Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Fr oblong to suborbicular, strongly flattened dorsally, the lateral ribs with conspicuous flat wings, the others slender; carpophore bifid to the base; umbels compound, with several to many usually unequal rays; invol minute or none; umbellets densely many-fld; bractlets in ours conspicuous, all on the outer side of the umbellet, often connate; sep minute or none; pet yellow or white (or pinkish); stylopodium scarcely developed; acaulescent perennials from a vertical thickened root, with several pinnately or ternate-pinnately decompound basal lvs, rarely also a lf near the base of the scape. (Cogswellia) 70, w. and c. N. Amer.