Cal minute or obsolete; cor funnelform, narrowly campanulate, or tubular, the 5 lobes subequal; stamens 3; stamens and style exsert; fr dry, 3- locular, the one locule fertile and 1-seeded, the other 2 empty; dichotomously forked, annual or biennial herbs with simple, mostly sessile lvs, the lower often connate; fls in cymose glomerules ending the branches. Our spp. much alike in aspect and habitat. 60, N. Hemisphere.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.