K. Krause in Engl. & K. Krause, Pflanzenr. IV. 23Db (Heft 60): 65. 1913. TYPE: Panama. Canal Area: at Frijoles, 25--30 m, 9E10'N, 79E48'W, Pittier 3753 (holotype, US). Figures 297--299.
Usually hemiepiphytic; stem appressed-climbing, to 1.3 m long, sap reddish, sticky; internodes short, semiglossy, 2.5--4 cm diam., sometimes longer than broad, dark green; roots several per node, drying 2--4 mm diam., dark brown, semiglossy, sparsely scaly; cataphylls 18--20 cm long, sharply 1-ribbed to sharply 2-ribbed, green to whitish, drying light brown, persisting briefly more or less intact, eventually fibrous, sometimes persisting for a time, eventually deciduous; petioles erect-spreading, (23)34--70(79) cm long, 4--13 mm diam., terete to subterete, sometimes weakly flattened or with narrow flattened rib adaxially, sometimes weakly and narrowly sulcate at base, dark green, sometimes pink at base, surface sparsely to densely pale greenish striate or striate-lineate, minutely grooved upon drying, geniculum to 6.5 cm long, sheath 1--4 cm long, usually inconspicuous, to 10 cm long when subtending an inflorescense; blades broadly triangular-ovate or more infrequently ovate, subcoriaceous, semiglossy, moderately bicolorous, abruptly acuminate, sometimes acute at apex (the acumen sometimes inrolled, to 4 mm long), deeply cordate at base, 32--72 cm long, 24--38 cm wide (1.2--2.3 times longer than wide, averaging 1.5), ((0.3)0.7--1.4 times longer than petiole, averaging 1.07), broadest near point of petiole attachment; upper surface dark green and glossy, drying semiglossy, dark gray-brown to olive-green, often somewhat blackened, lower surface slighty paler, semiglossy; margins sometimes broadly undulate; anterior lobe 25--41(58) cm long, (15)20--36(41) cm wide (1.9--4 times longer than posterior lobes); posterior lobes 7.5--18 cm long, 4.5--17.7 cm wide, rounded to broadly rounded to broadly obtuse; sinus hippocrepiform to parabolic (arcuate on younger blades), 4--12 cm deep; midrib broadly sunken, concolorous or paler than surface above, weakly asperous, thicker than broad, matte, sometimes short-white-striate, darker than surface below; basal veins 5--8 per side, with 1 free to base or nearly so, third and higher order veins coalesced 4--7 cm long; posterior rib naked for 2--3 cm long; primary lateral veins 4--7 per side, departing midrib at a 55--65E angle, spreading to a 65--75E angle, usually curved down gradually before merging with the midrib, narrowly sunken, concolorous or paler than surface above, convex, matte, slightly darker than surface below; interprimary veins narrowly sunken above; minor veins distinct, darker than surface below, arising from both the midrib and primary lateral veins; secretory ducts moderately visible on lower dried surface, alternating with minor veins.
INFLORESCENCES more or less erect, 4(6) per axil; peduncle (4.5)6.5--20 (most more than 15) cm long, 4--12 mm diam., pale green, strongly white lineate, slightly to moderately bent just below the spathe; spathe 10.5--18.5 cm long, (0.6--1.7(2.7) times longer than peduncle), acute at apex; spathe blade white outside, (opening 4--7.5 cm wide), pale green, moderately glossy to pale-punctate inside; spathe tube ellipsoid, medium green, densely pale-speckled outside, 6--9 cm long, to 4.5 cm diam., pale green, moderately glossy to pale-punctate inside, spadix sessile; protruding forward at anthesis, 12--16 cm long, broadest at upper two-thirds constricted to ca. 1.5 cm diam. between sterile staminate portion and fertile staminate portion; pistillate portion pale green, cylindrical, 3--6.5 cm long in front, 2.7--3.6 cm long in back, 1.3--1.7 mm diam. at apex, 1.3--1.9 mm diam. at middle, 1.1--1.5 mm wide at base; staminate portion 10.5--14.7 cm long; fertile staminate portion creamy white, more or less clavate, 1.5--1.8 cm diam. at base, 1.3--2 cm diam. at middle, 9--12 mm diam. ca. 1 cm from apex, about as broad as the pistillate portion; sterile staminate portion 1--1.9 cm diam.; pistils 2.1--3.4 mm long, 1--1.6 mm diam.; ovary 6(7)-locular,1.5--3.1 mm long, 1--1.6 mm diam., with axile placentation, walls sometimes embedded with granular, crystal-like particles; locules 1.5--3 mm long, 0.5--0.7 mm diam.; ovules 20--31 per locule, 2-seriate, 0.3 mm long; funicle 0.2 mm long, adnate to lower part of partition, style 0.5--0.6 mm long, 1.3--1.6 mm diam., similar to style type B; style apex rounded or domed; stigma truncate, hemispheroid, 1--1.3 mm diam., 0.3--0.5 mm high, covering entire style apex; the androecium truncate, prismatic, oblong, margins acutely and regularly 4--6-sided, 0.9--1 mm long, 0.7--2.2 mm diam. at apex; thecae oblong to cylindrical, 0.3--0.5 mm wide, more or less parallel to one another, contiguous; sterile staminate flowers bluntly, irregularly 4--6-sided, 1.9--4.1 mm long, 1.1--2 mm wide. INFRUCTESCENCE with seeds many per berry, white, narrowly cylindrical, 1.3 mm long, sticky. JUVENILE petioles terete, sheathing broadly, for 1/2 to 3/4 its petiole length, acute to rounded, eventually weakly to strongly cordate; blades broadest at the middle.
Flowering in Philodendron panamense occurs during the dry season and early rainy season (March through May), with post-anthesis inflorescences collected from May through August and immature fruits from July through November.
Philodendron panamense is endemic to Panama, but it is likely to occur also in adjacent Colombia. In Panama, it occurs in Tropical moist forest on both slopes of the Canal Zone, and Premontane wet forest and Tropical wet forest in Panamá, Colón, and Darién Provinces, at sea level to 800 m elevation (but mostly below 300 meters).
Philodendron panamense is a member of P. sect. Philodendron subsect. Philodendron ser. Fibrosa. Philodendron panamense is characterized by its appressed-climbing hemiepiphytic habit, short internodes, weakly one-ribbed, mostly deciduous cataphylls (sometimes persisting intact or as fibers), terete, pale-striate petioles, usually broadly triangular-ovate, moderately thin blades with parabolic to hippocrepiform sinus, and by the long-pedunculate spathes with externally greenish tube and white blade (greenish white throughout within). Also characteristic is the peduncle, which is often bent abruptly just beneath the spathe.
This species is most easily confused with P. lazorii, which has similar greenish inflorescences. The latter species differs in having more broadly ovate blades (0.97--1.4 times longer than wide and averaging 1.1 times) matte on the lower surface. In contrast, the blades of P. panamense are usually ovate-triangular, 1.3 or more times longer than broad (averaging 1.5 times longer) with the lower surface semiglossy. In addition, the peduncles of P. lazorii are proportionately shorter and usually shorter than the spathe (versus often longer than the spathe in P. panamense).
Philodendron panamense has been confused with P. jodavisianum, which has leaves drying a similar, somewhat blackened color. The latter species differs, however, in having D- to U-shaped petioles, typically with a medial rib adaxially, as well as more typically persistent cataphyll fibers and much shorter peduncles (typically less than 10 cm long in P. jodavisianum, versus typically more than 10 cm long in P. panamense). In addition, the peduncles of P. jodavisianum are usually straight, not bent.
A collection from the Serranía del Pirre at Cana, Croat 37600, is unusual in having several persistent cataphylls and shorter-than-usual peduncles.
Collections from Cerro Sapo and Cerro Pirre, (Croat 55184 and 68951 respectively), differ from typical material of P. panamense in having ovate (rather than triangular ovate) leaves and more short-pedunculate inflorescences. In addition, they have sharply two-ribbed cataphylls that persist intact (in the case of Croat 55184, on plants in the living collection at MO) or semi-intact (Croat 68951, collected in the wild on Cerro Pirre). Most dried collections of P. panamense have no cataphylls and longer peduncles.
Earlier (Croat, 1978), the species was reported to be much more widely distributed (to Honduras and Ecuador) but collections from outside of Panama have since proven to be misidentified (most now P. jodavisianum).
Additional specimens examined.
PANAMA. Canal Area: Barro Colorado Island, Croat 5101 (MO); 5530 (MO); 5840 (F, MO, SCZ); 6188 (MO); 8819 (MO, PMA); 8993 (MO); 9292 (MO, PMA, SCZ); 10083 (MO), SCZ); 10264 (MO, SCZ, US); 10819 (MO); 10894 (MO); 11016 (MO); 14876 (MO); Bailey & Bailey 199 (BH); Parque Nacional Soberania, Pipeline Road, N of Gamboa, Luteyn & Foster 1556 (MO); Río Macho bridge, 10 km NW of Gamboa, 115 m, Nee 7869 (MO, US); 6 mi. N of Gamboa, Río Mendoza, 9E11'N, 79E46'W, Croat & Zhu 77084 (MO); Summit Gardens, Croat 10867 (F, MO). Colón: Portobelo--Nombre de Dios, 0.5 mi. beyond junction of road to Isla Grande, 9E40'N, 79E35'W, Croat 49804 (MO); near Nuevo Tonosí, <100 m, Croat 33517 (MO, RSA). Darién: Cerro Sapo, Croat 55184 (AAU, K, MEXU, MO, PMA, US); ca. 5 km S of Garachiné, Río San Antonio, 130 m, 7E59'N, 78E25'W, Hammel et al. 1481 (MO); Cerro Pirre region, NW of Cana, 600 m, Sullivan 672 (MO); vic. of gold mine at Cana, 500--600 m, Croat 37600 (MO); Serranía Sapo above Casa Vieja along boundary trail of Darién National park, 150--300 m, 7E58'N, 78E23'W, McPherson et al. 15359 (COL, F, MO, NY, PMA), 550--830 m, 15378 (MO, US); Parque Nacional Darién, vic. of Cerro Pirre base camp, trail E side of Río Paracida, 0--80 m, 8EN, 77E48'W, Croat 68991 (CM, L, MEXU, MO, PMA, US); Estación Rancho Frío, at N base of Cerro Pirre, ca. 9 km S of El Real, 70--270 m, 8E01'N, 77E44'W, Hammel et al. 16131 (MO); Cerro Pirre, 800--1050 m, 7E56'N, 77E45'W, Croat 68951 (CAS, COL, MO, NY, PMA); Río Tuquesa, ca. 2 km air distance from Continental Divide, vic. of Tyler Kittredge gold mine, Croat 27193 (MO); Parque Nacional Cerro Pirre, Río Perisenico, 110 m, 8E01'N, 77E44'W, Croat & Zhu 77100 (CAS, CM, F, MO). Panamá: road to Cerro Azul, Mile 5, Croat 11515 (F, MO, PMA); 720 m, 9E04'N, 79E29'W, Croat 75152 (CM, MO); Cerro Campana, Dwyer et al. 4848 (MO), Croat 12074 (MO, SCZ).