Hemiepiphytic; stem appressed-climbing, growing to 2.5-6 m high in trees; internodes matte to weakly glossy, 3-6(15) cm long, 1.5-3 cm diam., dark green, drying gray (within 4-6 internodes), epidermis drying light brown, semiglossy, often peeling (underlying stem blackened), fissured transversely, longitudinally ridged; cataphylls soft (especially near base),12-33 cm long, bluntly to sharply 2-ribbed or sharply 1-ribbed to near the apex then 2-ribbed below, green, sometimes tinged red, deciduous, persisting deciduous, intact; LEAVES: petioles 17-54 cm long, 5-10 mm diam., subterete, somewhat spongy, dark green, weakly flattened toward apex with an obscure medial rib adaxially, with adaxial margins rounded to weakly angular, surface weakly glossy, drying blackened; sheathing 3-9 cm long; blades deeply 3-lobed, subcoriaceous, moderately to conspicuously bicolorous, 30-48 cm long, 20-48 cm wide (1-1.5 times longer than wide), (0.8-1.8 times longer than petioles), upper surface dark green, drying dark gray to dark brown, semiglossy, lower surface drying dark yellow-brown to dark gray-brown, weakly glossy, moderately paler; anterior lobe 28-39 cm long, 8.5-14(17) cm wide (1.8-1.9 times longer than lateral lobes), rarely broadest at the base, usually narrowed toward the base (4-12 cm wide just above the base); sinus arcuate to broadly V-shaped; lateral lobes (7.5)15-22(27) cm long, 3-8(12) cm wide, broadest usually toward the apex, directed outward, broadly spreading (90 -127º angle), broadly confluent with medial lobe 3.3-6.5 (rarely to 14) cm, acute; midrib broadly convex to flat-sunken above, convex, slightly paler than surface, drying blackened below; basal veins 8-10 per side, pinnately arranged along a stout medial rib; posterior rib not at all naked or rarely naked for 1-1.5 cm; primary lateral veins 5-6 per side (45-75º angle on median lobe), gradually curved to the margins, sunken above, convex, drying blackened below; interprimary veins weakly raised and darker than surface below; minor veins distinct, darker than surface below, arising from both the midrib and primary lateral veins. INFLORESCENCES 1-3 per axil; peduncle (4.5)9-11(15) cm long; spathe (11)13-18 cm long, 8-10 mm diam. (1.4-1.6(2.4) times longer than peduncles), greenish white outside, greenish white to white within; spathe opening broadly at anthesis, convolute in only lower one-half of tube, barely or not at all constricted above the tube; spathe blade sometimes tinged white outside; spathe tube light green, sometimes tinged maroon at base outside, spadix held erect, not protruded forward, oblong to oblong-tapered, rounded to bluntly acute at apex, (9.5)11-15.5 cm long, broadest near the middle constricted weakly above sterile staminate portion; pistillate portion pale green, oblong to oblong-tapered, 4.5-5.7 cm long, 8-10 mm diam. at apex, 8-12 mm diam. at middle, (5)11-13 mm wide at base; staminate portion 8-11 cm long; fertile staminate portion oblong-tapered, 8-13 mm diam. at base, (6)12-13 mm diam. at middle, 8-9 mm diam. ca. 1 cm from apex, usually broader than the pistillate portion; sterile staminate portion ca. 1 cm diam.; pistils 1.5-3 mm long, 1.1-1.8 mm diam., ovary 7-10-locular, (0.8)1.1 mm diam., with sub-basal placentation; ovules 1(2) per locule, contained within transparent ovule sac, 0.6 mm long, usually shorter than funicle, style similar to style type B; style apex rounded; stigma button-like, subdiscoid, 1 mm diam., 0.2-0.4 mm high, covering center of style apex; thecae oblong to oblong-ovate, contiguous, sometimes divaricate. JUVENILE plants with petioles 8-10 cm long; blades, oblong, rounded to weakly subcordate.