Description from Flora of China
Herbs annual or biennial, hispid and appressed pubescent, hairs discoid at base. Stems erect or prostrate. Leaves alternate, ovate to oblanceolate. Cymes bracteate. Flowers pedicellate. Calyx 5-parted; lobes lanceolate, not enlarged or slightly enlarged in fruit. Corolla rotate, blue or white; tube short; throat appendages 5, scalelike; lobes 5, overlapping in bud, apex obtuse. Filaments extremely short; anthers 5, inserted in corolla tube, included; anthers ovate, obtuse. Ovary 4-parted, valves free, each containing 1 anatropous ovule. Style short, not surpassing valves; stigma capitate. Gynobase flat. Nutlets 4, with cupular emergence adaxially, rounded abaxially, tuberculate, with an oblong, elliptic, or orbicular ringlike aperture; margin of aperture thickened, prominent, entire or sometimes finely dentate; attachment scar basal. Seeds usually not curved.
About five species: Afghanistan, China, India, Indonesia (Java, naturalized), Japan, Kazakhstan, Korea, Kyrgyzstan, Pakistan, Russia, Tajikistan, Turkmenistan, Uzbekistan, Vietnam; all five in China.