Description from Flora of China
Herbs perennial or biennial, rarely annual. Leaves usually basal and stem, entire; basal and lower stem leaves usually long petiolate. Cymes terminal or axillary, crowded or often dichotomously branched spreading panicles, bracteate or ebracteate. Flowers pedicellate. Calyx 5-parted to base, enlarged in fruit; lobes reflexed or spreading. Corolla usually blue, rarely white, dark purplish red, blackish purple or yellow-green, campanulate, tubular or funnelform, 5-parted; tube ± shorter than calyx; throat appendages 5, ± square, trapeziform or lunate, depressed at apex; lobes ovate to orbicular. Stamens included, inserted at middle or above in corolla tube; anthers ovoid or oblong. Style filiform, terete or somewhat tetragonous; stigma capitate, not exserted; ovary 4-parted; ovule anatropous. Gynobase fastigiate to conical. Nutlets 4, ovoid to subglobose, with glochids, attachment scar subapical.
About 75 species: cosmopolitan, primarily in Africa, Asia, and Europe, 12 species in China.