Cal tubular to campanulate, 2-lipped, 10-15-nerved, the upper lip entire to 3-lobed, the lower deeply 2-lobed; cor 2-lipped, the upper lip straight or arched, often subgaleate, the lower 3-lobed; stamens 2, ascending under the upper lip and sometimes surpassing it; filaments short; connective much elongate, attached at or near its middle to the filament, bearing a single pollen-sac (half anther) at the upper end, the lower end either sterile or with an imperfect half-anther; ours herbs, the medium-sized to large fls in verticils subtended by usually much reduced bracteal lvs, forming a terminal, sometimes interrupted, spike-like infl. 500, cosmop.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.