Succulent or fleshy herbs or undershrubs. Leaves opposite or alternate, generally simple; stipules wanting. Flowers regular, hermaphrodite or rarely unisexual. Calyx persistent, free, usually 3–5-fid or -partite. Petals as many as the sepals, free or more or less cohering into a lobed corolla, inserted at the base of the calyx. Stamens as many or twice as many as the petals, inserted with the petals and sometimes adnate to them. Ovary superior, of as many carpels as petals; carpels free or connate below, 1-celled, usually with a small gland or scale at the base of each; styles simple; ovules usually numerous, attached to the ventral suture (few in Tillœa). Fruit of several 1-celled follicles, dehiscing along the ventral suture. Seeds few or many, minute, albuminous; embryo terete, cotyledons short.

A rather large order, spread over the whole world except Polynesia. Particularly abundant in South Africa, where nearly half the species are found; also plentiful in the rocky districts of Europe and central Asia; rare in Australia, and South America. Genera about 15; species estimated at 400. All the species are inert, and are of little importance from an economic point of view. The single New Zealand genus is almost cosmopolitan.