Description from Flora of China
Herbs, perennial, rhizomatous, glabrous, with translucent ("pale") glands only. Leaves opposite, sessile or petiolate, entire; venation pinnate; glands punctiform only. Flowers bisexual, homostylous. Sepals 5, quincuncial, equal, free. Petals 5, imbricate, flesh-pink or white, ± symmetric, deciduous after anthesis. Stamens in 5 fascicles united to form apparently 3 (i.e., 2 + 2 + 1) with compound fascicles antisepalous, persistent, each fascicle with 3 stamens; filaments rather slender, 0.35-0.5 united; anthers small, dorsifixed, dehiscing longitudinally, with gland on connective; sterile fascicles (fasciclodes) 3, yellow to orange, inserted between stamen fascicles, persistent. Ovary 3-loculed with axile placentae, each placenta with numerous ovules; styles 3, free, ± slender; stigmas narrowly to scarcely capitate. Fruit a septicidal capsule, with valves longitudinally and prominently vittate. Seeds small, carinate; testa reticulate-foveolate, not arillate; embryo slender, straight, with distinct slender cotyledons.
Six species: one in NE India (Khasia Hills) and S China, one in NE China, Korea, Russia (Far East), and Japan, and four in E Canada and the E United States.
(Authors: Li Xiwen (李锡文 Li Hsi-wen); Norman K. B. Robson)