Annual or perennial, erect or procumbent and mat-forming herbs with a woody base; usually scabrid-pubescent, rarely glabrous. Leaves opposite or pseudo-verticillate; stipules silvery-scarious; bracts prominent, silvery-scarious. Flowers in dense, simple or compound, terminal and lateral dichasia, in some species almost concealed by the bracts, 5-merous, bisexual; sepals 5, free, more or less hooded; petals absent, or 5 and minute; stamens usually 5; ovary 1-celled with 1 ovule, style more or less bifid. Fruit an indehiscent achene enclosed by persistent calyx; seed 1, subglobose to more or less reniform, smooth to finely punctate.
Over 100 species, cosmopolitan; 3 naturalised in Australia.