Annual or perennial herbs, often with a thickened taproot, usually glabrous. Leaves alternate, opposite or rosetted at base, usually sessile, simple, commonly fleshy; stipules absent but leaf blades sometimes dilated and sometimes connate around the stem. Inflorescence a terminal, few–many flowered cyme or cymose panicle, or flowers solitary in axils. Flowers bisexual, rarely unisexual; sepals mostly 2, free or fused at base; petals usually 5, free or fused at base; stamens 3, 5 or in multiples of 3; ovary superior, 1 locular; ovules 1–many; style partly or wholly cleft into 3 stigmatic arms (Victorian plants). Fruit a capsule, dehiscing longitudinally into 3 or 4 valves, or an indehiscent or irregularly dehiscent capsule or utricle (not in Victoria).
About 226 species in 15 genera, from western America, northern Asia and Europe, Australia and New Zealand; about 70 species in 3 or 4 genera in Australia.