Annual or perennial succulent herbs, with conspicuous papillose epidermal cells. Leaves opposite below, alternate on flowering branches. Flowers solitary, axillary, leaf-opposed or terminal, sessile or shortly pedicellate; sepals 5, free, unequal (2 larger than others); petaloid staminodes numerous, white; stamens numerous; styles 5; ovary inferior to semi-superior, 5-locular; ovules numerous, axile. Fruit a 5-locular capsule, valves winged, opening when wet via apical slits; seeds numerous.
Between 16 to 101 species depending on which taxonomic concept is followed, chiefly from South Africa, a few Mediterranean and on nearby islands; 4 species naturalised in Australia, others commonly grown for ornament.