PHILODENDRON ATTENUATUM
PROTOLOGUE: Philodendron attenuatum , published in Aroideana 36E: 24 (2013).
Philodendron attenuatum Croat, sp. nov. Type: ECUADOR. Napo: Vicinity of Archidona, along road to San Pablo, 1.8 km E from main plaza in Archidona, 00°57'S, 77°49'W, 945 m, 21 Apr 2003, T. B. Croat, L. P. Hannon & N. Altamirano 87955 (holotype, MO-5704871–72; isotypes, AAU, B, CAS, COL, F, GOET, K, NY, QCNE, S, SEL, US). Figure 2 A–D.
DISTRIBUTION: Ecuador to Peru: Ecuador, Peru.
SPECIES DESCRIPTION:
Usually hemiepiphytic, sometimes terrestrial, or rupicolous; stems to 1 m long, drying light yellow-brown; internodes 1–4 cm long, 1–4.5 cm diam., typically about as long as broad, dark green to greenish gray and matte, scurfy; cataphylls 15.5–31 cm long, unribbed, spongy, medium green, pale green-speckled-lineate marcescent and deciduous; petioles 24.7–65 cm long 0.5–1.25 cm diam., spongy, subterete, obtusely and shallowly sulcate toward base, moderately spongy, obtusely flattened adaxially, semiglossy, densely dark green-lineate, dark green apical ring; blades ovate to ovate-cordate, 26.1–49.1 cm long, 14.5–36.6 cm wide, 1.39 (1.24–1.55) times longer than broad, 0.9 (0.7–1.1) times longer than petioles, truncate to subcordate at base with the leaf tissue usually decurrent on the petiole, subcoriaceous, moderately bicolorous, dark green and weakly glossy to semiglossy above, paler and semiglossy below, drying yellow-brown above, yellow-green below; anterior lobe length 20–40 cm, abruptly acuminate at apex; midrib broadly convex and slightly paler above, convex and much paler below, drying darker above, moderately paler below; primary lateral veins 3–5 per side, arising at an acute angle then spreading at a 50–60° angle, obtusely quilted-sunken and concolorous above, convex to slightly and paler below, drying moderately paler than the surface; minor veins moderately obscure to distinct below, minutely granular upon magnification with a paler, vein-like structure loosely coursing in a somewhat undulating pattern between the minor veins; the cross-veins typically clearly visible; laticifers if present, not obvious, the lower surface sometimes minutely granular; basal veins 4–5(–6); posterior lobes when present rounded, length 10–15 cm, width 10–14 cm; sinus, arcuate with blade decurrent and or hippocrepiform to 5.6 cm deep.
INFLORESCENCE:
Inflorescences 2–3 per axil; peduncle medium green, terete, 16–21 cm long, 10–12 mm diam., semiglossy, clearly demarcated at apex, 11.5–18 cm long, drying 4–7 mm diam., dark yellowish green; spathe 16–23 cm long, moderately green and semiglossy outside, pale green and glossy inside on blade, dark violet-purple inside on tube (to ca. 3 cm high), not obviously constricted, long-attenuate and often spreading back at apex; tube to 7.7 cm wide when flattened, drying yellowish to reddish brown; spadix stipitate 1.5 cm long, drying 15.6–18.6 cm long, medium brown to dark reddish brown; pistillate portion 3.7–7.7 cm long in front, 9 mm diam. at middle, 3.4–7.2 cm long in back, pale green; staminate portion 7.2–13.1 cm long, 6 mm diam., gradually long-tapered, the apex of male spadix protruding forward at anthesis, persisting dark brown post-anthesis; sterile staminate portion 5–7 mm long, 6 mm diam.; pistils 2.6–2.8 mm long, 2.6–2.8 mm diam., the style thick with rounded margins, shallowly sunken midway with a weakly raised stigma; stigma funnel-shaped, 0.4–0.5 mm diam., covered initially by a thin, very ephemeral mantle 1.4–1.5 mm wide; locules 5, 1.4–1.6 mm long; completely filled with a single, thin-walled ovular envelope filled with watery fluid; ovules with basal placentation, solitary, 0.2 mm long, funicles 0.2–0.4 mm long, the base of the funicle covered with a dense layer of glands.
ECOLOGY:
Found as a hemiepiphyte, sometimes terrestrial or rupicolous.
ETYMOLOGY:
Although the original description does not explicitly explain the name, the epithet is from Latin attenuatus, “tapered, drawn out, narrowed,” and almost certainly refers to the attenuated bases of the leaf blades — the feature Croat singles out in the diagnosis — and perhaps also to the long-tapered spathe and staminate spadix.
NOTES:
1. The species is a member of subgen. Philodendron sect. Macrobelium, subsect. Glossophyllum, ser. Ovata characterized by its moderately short internodes, unribbed, more or less marcescent and deciduous cataphylls, subterete, spongy petioles, more or less ovate blades with attenuated bases, inflorescences 2–3 per axil with the spathe green and long-tapered to the apex and often somewhat reflexed with the tube dark purple-violet inside as well as by a long-tapered staminate portion of the spadix which usually remains exposed outside the spathe after it closes.
2. The species is confusing from the standpoint of the presence of laticifers. There are unusual features that sometime resemble laticifers in that they have a rather undulating course between the minor veins but these structures seem to be continuous and typically pale, not blackened as in the case of most laticifers. Occasionally these structures become darkened in places but it is not certain that they are laticifers. Croat 50770, a collection from north of Yangzatza at 890 m elevation, is similar to Philodendron attenuatum in having the leaf base attenuated at the base but it differs in drying more yellow-brown and thicker, has the midrib drying darker than the surface on the lower surface and has the minor veins moderately obscure with no sign of cross-veins. In addition it has obvious laticifers which, as mentioned above, are lacking on Philodendron attenuatum.
3. R. Rojas & G. Ortiz 5975 differs from Ecuadorian material of the species in having an arcuate sinus with no decurrent tissue along the petiole but otherwise must be placed in the species.
4. J. Ruiz & J. Campos 1723 from the Peruvian province of San Martín in San Martín Province is probably also this species but it differs in having the sinus narrowly hippocrepiform with no leaf tissue decurrent along the petiole as is the case for material in Ecuador.
REFERENCES:
1. Plants of the World Online, Royal Botanic Gardens, Kew — Philodendron attenuatum
2. Aroideana 36E: 24 (2013) — protologue.
3. iNaturalist: Philodendron attenuatum
Additional photos by David Scherberich