Stiffly erect, dark green annual, much branched, 20–50 cm high; stems 4-angled with a groove on each face, scabrous. Leaves opposite, linear to linear-lanceolate to lanceolate, 6–9 cm long, 1.1–1.5 cm wide, acute, margins entire, rather thick and leathery, both surfaces scabrous, margins with hispid hairs at regular intervals. Flowers opposite or subopposite, 8–10 open at same time per inflorescence branch, variable in size; bracts almost as long as the calyx with prominent hispid hairs on the margins, tip curved away from stem; bracteoles half the length of the calyx. Calyx 5-ribbed, 10–12 mm long, 2.5 mm wide, hispid on the ribs, intercostal portion whitish or pinkish and translucent, glabrous; lobes unequal, acuminate. Corolla bright pink (rarely white); tube 10–20 mm long, bent just above calyx teeth, outside with very scattered hairs, glandular-pubescent; upper lobe emarginate, erect, lower lobes 10–13 mm long, 8–10 mm wide. Capsule oblong, 12–15 mm long, 2–2.5 mm wide. Fig. 38: 4–6, p. 145.
