Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Perianth subrotate, the tep alike and spreading, retuse or abruptly aristulate, distinct or very shortly connate at base; filaments connate at least to the middle (to the top in our spp.); style-branches filiform, alternating with the stamens; capsule globose to obovoid, loculicidal; seeds black, globular, ± pitted; low, perennial, grass-like herbs, usually tufted from fibrous roots; lvs equitant, linear and mostly basal; scape-like stems 2-edged or 2- winged, simple or branched from the axils of lf-like bracts; fls delicate and fugacious, in umbel-like clusters from 2-valved spathes, blue to violet or pink, seldom white, rarely yellow, our spp. regularly with a yellow or greenish eye. Our spp. fl chiefly in May, but continue until Sept. 60±, New World.