Erect, annual herb up to 60 cm tall, with straight, simple or branched, hairy stem. Leaves opposite, simple; stipules absent; petiole up to 3 mm long; blade circular to ovate or lanceolate, 1.5–5.5 cm × 1–3 cm, base cuneate, rounded or cordate, apex acute or obtuse, margin almost entire to coarsely toothed, rigid-hairy to almost glabrous. Flowers solitary in axils of upper leaves, bisexual, slightly zygomorphic, sessile or with pedicel up to 0.5(–1.5) mm long; bracteoles linear to filiform; calyx campanulate, 6–8 mm long, 10-veined, 5-lobed with triangular lobes 3–5 mm long; corolla campanulate, slightly longer than calyx, pale yellow to dull orange, sometimes with reddish veins, withering but not falling off; stamens 4, 2 longer ones with long-hairy filaments; ovary superior, glabrous, 2-celled, style clavate above the middle, recurved, included with stamens in corolla. Fruit a globose capsule c. 5.5 mm in diameter, glabrous, many-seeded. Seeds linear to clavate, small. |