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 Zoölogy, 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.”