Herbs perennial, 40--80 cm tall, with creeping rhizomes. Stems erect, stout, simple or weakly branched, glabrous basally, viscid-pubescent apically. Leaves opposite or in whorls of 3 or 4, very short petiolate or sessile, elliptic-lanceolate to linear-lanceolate, 4--12 X 0.5--4 cm, abaxially glabrous except for glandular puberulent midvein, sparsely black glandular punctate, adaxially glabrescent, base obtuse to subrounded, apex acute to acuminate; veins usually more than 10 pairs; veinlets prominent. Panicles terminal and axillary; bracts linear, densely glandular puberulous. Pedicel 7--12 mm. Calyx lobes triangular, ca. 3.5 mm, margin black glandular striate. Corolla bright yellow, ca. 8 mm, deeply parted; lobes oblong, adaxially densely glandular, apex rounded. Filaments connate basally into a ca. 1.5 mm high ring, free parts 2--3 mm, densely glandular; anthers oblong-ovate, dorsifixed, opening by lateral slits, ca. 1 mm. Ovary ovoid; style 4--5 mm. Capsule subglobose, 2--4 mm in diam. Fl. Jun-Aug. 2n = 24, 42.
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