Rootstock of vertical, usually annual tubers (renewed each year). Stem twining to right. Bulblets present or absent. Leaves opposite or alternate, simple; leaf blade broadly ovate to narrowly oblong, margin entire. Male inflorescences spikes, solitary or clustered, or grouped into axillary or terminal panicles. Flowers solitary, sessile; perianth lobes free, incurved; stamens 6, rarely 3 reduced to staminodes, anthers introrse. Female spike sometimes branched. Capsule not reflexed at maturity, usually wider than long. Seeds inserted near middle of capsule, winged all round.

About 120 species or more: mainly in tropical Africa and Asia, none common to both continents; 14 species (five endemic, one introduced) in China.