Where the Rhone enters the Mediterranean, there are some 40,000 acres of sandy and clayey land called the Camargue. The bare sand near the sea is often flooded and swept by violent storms in winter; anything which tries to grow there is usually carried[75-b] off and destroyed. [note 75-b] Drude, _l.c._; Schimper, _l.c._; Warming, _l.c._; _Colonial Reports_, No. 3, Miscellaneous. Schimper, _Indo-Malayische Strandflora_. But, after a time, one finds here and there a solitary plant of a kind of Saltwort (_Salicornia macrostachya_) which has withstood the strain: its branches gather a little sand and hold it together, and its roots gradually explore and tie down the soil around it. Next winter it can stand the sweep and scour of the stormy water; next summer other plants begin to grow on this tiny sand-heap, and the "touradon," as it is called, is now fairly well established. It goes on growing until it may be, after a few years, six feet in diameter. Eventually the salt gets washed out of the soil and these little heaps become united by a continuous covering of green plants in which shrubs and then trees begin to grow.[76] By this time of course the sand has accumulated farther out to sea and the same process is going on there. [76] Flahault, after Schimper, _l.c._ In Britain we have the "sea meadows" of Sea-grass, which covers the submerged sand and mudbanks near the mouths of great rivers. The waving green grasslike leaves form a rich submarine meadow. They are used for stuffing pillows and cushions, especially in Venice, but their real importance in the world depends upon their being able to tie down and fix permanently those unseen shifting banks which form a real danger to all navigation. These plants are very remarkable. They lived, no doubt, at one time on the land, like most of the flowering plants. But, like the whale and the seal, they have been driven to take refuge below the ocean. They are not easily seen, and, indeed, one may wander for years along the sea-coast and never suspect that great meadows of Zostera (the Eelwrack, Grasswrack, or Sea-grass) are flourishing under water. But, one might ask, how is the pollen of its flowers carried? Obviously neither insects nor the wind can be of any service. The pollen of Zostera is, however, of the same weight exactly as the water, so that it neither rises to the surface nor sinks to the bottom, but floats to and fro until it reaches the outspread styles of another plant. This is perhaps the most remarkable arrangement known for the carrying of pollen.