Herbs; stems erect or ascending, rarely creeping. Leaves opposite, the mar-gins undulate, crenate or entire. Inflorescences in terminal or axillary spikes, the flowers borne in the axils of conspicuous, imbricate bracts. Flowers with the calyx 5-merous, the segments subequal; corolla funnelform with a narrow tube, the tube straight or slightly curved, the limb spreading, the 5 lobes convolute in bud; stamens 4, didynamous, the filaments inserted at or below the mouth, the anthers 2-celled, blunt at the base, staminodes none; stigma bilobate, the lower lobe often inconspicuous. Capsules elliptic, seeds 6-12.