Herbs perennial, glabrous, 40--70 cm tall. Stems erect, quadrangular, usually simple. Leaves opposite, rarely alternate in upper part of stems; petiole 5--10 mm, narrowly winged; leaf blade ovate to ovate-lanceolate, 8--11 X 2.5--3.5 cm, sparsely dark purple or black glandular punctate and striate near margin, base attenuate, margin obscurely undulate, apex acuminate. Racemes terminal; peduncle and pedicels with scattered raised glands; bracts linear, 3--4.5 mm. Pedicel 7--9 mm, slightly thickened toward apex. Calyx lobes triangular-lanceolate, 3--3.5 mm, ciliolate, brown glandular striate outside, apex subobtuse, ± recurved. Corolla white, 5--5.5 mm, parted ca. to middle; lobes suborbicular to subflabellate, red glandular punctate, apex erose-denticulate. Stamens included; filaments adnate to base of corolla lobes, free parts ca. 1 mm; anthers elliptic, dorsifixed, 1--1.5 mm, apex red glandular. Ovary glabrous; style ca. 2 mm. Capsule subglobose, ca. 2.5 mm in diam. Fl. May.
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