Philodendron atratum Croat

Terrestrial, epiphyte or hemiepiphyte; stems less than 1 m long; internodes dark green and semiglossy, later gray-brown, short, 3-8 cm diam., 1-3 cm long, coarsely short-ribbed at apex; cataphylls 18.8-35 cm long, medium green, sharply 2-ribbed, marcescent then deciduous, drying with fragments of dark brown epidermis and pale fibers; petioles spongy, subterete, obtusely flattened adaxially, medium green, matte-subvelvety to semiglossy, dark green-lineate, obtusely ribbed adaxially, 2.2 cm diam. at apex, 2.8 cm diam. midway, drying 59.8-86.9 cm long, 0.9-1.7 cm diam., blackish brown; geniculum 1.5-3.2 cm long, drying slightly paler than petioles; preadult blades broadly ovate cordate to sagittate, to 34.3 cm long, 25.5 cm wide (averaging 30 x 22), the sinus ca. 3 cm deep, narrowly rounded at the apex; adult blades broadly ovate, 61.1-93.4 cm long, 41-68 cm wide (averaging 76 x 55), 1.30-1.49 (averaging 1.38) times longer than broad, 0.7-1.4 (averaging 1.0) times longer than petioles, abruptly acuminate at apex (acumen to 1.7 cm), broadest above petiole attachment, subcoriaceous, semiglossy, moderately bicolorous, dark green and semiglossy to matte-subvelvety above, moderately paler and weakly glossy below, drying dark grayish black and glossy above, paler and semiglossy below; anterior lobe 46.3-72.2 cm long, the margins broadly rounded; posterior lobes 19.3-35.2 cm long, 15.8-27.6 cm wide, directed downward and inward; midrib broadly convex to flattened and slightly paler above, narrowly rounded, faintly dark-lineate and concolorous below, drying darker above and below; primary lateral veins 5-6 per side, arising at a 60° angle near base then a 50° angle near apex, weakly and obtusely sunken, slightly paler above, thickly convex and slightly paler below, drying darker above and below; minor veins moderately obscure, arising mostly from midrib but also from the primary lateral veins closer to margins, drying obscure above and distinct below; laticifers long and discontinuous, weakly raised appearing like minor veins; basal veins 7(8) pairs, the 1st pair free to the base, 2nd pair fused to 2-2.5 cm, the 3rd and 4th pair fused to 2.4-5 cm; posterior rib gradually curved, naked 1.5-2.5 cm; sinus spathulate, 13.3-21.9 cm deep, 5.4-16.8 cm wide.  INFLORESCENCES 4-5 per axil; peduncle 8.7-11.3 cm long, 0.9-1.7 cm diam. midway, pale green, whitish at base, pale-striate, drying black-brown; spathe medium green, semiglossy, faintly pale short-lineate, open face paler, tinged violet-purple on outside, inner surface white and glossy on blade, heavily tinged violet-purple in tube, drying 14.9-18 cm long, 4.4-6.2 cm wide, reddish black-brown; tube 3.2-4.7 cm diam., constriction 2.5-3.0 cm, blade 2.6-2.9 cm diam.; spadix 17 cm long, drying 12.6-16.4 cm long, dark brown; pistillate portion 1.3-2.3 cm long in front, 2.2-3.1 cm long in back, 12 mm diam. at middle; staminate portion 10.6-11.5 cm long, 1-1.2 cm diam., gradually tapered; sterile staminate portion 5-8 mm long, 1.3-2.0 cm diam. toward apex, to 1.5 cm diam. at constriction; pistils 2.5-2.6 mm long, 1.5-1.7 mm diam.; style with margins rounded, slightly narrower than the stigma; stigma rounded, 15-1.6 mm diam., 0.1 mm thick, consisting of 5-6 irregular mounds around the periphery with a medial concavity, completely covered with stigmatic papillae; locules 5-6, 1 mm long, 0.2 mm diam.; ovules ca. 10 or more per locule; placentation axile, 0.1 mm long, the funicle about as long as the ovule.