Description from Flora of China
Plants perennial or annual, appressed strigose or villous. Leaves alternate. Cymes terminal, not branched or branched and paniculate, rarely 1-flowered. Fruiting pedicel erect or deflexed. Calyx 5-parted to base or nearly so; lobes vertical to reflexed, enlarged in fruit. Corolla blue, light blue, or light purple, rarely yellow or white, campanulate-rotate to campanulate-tubular; throat with appendages, rarely appendages obscure or absent; lobes overlapping in bud, erect or divaricate at anthesis. Stamens included; anthers orbicular, ovate to oblong. Style and stigma solitary, usually not exceeding nutlets. Gynobase flattened-fastigiate or semiglobose to 1 mm, wider than tall at base. Nutlets 4, all or some developed, turbinate to ovoid or triangular-ovoid and dorsiventrally compressed; abaxially usually discoid, ribs or margin usually winged, dentate or with glochids.
About 50 species: mainly in Asia, a few in Europe and North America; 39 species in China.