Herb 40-75 cm tall. Stem unbranched, deeply sulcate decumbent at base, sparingly pubescent becoming glabrescent with age. Petiole 2-5 mm long; blade decreasing in size towards apex, rather firm, elliptic, 10-16 x 3-5 cm, caudate-acuminate at apex, acute or slightly attenuate at base, glabrous, margin sinuate or undulate, puberulous; primary veins and secondary veins (6-8 pairs) conspicuous, not connected to intermarginal veins, pubescent; cystoliths conspicuous under a lens. Inflorescence axillary or terminal, alternate or opposite, pedunculate; flowers dense or lax on once or twice dichasially branched, 9-13 cm long peduncles, glabrous or sparingly and inconspicuously puberulous, subquadrangular, canaliculate; basal bracts linear, to 25 x 2.5 mm, glabrous to sparingly puberulous, cystoliths prominent under a lens; pedicel of central flower 1-2 mm long; bracteoles subulate, 1.5-2 x 0.4-0.5 mm, glabrous, margin ciliolate. Calyx lobes green, linear, 8-9 x 0.5-1 mm, sparingly glandular pubescent, trichomes pilose and gland-tipped, densely covered with cystoliths, these conspicuous under a lens; corolla white with lavender streaks to lilac or violet, pale mauve or bluish, pubescent without, especially on upper part of tube, 30-35 mm long, tube erect, cylindrical, 15 mm long, 1 mm broad at base, throat obconic, 10-13 x 8-11 mm, limb suberect, lobes obovate, 7-8 x 5.5 mm, glabrous, retuse at apex; stamens included, filaments sparsely hirtellous, 3 and 5 mm long, anthers 1.6 mm long, connective conspicuously glandular pubescent; ovary 2.5 mm high, adpressed puberulous, gray at apex, style white, rose-violet at apex, 25 mm long, sparsely hirtellous at base, lower stigma lobe 1.2 mm long. Capsule tinged with red at apex, clavate, 11 x 3-3.5 x 2 mm, puberulous, stipe 5 mm long, valves 3-4-seeded, dorsally sulcate; seeds dark brown, 2 mm in diam., margin erose.
Guianas present, Southern America: Brazil North (Amapá present, Pará present)
The Guianas and Brazil (Amapá, Pará); 105 collections studied of which 100 from the Guianas (GU: 2; SU: 35; FG: 63).