Description from Flora of China
Herbs perennial. Rhizome short, slender. Leaves mainly basal, cauline ones few, small; stipules small; leaf blade simple and trilobed or subtrifoliolate. Inflorescence a raceme or panicle, simple or sparsely branched; bracts small. Flowers small; hypanthium adnate to ovary at base. Sepals 5, usually petaloid. Petals 5, sometimes absent. Stamens 10, visible above corolla. Carpels 2, connate basally; ovary 1-loculed; placentation parietal; styles 2, slender, elongate. Fruit a capsule; carpels unequal, one ca. 1/2 as long as the other. Seeds few, black, small, smooth.
The two North American species are more closely related to each other than to either of the Asian species.
Three species: one in China, the Himalayas, and Japan and one each in E and W North America: one species in China.
(Authors: Pan Jintang; Douglas E. Soltis)