Cal campanulate, 15-nerved, slightly oblique at the throat, the lobes triangular, acute, the lower 2 slightly shorter than the upper 3; cor large, the tube very slender at base, distended distally, especially on the lower side, the upper lip 2-lobed, the lower slightly larger, more deeply 3-lobed, villous; stamens 4, ascending under the upper lip and about equaling it, the upper pair slightly the longer; pollen-sacs parallel or nearly so; trailing perennial herbs with handsome blue fls in a terminal, leafy, secund spike. 2, the other in e. Asia.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.