Herbs, perennial, terrestrial or epipetric, stoloniferous. Stems simple or branched. Leaves few to many, along stem, opposite, equal to subequal in a pair; leaf blade glabrous to pilose, base attenuate to cuneate, rarely rounded. Inflorescences umbel-like, dense, axillary or pseudoterminal, 1-to many-flowered cymes; bracts 2, opposite, connate, forming a globose to ovoid involucre. Calyx actinomorphic, 5-sect from base, 2-lipped, or 5-lobed from middle or above; segments equal, rarely unequal. Corolla white to pink, purple, or yellow, zygomorphic, inside usually with a ring of hairs; tube funnelform-tubular, not swollen, longer than limb, 0.7-2 cm in diam.; limb 2-lipped; adaxial lip 2-lobed, shorter than to nearly as long as abaxial lip; abaxial lip 3-lobed, lobes equal or subequal, apex rounded. Stamens 2, adnate to abaxial side of corolla tube below middle, included; anthers basifixed, coherent apically or adaxially, thecae parallel, not confluent at apex, dehiscing longitudinally; connective not projecting; staminodes 2 or 3, adnate to adaxial side of corolla tube. Disc ringlike. Ovary linear to linear-lanceolate, 2-loculed, only adaxial locule fertile; placenta 1, axile. Stigma 1, terminal, truncate to obtuse or capitate, undivided. Capsule straight or oblique in relation to pedicel, usually narrowly lanceolate, somewhat curved, much longer than calyx, dehiscing loculicidally to base only adaxially; valves 2, straight, not twisted. Seeds unappendaged.
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