Annual or perennial herbs, spreading, viscid. Leaves opposite, petiolate, lamina entire or shallowly lobed, rounded. Inflorescence a terminal raceme, few–many-flowered; calyx 5-lobed, tube split to the base on the lower side, viscid pubescent; corolla cream to red-purple, tubular, expanded into the 5-lobed limb, lobes rounded, unequal; fertile stamens 4; stigma of 2 flattened lobes. Capsule rough (not spiny), crested on the dorsal side and extended at the apex into 2 long horns.
9 species, in the warm tropical Americas; 2 species naturalised in Australia.