Perennial, glabrous herb, stem branched, terete or quadrangular, internodes short; leaves sessile, linear or lanceolate-ovate, 3-nerved; flowers in axillary, sessile clusters; calyx deeply 5-lobed, segments narrowly oblong, obtuse, not keeled; corolla white, infundibuliform, lobes-5, elliptic, twisted to right, spreading; stamens 5, attached on upper part of the corolla tube; filaments shortly linear with minute scales at the base; anthers oblong, oblong, acute, included; ovary 1-celled, placenta not much protruded; style short, filiform; stigma capitate; capsules ellipsoid, carpels separating, glabrous; seeds many, small, subglobose reticulate.