Philodendron opacum Croat & Grayum

Ortiz, Orlando Oriel, de Stapf, María Sánchez, Baldini, Riccardo Maria & Croat, Thomas Bernard, 2019, Synopsis of aroids (Alismatales, Araceae) from Cerro Pirre (Darién Province, Panama), Check List 15 (4), pp. 651-689 : 680

Philodendron opacum Croat & Grayum ( Fig. 7E)

Material examined. Parque Nacional Darién, vicin- ity of Cerro Pirre base camp, along trail near E side of Río Paracida; 08°00′N, 077°48′W; 0–80 m; 1 Jul. 1988; T. B. Croat 68978 ( MO). Ibid.; T. B. Croat 68988 ( MO). Vicinity Cerro Pirre, along trail from base camp to Rancho Frío on slopes of Cerro Pirre; 07°58′N, 077°43′W; 200–450 m; 27 Jul. 1994; T. B. Croat 77131 ( MO). Ibid., 17 km S of El Real, along trail from base camp, along Río Perisenico; 08°01′N, 077°44′W; 100 m; 28 Jul. 1994; T. B. Croat 77180 ( MO). Parque Nacional del Darién, Estación Rancho Frío at N base of Cerro Pirre, ca 9 km S of El Real, along Quebrada Perisenico, in forest; 08°01′N, 077°44′W; 70–270 m; 8 Oct. 1987; B. E. Hammel 16157 ( MO). Ibid., trocha limitrofe al NO en la vecindad de la Estación Pirre; 08°00′N, 077°45′W; 150 m; 7 Oct. 1990; H. Herrera 692 ( MO, PMA). Ibid., en la trocha limitrofe entre el camino a Cerro Pirre y Balsas; 08°00′N, 077°45′W; 60–150 m; 12 Feb. 1991; H. Herrera 951 ( MO). Ibid., Cerro Pirre, Rancho Frío; 08°01′16″N, 077°44′04″W; 103 m; 13 Apr. 2016; O. O. Ortiz 2545 ( PMA). Ibid., orillas del río Perresenico; 08°01′11″N, 077°43′51″W; 110 m; 1 Dec. 2016; O. O. Ortiz 2700 ( PMA). Ibid.; O. O. Ortiz 2706 ( PMA).

Identification. This species is characterized by its nomadic vine life form (appressed-climbing habit), thickly sulcate and yellowish stems (when dry), erect petiole sheaths, non-cordate blades, usually matte or velvety above, uniformly greenish spathes, and straight to slightly curved seeds. On Cerro Pirre, the only species with which it could be confused is Philodendon sulca- tum K. Krause, because both species have thick sulcate and yellowish stems (when dry). The latter species differs from P. opacum in having unsheathed portion of the petioles generally <1 cm long, widely open horizontally winged petiole sheaths and semicochleate to cochleate seeds.

Distribution and ecology. Colombia, Costa Rica, Ecuador, Nicaragua, and Panama. On Cerro Pirre, P. opacum represents a common species and grows along semideciduous and evergreen forests, between 60 and 700 m.