Procumbent, diffuse glabrous, papillose or pubescent-succulent, mostly annual herbs. Leaves opposite, petiolate or sessile, those of a pair often unequal, entire; leaf-bases membranous-dilated, often connate in pairs. Flowers axillary, solitary or clustered or glomerulate, sessile or pedicellate. Calyx campanulate, 5-lobed, each lobe with a dorsal subapical mucro. Petals 0. Stamens 5 to many, episepalous, alternate with calyx-lobes. Ovary superior of 1 carpel, 1-cell, apex truncate or depressed around the single style. Capsule membranous or coriacous. Seeds 2 to many.