Annual or perennial herbs or undershrubs, sometimes fleshy. Leaves simple, entire or subentire, opposite, spread, or spuriously whorled, sometimes minute, stipulate or not. Stipules often small, scarious, fugacious. Flowers axillary, solitary, clustered or fascicled, cymose, pseudoracemose, or subumbellate, actinomorphic, usually ♀, often small and inconspicuous. Tepals 5, either free, imbricate in bud, herbaceous with scarious often white margins or entirely scarious, persistent, conniving before and after anthesis, or a distinctly gamophyllous, corolline or calycine 3—8-lobed perianth with usually persistent, herbaceous lobes imbricate or rarely valvate in bud. Stamens 1-~, perigynous or hypogynous, free or connate at the base, either singly or in groups, often alternate with the perianth lobes. Anthers 2-celled, dehiscing lengthwise. Disk annular or absent. Ovary superior, semi-inferior or inferior, 1—9-celled. Ovules 2-~, solitary or ~, basal, apical or axile. Styles 1-~. Capsule or drupe, 2—~-seeded, often enclosed by the perianth and falling off with it. Distr. About 23 genera (if Mesembryanthemum is split into segregates many more) and over a thousand spp.(over 800 belonging to Mesembryanthemum), distinctly centering in the S. hemispherical subtropics of the Old World, mainly in S. Africa, with a secondary centre of development in Australia, in Malaysia and other essentially forested tropics poorly represented by some widely distributed, partly peritropical genera and widely distributed weeds.