Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Epicalyx wanting (in our spp.); cal 5-lobed, persistent and enclosing the fr, the ten costae leading alternately to the lobes and sinuses; stamen-column bearing anthers at the top; carpels 5–15, each with a single pendulous ovule; mature mericarps each with a lower, indehiscent, 1-seeded portion and an upper, dehiscent portion that is often tipped with 1 or 2 erect or connivent or inflexed beaks; upper and lower parts of the mericarp set apart dorsally by a shoulder that is an extension and joining of 2 lateral ribs; herbs and small shrubs with mostly small fls solitary or fascicled in the axils or forming a terminal panicle. 150+, warm reg.