RHIPSALIS

cactus genus of about 60 species, family Cactaceae, native to tropical and subtropical America, West Indies, Africa, Madagascar, and Sri Lanka. Rhipsalis is the only Old World representative of the cactus family. Theories proposed to account for this puzzling distribution include: (1) dispersal of the genus at an earlier geologic period when South America and Africa were joined; (2) transportation of the sticky seeds on the feet of birds; (3) floating and rafting long distances; and (4) dispersal by human agency. These small, much-branched plants usually grow perched upon trees; some species grow among rocks or in the ground. Rhipsalis species are cultivated as much for their strange form as for their small but numerous flowers. Small fleshy berries follow. Easter cactus (Rhipsalis, or Rhipsalidopsis, rosea), a popular spring-blooming ornamental, has fragrant 2.5-centimetre (1-inch) rosy flowers that open in the Sun. Rhipsalis megalantha has yellow flowers 4 cm across. Species of Lepismium, Pfeiffera, Erythrorhipsalis, Acanthorhipsalis, and Hatiora are usually combined into the genus Rhipsalis.