Shrubby, much-branched, rigidly clambering plants, ascending to at least 10 m on tree trunks, the stems with prominent petiole scars; fertile branches divergent. Internodes (0.4-) 2.1-12.6 cm long, 0.3-0.8 (-1.1) cm wide, dark green to gray-green becoming brown, semiglossy or glossy to matte, drying stramineous to cafe-au-lait or mid-brown, costate, the epidermis slightly to moderately brittle and flaky; nodal roots occasionally seen on juvenile (and presumably appressed) shoots, to ca. 1.5 mm in diameter, sometimes bearing spiny galls. LEAVES: Petiole 5.6-13.6 cm long, P/L=(0.28-) 0.31-0.43 (-0.47), extensively sheathed, the sheath involute with the edges brownish, dry and cracking, the free portion prolonged apically by 1.5-2.5 (-5.0) mm (often beyond the lamina base); unsheathed portion of petiole obsolete or to 0.3 (-0.5) cm long. Lamina 13.4-32.2 cm long, 3.2-14.0 cm wide, L/W=(1.82-) 2.02-3.71 (-4.19), IQI=(4-) 7-13 (-19), thinly coriaceous to sub-coriaceous, semiglossy to glossy both sides, virtually concolorous to weakly ormoderately bicolored (young blades reddish) narrowly to broadly elliptical to lanceolate or oblanceolate (broadest near the middle to slightly above), gradually to abruptly ± long-acuminate (rarely short-acuminate) apically (the acumen 0.6-2.4 cm long), narrowly to broadly cuneate or (more rarely) truncate to rounded or subpandurate basally (often circulate at the petiole apex); midrib sunken above, convex below; primary lateral veins 10-14 per side, (0.2-) 1.0-3.4 cm apart, weakly sunken above, weakly convex below; minor veins weakly visible, slightly darker below; abaxial laminar surface drying virtually smooth to moderately and uniformly granular, with reticulate venation visible, though not conspicuous; white stitching occasional not conspicuous sometimes following resin canals; resin canals ± visible; adaxial surface relatively featureless, virtually smooth to sparingly or moderately granular with resin canals vaguely visible. INFLORESCENCES solitary, very rarely paired; cataphylls absent; peduncle (0.6-) 1.1-3.5 cm long (to 4.4+ cm in fruit), P/S=(0.10-) 0.16-0.27 (-0.31), subterete, pale short-lineate; spathe at anthesis 6.8-15.0 cm long, 1.4-3.6 (-4.1) cm wide, externally green and often whitish lineolate below, paler (greenish white to cream) distally, often with pale whitish spots, internally uniformly whitish; spathe drying densely and uniformly granular (rarely virtually smooth) externally, internally moderately granular (may appear reddish punctate), with longitudinal secretory striations ca. 1/2 to 3/4 to apex, abscising in fruit; acumen of spathe obsolete to more commonly 1.1-2.3 cm long. Stipe of spadix (0.3-) 0.6-1.3 cm long; spadix 5.9-12.3 cm long, the fertile male portion 0.6-1.2 cm wide cream-colored; sterile male zone 0.7-1.2 cm long; female portion of spadix 1.1-4.3 cm long (to 8.3+ cm in fruit), F/S= (0.19-) 0.24-0.38 (-0.42), 0.50-1.25 cm wide (to 2.1+ cm in fruit), pale green or yellowish; fertile male flowers 0.8-1.7 mm long, 0.6-2.0 mm wide, irregularly polygonal; sterile male flowers 1.2-2.3 mm long, 0.7-1.7 mm wide, cuboidal to clavate; female flowers 1.3-2.1 mm long, 0.5-0.9 mm wide, the stylar canals 4-5. INFRUCTESCENCES: Ripe fruits very pale yellowish orange (ochroleucous), emitting a pronounced garlicky odor at night (Grayum 8594). Seeds (0.7-) 0.9-1.0 mm long, ca. 0.2 mm wide, straight to some- what (or occasionally strongly) curved, twisted or spindled finely striate with the striae cancellate, drying light brown and semiglossy.
According to K. Thomsen (in litt. 1995), the roots of P. alliodorum (Thomsen 335) are occasionally used for basketry on the Osa Peninsula of Costa Rica. The fresh roots are soaked in water and their "bark'' is removed to yield the fibers.