Plants annual, biennial, or perennial, glabrous or white hairy, herbaceous. Leaves petiolate or sessile, subentire. Verticillasters axillary, 6-flowered; bracts ciliate-or awned-crenate. Pedicel erect, rigid, flattened. Calyx tubular, 15-veined, straight, throat closed after anthesis; teeth 5, subequal, posterior tooth wider than other teeth, tooth sinus with a thickened fold. Corolla with a slender, included to slightly exserted tube, dilated at apex into throat, 2-lipped; upper lip straight, slightly concave, apex emarginate, with 2 longitudinal folds inside; lower lip spreading, 3-lobed, middle lobe reniform, lateral lobes minute, semicircular. Stamens 4, posterior 2 longer; filaments pilose; anther cells 2, divaricate. Style apex 2-cleft, lobes subulate. Nutlets dark brown, oblong, adaxially ribbed, mucilaginous on wetting.
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