Herbs 0.8-1.5 m tall, perennial, isophyllous. Stems black, 4-angled, apically sulcate, glabrous. Petiole 1.3-2.5 cm, glabrous; leaf blade oblong-elliptic, 15-25 × 6.5-11 cm, both surfaces glabrous and with prominent cystoliths, abaxially paler and with prominent veins covered with cystoliths, secondary veins 6-9 on each side of midvein, base cuneate, margin serrate, apex acuminate. Inflorescences terminal, spikes, 15-25 cm, branched or rarely unbranched; rachis densely pilose with large-celled trichomes; bracts ovate-oblong, 8-12 × ca. 4 mm, persistent, pilose with large-celled trichomes and some gland-tipped trichomes; bracteoles lanceolate, 9-13 × 1.1-1.3 mm, persistent, pilose with large-celled trichomes and some gland-tipped trichomes. Flowers opposite pairs, sessile, 0.8-2 cm apart on rachis. Calyx 14-18 × 1-1.5 mm, persistent, pilose with large-celled trichomes, some trichomes gland-tipped. Corolla white, 3-3.5 cm, outside glabrous except for lobe margin, inside glabrous except for trichomes retaining style; tube basally cylindric and narrow for 1-1.5 cm then gradually ventricose and strongly bent 1.5-2.5 cm from base; lobes ovate, ca. 4 × 5 mm, apex obtuse. Stamens 4, included; filaments glabrous, shorter pairs 2-3 mm, longer pairs 3-5 mm; anther thecae oblong, 3-4 × ca. 1 mm, glabrous; pollen type 9. Ovary ca. 3 × 1 mm, glabrous; style ca. 2.5 cm. Capsule oblong, 1.5-2 × 0.2-0.3 cm, narrowed at both ends, comose, 4-seeded. Seeds ovate to suborbicular in outline, ca. 3 × 3 mm, pilose. Fl. Apr-Jun.
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