Elements of Structural and Systematic Botany

All matter is composed of certain constituents (about seventy are at present known), which, so far as the chemist is concerned, are indivisible, and are known as elements.

Of the innumerable combinations of these elements, two general classes may be recognized, organic and inorganic bodies. While it is impossible, owing to the dependence of all organized matter upon inorganic matter, to give an absolute definition, we at once recognize the peculiarities of organic or living bodies as distinguished from inorganic or non-living ones. All living bodies feed, grow, and reproduce, these acts being the result of the action of forces resident within the organism. Inorganic bodies, on the other hand, remain, as a rule, unchanged so long as they are not acted upon by external forces.

All living organisms are dependent for existence upon inorganic matter, and sooner or later return these elements to the sources whence they came. Thus, a plant extracts from the earth and air certain inorganic compounds which are converted by the activity of the plant into a part of its own substance, becoming thus incorporated into a living organism. After the plant dies, however, it undergoes decomposition, and the elements are returned again to the earth and atmosphere from which they were taken.

Investigation has shown that living bodies contain comparatively few elements, but these are combined into extraordinarily complex compounds. The following elements appear to be essential to all living bodies: carbon, hydrogen, oxygen, nitrogen, sulphur, potassium. Besides these there are several others usually present, but not apparently essential to all organisms. These include phosphorus, iron, calcium, sodium, magnesium, chlorine, silicon.

As we examine more closely the structure and functions of organic bodies, an extraordinary uniformity is apparent in all of them. This is disguised in the more specialized forms, but in the simpler ones is very apparent. Owing to this any attempt to separate absolutely the animal and vegetable kingdoms proves futile.

The science that treats of living things, irrespective of the distinction between plant and animal, is called "Biology," but for many purposes it is desirable to recognize the distinctions, making two departments of Biology,-Botany, treating of plants; and Zo?logy, of animals. It is with the first of these only that we shall concern ourselves here.

When one takes up a plant his attention is naturally first drawn to its general appearance and structure, whether it is a complicated one like one of the flowering plants, or some humbler member of the vegetable kingdom,-a moss, seaweed, toadstool,-or even some still simpler plant like a mould, or the apparently structureless green scum that floats on a stagnant pond. In any case the impulse is to investigate the form and structure as far as the means at one's disposal will permit. Such a study of structure constitutes "Morphology," which includes two departments,-gross anatomy, or a general study of the parts; and minute anatomy, or "Histology," in which a microscopic examination is made of the structure of the different parts. A special department of Morphology called "Embryology" is often recognized. This embraces a study of the development of the organism from its earliest stage, and also the development of its different members.

From a study of the structure of organisms we get a clue to their relationships, and upon the basis of such relationships are enabled to classify them or unite them into groups so as to indicate the degree to which they are related. This constitutes the division of Botany usually known as Classification or "Systematic Botany."

Finally, we may study the functions or workings of an organism: how it feeds, breathes, moves, reproduces. This is "Physiology," and like classification must be preceded by a knowledge of the structures concerned.

For the study of the gross anatomy of plants the following articles will be found of great assistance: 1. a sharp knife, and for more delicate tissues, a razor; 2. a pair of small, fine-pointed scissors; 3. a pair of mounted needles (these can be made by forcing ordinary sewing needles into handles of pine or other soft wood); 4. a hand lens; 5. drawing-paper and pencil, and a note book.

For the study of the lower plants, as well as the histology of the higher ones, a compound microscope is indispensable. Instruments with lenses magnifying from about 20 to 500 diameters can be had at a cost varying from about $20 to $30, and are sufficient for any ordinary investigations.

Objects to be studied with the compound microscope are usually examined by transmitted light, and must be transparent enough to allow the light to pass through. The objects are placed upon small glass slips (slides), manufactured for the purpose, and covered with extremely thin plates of glass, also specially made. If the body to be examined is a large one, thin slices or sections must be made. This for most purposes may be done with an ordinary razor. Most plant tissues are best examined ordinarily in water, though of course specimens so mounted cannot be preserved for any length of time.[1]

In addition to the implements used in studying the gross anatomy, the following will be found useful in histological work: 1. a small camel's-hair brush for picking up small sections and putting water in the slides; 2. small forceps for handling delicate objects; 3. blotting paper for removing superfluous water from the slides and drawing fluids under the cover glass; 4. pieces of elder or sunflower pith, for holding small objects while making sections.

In addition to these implements, a few reagents may be recommended for the simpler histological work. The most important of these are alcohol, glycerine, potash (a strong solution of potassium hydrate in water), iodine (either a little of the commercial tincture of iodine in water, or, better, a solution of iodine in iodide of potassium), acetic acid, and some staining fluid. (An aqueous or alcoholic solution of gentian violet or methyl violet is one of the best.)

A careful record should be kept by the student of all work done, both by means of written notes and drawings. For most purposes pencil drawings are most convenient, and these should be made with a moderately soft pencil on unruled paper. If it is desired to make the drawings with ink, a careful outline should first be made with a hard pencil and this inked over with India-ink or black drawing ink. Ink drawings are best made upon light bristol board with a hard, smooth-finished surface.

When obtainable, the student will do best to work with freshly gathered specimens; but as these are not always to be had when wanted, a few words about gathering and preserving material may be of service.

Most of the lower green plants (alg?) may be kept for a long time in glass jars or other vessels, provided care is taken to remove all dead specimens at first and to renew the water from time to time. They usually thrive best in a north window where they get little or no direct sunshine, and it is well to avoid keeping them too warm.

Numbers of the most valuable fungi-i.e. the lower plants that are not green-grow spontaneously on many organic substances that are kept warm and moist. Fresh bread kept moist and covered with a glass will in a short time produce a varied crop of moulds, and fresh horse manure kept in the same way serves to support a still greater number of fungi.

Mosses, ferns, etc., can be raised with a little care, and of course very many flowering plants are readily grown in pots.

Most of the smaller parasitic fungi (rusts, mildews, etc.) may be kept dry for any length of time, and on moistening with a weak solution of caustic potash will serve nearly as well as freshly gathered specimens for most purposes.

When it is desired to preserve as perfectly as possible the more delicate plant structures for future study, strong alcohol is the best and most convenient preserving agent. Except for loss of color it preserves nearly all plant tissues perfectly.

* * *