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a genus of lichens with a binary thallus. The prothallus is horizontal and grows in the form of nodules or scales, which sometimes later atrophy; the secondary thallus, which grows out of the prothallus, is vertical, and consists of subulate, hornlike, cup-shaped, or bushy formations called podetia. The apothecia, found at the tips of the branches or on the apexes of the podetia, are rounded or hemispheric and red, brown, or, more rarely, yellow in color. There are about 300 species of Cladonia, growing in forests (chiefly pine), tundras, and swamps. In the North several species of Cladonia are used as forage for reindeer. Some species contain usnic acid and have medicinal value. In the USSR there are about 100 species.