A large, strong liane reaching 30 m. or more in the crowns of trees, or a scrambling shrub, with light ochraceous thick corky bark and plentiful milky latex. Stems flexuose, at first usually reddish-brown or greyish puberulous with a mixture of simple and branched hairs, later glabrescent with conspicuous whitish dot-like lenticels. Leaves membranous, drying ± concolorous green; petiole 5–10 mm. long, puberulous; 2 minute oblong or triangular glands present on upper leaf surface at proximal end of midrib; lamina 6·2–13 x 2–5 cm., narrowly obovate or obovate-oblong, the apex cuspidate-acuminate, the base rounded to acute; upper leaf surface glabrous, with major nerves both raised and channelled; lower surface glabrous (except for domatia), with all nerves raised; domatia (dense tufts of hispid hairs) present on lower leaf surface in the angles between lateral nerves and midrib, and also sometimes where lateral nerves meet. Venation: lateral nerves few (2–5 on each side), at an acute angle to the midrib; tertiary veins scalariform, ± at right angles to the midrib. Panicles axillary, many-flowered, loose; flowers greenish. Calyx 2–3 mm. long, lobes shortly connate at base, imbricate, elliptic, puberulous. Corolla tube c. 3 mm. long, barrel-shaped, pubescent externally, densely pilose internally except for a narrow glabrous band at base and apex, the hairs pointing downward; 5 small triangular scales present at mouth, one in each sinus between the petal lobes. Corolla lobes 3–5 mm. long, narrowly linear, ± glabrous. Stamens inserted almost at base of corolla tube; filaments short; anthers large (2–2·75 mm. long), reaching almost to mouth of corolla tube, each comprising a sagittate sterile structure bearing the anther thecae on its inner side on the upper half, the five anthers lightly connate by their margins into a tube round the gynoecium. Five square scales present on the receptacle centripetal to and alternating with stamens, reaching half-way up the ovary. Ovary of 2 ± free carpels c. 0·5 mm. long; style ± absent; clavuncle fusiform, style of 2 short fleshy lobes. Fruit a divaricate pair of follicles, each up to 25 cm. long and 1·3 cm. in diameter, narrowly cylindrical, tapering at both ends, brown-pubescent outside, smooth, glabrous and yellow within, splitting longitudinally at maturity, containing ¥ seeds. Seed c. 14 x 2·5 mm., narrowly ellipsoidal, strongly compressed, with apical coma of fine white simple hairs up to 3 cm. long.