Description from Flora of China
Herbs perennial, erect, fibrous rooted. Stems terete, glabrous proximally to finely pubescent and widely branched distally. Leaves alternate, shortly petiolate; leaf blade lanceolate or narrowly so, thin, apex long acuminate. Flowers numerous, arranged in terminal and axillary, scorpioid (or corymblike) cymes, bisexual, yellow-green, small. Sepals 5(-8). Petals 5(-8) or absent. Stamens 10(-16), in 2 whorls. Carpels 5(-8), connate near base; ovules many; styles short. Capsule 5(-8)-lobed; carpels rostrate at apex. Seeds many, small.
Recent studies have demonstrated that Penthorum is not part of Saxifragaceae, but is actually most closely related to Haloragaceae.
Two morphologically very similar species: one in E Asia, the other in E North America; one species in China.
(Authors: Pan Jintang ; Douglas E. Soltis)