25. Muhlenbergia plumiseta Columbus, Aliso 28: 66. 2010.

Fig. 16 G-L

Pereilema ciliatum E. Fourn., Mexic. Pl. 2: 93. 1886. Type: México, region Orizaba, 8 Nov 1866, E. Bourgeau 3328 (lectotype, designated here: P-00751680!; isolectotypes: K-000308948 [image!], L-0062312 [image!], MPU-026837 [image!], US-996083!). ≡ Muhlenbergia plumosa P. M. Peterson, Amer. J. Bot. 97(9): 1546. 2010, isonym. Basionym.

Description.

Delicate, caespitose, annuals. Culms 15-50 cm tall, decumbent, rooting at the lower nodes, smooth and glabrous below the nodes; internodes usually glabrous to scaberulous. Leaf s heaths shorter than the internodes, scaberulous or smooth; ligules 0.2-0.4 mm long, membranous, apex truncate, erose; blades 4-10 cm long, 1.5-3 mm wide, flat, acuminate, auriculate near base, the auricles 0.5-1 mm long, clasping, ciliate. Panicles (2-)3-8 cm long, 0.2-0.6 cm wide, spiciform, linear, continuous; primary branches 0.2-0.8 cm long, tightly appressed, pilose, ascending, frequently glandular, the spikelets arising just above the sterile spikelets or bristles, the bristles 1-4 mm long, plumose, deciduous; pedicels 0.1-0.2 mm long, arising just above the bristles. Spikelets 2-3 mm long, stramineous to mottled with gray areas, subtended by an involucre of deciduous bristles; glumes 1-3 mm long, narrowly awl-shaped, 1-veined, plumose, difficult to separate from the bristles; lemmas (1.8-)2-3 mm long, lanceolate, scabrous, 3-veined, usually awned, the awns (1-)5-25 mm long, straight or flexuous, callus hairy, the hairs 0.2-0.4 mm long; paleas (1.8-)2-3 mm long, as long as the lemmas, apex bidentate; stamens 3, anthers 0.6-1.4 mm long, yellow or purplish; styles 2. Caryopses about 0.8 mm long, ovoid. 2 n = 40 (Reeder 1968).

Distribution.

Muhlenbergia plumiseta ranges from northwestern México to Guatemala and El Salvador (Peterson et al. 2001).

Ecology.

This species occurs on open hillsides, ravines, and margins of forests in tropical deciduous forests and pine forests in shaded, often dry sites; 700-1800 m.

Comments.

Muhlenbergia plumiseta can be separated from M. pereilema in having deciduous, plumose bristles (bristles not plumose in M. Pereilema) subtending the spikelets and spiciform panicles (2-)3-8 cm long, 0.2-0.6 cm wide (10-22 cm long, 1-3 cm wide in M. Pereilema) [Herrera Arrieta et al. 2010). This species forms a clade with M. Beyrichiana and M. Pereilema within M. Subg. Muhlenbergia (Peterson et al. 2021).

Specimens examined.

Guatemala. Huehuetenango: Rio Selgua, from wooded slopes above Río Selegua, W.E. Harmon & J.D. Fuentes 4807 (MO) . Mexico. Chiapas: Chiapa de Corzo: above El Chorreadero, D.E. Breedlove 53812 (CHAPA). Chicoasén: Mirador "Manos que imploran", 10 km al SW de Chicoasén, A. Reyes G. 911 (MEXU). Jitotol: 3 km NE de Jitotol, en la carr. 195, F.W. Gould 12707 (ENCB, MEXU, US). Ocozocoautla de Espinosa: 14.8 mi de Ocozocoautla, en la carr. Méx ., J. Brunker & C. Perino 314 (ENCB). Tenejapa: Paraje de Kotol Te', D.E. Breedlove 7363 (ENCB, US). Tuxtla Gutiérrez: 2 mi S of Tuxtla Gutiérrez along road to Villa Flores, D.E. Breedlove & P.H. Raven 13334 (US); 11 km al NE de Tuxtla Gutierrez, Cañon del Sumidero, R. Torres, E. Cabrera & M. Huft 6348 (MEXU); 17 km al NE de Tuxtla Gutierrez, Cañon del Sumidero, R. Torres, E. Cabrera & M. Huft 6405 (MEXU). Zinacantán: along Mexican Hwy 190 at paraje Sequentic, D.E. Breedlove 28688 (MEXU) .