Fls small, prefect, regular, in clusters variously arranged; bracteoles ochreate; tepals us. 5, ± connate at base; stamens 4-8; styles 2-3; fr. lenticular or trigonous, ± invested by persistent tepals. Annual or perennial herbs of wide, mostly temperate, distribution; some 175 spp.

Annual or perennial herbs, occasionally small shrubs, sometimes aquatic or ± scrambling; stems usually solid, with nodes usually obviously jointed and often swollen. Lvs cauline, very variable but usually considerably longer than wide, usually entire; ochreae well-developed, scarious. Infl. axillary or terminal, usually a fascicle, spiciform raceme, capitate head, or diffuse panicle; fls generally ☿, sometimes unisexual (plants monoecious or dioecious). Pedicels generally jointed. Perianth segments (4)-5-(6), persistent but usually not markedly accrescent, free or united at base, equal or nearly so, white, pink to crimson, not keeled. Stamens (3)-5-8-(9). Styles 2-3, variable in length. Fr. a biconvex or trigonous nut, enclosed or slightly exserted from the persistent, spineless perianth valves.