Annual to perennial herbs; glabrous except for scabrid angles of stems. Leaves opposite or pseudo-verticillate; stipules scarious, not connate around the node; bracts scarious. Flowers in terminal dichasia, 5-merous, bisexual; sepals 5, free, carinate, more or less hooded; petals narrow, emarginate, shorter than sepals; stamens (1–)3–5; ovary 1-celled with several ovules, style 1, trifid above. Capsule broadly ovoid, splitting almost to the base by 3 valves; seeds several, angular-reniform, finely but bluntly tuberculate.
16 species, cosmopolitan; 1 native to NT and 1 naturalised in Australia.