Cor rather small, ±salverform, white, the well developed fornices sometimes yellow; stamens included; nutlets tending to be keeled on the back, and with a well developed ventral keel; scar generally elevated and caruncle-like, mostly small, lateral to virtually basal, placed at the lower end of the ventral keel, or sometimes extending along the keel; gynobase short and broad to pyramidal; narrow-lvd annuals or sometimes perennials, with the fls in a series of sympodial, helicoid, naked or irregularly bracteate, elongating false racemes or spikes. 50, mostly w. N. Amer.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.