

CHAPTER II. The Parts of the Seedling ;— its Development

15. Root, Stem, and Leaf. —By the time the seedling is well out of ground it, in most cases, possesses the three kinds of vegetative organs, or parts essential to growth, of ordinary flowering plants, the root, stem, and leaf. All of these organs may multiply and increase in size as the plant grows older, and their mature structure will be studied in later chapters, but some facts concerning them can best be learned by watching their growth from the outset.

16. The Young Root. — Roots growing in sand or ordinary soil cling to its particles so tenaciously that they cannot easily be studied, and those grown in water have not quite the same form as soil roots. Roots grown in damp air are best adapted for careful study. :

Experiment 6. In what Portions of the Root does its Increase in Length take Place?-—Sprout some peas on moist blotting-paper in a loosely covered tumbler. When the roots are one and a half inches or more long, mark them along the whole length with little dots made with a very small camel’s-hair brush or a bristle dipped in water-proof India ink.

Transfer the plants to moist blotting-paper under a bell glass or a battery jar and examine thé roots at the end of twenty-four hours to see along what portions their length has increased; continue observations on them for several days.

17. Root-Hairs.— Barley, oats, wheat, or red clover seed soaked and then sprouted on moist blotting-paper afford convenient material for studying root-hairs. The seeds may be kept covered with a watch-glass or a clock-glass while sprouting. A few of the red clover seeds should also be sprouted in a deep cell on a microscope-slide. Examine those parts of the root which have these appendages, first with the magnify-_

THE PARTS OF THE SEEDLING. 13 ing glass, then as opaque objects in a cell under a low power of the miscroscope ; finally cut off a very small portion of the root with its hairs and examine in water with a power of 150 to 200 diameters.?

Make several sketches of the root-hairs and compare with Figs. 5 and 19. Notice that they do not cover all portions an

Fie. 3.— Lengthwise Section through Tip of a Root of Barley. (Much magnified.)

d, thick outer wall of epidermis; 6 (portion bounded by the heavy line), the central eylinder of the root; c, the growing-point, from which the root-cap is produced (in this and similar plants) and from which growth in length proceeds ; d, loose ‘eells of the root-cap.

of the rootlets. Where are they most abundant? Observe that each hair is in reality a very slender tube, closed at the ends, and with walls of extreme thinness.

The root-hairs in plants growing under ordinary conditions

1Great care is needed to prevent the root-hairs from becoming distorted by pressure, and they shrivel up in dry air almost at once, are surrounded by the moist soil and wrap themselves around microscopicak particles of earth. Thus they are able rapidly to absorb through their thin walls the soil-water, with whatever mineral substances it has dissolved in it.

18. The Root-Cap.—The tips of young roots and rootlets,

Fie. 4.—Apparatus for Measurement 'of Growth.

as they bore their way through the soil, are protected from injury by a coating of loose cells, called the root-cap, shown at d in Fig. 3. It will.be seen from this figure that no root-hairs proceed from the root-cap, and indeed there is very little absorption of water going on in this place. In the so-

THE PARTS OF THE SEEDLING. 15 called water-hyacinth’ that which occupies the place of an ordinary root-cap is a long sheath, which may be pulled off entire; its large size is possibly due to the fact that it is not worn away by friction against the soil.

19. The Young Stem.—The caulicle, or portion of the stem which lies below the cotyledons, is the earliest-formed portion of the stem. Sometimes this lengthens but little; often, however, as the student knows from his own observations, the caulicle lengthens enough to raise the cotyledons well above ground, as in Fig. 5.

The later portions of the stem are considered to be divided into successive nodes, places at which a leaf (or a scale which represents a leaf) appears, and internodes, portions between the leaves.

The student should watch the growth of a seedling bean or pea and ascertain by actual measurements whether the internodes lengthen after they have once been formed, and if so, for how long a time the increase continues. Fic. 5.— I, a seedling maple, natural , size ; c, cotyledons ; d, plumule; 0; The rate of growth may readily be level of the ground ; II, part of root measured by means of a simple piece of the same, magnified six times, of apparatus, shown in Fig. 4. This showing root-hairs. consists of a pointer ZL supported by an upright stand, moving over a graduated arc, and with a grooved