Annual or perennial herbs, without stinging hairs. Leaves alternate, petiolate,simple and entire; stipules mostly 0. Inflorescences small, axillary, cymose, clustered. Flowers hermaphrodite and unisexual in the same cluster (plants polygamous), bracteolate, green. Perianth of hermaphrodite and staminate flowers of 4 segments, elongating after flowering, that of pistillate flowers tubular, 4-toothed, not elongating. Stamens 4; filaments free, inserted at base of tepals, inflexed in bud, straightening elastically at flowering. Ovary 1-celled, ovoid or oblong; stigma sessile or borne on a very short style, tufted. Achenes more or less ovoid, enclosed in the persistent perianth.