Erect or ascending herbs or shrubs with opposite, entire, undulate or ± crenate leaves. Flowers blue or yellow, infundibuliform, in terminal or axillary short spikes or heads, rarely solitary; bracts large, ovate or lanceolate, imbricated, 4-ranked; bracteoles present or absent. Calyx deeply 5-lobed, lobes linear lanceolate, ± equal. Corolla tube narrow, straight or slightly incurred, limb subequally 5-lobed, lobes obtuse, twisted in bud. Stamens 4, all fertile, didynamous, almost included, anthers dithecous, muticous; staminodes absent. Ovary 2-loculed, each locale 3-10-ovuled; style filiform, stigma unequally 2-lobed. Capsule linear or linear-oblong, 6-20-seeded, stipe absent. Seeds compressed, discoid, brown with white margins.