PHILODENDRON ATRATUM
PROTOLOGUE: Philodendron atratum , published in Aroideana 36E: 19 (2013).
Philodendron atratum Croat, sp. nov. Type: ECUADOR. Morona-Santiago: Along road between Palora and Yushin, departing main Palora-San Vincente de Tarqui road, 8.7 km NW of Palora, 3.4 km S of Río Amudalo, 2.1 km E on road to Yushin, 922 m, 01°41'46”S, 78°01'21”W, 25 Aug 2002, T. B. Croat & L. P. Hannon 86951 (holotype, MO-5746852–53; isotypes, AAU, B, CAS, COL, F, GH, K, M, NY, S, SEL, QCNE, US, USM). Figure 1 A–D.
DISTRIBUTION: Colombia to Ecuador: Colombia, Ecuador.
SPECIES DESCRIPTION:
Terrestrial, epiphyte or hemiepiphyte; stems less than 1 m long; internodes dark green and semiglossy, later gray-brown, short, 3–8 cm diam., 1–3 cm long, coarsely short-ribbed at apex; cataphylls 18.8–35 cm long, medium green, sharply 2-ribbed, marcescent then deciduous, drying with fragments of dark brown epidermis and pale fibers; petioles spongy, subterete, obtusely flattened adaxially, medium green, matte-subvelvety to semiglossy, dark green-lineate, obtusely ribbed adaxially, 2.2 cm diam. at apex, 2.8 cm diam. midway, drying 59.8–86.9 cm long, 0.9–1.7 cm diam., blackish brown; geniculum 1.5–3.2 cm long, drying slightly paler than petioles; preadult blades broadly ovate cordate to sagittate, to 34.3 cm long, 25.5 cm wide (averaging 30 x 22), the sinus ca. 3 cm deep, narrowly rounded at the apex; adult blades broadly ovate, 61.1–93.4 cm long, 41–68 cm wide (averaging 76 x 55), 1.30–1.49 (averaging 1.38) times longer than broad, 0.7–1.4 (averaging 1.0) times longer than petioles, abruptly acuminate at apex (acumen to 1.7 cm), broadest above petiole attachment, subcoriaceous, semiglossy, moderately bicolorous, dark green and semiglossy to matte-subvelvety above, moderately paler and weakly glossy below, drying dark grayish black and glossy above, paler and semiglossy below; anterior lobe 46.3–72.2 cm long, the margins broadly rounded; posterior lobes 19.3–35.2 cm long, 15.8–27.6 cm wide, directed downward and inward; midrib broadly convex to flattened and slightly paler above, narrowly rounded, faintly dark-lineate and concolorous below, drying darker above and below; primary lateral veins 5–6 per side, arising at a 60° angle near base then a 50° angle near apex, weakly and obtusely sunken, slightly paler above, thickly convex and slightly paler below, drying darker above and below; minor veins moderately obscure, arising mostly from midrib but also from the primary lateral veins closer to margins, drying obscure above and distinct below; laticifers long and discontinuous, weakly raised appearing like minor veins; basal veins 7(8) pairs, the 1st pair free to the base, 2nd pair fused to 2–2.5 cm, the 3rd and 4th pair fused to 2.4–5 cm; posterior rib gradually curved, naked 1.5–2.5 cm; sinus spathulate, 13.3–21.9 cm deep, 5.4–16.8 cm wide.
INFLORESCENCE:
Inflorescences 4–5 per axil; peduncle 8.7–11.3 cm long, 0.9–1.7 cm diam. midway, pale green, whitish at base, pale-striate, drying black-brown; spathe medium green, semiglossy, faintly pale short-lineate, open face paler, tinged violet-purple on outside, inner surface white and glossy on blade, heavily tinged violet-purple in tube, drying 14.9–18 cm long, 4.4–6.2 cm wide, reddish black-brown; tube 3.2–4.7 cm diam., constriction 2.5–3.0 cm, blade 2.6–2.9 cm diam.; spadix 17 cm long, drying 12.6–16.4 cm long, dark brown; pistillate portion 1.3–2.3 cm long in front, 2.2–3.1 cm long in back, 12 mm diam. at middle; staminate portion 10.6–11.5 cm long, 1–1.2 cm diam., gradually tapered; sterile staminate portion 5–8 mm long, 1.3–2.0 cm diam. toward apex, to 1.5 cm diam. at constriction; pistils 2.5–2.6 mm long, 1.5–1.7 mm diam.; style with margins rounded, slightly narrower than the stigma; stigma rounded, 15 [sic]–1.6 mm diam., 0.1 mm thick, consisting of 5–6 irregular mounds around the periphery with a medial concavity, completely covered with stigmatic papillae; locules 5–6, 1 mm long, 0.2 mm diam.; ovules ca. 10 or more per locule; placentation axile, 0.1 mm long, the funicle about as long as the ovule.
ECOLOGY:
Found from 280–1524 m in a Premontane wet forest life zone.
ETYMOLOGY:
From Latin atratus, “blackened” or “dark,” referring to the very dark to blackened dried leaf blades.
NOTES:
1. The species is recognized by its thick stems with short internodes, sharply 2-ribbed, marcescent and deciduous cataphylls, obtusely flattened petioles, very large, thick black-drying blades as well as by the 4–5 inflorescences per axil with medium green spathe outside with the tube heavily tinged violet-purple in the tube.
2. There is no other species of Philodendron that has black-drying leaves of this size but in the Lucid Philodendron Key the species tracks to Philodendron dodsonii Croat & Grayum, a species that occurs only on the Pacific slope of the Andes and has blades that dry much paler and reddish brown and the spathe tube red-purple to dark reddish outside. The 2016 Lita-San Lorenzo revision gives Philodendron dodsonii a wider range: Costa Rica, Colombia and Ecuador.⁴
3. A single collection from Carchi Province on the Pacific slope in Tulcán Cantón appears to be this species also but since this would be the only species known to the author from that area to occur in the Amazona basin, the author is reserving judgment regarding its determination.
4. A collection from Cajamarca Department, San Ignacio Province at 1650 m is perhaps this species. It has blades which dry dark brown and has a similar shape but only a short portion of the posterior rib which is naked (only about 1 cm).
STORY:
STORY TITLE: Named for leaves that dry black
When Thomas Croat described Philodendron atratum in 2013, he pointed to a character shared by no other member of the genus: leaf blades this large that dry to a deep grayish black. That blackening gives the plant its name — atratum, Latin for “blackened” — and it is the surest way to tell the species apart: in the Lucid Philodendron Key, Philodendron atratum keyed out to Philodendron dodsonii, a species whose blades dry far paler and reddish brown instead.²
Philodendron atratum grows in premontane wet forest on the Amazonian side of the Andes, ranging from southern Colombia through eastern Ecuador at roughly 280 to 1524 m. Its limits are still unsettled: Croat reserved judgment on a Pacific-slope collection from Carchi that appears to be this species, and called another, from San Ignacio in northern Peru, only “perhaps this species.”²
REFERENCES:
1. Plants of the World Online, Royal Botanic Gardens, Kew — Philodendron atratum
2. Aroideana 36E: 19 (2013) — protologue.
3. iNaturalist: Philodendron atratum
4. Croat, T. B., Delannay, X., Duncan, S. & Kostelac, C. V. (2016). Revision of Philodendron from the Lita-San Lorenzo Region (Esmeraldas Province, Ecuador). Aroideana 39(1): 26–315.
Additional photos by David Scherberich