Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Fls regular or slightly irregular; tep essentially alike, spreading, separate, sessile or short-clawed, 3–7-nerved; stamens 6, hypogynous; filaments filiform, elongate; anthers linear-oblong, introrse, versatile; ovules numerous; style solitary, slender, the stigma 3-lobed; fr a loculicidal capsule with few to several seeds; perennial from coated bulbs, with several linear basal lvs, an erect scape, and a loose, terminal, bracteate raceme of showy white to blue or violet fls. 5, N. Amer.