Geonoma trigona (Ruíz & Pavón) Gentry (1986: 161)

Henderson, Andrew, 2011, A revision of Geonoma (Arecaceae), Phytotaxa 17, pp. 1-271 : 152-153

65. Geonoma trigona (Ruíz & Pavón) Gentry (1986: 161) . Carludovica trigona Ruíz & Pavón (1798: 293) . Ludovia trigona (Ruíz & Pavón) Persoon (1807: 576) . Salmia trigona (Ruíz & Pavón) Willdenow (1811: 401) . Type: PERU. Huánuco: no locality, no date, J. Pavón s.n. (holotype MA, destroyed, isotype FI n.v.).

Plants 2.9(1.5–4.0) m tall; stems 3.0 m tall, in diameter no data, solitary; internodes no data. Leaves 6 per stem, undivided, plicate, bases of blades running diagonally into the rachis; sheaths 17.9(15.0–20.7) cm long; petioles 7.1(3.0–9.0) cm long, drying green or yellowish; rachis 18.3(11.7–32.0) cm long, 6.3(4.9–7.6) mm, in diameter; veins raised and rectangular in cross-section adaxially; pinnae 1 per side of rachis; basal pinna length and width not applicable, forming an angle of 17(10–27)° with the rachis; apical pinna 22.9(18.0–26.0) cm long, width not applicable, forming an angle of 17(11–23)° with the rachis. Inflorescences branched 1–2 orders; prophylls and peduncular bracts not ribbed with elongate, unbranched fibers, flattened (if tubular, narrow, and elongate then not ribbed), deciduous or persistent; prophylls 36.2(27.5–43.0) cm long, not short and asymmetrically apiculate, the surfaces not ridged, without unequally wide ridges; peduncular bracts 27.0 cm long, well-developed, inserted 18.7 cm above the prophyll; peduncles 46.4(38.0–61.0) cm long, 7.4(6.4– 8.7) mm in diameter; rachillae 10(9–11), 14.2(11.3–19.4) cm long, 5.0(4.0–5.6) mm in diameter, the surfaces without spiky, fibrous projections or ridges, drying brown or yellow-brown, without short, transverse ridges, not filiform and not narrowed between the flower pits; flower pits spirally arranged, glabrous internally; proximal lips apiculate and lobed before anthesis, tearing in the center after anthesis, not recurved after anthesis, not hood-shaped; proximal and distal lips drying the same color as the rachillae, not joined to form a raised cupule, the proximal lip margins overlapping the distal lip margins; distal lips absent; staminate and pistillate petals not emergent, not valvate throughout; staminate flowers deciduous after anthesis; stamens 6; thecae diverging at anthesis, inserted almost directly onto the filament apices, the connectives bifid but scarcely developed; anthers short and curled over at anthesis; non-fertilized pistillate flowers persistent after anthesis; staminodial tubes crenulate or shallowly lobed at the apex, those of non-fertilized pistillate flowers not projecting and persistent after anthesis; fruits 9.0 mm long, 6.5 mm in diameter, the bases with a prominent, asymmetric stipe, the apices not conical, the surfaces not splitting at maturity, without fibers emerging, bumpy from the numerous, subepidermal, tangential, short fibers present, these coming to a point at fruit apices; locular epidermis without operculum, smooth, without pores.

Distribution and habitat:— From 3°27’– 11°35’S and 75°37’– 78°22’W on eastern Andean slopes in Ecuador and Peru at 2698(2090–3000) m elevation in pajonal or dwarf forest ( Fig. 41 ).

Taxonomic notes:— Geonoma trigona is a member of a group of high elevation, Andean species (the G. undata clade, also including G. lehmannii , G. orbignyana , G. talamancana , and G. undata ). It is distinguished by its absent distal lips of the flower pits. The species is also notable for its strongly plicate leaves. In fact, it was first placed in the Cyclanthaceae and was only recently transferred to Geonoma ( Gentry, 1986) .

Subspecific variation:— No traits vary within this species. There is geographic discontinuity and specimens come from two areas on the eastern slopes of the Andes—southern Ecuador, and central Peru. There are too few specimens to test for differences between these two areas. See under Geonoma undata subsp. undata for possible hybrids with that species.

Figures

FIGURE 41. Distribution maps of Geonoma triandra, G. triglochin, G. trigona, and G. umbraculiformis.