Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Fr linear to narrowly clavate, slightly flattened laterally, the base prolonged (in our spp.) into bristly tails, the ribs slender, acute, ± appressed-bristly; oil-tubes obscure or none; carpophore bifid less than half length; fls white or greenish-white; umbels peduncled, terminal and lateral, usually surpassing the lvs, few-rayed, with or without invol; umbellets few-fld; sep obsolete; pet white; erect perennials from thickened roots; lvs twice ternately compound, the lower petiolate, the upper subsessile, the ultimate segments ovate to lanceolate, serrate or lobed. 11, N. Amer., Andes, and e. Asia. Our spp. are habitally similar, 4–8 dm, pubescent to subglabrous, with mostly 3–6 widely ascending to divaricate rays, each ray with 3–6 fertile pedicels to 15 mm, usually mixed with some sterile ones.