broadest near the middle or at petiole attachment, sometimes weakly constricted at or about the petiole attachment; margins somewhat undulate; adaxial surface semiglossy, dark green, drying dull olive-green to grayish with the major veins usually drying much darker; abaxial surface paler than adaxially and matte, drying pale olive-green; anterior lobe 22.5–33 x 16–27 cm, 1.7–1.8x longer than posterior lobes; posterior lobes 12.5–18 x (6.3–)8–11.5 cm, narrowly rounded at apex, directed downward and outward; sinus hippocrepiform, 10–11.5 cm deep; major veins drying raised, concolorous with surface but with very dark margins adaxially, round-raised and darker than surface abaxially; midrib darker than surface, flat or slightly raised within deep valleys, marginally dark green adaxially, round-raised and thicker than broad abaxially; basal veins 3 per side, with 1 to 2 free to base, posterior rib highly branched, naked 2–3 cm; primary lateral veins 5 to 7 per side, 2.5–3.5 cm apart, departing midrib at 50º–60º angles, curving gradually out to margin, darker than blade and deeply quilted-sunken, dark green along the margin of the vein and otherwise medium to pale green adaxially, narrowly raised, matte and darker or paler than blade surface abaxially, those in the lower 1/2 of the blade branched 1 to 2x; interprimary veins nearly equal to primary lateral veins; tertiary veins obvious, especially abaxially, arising from basal veins and primary lateral veins; numerous cross veins obvious on both sides, darker than surface; basal veins 8 to 12 pairs, the 1st pair often free to the base, the remainder variously coalesced and branching off the 6 straight posterior rib, the 4 to 5 acroscopic pairs branched 1 to 2x before merging with the margin; cross veins usually prominulous even on fresh material; sinus narrowly obovate, naked along the posterior rib 3–5 cm. INFLORESCENCE 1 to 2 per axil; peduncle medium green, weakly glossy, 6–7 cm, 3.5–4 mm diam. on drying; spathe 12.5–13 x 2.1–2.3 cm on tube, moderately dark green and matte outside, paler and weakly glossy within; blade white on both surfaces; spadix 11.5–12 cm; staminate portion 6–6.5 cm, 1.3– 1.4 cm diam., drying ca. 7 mm diam. midway; sterile portion ca. 2.5 cm, ca. 1.5 cm diam. at base, ca. 1.5 cm diam. at apex; pistillate portion 4–5 cm, 1.4– 1.6 cm diam.; pistils pale yellow-green, 5- to 6- locular, 1.8–2 mm, 1.4–1.8 mm diam; placentation basal; ovules 8 to 10 per locule, ca. 0.15 mm, contained within an oblong opaque envelope, the envelope ca. 1 mm, attached at base of locule; funicle shorter than ovule; style irregularly 5- to 6-sided with rounded edges, minutely papillate, matte, drying bowl-shaped with 5 to 6 deep depressions, 0.5–0.7 mm wide; stigma consisting of 1 brush-like cluster for each locule, the entire width of the collective stigma 0.8–1 mm diam., drying flattened to saucer-shaped, irregularly angular, 1–1.5 mm diam. Berries not seen.
This species is a member of subgenus Philodendron, section Philodendron, subsection Achyropodium (Schott) Engl. in Mart. It is characterized by its terrestrial habit; scandent stems; cataphylls that are unribbed, pale green, and that weather to pale fibers; and ovate to triangular-ovate, bullate, markedly bicolorous blades that are deeply cordate with lobes directed downward and outward forming a hippocrepiform sinus. The venation is particularly striking because the major veins are pale green but are sunken in dark green valleys adaxially, and the primary lateral veins are prominently forked (hence the epithet ‘‘furcatum’’). Other unusual characteristics for the species are the peculiar branched styles emerging from each locule and the fact that the ovules are enclosed within a cylindroid envelope in each locule.
Philodendron furcatum was known only in sterile condition when the junior author finished her Ph.D. thesis, and it was listed as species #5 in her thesis. The type specimen was later found in flower.
The species is closest to another new species from western Ecuador in the provinces of Carchi (Madison & Besse 7024 from El Pailon, 45 km below Maldonado at 800 m) and Esmeraldas (Croat 83373 from the Lita–San Lorenzo rd., 13.2 km SE of El Durango at 735 m, as well as Croat 77233 and Croat et al. 82216 from the Río Chuchubí, 6.4 km W of Río Lita at 609 m). That species differs in having petioles conspicuously scaly near the apex and having the primary lateral veins scarcely or not at all branched between the midrib and the margin. In contrast, Philodendron furcatum has glabrous petioles and the primary lateral veins are markedly branched between the midrib and the margin. In addition, the primary lateral veins of P. furcatum are markedly discolored dark green along their borders, which is not the case with the other new species from Ecuador.