Cal tubular, becoming flask-shaped, gibbous on the lower side at base, strongly 13-ribbed, 2-lipped, villous in the throat; cor weakly 2-lipped, the upper lip erect, emarginate, the lower spreading, 3-lobed; stamens 2, ascending under the upper cor-lip and about equaling it; nutlets ovoid, smooth; small annuals (our spp.) with numerous axillary, few-fld verticils of small, blue, pediceled fls. 38, New World.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.