Annual, dichotomously branching herbs. Leaves opposite, exstipulate. Flowers herm-aphrodite, in loose, corymbose or paniculate dichasia. Calyx herbaceous, many-nerved, prominently 5-ribbed, accrescent and becoming 5-winged in fruit; teeth 5. Petals 5, generally purple, clawed, without coronal scales. Stamens 10. Ovary borne on a short carpophore, 1-celled, slightly 2-celled at base, many-ovuled. Styles 2, filiform. Capsule oblong to globular, dehiscent by 4 teeth. Seeds reniform or subspherical.