Annual, biennial, or perennial herbs. Leaves exstipulate, very narrow, joined at the base. Inflorescence mostly reduced dichotomous cymes, or flowers solitary in the leaf axils, at the base enveloped by two scarious bracts. Flowers perigynous; Sepals 4 or 5, with scarious margin. Petals 0. Stamens 1-10, connate at the base, sometimes alternating with staminodes. Ovary 1-ovuled; Fruit a membranaceous utricle surrounded by the thickened hard hypanthium. Seeds compressed, glabrous with thin testa.
Asia-Tropical: New Guinea present, Australasia, New Zealand present, temperate and subtropical Europe and N Africa present
About 10 species, mainly in temperate and subtropical Europe and N Africa, also in Australia and New Zealand In Malesia one species in New Guinea.
Several species are very polymorphous and particularly by earlier Euro-pean authors divided into numerous segregate species, so that as many as 150 species have been described.