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Tortula (order Pottiales) A genus of mosses which form greenish, sometimes hoary patches or cushions. The leaf nerve is usually excurrent. Capsules are erect, ellipsoid or cylindrical, straight or slightly curved, with a beaked lid. There are about 280 species, found mainly in temperate regions. T. muralis is common on brick and stone walls throughout Britain, even in towns. The leaves are broadly tongue-shaped, and the nerve extends well beyond the leaf tip to form a long hair point. T. ruraliformis (T. ruralis ssp. ruraliformis) often forms extensive carpets on sand-dunes; when moist the plants are orange-brown or golden-green in colour.