Herbs perennial, glabrous, 15--60 cm tall. Stems erect, weakly angular, usually simple, minutely brownish glandular at apex. Leaves alternate, evenly distributed on stem; petiole 0.5--1.5 cm, ± decurrent at base; leaf blade ovate to narrowly ovate or elliptic, (2.5--)4--9 X 2.5--3.5 cm, base short attenuate, apex acuminate; veins 4 or 5 pairs, raised abaxially. Pedicel nodding in fruit, ca. as long as to shorter than petioles, ± glandular. Flowers solitary, in axils of upper leaves. Calyx 0.9--1.2 cm; lobes lanceolate, widest at middle, 2.5--3 mm wide, apex acuminate. Corolla yellow, 0.9--1.3(--1.6) cm, ca. as long as to slightly longer than calyx; tube ca. 1 mm; lobes lanceolate to narrowly oblong, 4--6 mm wide. Filaments connate basally into a ca. 1 mm high ring, fused with corolla, free parts ca. 1 mm; anthers ca. 4 mm, basifixed, opening by apical pores. Capsule globose, 6--7 mm in diam. Fl. May-Jun. 2n = 18, 30.
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