Herbs perennial. Rhizomes creeping, rooting from nodes. Roots slightly fleshy. Stems usually erect, simple. Proximal leaves scalelike, distal ones few to several, alternate, membranous. Racemes spreading, 1--4-flowered; peduncle axillary, slender; bracteoles small, scalelike. Flowers small. Stamens inserted at base of perianth segments; filaments thick; anthers dorsifixed, arched; connective not appendaged. Ovary superior, ovoid, compressed; ovules few, apically attached to placenta, pendent. Stigma capitate. Capsule ovoid, valvate. Seeds subglobose, longitudinally ribbed; funicle bearded.

Wu Zhengyi (editor’s note) believes that Croomia, together with Stichoneuron J. D. Hooker (from SE Asia), are more primitive and should be treated in the segregate family Croomiaceae, as was done by Takhtajan (Diversity Classific. Fl. Pl. 519. 1997).

Three species: China, Japan; E North America; one species in China.