Perennial, rarely annual, diffusely branched, xerophytic or halophytic undershrubs or prostrate herbs. Leaves opposite, usually 1-2-foliolate, rarely more than 2-foliolate or simple: stipules rarely thorny; leaflets cylindrical or flat, usually fleshy or leathery. Flowers solitary axillary, pedicellate, actinomorphic, hypogynous, 4-5-merous, white or yellow, sometimes with a purple or red basal spot; disc fleshy, angular, cup-shaped or concave. Sepals 4-5, persistent or deciduous, imbricate. Petals 4-5, free, with or without a claw, imbricate or contorted. Stamens 8-10, inserted at the base of the disc, filaments usually longer than petals, filiform, usually appendaged with a membranous scale within the base, rarely unappendaged, anthers oblong-ovate to rotundate. Carpels 4-5, united; ovary sessile, 4-5-angled, (2.3-) 4-5-loculed, each locule with 2 or more, superposed, pendulous ovules; style angular, stigma minute. Fruit 4-5-angled or winged, septicidal, loculicidal or indehiscent capsule, with 1 or more seeds in each locule. Seeds pendulous, endospermous; embryo straight with oblong cotyledons.