Annual herbs. Leaves simple, entire, dentate or pinnatisect, petiolate, becoming sessile and stem-clasping below inflorescence. Inflorescences bracteate cymes often branching into several compact dichasia. Flowers small, sessile, blue, rose-red or white; bracts scale-like, clasping and often retaining fruit for some time; sepals 1–30, connate in a short tube, not rolled at anthesis, enlarging in fruit; corolla more or less actinomorphic, 5-lobed, with a short tube c. as long as lobes, lobes subequal; stamens 3, filaments inserted in throat of corolla-tube; style slender, stigma shortly 3-branched. Cypsela dry, surmounted by persistent calyx, ridged where 2 cells aborted.
About 200 species, mostly from the Northern Hemisphere but also South America and South Africa; 5 species naturalised in Australia.