MONSTERA TENUIS
PROTOLOGUE: Monstera tenuis K.Koch, published in Index Seminum Horti Botanici Berolinensis, Appendix 1855, App.: 4 (1855). The protologue is reproduced below.
SYNONYMS:
HETEROTYPIC SYNONYMS: Marcgravia paradoxa W.Bull ex G.W.Johnson & R.Hogg; Monstera gigantea Engl.
DISTRIBUTION: SE. Nicaragua to W. Panama: Costa Rica, Nicaragua, Panama.
DISTRIBUTION NOTE: iNaturalist: Alajuela, Bocas del Toro, Cartago, Chiriquí, Heredia, Limón, Puntarenas, San José.
SPECIES DESCRIPTION:
Robust to massive nomadic vine, appressed-climbing habit. Seedlings: filiform. Juvenile plants: root climbers; stems light-brown or green, smooth, flattened or cylindrical; internodes 2–10 cm long, 5–10 mm diam.; petiole not visible (covered by blade), dark green, smooth, 2–4 cm long; blades obovate, subcordate at base, acuminate at apex, coriaceous, 5–15 × 4–10 cm, appressed to the phorophyte; fenestrations absent. Adult plants: root climbers; stems light-brown or green, cylindrical, warty with pustules; internodes 3–8 cm long, 3–14 cm diam., 0.6–1.0 times as long as wide; anchor roots light brown; feeder roots dark-brown; petiole light-green, smooth, 25–70 cm long, sheathed to base of the geniculum; petiole sheath deciduous with fibrous remains; geniculum smooth, flattened adaxially, convex abaxially, 2–5 cm long; blades lanceolate to ovate to lanceolate-oblong, obtuse, truncate, sub-cordate or attenuate at base, obtuse to slightly acuminate at apex, coriaceous, drying yellowish, blackish, brownish or reddish, 45–90 × 35–50 cm, 1.5–2.0 times longer than wide, decurrent on the geniculum, decurrent portion 1–2 mm wide; midrib ribbed adaxially, convex abaxially, drying black to dark brown on both surfaces; primary lateral veins 5–60 per side, slightly sunken adaxially, prominent abaxially, drying blackish or dark brown; collective veins not visible; fenestrations present only in the transition to adult leaves; margins deeply pinnatifid, 5–30 lobes per side, often somewhat drooping, with 3–5 veins per lobe (the middle one the most prominent).⁴
INFLORESCENCE:
Inflorescences on ascending stems, 1–5 simultaneously at flowering time, arranged in the leaf axils; peduncle smooth, 4–10 cm long, 3–4(6) cm diam.; spathe obtuse to short-acuminate, green-yellowish externally and white-cream externally during development, completely open or tearing in fragments, deciduous after anthesis, 15–40 × 10–20 cm, as long as the spadix; spadix white-cream during development, yellow at anthesis, 13–40 cm long, 2–6 cm diam.; basal sterile flowers 5–8 mm long, with a yellowish stigmatic secretion; fertile flowers 0.9–1.5 cm long; stamens 2–10 mm long, with laminar filaments; anthers 1.5–2.0 mm long; ovary rectangular in longitudinal section, ribbed, 7–11 × 2–3 mm; style hexagonal, 4–6 × 2–3 mm; stigmatophore semi-columnar; stigma linear, with a yellow stigmatic secretion; berries with a pale-green stylar cap during development, mature stylar cap moss-green; pulp gray; seeds black with light brown dots, elongated, 6–10 mm long.⁴
ECOLOGY:
Monstera tenuis ranges from Nicaragua to Costa Rica and Panama, at 0–1766 m. It occurs in Tropical moist forest, Tropical wet forest, Premontane wet forest and Premontane rain forest life zones; in primary and secondary forest, and open areas.⁴
ETYMOLOGY:
Latin tenuis, "thin," referring to the membranaceous texture of the juvenile leaf lamina.⁶
NOTES:
1. The species, a member of sect. Marcgraviopsis, is characterized by the light green petiole, sheathing to base of the geniculum, with deciduous wings leaving fibrous residues, leaf blades deeply pinnatífid and never fenestrate, inflorescences with the spathe white-cream externally, spadices up to 40 cm long with short peduncles (<10 cm), and the infructescence moss green at maturity. It could be confused with Monstera pinnatipartita, but that species has the petioles speckled, with wings of the leaf sheath persistent and involute, and it lacks the shingling juvenile phase. Monstera tenuis is among the most robust species of the genus, only rivalled in the size of the leaves by Monstera deliciosa and Monstera alfaroi, and the recently described Panamanian Monstera gigas, the latter with leaves which can reach 3 m long (Cedeño-Fonseca et al. 2021b, 2022). Monstera tenuis also has the largest spadix of any species, though overall inflorescence size is eclipsed by Monstera titanum also from Panama, whose combined peduncle and spathe length can approach 1 m (Cedeño-Fonseca et al. 2021b, 2022). For more details about the taxonomic comments and nomenclatural note see Cedeño-Fonseca et al. (2022).⁴
2. Conservation status: Monstera tenuis is protected in the Jardín Botánico Wilson, Jardín Botánico Lankester, Reserva Biológica Monteverde, Estación Biológica La Selva, Estación Biológica La Tirimbina, Parque Nacional Guanacaste, Parque Nacional Rincón de la Vieja, Parque Nacional Volcán Arenal, Parque Nacional Braulio Carrillo, Parque Nacional Tortuguero, Parque Nacional Tapantí, Parque Internacional de La Amistad (parte baja caribe y pacífico), Parque Nacional Corcovado, Zona Protectora Volcán Miravalles and Reserva Forestal Golfo Dulce.⁵
STORY:
STORY TITLE: Fruit the size of a forearm
Monstera tenuis abounds on the Atlantic coastal plain of Nicaragua and Costa Rica and climbs the mountains to 1500 m. It is recognized by regularly pinnatifid leaves with 15 to 30 pinnae a side and by massive fruiting spadices the dimensions of a man's forearm, which at maturity often hang because the peduncle can no longer hold them upright.⁶
It is among the most robust species of the genus, rivaled in leaf size only by Monstera deliciosa and the Panamanian Monstera gigas, whose leaves reach 3 m, and it has the largest spadix of any species, though for total inflorescence length it is beaten by Monstera titanum, whose peduncle and spathe together approach a meter.⁵ Its flowers and fruits could not be properly documented in Costa Rica because the plants bloom more than 10 m above the ground. Stems hang free when the plant can climb no higher, but inflorescences appear only on ascending shoots.⁵
The name dates from an 1855 Berlin seed list and rests on a juvenile plant in the shingling stage, grown from living material of unrecorded origin that Warszewicz had introduced and the Berlin nurseryman Louis Mathieu had raised. The holotype is apparently no longer at Berlin, but two fragments annotated by N. E. Brown survive at Kew.⁵ The epithet, thin, refers to that membranous juvenile leaf, not to the giant it becomes.⁶
The classic account of a Monstera seedling growing toward the darkest sector of its horizon, and so toward the nearest trunk, was made on a plant published as Monstera gigantea.⁷ That name is ambiguous and probably covers Monstera tenuis or Monstera dubia.⁶
REFERENCES:
1. Plants of the World Online, Royal Botanic Gardens, Kew — Monstera tenuis K.Koch
2. Index Seminum Horti Botanici Berolinensis, Appendix 1855, App.: 4 (1855) — protologue.
3. iNaturalist: Monstera tenuis
Additional photo by Patrick Blanc
Additional photos by David Scherberich
Additional photos from iNaturalist by Linden Hickson, Daniel Garrigues, Marcel Esquivel, Giovanni Carraro, Gage Mallard, hiddenutah, andregeelhoed, John Beer, kevin_christ, Marietta Landis, mdoliveira, Nicolas Fl, pilgrim123, Ash Kerby-Miller, Drew Monkman, Ethan Beaver, Michael Kemp, Patrick Jackson and Stephanie Lyon
Additional photos from Wikimedia Commons by Dick Culbert from Gibsons, B.C., Canada, Dick Culbert from Gibsons, B.C., Canada, Jacob Rehage and Jacob Rehage
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