Herbaceous tuber-bearing vines; leaves palmately and reticulately veined; flowers unisexual, dioecious; perianth parts connate, at least basally; stamens in staminate flowers 6, all fertile or 3 abortive, around a reduced ovary; staminodia of pistillate flowers 6; ovary of pistillate flower inferior, 3-celled; styles 3; stigmas entire or bifid; ovules 2 in each cell; fruit capsular. 10 genera, over 650 species, mainly tropical.