Herbs or subshrubs, 0.5-2 m tall, branched, anisophyllous. Stems 4-angled to subterete, sulcate, retrorsely pubescent. Petiole 3-10 mm, grooved, pubescent; leaf blade ovate-elliptic to rarely ovate, smaller of pair 1-4 × 0.5-2 cm and larger one 3-10.5 × 1.5-4.5 cm, glabrous, cystoliths prominent, whitish, and dense along veins, secondary veins 3-6 on each side of midvein, base attenuate and oblique, margin serrulate, apex acute. Inflorescences axillary, pedunculate heads, 3-or 4-flowered, sometimes forming small axillary panicles; peduncle 1-3 cm, simple or 3-furcate, pubescent, apically thickened; bracts broadly ovate to rarely obovate, 4-13 mm, caducous, abaxially subglabrous and densely covered with cystoliths, margin ciliate, apex acute; bracteoles linear, ca. 5 × 2 mm. Calyx 5-lobed almost to base; lobes linear to lanceolate, 6-7 mm, slightly unequal with one longer than others, pilose. Corolla purple, 3.5-4.3 cm, ventricose, outside pilose, inside glabrous except for trichomes retaining style; tube basally cylindric and ca. 2 mm wide for ca. 8 mm then gradually widened to ca. 1 cm at mouth; lobes ovate, ca. 4 mm, apex emarginate. Stamens 4, included; filaments glabrous; shorter filament pair ca. 2 mm, incurved; longer filament pair 7-8 mm, unequal, erect; anther thecae subspherical, ca. 1.3 mm in diam. Ovary gland-tipped pilose at tip; style 2.8-3.5 mm. Capsule 15-16 × 3-4 mm, oblong, apically gland-tipped pilose, 4-seeded. Seeds ovate in outline, ca. 2 × 2 mm, pubescent. Fl. Oct, fr. Dec.
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