Succulent annual or perennial herbs. Leaves alternate to subopposite, usually sessile, terete to flat; axillary hairs present. Flowers few–many, in compact cymes subtended by several involucral leaves, each flower subtended by a (usually unequal) pair of scarious bracts; sepals united at base, the tubular portion fused to the lower half of ovary; petals 4–6, fused at base; stamens 8-many; ovary semi-inferior, ovules numerous, style cleft into 3–7 stigmatic arms. Capsule circumsciss, the sepals and remains of the petals falling with the upper part of capsule; seeds numerous, orbicular to ± reniform, smooth or variably tuberculate to papillate.
About 100 species in tropics and warmer temperate regions, many of them weedy; c. 20 species in Australia.