THE LIFE OF WATER PLANTS. 799 



of the lower orders belonging for the most part to the little micro- 

 scopic 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 beauti- 

 ful 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 



