TYPE: Panama. Panamá: El Llano--Cartí road, 5 mi. from Pan American Hwy., virgin forest on steep slopes, along trail through forest, (W side of road), 350 m, 9E17'N, 78E58'W, 16 July 1987, Croat 67346 (holotype, MO 3609133; isotypes, B, CM, COL, CR, K, PMA, RSA, NY, US). Figures 57--60.

Planta hemiepiphytica, interdum epiphytica aut terrestris; internodia 1--4(11) cm longa, 1.5--3.5 cm diam.; cataphylla obtuse usque acute 2-costata aut incostata; petiolus subteres, 14--42 cm longus, subspongiosus cum annulo purpureo apice; lamina oblonga vel oblongo-ovata, subcordata, 24--73 cm longa, 8--29 cm lata; inflorescentia 1--2(3); pedunculus 3.6--11.5(17) cm longus; spatha 12.3--22 cm longa, lamina spathae extus alba vel viridalba, intus pallide viridis, tubo spathae extus viridi, intus viridi, striato rubello vel marronino basi; pistilla (5)7--8-locularia; loculi 1--2(4--5)-ovulati; baccae pallide virides vel albae.

Usually hemiepiphytic, sometimes epiphytic or terrestrial; stem appressed-climbing, sometimes creeping, to 1 m long, sap clear, sticky, sometimes black pepper-scented, leaf scars conspicuous, to 2.5 cm long, to 1.5 cm wide; internodes semiglossy, sometimes becoming matte, sometimes scurfy, 1--4(11) cm long, 1.5--3.5 cm diam., usually longer than broad, dark green to grayish or grayish green to brown, epidermis thin, drying brownish, irregularly ridged, frequently transversed fissured, cracking off; roots olive-green to brownish, slender, 0.6--100 cm long, to 3 mm diam., semiglossy, somewhat twisting, drying pale; cataphylls to 34 cm long, bluntly to sharply 2-ribbed (ribs to 5 mm high), green, densely short, dark green lineate or speckled, sometimes persisting as a rotting mass, eventually deciduous.
LEAVES erect-spreading to spreading to weakly arching; petioles 14--42 cm long, more or less terete, slightly spongy, medium green, obtusely flattened and sometimes with an obscure medial rib near apex adaxially, sometimes with adaxial margins erect, blunt, surface sparsely dark green short-lineate or unmarked, sometimes with a purple ring at apex, sheath 4--9.5 cm long; blades oblong to oblong-ovate, subcoriaceous, moderately bicolorous, semiglossy, subcordate at base, 24--73 cm long, 8--29 cm wide (2.5--3 times longer than wide), (ca. 1.7 times longer than petiole), margins moderately undulate, upper surface dark green, lower surface paler; anterior lobe 23.5--68 cm long, 11--27.5 cm wide, (10.5--15.6 times longer than posterior lobes); posterior lobes usually narrowly rounded and somewhat spreading or borader than long, rarely cordulate and about as long as broad, 1.5--6.5 cm long, 4.1--11.6 cm wide; sinus open or closed with lobes overlapping; midrib flat to broadly convex, slightly paler than surface or concolorous above, convex to bluntly acute, mostly concolorous, sometimes minutely speckled, matte or slightly semiglossy below; basal veins (1)2--3(4) per side, usually all free to base, sometimes with 2 united for up to 2 cm; posterior rib usually absent, never naked when present; primary lateral veins 6--10 per side, departing midrib at a 60--70E angle, more or less straight to the margins, obtusely sunken, paler than surface above, convex to weakly raised and darker than surface below; interprimary veins flat and darker than surface below; minor veins moderately distinct to more or less obsure above and below, arising from both the midrib and primary lateral veins.

INFLORESCENCES erect to spreading, 1--2(3) per axil; peduncle 3.6--11.5(17) cm long, to 1.8 cm diam., somewhat flattened adaxially, green, sometimes tinged red, weakly lineate or unmarked; spathe 12.3--22 cm long, (1.7--3.4 times longer than peduncle), to 3 cm diam. (when closed), oblong-linear, acute at apex, weakly constricted above the tube; spathe blade white to greenish white outside (opening 8.5 cm long, 5.5 cm wide), pale green, with orange resin canals inside; spathe tube green outside, 5--7 cm long, 2.3 cm diam., green, reddish to maroon or maroon-streaked at base inside; spadix stipitate to 4 mm long; white, 9--14.7 cm long, broadest above the middle, weakly constricted above sterile staminate portion; pistillate portion pale green, cylindrical, 2.9--5.4 cm long, 0.9--1.3 mm diam., weakly narrowed toward both ends; staminate portion 6.8--12.5 cm long; fertile staminate portion white, cylindrical to clavate, weakly tapered at apex, (5--7)12--15 mm diam. at base, 8--16 mm diam. at middle, (4)6--9 mm diam. ca. 1 cm from apex, broadest at middle or at base; sterile staminate portion narrower or broader than pistillate portion, white, 4--15 mm diam.; pistils 1.5--2.1(3.5) mm long, ovary (5)7--8-locular, 0.8--1.2(2) mm diam., with sub-basal or basal (or axile placentation in Croat 69250); ovules 1--2(4-5) per locule, 1-seriate, contained within transparent ovule sac, 0.3--1.7 mm long, longer than or equal in length to funicle, style similar to style type B; style apex with the shallow depression completely covered by stigma; style boss sometimes shallow, broad; stigma discoid to button-like (brush-like), 0.5--1 mm diam., less than 0.3 mm high, drying with the crown button-shaped and flat to concave with moderately large stylar pores around its periphery; the androecium margins 5(4--6)-sided, somewhat scalloped, 2 mm long; thecae oblong, 0.5 mm wide, nearly contiguous, sometimes divaricate; sterile staminate flowers more or less rounded.

INFRUCTESCENCE (immature), pale yellow-green outside; spadix to 3 cm wide, pistillate spadix 8--11 cm long; berries pale green to white; seeds tan, 1 mm long, 0.6 mm diam. JUVENILE petioles sheathed nearly throughout; blades oblong, obtuse to rounded at base, lower surface sometimes maroon.

Flowering in Philodendron annulatum is vouchered by one collection in January with the vast majority of post-anthesis collections made primarily between February through May, and a single collection in August and October. Mature fruits have been seen for only June and July.

Philodendron annulatum is endemic to Panama, ranging from Veraguas (Santa Fe) to Panamá and San Blas (El Llano--Cartí Road), at 100 to 970 m elevation in Tropical wet forest and Premontane rain forest.

Philodendron annulatum is a member of P. sect. Calostigma subsect. Macrobelium ser. Macrobelium. The species is distinguished by having internodes somewhat longer than broad and drying light brown, usually sharply two-ribbed, deciduous cataphylls, somewhat spongy obtusely somewhat flattened petioles with a purple distal ring (hence the name "annulatum" from annulatus, meaning "having a ring"), oblong to oblong-ovate, subcordate blades, and one to two inflorescences per axil with the spathe blade white and the tube green outside (usually colored or tinged red to maroon within).

Philodendron annulatum is most easily confused with P. ligulatum Schott. Philodendron correae Croat also has narrow, usually cordulate leaf bases and petioles with a purplish annular distal ring. Both differ from P. annulatum in having narrower blades broadest at or above the middle and narrowest just above the narrowly cordulate base. Alternatively, blades of P. annulatum are broadest at or near the base. Philodendron annulatum can also be confused with narrow-leaved representatives of P. sagittifolium. That species differs in having typically purple-spotted petioles (and often midribs) which lack a purplish distal ring.

  Additional specimens examined.

PANAMA. Coclé: 46 km N from Penonomé on road to Coclesito, 100 ft., Hammel 1698 (MO); El Copé region, Alto Calvario, on Continental Divide, 5.2 mi. above El Copé, 930 m, Croat 49186 (COL, K, MO); Alto Calvario above El Copé, ca. 6 km N of El Copé, 710--800 m, 89E39'N, 80E36'W, 68728 (AAU, CAS, K, L, M, MEXU, MO, PMA, TEX, US); 860 m, Folsom 1257 (MO); 4.1 mi. N of El Copé, 680--770 m, 8E39'N, 80E36'W, 74831 (CAS, CM, F, MO, PMA), 74855 (L, MO, PMA); E of sawmill along old logging road, 2,600 ft., Hammel 4076 (MO); 4.5 mi. N of El Copé, 2.5 mi. N of Escuela Barrigón, 580--740 m, 8E38'N, 80E36'W, Croat 67524 (AAU, COL, MO, US); El Valle region, vic. of La Mesa, N of El Valle de Antón, along E edge of Cerro Gaital, 900--1000 m, 8E37'N, 80E08'W, Croat 67225 (COL, MO, US); La Mesa, above El Valle, Croat 13467 (MO, SCZ); 775 m, 8E36'N, 80E07'W, 74803 (AAU, CAS, MO, PMA); 800 m, Croat & Zhu 76676 (MO). Colón: Río Guanche, ca. 1 km upstream from bridge at the Colón--Portobelo Road, 100 m, 9E30'N, 79E39'W, Croat 75191 (CM, MO, TEX); Río Iguanita, ca. 3 km above the bridge on Portobelo road, <100 m, 9E27'N, 79E40'W, 49760 (CM, MO). Panamá: El Llano--Cartí, 10 mi. from Pan-American Highway, 350 m, 9E14'N, 79EW, Knapp et al. 4727 (MO); 450 m, 9E14'N, 79EW, Knapp & Huft 4431 (MO); 7.5 km N of highway, Folsom 2555 (MO); 5--6 mi. N of highway, 350--375 m, Croat 34762 (MO); ca. 16--18 km from highway, 400 m, Tyson & Nee 7344 (F, MO), 7357 (MO, US); 4 mi. from highway, Croat 33731 (MO, NY); 3--3.5 mi. NE of Altos de Pacora, 700--750 m, 9E15'N, 79E25'W, 68696 (CM, KYO, MO, PMA, RSA); Cerro Jefe region, 750--800 m, 9E14'N, 79E22'W, 67088 (MO); 850 m, 67054 (MO); ca. 0.5 mi. below tower, 700--800 m, 9E15'N, 79E30'W, Thompson 4789 (MO); 800 m, Sullivan 211 (MO); 21 km above Pan-American Highway, ca. 600 m, Croat 35889 (MO); 4.6 km beyond peak on road to Altos de Pacora, 26.3 km from the Inter-American Highway, 600 m, 35895 (MO); 0.8 mi. beyond turnoff to Altos de Pecora, 970 m, 8E43'N, 82E17'W, Croat & Zhu 76620 (MO); Río Teralde, on road 8 km from Pan-American Hwy, 400 m, 9E08'N, 79EW, Knapp 1825 (MO). San Blas: El Llano--Cartí Road, 14 mi. N of Pan-American Highway, 300 m, 9E15'N, 79EW, Croat 69247 (CM, DUKE, MO, TEX), 69250 (CM, MO, NY); 14.5 mi. highway, 350 m, 9E15'N, 79EW, McPherson 9508 (MO, PMA); 10.1 mi. N of highway, 300 m, Croat & Zhu 76540 (MO); 1 mi. S of Nusagandi, 9 mi. N of Interamerican Highway, 350 m, 9E20'N, 79EW, Croat & Zhu 77013 (MO); 76568 (MO, US); 76569A (MO); 10.1 mi. N of main highway, 300 m, 9E20'N, 79EW, Croat & Zhu 76540 (MO); near Nusagandi, along Sendero Nusagandi, 300--350 m, 9E15'N, 79EW, McPherson 10756 (MO); 1-5 mi. N of Nusagandi, 250--300 m, 9E16'N, 79EW, Thompson 4661 (CM). Veraguas: Santa Fe region, Santa Fe--Río San Luis, past Escuela Agrícola Alto de Piedra, 8 mi. N of school, 450 m, 8E33'N, 81E08'W, Croat 66954 (K, MO, NY, PMA, QCA); 0.2 mi. beyond fork in road at Escuela Agrícola Alto Piedra, 750 m, 33971 (MO).