Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Sep 6, biseriate, ovate-elliptic; stamens 6; ovary ellipsoid; stigma sessile; fr a few-seeded berry; smooth perennial herbs with a thick rhizome, the flowering stem with 2 alternate lvs peltate near the margin, the basal lvs scattered, erect, with centrally peltate blade; fls in a pedunculate cyme, white. 3, the other 2 in e. Asia.