Philodendron rigidifolium K.Krause

Lianas or scandent hemiepiphytes. Internodes 0.4-17.3 cm long, (0.4-) 0.6-1.3 cm wide dark green to tan or gray-brown, matte or weakly glossy, somewhat flattened on one side, drying yellowish tan to yellowish brown, pluricostate to coarsely sulcate, the epidermis sometimes flaking off; roots absent to solitary or few at distal nodes, 1.0-2.0 mm thick. LEAVES: Petiole (6.3-) 7.2-27.7 cm long, P/L=(0.45-) 0.47-0.88 (-0.95), the sheath spreading-erect to involute, sometimes dark-green-streaked, free apically and prolonged by (0.1-) 0.7-2.3 (-4.1) cm; unsheathed portion of petiole (0.0-) 0.2-5.4 cm long, subterete to D-shaped, flat to shallowly sulcate above, the margins obtuse. Lamina (12.3-) 14.6-33.9 cm long, (5.3-) 6.7-22.2 cm wide, L/W=(1.36-) 1.42-2.34 (-2.67), IQI=0-4 (-5), subcoriaceous to coriaceous, matte and velvety to semiglossy or glossy above, weakly glossy to semiglossy below, virtually concolorous to weakly bicolored, narrowly to broadly ovate, oblong, lanceolate, or broadly elliptical (broadest at or, usually, below the middle), abruptly acuminate apically (the acumen 0.7-2.3 cm long), broadly cuneate to truncate, rounded, subcordate, or cordate basally; midrib flat or weakly sunken above and paler (pale yellow-green), convex and somewhat paler below; primary lateral veins 5-8 (-9) per side, 0.15-3.60+ cm apart, very weakly sunken to sunken above (or scarcely apparent) and sometimes paler, very weakly convex to convex below and slightly paler (or obscure), with interprimaries usually visible especially proximally; minor veins visible below, darker, occasionally prominulous; abaxial laminar surface usually drying virtually featureless, often densely and minutely alveolate, rarely densely but obscurely granular (especially along veins, even coarsely so along midrib), with occasional to abundant reticulate veins, rarely with occasional to abundant white stitching or obvious resin canals or resiniferous punctations; adaxial surface similar. INFLORESCENCES erect, always solitary; cataphylls absent; peduncle 1.7-5.2 cm long, P/S=ca. 0.07-0.17, subterete, coarsely pale-striate-roughened; spathe at anthesis (15.9-) 19.3-29.0 (-33.6) cm long, 2.0-4.0 cm wide (broadest in expanded blade), externally weakly striate, green, matte to weakly glossy, pale-striate-roughened and sometimes appearing glaucous proximally, paler distally and almost matte, internally uniformly greenish white to pale green, persisting to fruit (including blade, which becomes reflexed); spathe drying relatively featureless to ± rugose and/or densely but obscurely granular externally, sometimes finely white-lineolate, internally obscurely to densely and conspicuously granular, with longitudinal secretory striations ca. 2/3 - 3/4 to apex; acumen of spathe (0.5-) 1.1-3.2 (-3.4) cm long. Stipe of spadix 0.3-0.9 cm long; spadix (13.0-) 15.6-24.6 (-27.0+) cm long, the fertile male portion 0.60-1.35 cm wide, white, persisting to fruit (and becoming brown); sterile male zone 0.25-0.90 (-1.20) cm long (sometimes obsolete or at least not obvious); female portion of spadix (3.1-) 4.0-6.1 cm long, F/S=(0.15-) 0.19-0.29 (-0.32), 1.0-2.0 (-2.3) cm wide, pale green; fertile male flowers 0.7-2.2 mm long, 0.6-2.7 (-3.1) mm wide, irregularly polygonal, columnar to laterally compressed; sterile male flowers 1.2-2.3 mm long, 0.7-2.5 mm wide, quadrangular and broad-based to obconical or anvil-shaped; female flowers 2.3-4.8 mm long, 0.7-2.0 mm wide, the stylar canals (4-) 5-6 (-7). INFRUCTESCENCES: Ripe fruits (subsp. rigidifolium) white (Croat 1978). Seeds (subsp. rigidifolium) 1.0-1.4 mm long, 0.2-0.3 mm wide, straight, somewhat spindled, very finely striate with the striae cancellate, drying brown to purplish brown and glossy.