Description from Flora of China
Herbs, perennial or annual, twining, dioecious. Stems, branchlets, and petioles with rigid 2-armed stalked hairs. Stems coarse, 6-ridged or winged. Leaves opposite, well developed leaves ± cordate and 3-7(-9)-lobed, terminal leaves sometimes ± ovate and simple, abaxially with yellowish brown resinous glands and dots. Male inflorescences laxly paniculate. Male flowers: filaments straight in bud; female inflorescences a conelike spicate cyme; bracts imbricate, persistent and enlarged in fruit, margin entire. Female flowers: calyx thinly membranous, appressed to ovary, margin entire; ovary ± surrounded by appressed calyx; styles 2-branched; branches caducous. Achene broadly ovoid; calyx persistent, appressed to achene; pericarp crustaceous; embryo spirally involute; cotyledons narrow.
Three species: Asia, Europe, North America; three species (one endemic) in China.