Erect or diffuse, glabrous or villose, ± suffrutescent, occasionally armed herbs of wet or marshy habitats. Leaves opposite, sessile to subsessile, entire. Flowers sessile, bluish-purple or white in axillary cymose fascicles or terminal dense heads or spikes; bracts leafy, ellipitc or linear-lanceolate; bracteoles lineal subulate. Calyx 4-5-lobed almost to the middle, the lobes linear or lanceolate, slightly unequal, valvate. Corolla glabrous, tube uniformly cylindrical, some what ampliate near the mouth, the limb bilabiate, upper lip erect, concave, shorter than lower, shallowly 2-lobed or emarginate, the lower lip patent, shallowly 3-lobed. Stamens 4, didynamous, all fertile or 2 fertile and 2 staminodes attached at the throat, exserted, filaments basally dilated and connate in pairs anthers oblong, dithecous, thecae equal, parallel, muticous. Ovary oblong-cylindric, 2-loculed, ovules (2-) 4-8 (-18) in each locule; style filiform, hairy recurved at tip with simple stigma. Capsule oblong-cylindric, not stipitate, (4-) 8-16 (-36)-seeded. Seeds compressed, oblique-ovate or orbicular, on hook-like funicles, hairy.