Monstera gigas Croat, Zuluaga, M. Cedeño & O. Ortiz, Webbia

Croat, Thomas B., Cedeño-Fonseca, Marco & Ortiz, Orlando O., 2024, Revision of Monstera (Araceae: Monsteroideae) of Central America, Phytotaxa 656 (1), pp. 1-197 : 90

22. Monstera gigas Croat, Zuluaga, M. Cedeño & O. Ortiz, Webbia 76(2): 272–275. 2021. ( Figs. 40 , 41 )

Type: — Panama. Chiriquí: Fortuna Dam area, unnamed creek to E of road flowing into Río Hornito near Quebrada Moro , 1200 m, 16 Jun 1984, W. Churchill 5508 (holotype MO-3216379–821 !, isotype PMA!) .

Very robust to gigantic, pachycaulous, appressed-climbing nomadic vine or rarely terrestrial. SEEDLINGS: bearing foliose leaves. JUVENILE PLANTS: root climbers; unknown. ADULT PLANTS: root climbers; stems pale green, smooth, cylindrical; internodes 1.5–2.0 cm long, 3–11 cm diam., 0.2–0.5 times as long as wide; anchor roots unknown; feeder roots unknown; petiole light green, white-dotted, smooth, (45)66–81(140) cm long, sheathed up to (0.36)0.74– 0.86 its total length; petiole sheath slightly persistent, drying dark brown with pale brown margins; geniculum white-dotted, 13–17 cm long, 3 cm diam.; leaf-blades narrowly ovate-elliptic, rounded on both sides, subcordate on one side and rounded on the other side, or unequal (one side 4–5 cm wider) at base, short-acuminate at apex, moderately coriaceous, (43)72–86(140) × (25)34–40(61) cm, 1.67–2.20 times longer than wide; fenestrations absent or present; margins entire; midrib weakly sunken and colorless to weakly discolored toward the distal margin, greenish white and thicker than broad abaxially, convex toward the apex, closely rounded and pale brown below; primary lateral veins (21)24–65 per side, sunken and colorless adaxially, closely narrowly rounded and pale abaxially, departing the midrib at (40°)55–75° toward the apex and 80–90° in the lower part of the blade; secondary veins parallel, moderately prominent adaxially. INFLORESCENCES on ascending stems; peduncle smooth, 34.0– 38.5 cm long, 1.7–2.2 cm diam.; spathe acuminate, white at anthesis, coriaceous, 30–34 × 15.0– 18.5 cm; spadix white at anthesis, 20.0– 25.5 cm long, 3.2–4.2 cm diam.; basal sterile flowers 3–5 mm long; fertile flowers 5–6 mm long; stamens with laminar filaments; anthers 1.5–2 mm long; ovary rectangular in longitudinal section, ribbed, 4–5 × 1.5–2.5 mm; style hexagonal, 1.5–2.0 × 1.5–2.0 mm; stigma circular; berries with a white stylar cap when ripe; seeds unknown.

Distribution and ecology: — Monstera gigas is endemic to Panama where it is known only from the type locality in the region of the Fortuna Lake at 1200–1300 m, in a Premontane rain forest life zone.

Phenology: —Fruiting has been recorded in January, April, July, and September.

Discussion: —The species is member of sect. Monstera characterized by its usually nomadic-vine (but sometimes terrestrial) habit, large stems with short, stout internodes, subterete, pale yellowish brown petioles sheathed to within 13–17 cm from the base (to 36 cm on preadult leaves), and ovate-elliptic, grayish-drying, entire and non-perforated, short-acuminate leaf blades, rounded at the base and with 24–65 primary lateral veins per side, as well as by its moderately short-pedunculate, massive, green-white spathes, green spadices, and flowers with a narrow style covered for nearly its entire width by the stigma, the latter bearing a tubular extension that protrudes beyond the end of its center.

Leaves at the upper end of the size range for this species, exceeding 3 m in length, are the largest so far know in the genus, and the plant is perhaps the most massively constructed member of its entire subfamily.

Additional specimens examined: — PANAMA. Chiriquí: Vicinity of Gualaca, ca. 8.6 mi from Planos de Hornito on the road to the La Fortuna dam site, 4000 ft, T. Antonio 500 2 ( MO!) ; Along road between Gualaca and Fortuna dam site; 7.9 mi beyond (NW) of Los Planes de Hornito ; virgin forest, 1300 m, T.B. Croat 49904 ( MO!) ; Gualaca-Chiriquí Grande, 4.8 mi beyond IRHE facilities at Dam, 4 mile N of bridge over Bayano Lake , along gravel road which turns off main highway, 100 m beyond pipeline marker 108, T.B. Croat 68031 ( MO!) ; Chiriquí, Gualaca, Hornito. Fortuna , camino a Chiriquí Grande , 1230 m, M. Cedeño et al. 2328 ( MO, PAM, USJ) ; Veraguas: Vicinity of Santa Fe on slopes of Cerro Tute-Arizona above school at Alto Piedras ; on trail to summit, 900–1100 m, G. McPherson 13672 ( MO!) .

Figures

FIGURE 40. Monstera gigas from Fortuna, Panama. Adult plant with the stem beige, 11 cm diam., and leaves up to 3 m of length. M. Cedeño et al. 2328 (PMA). Image from Cedeño-Fonseca et al. (2020b).

FIGURE 41. Monstera gigas from Fortuna, Panama. Michael Mittermeier (left) with a leaf up to 3 m of length, and Marco Cedeño and Orlando Ortiz (right) with a leaf up to 2 m of length. M. Cedeño et al. 2328 (PMA). Image from Cedeño-Fonseca et al. (2020b).