Annual, rarely perennial, usually monoecious, sometimes dioecious, prostrate to erect herbs. Lvs alternate, entire. Infl. cymose, composed of axillary or terminal spikes; spikes sessile or pedunculate, solitary or clustered (paniculate). Fls densely arranged and each subtended by a bract and 2 bracteoles; bracts and bracteoles occasionally spiny, often varying in length in each cymose cluster. Tepals (2)-3 or (4)-5, membranous, green, brown, red, or hyaline, persistent. Stamens as many as tepals, free; staminodes 0. Stylar branches 2-3-(4), with stigmatic surface to near base; ovule 1, sessile. Fr. dry, membranous, indehiscent, or dehiscent and circumscissile; pericarp usually smooth, enclosed in persistent perianth. Seed usually glossy, smooth and black or dark brown.