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-oblong, slightly flattened laterally, tipped by the slender stylopodia, the ribs low and obtuse; oil-tubes 1–4 in the intervals, 2 on the commissure; carpophore bifid to the base; umbels compound, the rays ± unequal; invol none or of a single small bract; umbellets few-fld, the 0–3 bractlets minute, the pedicels very unequal; sep minute or obsolete; pet white; branching, glabrous herbs with trifoliolate lvs and numerous loose, irregular umbels arising terminally and from the upper axils. 4, the others Old World.