Herbs perennial, 13--35 cm tall. Stems arcuately erect, simple or branched, with black glandular stripes and tangled multicellular hairs. Leaves opposite on lower part, alternate on upper part; petiole 4--15 mm, narrowly winged; leaf blade ovate to rhomboid-ovate, 1.3--3.5 X 0.8--2.5 cm, pilose, black glandular striate, base rounded, truncate to short attenuate, apex acute to subobtuse. Pedicel recurved in fruit, 1--3 cm, densely pubescent. Flowers solitary, in axils of upper leaves. Calyx lobes ovate-lanceolate, ca. 7 mm, ciliate, sparsely pubescent, blackish glandular striate, apex long acuminate. Corolla yellow; tube 0.5--1 mm; lobes ovate or rhomboid-ovate, 5--8 X 3--5 mm, brown glandular striate. Filaments connate basally into a ca. 0.5 mm high ring, free parts 1.5--2.5 mm; anthers dorsifixed, opening by lateral slits. Ovary pubescent; style ca. 4.5 mm. Capsule subglobose, ca. 4 mm in diam. Fl. Apr-May.
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