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; stamens 6, free from the perianth; filaments broad and flat, at least at base, the anthers oblong, versatile; ovary superior; style and stigma trigonous; capsule loculicidal, obtusely trigonous, with ± numerous seeds in each locule; perennial herbs from a poisonous, coated bulb, with linear basal lvs, an erect or ascending scape, and a bracteate raceme of white fls. 150, temp. Old World.