Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Fr oval to rotund, flattened laterally, somewhat constricted along the commissure; ribs 5 per mericarp, elevated; oil-tubes solitary in the intervals, 2 on the commissure; carpophore entire or not cleft beyond the middle; umbels terminal and lateral, compound, the lateral sometimes sessile; umbellets small; sep minute or none; pet white or greenish-white; stylopodium short-conic to depressed; lvs once pinnate to decompound. 10, widespread.