Page:Popular Science Monthly Volume 47.djvu/816



HEN we mentally survey the floral dress that variegates the solid crust of our globe, the world of plants appears to be divided into a few large groups. We think of the primitive forest with its mossy trees, the slender vines, and the multiform beauties of the orchids; the steppe comes to our minds with its hard, sharp-cutting grasses; and the moist carpeting of the Alpine flora, with gentian and fragrant herbs. The eye lingers longest on the native group; the colored population of our meadows rises before us, the forest with its berried undergrowth, and possibly the bushy river bank and the undulating insulated plant-covering of a pond. Each of the plant groups we have named bears a special expression distinguishing it from all the others. The members of each have certain common features the aggregation of which constitutes the characteristic of the group. In them are included plants which are not at all connected by natural relationship. Ivy is not related to wintergreen or the strawberry to the huckleberry, and all these, again, are far removed from ferns, mosses, and fungi; yet we are satisfied as to the connection of these plants, so that we regard them as members of a definite group, as is represented by our wood flora. So with the other forms we have named, those of the tropical forest, of the steppe, and of the Alpine fields; the plants constituting them are not grouped by blood relationship. Outer circumstances, the conditions of life, have impressed their special characters upon them. The shadow of the wood, the tropical rains, the short summer of the Alps, the aridity of the steppe—all these are factors which have produced in the plants exposed to them common properties more perceived than defined, because they have had effect upon their outer figure as well as upon their vital processes. Thus these groups of plants are developed by the community of their life conditions. They furnish illustrations of Goethe's saying that the manner of life works powerfully on all forms.

We shall study more closely in this paper one of these communities of life conditions—the plant world of the water—and inquire into the connection existing between its most marked peculiarities and the conditions of life afforded by the water. If we walk along the shore of a large pond sheltering a rich growth of plants, or of a bush-lined stream, the vegetable inhabitants will be divided, at first sight, into three groups—the shore plants on the banks; the floating leaves and flowers of the surface plants; and in the depths, hardly visible to the eye, the submerged flora, composed of a few curiously shaped flowering plants, and many