Perennial waterplants with a tuberous, elongate or cylindrical and often branched rootstock or rhizome which produces a tuft of leaves and the inflorescences. Leaves submerged and/or floating (very seldom emerged), with a mostly distinct midrib and one or more pairs of parallel main nerves, connected by numerous cross-veins. Inflorescence long-peduncled, emerging above the water surface, in bud enveloped by a caducous or rarely persistent spathe, composed of 1 (in Mal.) or 2-11 spikes. Flowers (in Mal.) bisexual, spirally arranged, turned towards all directions. Tepals 2, mostly persistent, rarely caducous. Stamens 6, in 2 whorls. Ovaries 3(-4-5), free, sessile, narrowed into the style with a stigmatic ridge on the inner side; ovules 2-8 per carpel. Fruits with a mostly distinct, lateral or terminal, often curved beak. Seeds without endosperm; testa mostly a single envelope, sometimes, however, split into two envelopes, the inner one, brown and closely fitting the embryo, the outer loose, transparent and reticulately veined; embryo with the plumule fitting in a groove or not, or without plumule (the embryos of all species with a double testa seem to have no plumule). Distr. About 40 spp. described, from Africa (Ethiopia to the Cape), Madagascar, India & Ceylon, through SE. Asia (to c. 30° NL) and Malesia to SW., N. and E. Australia (to 34° SL), centering in Africa and Madagascar.