Large herbs or shrubs, with cystoliths. Stems quadrangular and articulated. Leaves opposite, petiolate; blades elliptic to narrowly ovate, with numerous cylindrical cystoliths, margins entire or irregularly dentate. Inflorescences narrow, terminal and axillary, panicles, basal branchlets once or twice dichasially branched; bracts small, basal pair sometimes leaf-like; bracteoles none. Flowers homostylous, pedicellate; calyx campanulate, basally unequal and shortly 5-lobed or toothed; corolla tubular, slightly curved, limb short, 2-lipped, not spreading, upper lip 2-lobed, lobes contorted in buds; stamens 4, didynamous, inserted near apex of corolla tube, included in corolla tube or exserted from mouth of corolla, filaments united in pairs at base, anthers 2-thecous, thecae subequal to subparallel, obtuse at base, connective apiculate; disk annular, with distinct projections. Capsules clavate, retinacula present, septa with curved retinacula remaining attached to inner wall of mature capsule; seeds 6, homomorphic, flattened to lenticular.
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