Annual herbs or short-lived perennial shrubs, glabrous or pubescent. Leaves alternate or opposite, sessile, ± linear. Flowers bisexual, mostly solitary in axils, each subtended by 2 (usually leaf-like) bracteoles; perianth segments 5 (3 outer, 2 inner), free or shortly united at base; stamens 5; stigmas 2. Fruiting perianth segments usually developing a transverse wing on the back; pericarp membranous or cartilaginous. Fruit a utricle; seed orbicular, horizontal, testa membranous, embryo spiralled.
Probably over 100 species (but treated variably) in Asia, Europe and Africa; 1 species in Australia, probably naturalized.