Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Fr broadly ovoid, flattened laterally, barely constricted at the commissure; ribs 5 per mericarp, prominent, often undulate; oil-tubes very small and numerous; carpophore entire; umbels numerous, mostly terminal, often 2–4 together from the uppermost node of the stem; bracts few, ovate to lanceolate; rays numerous; bractlets like the bracts but smaller; sep none; pet white; stylopodium depressed-conic; biennials with large, pinnately decompound lvs. 4, temp. Eurasia, S. Afr.