Perennial herb or undershrubs, erect to subspreading, often densely pubescent. Leaves opposite or subopposite, ovate to ovate-oblong, petiolate, usually dentate and coarsely veined, sub-pubescent. Inflorescence terminal, spicate, often elongated in fruit. Flowers sessile or subsessile, bracteate, usually white, zygomorphic, hermaphrodite. Calyx-tube 5-ribbed, obliquely truncate to minutely 5-toothed, pubescent, slightly enlarged below and splitting lengthwise outside in fruit. Corolla-tube exceeding the calyx, cylindrical; limb lobes 5, subequal, short, spreading. Stamens 4, didynamous, included, inserted above the middle of corolla-tube; anthers ovate, dithecous, subsessile or on very short filaments. Ovary 2-loculed with 1-2 ovules in each locule; style filiform, with somewhat oblique, sub-bilobed stigma. Fruit dry, enclosed within the persistent calyx, separating into 2, oblong, glabrous, smooth pyrenes.