Erect, much branched, hispid herb, up to 28 cm long; leaves variable, lower opposite and upper alternate, sessile, cordate at base, lanceolate or ovate obtuse or subacute at apex, margins entire, bristly on both surfaces; flowers violet, in terminal or leaf opposed, 1-few flowered racemes, pedicels axillary, up to 2-4 cm long; calyx hispid, deeply 5-lobed, lanceolate, margin strongly ribbed, with conivent base, much enlarged in fruit; corolla campanulate, petals 5, twisted to left, a gland or depression near the base of each lobe, throat without scales; stamens 5, adnate to the corolla lobes, anthers elongate, lanceolate, convient in a cone, filament short, connectives hairy on back; ovary 4-celled; style terminal, filiform; stigma capitate, small; fruits ellipsoid or pyramidal, subtruncate at apex, 4 ribbed nutlets enclosed in persistent calyx; ovate oblong, white, smooth, obscurly margined, shining on back.