Arum tripartitum Jacq., hort. Schonbr. 2: 33, t. 190. (1797). Illustration Plate 190 Caladium tripartitum (Jacq.) Willd., Sp. Pl. 4: 491. 1805. Caladium trifoliatum Desf., Tabl. Ecole Bot. ed. 3, p. 386. (1829). Type: [not seen]. Philodendron fenzlii Engl. in Mart., Fl. Bras. 3(2): 144. (1878). Type: Mexico. Schott Drawing 2599 Philodendron affine Hemsl., Diagn. Pl. Nov. Mexic.: 37. (1879). Type: Guatemala, Barranca Honda, Volcán de Fuego, Salvin (K). Philodendron tripartitum var. tricuspidatum Engl. in Mart., Fl. Bras. 3(2): 144. (1878). Type: Costa Rica, at San José, 1300 m, May 1857, C. Hoffmann s.n. (B?). [not seen].

Hemiepiphytic; appressed-climbing, stem often several meters long, sap watery, very aromatic-scented; internodes moderately elongate except near the apex, semiglossy, drying coarsely and irregularly ribbed (the ribs usually acute), 3–14 cm long, 1–2 cm diam, green to dark green to gray-green, soon drying light brown, epidermis sometimes loose and papery, roots usually 3–6 per node, usually less than 20 cm long, drying brown, less than 3 mm diam., semiglossy, sparsely scaly; cataphylls thin, (10)18–33 cm long, usually unribbed, sometimes sharply 1-ribbed, greenish, sometimes tinged reddish, deciduous intact. Leaves erect-spreading to spreading; petioles 20–61 cm long, 6–15 mm diam., terete to subterete, moderately spongy, sometimes obtusely somewhat flattened, sometimes with an obtuse medial rib, dark green, surface glossy to weakly glossy; blades deeply 3-lobed almost to the base or rarely trisect, about as broad as long in outline, thinly coriaceous, semiglossy, moderately bicolorous, acuminate at apex, lower surface sometimes heavily tinged purplish or reddish; typically rather dissimilar, median segment usually oblanceolate, sometimes nearly elliptic, rarely oblong to linear, 15–45 cm long, (4.5)7–14(19) cm wide, 1.9–7.8 times longer than wide (averaging 4.3 times longer than wide), (0.9)1.5(1.7) times longer than lateral segments;) the lateral segments conspicuously inequilateral, arcuate-spreading toward apex, (12)18–35 cm long, 1.3–15 cm wide, the inner margin always much narrower than the outer margin and weakly confluent with medial lobe, usually to 1 cm., rarely to 2 cm, the outer margin 1.5–5 times wider than the inner margin where the difference is most severe; midrib broadly convex, concolorous above, convex to round-raised, darker below; basal veins lacking; primary lateral veins (4)6–10(12) per side, departing midrib to a 25 degree angle on narrow blades or to 90 degree angle on broader blades, weakly curved on narrow blades or markedly curved on broader blades to the margins, sunken and usually concolorous above, convex and darker than surface below; minor veins fine and conspicuously visible, arising from both the midrib and primary lateral veins. Inflorescences usually solitary, sometimes 2–3 per axil; peduncle 3–16 cm long, 6–13 cm diam., medium green, moderately recurved with reddish ring around the apex; spathe (8)13–21 cm long, 1.2–4 cm diam., weakly constricted above the tube, to 2.5 cm diam. at constriction, usually medium green to yellow-green, rarely creamy white, with dark purple dots (most to 3 mm circumference) heavily so on tube, less so on blade throughout, white to creamy white or greenish white within, cucullate at apex, convolute in lower 2/3 of tube at base, margins whitish or colorless, recurled at anthesis; spathe blade glossy, smooth outside, (the opening 7.5–8.5 cm long, 3.4–5.2 cm wide), creamy white, glossy; resin canals intermittent, orange, appearing medially and extending into spathe tube inside; spathe tube oblong, glossy outside, 5 cm long, 3 cm diam., maroon, deep red, or purplish-violet inside; spadix sessile or shortly stipitate (to 2 mm); clavate, more or less erect, 12.3 cm long, broadest above the middle, weakly constricted between sterile and fertile portions; pistillate portion greenish white to pale yellowish green, 2.5–4.5(6.2) cm long, 1–1.8 cm diam. throughout; staminate portion 7.5–8.5 cm long; fertile staminate portion creamy white, 1.2 cm diam. at base, 1.3 cm diam. at middle, 1 cm diam. ca. 1 cm from apex, broadest in the middle, usually narrower than the pistillate and sterile portions; sterile staminate portion usually broader than the pistillate portion, creamy white, drying yellowish, 1.3 mm diam.; pistils 1.7–2.5(3.4) mm long, 0.6–1.1(2.3) mm diam.; ovary 6–8(10)-locular, 0.8–2.3 mm long, 1.1–2.3 mm diam., with sub-basal placentation; locules 0.8–1.1(2.3) mm long, 0.2–0.4(0.7) mm diam.; ovule sac 0.7–0.9(1.2) mm long; ovules 1–2 per locule, contained within a translucent and gelatinous matrix, 0.4–0.6 mm long, longer than funicle; funicle 0.2–0.4 mm long, (can be pulled free to base), style 0.4–0.8 mm long, 1–1.4(2.5) mm diam., usually similar to style type D (rarely B or E); style apex more or less rounded; stigma subdiscoid, truncate, 0.7 mm diam., 0.2–0.3 mm high, covering center of style apex, inserted on style boss; the androecium truncate, prismatic, margins usually irregularly 5-sided, 1.4 mm long, 2.2 mm diam. at apex; thecae oblong, 0.5 mm wide, more or less parallel to one another; sterile staminate flowers blunt, prismatic, irregularly 4–6-sided, 1.9 mm long, 1.5-2 mm wide. Berries whitish, irregularly angular, 4 mm long, 2–2.7 mm diam.; seeds usually 6–8 per berry, cylindrical, 1.5 mm long, sticky. Juvenile plants with blades maroon below.

Type: Costa Rica, at San José, 1300 m, May 1857, C. Hoffmann s.n. (B?). [not seen].

Napo: Anangu. Cultivated Plants - Waimea Arboretum and Botanical Garden. 260 m, Croat 76161 (MO). Pichincha: Patricia Pilar--Saltos del Bimbe, ca. 3 km N of Centinela on ridgeline of Montanas de Ila Cooperativa Piedad Alcivar, 600 m, Dodson 11809 (MO, QCNE, SEL).