Description from Flora of China
Herbs perennial, biennial, or rarely annual. Stems single or several and cespitose, erect to diffuse, hispid or pilose, rarely glabrous. Cymes solitary or dichotomously branched, ebracteate or lower pedicels bracteate, rarely all bracteate (flowers extra-axillary). Calyx 5-lobed or 5-parted, not enlarged or slightly enlarged in fruit. Corolla blue or white; tube usually shorter than calyx; throat appendages 4, lunate or trapeziform; lobes 5, spreading, overlapping. Stamens included; anthers oblong to elliptic. Ovary 4-parted. Style linear, usually shorter than corolla tube; stigma included, capitate. Gynobase flat. Nutlets 4, semiglobose-tetrahedral or subulate trigonous-tetrahedral, shiny, glabrous or pubescent, rarely tuberculate, adaxial 3 surfaces subequal in size or bottom smaller than 2 lateral surfaces, longitudinal vein at juncture of 2 lateral surfaces, sessile or with a short carpophore from corner of 3 adaxial surfaces, abaxial surfaces flattened or convex, acute or obtuse ribbed, rarely narrow winged; attachment scar at bottom of carpophore or at corner of 3 adaxial surfaces when sessile. Embryo vertical; cotyledon ovate.
About 58 species: Asia, E Europe; 39 species in China, of which 34 are endemic.