Cal deeply 4-5-parted, the 2 lobes of the lower lip longer than the 2 or 3 of the upper; cor tubular, nearly regular, the lobes much shorter than the tube, the upper lobe about equaling the lateral ones and wider than the lower one; stamens 2, inserted below the middle of the cor-tube, long-exsert; pollen-sacs parallel; style slender, about equaling the stamens; stigma 1, minute; fr narrowly ovoid or ellipsoid, not flattened, opening by 4 short terminal slits; tall perennials with narrow whorled lvs and slender terminal spikes of pink or white fls. 2, the other closely related, in e. Asia.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.