Herbs. Leaves whorled below, alternate above, narrow, sessile, entire. Flowers in terminal spikes. Calyx deeply 5-lobed. Corolla 2-lipped: tube with a basal spur; upper lip 3-lobed with a prominent basal palate; lower lip 2-lobed. Stamens 4, didynamous. Ovary with many ovules in each loculus. Fruit a capsule, opening by 4-10 apical valves. Seeds winged.