Description from Flora of China
Shrubs. Branches 4-sided, glabrous or slightly furfuraceous. Leaves opposite, petiolate; leaf blade both surfaces glabrous, secondary veins 2 on each side of midvein but marginal veins inconspicuous, margin entire. Inflorescences terminal, cymes, (1-)3-flowered. Flowers 4-merous. Hypanthium campanulate, acutely 4-angled, furfuraceous. Calyx lobes 4, lanceolate to shortly triangular. Petals 4, broadly obovate. Stamens 8, whorls unequal in length. Anthers of longer stamen lanceolate, apex beaked; connective basally extended adaxially into an inconspicuous spur bearing 2 long setae. Anthers of shorter stamen oblong, apex not beaked, 2-setose at base; connective slightly inflated. Ovary half inferior, pyriform, 4-sided, 4-celled, glabrous. Capsule oblong-globose, obtusely 4-sided, often furfuraceous, dehiscing into 4 valves. Seeds numerous, cuneiform, small.
The genus was revised by Hansen (Notes Roy. Bot. Gard. Edinburgh 38: 489-493. 1980), and his concept is followed here.
● One species: China.