Small, erect, pale green, annual herb, 10-30 cm high; stem and branches glabrous, acutely 4-angled, spreading from base; leaves opposite, 3-8 cm long, lanceolate acute or acuminate at apex, minutely scabrid on margins, glabrous, membranous; petiole slender, 3-6 cm; stipular glands subulate; flowers solitary or in pairs in upper axils, white, about 1 cm across, pedicels very short, white; calyx of 5 segments, filiform; corolla tube rotate or cylindric, white; 5-lobed, flat, wheel shaped, lobes obovate, throat constricted, mouth narrow, pilose inside; stamens 5, inserted near the top of inflated tube, filaments short, anthers oblong; disk 2, oblong glands; carpels 2, apocarpous, ovary with many ovules, marginal placenta; style filiform; stigma depressed or capitate, annulate, viscid; fruits folicles, 3-8 cm long, very slender, membranous, glabrous, straight, diverging; seeds black, muricately ribbed, linear-oblong, rounded at both ends.