Herbs, annual, biennial, or perennial. Stems ascending to erect. Leaves opposite, rarely verticillate, sometimes forming a basal rosette, sessile or short-petiolate. Inflorescence axillary or terminal, 1-few-flowered cymes, sometimes in terminal clusters and/or axillary whorls. Flowers (4- or) 5-merous; calyx lobes filiform to ovate; corolla tubular, salverform, funnelform, obconic or urceolate; tube usually much longer than lobes; with appendages (plicaes) between lobes; stamens inserted on corolla tube; filaments basely winged or not; anthers free or rarely contiguous; glands 5-10 at ovary base; pistil sessile or on a long gynophore; style usually short, linear, less often long and filiform; stigma bilobed, lobes free or connate, usually oblong to linear, spirally recurved at bloom. Capsule cylindric to ellipsoid and wingless or narrowly obovoid to obovoid and winged, many seeded. Seeds wingless or winged, seedcoat minutely reticulate, rugose, simply areolate, or with complex spongy areolation.
About 360 species: NW Africa (Morocco), America, Asia, E Australia, Europe. Eleven species and two varieties distributed in Taiwan.