Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Fls perfect; tep 6, distinct, narrow; stamens 6, inserted at the base of the perianth; filaments slender; anthers oblong, laterally dehiscent; ovary superior, 2–3-locular, with 2 or more ovules per locule; style long and slender; stigma obscurely lobed; fr a berry with few–several seeds; rhizomatous herbs with 2–5 ample basal lvs, the bases of which sheathe a lfless erect scape bearing a determinate umbel of showy fls. 6, N. Amer. and e. Asia.