Page:First course in biology (IA firstcourseinbio00bailrich).pdf/33



CHAPTER I

NO TWO PLANTS OR PARTS ARE ALIKE

(Hemlock.)

If one compares any two plants of the same kind ever so closely, it will be found that they differ from each other. The difference is apparent in size, form, color, mode of branching, number of leaves, number of flowers, vigor, season of maturity, and the like; or, in other words, all plants and animals vary from an assumed or standard type.

If one compares any two branches or twigs on a tree, it will be found that they differ in size, age, form, vigor, and in other ways (Fig. 1).

If one compares any two leaves, it will be found that they are unlike in size, shape, color, veining, hairiness, markings, cut of the margins, or other small features. In some cases (as in Fig. 2) the differences are so great as to be readily seen in a small black-and-white drawing.