Herbs, erect or scandent, annual or perennial; latex 0. Lvs opposite or alternate, simple or palmately divided, stipulate, petiolate. Fls unisexual, apetalous, in axillary infls; ♂ infls paniculate; ♀ infls sessile, crowded or strobilate with large persistent imbricate bracts. ♂ fls with perianth 5-merous; segments imbricate; stamens 5, erect in bud; filament short; anthers 2-celled; rudimentary ovary 0. ♀ fls with perianth entire, membranous, closely enfolding ovary. Ovary sessile, 1-locular; style central, 2-partite; ovule solitary, pendulous from the apex of the loculus, anatropous. Fr. an achene. Seeds with fleshy endosperm; embryo curved or spirally involuted.