Biennial-perennial, glabrous, erect herbs. Basal leaves in a rosette, cauline leaves opposite, loosely arranged. Inflorescence solitary, terminal. Flowers pedunculate, peduncle long, tetramerous, rarely pentamerous, bisexual, actinomorphic-zygomorphic, mostly campanulate-tubular. Calyx divided mostly up to the base, sometimes not forming a tube, not provided by an inner membrane. Corolla campanulate, sometimes tubular, variously coloured: blue, purple, violet, red, pink or white, plicae or subsidiary lobes of the corolla absent, throat fimbriate, fimbriae linear-lanceolate or filiform, entire, acute or obtuse, arising from a crown inserted near the corolla tube. Stamens corresponding to the number of and alternating with the petals. Anthers strictly versatile, with filaments running down approximately to the base of the tube. Nectaries present at the base of the corolla, two each on a petal lobe. Ovary superior, unilocular with numerous ovules and parietal placentation, sessile, stigmas 2, sessile or stipitate, capsule dehiscing septici-daily from apex. Seeds light to dark brown, ovoid or circular in shape, mostly smooth, rarely reticulate.