Perennial herbs from scaly rhizomes; stems usually erect. Leaves opposite, nearly equal in a pair, the base not oblique, entire or toothed; petiolate. In-florescences of single flowers in the axils of the leaves or arranged opposite in a pair on racemes in the axils of reduced leaves. Flowers showy; floral tube often elongate, narrow, grooved; calyx 5-lobed; corolla white, blue, lavender, rose pink, tubular, funnelform to campanulate, erect or oblique in the calyx, the limb of 5 nearly equal lobes; fertile stamens 4, the filaments often coiling after anthesis, the anthers coherent by their apices; disc absent or annular when present; ovary inferior. Fruit an elongated capsule; seeds numerous.
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