Grasswrack, or Zostera, L. a perennial native plant, of two species, the principal of which is the marina, or Sea-grasswrack, found on sea-shores, and in salt-water ditches near Yarmouth.

This vegetable grows at the bottom of the ocean, as common as the mosses thrive in woods : it is thrown on shore by the tide in such abundance, that mounds or dams, are constructed with its assistance, to prevent the encroachment of the sea. The green leaves are said to be an useful and durable substitute for thatch : when exposed to the' air and weather, they become white. - The inhabitants of Gothland, employ the grasswrack as an excellent manure, and likewise for stuffing their beds, as it is softer than hay or straw. - Horses and swine eat this herb, but it is not relished by cows, unless mixed with hay. - The ashes obtained from the whole plant are, with great advantage, employed by the Germans, in the manufacture of glass.