Erect or ascending, rarely creeping perennial herbs. Stems more or less pubescent. Leaves opposite, petiolate; blades usually crenate or undulate, sometimes entire. Inflorescences terminal or axillary spikes with flowers borne in axils of conspicuous, opposite, imbricate bracts. Flowers sessile; calyx 5-lobed, lobes linear-subulate, ciliolate, slightly unequal in length; corolla usually lavender, white or purplish, tube slender, straight or slightly curved, somewhat enlarged above, limb subregular, and subequally 5-lobed, corolla lobes contorted in bud; stamens 4, didynamous, inserted at or below corolla throat, filaments united at base by a membrane, anthers 2-thecous, thecae equal, parallel, muticous at base, staminode 0; ovules 4-6 in each locule, stigma 2-lobed, posterior lobe often inconspicuous. Capsules fusiform, seminiferous from base, retinacula present, septae with retinacula remaining attached to inner wall of mature capsule; seeds 6-12, flat, pubescent.
Indomalaysia present, Old World present, S China present, gardens in Latin America cultivated, tropical Australia present
Old World genus of about 100 species in S China, Indomalaysia and tropical Australia; one species is cultivated in gardens in Latin America and occasionally found as an escape.