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 or pistillate; cal persistent, 5- lobed to the middle, the segments usually keeled, incurved over the ovary; stamens 5; ovary flattened, discoid; styles (2)3; cal at maturity developing below its lobes a continuous, horizontal, erose or toothed, membranous wing; fr plano-convex, horizontal, black, puberulent, the pericarp free from the seed; embryo annular; densely branched annual tumbleweed with pale green lvs and slender, few-fld, terminal, interrupted spikes of minute green fls subtended by minute bracts; fr often turning purple. Monospecific.