Herbs to 3 m tall, perennial, anisophyllous. Stems 4-angled, somewhat zigzag, sulcate, glabrous. Petiole 0.6-7 cm; leaf blade broadly ovate, ovate, ovate-elliptic, or rarely elliptic, smaller of pair 3.5-7 × 2-4 cm and larger one 10-19 × 4.5-11.5 cm, glabrous, densely covered with linear cystoliths especially along abaxial veins, secondary veins 4-7 on each side of midvein, reticulate veins conspicuous, base broadly cuneate and oblique, margin remotely dentate to rarely serrate, apex acute. Inflorescences axillary or terminal, spikes, 7-15(-26) cm, sometimes branched; peduncle 0.5-5.5 cm, glabrous; rachis 4-angled, strongly zigzag, sulcate, bifariously pubescent; bracts elliptic, 5-7 × ca. 4 mm, caducous, glabrous, margin ciliate, apex truncate to retuse; bracteoles yellowish but apically black, linear-lanceolate, ca. 8 × 1.5 mm, persistent, abaxially sparsely puberulent, margin ciliate, apex truncate to rounded. Flowers distant on rachis. Calyx yellowish with a black apex, 8-10 mm, sparsely pubescent, usually sparsely covered with cystoliths, 2-lipped, lower lip 2-lobed almost to base, upper lip 3-lobed; lobes lanceolate, 5-6 mm, margin apically ciliate. Corolla white, 3.5-4 cm, slightly curved, outside glabrous, inside glabrous except for trichomes retaining style; tube basally cylindric and ca. 4 mm wide for 1-1.5 cm then ± ventricose and gradually widened to ca. 2 cm at mouth; lobes ovate, ca. 7 × 5 mm, apex obtuse. Stamens 4, included; shorter filament pair ca. 3 mm, glabrous; longer filament pair ca. 7 mm, sparsely hirsute; anther thecae oblong, 3-4 × ca. 1.5 mm; pollen type 12. Ovary comose; style ca. 2.7 cm, sparsely hirsute. Capsule fusiform, ca. 1.7 cm, glabrous except at apex, 4-seeded. Seeds ovate in outline, ca. 3 × 2.5 mm, densely appressed pubescent. Fl. Oct-Dec, Apr.
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