Sprawling to erect, mostly perennial and succulent herbs, with nodose or jointed stems, often brittle and with fibrous roots. Leaves alternate, rarely falsely whorled, often sheathing at base and entire. Inflorescence mostly condensed cymes, often subtended by involucral bracts or cymbiform spathes, lateral or axillary, rarely solitary or apparently fascicled. Flowers usually hermaphrodite, sometimes polygamous or cleistogamous, 3-merous, regular to irregular, mostly white, blue or pinkish. Perianth 2-seriate; outer 3 sepaloid, free, green to whitish, sometimes membranous, often persistent; inner 3 petaloid, one often larger than the other two, free, united below, ephemeral, decaying or deciduous, mostly ovate. Stamens 6, in 2 whorls, sometimes 2-4 reduced to staminodes, free, epipetalous or adnate to petal bases; filaments often bearded; anthers dithecous, often dissimilar, with broad or narrow connectives, dehiscing longitudinally, rarely by basal pores. Pistil 3-carpellary, syncarpous, 2-3-locular, with 1-several, orthotropous ovules in axile placentas; style simple, terminal with capitate or 3-fid stigmas. Fruit a capsule, sometimes enclosed by fleshy sepals, dehiscent to indehiscent; seeds usually angular, arillate, often muricate, ridged or reticulate with a punctiform or linear scar, usually with copious mealy endosperm and minute embryo beneath an embryotega (disc-like structure).