Twinning or erect shrub, rarely under shrub with milky latex. Leaves whorled or opposite, rarely alternate above, glands present at the axil of petiole. Inflorescence few to many flowered cymes, axillary or terminal. Flowers showy, generally yellow or purple. Calyx 5-partite, lobes more or less free and unequal, lanceolate, acute, eglandular. Corolla funnel shaped, 5-lobed, convolute; tube inflated below the throat, appendages absent. Stamens 5, filament very short, included; anthers lanceolate, acuminate, basally shortly sagittate. Disc thick, annular, obscurely 5-lobed. Ovary uniloculor; ovules many; style filiform; stigma capitate. Fruit a capsule, globose or subglobose, spiny. Seeds winged, flat.