Annual herb (4.5–)8–30(–70) cm. tall, sometimes slender in habit but often coarse and appearing quite different; stems drying blackish purple, often with paler longitudinal lines, densely covered with spreading hairs, usually sparingly branched or unbranched. Leaf-blades lanceolate, 1.3–7 cm. long, 2–9 mm. wide, acute at the apex, narrowed at the base into the stipule-sheath, covered with long rather coarse hairs on both surfaces and also scabrid with shorter hairs near the margins; stipules with fimbriae crimson or red-brown in life but mostly blackish purple when dry; base 2 mm. long, with 5–7 fimbriae 3–8 mm. long, with long white hairs. Flowers in many-flowered verticillate clusters, mostly at the upper nodes which run together to form a dense coarse strobilate inflorescence 0.7–1.5 cm. wide, but usually with 1–2 clusters at the nodes beneath and well separated; bracteoles stipule-like, of 5–6 lanceolate fimbriae 5–6 mm. long, joined at the base, ciliate along the margins. Calyx-tube ellipsoid, 1.8 mm. long; lobes 2, lanceolate, 3 mm. long, 0.6 mm. wide at the base. Corolla white or with purplish tips to lobes outside or blue; tube very narrowly cylindrical, 9.5–12 mm. long; lobes narrowly elliptic or linear-oblong, 1.8–3 mm. long, 0.8–1.2 mm. wide, sparsely hairy outside. Filaments exserted ± 1–2 mm. Style exserted 1.2–2 mm.; stigma slightly bifid, 0.5 mm. wide. Capsule ellipsoid, 3–3.5 mm. long, 1.8–2 mm. wide, shortly hairy at the apex. Seeds chestnut-brown, semi-ellipsoid, 2.7 mm. long, 1.1–1.5 mm. wide, 0.9 mm. thick, shiny, flat and narrowly grooved ventrally, the groove opening out at each end, convex dorsally, rugulose. Fig. 49/5, p. 340.