Trichanthecium acrotrichum (Hook.f.) Zuloaga

Zuloaga, Fernando Omar, Aliscioni, Sandra, Delfini, Carolina & Salariato, Diego Leonel, 2024, Old World species of Trichanthecium (Poaceae: Panicoideae: Paniceae) including a new species from the Democratic Republic of Congo, Phytotaxa 646 (3), pp. 230-264 : 238

1. Trichanthecium acrotrichum (Hook.f.) Zuloaga , comb. nov.

Panicum acrotrichum Hooker (1864: 226) . Eriochloa acrotricha (Hook. f.) Hack. ex Schinz (1906: 399) .

Lectotype [designated as “holotype” by A.P.M. van der Zon (1992: 220)]:— CAMEROON. “Hab. Cameroon Mountains ”, December 1882, G. Mann 2100, K [ 00182374 ] image!, isolectotype SI!) .

Perennial, not tufted; culms slender, 20–30(–50) cm long, decumbent, rooting and branching at the lower nodes, then erect; internodes cylindrical, hollow, glabrous, 3–10 cm long, longer than the sheaths; nodes dark, compressed, glabrous. Sheaths striate, 3–6 cm long, glabrous, the upper margins ciliate. Ligule membranous, laciniate at the apex, pale, 0.5 mm long, with long hairs beneath at the base of the blade. Blades ovate-lanceolate, 2–8 × 0.4–1.8 cm, flat, asymmetric, with cross veins, subcordate to cordate at base, acuminate, sparsely to densely pilose, with tuberculate hairs, to glabrous, the margins scaberulous, the basal ones ciliate. Inflorescence a terminal, open to contracted, long exserted panicle, 6–10(–14) × 2–6 cm; peduncle cylindrical, 12–22 cm long, glabrous; pulvini glabrous; first-order branches alternate, divergent, glabrous, spikelets solitary and appressed on the upper portion of first-order branches, pedicels flexuous, 1–4 mm long, claviform, glabrous. Spikelets ellipsoid, 2.1–2.6 × 1–1.1 mm, greenish; lower glume long ovate, 1–1.8 mm long, 1/2 or more the length of the spikelet, 1–3(–5)-nerved, membranous, pilose; upper glume as long as the spikelet, membranous, 5–7-nerved, acute, with long whitish hairs 3–4 mm long toward the apex; lower lemma glumiform, 2 mm long, 5–7-nerved, acute, with long whitish hairs toward the apex or glabrous; lower palea elliptic, hyaline, 1–1.7 × 0.9 mm or absent; lower flower neuter. Upper anthecium ellipsoid, 1.7–2 × 0.7–1 mm, pale, chestnut at maturity, indurate, smooth and shiny, upper lemma 5-nerved, with bicellular microhairs toward the apex. Caryopsis not seen.

Distribution and habitat: —West tropical Africa, where it is present in Cameroon and Equatorial Guinea (Bioko); it grows in montane forest shade, at 2000–3000 m elevation.

Chromosome number: —2n = 32 ( Morton 1993).

Typification: — When describing Panicum acrotrichum, Hooker f. (1864) did not indicate where the type specimen collected by Mann was deposited, nor did he provide its collecting number. Van der Zon (1992) designated the specimen K00182374 as the holotype of the species; this is a well-preserved specimen that agrees with the protologue of the species.

Notes: —This species is distinguished, from other species of the genus, by the presence of long whitish hairs at the apex of the upper glume.

Trichanthecium acrotrichum was classified, as P. acrotrichum , as Vulnerable (A2c) according to Cheek & Lovell (2021) (https://www.iucnredlist.org/).

Representative specimens examined: — CAMEROON. Buea , January 1929, Maitland 344 ( K, US) ; Mann´s Spring , between Lu and Ukile, 30 March 1948, Brenan 9533 ( BR, K, P, US) ; Tchabal Mbabo : Hama Aoudi, 3 November 1967, Jacques-Félix 9026 ( P) ; Piste de Verkovi au Mont Oku , 15 km SW de Kumbo, 8 December 1974, Letouzey 13459 ( P) ; Bamenda Division , 22 May 1959, Hepper 2028 ( K, P) ; Douala et Mts. Bamboutos, 21 November 1965, Meurillon 58 ( BR, P) ; au NW de Nabemo, route Meigan-Baibokoum , 15 October 1963, Letouzey 6176 ( P). EQUATORIAL GUINEA. Bioco , El Pico, 10 December 1951, Boughay 119 ( K, P), ibidem, Boughay 129 ( SI, US), ibidem, Boughay 134 ( K) ; Bioco , carretera del Pico Basilé, km 18–19, 2470 m, 1 November 1988, de Carvalho 3676, 3757 ( BR, US) .