Fleshy, glabrous annual herbs. Stems jointed, branched. Leaves reduced to scales, opposite and connate in pairs, forming a short sheath. Clusters (cymes) mostly 3-flowered, 2 on each node, embedded in the cavity of the axis and more or less adnate to its wall, subtended by bracts and forming terminal, simple or branched spike-like inflorescences. Bracts persistent, opposite, connate, cup-like. Flowers hermaphrodite, coalescent (the lateral ones in each cyme usually sterile, rarely pistillate). Perianth fleshy, white or brownish, of 3 fused segments, 3-dentate at tip, containing water-accumulating cells with bar-thickening walls. Stamens 2, rarely 1. Stigmas 2, subulate. Fruit ovoid or oblong, with membranous pericarp, included in the spongy perianth. Seeds vertical, almost ovoid, covered with short, often curved or hooked hairs; perisperm scanty; embryo bent.