Description from Flora of China
Shrubs erect or trailing. Leaves whorled, with axillary glands. Flowers large, in terminal or seemingly axillary corymbs. Calyx deeply divided, without basal glands. Corolla yellow, funnelform, narrow part with fringed scales, limb campanulate, lobes overlapping to left. Stamens inserted at narrow part of corolla; filaments very short; anthers narrowly oblong, base rounded, coherent with pistil head; disc cup-shaped, obscurely 5-lobed or entire, fleshy, thick. Ovary 1-loculed, with two parietal placentae; ovules numerous. Style filiform; pistil head thick, with a membranous, reflexed rim, apex conical, shortly 2-lobed. Capsules globose, glabrous, sharply spiny, 2-valved. Seeds numerous, imbricate, compressed, winged or with a membranous margin; radicle short.
Fourteen species: tropical America, two cultivated in China.