Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Freely branched, 2–7 dm; lvs shining, broadly deltoid, twice or thrice pinnately dissected into narrow acute segments; umbels 2–5 cm wide; rays 10–20; pedicels numerous, 1–5 mm; fr rather acute, 3 × 2 mm; 2n=20. Native of Eurasia, established as a weed here and there from N.S. and Me. to Pa. and O. June–Sept.