Fls in sessile axillary congested clusters. Per. 5-partite; fertile stamens 2-3, filaments connate at base, anthers 1-celled; style very short or obsolete, stigma us. capitate; ovules solitary, pend. from basal funicle. Utricle compressed, margins often thickened or winged; seed vertical, lenticular. Herbs, us. decumbent, with opp. lvs. About 170 spp., mainly tropical and subtropical.

Perennial herbs with a slender tap root; stems prostrate to erect, 2.0–3.5 mm diam., green and flushed pink, glabrous to sparsely hairy, with two decurrent lines of hairs, nodes tomentose. Leaves (20–)30–83 × 6–12 mm, leaves usually narrowly elliptic or lanceolate, sometimes linear to linear- oblong, light green or yellow-green with midrib and lateral veins pink, glabrate to sparsely hairy on margins, midrib, and both surfaces, apex acute; margins distinctly denticulate; base attenuate. Spikes globular or shortly oblong, 0.5–0.8 mm diam., clustered, with 15–20 flowers; rachis sparsely hairy, flowers subtended by 1 bract and 2 bracteoles; bracts and bracteoles 1.5–2.0 × 0.6–0.8 mm, lanceolate, cream, glabrous, membranous, shortly acuminate to acute. Perianth segments 2.3–2.4 × 0.6–0.8 mm, lanceolate, cream, glabrous, membranous, shortly acuminate to acute; anthers c. 0.15 mm long, yellow; filaments 3–4 mm long, translucent; style 0.1– 0.2 mm long; stigma capitate; ovary 0.4–0.5 mm long, green. Fruit 1.7–1.8 × 1.9–2.1 mm, cream and fl ushed pink, obovoid, compressed, indehiscent. Seeds 0.9–1.0 × 0.8–0.9 mm, cream to yellow, often with a light brown centre, compressed.

Annual or perennial herbs; stems erect, creeping, procumbent or decumbent, sometimes floating. Lvs opposite, entire, sessile or petiolate. Infls sessile or pedunculate, capitate or spicate, usually axillary; fls usually ☿, sometimes ♀, each with a scarious bract and 2 scarious bracteoles. Tepals 5-merous, often dorsally compressed, equal or unequal, free, glabrous or hairy. Stamens 2-5; filaments connate in a short tube at the base; staminodes sometimes present; anthers small, 1-celled. Ovary compressed or terete; ovule 1, pendulous on long funicle. Style short; stigma capitate. Fr. an utricle, indehiscent, often compressed, with persistent perianth, falling with or without bracteoles. Seed vertical.