Annual or perennial herbs or shrubs, sometimes climbing by means of foliar tendrils, rarely small trees. Leaves spirally arranged or opposite, exstipulate, sessile or petioled, entire or more or less deeply divided, or compound. Flowers axillary or terminal, solitary, geminate, corymbose or capitate, actinomorphic or slightly zygomorphic. Calyx 5-lobed or 5-partite, with or without transparent fields, persistent. Corolla gamophyllous, 5-lobed or 5-partite; lobes contorted in bud. Stamens 5, on the corolla-tube, inserted at equal or unequal height, alternating with the segments; filaments free from each other, included or exserted; anthers dorsifixed, 2-celled; cells opening longitudinally. Ovary superior, sessile on a disk, 3 (rarely 2)-celled; ovules in each cell 1-~, inserted in the inner angle; style 1, filiform, 3 (rarely 2)-fid. Fruit a loculicidal or septifragal capsule, rarely indehiscent. Endosperm mostly copious; embryo straight or slightly curved. Distr. N. America and the Andes, rare in the Old World, absent from Africa and Australia. Genera 12, represented by upwards of 250 species. In Malaysia one American genus is more or less naturalized; a few other species are cultivated in gardens.