Rootstock of annual tubers; tubers solitary or paired, usually unstalked (in Asian species), poisonous (in wild species). Stem twining to left, glabrous, rarely hairy. Bulblets present. Leaves alternate, simple; leaf blade ± ovate, margin entire. Male inflorescences of spikes or racemes clustered or in panicles. Flowers with perianth lobes free; stamens 6. Capsule reflexed at maturity, longer than wide. Seeds inserted near apex of capsule; wing pointing toward capsule base.

Five or six species: E hemisphere; one species in China.