Widely branching, rigidly scantent vine loosely draping tree trunks (or rarely terrestrial or epilithic), climbing to 2-9 m above ground, the branches ligneous, divergent or pendent, often leafless or with reduced leaves. Internodes 0.4-13.8 (-21.7) cm long, 0.4-0.9 (-1.2) cm wide, olive-green to brownish green or gray- green, matte to semiglossy, sparsely to moderately tuberculate or pustular, narrowly flattened on one side, drying yellowish to tan or dark brown, finely to coarsely sulcate, the epidermis brittle and sometimes excoriating on older stems; roots usually absent from distal nodes, rarely abundant, to ca. 1.5 mm in diameter when present, sometimes with prickly, ovoid terminal galls. LEAVES: Petiole (4.3-) 9.2-28.4 (-34.2+) cm long, P/L=(0.31-) 0.35-0.70 (-0.75+), sometimes tinged purplish (Bunting et al. 12319), weakly glossy, sparsely pustular, sheathed (81-) 83-93% to (more frequently) extensively sheathed, the sheath erect-spreading to involute, adnate or with the free portion prolonged to ca. ,1.0 (-2.0) mm; unsheathed portion of petiole (0.0-) 0.2-2.3 (-3.6) cm long, C-shaped, weakly flattened to shallowly and bluntly sulcate above. Lamina (15.6-) 18,7-47.2 (-54.7) cm long, 5.0-29.6 (-37.8) cm wide, L/W=(1.14-) 1.40-2,92 (-3.46; -5.43, juvenile leaves), IQI=(0-) 2-7 (-10), thinly chartaceous to subcoriaceous or (rarely) coriaceous, matte to senmiglossy above, matte to glossy below, virtually concolorous to moderately bicolored, broadly to narrowly ovate, narrowly (rarely broadly) elliptical, broadly or (rarely) narrowly deltate, to broadly or (rarely) narrowly lanceolate or oblanceolate (broadest at or below the middle, or very rarely somewhat above), acute to (more commonly) gradually to ± abruptly short- to ± long-acuminate apically [the acumen ca. (0.3-) 0.4-1.8 (-2.7) cm long], broadly cuneate or rounded to (rarely) subcordate, cordate (with the sinus to 1.1 cm deep) or truncate basally; midrib broadly sulcate above, narrowly convex to C-shaped below; primary lateral veins 11-22 (-29+) per side, 0.2-4.5 (-6.2) cm apart, sunken above, convex (and sometimes paler) below, usually with interprimaries; minor veins obscurely to distinctly visible and slightly darker below; abaxial laminar surface drying with the tertiary and reticulate veins prominulous and enclosing granular (or rarely nearly smooth, especially on larger leaves) areolae, rarely granular along the veins; white stitching absent or rare to (occasionally) abundant, usually along the larger veins and marginally; resin canals usually visible between tertiary veins; adaxial surface similar, but the reticulate veins usually less prominulous and sometimes obscure; white stitching rare to (usually) scattered or abundant, especially toward the base, often obliquely oriented; resin canals generally not evident. INFLORESCENCES typically paired, occasionally solitary, very rarely in 3's; cataphylls often present but ± quickly deciduous, (5.9-) 7.9-20.2 cm long, 0.5-1.2 (-1.9) cm wide, red or reddish, heavily reddish lineate or greenish lineate, narrowly to ± broadly lanceolate, rounded dorsally or (less commonly) subacutely 2-keeled; peduncle (0.4-) 0.9-4.3 cm long, P/S=(0.03-) 0.11-0.24, prominently and coarsely raised-whitish lineate or tuberculate; spathe at anthesis (9.4-) 13.0-20.2 (-22.0) cm long, 1.5-2.5 (-3.1) cm wide, coriaceous, externally glossy, green or yellow-green below and densely while- and/or pinkish lineate or speckled, cream-colored distally (the blade persistent-reflexed), often pinkish or reddish toward margins and at very base, internally greenish white or cream-colored to pinkish (rarely dull rose-red to reddish wine) proximally, whitish distally, open to base at female-receptive stage, closed and somewhat constricted over intermediate sterile region at male-receptive stage, becoming pale yellowish green toward fruit and ultimately deciduous; spathe drying uniformly and densely granular and finely striate/sulcate to coarsely white-lineate externally, internally sparsely to densely granular and coarsely striate, sometimes with abundant white stitching along the margins, with longitudinal secretory striations in basal half to 2/3 acumen of spathe (0.05-) 0.30-1.00 (-1.50) cm long. Stipe of spadix 0.3-1.5 cm long; spadix (8.5-) 10.3-18.1 cm long, the fertile male portion 0.45-0.90 (-1.05) cm wide, cream-white, slightly arched forward at female receptivity; apical sterile male zone (0.9-) 1.5-4.4 (-5.1) cm long; intermediate sterile male zone 0.3-0.9 cm long; fertile female portion of spadix 1.9-3.9 (-4.4) cm long (to 8.0+ cm in fruit), F/S=0.14-0.28 (-0.33), 0.4-1.1 (-1.4) cm wide (to 4.0+ cm in fruit), ochroleucous, sometimes described as "red-orange'' (Dodson 6620) or "orangish'' (Folsom & Mauseth 7820); fertile male flowers 1.0-1.8 (-2.2) mm long, 0.6-1.6 mm wide, irregularly polygonal, columnar to laterally compressed or slightly anvil-shaped; apical sterile male flowers 0.7-1.3 (-1.6) mm long, 0.6-1.2 (-1.4) mm wide, irregularly polygonal, columnar; intermediate sterile male flowers 1.3-1.9 (-2.1) mm long, (0.65-) 1.10-1.80 mm wide, ± lozenge-shaped, somewhat laterally compressed to narrowly anvil-shaped or nearly clavate, drying dark brown and appearing oil-rich distally, black proximally; female flowers 1.5-2.2 (-2.5) mm long, 0.6-1.1 (-1.4) mm wide, the stylar canals (3-) 4-5. INFRUCTESCENCES: Ripe fruits variously described as "green" (Bunting 2266), "orange'' (Croat 15149A, 25100), "anaranjado'' (Albert de Escobar et al. 1782), "bright tangerine-orange'' (Grayum 8593), "orangey-red'' (D. Smith 1090), or "red" (Madison 3840). Seeds 0.75-1.00 (-1.20) mm long, 0.15-0.25 (-0.30) mm wide, whitish, ± straight to slightly or strongly (to 90º) curved or bent, finely striate with the striae minutely and obscurely cancellate, drying stramineous or yellow-orange to brown, glossy.
Most frequently collected in Tropical Wet Forest and, particularly, Premontane Wet Forest life zones, but also occurs abundantly in Tropical Moist Forest, where it is probably the most common and characteristic species of subg. Pteromischum; also collected from Tropical Rain Forest, Premontane Rain Forest, Premontane Moist Forest, and Lower Montane Wet Forest, as well as five relatively arid life zones enumerated in the discussion below.