Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Sep and lateral pet similar, spreading, the pet projecting forward over the column; lip broadly obovate, with 3 low parallel ridges near the center, obliquely 3- cleft, its lateral lobes up curved, the terminal one dilated and upcurved at the margin; column slender, flattened, bearing a terminal anther with 4 pollinia; perennial from stout globose corms that produce in late summer a single lf that lasts ± throughout the winter, the same corm (in some individuals) producing an achlorophyllous, bracteate scape the following spring, after the lf has withered; fls in a loose terminal raceme. 2, the other Japanese.