Herbs annual. Roots containing a purple dye. Stems erect, branched from base, 10-30 cm tall, spreading long hispid; branches alternate or subopposite. Stem leaves sessile, linear-oblong to linear-lanceolate, 2-6 cm × 2-16 mm, sparsely hispid, apex obtuse. Calyx lobes linear, ca. 7 mm, to 1.2 cm in fruit, long hispid, short strigose, base extended and hardened, subtending nutlet. Corolla yellow, tubular-campanulate, 1-1.4 cm, pubescent outside; tube straight or slightly curved; limb 3-6 mm wide; lobes broadly ovate, subequal. Stamens spirally inserted at apex of corolla tube; anthers oblong, ca. 1 mm. Style filiform, nearly reaching throat, twice 2-cleft; stigma globose. Nutlets brown, triangular-ovoid, ca. 2 mm, densely tuberculate, adaxial center line prominent, abaxially convex, slightly wrinkled, apex nearly keeled. Fl. and fr. May-Jun. 2n = 8, 22.
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