Philodendron pleistoneurum Standl. & L.O. Williams, Ceiba 3. 109. (1952). Type: Costa Rica. Puntarenas: Esquinas Forest, 60 m, 27 Mar. 1951, Allen 6036 (holotype, EAP; isotypes GH, US).

Terrestrial; stem creeping over soil, 20–100 cm long, leaf scars obscured by cataphylls; internodes short, 1–4 cm long, 2.8 cm diam., usually broader than long, medium green, semiglossy, coarsely white-streaked at apex; roots more or less smooth, slender, elongate, 2–4 mm diam., few per node, descending; cataphylls moderately coriaceous, 16–22 cm long, sharply 2-ribbed, green to pale green or reddish or pinkish, drying brown to tan, persisting semi-intact or as fibers at lower nodes, acuminate at apex. Leaves arching to pendent; petioles 25.5–73 cm long, 10–12 mm diam., D-shaped, spreading, pale to medium green to reddish at base, with a medial rib adaxially, rounded abaxially, with adaxial margins erect, surface finely and weakly striate; sheathing 3.5–5.5 cm long; geniculum slightly thicker than petiole when apparent, 1.4–1.7 cm long, paler than petiole; blades broadly ovate-cordate, subcoriaceous, moderately bicolorous, acute to abruptly acuminate at apex (the acumen apiculate and downturned), cordate at base, 20–50 cm long, 15.5–36 cm wide (0.9–1.7 times longer than wide), (0.5–0.9 times the petiole length), broadest at or near the middle, margins broadly undulate, upper surface dark green, semiglossy to glossy, sometimes matte or subvelvety, drying brown to greenish brown, lower surface semiglossy, moderately paler, drying brown to greenish brown; anterior lobe 16–37 cm long, 15–38 cm wide (1.8–3.7 times longer than posterior lobes), broadest slightly above or at point of petiole attachment; posterior lobes 5.5–15.5 cm long, 7.4–18.6 cm wide, directed downward, usually held up somewhat at an angle from the midrib, rounded to obtuse; sinus parabolic to hippocrepiform, sometimes closed with lobes overlapping before being pressed; midrib concolorous, flat at base, becoming weakly sunken toward apex above, thicker than broad at base, becoming convexly raised, concolorous below; basal veins 8–10 per side, 1(2) free to base, several remaining coalesced 0.5–2(4) cm, prominently sunken above, convexly raised below; posterior rib usually not naked, sometimes briefly so at base; primary lateral veins (8-10)11–17 per side, departing midrib at a 20–30 degree angle, spreading to 50–70 degree angle, more or less straight to the margins, quilted-sunken and concolorous above, prominently convex, matte, and darker than surface below; interprimary veins about as conspicuous as primary lateral veins above, flat and darker than surface below; minor veins arising from both the midrib and primary lateral veins; tertiary veins distinct, weakly raised above, darker than surface below. Inflorescences erect, 2–4 per axil; peduncle 2.5–14 cm long, 5–8 mm diam., terete, green to reddish, white-lineate; spathe 6.6–11.8 cm long (0.6–2.5 times longer than peduncle), constricted more or less midway; spathe blade lanceolate, pinkish red, tinged green, pale green to white or green, short white lineate outside, 4–6 cm long, (opening broadly elliptic in face view, pinkish red to white, pale greenish white or pale green inside; spathe tube oblong-ellipsoid, dark reddish maroon to reddish purple to green, weakly short dark lineate outside, 2.5–4 cm long, 1.4–3.8 cm diam., pale green to greenish white to pinkish red inside; spadix sessile or very short stipitate; tapered, 6.6–11.8 cm long, broadest near the base; pistillate portion white, yellowish white (post-anthesis), slightly tapered toward the apex and base, (1.6)2–2.7 mm long, 9–11 mm diam. at apex, 1–1.5 cm diam. at middle, (6)10–11 mm wide at base, with 17–19; staminate portion 3.5–7.1 cm long; fertile staminate portion white, cylindrical to tapered, 7–10 mm diam. throughout, 1–1.5 cm diam. at base, 7–10 mm diam. at middle, 4–6 mm diam. ca. 1 cm from apex, narrower than the pistillate portion, as broad as the sterile portion; sterile staminate portion about as the pistillate portion, white, 1–1.5 cm diam.; pistils 1.8–2.3 mm long, 1.1–1.5 mm diam.; ovary (4)5–6-locular, 1.3–1.5 mm diam., locules 1–1.5 mm long, 0.4–0.6 mm diam., with axile placentation; ovules (7-10)16–22 per locule, arranged in series of 2, 0.2–0.4 mm long, longer than funicle, style similar to style type B; style apex more or less concave, sometimes weakly lobed; stigma subdiscoid, brushlike, lobed or unlobed, 0.9–1.4 mm diam., 0.2–0.5 mm high, covering center of style apex, depressed medially; the androecium truncate, margins irregularly 3–6-sided; thecae oblong, 0.2–0.3 mm wide; sterile staminate flowers blunt, margins irregularly elongate, 13–18 mm long, 9–13 mm wide. Berries creamy white, obovoid, apex truncate; seeds 20 per locule, 1.9 mm long, 0.2 mm diam., with prominent striations running from funicle to apex and slightly spiraling, perpendicular to larger veins. Juvenile blades narrowly elliptic to ovate, acute to weakly cordate at base.

Type: Panama. Colón: Río Fató (Pató) at Dos Bocas (E of Nombre de Dios), 40--80 m, ca. 9°35'N, 79°28'W, Pittier 4228 (holotype, US). Philodendron pleistoneurum Standl. & L.O. Williams, Ceiba 3. 109. (1952). Type: Costa Rica. Puntarenas: Esquinas Forest, 60 m, 27 Mar. 1951, Allen 6036 (holotype, EAP; isotypes GH, US).

Esmeraldas: Lita-San Lorenzo, 40.1 km W of Lita, 350 m, 0°56'N, 78°40'W, Croat 72308 (CM, MO); Carretera vecinal Herrera-Los Monos, Cabecera del Río Aguacatal, 550 m, 0°19'30"N, 79°46'6"W, Palacios 13670 (QCNE, MO); Lita-San Lorenzo Road, Río Piguambi, 6.4 km W of Río Lita Bridge (below Lita), 685 m, 0°52'4"N, 78°29'3"W, Croat et al. 82202 (MO); Lita-San Lorenzo Road, 5 km W of Río Lita Bridge (below Lita, on old road to San Lorenzo), 0°52'7"N, 78°27'43"W, Croat et al. 82277 (MO); Along Río Lita in vic. of Lita, 600-650 m, Croat 38948 (MO). <b>Losb> <b>Ríosb>: Río Palenque, along river after crossing Río Bimbe and Río Waija, 170 m, Dodson & Gentry 6519 (MO, S); Tinalandia (Hotel Tinalandai) 9.6 km E of Santo Domingo de los Colorados, S of hwy. to Aloag & Quito, above Río Toachi, 700 m, 0°16'N, 79°7'W, Croat 55731 (MO); Reserva ENDESA, about 8 km North of Km. 113 on Quito-Puerto Quito Highway, vicinity of Río Cabayales, 700 m, 0°5'N, 79°2'W, Croat & Rodríguez 61502 (MO); Reserva ENDESA, along San Miguel de los Bancos-Puerto Quito Road, NW of Quito, Km 113, 28.6 km E of Puerto Quito, 3.1 km E of Vincente Maldonado, 710 m, 0°3'N, 79°7'W, Croat 73148 (MO). Carchi: Reserva Indígena Awá, 1800 m, 1°2'N, 78°14'W, Rubio et al.1602 (MO, US). Imbabura: Río Mira Valley on border with Carchi Province, 750-775 m, Croat 38979 (MO).