Climbing or vining herb, glabrous. Stem grey or drying blackish, quadrangular. Petioles 3-12 mm, canaliculate; blade herbaceous to chartaceous, ovate-oblong, 6-11 x 2.2-5.5 cm, acute or long acuminate at apex, acute and contracted at base, glabrous on both surfaces, margin subentire or repand; primary veins and secondary veins (5-9 pairs) slightly raised on both surfaces, veinlets prominent; cystoliths numerous and conspicuous, especially on upper surface. Inflorescence terminal, sometimes axillary panicles; peduncle 1.5-5 cm long; rachis sharply quadrangular, 3-10 cm long; basal branchlets 1-2 cm long, once or twice dichasially branched, bracts leaf-like, other bracts narrow, subulate, 1.5-4.5 x 0.5 mm, floral bracts subulate, 1.5 x 0.5 mm; pedicels 2-3 mm long, minutely and inconspicuously puberulent. Calyx green or brownish-purple, tube subglabrous, 1.5 x 2.5 mm, lobes subulate, 5-6 x 1 mm, minutely puberulous; corolla red, 50-70 mm long, tube curved inwards, 2-3.5 mm in diam. at base, apically somewhat contracted, 8-9 mm wide, puberulous towards base, lips 10-14 mm long, upper lip deeply 2-lobed, lobes triangular, ovate, 5 x 3 mm, spurred at base, lower lip 3-lobed, lobes narrowly ovate, 13 x 4 mm; stamens exserted 13 mm beyond mouth of corolla tube, filaments glabrous, connate from base to 25 mm, free part 11.5 and 13 mm long respectively, anthers yellow, 3 mm long; disk entire, 0.7-1 mm high; ovary with 3-4 ovules per locule, 3.5-5 mm high, glandular puberulent, style red, sparingly puberulous, 50-60 mm long, slightly exceeding stamens, stigma 2-lobed, upper lobe 0.6 mm, lower 2 mm long. Capsule unknown.