Page:Popular Science Monthly Volume 47.djvu/817

From Wikisource
Jump to navigation Jump to search
This page has been proofread, but needs to be validated.
799
THE LIFE OF WATER PLANTS.

of the lower orders belonging for the most part to the little microscopic world. The shore plants form a transition class between the vegetation of the land and that of the water. Taking root in damp soils, or perhaps under water, they lift the greater part of their stems with their leaves and flowers above the surface, joining the land flora in their methods of growing, respiring, and feeding. Among the shrubbery of the meadow, overtopped by single gray-stemmed alders, rise little forests of rustling reeds, both interspersed with variegated masses of various herbs, among which sharp-edged sedges and round-stalked rushes take the first places, by the side of the fragrant calamus, irises, and the umbel—flowers of the tall water violets. Farther ashore rise the beautiful white panicles of the swamp meadowsweet, with the grayish—green leaves and violet flowers of the bittersweet. We must not overlook the white stars of the willow-leaved aster, signs of the beginning of autumn, and the great bindweed, whose threadlike stems find welcomed support on the hard stalks of the reeds. Altogether a variegated picture, the characteristic points of which are hard to separate from the impression of the whole. This is easier to do with two other forms of shore flora which have been developed under peculiar conditions furnished by our waters—the flora of the sandy sea-beaches and that of the unfathomable, unstable morasses of the mouths of tropical rivers. In the former instance a striking appearance is given to the vegetation by the salt contained in the soil. Plants with usually inconspicuous flowers, and also a pretty blue aster, have adapted themselves to life by the salt water. They are sometimes distinguished by their fleshy leaves, the properties of which stand in so close relation to the presence of salt in their habitat that when one is far from the sea he can judge by their presence whether there is salt in the soil. Characteristic of the tropical morasses are the mangroves, a group of arborescent plants which stand as if on stilts on long, bracing roots sent out from all parts of their stems. The young shoots are hard, dagger-shaped bodies about a metre long, which finally drop down and bore perpendicularly into the slime so that they shall not be disturbed by the current, and may become fixed in the mud. In both of these shore regions the special forms appear to be developed in connection with the peculiar features of the locality.

These adaptations to special conditions thus easily recognized in the shore vegetation are greatly multiplied in the water plants proper. The better to understand them, we must, before going into particulars, devote a few words to the origin of the water flora. Among them are representatives of various orders and classes. They may be divided into plants that have strayed from the land into the water, and those whose original home is that