Description from Flora of China
Herbs annual or perennial, erect, with latex, without stolons. Leaves alternate, membranous. Cymes thyrsoid or corymbose, terminal. Flowers blue or bluish. Sepals narrowly acuminate, usually without glands. Corolla blue or bluish, salverform; tube cylindric, dilated above middle, villous inside; lobes overlapping to left. Stamens inserted inside dilated portion of corolla tube; anthers ovate or oblong, free from pistil head, base rounded. Carpels united by a filiform style; ovules numerous, biseriate on each placenta. Pistil head with a basal membranous appendage. Follicles 2, cylindric-fusiform, erect. Seeds cylindric, end obliquely truncate; coma absent.
About 20 species: North America, SE Asia; one species in China.