Oyster Green, a name given to marine algae of the genus ulva, which are also called green laver and sea lettuce. The ulvas belong to the ehlorospermous class of seaweeds, distinguished by their green spores, and the generally green color of their fronds. There are several species of ulva common to both shores of the Atlantic, the most abundant on our coast being U. latmima and U. lactuca; they are from 3 in. to 2 ft. long, and 3 to 12 in. broad, often sinu-ous on the margin, and wavy or plaited; they are very thin, smooth, and glassy, and appear like very fine bright green silk. The plants are very common on oyster beds, and are frequently used by dealers to decorate their heaps of oysters. The plant is the most valuable seaweed for a salt-water aquarium, it being one of the few that will thrive and give off oxygen in the quiet waters of a marine tank. Among the seaweeds eaten in Europe, under the impression that they have some antiscorbutic properties, is the true laver, the related porphy-ra; and the ulvas are eaten raw, with lemon juice, as green laver.

In Scotland they are sometimes used as a remedy for headache, being bound over the forehead.