Description from Flora of China
Herbs perennial, with horizontal rhizomes. Leaves opposite, usually 2- or 4-crowded apically on stem. Inflorescence terminal, an umbellate or corymbose cyme, few flowered; involucres and bracts deciduous or occasionally persistent. Sterile flowers small, borne at margin of inflorescence. Fertile flowers large. Calyx tube hemispheric to turbinate, adnate to ovary; lobes 5, imbricate in bud, petaloid, persistent. Petals 5-8, imbricate in bud. Stamens inserted on periphery of disc; filaments slender; anthers basifixed, broadly ellipsoid. Ovary semi-inferior; placentation parietal; ovules numerous. Styles 5, connate or apex 6-fissured; stigmas small. Fruit a capsule, semi-inferior, dehiscing between valves. Seeds numerous, small, winged at both ends.
Two species: China, Japan; one species (endemic) in China.
(Authors: Wei Zhaofen ( Wei Chao-fen); Bruce Bartholomew)