Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Fls covering all or most of the slender spadix; spathe elongate, oblong, convolute below and covering the pistillate fls, opening distally and exposing the staminate ones; perianth none; ovary unilocular, subtended by a few white staminodia; ovules 1–few; stamens 4–5, embedded in a sterile ovary; perennial from thick fibrous roots, with long-petioled, basal, 3-nerved, pinnately veined lvs and a long scape bearing a slender, green or greenish spathe. 2, Atlantic N. Amer.