PHILODENDRON ANGUSTILOBUM

PROTOLOGUE: Philodendron angustilobum , published in Annals of the Missouri Botanical Garden 84: 396 (1997).

Philodendron angustilobum Croat & Grayum, sp. nov. TYPE: Costa Rica. Heredia: Estación Biológica La Selva, confluence of Río Sarapiquí and Río Puerto Viejo, 10°26′N, 84°01′W, 50–80 m, Grayum & Chavarría 8302 (holotype, MO). Planta hemiepiphytica; internodia 3–6(15) cm longa, 1.5–3 cm diam.; cataphylla 12–33 cm longa, acute 2-costata; petiolus subteres, 17–54 cm longus, 5–10 mm diam.; lamina profunde 3-lobata, 30–48 cm longa, 20–48 cm lata; in sicco atricana vel atribrunnea supra, flavibrunnea vel atricanibrunnea infra; lobis lateralibus manifeste patentibus, in sicco denigratis infra; inflorescentia 1–3; pedunculus (4.5)9–11(15) cm longus; spatha (11)13–18 cm longa, lamina spathae extus interdum suffusa alba; tubo spathae pallide viridi, extus interdum suffusa marronino basi; pistilla 7–10-locularia; loculi (1)2-ovulati.

DISTRIBUTION: C. America, SW. Colombia: Colombia, Costa Rica, Honduras, Nicaragua, Panama.

SPECIES DESCRIPTION:

Hemiepiphytic; stem appressed-climbing, growing to 2.5–6 m high in trees; internodes matte to weakly glossy, 3–6(15) cm long, 1.5–3 cm diam., dark green, drying gray (within 4–6 internodes), epidermis drying light brown, semiglossy, often peeling (underlying stem blackened), fissured transversely, longitudinally ridged; cataphylls soft (especially near base), 12–33 cm long, bluntly to sharply 2-ribbed or sharply 1-ribbed to near the apex then 2-ribbed below, green, sometimes tinged red, deciduous, persisting deciduous, intact; petioles 17–54 cm long, 5–10 mm diam., subterete, somewhat spongy, dark green, weakly flattened toward apex with an obscure medial rib adaxially, with adaxial margins rounded to weakly angular, surface weakly glossy, drying blackened; sheathing 3–9 cm long; blades deeply 3-lobed, subcoriaceous, moderately to conspicuously bicolorous, 30–48 cm long, 20–48 cm wide (1–1.5 times longer than wide), (0.8–1.8 times longer than petioles), upper surface dark green, drying dark gray to dark brown, semiglossy, lower surface drying dark yellow-brown to dark gray-brown, weakly glossy, moderately paler; anterior lobe 28–39 cm long, 8.5–14(17) cm wide (1.8–1.9 times longer than lateral lobes), rarely broadest at the base, usually narrowed toward the base (4–12 cm wide just above the base); sinus arcuate to broadly V-shaped; lateral lobes (7.5)15–22(27) cm long, 3–8(12) cm wide, broadest usually toward the apex, directed outward, broadly spreading (90–127° angle), broadly confluent with medial lobe 3.3–6.5 (rarely to 14) cm, acute; midrib broadly convex to flat-sunken above, convex, slightly paler than surface, drying blackened below; basal veins 8–10 per side, pinnately arranged along a stout medial rib; posterior rib not at all naked or rarely naked for 1–1.5 cm; primary lateral veins 5–6 per side (45–75° angle on median lobe), gradually curved to the margins, sunken above, convex, drying blackened below; interprimary veins weakly raised and darker than surface below; minor veins distinct, darker than surface below, arising from both the midrib and primary lateral veins.

INFLORESCENCE:

INFLORESCENCES 1–3 per axil; peduncle (4.5)9–11(15) cm long; spathe (11)13–18 cm long, 8–10 mm diam. (1.4–1.6(2.4) times longer than peduncles), greenish white outside, greenish white to white within; spathe opening broadly at anthesis, convolute in only lower one-half of tube, barely or not at all constricted above the tube; spathe blade sometimes tinged white outside; spathe tube light green, sometimes tinged maroon at base outside; spadix held erect, not protruded forward, oblong to oblong-tapered, rounded to bluntly acute at apex, (9.5)11–15.5 cm long, broadest near the middle, constricted weakly above sterile staminate portion; pistillate portion pale green, oblong to oblong-tapered, 4.5–5.7 cm long, 8–10 mm diam. at apex, 8–12 mm diam. at middle, (5)11–13 mm wide at base; staminate portion 8–11 cm long; fertile staminate portion oblong-tapered, 8–13 mm diam. at base, (6)12–13 mm diam. at middle, 8–9 mm diam. ca. 1 cm from apex, usually broader than the pistillate portion; sterile staminate portion ca. 1 cm diam.; pistils 1.5–3 mm long, 1.1–1.8 mm diam., ovary 7–10-locular, (0.8)1.1 mm diam., with sub-basal placentation; ovules 1(2) per locule, contained within transparent ovule sac, 0.6 mm long, usually shorter than funicle, style similar to style type B; style apex rounded; stigma button-like, subdiscoid, 1 mm diam., 0.2–0.4 mm high, covering center of style apex; thecae oblong to oblong-ovate, contiguous, sometimes divaricate. JUVENILE plants with petioles 8–10 cm long; blades oblong, rounded to weakly subcordate.

ECOLOGY:

Found in tropical wet forest and premontane wet forest life zones, from near sea level to 680 m elevation on the Atlantic slope and from 800 to 1430 m near the Continental Divide in Panama

ETYMOLOGY:

From Latin angustus, “narrow,” and lobus, “lobe,” meaning “narrow-lobed.” Although the original description does not explicitly explain the name, it likely refers to the conspicuously narrow, broadly spreading lateral lobes of the deeply 3-lobed leaf blade, which are much narrower and shorter than the medial lobe.

NOTES:

1. Philodendron angustilobum is apparently a member of Philodendron sect. Tritomophyllum [though M. Grayum (pers. comm.) believes it is closest to Philodendron ligulatum, a member of Philodendron sect. Calostigma subsect. Glossophyllum ser. Glossophyllum]. This species is characterized by its moderately long internodes, spongy petioles, and 3-lobed blades, which dry blackened with broadly spreading lateral lobes that are much narrower and shorter than the medial lobes. It is superficially similar to Philodendron mexicanum Engl., which has sagittate blades that dry green to brown and occurs typically in much drier habitats.

2. The sole Honduran collection might prove to represent another species or perhaps even a hybrid. It differs from material collected from Nicaragua, Costa Rica, and Panama in having the medial lobe broader, more triangular, and not at all constricted at the base.

3. Two collections (Croat & Grayum 59933 and Croat 67616) from the same plant from southwestern Costa Rica near Golfito differ in having the posterior lobes less narrowed; they may prove to represent another species.

4. Flowering in Philodendron angustilobum has been recorded from the early dry season through the mid-wet season, including February, March, May (the greatest number), and August, but too few collections exist to be certain of phenology.

REFERENCES:

1. Plants of the World Online, Royal Botanic Gardens, Kew — Philodendron angustilobum

2. Annals of the Missouri Botanical Garden 84: 396 (1997) — protologue.

3. iNaturalist: Philodendron angustilobum

Additional photos by David Scherberich

Additional photos from iNaturalist by Sharon Brown, Julia Harencar and LostInCR