Philodendron albisuccus Croat, sp. nov.

TYPE: Panama. Darién: Parque Nacional del Darién, middle slopes on W side of Cerro Pirre, 800--1500 m, 7E56'N, 77E45'W, 29 June 1988, Croat 68940, (holotype, MO--3589989; isotypes, B, COL, K, PMA, US). Figures 41--43.

Planta hemiepiphytica; internodia 2--3 cm longa, 2.8 cm diam.; succus albus, in sicco calcareus; cataphylla leviter 1-costata vel acute 2-costata, persistentia ut fibrae tenues, pallidae; petiolus usque 51--72 cm longus, subteres, leviter complanatus basi usque ad medium; lamina anguste ovata, cordata basi, 50--66 cm longa, 24.5--42 cm lata; inflorescentia 1; pedunculus (3.7)7--12 cm longus; spatha 13.5--14.5 cm longa, extus viridis, intus pallide flaviviridis; pistilla 5--6-locularia; locules cum 18--20 seminibus; baccae albae.

Hemiepiphytic; stem more or less appressed-climbing, to 75 cm long, to 2.8 cm diam. sap chalky white; internodes short, usually sparsely covered with cataphyll fibers, 2--3 cm long, 2.8 cm diam., dark green; roots brownish, few per node, epidermis smooth to flaking and peeling; cataphylls thin, to 40 cm long, weakly 1-ribbed to sharply 2-ribbed, sparsely short-lineate, persisting as thin, pale fibers at upper nodes, then deciduous; petioles 51--72 cm long, 3--7 mm diam., erect-spreading, subterete, dark green, weakly flattened from near base to middle, obtusely sulcate at the base adaxially, surface semiglossy; blades narrow ovate, subcoriaceous, splitting, long-acuminate at apex (the acumen inrolled), cordate at base, 50--66 cm long, 24.5--42 cm wide (1.6--2 times longer than wide), (ca. about equal in length to petiole), broadest just below point of petiole attachment, upper surface dark green, semiglossy, lower surface semiglossy, moderately paler, drying yellow-green; anterior lobe 37--48(54.5) cm long, 23.1--27.4(42.4) cm wide (4.2--4.4 times longer than posterior lobes); posterior lobes 8.5--11.5(16.5) cm long, 9.7--12(18.5) cm wide; sinus hippocrepiform; midrib flat, concolorous above, bluntly acute, slightly paler than surface below; basal veins 3--5 per side, with 1 free to base, third and higher order veins coalesced 0.5-2 cm long, the fifth and sixth veins sometimes coalesced to 5 cm long; posterior rib naked, raised; primary lateral veins (4)6--7(8) per side, departing midrib at a 60--65E angle, sunken above, raised to convex below; interprimary veins darker than surface; minor veins arising from both the midrib and primary lateral veins; lesser veins obscure to visible.

INFLORESCENCES 1 per axil; peduncle (3.7)7--12 cm long, 3--3.5 mm diam., pale green; spathe semiglossy, 13.5--14.5 cm long, (1.2--1.8 times longer than peduncle), weakly constricted above the tube, green throughout, pale yellow-green (greenish brown post-anthesis) within; spathe tube densely short pale lineate outside, 5--7 cm long; spadix 12 cm long at anthesis; pistillate portion 4.3 cm long in front, 3 cm long in back, 8 mm diam. midway, 7 mm diam. at apex; staminate portion to 10 cm long; fertile staminate portion to 9 mm diam. toward apex, somewhat narrower just above the sterile portion, to 5 mm diam. 1 cm from apex; sterile staminate portion 9 mm diam.; pistils 6--6.3 mm long, 1.8--2.5 mm diam., ovary 5--6-locular, with axile placentation; ovules 2-seriate, style similar to style type B; style apex flat; stigma subdiscoid. INFRUCTESCENCE 6.4 cm long, 3 cm diam.; berries white; seeds 18--20 per locule.

Flowering in Philodendron albisuccus is poorly known with a flowering collection seen in October, immature fruits seen in June, and more nearly mature fruits seen in July.

Philodendron albisuccus is endemic to Panama, known only from the Serranía de Pirre in Darién Province, at 800 to 1400 m elevation in Premontane rain forest.

Philodendron albisuccus is a member of Philodendron sect. Philodendron subsect. Cardiobelium ser. Albisuccosa. The species is characterized by its short internodes, thin, obscurely one-ribbed cataphylls which persist at the upper nodes as thin, pale fibers, subterete petioles (about as long as the blades), the narrowly ovate, moderately cordate blades with a hippocrepiform sinus, and especially by the sap in all the cut plant parts, which promptly turns white and chalky upon exposure to air. Only one other species in Panama, P. cretosum Croat & Grayum, has chalky sap. Though both species have chalky sap (a rare feature for Philodendron) and 18--20 ovules per locule I do not believe them to be closely related as they show no other features in common. Philodendron cretosum differs most particularly in having slender oblong-lanceolate blades that are 5.1--8.3 times longer than wide (versus 1.6-2 times longer than wide for P. albisuccus). Philodendron albisuccus also has the much longer petioles (51-72 cm long versus 10-23 cm long for P. cretosum), more broadly spreading primary lateral veins (60--65E versus 25--45E angle for P. cretosum. In addition, P. albisuccus has minor veins more distinct than those of P. cretosum.

The species is superficially similar to both P. alticola Croat and P. straminicaule Croat & Grayum, both of which have blades of similar size, shape, and color upon drying. Both differ by having the inner surface of the spathe red rather than green.

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Additional specimens examined.

PANAMA. Darién: Cerro Sapo, ca. 5 km S of Garachiné, 600--800 m, 7E59'N, 78E25'W, Hammel et al. 14820 (MO, US); Cerro Pirre region, Altos de Nique--Cerro Pirre, ca. 8 km N of Alturas de Nique, ca. 8 km W of Cana Gold Mine, 1430--1480 m, Croat 37851 (MO, PMA); Río Cana--Río Escucha Ruido, along ascent of Serranía de Pirre above Cana Gold Mine, 1310--1430 m, 37830 (MO, US); Río Cana, SW of Cerro Pirre, vic. of old gold mine at Cana, 1400 m, 27319 (MO); Parque Nacional Darién, slopes of Cerro Mali, headwaters of S branch of Río Pucuro, ca. 22 km E of Pucuro, 1300--1400 m, 8E04'30"N, 77E14'W, Cuadros et al. 3961 (MO).