Erect, annual-perennial glabrous herbs. Basal leaves usually in rossettes, cauline opposite, loosely arranged, sessile. semiamplexicaule. Inflorescence solitary and terminal, usually long pedicelled. Flowers bisexual, zygomorphic, tetramerous. Calyx cylindric-campanulate, 4-lobed, lobes unequal, 2 larger lobes linear-lanceolate, acute-acuminate, 2 smaller lobes ovate-triangular, 4-triangular ciliated intracalycine membrane at the base of and alternate with lobes. Corolla 4-lobed, tube cylindric-campanulate, variously coloured: blue, purple, violet, reddish, pinkish or white, plicae or the subsidiary lobes of the corolla absent, naked inside i.e. without any ciliae or fimbriae inside corolla tube, margin of lobes ciliate or fimbriate, sometimes entire. Stamens corresponding the number of and alternating with petals. Anthers strictly versatile with filaments inserted at ± below half level of the corolla tube or sometimes near the bottom of the tube. Nectaries present at the base of corolla tube and opposing the petals, but never at the base of ovary. Ovary superior, unilocular with numerous ovules and parietal placentation, with a distinct gynophore, stigmas 2, enlarged, with a small style or style absent. Capsule stipitate, dehiscing into valves. Seeds elliptic to cylindric, densely papillose.