ContentsPhilodendron radiatum

Philodendron dressleri G. S. Bunting,

Ann. Missouri Bot. Gard. 50: 25. Fig. 2. 1963. TYPE: Mexico. Nayarit: Tepic--San Blas, along Hwy. 54, 14--16 mi. SW of junction with Hwy. 15 (Tepic-Mazatlán), 75 m, 5 Sept. 1961, Moore & Bunting 8688 (holotype, BH; isotypes, K, MO, US). Figures 152, 157--160.

Hemiepiphytic; stem scandent, 3--3.5 cm long, 4--4.6 cm diam., leaf scars conspicuous, 3--3.5 cm long, 4--4.6 cm wide; internodes short, stout, succulent, scurfy, 3--6.5 cm long, 4--7 cm diam., broader than long, pale olive-green to gray-green, becoming grayish white with age, epidermis peeling; roots few per node, brownish, smooth, long, to 7 mm diam.; cataphylls 16--22 cm long, sharply 2-ribbed, drying weakly 2-ribbed, densely short dark striate, sometimes deciduous in dry season; petioles 34.5--70 cm long, 1--1.8 cm diam., terete, somewhat spongy, surface dark green-striate, dark green ring around apex; blades ovate in outline, deeply incised-lobate, bipinnatifid, weakly bicolorous, matte to semiglossy, acute to weakly obtuse at apex (the acumen apiculate), cordate at base, 30--46.5 cm long, 27--40.5 cm wide (0.99--1.2 times longer than wide), (0.9--1.2 times longer than petiole), broadest near the middle; anterior lobe 20.5--30 cm long with up to 6 segments, 12--19 cm long and each 3--5-lobed; posterior lobes rounded in outline, turned up at angle to midrib with ca. 5 similarly lobed segments; sinus closed or nearly so; segments pinnatifid, 12.3--27 cm long, divided to within 2--15 cm from the midrib; the interlobal sinus divided 0.4--0.7 the length of the lobe; midrib flat, dark green striate, paler than surface above, round-raised, pale striate, paler than surface below; basal veins 4 per side, 3--4 coalesced 5--10 mm; posterior rib naked for 2.5 cm; primary lateral veins 5--6 per side, departing midrib at a 45--60E angle, more or less straight, eventually branching to the margins, flat to weakly raised above, round-raised and paler than surface below; reticulate veins visible, darker than surface below; minor veins arising from both the midrib and primary lateral veins; tertiary veins sunken and paler than surface above, raised and paler than surface below.

INFLORESCENCES 1 per axil; peduncle 9--16 cm long, 7--9 mm diam. (dried), green; spathe 12--21 cm long (1.3 times longer than peduncle), weakly constricted above the middle, more or less obtuse at apex; spathe blade dark green outside, pinkish, with darker punctations inside; spathe tube green outside, to 4.5 cm long, purplish violet to wine-red or crimson inside; spadix 10--15 cm long; pistillate portion to 3.5 cm long, 2.2 cm diam.; staminate portion to 14 cm long; fertile staminate portion clavate, to 1.9 cm diam. at base, 2.4 cm diam. ca. 1 cm from apex; sterile staminate portion 2.4 cm diam.; pistils 3.7(7) mm long; ovary 4--5-locular, with axile placentation; ovule sac 2.5 mm long; ovules 3--4 per locule, 2-seriate, contained within translucent envelope, 0.4 mm long, longer than funicle; funicle 0.2--0.3 mm long, adnate to lower part of axillary wall, style similar to style type B; central style dome sometimes present; style apex flat; stigma subdiscoid to hemispheroid, 1.8 mm diam., 0.7 mm high, covering entire style apex; the androecium truncate, more or less prismatic, irregularly 5--6-sided, ca. 1.6 mm long; thecae more or less oblong, 0.4 mm wide, nearly contiguous, more or less parallel to one another.

INFRUCTESCENCE with spathe 10-13 cm long, pistillate spadix 4--6.5 cm long, 3.5--4 cm diam.; seeds 3--4 per locule, 2 mm long, 0.8 mm diam.

Flowering in Philodendron dressleri is probably during the rainy season. Post-anthesis collections are known from July and September with immature fruiting collections known from December and January.

Philodendron dressleri is endemic to west central Mexico from coastal Nayarit including Tres Marías Islands, off the western coast of Mexico) to southern Sinaloa, from sea level to 370 m elevation in "Selva Baja Caducifolia."

Philodendron dressleri is a member of P. sect. Polytomium. This species is characterized by its stout, succulent stems with short internodes, weakly two-ribbed, deciduous cataphylls, terete, somewhat spongy petioles (about as long as the blades), bipinnatifid blades divided about midway to the midrib, and solitary green inflorescences with the spathe tube purplish violet to wine-red within.

Philodendron dressleri is the most northerly-ranging species of Philodendron, extending almost to the Tropic of Cancer. It is probably most closely related to P. warszewiczii, but is also similar to P. radiatum, both of which differ in having gradually much more deeply divided (almost to the midrib) blades (versus pinnatifid 0.4--0.7 the way to the midrib in P. dressleri). Philodendron warszewiczii ranges from Honduras to western Mexico, but no further north than the state of Jalisco. Philodendron radiatum ranges no further north than Chiapas on the Pacific slope.

The species is superficially most similar to P. radiatum var. pseudoradiatum, which also has blades divided less than halfway to the midrib. However, that taxon differs in comprising more scandent plants with slender stems having internodes longer than broad (2--12 x 1--2.5 cm for P. radiatum var. pseudoradiatum versus 3--3.5 x 4--4.6 cm for P. dressleri).

For an additional photo of this species see Bunting (1965: 332).

Click on the Thumbnail to enlarge the picture.

Additional specimens examined.

MEXICO. Nayarit: near Sangaite, E of San Blas, Philbrick 414 (BH); Tepic--Puerto Vallarta, along Hwy 200, 33 mi. S of Tepic, 4 mi. N of Las Varas, 370 m, Croat 45360 (CM, MO); 6 mi. S of Mazatan, Dressler & Wirth 2732 (UC, US); W of Jalcocotán, Dressler 1051 (UC); 5--6 mi. E of San Blas along highway, Gentry et al. 19477 (US); Tres Marías Islands, María Madre, Ferris 6249 (DS, US). Sinaloa: Labradas vic., Ferris & Mexia 5290 (CAS, DS); Culiacán, Gónzalez-Ortega 6632 (US); Mpio. Concordia, Sindicatura Mesillas, Cañada La Calera, 200 m, Trejo 1112 (US); Sindicatura Panuco, La Calera, Gónzalez-Ortega 271 (MEXU); Mpio. Mazatlán, Gónzalez-Ortega 7393 (US).