19. Muhlenbergia nigra Hitchc., N. Amer. Fl. 17(6): 468. 1935.

Fig. 3F-J

Type.

México, México, Nevado de Toluca, cool slopes under pines, 2 Sep 1892, C.G. Pringle 4211 (holotype: US-746689!; isotypes, F!, MO-2974170!, MSC, US-821929!) .

Description.

Caespitose perennials. Culms 45-110 cm tall, erect, rounded near base, pubescent below the nodes, internodes glabrous to scaberulous. Leaf sheaths 3-17 cm long, shorter than the internodes, glabrous to scaberulous, the basal persistent, papery and flattened with age; ligules (5-)8-20 mm long, strongly decurrent, occasionally splitting into auricles, membranous to chartaceous above, firmer below near margins, apex truncate to obtuse; blades 5-25(-35) cm long, 2-3 mm wide, involute, scabrous and short pubescent above and mostly glabrous below. Panicles 6-15(-17) cm long, 5-10 mm wide, dense, spikelike, erect, exserted and surpassing the blades in height, plumbeous with a hint of green; primary branches 1-6 mm long, tightly appressed and ascending, imbricate, unexposed; pedicels 0.1-1.3 mm long, densely hispidulous. Spikelets (5.3-)6-8 mm long, erect, laterally compressed, plumbeous with a hint of green; glumes (5.3-)6-8 mm long, linear-elliptic to linear-ovate, usually longer than the lemma, 1-veined, sometimes mucronate or awn-tipped, scabrous along the keel, subequal; apex acuminate, scabrous, the awn up to 1.8 mm long; lemmas 5-6.5 mm long, broadly lanceolate, the margins involute, scabrous, unawned, mucronate or awned greenish-gray; apex acute, sometimes awn-tipped, the awn up to 1.3 mm long sometimes borne between two minute lobes, the lobes 0.1-0.3 mm long; callus sparingly pilose, the hairs 0.1-0.3 mm long; paleas 4.5-6 mm long, shorter than the lemma, scabrous; apex acute; anthers 2.5-3.2 mm long, grayish-green to whitish-gray. Caryopses 3-3.5 mm long, fusiform, brownish. Chromosome number unknown.

Distribution.

Muhlenbergia nigra occurs in central México south to Guatemala and Costa Rica (Peterson et al. 2001).

Ecology.

This species is found in mountain meadows, lava fields, and open pine forests; 2300-4000m.

Comments.

Muhlenbergia coerulea (Griseb.) Mez from the Cordillera de los Andes in South America is morphologically similar to M. nigra . However, in recent molecular studies M. nigra and M. coerulea, both members of M. subg. Trichochloa, do not share an immediate common ancestor but lie in a poorly resolved clade with 10 other species in the subgenus (Fig. 1; Peterson et al. 2018, 2021).

Specimens examined.

Costa Rica. San José: Sabana, south fork of Rio Talarí, A.S. Weston 12372 (CR, ISC); Pérez Zeledón, sendero a la Sabana los Leones, 700m. S del Puesto, A. Rodríguez 6461 (INB); Pérez Zeledón, P.N. Parque Nacional Chirripó, Cuenca Chirripó, Cuenca Terraba-Sierpe, sendero a Valle Los Leones, E. Alfaro 1770 (INB, MO); Pérez Zeledón, Paramo en Las Sabanas Chirrido, E. Alfaro 424 (INB, MO); Pérez Zeledón: bosques quemados y bosque enano camino al Rio Terbi y Sabana de Los Leones, J.F. Morales 5174 (INB); Pérez Zeledón, Parque Nacional Chirripó . Del Puesto Los Crestones, 2.5 km al Sur, camino a Sabana Leones, R. Robles 1784 (INB, MO); Rivas. P.N. Chirripó . Sabana de los Leones, J. Sánchez el al. 2870 (MO); P.N. Chirripó, Valle de los Conejos, R. Ocampo 1492 (CR); Parque Nacional Chirripó, Frente a refugio Los Crestones, G. Vargas et al. 540 (USJ); P.N. Chirripó, Sabana de los Leones, A. Weston 10114 (CR). Guatemala. Huehuetenango: Todos Santos, Cuchumatan, Tuicoy, R. Flores & M. Véliz 94.4308 (MO); Todos Santos Cuchumatan, camino a la Torre, M. Véliz et al. 14030 (MO); Sierra de los Cuchumatanes, ca. 28 mi from Huehuetenango, slopes of Cerro Chemal, J.G. Hanokes 1453 (US); Cerro Chémal, J.A. Steyermark 50305 (US-1935065, US-2208671). Quetzaltenango: Volcan Santa Maria, near summit of mtn., in open somewhat weedy and disturbed meadow above timberline, J.H. Beaman 4119 (US). Sacatepequez: Volcano Agua, open pine woodland on steep northern slopes, W.E. Harmon 3595 (MO); Santa Maria de Jesús, M. Véliz et al. 2M. 8512 (MO); Acatenango, Volcán de Acatenango, M. Véliz et al. 10351 (MO); Volcan de Agua, summit of south rim of crater. In open, gravelly soil, J.H. Beaman 2931 (US); Volcano Agua, A.S. Hitchcock 9117 (US); Volcan de Agua, W.A. Kellerman 7416 (US); Antigua, Volcan de Agua, W.A. Kellerman s.n. (US); Volcan de Agua, G. Salas 538 (US).