Encyclopaedia Britannica 11th Edition


, in botany, a natural order of Monocotyledons, confined to tropical and sub-tropical America. It includes the pine-apple (fig. 1) and the so-called Spanish moss (fig. 2), a rootless plant, which hangs in long grey lichen-like festoons from the branches of trees, a native of Mexico and the southern United States; the water required for food is absorbed from the moisture in the air by peculiar hairs which cover the surface of the shoots. The plants are generally herbs with a much shortened stem bearing a rosette of leaves and a spike or panicle of flowers. They are eminently dry-country plants (xerophytes); the narrow leaves are protected from loss of water by a thick cuticle, and have a well-developed sheath which embraces the stem and forms, with the sheaths of the other leaves of the rosette, a basin in which water collects, with fragments of rotting leaves and the like. Peculiar hairs are developed on the inner surface of the sheath by which the water and dissolved substances are absorbed, thus helping to feed the plant. The leaf-margins are often spiny, and the leaf-spines of Puya chilensis are used by the natives as fish-hooks. Several species are grown as hot-house plants for the bright colour of their flowers or flower-bracts, e.g. species of Tillandsia, Billbergia, Aechmea and others.