Perennial or rarely annual herbs, erect or prostrate, densely pubescent to glabrous. Leaves simple, opposite at least below or spirally arranged throughout, denticulate to serrulate or rarely entire, sometimes pubescent. Flowers in axillary racemes. Calyx of 4 free or basally fused equal sepals. Petals 4, notched at the apex or entire, equal, free or basally fused. Stamens 8, the episepalous ones longer. stigma 4-lobed, capitate or clavate. Capsules elongate, slender, 4-locular, locuicidal, pubescent or glabrous, pedicellate or subsessile. Seeds many, comose, foveolate or variously papillose. Chromosome number n = 12, 13, 15, 16, 18, 30, 36 (only n = 18 known for species from Pakistan).