Plants annual or perennial; usually synoecious, infrequently andromonoecious; sometimes rhizomatous, often cespitose, sometimes mat-forming, rarely stoloniferous. Culms 2–300 cm, erect, geniculate, or decumbent, usually herbaceous, sometimes becoming woody. Sheaths open; ligules membranous or hyaline (rarely firm or coriaceous), acuminate to truncate, sometimes minutely ciliolate, sometimes with lateral lobes longer than the central portion; blades narrow, flat, folded, or involute, sometimes arcuate. Inflorescences (synflorescence) terminal, sometimes also axillary, open to contracted, racemelike or spikelike panicles; disarticulation usually above the glumes, occasionally below the pedicels. Spikelets mostly perfect with 1 (2–6) florets, sometimes staminate or sterile, occasionally paired or in groups of threes then the central spikelet perfect and the lateral ones staminate or sterile; chasmogamous, rarely cleistogamous; glumes usually (0)1(2–3)-veined, apices entire, erose, or toothed, truncate to acuminate, sometimes mucronate or awned from the midvein, occasionally awned from the lateral veins; lower glumes sometimes rudimentary or absent, occasionally bifid; upper glumes shorter than to longer than the florets; calluses poorly developed, glabrous or hairy, the hairs up to 3.5 mm long, straight; lemmas glabrous, scabrous, or with short hairs, 3-veined (rarely appearing 5-veined), apices awned from the midvein, mucronate, or unawned; awns, if present, straight, flexuous, sinuous, or curled, sometimes borne between 2 minute teeth, lateral veins occasionally extended into awns; paleas shorter than or equal to the lemmas, 2-veined, apices; lodicules 2, cuneate, fleshy, sometimes with a narrow membranous apex, apex truncate and slightly lobed, glabrous; anthers (1–2) 3, purple, orange, yellow, olivaceous, or whitish; ovary with 2 styles (rarely 1), glabrous, stigmas plumose. Caryopses an achene,elongate, fusiform or elliptic, slightly dorsally compressed, rarely laterally compressed, free threshing; grain solid without lipid. Cleistogamous panicles sometimes present in the axils of the lower cauline leaves, enclosed by a tightly rolled, somewhat indurate sheath. Chromosome base number is x = (8 or 9) 10, and these are relatively small in size when compared to chromosomes in the Pooideae.

The genus is primarily distributed in the Western Hemisphere in North, Central, and South America (Peterson 2003; Peterson and Giraldo-Cañas 2012; Peterson et al. 2018, 2021). There are also eight species known to occur in southeastern Asia; six of these are found in China (Wu and Peterson 2006) and five in India (Tiwari et al. 2023).

The species occur in open habitats in deserts, grasslands, sclerophyllous scrubland, and margins of forests often in xeric to meso-xeric habitats from near sea level to more than 4000 m.

Named for Gotthilf Henry Ernest Muhlenberg (1753–1815), a Lutheran minister and pioneer botanist of Pennsylvania, USA.

Guatemala. Quezaltenango, in thickets at base of vertical slopes along railroad, Finca Pirineos, lower S facing slopes of Volcán Santa María, between Santa Maria de Jesus and Calahuache, 1300–1500 m, 31 Dec 1939, J.A. Steyermark 33175 (holotype: F-1057948 [image 64109!]; isotype: US-2236470 fragm. ex F!).

Strongly caespitose perennials. Culms 70–80 cm tall, stout, compressed-keeled near base, glabrous below the nodes; internodes glabrous. Leaf sheaths glabrous below becoming scabrous near the collar; ligules 3–10 mm long, hyaline, apex attenuate, appearing shredded and withering with age; sheath auricles 4–8 mm long, often rudimentary and withering with age; blades 25–42 cm long, 2.5–5 mm wide, flat, conduplicate near base, scaberulous above, scabrous below, margins saw-toothed. Panicles 28–36 cm long, 5–10 cm wide, nodding, dense, golden yellow; primary branches 10–17 cm long, ascending, appressed to spreading up to 30° from the culm axis, without spikelets on the lower half; pedicels 1.5–2 mm long, scabrous. Spikelets 1.7–2.2 mm long, erect, yellow; glumes 1.7–2.2 mm long, as long as the floret, the upper glumes slightly longer than the lower, apex acute, scabrous, mucronate, the mucro up to 0.6 mm long; lemmas 1.8–2 mm long, hyaline, indistinctly 3-veined, pubescent on the lower 1/3 of the margins and midvein, awned, awns 10–20 mm long, flexuous borne just below the apex; paleas 1.7–1.8 mm long, a little shorter than the lemma, hyaline, glabrous; anthers not seen. Caryopses not seen.

Flowering December and January.

Known only from two collections in Guatemala, the type locality on the south facing slopes of Volcán Santa Maria in Departamento Quezaltenango between the cities of Quezaltenango and Retalhuleu (Peterson et al. 2001).

Muhlenbergia aurea occurs on slopes between 1300 and 1500 meters.

Swallen (1950) suggested M. aurea is related to M. scoparia Vasey “which differs in having narrower sheaths and blades, an elongate ligule, a narrow, less densely flowered, purple panicle, and longer awns.” Not much is known about M. aurea and currently it has not been investigated using molecular methods. However, based on morphology it is placed in M. subg. Trichochloa.

Figure 2. 

A–E Muhlenbergia aurea Swallen A habit B inflorescence C ligule D Spikelet E immature lemma F–H Muhlenbergia xanthodas Soderstr. F ligule G spikelet H lemma. A drawn from J.A. Steyermark 33175 (F-1057948) B–E drawn from M. de Koninck 241 (US-2182672) F–H drawn from E. Matuda 4003 (US-1817864).

Guatemala. Quetzaltenango: Finca Pirineos, lower south-facing slopes of Volcán Santa María, between Santa María de Jesús and Calahuaché, J.A. Steyermark 33175 (MO); Quezaltenango–Retalhuleu, 1480 m, 1954, M. de Koninck 241 (US-2182672).

Guatemala, Guatemala City, collected on clay hill, 1500 m, 2 Dec 1911, A.S. Hitchcock 9063 (holotype: US-995888!).

Densely caespitose perennials. Culms 70–140 tall, erect, stout, compressed-keeled near base, puberulent to glabrous below the nodes; internodes glabrous. Leaf sheaths 8–26 cm long, mostly longer than the lower internode, scaberulous to glabrous, basally becoming brown, curled and fibrillose or shredded, margins entire, apex pubescent on abaxial surface; ligules 0.1–2 mm long on the culm leaves, of innovations 6–13 mm long, membranous to chartaceous with a rim of hairs, lacerate, apex truncate; sheath auricles 1.5–6 mm long, whitish when present, often lacking; blades 20–50 cm long, 2–3 mm wide, usually abruptly narrowed at base (sheath and blade junction), flat to folded, scabrous above, sometimes pubescent near throat and scaberulous below. Panicles 30–51 cm long, 3–10 cm wide, nodding, somewhat dense, yellowish to purplish brown or purplish green; primary branches mostly 3–12 cm long, ascending, lax and nodding, appressed to spreading up to 40° from the culm axis; pedicels 0.5–3 mm long, scaberulous. Spikelets 2–3.5 mm long, erect, yellowish to purplish-brown; glumes 2–3.5 mm long, equal or a little longer than the floret, equal in length, lanceolate to oblong-lanceolate, 1-veined, occasionally the upper 2-veined, apex acute to acuminate, often scaberulous, sometimes mucronate, the mucros up to 0.2 mm long; lemmas 2.1–2.8 mm long, lanceolate to oblong-lanceolate, awned, midvein and margins pubescent to sparsely pilose on the proximal 2/3, the hairs up to 0.3 mm long, apex acute to acuminate; awns 6–18 mm long, straight or flexuous, borne just below the apex; callus sparsely pilose; paleas 2–2.7 mm long, oblong, the proximal 2/3 pubescent to sparsely pilose between the veins, apex acute; anthers 1–1.7 mm long, purple or yellow. Caryopses 1–1.3 mm long, fusiform, light brownish.

Figure 3. 

A–E Muhlenbergia breviligula Hitchc. A habit B ligule with auricles C glumes D floret E stamens and lodicules F–J Muhlenbergia nigra Hitchc. F habit G ligule H glumes I floret J stamens, pistil, and lodicules. A–E drawn from A. Molina R. 25227 (US-2942492) F–J drawn from S.D. Koch 76255 (US-2824590).

Flowering October through December.

Chiapas, México, southeast to Guatemala, Honduras, El Salvador, and Nicaragua (Peterson et al. 2001; Menjívar Cruz et al. 2021).

Muhlenbergia breviligula occurs on rocky slopes, along drainages, and in open pine-oak woodlands; 650–2530 m.

This species is morphologically similar to M. emersleyi Vasey, a species common in southwestern USA and northern México. However, M. breviligula differs in having culms with a short ligule 0.2–2 mm long (ligules 10–25 mm long in M. emersleyi), leaf blades 2–3 mm wide (2–6 mm wide in M. emersleyi), and persistent fimbrillose basal sheaths (not as persistent in M. emersleyi) [Soderstrom 1967; Peterson 2003]. Muhlenbergia breviligula, a member of M. subg. Trichochloa, has been found in an unsupported clade with three other species, distributed in North America (México), Central America, and South America (Columbia, Ecuador, and Peru) [M. lehmanniana, M. versicolor, and M. maxima Lægaard & Sanchez Vega] (Fig. 1A; Peterson et al. 2021).

El Salvador. Chalatenango: San Fernando, creciendo a orilla de la calle, J. González 398 (MO). Honduras. Choluteca: San Marcos de Colón, pine forest area near San Marcos [de Colón], L.O. Williams & A. Molina R. 10921 (MO). El Paraíso: Guinope, Galeras, along road ca 10 km S of El Zamorano, open pine forest. [Originally reported from Francisco Morazán], R.W. Pohl 12527 (MO); Alauca, Las Manos, 5 km N of Las Manos, near Los Limones, R.W. Pohl & M. Gabel 13430 (MO). Francisco Morazán: Tatumbla, 24 km E de Tegucigalpa, bosque húmedo subtropical, I. Cruz P. 75 (MO); In mountains along highway, 30 km W of Tegucigalpa, W.A. Archer 3846 (US); Drainage of the Rio Yaguare, floresta de pino roble, acueducto de la EAP, Zamorano, A. Molina R. 1593 (US); foothills of Mt. Uyuca, beyond Las Floras, overhanging steep bank in pine forest, J.R. Swallen 11323 (US); San Antonio de Oriente, El Zamorano, R.W. Pohl 12509 (MO); San Antonio del Oriente, overhanging bank, small shady canyon, about 2 km above San Antonio, J.R. Swallen 10968 (US); Distrito Central, El Picacho, carretera en el Picacho, Villatoro et al. 137 (MO). Lempira: Gracias, Río Mejocote [Rio Grande de Mejocote], 9 km de Gracias, pinares, C. Nelson et al. 252 (MO). Ocotepeque: Santa Fe, about 8 km southwest of Santa Fé, near the Guatemala border, R.A. Molina et al. 31271 (MO). Olancho: Jutiapa, mountain above a fire tower, Jutiapa Forest Station, between Concordia and Salamáa, pine forest on a steep slope, R.W. Pohl & M. Gabel 13493 (MO). Santa Bárbara: Quimistán, Cofradia, ca. 8 km S of Cofradia, along Highway 18, open pine savana on a hill, R.W. Pohl & M. Gabel 13392 (MO). El Paraíso: Dry hillsides along the Quebrada de Dantas, Rio Choluteca Valley about 16 km north of Yuscaran, L.O. Williams & R.P. Williams 18652 (US). Guatemala. Chiquimula: along Rio Taco, between Chiquimula and Montana Barriol, 3–15 mi NW of Chiquimula, J.A. Steyermark 30649 (US). Alta Verapaz: vicinity of Secanquim, O.F. Cook & C.B. Doyle 60 (US). Guatemala: Guatemala City, A S. Hitchcock 9063 (MO), A.S. Hitchcock 9064 (US). A.S. Hitchcock 9109 (US). Huehuetenango: Mountains wet of Aguacatan, on the road to Huehuetenango, open bank, P.C. Standley 81190 (US). Zacapa: 13 km east of El Lobo, North-facing slope of open field and thickets, Quercus and Pinus on drier slopes, W.E. Harmon & J.A. Fuentes 1851 (MO). Mexico. Chiapas: Arriaga: At La Mina Microwave Station, D.E. Breedlove 56328 (CAS, MO); Chiapa de Corso: Above El Chorreadero, D.E. Breedlove & R.F. Thorne 20499 (CAS, MO); 30 miles W of San Cristobal de las Casas on Mex 190 J. N. Brunken & C. H. Perino 354 (MEXU); Cintalapa: Crest of the Sierra, near the microwave station of La Mina, 12 km S of Mexican Highway 190, near Rizo de Oro, D.E. Breedlove & R.F. Thorne 20555 (CAS, MO); Comitán de Domínguez: 6 km N of Comitán along Mexican Highway 190, D.E. Breedlove & G. Davidse 54872 (CAS, MO); 6 km N of Comitán along Mexican Highway 190, D.E. Breedlove & G. Davidse 54870 (CAS, MO); Huistán: 10 km E of Huistán. [Tenejapa Mpo. (Huistan), D.E. Breedlove & G. Davidse 55186 (CAS, MO); Comitán de Domínguez: 6 km N of Comitán along Mexican Highway 190, D.E. Breedlove & G. Davidse 54872 (CAS, MO); 6 km N of Comitán along Mexican Highway 190, D.E. Breedlove & G. Davidse 54870 (CAS, MO); Ixtapa: near the Zinacantán Paraje of Muctajoc. Slope with tropical deciduous forest, D.E. Breedlove & G. Davidse 54005 (MEXU, CAS, MO), 54006 (CAS, MO), 54008 (MEXU, CAS, MO), 54009 (MEXU, CAS, MO), 54011 (CAS, MO); Intersection of the Tuxtla Gutiérrez-San Cristobal de las Casas and the Villahermosa highways, G. Davidse et al. 30101 (MO); along road from Zinacantán center to Ixtapa near Paraje Vo Bits, D.E. Breedlove 40709 (CAS, MO); Jiquipilas: Ejido Tierra y Libertad, A. Reyes-García 5556 (MEXU); La Independencia: 6–10 km NNE of La Soledad along logging road from Las Margaritas to Campo Alegre, D.E. Breedlove & B.M. Bartholomew 55670 (CAS, MO); La Trinitaria: a 12 km al S de la Trinitaria, camino a Cd. Cuauhtemoc, E.M. Martínez S. & W.D. Stevens 23905a (MEXU); 6–7 km S of La Trinitaria, G. Davidse et al. 29938 (MO); 6 km south of La Trinitaria on Mexican Highway 190, D.E. Breedlove & G. Davidse 55074 (CAS, MO); 20 km south of La Trinitaria, D.E. Breedlove & G. Davidse 55067 (CAS, MO); D.E. Breedlove 4216 (CAS, MO); Oxchuc: 5 km east of Oxchuc, D.E. Breedlove & F. Almeda 57120 (CAS, MO); San Cristóbal las Casas: NE edge of San Cristóbal las Casas, D.E. Breedlove 54721 & G. Davidse (CAS, MEXU, MO); Northeast edge of San Cristóbal Las Casas, D.E. Breedlove & G. Davidse 54746 (CAS, MEXU, MO); San Fernando: Parque Nacional del Sumidero, 20–22 km NW of Tuxtla Gutiérrez, along the road to the canyon Outlook, G. Davidse et al. 29764 (MO); Northeast edge of San Cristóbal Las Casas, D.E. Breedlove & G. Davidse 54728 (CAS, MO); San Juan Chamula, C. Santíz Ruíz 222 (MEXU); Tuxtla Gutiérrez: 22 km north of Tuxtla Gutiérrez. Cliff faces and limestone bluffs with Seasonal Evergreen Forest, Calycophyllum, Zanthoxylum, Bursera, Quercus, Ficus and Erythrina at El Sumidero, D.E. Breedlove & B.M. Bartholomew 55482 (CAS, MO); 16 km north of Tuxtla Gutiérrez on road to El Sumidero, D.E. Breedlove & Bruce M. 55494 (CAS, MO); t El Sumidero, 22 km north of Tuxtla Gutiérrez, D.E. Breedlove & A.R. Smith 21557 (CAS, MO); Venustiano Carranza: Wooded slope near the town, along the road to Pugiltic, R. M. Laughlin 2702 (ENCB); 3 mi S of Aguacatenango along road to Pinola Las Rosas, D.E. Breedlove & P.H. Raven 13135 (ENCB); Villa Corzo: Above Colonia Vincente Guerrero on road to Finca Cuxtepec [Custepec], D.E. Breedlove 54599 & G. Davidse (CAS, MO); near Paraje Navenchauk, D.E. Breedlove & G. Davidse 53899 (CAS MO); Near Colonia Vincente Guerrero, D.E. Breedlove 48584 (CAS, MO); Zinacantán: near Paraje Zinacantán, D.E. Breedlove 53901 & G. Davidse (MEXU); near the Zinacantán Paraje of Muctajoc, D.E. Breedlove & G. Davidse, (MEXU); D.E. Breedlove 13807 (DS, MO). Nicaragua. Nueva Segovia: Santa María, km 242, 1 km al W de Santa María, P.P. Moreno 25214 (MO).

Caespitose perennials. Culms 60–100(–150) cm tall, erect from the base, not conspicuously branched; internodes mostly glabrous, sometimes puberulent below the nodes. Leaf sheaths glabrous or puberulent, basal sheaths terete, often becoming fibrous, but never spirally coiled, at maturity; ligules 1.8–5(–10) mm long, membranous, firm, strongly decurrent, obtuse; blades 10–35(–80) cm long, 2–4 mm wide, flat or involute, smooth abaxially, scabrous adaxially. Panicles 15–50(–60) cm long, 8–30(–41) cm wide, longer than wide, diffuse; primary branches 2–20 cm long, capillary, diverging 30–100° from the culm axis, naked basally, lower branches with 5–20 spikelets; pedicels 10–40(–50) mm long, longer than the spikelets, capillary, flexible. Spikelets 3–5 mm long, usually purple, occasionally green, brown, or stramineous; glumes (0.3–)1–1.5(–2) mm long, usually less than 1/2 as long as the lemmas, subequal, glabrous; lower glumes 1-veined, usually unawned, rarely awned, awns 1–3 mm long; upper glumes 1-veined, rarely 3-veined, acute to acuminate, often erose, usually unawned, rarely awned, awns 1–3(–5) mm long; lemmas 3–5 mm long, lanceolate, not shiny, calluses short pubescent, apices scabrous, acuminate, sometimes with 2 setaceous teeth, teeth to 1 mm long, unawned or awned, awns 2–13(–18) mm long, clearly demarcated from the lemma bodies; paleas 2–4.5 mm long, lanceolate, acuminate, usually unawned; anthers 1.5–2 mm long, purple. Caryopses 2–2.5 mm long, narrowly elliptic, brownish.

Muhlenbergia capillaris ranges from the southeastern United States, the Caribbean coast of México (Quintana Roo), extending to Guatemala, Bahamas, and various Caribbean islands (Peterson et al. 2001). It is also grown as an ornamental. This species was reported from the Yucatán (Dávila et al. 2018) but we have been unable to locate a specimen to verify this record.

Muhlenbergia capillaris occurs in open woodlands, pine-oak forests, savannahs and on rock outcrops; 0–2020 m.

Muhlenbergia capillaris can be separated morphologically from M. rigida in having panicles 8–30(–41) cm wide with open, diffuse branches that are strongly divergent, whereas M. rigida has loosely contracted panicles 2–5(–12) cm wide with appressed to ascending branches spreading up to 80° from the culm axis. Muhlenbergia capillaris, a member of M. subg. Trichochloa, is found in a strongly supported clade sister to M. expansa (Poir.) Trin., a species from the southeastern USA (Fig. 1; Peterson et al. 2021).

Guatemala. Guatemala: Guatemala City, open prairie, A.S. Hitchcock 9141 (US-995855); Huehuetenango: Rocky dry slopes above San Ildefonso, Ixtahuacan, J.A. Steyernmark 50673 (US-1935074, US-2208677); Quiché: Chichicastenango, 1 km north of Chichicastenango. Small “prairie” next to a milpa, shallow soil on sandstone, W.E. Harmon 4364 (MO), mts. E of Quiche, V. Grant 645 (US-1818233). Mexico. Chiapas: near ranch house on S edge of Teopisca, D.E. Breedlove & P.H. Raven 13097 (MICH); Marsh near Teopisca, D.E. Breedlove & G. Davidse 54803 (MICH, CAS, MO); Teopisca, slope at W edge of Teopisca, D.E. Breedlove & J.L. Strother 46373 (CAS, MO). Quintana Roo: José María Morelos: Lake Chichancanab (Laguna Chan-kabnab), 28–29 July 1932, J.R. Swallen 2726 (MO, US-1537112, US-3090503).

Figure 4. 

A–C Muhlenbergia capillaris (Lam.) Trin. A habit B glumes C floret. A–C drawn from F. Lamson Scribner s.n. (US-746068) used in Hitchcock (1935).

Caespitose perennials often sprawling, occasionally with stolons. Culms (10–)25–55 cm tall, glabrous below the nodes; internodes glabrous. Leaf sheaths mostly 0.8–8 cm long, shorter than the internodes, glabrous; ligules 1–2 mm long, apex acute, lacerate; blades 1.5–6 cm long, 0.5–2 mm wide, flat, scaberulous above, smooth beneath. Panicles 2–8 cm long, 0.5–1.2 cm wide, open, loosely-flowered with recemosely arranged branches; primary branches 2–4 mm long, excluding the awns, one per node, often purplish. Spikelet fascicles of three with one sessile perfect spikelet (lateral staminate or sterile), the pedicels less than 0.2–0.5 mm long and the other two spikelets short-pedicelled, the pedicels about 0.7–1.2 mm long; glumes (1–)1.5–2.8 mm long, oblong and wider distally, 1-veined, apex deeply notched, awned, the awns 2–4 mm long, lobes triangular, acute; lemmas 2.5–3 mm long, fusiform, 3-awned, the central awns 5–13 mm long, lateral awns 2–3 mm long; paleas 2.5–3 mm long, puberulent, apex awned, the awns 1–2 mm long; anthers 1.6–1.8 mm long, yellowish to purplish. Caryopses 1–1.4 mm long, fusiform. 2n = 40, 60, 80.

Muhlenbergia cenchroides ranges from throughout México, throughout Central America (Costa Rica, El Salvador, Guatemala, Honduras, México, Nicaragua, and Panama) to South America in Bolivia, Brazil, Colombia, Ecuador, Peru, Guyana, and Venezuela (Pohl 1994a; Peterson et al. 2001).

Figure 5. 

A, B Muhlenbergia cenchroides (Humb. & Bonpl. ex Willd.) P.M. Peterson A habit B spikelets C–G Muhlenbergia diandra (R.W. Pohl) Columbus C habit D ligule with auricles E glumes F floret G stamens and pistil. A, B drawn from S. Beck 7464 used in Renvoize (1998) C–G drawn from P.C. Standley 44066 (US-1307162)

Muhlenbergia cenchroides occurs on rocky slopes, canyons, cliffs, roadcuts, arroyos, seeps, and meadows, often associated with Baccharis ssp., Salvia ssp., Eupatorium, Festuca, Schizachyrium, Muhlenbergia ssp., Hyptis, Oxalis, Aristida, Bidens, Sporobolus, Carex, Eragrostis, Lupinus, Lycopodium, Jarava, Nassella, Agave, Thalictrum, and Chusquea; 1430–3850 m.

Muhlenbergia cenchroides can be separated from its South American sister, M. bryophilus (Döll) P.M. Peterson (South American) in having anthers 1.6–1.8 mm long, the perennial habit with (10–)25–55 cm tall culms, and sessile or inconspicuously pedicelled perfect spikelets usually associated with two staminate or sterile pedicelled spikelets (Tovar 1993; Giraldo-Cañas and Peterson 2009). In addition to being perennial, Muhlenbergia cenchroides differs from M. uniseta in having glumes with acute lobes and central veins extending as an awn 2–4 mm long.

Muhlenbergia cenchroides, a member of M. subg. Muhlenbergia, lies in a strongly supported trichotomy with M. bryophilus and M. uniseta, and this trichotomy is sister to M. tarahumara P.M. Peterson & Columbus (Sierra Madre Occidental, México) in M. subg. Muhlenbergia (Peterson et al. 2010b; Peterson et al. 2021).

Costa Rica. Alajuela: SW of Palmira, A. Weston 3076 (USJ); 1 km S of Carrizal, R.W. Pohl & G. Davidse 11499 (CR); 6.5 km W of Varablanca, R.W. Pohl & C. Calderón 10278 (CR); 0.5 km W of Varablanca, roadside, R.W. Pohl & C. Calderón 10257 (CR). Cartago: Reserva Biológica Tres de Junio, J. Gómez-L. & D. Rivera 1221 (USJ); Interamerican Highway, about km 82, L. Clark et al. 1570 (USJ, MO, US); Cordillera Central, lower slopes of Volcán Irazú, 1 km below San Juan de Chicoa, R.W. Pohl & G. Davidse 11421 (CR); Reserva Forestal Río Macho, Cuenca del Savegre, Cerro de la Muerte, Carretera Interamericana, entre km 93/94, A. Rodríguez 4227 (CR, INB); Estación Cuericí, camino a la Auxiliadora, 2 km E de Villa Mills, B. Gamboa R. 753 (INB); Salsipuedes, bosque secundario y turberas en las cabeceras del rio Humo, J.F. Morales 6223 (INB, MO); Santa Rosa, E. Alfaro 5132 (INB); San Ramón de Tres Ríos, Westl. Talhang des Río Tiribí, untere Nebelwaldregion, Weg Einschmitt, vollsonniger Lehmhang ohne Gehölze, H. Kuhbier 214 (CR); Heredia: P. Döbbeler 2010 (MO); San José de la Montaña, M. Montiel s.n. (USJ); Monte de la Cruz, R. Ocampo 1251 (CR); 2 km N of Porrosatí, R.W. Pohl & M. Gabel 13673 (CR); San José de la Montaña, D. Santamaría 3092 (INB); Parque Nac. Braulio Carrillo Porrosatí, Río Ciruelas, R. Rivera 457 (MO). San José: Santa Maria de Dota, J. Bustamante 218 (INB); Hda. Tiquires, Bosque primario, robledales y potreros en la Fila Aguabuena cerca de la Laguna, J.F. Morales 4232 (MO, INB); Bosque secundario en la cima del Cerro Pico Alto, cabeceras del rio Poas, El Cidral, J.F. Morales 1725 (INB); Copey, Cerro Vueltas, bosques enanos transición a páramo y páramos en la cima, L. G. Clark 1570 (INB); Carretera Interamericana, ruta al Cerro de la Muerte, 2 km después de los Chespiritos dirección a Pérez Zeledón, entre km 80–81, A. Rodríguez 3276 (INB, MO); Dota, Reserva Ftal Los Santos, Estación Ojo de Agua, Calle a Providencia, E. Alfaro 2223 (INB); along Carretera Interamericana between km 103 and km 106, ca. 7.7–9.7 km beyond La Georgina toward San Isidro de El General, M. Grayum 8154 (INB); Bajo Gamboa, 1 km sobre el camino que conduce al Cerro Caraigres, J.F. Morales 6718 (CR, INB); R.F. Los Santos. Providencia Dota, Fila Cerro Vueltas, J.F. Morales 8412 (INB); Salsipuedes, km 69, Carretera Interamericana, B. Hammel 5132 (INB); Direct line from Hotel La Georgina to Cerro Frío of the Cerro Buenavista complex (Cerro de la Muerte), area with television and radio towers, G. Davidse 25028 (MO); along Carretera Interamericana between km 103 and km 106, ca. 7.7–9.7 km beyond La Georgina toward San Isidro de El General, M. Grayum & J. Affolter 8154 (MO); Z.P. Cerros de Escazú, Cerros Escazú-La Carpintera, J.F. Morales 1725 (MO); Cuenca Térraba-Sierpe. Estación Cuericí, camino a la Auxiliadora, bosque secundario en orillas del camino, B. Gamboa R. 753 (MO); Los Santos, Est. Ojo de Agua, colectando en bosque y orillas del tendido eléctrico, E. Alfaro & M. Alfaro 2223 (MO); Cerro León, camino hacia Fila Aguabuena, A. Quesada et al. 751 (CR); Cerro León, camino hacia Fila Aguabuena, A. Quesada et al. 755 (CR); Los Cuadros, O. Jiménez 710 (CR); Cordillera de Talamanca, 26 km N of San Isidro del General along the Carretera Interamericana, R.W. Pohl & G. Davidse 10755 (CR); along carretera Interamericana, ca. 10 km N of San Isidro del General roadsides, R.W. Pohl & C. Calderón 10064 (CR); Montane forest formations with open landslides and road cuts and swamps, about 22 km SE of Empalme, along the Interamericcan Highway, G. Davidse 6452 (CR); Z.P. Cerros de Escazú Río Londres y Río Agres, bosque ripario secundario, G. Vargas & J. Sánchez 940 (CR); Los Santos Ca. 4 km due S of La Georgina at Villa Mills off the Interamerican Hwy., F. Almeda & K. Nakai 4824 (CR); R.F. Los Santos Camino entre San Gerardo y Carretera Interamericana, A. Estrada et al. 2782 (CR); Cerro León, camino hacia Fila Aguabuena, R. Chacón et al. 188 (CR); San Antonio, S. Lobo 908 (CR); Rivas, A. Rodríguez 6509 (INB); Páramo, D. Santamaría 3151 (INB); Páramo, S. Lobo 1656 (CR); Carretera interamericana Sur, J. Gómez. 6342 (CR); 71 km from San Isidro del General on Cartago road, H.S. McKee 11221 (US). El Salvador: Santa Ana, Cerro Monte Cristo, NE of Metapan, R.W. Pohl 12581 (CR); Montecristi, R. Villacorta & J. González 1158 (MO); Volcán de Santa Ana, G. Davidse & R.W. Pohl 2050 (MO); Parque Nacional Montecristo, camino a Miramundo, R.A. Carballo & J. Aldana RAC00590 (MO). Usulutan: Laguna de Alegría, por la entrada, D. Williams & R.W. Williams 356 (MO). Guatemala. Alta Verapaz: H. von Turckheim s.n. (MO).). Chimaltenango: Vegetación del volcán de Acatenango, M. Vélz 93.2751 (MO). Guatemala: Guatemala city, A.S. Hitchcock 9108 (US). Huehuetenango: Carretera a la Sierra de los Cuchumatanes, M. Véliz, 96.5778 (MO); Dry oak-pine forest and ravines about 6 km S of Huehuetenango, L.O. Williams et al. 22038 (US). Izabal: Between Los Amates and Izabal, Sierra del Mico, W.A. Kellerman, 6230 (MO). Quetzaltenango: Mountains above Ostucalco, P. C. Standley 66407 (US); vicinity of Zunil, dry brushy hillside, P.C. Standley 83211 (US).Sololá: Volcan Atitlán, J. Viñals, s.n. (MO). Honduras. Comayagua: vicinity of Siguatepeque, P.C. Standley 56214 (US). El Paraíso: Mansaragua, G. Davidse et al. 35031 (MO). Intibucá: Cerro San Cristóbal, C. Nelson & R. Andino 10605 (MO). Ocotepeque: Nueva Ocotepeque, W.E. Harmon & J.D. Dwyer 4123 (MO). Mexico. Chiapas: Cintalpa: Hacienda Monserrat, C.A. Purpus 467 (MO). Larráinzar, Muctahuitz. Región Los Altos, L. Soto-Pinto 1543 (MEXU). Huixtlán: Chilil, B.Y. López-Santos 217, 218 (MEXU). Tenajapa: In the Paraje of Pahal Ton, D.E. Breedlove 12591 (MEXU). Mapastepec: Reserva El Triunfo, polígono 1, Dry area above Cañada Honda, M. Heath & A. Long 1043 (MEXU). San Cristóbal: 10 km de la carr. San Cristóbal-Ocosingo, Borrego 6 (MEXU); entrada a Zacualpa, 500 m carr San Cristóbal-Comitán, S. Ochoa-Gaona et al. 4258 (MEXU). San Juan Chamula: Los Altos, Bautista Chico, L. Soto-Pinto 1236, 1264 (MEXU); Yalchín, B.Y. López-Santos & F. Martínez 735 (MEXU). Unión de Juárez: en el camino de Talquián a Chiquihuite, E. Martínez et al. 193976 (MEXU). Venustiano Carranza: Ejido “Laja tendida”, km 17 de carr. Venustiano Carranza-Tuxtla Gutíerrez, aprox. 2 km a Flores Magón, A. Miranda S. 1237 (MEXU); G. Davidse 9449 (MO). Nicaragua. Chontales: 3 miles southeast of Juigalpa, route 7, roadside and swampy woods [Seymour series], D.A. Dudey 1602 (MO). Estelí: Mechapa, D.A. Hamblett 992 (MO). Rivas: Southwest of La Virgen and northeast of San Juan del Sur, route 16 where road crossed brook, km 136 [Seymour series], F.C. Seymour1228 (MO); Peñas Blancas, F.C. Seymour1853 (MO). Panama. Chiriquí: Volcán Barú, on road to towers at top; near towers at summit, G. McPherson 15064 (MO); 3 km S of Boquete along Rio Caldera, P.M. Peterson & C.R. Annable 7387 (MO); Steep forested slope to W of Río Caldera, ca. 2 km NW of Bajo Mono (Boquete region), M. Grayum et al. 6450 (MO); Camino de acceso al Parque Nacional Volcán Barú (vertiente oriental), M. Vega & R. Rincon 194 (MO); Baru/Potrero Muleto, G. Davidse & W.G. D’Arcy 10257 (MO); Volcán Chiriquí, A. Weston 12375A (CR); Volcán Chiriquí, A. Weston 6216 (CR); Side of Barú Mt., J.S. McCorkle 156 (US); 8 km NW of Boquete on road to Volcán Barú, slopes above Quebrada Grande, P.M. Peterson & C.R. Annable 7361 (US); Chiriqui Volcano, A.S. Hitchcock 8218 (US); Chiriquí Volcano, A.S. Hitchcock 8206 (US).

Sprawling, slender annuals. Culms 8–30(–50) cm tall, glabrous, filiform, often tufted, freely branching at lower nodes; 0.2–0.5 mm diameter just below the inflorescence; internodes 6–42 mm long. Leaf sheaths (8–)20–44 mm long, glabrous or sparsely pilose along the margins, shorter than the internodes; ligules 0.2–0.8 mm long, a ciliate membrane; apex truncate; margin with a tuft of hairs up to 1 mm long; blades 1–4 cm long, 0.6–1.4 mm wide, flat or loosely involute, often sparsely pilose above, glabrous below. Panicles 4–12 cm long, 1.8–5.0 cm wide, terminal, densely flowered; primary branches 1.5–3.7 cm long spreading and reflexed at maturity up to 90° from the rachises, one per node; pedicels 0.5–3 mm long, glabrous, appressed, erect; nodes 6–13 per panicle. Spikelets appressed to the branches, overlapping; glumes 0.7–1.7 mm long, subequal, glabrous, 1-veined; apex acuminate, often mucronate; the mucro up to 0.5 mm long; lower glumes 0.7–1.5 mm long; upper glumes 0.8–1.7 mm long; lemmas 1.8–2.5 mm long, lanceolate, slender, awned, strongly 3-veined but appearing five-veined, the intermediate “nerves” actually rows of short barbs on top of folded epidermal ridges, sometimes with prominent short hairs (scabers) along the lateral veins, often appearing glabrous without magnification, awns (1–)5–11(–18) mm long, flexuous; callus minutely short pubescent; paleas 1.6–2.4 mm long, narrowly lanceolate, glabrous; anthers 0.3–0.5 mm long, yellowish. Caryopses 0.8–1.8 mm long, narrowly fusiform, brownish. 2n = 20.

Figure 6. 

A–D Muhlenbergia ciliata (Kunth) Trin. A habit B floret C glumes D ligule E–F Muhlenbergia vaginata Swallen E habit F ligule G glumes H floret. A–D drawn from P.M. Peterson & C.R. Annable 4541 (US, WS) E–F drawn from P.M. Peterson & C.R. Annable 4111 (US, WS) both used in Peterson and Annable (1991).

Muhlenbergia ciliata is found throughout México and Central America (Costa Rica, El Salvador, Guatemala, Honduras, México, Nicaragua, and Panama) to Ecuador, Peru, Brazil, Bolivia, and Argentina (Peterson and Annable 1991; Peterson et al. 2001).

Muhlenbergia ciliata is found on moist to dry soils usually beneath taller vegetation, sandy drainages, steep rocky slopes, rock outcrops, and disturbed roadsides in woodlands with Acacia, Agave, Andropogon, Bidens, Baccharis ssp., Bothriochloa, Eupatorium, Melinus minutiflora P. Beauv., Muhlenbergia bryophilus, M. flexuosa, M. rigida, Puya, and Salvia; 1000–2400 m.

Muhlenbergia ciliata can be differentiated from M. tenella in having lemmas with ciliate margins (not ciliate in M. tenella), reflexed and spreading panicles branches (tightly appressed panicle branches in M. tenella), regular, alternating leaf blade insertion (secund in M. tenella) [Peterson and Annable 1991; Peterson and Giraldo-Cañas 2011, 2012].

Muhlenbergia ciliata is closely related to M. pectinata C.O. Goodd. (North America) and M. tenella (Kunth) Trin. (North America, Central America, and Colombia) [Peterson and Annable 1991]. These three species form a strongly supported clade in M. subg. Muhlenbergia (Fig. 1; Peterson et al. 2010b; Peterson et al. 2021).

Costa Rica. San José: J.F. Morales 6707A (MO); Cerro de Piedra Blanca, above Escazú, P.C. Standley 32486 (US); Cord. Talamanca, 14 km S of Division along the Interamerican Highway, roadside through oak forest, road fill, R.W. Pohl & G. Davidse 11616 (US). El Salvador. San Salvador: Volcano of San Salvador, A.S. Hitchcock 8938 (US). Guatemala. Alta Verapaz: Coban, Unter Kiefernwald, H. Von Turckheim 3989 (US). Guatemala: Guatemala city, dry hill, A.S. Hitchcock 9061 (US). Quetzaltenango: km 15.5, M. de Koninck, M. 227 (US). Huehuetenango: San Juan Ixcoy, Sierra de los Cuchumatanes, 3 mi N of San Juan Ixocy on Hwy 9N, P.M. Peterson & C.R. Annable 4689 (MO); Huehuetenango, P.M. Peterson & C.R. Annable 4681 (MO). Sacatepequez: Magdalena, W.A. Archer 3865 (US); Volcano Agua, open ground near Antigua, A.S. Hitchcock 9135 (US); Volcano Agua, A.S. Hitchcock 9136 (US). Totonicapán: San Francisco El Alto, W.E. Harmon 4555 (MO). Zacapa: Forested slopes, Sierra de las Minas, near summit of mountain, between Rio Hondo and Finca Alejandria, J.A. Steyermark 29683 (US). Honduras. Copan: Sta. Rosa de Copan, W.A. Archer 3838 (US). Francisco Morazán: Santa Lucía, Quebrada Hierba Buena, R. Clotter 87 (MO); Tatumbla, Cerro Uyuca, I. Cruz 93 (MO); Tatumbla, Cerro Uyuca, R.W. Pohl & M. Gabel 13414 (MO); Distrito Central, El Hatillo, R.W. Pohl & M. Gabel 13463 (MO); Distrito Central, between El Hatillo and Los Jutes, R.W. Pohl & M. Gabel 13790 (MO); Valle Angeles, R. Ramos 99 (MO); Valle de los Angeles, El Balmoral, C. Román 23 (MO); Drainage of the Rio Yeguare, L. O. Williams 17001 (US); Cerro de Uyuca, along trail from Las Flores to La Labranza, P.C. Standley 27380 (US); San Antonio del Oriente, J.R. Swallen 10916 (US); Mt. Uyuca, J.R. Swallen 11177 (US). Mexico. Chiapas: Cacahoatán: 3 km NE of Huixtla on hwy to Motozintla, W.D. Stevens & E.M. Martínez 25671 (MO). Ocozocoautla de Espinosa: 13 km E of Ocozocoautla on Rte. 190, then N on road to Aguacera, M.J. Huft el al. 2252 (MO). Ixtapa: 1 km W of Ixtapa, F.W. Gould 12713 (ENCB). Jitotol: about 10 mi NE of Bochil on Hwy 195, J.R. Reeder & C.G. Reeder 6075 (ARIZ, ENCB, MO); 4 km SE of Jitotol along road to Bochil, G. Davidse et al. 29663 (MEXU); Slope, 10 km N of Jitotol near Rio Hondo, D.E. Breedlove & G. Davidse 55155 (CAS); Santa Isabel near Jitotol, A. A. Beetle M-4091 (MEXU). Ruíz: camino de El Zopilote a San Juan Corapan, A. Ramos 291 (MEXU). Teopisca: Belem, 8 km NW of Teopisca along hwy. to San Cristobal de las casas, G. Davidse et al. 29771 (MEXU); 8.2 mi SE de San Cristóbal de las Casas, P.M. Peterson & C.R. Annable 4679 (US); 10.5 mi SE of San Cristobal de las Casas, P.M. Peterson & C.R. Annable 4717 (ENCB, MEXU, US); Venustiano Carranza: 3 mi S of Aguacatenango along rd to Pinola Las Rosas, D. E. Breedlove & P. H. Raven 13458 (US). Nicaragua. Estelí: Darailí, W.D. Stevens 15913 (MO). Panama. Chiriquí: vicinity of Boquete, from Boquete to 3mi N, W.H. Lewis et al. 332 (MO).

Caespitose annuals. Culms 35–90 cm tall, erect to somewhat decumbent and rooting at the lower nodes, smooth and glabrous below the nodes; internodes 1–2 mm diameter, glabrous or slightly scabrous, often reddish. Leaf sheaths shorter than the internodes, scabrous or smooth; prophylls 2–3 cm long, prominent, bifid; ligules 0.7–1 mm long, membranous, thick, apex truncate; blades 9–22 cm long, 5–9 mm wide, flat, scabrous, auriculate near base, the auricles 1–2 mm long, ciliate, clasping. Panicles 10–22 cm long, 1–2.5 cm wide, cylindrical, solitary, exserted or included in the sheaths below; primary branches 1–3.5 cm long, ascending mostly appressed, spreading up to 70° from the culm axis with dense fascicles of florets; pedicels 0.1–0.3 mm long, the spikelets arising just above the sterile spikelets or bristles, the bristles 3–5 mm long. Spikelets (fertile) 1.8–2.8 mm long; glumes 0.7–1.5 mm long, subequal, oblong to ovate, 1-veined, awned, the awns 1.5–4 mm long; lemmas 1.8–2.6 mm long, lanceolate, scabrous 3-veined, awned, the awns 10–24 mm long, straight, callus hairy, the hairs 0.6–1 mm long; paleas 1.8–2.8 mm long, slightly longer than the lemma, apex bidentate; stamens 2, anthers 0.8–1 mm long, often purple. 2n = 80 (Pohl and Davidse 1971).

The species is endemic to Costa Rica and is known from Provincias Alajuela, Heredia, Puntarenas, and San José (Peterson et al. 2001; Morales 2003).

Muhlenbergia diandra occurs on dry to moist roadsides and disturbed sites on the margins of humid forests; 500–1800 m.

Muhlenbergia diandra differs from M. pereilema in having wide leaf blades 4–9 mm long (2–3 mm wide in M. pereilema), lemmas with straight awns (flexuous in M. pereilema), and chromosome number (Davidse and Pohl 1992; Morales 2003). This species probably forms a clade with M. beyrichiana Kunth, M. pereilema, and M. plumiseta Columbus within M. subg. Muhlenbergia (Peterson et al. 2021).

Muhlenbergia beyrichiana is only known to occur in Brazil, Ecuador, and Peru as determined here. Earlier, it was reported in México and Central America but these are in error (Espejo Serna et al. 2000; Lægaard and Peterson 2001; Peterson et al. 2001, 2018).

Costa Rica. Hoffmann 465 (US); Río Tiliri, A. Tonduz 3121 (MO, CR). Alajuela: Poás, Carrillos de Poás, A.M. Brenes 14606 (CR, US); Naranjo, puente sobre el Rio Colorado donde el Tropical Bungee, B. Hammel 20587 (INB, CR); Naranjo, open areas on upper slopes of Cerro Espíritu Santo, 1–3 km SW of Naranjo, A.S. Weston et al. 3852 (CR). Heredia: Puente de Mulas, S of San Antonio, Canyon of the Río Virilla, R.W. Pohl & G. Davidse 11482 (MO, CR). Puntarenas: Monteverde, 10 km S Monteverde on road to Inter-American Highway, area of spring, W. Haber & W. Zuchowski 9639 (MO, INB); Cordillera de Tilarán, 10 km SW Santa Elena on road from Monteverde to Inter American Highway, dry ridges and cut banks, W. Haber & W. Zuchowski 10305 (MO, INB, US). San José: San Francisco de Guadalupe, A. Tonduz 9817 (CR, MO, US); Mora, Llano Grande Puriscal, O. Jiménez 890 (US, CR); Orillas del camino a San Juan, O. Jiménez 161 (US); vicinity of Santa Maria de Dota, P.C. Standley 41769 (US), 43224 (US), 44066 (US); Bordes del rio Torres, San Francisco de Guadalupe, A. Tonduz 7198 (US).

Caespitose perennials. Culms 100–180 cm tall, erect, glabrous to pubescent below the nodes; internodes glabrous. Leaf sheaths 8–42 cm long, longer than basal internodes, glabrous, the keels prominent, sometimes coiled to shredded below, basal sheaths compressed-keeled; sheath auricles 6–26 mm long, on lower portions and to 6.4 cm above, apex acuminate; ligules 4–15 mm long, membranous, apex finely lacerate sometimes almost to the base; blades 18–90 cm long, 2–7 mm wide, flat or folded, scaberulous to scabrous on both sides, the margins and keel saw-toothed. Panicles 35–70 cm long, 4–15 cm wide, densely-flowered, oblong, sometimes lax near apex, greenish-brown, sometimes reddish-purple; primary branches 2–15 cm long, without spikelets near the base, appressed to loosely spreading up to 60° from the rachises; pedicels 0.2–4 mm long, glabrous to scaberulous. Spikelets 1.5–2.8(–3) mm long, erect, greenish-brown, to reddish-purple; glumes 1.2–2.8 mm long, longer, as long or a little shorter than the lemma, subequal, oblong to narrowly-oblong, faintly 1-veined, hyaline, glabrous to scaberulous, usually with faint, widely scattered hairs, the hairs less than 0.1 mm long, apex acute to acuminate; upper glumes rarely mucronate, the mucro to 0.4 mm long; lemmas 1.4–2.7 mm long, lanceolate to linear-lanceolate, awned, glabrous or sometimes the margins on the lower 1/3 pubescent, the hairs to 0.2 mm long, rarely the lower 1/3 with scattered hairs, apex acute, minutely bifid, the teeth to 0.5 mm long, the awn 4–16 mm long, flexuous, often reddish-purple near base; callus usually short pilose; paleas 1.3–2.7 mm long, glabrous or with few hairs between the veins on the lower 1/3, apex acute; anthers 1.2–1.5 mm long, yellowish, sometimes reddish tinged. Caryopses not seen.

Figure 7. 

A–E Muhlenbergia macroura (Kunth) Hitchc. A habit B ligule C glumes D floret E stamens, pistil, and lodicules F–I Muhlenbergia distichophylla (J. Presl) Kunth F ligule G glumes H floret I stamens pistil, and lodicules. A–E drawn from P.M. Peterson & C.R. Annable 5970 (US) F–I drawn from L.O. Williams, A. Molina R. & T.P. Williams 22309 (US) and F.W. Gould 12666 (US).

The species ranges from central México in Jalisco, Guerrero, México, Oaxaca, and Chiapas to Guatemala (Peterson et al. 2001).

Muhlenbergia distichophylla occurs in open pine-oak forests and tropical deciduous forests on rocky slopes, canyons, and ravines; 400–2000 m.

This species can be separated from other members of M. subg. Trichochloa in having long, acuminate sheath auricles up to 6.4 cm long on the culm, usually greater than 2 cm long on the lower innovations (Herrera Arrieta and Peterson 2018). Muhlenbergia distichophylla, a member of M. subg. Trichochloa, has been found in an unsupported clade with nine other species, distributed in North America (Eastern USA, western USA, México) and Central America [M. lindheimeri Hitchc., M. setifolia Vasey, M. dubia E. Fourn., M. gypsophila Reeder & C. Reeder, M. x involuta Swallen, M. reverchonii Vasey & Scribn., M. sericia (Michx.) P.M. Peterson, M. expansa (Poir.) Trin. and M. capillaris] (Fig. 1; Peterson et al. 2021).

Guatemala. Escuintla: Rio Coyolate, near Highway CA-2, thickets on banks of Río Coyolate, W.E. Harrmon & J.A. Fuentes 4721 (MO). Huehuetenango: On dry bank about 5 km. west of Huehuetenango, L.O. Williams, A. Molina R. & T.P. Williams 22309 (US); Sierra de los Cuchumatanes, P.C. Standley 81480 (US). Mexico. Chiapas: Escuintla, E. Matuda 319 (MEXU); Monte Ovando, E. Matuda 322 (MO).

México, Porto Pedro, Karwinsky 1393 (lectotype, designated here: LE-TRIN-1497.01!; isolectotypes: LE-TRIN-1497.02!, LE-TRIN-1497.03!, US-84831 fragm. ex LE-TRIN!, W-0002564!).

Sprawling annuals. Culms 16–50 cm tall, decumbent, rooting at the lower nodes; nodes retrorsely pilose; internodes smooth or scabridulous. Leaf sheaths 1.5–8.5 cm long, sparsely or densely pilose, hairs to 3 mm long, papillose-based; ligules 0.5–0.8 mm long, membranous, apex truncate, erose; blades 2–6 cm long, 1.5–4 mm wide, flat, bases distinctly narrowed to the junction with the sheath, surfaces scabridulous and sparsely pilose, hairs papillose-based. Panicles 6–10.5 cm long, 2.0–4.5 cm wide, open; primary branches 0.8–3.5 cm long, secund, spreading at right angles or somewhat reflexed usually lying to one side with 2–5 spikelets; secondary branches not developed; pedicels 1–5 mm long, scabrous or shortly pilose, hairs papillose-based; disarticulation at the base of the primary branches where there is a weak and contorted stipe. Spikelets 4–8 mm long, dimorphic with respect to the glumes, proximal spikelets on each branch almost sessile; glumes of proximal spikelets on each branch subequal, 0.2–0.7 mm long, orbicular, truncate, often erose or irregularly toothed, unawned; glumes of distal spikelets on each branch markedly unequal; lower glumes to 8 mm long, 1-veined, acute, usually awned, awns 0.5–3 mm; upper glumes orbicular, acute, sometimes awn-tipped; lemmas 4.0–7.6 mm long, linear to broadly lanceolate, light greenish, smooth or scabrous, usually with greenish veins, apices acuminate, awned, awns 6–19 mm long, usually straight, scabrous; paleas 3.7–6.8 mm long, narrowly lanceolate, coarsely papillate or almost smooth, 2-keeled, the veins prominent, scabrous, greenish, sometimes extending as minute awns, acuminate; anthers 0.4–0.8 mm long, yellowish. Caryopses 1.8–3 mm long, oblong-ovoid, flattened, brownish. 2n = 20.

Figure 8. 

A–D Muhlenbergia diversiglumis Trin. A habit B floret C glumes D ligule E–H Muhlenbergia implicata (Kunth) Kunth E habit F floret G glumes H ligule. A–D drawn from P.M. Peterson & C.R. Annable 4158 (US, WS). E–H drawn from P.M. Peterson & C.R. Annable 4598 (US, WS).

The species is native to North America, Central America, Colombia, Venezuela, Ecuador, Peru, and Argentina (Peterson and Annable 1991; Peterson et al. 2001).

Muhlenbergia diversiglumis grows on moist cliffs, along water courses, sandy slopes, and road cuts, primarily in moist shaded environments of broadleaf evergreen forests and pine-oak forests; 600–2500 m.

Muhlenbergia diversiglumis can be differentiated from M. ciliata, M. microsperma, and M. romaschenkoi in having secund panicles (versus not secund in the latter three species) with each primary branch consisting of 2–5 dimorphic spikelets where the proximal spikelets have short orbicular glumes less than 1 mm long, and the distal spikelets have glumes up to 8 mm long (Peterson and Annable 1991; Giraldo-Cañas and Peterson 2009).

Muhlenbergia diversiglumis is a member of M. subg. Muhlenbergia and is sister to M. alamosae Vasey, a species from México (Peterson et al. 2021).

Costa Rica. Alajuela: 1 km S of Carrizal, R.W. Pohl & G. Davidse 11500 (US). Cartago: San Ramón, E of San José, open grassy roadside, R.W. Pohl & Mark Gabel 13678 (MO); Road crossing of Río Reventado between Llano Grande and Tierra Blanca, gravelly river banks, R.W. Pohl & M. Lucas 13092 (MO). Heredia: Porrosati, 2 km by road N of Porrosati, R.W. Pohl & M. Gabel 13672 (MO); Carrizal, H. Pittier 786 (US); Barba, cultures a La Esmeralda, A. Tonduz 1692 (US). Puntarenas: Cordillera de Tilarán, W. Haber & W. Zuchowski 10891 (MO, INB). San José: Aserri, Cuenca del Pirris-Damas, Cerros Caraigres, Falda S, Quebrada Concha, en el camino viejo a Bijagual, J.F. Morales 5913 (MO, INB); León Cortés Castro, Z.P. Caraigres, Cuenca del Pirris-Damas, Fila El Alto. J.F. Morales 5933 (MO, INB), Pérez Zeledón, P. N. Chirripó camino a Chirripó a orilla del sendero, Cuenca Térraba- Sierpe, E. Alfaro, et al. 966 (CR, INB); Hacienda La Esperanza, La Palma, O. Jiménez 963 (CR). San Francisco de Guadalupe, cultivos, O. Jiménez s.n. (US); Jardines de San Francisco de Guadalupe, H. Pittier 9068 (US); 11 km N of San Isidro de El General along the Carretera Interamericana, R.W. Pohl & G. Davidse 11570 (US); Between Aserrí and Tarbaca, P.C. Standley 41352 (US); vicinity of Santa María de Dota, moist forest, P.C. Standley 41831 (US); vicinity of Santa María de Dota, P.C. Standley & J. Valerio 43215 (US); La Verbena de Alajuelita, A. Tonduz 9084 (US). El Salvador. Ahuachapán: Parque Nacional El Imposible: San Benito, al S del enganche de los ríos Venado y Escalares, E. Sandoval & F. Pérez 1470 (MO). San Salvador: Volcán San Salvador, el Boqueron, disturbed secondary forest bordering pasture and cafetale, A. Monro et al. 2179 (MO); Volcano of San Salvador, A.S. Hitchcock 8929 (US); Volcano of San Salvador, A.S. Hitchcock 8939 (US); Volcano of San Salvador, A.S. Hitchcock 8940 (US). Guatemala. Alta Verapaz: near San Cristóbal Verapaz, wet thickets and second growth forest, L.O. Williams et al. 42228 (MO); Coban, H. Von Turckheim s.c. (US); Coban, Maisfeldem. unter Kiefernald, H. Von Turckheim 3988 (US). Guatemala: Guatemala City, A.S. Hitchcock 9049 (US). Huehuetenango: 21 mi NW of Huehuetenango on Pan American Hwy. 1, P.M. Peterson & C.R. Annable 4682 (MO). Jalapa: Mountains along the road between Jalapa and Paraiso, P.C. Standley 77358 (US). Jutiapa: Volcan Chingo, W.C. Shannon 3699 (US). Quiche: Chichicastenango, 4 km S of Chichicastenango, steep wooded hillside dominated by pine and oak, W.E. Harmon 4613 (MO). San Marcos: Wet mountain forest near Aldea Fraternidad, between San Rafael Pie de la Cuesta and Palo GPoales, west facing slope of the Sierra Madre Mountains, L.O. Williams et al. 25993; L.O. Williams et al. 25971 (US); Montane cloud forest area on outer slopes of Tajumulco Volcano, Sierra Madre Mountains about 8–10 km west of San Marcos, L.O. Williams et al. 26928 (US). Honduras. Francisco Morazán: Tatumbla, Cerro Uyuca, R.W. Pohl 12493 (MO); San Antonio del Oriente, J.R. Swallen 10975 (US); forest with with Pinus and Liquidambar entre Peña Blanca y Lo de Ponce, L.O. Williams & A. Molina R. 17126 (US). Mexico. Chiapas. Angel Albino Corzo: slopes of Río Cuxtepec. along stream below Finca Cuxtepec, D.E. Breedlove & J.L. Strother 46692 (CAS, MO). Motozintla: Sierra Madre de Chiapas 5 mi NW of Motozintla de Mendoza on road to El Porvenir, P.M. Peterson & C.R. Annable 4707 (ENCB, MEXU, US, MO); W side of Cerro Mozotal, 11 km NW of the junction of the road to Motozintla along the road to El Porvenir and Siltepec, D.E. Breedlove & B.M. Bartholomew 55714 (CAS, MO). Zinancantán: Hwy 190, 10 mi SE of the road to Simojovel paraje of Granadia, D.E. Breedlove 7276 (ENCB).

Costa Rica, San José, Cerro de Buena Vista, 3000m, 19 Jan 1891, H. Pittier 3372 (lectotype, designated here: G-00192109 [image!]; isolectotypes G-00192054 [image!], US-577110!).

Caespitose and sprawling perennials. Culms 25–45 cm long, densely branched near base, decumbent and rooting below; internodes glabrous. Leaf sheaths much overlapping, flabellately arranged, glabrous, margins membranous, old sheaths flattened and papery; ligules (2.5–)3–8 mm long, membranous, hyaline, margins entire, decurrent, apex acute; blades 2–5 cm long, 1–2 mm wide, flattened to folded or involute, mainly basal, strongly ridged above with short stiff hairs, scabrous below. Panicles 3–9(–15) cm long, 2–3 cm wide, few-flowered, narrow, short-exserted, dark green; primary branches mostly 1–2 cm long, sometimes purplish with loosely appressed and ascending branches, spreading up to 30° from the culm axis, central axis slightly flattened, 2-ribbed, scabrous; pedicels 0.2–1 mm long, scabrous. Spikelets 3–4 mm long, erect, plumbeous to dark olivaceous; glumes 1.2–2 mm long, subequal, scabrid, apex obtuse to truncate, unawned; lower glumes 1.2–1.6 mm long, ovate, usually 1-veined, sometimes unveined; upper glumes 1.6–2 mm long, half as long as the lemma, oblong-obovate, usually 3-veined, but sometimes very faint, 2 or 3-toothed, the teeth 0.3–0.6 mm long, about 1/3 the length of the glume; lemmas 3–4 mm long, lanceolate, pilose below and along margins, the hairs mostly less than 1 mm long, the callus hairy, apex awned, the awns 4–8 mm long, flexuous, scabrous, olive-green, arising from a bifid apex, the teeth up to 0.5 mm long; paleas 3–4 mm long, as long as the lemma, olive-green, scabrous; anthers 1.8–2.1 mm long, fusiform, purple.

Figure 9. 

A–E Muhlenbergia flabellata Mez. A habit B ligule C glumes D floret E floret F–J Muhlenbergia montana (Nutt.) Hitchc F habit G inflorescence H glumes I upper glume J florets. A, B, D, E drawn from W.C. Burger & L. Gomez P. 8309 (US-2695054) C drawn from G. Davidse 24971 (US-3014559) F–J drawn from A.S. Hitchcock 3143 (US-995116).

The species is endemic to Costa Rica and Panama (Peterson et al. 2001).

Muhlenbergia flabellata occurs in páramos between 3100–3500 m often associated with Chusquea subtessellata Hitchc., Hypericum, ssp., Comaristaphylos arbutoides Lindl., Garrya laurifolia Hartw. ex Benth., and Buddleja nitida Benth.

Muhlenbergia flabellata is a member of M. subg. Clomena and within this clade it is sister to M. quadridentata, a species primarily restricted to higher elevations that is common in México and extends into Guatemala (Peterson et al. 2021). Muhlenbergia flabellata can be separated from M. quadridentata in having short leaf blades 2–5 cm long (5–15 cm long in M. quadridentata), short upper glumes 1.6–2 mm long [versus (3–)3.2–4 mm long in M. quadridentata], and paleas scabrous throughout (versus pilose on the proximal ½ in M. quadridentata) [Peterson et al. 2007b; Herrera Arrieta and Peterson 2018].

Costa Rica. Cartago: Paraíso, Cerro de la Muerte, Cordillera de Salamanca, near summit of Cerro Sátira, S. Horn 35 (CR); Paraíso, Cerro de la Muerte, M. Kappelle et al. 2377 (CR). Pérez Zeledón: R. F. Los Santos, Cerro Bubis, A. Estrada et al. 2769 (CR); P. N. Chirripó, parte superior (norte) del Valle de los Conejos, J. Gómez 5339 (CR); R.F. Los Santos Alrededores de las torres de TV, cerro Buenavista, L. Gómez 6354 (CR); P. N. Chirripó, alrededores de refugio, parte inferior del valle de los Conejos, J. Gómez-L. 4503 (USJ); P. N. Chirripó, Cordillera de Salamanca, S facing slope of the Valle de los Conejos, about 1 km S of Cerro Nuevo, S. Horn 59 (CR); P.N. Chirripó, Valle de los Conejos, R. Ocampo 1466 (CR); P.N. Chirripó, Valle de los Conejos, R. Ocampo 1489 (CR); Rivas, A. Rodríguez 6422 (INB); Pérez Zeledón, Rivas, A. Rodríguez 6541 (INB); P.N. Chirripó, refugio Los Crestones, G. Vargas et al. 340 (USJ); disturbed paramo, Cerro de la Muerte, R. Chazdon 447 (CR); Cordillera de Talamanca, Cerro de la Muerte, summit of Cerro Buvis, R.W. Pohl & G. Davidse 11621 (US); Direct line from Hotel La Georgina to Cerro Frio of the Cerro Buenavista complex (Cerro de la Muerte), area with television and radio towers, G. Davidse 24971 (US, MO); Open paramo formation with stands of Chusquea bamboo 1–2.5 m tall and areas of short-burned forest and original forest 5–15 m tall in protected sites, along the trail to the Valle de los Leones and the lower part of theValle de los Conejos along the upper Rio Talari, W. Burger & L.D. Gomez 8309 (US). San Jose: W.C. Burger & R. Liesner 7467 (MO); Chirripó, G. Davidse & R. W. Pohl 1541 (MO); Buenavista, A. Jiménez 2666 (MO); Parque Nacional Chirripó, Páramo near Albergues de los Crestones, along Río Talari near trail to Valle de los Conejos, J. G. Pruski et al. 3904 (MO); Buenavista, A. Weston 5846 (MO); Cerro Buenavista, P.M. Peterson, S. Lobo, J. Sánchez & R. Chacón 22855 (CR, US); P. N. Chirripó Open paramo formation with stands of Chuquea bamboo 1–2.5 m tall on slopes and in the valley, short grasses and very short (30 cm)shrubs on the exposed ridges, Valle de los Conejos (upper río) Talari and trails to Cerro Chirripó and the Valle de Los Lagos, W.C. Burger & R. Liesner 7353 (CR); P. N. Chirripó, A. Chaverri et al. 1026 (CR); P. N. Chirripó Valle de los Conejos, A. Chaverri et al. 1172 (CR), Panama. Bocas del Toro: Fábrega, A. Weston 10190 (MO).

Caespitose slender annuals. Culms 15–50(–70) cm tall, mostly branched below and lax spreading or erect, scaberulous to short-pubescent below the nodes, the nodes 0.4–0.6 mm in diameter just below the inflorescence; internodes 3–9.5 cm long. Leaf sheaths 1.4–9.1 mm long, mostly shorter than the internodes, glabrous to scaberulous; ligules 1–2.5(–3) mm long, membranous to hyaline; blades 3–5(–10) cm long, 1–2.5 mm wide, flat or loosely involute, short pubescent above and mostly glabrous below, margins scabrous. Panicles 7–12(–26) cm long, 3–5(–9.2) cm wide, open, diffuse, with the peduncle included in the sheath, axis scaberulous; primary branches ascending and spreading up to 90° from the culm axis; pedicels 7–11 mm long, capillary, flexuous, delicate, smooth, nodding to reflexed, mostly purplish, thickened just below the spikelet. Spikelets 2.5–3(–4) mm long, purple; glumes 0.2–0.6 mm long, unequal, glabrous, apex truncate to broadly obtuse, often erose; lower glumes 0.2–0.4 mm long, veinless; upper glumes 0.3–0.6 mm long, 1-veined; lemmas 2.5–3(–4.5) mm long, 3-veined, appearing 5-veined because the margins are folded with rows of barbs that resemble extra veins, narrowly lanceolate, scabrous, apex awned and 2-toothed, the teeth to 1 mm long, the awns 8–26 mm long; callus with whitish appressed or spreading pubescence, the hairs up to 0.7 mm long; paleas 2.9–4 mm long, narrowly lanceolate, glabrous, apex acuminate; anthers 0.4–0.9 mm long, purple. Caryopses 1.8–2.7 mm long, narrowly fusiform, brownish. 2n = 20 (Peterson and Annable 1991).

Muhlenbergia implicata ranges from México to Central (Costa Rica, El Salvador, Guatemala, Honduras, México, Nicaragua, and Panama) and South America (Peterson and Annable 1991; Peterson et al. 2001). In Mexico, M. implicata is known from Chiapas and Campeche (Sanchez-Ken 2018).

This species grows on cliffs, canyon walls, and dry to rocky roadsides in open vegetation associated with oak-pinyon-juniper woodlands; (5–) 600–2550 m.

Muhlenbergia implicata is a member of M. subg. Pseudosporobolus and is sister to a central Mexican endemic, M. seatonii Scribn. (Fig. 1; Peterson et al. 2021).

Costa Rica. Alajuela: San Ramón, San Pedro de San Ramón, A.M. Brenes 14966 (CR); San Ramón, Colinas de San Pedro de San Ramón, A.M. Brenes 16704 (CR); San Ramón, San Juan cerca de San Ramón, A. M. Brenes 16852 (CR); Orillas de camino, O. Jiménez 44 (US); Canoas, O. Jiménez s.n. (US); 4 km NW of San Jose, Dry road bank in coffee plantation, R.W. Pohl & G. Davidse 11366 (US); 1 km S of Carrizal. Open roadside in coffee plantation, R.W. Pohl & G. Davidse 11501 (US). Cartago: R.W. Pohl & M. Lucas 13152 (MO). Heredia: M. Grayum 9600 (MO). San José: R.W. Pohl & M. Lucas 12997 (MO); Puriscal, 10 km antes de Puriscal, R. Ocampo1123 (CR); San José, J.J. Cooper 5996 (US); along railway, A.S. Hitchcock 8511 (US); San José, A.S. Hitchcock 8459 (US); San Francisco de Guadalupe, sobre paredón, O. Jiménez 5 (US); 13 km N of San Isidro de El General along the carretera interamericana, busy roadside in forest, R.W. Pohl & G. Davidse 11628 (US); vicinity of Santa Maria de Dota, in potrero, P.C. Standley 41586 (US); vicinity of Santa Maria de Dota, in cafetal, P.C. Standley 41608 (US); vicinity of Santa Maria de Dota, brushy slope, P.C. Standley & J. Valerio 43218 (US). El Salvador. La Libertad: Volcán San Salvador, P. Bernhardt & E.A. Montalvo 79 (MO); Volcano of San Salvador, A.S. Hitchcock 8948 (US). Guatemala. Alta Verapaz: Coban, H. Von Turckheim 3990 (US); Coban, H. Von Turckheim s.n. (US). Chimaltenango: along road from Chimaltenango to San Martin Jilotepeque, P.C. Standley 57892 (US); along road between Chimaltenango and San Martin Jilotepeque, oak forest, P.C. Standley 80877 (US). Guatemala: Guatemala City, A. S. Hitchcock 9030 (US); Guatemala City, A.S. Hitchcock 9013 (US); Barranca north of Guatemala City, W. Popenoe 736 (US). Huehuetenango: Sierra los Cuchumatanes. 8 mi N of Huehuetenango on Pan American hwy CA 1, slopes above Rio, Quercus forest, P.M. Peterson & C.R. Annable 4701 (MO, US); About Laguna de Ocubila, east of Huehuetenango, dry open bank, P.C. Standley 82631 (US); Pine-oak forest region, canyon at head of Rio Chixoy, about 10 km southwest of Huehuetenango, L.O. Williams et al.22548 (US); Barranco in oak forest near Ocubila, 10 km west of Aguacatan, L.O. Williams & T.P. Williams 21785 (US); Open, wet, boggy meadow 3 km S of Huehuetenango, L.O. Williams et al. 22105 (US). Jalapa: Jalapa, P.C. Standley 76829 (MO); vicinity of Jalapa, damp thicket, P.C. Standley 76399 (US); vicinity of Jalapa, P.C. Standley 76410 (US). Sacatepequez: Magdalena, W. A. Archer 3867 (US); Above Pastores, sand along stream, P.C. Standley 60846 (US). Mountains near Santa Maria, Weatherwax 173 (US). Honduras. El Paraíso: Guinope, drainage of the Rio Yeguare, en el pantano, llanos y potreros empantanados de Galeras y Llano de Lizapa, A. Molina 3367 (MO); Cumbre on Yuscaran road, rocky slope in pine forest, P.C. Standley 29360 (US). Francisco Morazán: Distrito Central, Colonia Miraflores, A. Díaz 244A (MO); San Antonio de Oriente, Las Mesas, R.W. Pohl 12521 (MO); Distrito Central, between El Hatillo and Los Jutes, R.W. Pohl & M. Gabel 13791 (MO); Las Casitas, L. Villela 129 (MO); Cerro la Uyuca, La Labranza and vicinity, along trail to summit, moist thicket, trail to La Labranza, P.C. Standley 28299 (US); vicinity of Suyapa, J.R. Swallen 11271 (US); San Antonio del Oriente, J.R. Swallen 10915 (US); Drainage of the Rio Yeguare, L.O. Williams 16905 (US). Mexico. Campeche: Campeche: 2.5 km al oeste de San Francisco Kobén, 5m, 20 Sep 2003, C. Gutiérrez Báez 7909 (MEXU-1338596). Chiapas: 10.5 mi SE of San Cristobal de las Casas, P.M. Peterson & C.R. Annable 4721 (ENCB, MEXU, US); near San Cristóbal, A.A. Beetle 3963 (MEXU); W edge of San Cristóbal de las Casas, D.E. Breedlove 53975 (NY); 2 mi S of Tuxtla Gutiérrez along road to Villa Flores, D.E. Breedlove & P.H. Raven 13357 (US). La Trinitaria: 20 km S of La Trinitaria, D.E. Breedlove & G. Davidse 55055 (CAS, MO); 6–7 km S of La Trinitaria, G. Davidse et al. 29972 (MO). Ixtapa: near the Zinacantán Paraje of Muctajoc, D.E. Breedlove & G. Davidse 54021 (CAS, MO); near Ixtapa, D.E. Breedlove & G. Davidse 54298 (CAS, MO); near the Zinacantán Paraje of Muctajoc, D.E. Breedlove & G. Davidse 53991 (CAS, MO). Pueblo Nuevo Solistahuacán: Clínica Yerba Buena, 2 km NW de Pueblo Nuevo Solistahuacán, D.E. Breedlove & P.H. Raven 19825 (ENCB, TAES, US). San Cristobal de las casas: S end of the valley of San Cristóbal Las Casas, D.E. Breedlove & G. Davidse 54374 (CAS, MO). Teopisca: N of Teopisca, D.E. Breedlove & G. Davidse 54770 (CAS, MO); 7 km NW of Teopisca along hwy. to San Cristobal de las Casas, G. Davidse, M. Sousa, O. Téllez, E. Martinez & J. Davidse 29826 (MO, US); 6 km W of Teopisca, F.W. Gould & S.L. Hatch 14420 (US). Nicaragua. Estelí: Las Pilas, P.P. Moreno 22341 (MO). Jinotega: Mountain slopes and wooded ravines of Cordillera Central de Nicaragua, 2–4 km S of Jinotega, grass in clearing, L.O. Williams et al. 23554 (MO); Jinotega, L. O. Williams et al. 27924 (MO). Panama. Chiriquí: G. Davidse & W.G. D´Arcy 10382 (MO); J.A. Duke 9197 (MO); M. Nee 14135 (MO).

Colombia, Cauca, Popayán, F.C. Lehmann 1267 (holotype: L-0044745 [image!]; isotypes: K-000308934 [image!], NY-00381489 [image!], US-72979 fragm. ex L!, US-72977 fragm. ex L!, US-72978 fragm. ex K!).

Caespitose perennials covered in old sheaths. Culms (72–)90–130(–167) cm tall, erect, compressed-keeled near base, glabrous to scaberulous below the nodes; internodes glabrous. Leaf sheaths tightly imbricate below, golden yellow with age, not basally shredded; ligules 10–25 mm long, membranous, somewhat firm below; apex acuminate; sheath auricles lacking or rarely rudimentary up to 0.1 mm long; blades 20–40 cm long, 1–4 mm wide, flat to folded, scaberulous to scabrous, apex becoming narrow and threadlike. Panicles 19–45 cm long, 3–6 cm wide, dense and narrow, golden, golden-brown or purplish-green; primary branches mostly 3.5–14 cm long, and up to 19 cm long below, ascending and appressed, naked below; pedicels 0.7–3.5 mm long, scaberulous. Spikelets 2.5–3.8 mm long, erect; glumes 2.5–3.8 mm long, about equal, sometimes the upper glume, both longer than the lemmas, 1-veined, occasionally 2 or 3-veined, hispid; apex obtuse to dentate, usually mucronate, the mucro up to 0.3 mm long; lemmas 2–3.3 mm long, pilose along the veins and margin on lower 2/3, awned from just below the apex; apex obtuse, the awns 10–20 mm long, flexuous and minutely scabrid; callus with short hairs; paleas 2.3–3.2 mm long, usually shorter than the lemma, hairy between the veins on the lower ½; anthers 1.4–1.6 mm long. Caryopses 1.2–1.3 mm long, fusiform, glabrous, light brown. 2n = 20 +2b (Reeder 1994).

Figure 10. 

A–F Muhlenbergia versicolor Swallen A habit B ligule C glumes D lemma E palea F stamens, pistil, and lodicules G–K Muhlenbergia lehmanniana Henrard G habit, H ligule I glumes J floret K stamens, pistil, and lodicules. A drawn from G.B. Hinton 2324 (US-1840807) B–F drawn from G.B. Hinton 14808 (US-1842654) G–K drawn from H. Pittier 1468 (US).

Muhlenbergia lehmanniana ranges from Central America in Costa Rica, Honduras, and Panama to South America in Columbia, Ecuador, and Venezuela (Giraldo-Cañas and Peterson 2009).

This species occurs on gentle to steep slopes, ravines, gravelly sites, and disturbed sites in humid tropical forests with Pinus and Quercus; 600–2200 m.

Muhlenbergia lehmanniana is morphologically similar to M. máxima Lægaard & Sánchez Vega, a Peruvian endemic. However, M. lehmanniana differs from M. máxima in having longer lemmatal awns (12–20 mm long versus 4–9 mm long in M. máxima) and longer ligules (10–25 mm long versus 3–5 mm long in M. máxima) [Peterson et al. 2018].

Muhlenbergia lehmanniana is a member of M. subg. Trichochloa (Peterson et al. 2010b; 2021). There is not much genetic variation among all members of M. subg. Trichochloa in Peterson et al. (2018, 2021).

Costa Rica. Basamento de Fila Lleskila, L.D. Gómez et al. 23244 (MO). Alajuela: San Ramón, San Pedro de San Ramón, cerca del Río Barranca, A.M. Brenes 21415 (CR); 6 km S of Los Cartagos by road, R.W. Pohl & G. Davidse 11504 (US); 12 km SW of San Ramon along the Carretera Interamericana, R.W. Pohl & G. Davidse 11511 (US). Cartago: El Guarco, F. Solís 618 (CR); Oreamuno, in Monte Irazú, A.S. Oersted 14012 (US), 14471 (US); Paraíso, Las Concavas, C.H. Lankester 676 (US); 5 km E of Paraíso, R.W. Pohl & G. Davidse 11390 (US). Puntarenas: Coto Brus, Z.P. Las Tablas. Cuenca Terraba-Sierpa, el tajo, colectando a orillas del camino, E. Alfaro 2593 (MO); Coto Brus, Z.P. Las Tablas, Cuenca Térraba-Sierpe, Cerro Pando, colecta en bosque y orillas de potreros E. Alfaro et al. 925 (MO); Coto Brus, Z.P. Las Tablas. Cuenca Térraba-Sierpe, Cerro Pando, colecta en bosque y orillas de potreros, E. Alfaro et al. 931 (MO); Coto Brus, Z.P. Las Tablas, E. Alfaro 925 (INB); Coto Brus, Z.P. Las Tablas, E. Alfaro 931 (INB); Coto Brus, Finca Cafrosa, 2.5 km al E del Progreso, Cerro Pelón, E. Alfaro 2593 (INB); Buenos Aires, Ujarras, El Carmen, Sabanas de Murur Bisuk, estribaciones de Cerro Amu, G. Herrera 3593 (INB); Buenos Aires, P.N. La Amistad, Cuenca térraba-Sierpe, Violey, Sabanas Esperanzas, L. González & A. Garita 1196 (MO); Buenos Aires, R.I. Ujarrás-Salitre-Cabagra, Cuenca Térraba-Sierpa, Salitre, Cerro Sipar, L. González & A. Garita 1215 (MO); Monteverde, 10 km S Monteverde on road to InterAmerican Highway, area of spring, W. Haber & W. Zuchowski 9660 (MO); Golfito, P.N. Corcovado, Península de Osa, Dos Brazos de Río Tigre, Jiménez, Cuenca superior del Río Madrigal, margen derecha, G. Herrera & C. Fallas 4710 (MO, INB); Buenos Aires, Ujarrás, El Carmen, Sabanas de Murur Bisuk, estribaciones de Cerro Amú, G. Herrera & W. Gamboa 3593 (MO); Buenos Aires, Violey, Sabanas Esperanzas, L. González 1196 (INB); Buenos Aires, Salitre, Cerro Sipar, L. González 1215 (INB); Parrita, Cuenca del Naranjo y Paquita, Fila Chonta, La Virgen, sector SE, Fila entre la vuelta del Pallo, cabeceras Río Palo Seco y Fila Chonta, J. F. Morales & R.J. Abarca 6294 (MO); Buenos Aires, Potrero Grande, A. Rodríguez 9744 (INB); Buenos Aires, Potrero Grande, A. Rodríguez 9835 (INB); Boruca, Savanes de Boruca, Soc. ex. San José 449 (CR); Buenos Aires, Potrero Grande, D. Solano 2871 (INB); Buenos Aires, M. Valerio 873 (CR); Monteverde, 10 km S Monteverde on road to Inter American Highway, area of spring, W. Haber 9960 (INB); Coto Brus, Savanas de Cañas Gordas, H. Pittier 7355 (US); Coto Brus, Savanes de Cañas Gordas, H. Pittier 11019 (MO); Coto Brus, Savanas de Cañas Gordas, H. Pittier 7358 (US); Borde de chemin de Mano de Tigre, H. Pittier 4630 (US); San José: Perez Zeledón, along Carretera Interamericana, S slope Cerro de la Muerte, between km 125 and km 117, M. Grayum & B. Hammel 9580 (MO, INB); Aserri, bosque primario y tacotales en la Fila El Alto, J.F. Morales 3390 (INB); Aserri, Faldas SE Fila Aguabuena, entre Quebrada Ceniza y Quebrada Sopapo, camino a Bijagual, J.F. Morales 6863 (INB, CR); Acosta, Alto Reflis, Falda NE, Fila de Cal, J.F. Morales 8764 (INB); Escazú, San Antonio, J. González 2886 (INB); Aserri, Cuenca del Pirris-Damas, Cerros Caraigres, Falda S, Quebrada Concha, en el camino viejo a Bijagual, J.F. Morales 5915 (MO); Aserri, Cuenca del Pirris-Damas. Ceiba Alta, Cuest Pacayas, Quebrada Pacayas, charrales residuales, J.F. Morales 6759 (MO, INB); 6 km by road N of San Pablo, N of San Marcos, open dry pasture on a hilltop, R.W. Pohl & M. Lucas 13142 (MO); Acosta, Cerro León, camino hacia Fila Aguabuena, R. Chacón et al. 190 (CR); Santa Ana, Z.P. Cerros de Escazú, Alto Caña Quemada, A. Estrada et al. 3241 (CR); Cercanías de División, Carretera Interamericana Sur, J. Gómez-L. 3460 (USJ); Acosta, Cuenca del Río Pírris-Damas, Fila del Naranjal, sendero a la Escuadra, J.F. Morales 7459 (CR, INB, MO); Acosta, Cerro León. Camino hacia Fila Aguabuena, A. Quesada et al. 741 (CR); Acosta, Cerro León. Camino hacia Fila Aguabuena, J. Sánchez et al. 1170 (CR); 3 km SSE of Villa Colon, R.W. Pohl & G. Davidse 11399 (US); 13 km N of San Isidro de El General along the Carretera Interamericana, R.W. Pohl & G. Davidse 11631 (US). Honduras. Comayagua: Ojo de Agua, orilla Río Humuya, 30 km N de ciudad Comayagua, bosque de vega tropical rodeado de pinares, C. Nelson et al. 6818 (MO). Panama. Chiriquí: In bare clay of steep artificial roadside bank below coffee finca. Western slope of first ridge east of Quebrada Zumbona, opposite east side of Cerro Pando, 7 km (by air) northwest of El Hato Del Volcán, T.S. Cochrane et al. 6327 (MO); Boquete, ca. 26 km N of David along the road to Boquete, Curatella-Byrsonima-Trachypogon savanna on old lava flow, G. Davidse & W.G. D’Arcy 10138 (MO); Boquete, eastern slope of Volcán de Chiriquí (Barú), WNW of Boquete. Partially cleared slopes with patches of original oak forest and mostly secondary growth, G. Davidse & W.G. D’Arcy 10170 (MO); Large old lava flow ca. 3 km NE of El Hato del Volcán at base of Volcán de Chiriquí (Barú), 1–3 km E of highway, G. Davidse & W.G. D’Arcy 10332 (MO); Llanos E of El Hato de Volcán, savannah and woods on lava flow, B. Hammel et al. 6811 (MO); Grassy slopes on lava flow about 16 km above town at Volcan, B. Hammel 1585 (MO); Volcán Barú, summit to llanos at base of W slope, along trail, B. Hammel et al. 6576 (MO); Lava fields near the town of Volcan, J.A. Duke 9143 (MO); Western slopes of Volcan de Chiriqui (Baru), on lava flow, S. Mori & J. Kallunki 5714 (MO); Bambito, in savanna 1 mile south, M. Partch 69-31 (MO); Alto Boquete, savanna, M. Partch 69-62 (MO); 2 km S of Boquete above the Río Caldera near a small flood control dam. Disturbed roadside, P.M. Peterson & C.R. Annable 7349 (MO, US); Between Río Quebrado El Velo and Río Caldera, W of San Ramon and NW of Boquete, gravel pit with very steep sandy slopes, P.M. Peterson & C.R. Annable 7372 (MO, US); 1 km NW of Boquete on road towards Volcan Baru, dry roadcut in bare soil, P.M. Peterson & C.R. Annable 7376 (MO, US); S end of Boquete, dry open slopes, P.M. Peterson & C.R. Annable 7385 (MO, US); NW of Boquete, between Finca Lerida and San Ramon, P.M. Peterson & C.R. Annable 7371 (MO, US); S end of Boquete, P.M. Peterson & C.R. Annable 7386 (MO, US); Ca 1.5 mi. northeast of El Hato del Volcan, grassy plain with occasional patches of forest, S. McDaniel 10199 (MO); Foothills, vicinity of El Boquete, A.S. Hitchcock 8241 (US); foothills, vicinity of El Boquete, A.S. Hitchcock, 8242 (US); Cerro Vaca, eastern Chiriqui, in savannas, H. Pittier 5360 (US); Cerro Vaca, eastern Chiriqui, in savannas, H. Pittier 5362 (US). Cocle: hills S of El Valle de Antón, P.H. Allen 2812 (MO);vicinity of Ola, H. Pittier 5062 (US), H. Pittier 5042 (US). Veraguas: Cerro Campana, savannas S of radio tower, B. Hammel 5528 (MO).

Loosely tufted annuals to short-lived perennials. Culms 2–12 cm tall, 0.2–0.4 mm diameter just below the panicle, erect or decumbent, slender, glabrous, sometimes flowering the first year, up to 15 cm broad, dying in the center, profusely branched below, a short branchlet with fascicled leaves borne at each node, with 4–6 nodes; internodes 2–20 mm long. Leaf sheaths 2–20 mm long, generally shorter than the internodes, glabrous, ridged, flattened by the densely fascicled branches; ligules 0.6–2.5 mm long, membranous to hyaline, apex truncate to rounded; blades 0.3–2.2 cm long, 0.8–1.5 mm wide, flat or folded, prominently veined, thick, firm, usually with whitish-thickened midvein and margins, conspicuously crystalline or spiculate on both surfaces, otherwise glabrous below, sparsely scaberulous above and along margins, tapering to a boat shaped tip. Panicles 1.0–3.0 cm long, 0.3–1.4 cm wide, long exerted or included in the uppermost sheath, loosely contracted; primary branches 5–9 mm long, one per node, appressed or reflexed at maturity up to 70° from the culm axis; pedicels 1–3 mm long, stiff, densely scabrous, spiculate, erect. Spikelets 1.5–3.0 mm long, often plumbeous to reddish-purple; glumes 1.0–1.9 mm long, subequal, glabrous, apex acute to obtuse, often minutely erose, greenish-gray; lower glumes 1.0–1.7 mm long, 1-veined; upper glumes 1.1–1.9 mm long, 1-veined or occasionally 3-veined; lemmas 1.5–3.0 mm long, lanceolate, 3-veined, keeled, glabrous, mottled with greenish-black areas or dark greenish mottles on a pale background, apex minutely scaberulous, acuminate, entire or mucronate; mucro rarely more than 1(–1.2) mm long; paleas 1.4–2.9 mm long, lanceolate, glabrous; anthers 0.8–1.1 mm long, purplish becoming pale. Caryopses 0.8–1.2 mm long, elliptic to fusiform, brownish.

Figure 11. 

A–E Muhlenbergia microsperma (DC.) Kunth A habit B inflorescence C ligule D glumes E floret F–J Muhlenbergia ligularis (Hack.) Hitchc. F habit G ligule H glumes I floret J stamens and pistil. A–E drawn from P.M. Peterson 4185 (US, WS) F–J drawn from P.M. Peterson, C.R. Annable, S. Lægaard & R.J. Soreng 12684 (US-3275569).

This species ranges from Guatemala and Costa Rica to Colombia, Venezuela, Ecuador, Bolivia, Peru, and Argentina (Pohl 1980; Peterson and Annable 1991; Peterson et al. 2001; Giraldo-Cañas and Peterson 2009).

Muhlenbergia ligularis occurs in grassy flats, moist depressions, wet meadows, gravelly banks, ridgetops, and gravelly roadsides often derived from calcareous substrates, associated with Achnatherum, Aciachne, Agrostis, Alnus, Anatherostipa, Baccharis, Berberis, Bidens, Buddleja, Caiophora, Carex, Cenchrus clandestinus (Hochst. ex Chiov.) Morrone, Colletia spinosissima J.F. Gmel., Eleocharis, Festuca, Gaultheria, Hypericum, Jarava, Juncus, Lepidophyllum, Lupinus, Margyricarpus, Muhlenbergia, Nassella, Plantago, Poa, Puya, Rumex, Salvia, and Senecio; 2320–4650 m.

Muhlenbergia ligularis is morphologically similar to the widespread South American, M. fastigiata (J. Presl) Henrard. It can be separated from the latter by possessing flat leaf blades, 0.8–1.5 mm wide, and a rather loosely tufted habit without wiry creeping rootstocks and scaly rhizomes. Morphologically, M. ligularis differs from the Peruvian endemic M. caxamarcensis Lægaard & Sánchez Vega in having glabrous lemmas (sericeous hairs on lower 1/2–3/4 of the lemma in the latter) [Peterson et al. 2018].

Molecular DNA sequence analysis indicates M. ligularis falls within the M. subg. Bealia clade in a subclade with M. filiformis (Thurb. ex S. Wats.) Rydb. and M. vaginata (Fig. 1; Peterson et al. 2021).

Costa Rica. San José: Valle de los Conejos (upper Río Talari) and trails to Cerro Chirripó and the Valle de los Lagos, open paramo formation with stands of Chusquea bamboo 1–2.5 m tall on slopes and in the valley, short grasses and very short (30 cm), shrubs on the exposed ridges, W.C. Burger & R.L. Liesner 7470 (CR); Perez Zeledón, Paramo en el Sendero al Valle de los Conejos, E. Alfaro 415 (INB, MO); Perez Zeledon, Rivas, sendero Valle Los Conejos y Cerro Chirripo en Paramo, E. Alfaro 572 (INB); Perez Zeledón, Valle de los Conejos, E. Alfaro 3873 (INB); P. N. Chirripó Alrededores del refugio, parte inferior (sur) del Valle de los Conejos, J. Gómez 5344 (CR); P.N. Chirripó A la vera del Río Talari, parte inferior (Sur) del Valle de los Conejos, J. Gómez 5382 (CR); P.N. Chirripó Valle de los Conejos, R. Ocampo 1500 (CR); Pérez Zeledón, Rivas, A. Rodríguez 6414 (INB); P.N. Chirripó Valle de los Conejos, R. Soto s.n. (CR). Guatemala. Huehuetenango: along road in region of Chémal, Sierra de los Cuchumatanes, at km 36, P.C. Standley 81703 (MO); Sierra de los Cuchumatanes, 6.6 mi NW of Santa Eulalia on road to San Mateo Ixtatán, P.M. Peterson & C.R. Annable 4691 (ARIZ, ENCB, GH. MEXU, MICH, MO, NMC, NY, RSA, TAES, UC, UNLV, US, UTC, WIS, WS); 3.6 mi NW of Paguix on hwy 9N and 16.2 mi S of San Juan Ixcoy, P.M. Peterson & C.R. Annable 4686 (GH, MO, NY, US, WS); 15.1 mi S of San Juan Ixcoy on hwy. 9N, Peterson & Annable 4688 (GH, MO, NY, RSA, US, WS); Meadow at Tojiah on hwy. 9N, P.M. Peterson & C.R. Annable 4695 (GH, MO, NY, RSA, UC, US, WS); 13 mi NW of Santa Eulalia on road to San Mateo Ixtatán, P.M. Peterson & C.R. Annable 4692 (ARIZ, ENCB, GH, MEXU, MICH, MO, NMC, NY, RSA, TAES, UC, UNLV, US, UTC, WIS, WS); Meseta alta Sierra de los Cuchumatanes, R. López s.n., (MO); Cerro Chemalito, Sierra de Cuchumatanes, 3.5 miles W of Santa Eulalia, J.A. Steyermark 49905 (MO); Sierra de los Cuchumatanes, at Chemal at km 318 on Ruta Nacional 9N, J.H. Beaman 3068 (US); Sierra de los Cuchumatanes, immediately north of Tojiah at km 322 on Ruta Nacional 9N, J.H. Beaman 3920 (US); Region of Chemal, Sierra de los Cuchumatanes, P.C. Standley 81115 (US); Sierra de los Cuchumatanes, 3.6 mi NW of Paguix on hwy 9N and 16.2 mi S of San Juán Ixcoy, P.M. Peterson & C.R. Annable 4686 (GH, MO, NY, RSA, US, WS); 15.1 mi S of San Juan Ixcoy on hwy 9N, P.M. Peterson & C.R. Annable 4688 (GH, MO, NY, RSA, US, WS); 6.6 mi NW of Santa Eulalia on road to San Mateo Ixtatán, P.M. Peterson & C.R. Annable 4691 (ARIZ, ENCB, GH, MEXU, MICH, MO, NMC, NY, RSA, TAES, UC, UNLV, US, UTC, WIS, WS); 13 mi NW of Santa Eulalia on road to San Mateo Ixtatán, P.M. Peterson & C.R. Annable 4692 (ARIZ, ENCB, GH, MEXU, MICH, MO, NMC, NY, RSA, TAES, UC, UNLV, US, UTC, WIS, WS); Meadow at Tojiah on hwy 9N, P.M. Peterson & C.R. Annable 4695 (GH, MO, NY, RSA, UC, US, WS); SW of Tojiah on Hwy 9N, P.M. Peterson & C.R. Annable 4700 (NY, US, WS). Chimaltenango: Cerro Chichoy near Chichoy, L.O. Williams & A. Molina R.15317 (US). Totonicapan: On the Tecum Uman Ridge at km 154 on Ruta Nacional N1, ca 20 km east of Totonicapan, J.H. Beaman 4156 (UC, US); Desconsuelo, potrero natural, Flora alpine, M. de Koninck 116 (US); Region of Desconsuelo, P.C. Standley 62736 (US); Region of Chiu Jolom, mountains above Totonicapan, on road to Desconsuelo, P.C. Standley 84418 (US); Totonicapan, En pastizal dominado por Agrostis exserta y Geranium alpicola, muy sobrepastoreado; plano; plena sol, Smith & Nelson 768 (MO).

Caespitose perennials. Culms 75–200 cm tall, erect, terete near base, forming dense clumps of 100 culms or more and up to 1 m in diameter, pubescent below the nodes, usually 1 or 2 nodes per culm; internodes mostly glabrous. Leaf sheaths 15–40 cm long, shorter than the internodes, glabrous to scaberulous, the basal persistent and keeled with age; ligules (5–)8–40(–50) mm long, strongly decurrent, splitting into broad auricles 10–35(–50) mm long, membranous to chartaceous above, brownish, firm, the veins evident below and near margins, apex truncate to obtuse; blades 20–60 cm long, 2–5 mm wide, mostly flat and apically involute, scabrous above and below. Panicles (15–)20–40 cm long, 5–12 mm wide, dense, spikelike, erect, exserted and surpassing the blades in height, greenish to greenish-gray; primary branches 0.1–1.2 cm long, ascending and tightly appressed, unexposed, imbricate; pedicels 0.1–1.7 mm long, shorter than the spikelets, scaberulous to hispidulous. Spikelets 3.4–5.6(–6) mm long, erect, strongly laterally compressed, greenish-gray; glumes 3.4–5.6 mm long, linear-elliptic to linear-ovate, usually longer than the lemma, 1-veined, scabrous along the keel, subequal, awnless, the upper slightly longer, apex acute to acuminate, scabrous; lemmas 3.4–5 mm long, elliptic to linear-elliptic, scabrous, greenish-gray; callus pilose, the hairs 0.1–0.3 mm long, apex acute, rarely mucronate, the mucro less than 0.4 mm long; paleas 3.4–5 mm long, about as long as the lemma, scabrous, apex acute; anthers 1.5–2.2 mm long, pale greenish. Caryopses 2–3 mm long, fusiform, brownish. 2n = 20, 24, 28.

Muhlenbergia macroura occurs in the Sierra Madre Occidental in northern México from Chihuahua to Chiapas and Guatemala (Herrera Arrieta and Peterson 2018).

This species can be found growing on upland slopes, mountain meadows, in pine or pine-oak forests often in deep humid soils; 1500–3400 m.

Muhlenbergia macroura is morphologically similar to M. nigra but differs in having spikelets 3.4–5.6(–6) mm long [(5.5–)6–8 mm long in M. nigra] and greenish to greenish-gray panicles (15–)20–40 cm long [dark green to blackish panicles 6–15(–17) cm long in M. nigra]. Muhlenbergia macroura is a member of M. subg. Trichochloa, and in a recent study was found to be sister to M. rigida (Peterson et al. 2021).

Guatemala. Chimaltenango: Plains near Tecpam, A.F. Skutch 610 (US). Guatemala: Guatemala City, A.S. Hitchcock 9140 (US). Huehuetenango: La Sierra (Tujimach), across river from San Juan Atitlan, Sierra de los Cuchumatanes, J.A. Steyermark 51968 (US); Paquix, San Juan Ixcoy, Sierra de los Cuchumatanes between Paquix and San Juan Ixcoy, A.A. Molina et al. 30017 (MO); San Juan Ixcoy, Sierra de los Cuchumatanes, along road to Huehuetenango, 5 miles S of San Juan Ixcoy, D.E. Breedlove 8569 (MO, DS); San Juan Ixcoy, Jolomhuitz, Aldea Jolomhuitz, M. Véliz 95.4470 (MO). Quetzaltenango: Mountains near Santa Maria, near Quetzaltenango, Weatherwax 177 (US); La Esperanza, M. de Koninck 18 (US); Cuesta El Caracol, Sierra Madre Mountains, about 5–8 km N of San Juan Ostuncalco, L.O. Williams et al. 22770 (US); Oak pine forest, above Los Vahos, Cerro Quemado, P.C. Standley 86171 (US). Quiche: Chichicastenango, 1 km N of Chichicastenango, W.E. Harmon 4369 (MO). Sacatepequez: Santa Maria de Jesús, Mal Paso, Volcán de Agua, Mal Paso, M. Véliz et al. 8529 (MO); Volcan Agua, W.A. Kellerman 4764 (US). San Marcos: Tajumulco, Volcan Tajumulco, M. Véliz et al. 10622 (MO), M. Véliz et al. 10638 (MO); El Boqueron, in the mountains at the summit of the road between San Antonio Sacatepequez and Palestina, P.C. Standley 85307 (US). Solola: Volcan Atitlan, near summit of mountain, J. H. Beaman 4053 (US); NW of Los Encuentros, L.O. Williams, A. Molina R. & T.P. Williams 25404 (F, US). Totonicapán: near San Francisco El Alto, P.C. Standley 83123 (US); along road between San Francisco El Alto and Momostenango, P.C. Standley 84011 (US); O. F. Cook 35 (US); Hochland von Calel, s.n. 2703 (US). Mexico. Chiapas: Vol. Tacana, Chiquihuite, E. Matuda 2829 (ARIZ, MO); Mt. Tacana, E. Matuda 2420 (DS). Amecatlán, Paraje Navenchauk, along mexican Hwy 190, R. M. Laughin 1506 (ENCB). La Grandeza: La Grandeza to Ojo de Agua, E. Hernandez X-1445 (US). Larráinzar: Muctahuitz. Región Los Altos, L. Soto s/n (MEXU). Motozintla: On the N and W slope of Cerro Mozotal below the microwave tower along the road from Huixtla to El Porvenir and Siltepec, D.E. Breedlove & R.F. Thorne 31173 (MO). San Juan Chamula: near school house of yal Ichin, D.E. Breedlove 7147 (ENCB, DS); Yut Bax, C. Santoz Ruíz 179 (ENCB). Motozintla, NW slope of cerro Mozotal, along the road from Huixtla to El Porvenir and Siltepec, D.E. Breedlove 31175 (NY); Slope near the school house of Yal Ichin, D.E. Breedlove 10471 (DS). Tenajapa: Paraje Matsbad, Alush Shilon Ton 999, (ENCB, DS); Paraje Shohieh, Alush Shilon Ton 548 (ENCB, DS); near Tenejapa Center, Alush Shilon Ton 63 (DS). Venustiano Carranza: Ejido “Laja Tendida” km 17 carr. Venustiano Carranza-Tuxtla Gutiérrez, aprox. 2 km a Flores Magón, A. Miranda S. s/n (MEXU). Zinacantán: near Paraje Nachij [Nachig], D.E. Breedlove & G. Davidse 53871 (CAS, MO); Steep NE slope of Zontehuitz near Summit, D.E. Breedlove 12348 (DS); near Zinacantán Center, R.M. Laughlin 2241 (DS); at paraje Navenchauk along Mexican Highway 190, R.M. Laughlin 1506 (DS); alley floor in Zinacantán Center, R.M. Laughlin 630 (DS).

Caespitose annuals, sometimes appearing as short-lived perennials. Culms 10–80 cm tall, often geniculate at the base, slender, often striate, much branched near the base, scaberulous below the nodes; internodes 1.8–8.6 mm long, mostly scaberulous or smooth. Leaf sheaths 2.2–6.6 mm long, commonly shorter than the internodes, glabrous, smooth or scaberulous; ligules 1–2 mm long, membranous to hyaline, decurrent, margins often extended, apex truncate to obtuse; blades 3–8.5(–10) cm long, 1–2.5 mm wide, flat or loosely involute, scabrous below, strigulose above, often deciduous with age. Panicles 6.5–13.5 cm long, 1–6.5 cm wide, open and not densely flowered, often purplish; primary branches 1.6–4 cm long, ascending or diverging up to 80° from the rachises, spikelet-bearing to the base; pedicels 2–6 mm long, appressed to divaricate, antrorsely scabrous. Cleistogamous panicles with 1–3 spikelets present in the axils of the lower sheaths. Spikelets 2.5–5.3 mm long; glumes 0.4–1.3 mm long, exceeded by the florets, 1-veined, obtuse, often minutely erose; lower glumes 0.4–1 mm long; upper glumes 0.6–1.3 mm long; lemmas 2.5–3.8(–5.3) mm long, narrowly lanceolate, mostly smooth, scaberulous distally, hairy on the lower 1/2 of the margins and midveins, the hairs 0.2–0.5 mm long, the callus hairy, apices acuminate, often bidentate, awned, awns 10–30 mm long, straight to flexuous; paleas 2.2–4.8 mm long, narrowly lanceolate, acuminate; anthers 0.3–1.2 mm long, purplish. Caryopses 1.7–2.5 mm long, fusiform, reddish-brown. 2n = 20, 40, 60.

Muhlenbergia microsperma occurs in Hawaii, southwestern USA, México, Guatemala, Colombia, Venezuela, Ecuador (including the Galapagos Islands), Peru, and Bolivia (Peterson and Annable 1991).

Rocky slopes, rock outcrops, sandy drainages, cliffs, and disturbed roadsides usually in desert scrub vegetation with Acacia, Aristida adscensionis L., Baccharis, Bombacaceae, Cactaceae, Dodonaea viscosa (L.) Jacq., Fucraea, Heliotropium, Heteropogon contortus (L.) P. Beauv. ex Roem. & Schult., Lantana, Pitcairnia, Prosopis, Puya, Salvia, Schinus molle L., and Schizachyrium; 1150–3500 m.

Muhlenbergia microsperma can sometimes be confused with M. romaschenkoi known only from Peru and differs from it by having cleistogamous panicles in the axils of the lower sheaths and shorter, obtuse glumes, 0.4–1.3 mm long (glumes acute to acuminate, 2–2.8 mm long in M. romaschenkoi) [Peterson et al. 2018].

In a molecular DNA sequence study, M. microsperma forms a strongly supported clade with two other annuals, M. appressa C.O. Goodd. and M. brandegei C.G. Reeder, all members of M. subg. Muhlenbergia (Fig. 1; Peterson et al. 2010b). In addition, these three species produce cleistogamous spikelets in the axils of the lower culm branches, enclosed by a sheath (Peterson and Annable 1991). Cleistogamous spikelets appear to have evolved twice within Muhlenbergia, once in M. subg. Muhlenbergia within the M. appressa–M. brandegei–M. microsperma clade and once in M. sect. Pseudosporobolus in M. cuspidata (Torr. ex Hook.) Rydb. (Morden and Hatch 1984; Peterson et al. 2010b).

Guatemala. Sacatepequez: Above Pastores, wet thicket, P.C. Standley 60819 (US); Volcano Agua, near Antigua, shady bank, A.S. Hitchcock 9130 (US); Antigua, W.A. Kellerman 7301 (US).

Delicate annuals. Culms 5–40 cm tall, erect or spreading, slender, scaberulous to strigulose below the nodes, 0.3–0.7 mm diameter just below the inflorescence; internodes 8–25 mm long. Leaf sheaths 4–52 mm long, shorter to longer than the internodes, glabrous or scaberulous, margins hyaline; ligules 1–2.6 mm long, hyaline, apex irregularly toothed to lacerate, truncate to obtuse, margins entire, sometimes splitting off to form auricles which are not longer than the body of the ligule; blades 0.5–4.0(–10) cm long, 0.8–2.0 mm wide, flat or involute, short pubescent above and scabrous below. Panicles 5.0–16.2(–21) cm long, 1.5–6.5 cm wide, open, ovate, nodes 12–35 per inflorescence; primary branches 8–42 mm long, one or two per node, spreading 25–80° from the rachis; pedicels 2–7 mm long, slender often capillary, erect. Spikelets 0.8–1.5 mm long, erect; glumes 0.5–0.9 mm long, subequal, 1-veined, sparsely short-pilose at least near apex; lower glumes 0.5–0.8 mm long, obtuse to acute; upper glumes 0.6–0.9 mm long, obtuse, usually broader than the first glume; lemmas 0.8–1.5 mm long, lanceolate, with short appressed silky pubescence located along the midvein and margins to glabrous, unawned, apex obtuse to subacute; paleas 0.8–1.4 mm long, about as long as lemma, with short appressed silky pubescence between the veins or glabrous; anthers 0.2–0.7 mm long, purplish. Caryopses 0.6–0.9 mm long, fusiform to elliptic, brownish. 2n = 60, 80.

Figure 12. 

A–D Muhlenbergia peruviana (P. Beauv.) Steud. A habit B floret C glumes D ligule E–H Muhlenbergia minutissima (Steud.) Swallen E habit F ligule G spikelet H floret. A–D drawn from P.M. Peterson & C.R. Annable 4067 (US, WS) E, G, H drawn from P.M. Peterson & C.R. Annable 5601 (US-3182908) F drawn from P.M. Peterson & C.R. Annable 4675 (US, WS).

Western North America from central Washington to Montana south to Texas, U.S.A. and throughout México to Guatemala (Peterson and Annable 1991).

Sandy and gravelly drainages, rocky slopes, flats, road cuts, and open sites most commonly in yellow pine forests, oak-pine forests with Arctostaphylos, thorn scrub forests with Acacia, pinyon-juniper woodlands, and oak-gramma grass (Bouteloua) savannahs; 1200–3000 m.

Morphologically, Muhlenbergia minutissima can be separated from other annual species of Muhlenbergia in Central America in having sparsely short-pilose glumes near the apex and open, ovate, panicles with pedicels that are longer than the spikelets (2–7 mm long [Peterson and Annable 1991].

Based on DNA sequence analysis, Muhlenbergia minutissima is a member of M. subg. Bealia and shares a most recent common ancestor with M. sinuosa Swallen, a species known to occur in Arizona and New Mexico, USA and Chihuahua and Sonora, México (Peterson and Annable 1991; Peterson et al. 2021).

Guatemala. Quetzaltenango: Santa Maria, Volcano Agua, A.S. Hitchcock 9130 (MICH, US-998503). Quiché: W.A. Archer 3858 (US-1646054). Totonicapán: E of San Cristóbal Totonicapán, Harmon 4570 (ENCB, NY).

Densely caespitose perennial. Culms 10–80(–90) cm tall, erect, terete near base, glabrous below the strictly basal nodes; internodes mostly glabrous, occasionally glaucous. Leaf sheaths 2–35 cm long, longer than the lower internode, glabrous to scaberulous, often glaucous, becoming flat, loose and papery, and occasionally spirally twisted near the base; ligules 4–14(–20) mm long, membranous, decurrent, apex acute to acuminate, often lacerate; blades 6–30 cm long, 1–2.5(–3) mm wide, flat becoming loosely involute to subfiliform, somewhat stiff, scabrous below and hirsute above. Panicles 5–25 cm long, (1–)2–6 cm wide, narrow to somewhat open, loosely flowered, not dense; primary branches 0.5–10 cm long, ascending, appressed or spreading to 40° from the rachises; pedicels 2–7 mm long, longer than the spikelets, flattened, scabrous, occasionally stiffly reflexed. Spikelets 3–4.5(–7) mm long, erect, occasionally reflexed; glumes (1–)1.5–3.2(–4) mm long, ⅓ to ⅔ as long as the lemma, subequal, glabrous to scaberulous above; lower glumes 1-veined, sometimes mucronate, the mucro less tan 1 mm long; upper glumes 3-veined, 3-toothed and 3-awned, the teeth (including the awns) ⅓ to the length of the glume, and the awns up to 1.7 mm long, apex truncate to acute; lemmas 3–4.5 mm long, lanceolate, awned, often greenish or yellowish with dark green or purple mottles, scaberulous above, loosely to densely appressed-pubescent to pilose along the midvein, margins, and proximal. to ⅘, the hairs up to 0.8 mm long, occasionally glabrous, apex acute to acuminate, the awn (2–)6–25 mm long, flexuous; paleas 3–4.5 mm long, lanceolate, loosely to densely appressed-pubescent to pilose between the veins on the proximal ⅓ to ⅘, apex acute to acuminate, scaberulous; anthers 1.5–2.3 mm long, purplish. Caryopses 1.8–2 mm long, fusiform, light brown. 2n = 20, 40 (Herrera Arrieta 1998).

This species ranges from southwestern USA throughout western México to Guatemala (Peterson et al. 2001).

Muhlenbergia montana grows on rocky slopes, dry meadows, ridgetops, and open grasslands, primarily in upland and mountain habitats in pine and oak forests, at elevations of 1400–3000 m.

Muhlenbergia montana is morphologically similar to M. quadridentata but can be separated from the latter in having 3-toothed and 3-awned upper glumes with teeth 1/3 to ½ the length of the glume (the teeth are small <1/6 the length of the glumes in M. quadridentata), lemmas that are greenish or yellowish with green mottles or purple mottles (the lemmas are greenish-plumbeous to mottled plumbeous in M. quadridentata), and the anthers are usually 1.5–2 mm long (2–2.5 mm long in M. quadridentata) [Herrera Arrieta and Peterson 2007, 2018].

Muhlenbergia montana is a member of Muhlenbergia subg. Clomena, a lineage hypothesized to have originated in the Sierra Madre of México about 5.4 mya (Peterson et al. 2021).

Guatemala. Huehuetenango: La Sierra (Tujimach), across river from San Juan Atitlan, Sierra de los Cuchumatanes. Open upper slopes, J.A. Steyermark 51989 (US); About Laguna de Ocubila, east of Huehuetenango, dry open oak woods, P.C. Standley 82722 (US); Chiantla, cerca del cementerio, Llano de San Nicolás, D.N. Smith 442 (MO)¸ Aldea San Nicolás, Chiantla, D.N. Smith 491 (MO). Quetzaltenango: La Esperanza, lugares secos, esteriles, M. de Koninck 132 (US). Quiche: Between Quiche and San Pedro Jocopilas, on dry rolling hills with pine and oak forest, P.C. Standley 62453 (US). Mexico. Chiapas: Amatenango del Valle: S of the center of Amatenango del Valle, Alush Shilom Ton 1531, (ENCB). San Cristóbalde las Casas: “El Banco” sobre el libramiento E a San Cristobal, km 4 carr. San Cristobal de Las Casas-Tenejapa, A. Miranda S. s/n (MEXU); D.E. Breedlove & G. Davidse 55174 (CAS) cited in Reeder (1994).

Densely caespitose perennials. Culms 75–100(–120) cm tall, erect, scabrous or strigulous below the nodes, rounded near base. Leaf sheaths shorter than internodes, glabrous or scaberulous, purplish in part, rounded below; ligules (2–)5–8 mm long; blades 20–40 cm long, 2–3 mm wide, flat or loosely involute, scabrous abaxially, scabrous on ribs adaxially, attenuate into a long apex. Panicles (5–)10–15(–20) cm long, 1–3(–6) cm wide, oblong-cylindrical, spreading, purple, rarely purplish-green; primary branches 4–8(–10) cm long, ascending or appressed; pedicels 1–3 mm long, usually shorter than the spikelets, slender, scabrous below spikelets. Spikelets (4–)4.5–5 mm long; glumes 1.5–2 mm long, acute, subequal, scabrous near the apex; lemmas (4–)4.5–5 mm long, scaberulous between veins, mucronate or shortly awned from 2 minute teeth, the mucro or awn 0.5–1(–2) mm long; callus hairy, the hairs 0.5–0.7 mm long; paleas about as long as the lemma, scabrous between the veins, apex acute or acuminate; anthers 2–2.2 mm long, purplish. Caryopses 2–2.5 mm long, about 0.5 mm wide, ellipsoid, reddish-brown.

Figure 13. 

A–G Muhlenbergia rigida (Kunth) Kunth A habit B inflorescence (narrow) C inflorescence (open) D ligule E glumes F floret G stamens and pistil H Muhlenbergia mucronata (Kunth) Trin. H floret. A, B drawn from P.M. Peterson 9659 (US) C–I drawn from P.M. Peterson, C.R. Annable & J. Valdés-Reyna 10876 (ANSM, US) H drawn from P.M. Peterson & C.R. Annable 10778 (US).

This Mexican endemic is known from: Baja California and Chihuahua in the north throughout central México to Oaxaca, Veracruz, and Chiapas in the south (Herrera Arrieta and Peterson 2018).

Muhlenbergia mucronata grows in oak–pine forests at elevations of 1350–2650 m.

Muhlenbergia mucronata is morphologically similar to M. rigida, differing from the latter in having mucronate to short-awned lemmas, narrower panicles, and usually shorter pedicels.

Muhlenbergia mucronata is a member of M. subg. Trichochloa and pairs with M. subaristata Swallen in a recent biogeographical analysis based on plastid and nuclear DNA sequences (Fig. 1; Peterson et al. 2021).

Mexico. Chiapas: San Cristóbal de las Casas: 7 km E of San Cristobal las Casas in road to Zontehuitz, D.E. Breedlove 11153 (US-3113121, US-3113122). Tenejapa: along river Chik Ha, barrio of Yashanal, D.E. Breedlove 11125 (US-3113120). Zinacantán: along hwy 190 at Granadilla, D.E. Breedlove 10607 (US-3113119), D.E. Breedlove 52324 (CAS) citado en Flora Mesoamercana.

Strongly caespitose perennials. Culms 120–300 cm tall, erect, compressed-keeled near the base, glabrous below the nodes to sometimes scaberulous. Leaf sheaths 12–32 cm long, shorter than internodes, sometimes purplish near base, often changing to brown with age, keels prominent and glabrous, lacking auricles; ligules (5–)8–15 mm long, membranous, apex lacerate; blades 35–110 cm long, 5–10 mm wide, flattened, scaberulous adaxially and glabrous abaxially, margins and keels serrate. Panicles 35–100 long, (8–)15–30 cm wide, purple or brown-purplish, branches ascending or pendulous spreading up to 60° from culm axis; primary branches 6–25 cm long, usually 15–20 cm long below, naked near the base, pendulous to flexuous; pedicels 0.2– 2.5 mm long, generally shorter than spikelets, scaberulous. Spikelets 1.3–2.6(–3) mm long, erect, purple to brownish-purple; glumes 1.3–2.6(–3) mm long, ovate, generally longer than florets, subequal, 1-veined, often translucent, usually glabrous to scaberulous, apex acute to obtuse; lemmas 1.3–2.3 mm long, oblong, awnless, rarely mucronate, glabrous; paleas 1.3–2.3 mm long, glabrous, apex acute to obtuse; anthers 0.9–1.3 mm long, yellow to purplish. Caryopses 1–1.3 mm long, fusiform, reddish-brown. 2n = 20, 24.

Figure 14. 

A–I Muhlenbergia mutica (Rupr. ex E. Fourn.) Hitchc. A habit B ligule C glumes D. lemma E stamens, pistil, and lodicules F inflorescence branch G glumes H lemma I stamens and lodicules. A–E drawn from P.M. Peterson & C.R. Annable 6051 (US) F–I drawn from Carl Mez Herbarium 3370 [Botteri & Sumichrast 104] (US-1720166).

Muhlenbergia mutica ranges from Chihuahua, Sinaloa, and Durango, México south to Oaxaca, Veracruz, and Chiapas (Herrera Arrieta and Peterson 2007, 2018).

The species grows among pines or pine–oak forests and tropical forests with Liquidambar, Nyssa, and Sabal; 600–2300 m.

Muhlenbergia mutica can be separated morphologically from M. robusta in having wider panicles (8–)15–30 cm wide (2–8 cm wide in M. robusta) and non-auriculate leaf sheaths [auricles 2–4(–10) mm long in M. robusta] (Herrera Arrieta and Peterson 2018). Muhlenbergia mutica is a member of M. subg. Trichochloa, and in a recent study was found sister to M. virletii (E. Fourn.) Soderstr., another Mexican endemic (Peterson et al. 2021).

Soderstrom (1967) chose to recognize M. mutica and M. gigantea, stating, “The only character to separate the two is the length of the glumes in relation to the floret. It (M. mutica) is most closely related to and doubtfully distinct from M. gigantea.” After careful study of the isolectotypes attributed to M. mutica and M. gigantea (both housed at US), we find no differences in glume length, and they appear to represent specimens of a single species. Therefore, we place M. gigantea (younger name) as a synonym of M. mutica in our treatment.

Mexico. Chiapas. Cintalapa: 12 km S of’ Mexican hwy 190 near Rizo de Oro, Crest of the Sierra near the microwave station of La mina, D.E. Breedlove 20641 (ENCB); 23 km W of Las Cruces along road to La Mina Microwave Station, D.E. Breedlove & G. Davidse 54111 (CAS, MO); Slope, near La Cienega de Leon 30 km N of Las Cruces, D.E. Breedlove & F. Almeda 48041 (CAS, MO). Ixtapa: near Ixtapa, D.E. Breedlove & G. Davidse 54301 (CAS, MO); Near the Zinacantán Paraje of Muctajoc, D.E. Breedlove & G. Davidse 54007 (CAS, MO); at Escopetazo, D.E. Breedlove & G. Davidse 53947 (CAS, MO). Jitotol: 10 km N of Jitotol, D.E. Breedlove 55152 (NY); near Colonia El Laurel, ca. 5 km N of Jitotol, G. Davidse et al. 29600 (MO). La Trinitaria: E.M. Martínez S. & W.D. Stevens 23903 (MEXU, MO). Paraje of Mahben Chauk, D.E. Breedlove 7677 (ENCB); Paraje of Yehts ‘Uk’um, D.E. Breedlove 7504 (ENCB); in the Paraje of Mahosik’, D.E. Breedlove 14861 (ENCB). cozingo: Estación Chajul, reserva Montes Azules, 4 km NE del poblado de Chajul, S. Sinaca-Colín s/n (MEXU). Tenejapa: In the Paraje of Mahosik’, A.S. Ton 1187 (ENCB). Tenejapa: Kulaktik, A.M. Ton 4570 (ENCB). San Juan Cancuc: El Pozo to Oxchuc, E. Hernández & Sharp X-616 (US). Tenejapa: slopes, near Paraje Kulak’tik, D.E. Breedlove 53057 (CAS, MO); lopes west of Tih Ha’ in the Barrio of Kurus Pilal. Paraje of Mahben Chauk, D.E. Breedlove 6282 (DS). Zinacantán: from Zinacantán paraje of Paste’ to San Lucas, R.M. Laughlin 2583 (ENCB); ear Paraje Sequentic, D.E. Breedlove & G. Davidse 53910 (CAS, MO).

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!).

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.

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

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

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).

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).

Guatemala, Dept. Huehuetenango, Cerro Chémal in alpine meadow, summit of Sierra de los Cuchumantanes, 3700–3800 m, 8 Aug 1942, J.A. Steyermark 50309 (holotype: F-1202399!; isotypes: F-73211!, G-00099366 [image!], US-132785!, US-132784!, US-1935066!, US-2208672!).

Densely caespitose perennials. Culms 12–30 cm tall; leaf sheaths longer than the internodes, glabrous, smooth or scabrous; ligules 0.3–0.5(–1) mm long, apex truncate and erose; blades 5–8 cm long, 1–1.6 mm wide, flat or loosely folded to involute, scaberulous, apearing glabrous below with widely-spaced, stiff, short ascending hairs more common towards the apex, margins scabrous towards apex. Panicles 5–25(–30) cm long, open, diffuse, capillary, the base often partially enclosed by the sheath; primary branches 2–8 cm long, scabrous, naked below with very few spikelets, spreading 60–90° from the culm axis; pedicels 4–15 mm long, straight, scabrous; disarticulation above the glumes. Spikelets 3–3.5 mm long, plumbeous to dark-green turning golden brown with age; glumes 1.5–2.2 mm long, subequal, the lower a little shorter than the upper, 1-veined, apex acute, erose, often mucronate, the mucro less than 0.3 mm long; lemmas 3–3.5 mm long, lanceolate, 3-veined, puberulous, apex acute, minutely bifid, mucronate or awned between the teeth, the awn up 1.3 mm long, straight or slightly curled near apex, scaberulous; callus sparsely hairy; paleas 3–3.6 mm long, often slightly longer than the lemma, 2-veined; anthers about 1.2–1.6 mm long, purple. Caryopses not seen.

Figure 15. 

A–E Muhlenbergia quadridentata (Kunth) Trin. A habit B ligule C glumes D floret E stamens, pistil, and lodicules F–J Muhlenbergia orophila Swallen F habit G ligule H glumes I floret J stamens, pistil, and lodicules. A–E drawn from P.M. Peterson & C.R. Annable 6201 (US) F–J drawn from P.M. Peterson & C.R. Annable 11105 (US).

This species has been reported in Chiapas and the type was collected in Guatemala (Villaseñor Ríos 2016). It is also known from central México and has been reported in Ciudad de México, Hidalgo, Morelos, México, Puebla, and Tlaxcala (Espejo Serna et al. 2000; Villaseñor Ríos 2016; Sanchez-Ken 2018).

Muhlenbergia orophila is found along creeks and wet areas in pine-fir forests; 3000–3860 m.

Affinities of M. orophila are unknown and it has not yet been included in a DNA molecular study.

Guatemala. Huehuetenango: Chemal, vicinity of Chémal, summit of Sierra de los Cuchumatanes, J.A. Steyermark 50309 (MO).

Delicate, caespitose, annuals. Culms 15–90 cm tall, decumbent, rooting from flower nodes, mostly smooth and glabrous below the nodes; internodes usually glabrous to scaberulous. Leaf sheaths longer than the internodes, smooth or scaberulous; ligules 0.5–1 mm long, membranous, eciliate, irregularly erose; blades 5–15 cm long, 2–3(–5) mm wide, flat, acuminate, auriculate near base; auricles 1–1.5 mm long, falcate. Panicles 5–20 cm long, 1–3 cm wide, spiciform, linear, continuous or interrupted; primary branches 0.5–3.5 cm long, appressed, the spikelets arising just above the sterile spikelets or bristles; bristles 2–4 mm long, antrorsely scabrous; pedicels 0.1–0.2 mm long, oblong, arising just above the bristles. Spikelets 1.5–2.6 mm long, greenish to stramineous, subtended by an involucre of persistent bristles, disarticulation below the glumes; glumes 0.8–1.5 mm long, equal, narrowly awl-shaped, awned, the awns 1–3 mm long; lemmas 1.5–2.6 mm long, ovate, keeled, 3-veined, with appressed hairs below, lateral veins close to margins, scabrous, apex acuminate, awned, the awns (15–)20–30 mm long, flexuous, callus hairy, the hairs 0.3–1 mm long; palea similar to lemma; stamens 3, anthers 0.5–0.7 mm long, yellow; style 1. Caryopses 0.8 mm long, ellipsoid, with adherent pericarp. 2n = 20 (Pohl and Davidse 1971).

Figure 16. 

A–F Muhlenbergia pereilema P.M. Peterson A habit B ligule with auricles C portion of the inflorescence D glumes E floret F stamens, pistil, and lodicules G–L Muhlenbergia plumiseta Columbus G habit H ligule with auricles I portion of the inflorescence J bristles K floret L stamens and pistil. A–F drawn from A.S. Hitchcock 9050 (US) G–L drawn from C.G. Pringle 5962 (US).

Muhlenbergia pereilema ranges from throughout México to Central (Costa Rica, El Salvador, Guatemala, Honduras, México, Nicaragua, and Panama) and South America (Peterson et al. 2001).

This species occurs on grassy slopes and rocky roadsides, ravines, and barrancas in tropical and oak-pine forests; 50–2450 m.

Muhlenbergia pereilema can be separated from M. plumiseta in having persistent, scabrous bristles (plumose in M. plumiseta) and wider panicles (1–3 cm in M. pereilema and 0.2–0.6 cm wide in M. plumiseta) [Pohl 1994B; Herrera Arrieta et al. 2010; Herrera Arrieta and Peterson 2018]. This species forms a clade with M. beyrichiana Kunth and M. plumiseta within M. subg. Muhlenbergia (Peterson et. al. 2021).

Costa Rica. Alajuela: Atenas, Balsa, alrededores de las Escuela Centroamericana de Gandería, J. Gómez-L 6127 (CR); 1 km S Carrizal, open roadside in coffee plantation, R.W. Pohl & G. Davidse 11502 (US, CR); La Garita, dam in the canyon of the Rio Grande de Tarcoles, R.W. Pohl & G. Davidse 11494 (US, CR); 1 km N of Grecia, R.W. Pohl & G. Davidse 11523 (US, CR). Cartago: Roadside N of Puente Negro, N of Orosi, R.W. Pohl & M. Lucas 13153 (MO, CR); Turrialba, Près de la station de Juan Viñas, H. Pittier 1759 (CR); San Juan Norte, R. W. Pohl & G. Davidse 11435 (US, CR); vicinity of Finca Las Concavas, P.C. Standley 41551 (US). Heredia: Orillas de la vía férrea a Heredia, A.M. Brenes 13284 (CR); Barva, bordes del Río Segundo, J. León 415 (CR); El Gallito de Heredia, M. Valerio 540 (CR). Puntarenas: Paturage a Boruca, A. Tonduz 3689 (CR); Savannas de Boruca, H. Pittier (Tonduz, A.) 4450 (US, CR); Boca de Barranca, M. Montiel s.n. (USJ); Bord du chemin a Mano de Tigre, H. Pittier (Tonduz, A.) 4627 (US, CR). San José: Acosta, camino a Bajo Palma, J.F. Morales 7439 (INB, MO); Puriscal, Alto La Escalera, a lo largo del camino entre San Ignacio y Guaitil, cuenca del Pirris-Damas. Valle del Candelaria, Alto La Escalera en el camino a Bajo Arias y La Cruz, J.F. Morales & B. Hammel 6049 (MO, INB, CR); Acosta, Cuenca del Pirris-Damas, Cerros de Caraigres, cabeceras del Río La Mesa, cerca Ceiba Este, J.F. Morales & J.F. Corrales 6032 (MO, INB); Mora, Colón, le long des chemins dans la vallée du rio Jaris, prés de Pacaca, H. Pittier 3329 (CR); Mora, Colón, en la orilla del camino de lastre que va de Brasil a Ciudad Colón, S. Lobo 2309 (CR); Escazú, San Antonio, D. Santamaría 3648 (INB, MO); Bordes líneas férreas San José-Guadalupe, A. Tonduz 709 (CR); Hacienda La Esperanza, La Palma, O. Jiménez 973 (US, CR); Sur un rocher au bord du rio Virilla, sous le pont du F. C. R., près San Juan, A. Tonduz 17556 (CR); 13 km N of San Isidro de El General along carretera interamericana, R. W. Pohl & G. Davidse 11626 (US, CR); San Pedro, W.A. Archer 3888 (US); Tibas, collected along the Río Virilla about 1 km S of Santo Domingo, J. Taylor 17313 (MO). El Salvador. Ahuachapán: Ahuachapán, S.A. Padilla 134 (US); San Benito, al N de la cima del cerro La Olla, E. Sandoval & Chinchilla 767 (LAGU, MO). La Libertad: Nueva San Salvador, Jardin Botanico La Laguna, W.G. Berendsohn 1003 (LAGU, MO); Boqueron del Volcán de San Salvador, L. E. González 1851 (MO, ITIC). San Salvador: San Salvador, S. Calderón 494 (MO); San Martin, S. Calderón 1902 (US); Cerro el Guayabal, S. Calderón 1964 (US). Guatemala. Alta Verapaz, Coban, H. von Türckheim 743 (MO); Cobán, H. von Türckheim 1362 (MO); H. von Türckheim 1509 (MO, US); Area of mixed forest and clearings, hills about 10 km south of Coban, L. O. Williams et al. 40051 (US); Finca aved near Coban, W. Popenoe 903 (US). Chimaltenango: along road from Chimaltenango to San Martin Jilotepeque, P.C. Standley 57894 (US). Chiquimula: Volcan Ipala, near Amatillo, bordering lake on top, J.A. Steyermark 30491 (US). Huehuetenango: Thickets and forest in deep canyon of a tributary of Rio Blanco, about 5 km W of Aguacatan, L.O. Williams et al. 22338 (US). Jalapa: vicinity of Jalapa, pine-oak forest, P.C. Standley 76749 (US). Jutiapa: Volcan Chingo, J. Donnell Smith 3673 (US). Guatemala: Guatemala City, A.S. Hitchcock 9050 (US); Guatemala City, rocky hill, A.S. Hitchcock 9031 (US); Guatemala City, barranca north of Guatemala city, W. Popenoe 733 (US); San Antonio, Las Roces, Rojas 385 (US). Santa Rosa: Chupadero, J. Donnell Smith 3914 (US); Cerro Redondo, J. Donnell Smith 6274 (US). Solola: Mixed forest area, mountain slopes above Lake Atitlan, about 3–5 km W of Panajachel, L.O. Williams et al. 25278 (US). Honduras. El Paraíso: Yuscarán, la Piedra de Apaguiz, 3.5 km al SE de Danlí, N.P. Estrada 137 (MO, CR, TEFH); Arauca, Las Manos, 5 km N of Las Manos, near Los Limones, R.W. Pohl & M. Gabel 13429 (MO, CR); Road to Danlí, near Río San Francisco, J. R. Swallen 11196 (MO); Road to Yuscaran, J.R. Swallen 11347 (US). Francisco Morazán: Distrito Central, Cerro el Hatillo, 15 km al NE de Tegucigalpa; bosque premontano húmedo, L.M. Ordóñez 67 (MO); San Antonio de Oriente, quarry above El Zamorano, on road to San Antonio de Oriente, R.W. Pohl & G. Davidse 12505 (MO, CR); vicinity of El Zamorano, along “Wood Road”, J.R. Swallen 10821 (US); In pine woods near Piedra Herrada, Mt. Uyuca region, L.O. Williams 18543 (US); Drainage of the Rio Yeguare, Moist rocky bank near Agua Amarilla, in oak-pine forest, L.O. Williams & A. Molina R. 14723 (US). Olancho: Jutiapa Forest Camp, near Salamá. Pine forest on a steep slope above a stream, R.W. Pohl & M. Gabel 13749 (MO, CR). Mexico. Chiapas: Angel Albino Corzo: slopes of Río Cuxtepec, below Finca Cuxtepec, D.E. Breedlove & G. Davidse 54676 (MEXU, CAS). Arriaga: 13 km N of Arriaga along Mex. Hwy. 195, D.E. Breedlove & G. Davidse 54149 (CAS, MO); slope at El Sumidero, 22 km N of Tuxtla Gutierrez, D.E. Breedlove & P.H. Raven 13387 (DS); along ravines 13 km N of Arriaga along Mexican Highway 195, D.E. Breedlove 28278 (MO). Cintalapa: 23 km W of Las Cruces along road to La Mina Microwave Station, D.E. Breedlove & G. Davidse 54092 (CAS, MO). Chiapa de Corzo: above El Chorreadero, D.E. Breedlove & G. Davidse 54032 (MEXU, CAS, MO); 36 km E of Tuxtla Gutierrez, F.W. Gould & S. Hatch 14374 (ISC, DS); Ixhuatán: 2 km al N of Ishuatan, G. Davidse et al. 29641 (MEXU, MO). Ixtapa: intersection of Tuxtla Gutiérrez-San Cristobal de las Casas and Villahermosa, G. Davidse et al. 30104 (MEXU, MO); near Ixtapa, D.E. Breedlove & G. Davidse 54264 (CAS, MO); along Mex Hwy 190 in the Zinacantan paraje of Muctajoc, D.E. Breedlove 13819 (DS). Motozintla: Motozintla de Mendoza, 25–27 km NE of Huixtla along rd to Motozintla SW of Toliman, D.E. Breedlove 28593 (CHAPA, MEXU, DS, MO); Ejido Toliman, sobre la carr. Huixtla-Motozintla. Vega de Arroyo, Gómez et al. 185 (MEXU). Tenejapa: In the paraje of Mahosik’, D.E. Breedlove 16146 (DS). Villa Corzo: Above Colonia Vicente Guerrero on road to Finca Cuxtepec, D.E. Breedlove & L. Strother 46573 (CAS, MO); Above Colonia Vicente Guerrero on road to Finca Cuxtepec, D.E. Breedlove & G. Davidse 54567 (MEXU, CAS, MO). San Fernando: Parque Nacional del Sumidero, 20–22 km NW of Tuxtla Gutiérrez, G. Davidse et al. 29767 (MEXU, MO). Nicaragua. Rivas, Volcán Concepción, Isla Ometepe, plantas propias de la lava, W. Robleto T. 157 (MO, CR). Panama. Coclé, vicinity of Ola, H. Pittier 5046 (US).

Tufted annuals. Culms 3–27 cm tall, erect, glabrous. Leaf sheaths usually longer than the internodes, smooth or scabridulous; ligules 1.5–3 mm long, membranous, acute; blades 1–5 cm long, 0.6–1.5 mm wide, flat to involute, smooth or scabridulous abaxially, sometimes shortly pubescent adaxially. Panicles 2–8 cm long, 0.3–3.4 cm wide, contracted or open; primary branches 1–5 cm long, diverging up to 80° from the rachises; pedicels 0.4–5 mm long, smooth or scabrous. Spikelets 1.4–4.2 mm long, 1-flowered; glumes smooth or scabridulous; lower glumes 0.8–2.8 mm long, narrow to broadly lanceolate, 1-veined, acute, often awn-tipped; upper glumes 0.9–3 mm long, wider than the lower glumes, lanceolate, 3(2)-veined, truncate to acute, 2- or 3-toothed; lemmas 1.4–4.2 mm long, ovate, widest near the base, purplish mottled with dark green areas, hairy on the calluses and lower 2/3 of the lemma bodies, hairs to 0.5 mm long, apices acuminate, usually bifid and awned from between the teeth, teeth to 0.5 mm long, awns 3–10 mm long, flexuous, purplish; paleas 1.3–3.8 mm, narrowly lanceolate, acuminate to subacute; anthers 0.5–1 mm long, purplish to yellowish. Caryopses 1–1.6 mm long, fusiform, brownish. 2n = 30.

Muhlenbergia peruviana occurs in Arizona and New Mexico, U.S.A, throughout México to Guatemala, and then in Argentina, Bolivia, Chile, Ecuador, and Peru (Peterson and Annable 1991).

Grassy flats, open gravelly flats, rock outcrops, sandy washes, gravelly drainages, wet or dry meadows, canyons, gravelly or sandy slopes, valleys, shores along lakes, open ridgetops, and disturbed road cuts associated with Aciachne pulvinata Benth., Anatherostipa, Berberis, Colletia spinosissima, Ephedra, Festuca orthophylla Pilg., Festuca ssp., Jarava, Juncus, Lepidophyllum, Luzula, Margyricarpus, Monnina, Muhlenbergia ssp., Nassella, Plantago, Poa ssp., Polylepis, Puya, Pycnophyllum, Salvia oppositiflora Ruiz & Pav., Stevia, Tagetes; 3000–4900 m.

As treated here, Muhlenbergia peruviana includes (as synonyms) what was sometimes identified as M. pulcherrima Scribn. ex Beal (southwestern USA and northern México) and M. pusilla Steud. (central México to Guatemala). There are many more morphological forms than just these, and since the only chromosome count of this species suggests triploidy (2n = 3x =30), perhaps this species is apomictic (Reeder 1968). We believe apomixis is occurring in this species but that it is not obligate, and that gene flow takes place sporadically to form intermediates maintained by asexual seed formation (Peterson and Annable 1991).

In a molecular DNA sequence analysis Muhlenbergia peruviana is sister to M. crispiseta Hitchc., another annual known only from Texas and north central México, and this pair is embedded in the strongly supported M. subg. Clomena clade (Peterson et al. 2010b, Peterson et al. 2021). Members of M. subg. Clomena possess spikelets with upper glumes that are 3-veined and often 3-toothed and have a densely caespitose habit (Peterson et al. 2010b). Muhlenbergia peruviana can be separated from M. crispiseta in having purplish irregularly flexuous, purplish awns (versus sinuous-wavy, crisped and curled, olive-green awns in M. crispiseta) and narrow, gradually acuminate lemmas (versus lemmas that are plump near middle) [Peterson and Annable 1991].

Guatemala. Huehuetenango: La Capellania, Sierra de los Cuchumatanes, 1.0 miles NW of La Capellania on hwy 9N and 12.3 miles N of Huehuetenango, P.M. Peterson & C.R. Annable 4683 (GH, MEXU, MICH, MO, NY, RSA, UC, US, WS); Tojiah, Sierra de los Cuchumatanes, 3 miles SW of Tojiah on hwy 9 N., P.M. Peterson & C.R. Annable 4698 (GH, MO, NY, RSA, US, WS); Treeless paramo-like plain near Calaveras, L.O. Williams et al. 21961 (US). San Marcos: Tacana, Volcán Tacaná, M. Véliz et al. 10587 (MO). Mexico. Chiapas: NW de Motozintla de Mendoza on road to El Porvenir, P.M. Peterson & C.R. Annable 4712 (US); 13 mi NW de Motozintla de Mendoza off road to El Porvenir at top of cumbre below tower, P.M. Peterson & C.R. Annable 4714 (US).

Figure 17. 

A, B Muhlenbergia phalaroides (Kunth) P.M. Peterson A culm with inflorescence B spikelet C–F Muhlenbergia tenella (Kunth) Trin. C habit D ligule E glumes F floret. A, B drawn from S. Lægaard 71419 (AAU) C–F drawn from P.M. Peterson & C.R. Annable 4755 (US, WS).

Perennials , intricately branched near base. Culms 10–30 cm tall, erect, mostly glabrous, usually decumbent and sprawling below, bent at the pubescent to short pilose nodes; internodes 0.4–10(–15) cm long, pubescent to short pilose. Leaf sheaths much shorter than the internodes above, hyaline near the margins, pilose near summit; ligules 0.4–1 mm long, membranous, apex truncate to deltoid, often erose and lacerate; blades 0.5–6.5 cm long, 0.5–1.2 mm wide, shorter near the base of culms, flat, folded or loosely involute, lanate above and glabrous or with scattered, short appressed hairs below, margins whitish-thickened, apex navicular, occasionally with a short seta, seta usually less than 2 mm long. Panicles 1.5–6.5 cm long, 3–8 mm wide, spiciform and spikelike, densely flowered, often interrupted below with only a few spikelets, terminal or axillary; rachis lanate to hispid, the short hairs antrorse, appressed; primary branches 1.5–7 mm long, very short, the spikelets usually in pairs, rarely 1 or 3 per terminal branch, when in pairs the lower short-pedicelled spikelet perfect, staminate or sterile and the upper longer-pedicelled spikelet usually perfect; pedicels 0.3–1.4 mm long; disarticulation usually at the base of the pedicel, each spikelet falling as a unit leaving a small cuplike tip. Spikelets 3–4 mm long, stramineous with plumbeous mottles, sometimes additionally with purplish mottles; glumes 1–2.1 mm long, shorter than the lemma, subequal, 1–3-veined; lower glumes commonly 2 or 3-veined, usually 2-awned, occasionally 1 or 3 awned, the awns 1–3 mm long, equal or subequal, scabrous, recurved; upper glumes commonly 1-veined, usually 1-awned, the awns 1–2.5 mm long; lemmas 3–4 mm long, narrowly lanceolate, 3-veined, margins hirsute to lanate and occasionally the lower ½ sparsely hairy, the hairs 0.1–0.3 mm long, apex usually awned, occasionally unawned or mucronate, the awns 1–3 mm long; paleas 2.8–3.8 mm long, hairy between the veins, the veins occasionally extending as mucros; anthers 1.3–2 mm long, yellowish. Caryopses 1.7–2 mm long, fusiform, brownish.

Muhlenbergia phalaroides ranges from México to South America where it is found in Argentina, Bolivia, Columbia, Ecuador, and Peru (Reeder 1985; Sánchez and Rúgolo de Agrasar 1986; Davidse and Pohl 1994).

This species occurs in open grasslands and savannahs on steep rocky slopes flats, and along disturbed irrigation canals in deep clayish-loam to sandy soils associated with Baccharis, Berberis, Cheilanthes, Condalia, Dodonaea viscosa, Eragrostis, Jarava ichu Opuntia, Muhlenbergia cenchroides, M. rigida, Nassella, Plantago, Puya, and Sporobolus indicus (L.) R. Br.; 2800–3500 m.

Muhlenbergia phalaroides is morphologically similar to M. phleoides (Kunth) Columbus known in the southwestern USA and México, and M. alopecuroides (Griseb.) P.M. Peterson & Columbus found in the southwestern USA, México, and disjunct in Argentina and Bolivia (Reeder 1985; Davidse and Pohl 1994, Renvoize 1998; Peterson and Giraldo-Cañas 2012). Muhlenbergia alopecuroides differs from M. phalaroides in having leaf blades with terminal seta (3–)4–7(–12) mm long and ligules (2–)3–12 mm long whereas M. phleoides differs in having auriculate ligules 1–2 mm long (Reeder 1985; Peterson 2003). These morphological differences are perhaps better recognized at the subspecific level but there are no population studies comparing these three species, other than Peterson and Morrone (1997) who investigated populations of only the amphitropical, M. alopecuroides [as Lycurus setosus (Nutt.) C. Reeder].

Muhlenbergia phalaroides probably lies within M. subg. Pseudosporobolus, although the species has not been included in a DNA-derived phylogeny, aligning with M. alopecuroides and M. phleoides (Peterson et al. 2021). Many members of this subgenus have narrow panicles, plumbeous spikelets with unawned, mucronate or short-awned lemmas (Peterson et al. 2010b).

Guatemala. Quetzaltenango: Chiquilaja, potreros naturales y secos, M. de Koninck 63 (US). Mexico. Chiapas: San Cristóbal: NE edge of San Cristóbal de Las Casas, D.E. Breedlove & G. Davidse 46039, 54734 (MEXU). Teopisca: N of Teopisca, D.E. Breedlove & G. Davidse 54768 (MEXU).

Perennials with slender, scaly rhizomes; rhizome scales 7.5–16 mm long, acute often deteriorating with age. Culms 10–40(–50) cm tall, erect, decumbent near base, little or much branched below, glabrous; internodes 0.4–6 cm long, glabrous, smooth to nodulose-roughened, the nodes green or purple, constricted. Leaf sheaths 1–5 cm long, mostly longer than the internodes, glabrous, margins hyaline; ligules 0.3–0.5(–0.7) mm long, membranous, truncate, decurrent; blades 2–10(–12) cm long, 1–2.4(–3.0) mm wide, flat or folded, glabrous. Panicles 4–9(–14) cm long, 0.5–4(–8) cm wide, open, usually well exerted with 6–12 branches; primary branches mostly 2–8 cm long, ascending and spreading up to 50° from the culm axis, with 3–30 spikelets, widely spaced, naked below, one per node, scabrid; pedicels 0.5–2 mm long, shorter than the spikelets, scaberulous. Spikelets 2.5–3.2(–3.5) mm long, plumbeous; glumes 1–1.6 (–1.8) mm long, shorter than the florets, equal or subequal, the upper often slightly longer than the lower, 1-veined, apex acute; lemmas 2.2–3(–3.3) mm long, lanceolate to ovate, glabrous or occasionally scabrous, faintly 3-veined, dark green, apex acute; paleas 2–2.8(–3.1) mm long, about as long as the lemma, glabrous, faintly 2-veined, apex acuminate; anthers 1.4–2 mm long, dark green or purplish turning yellow with age. Caryopses 1.4–1.6 mm long, ellipsoid, greenish-brown. 2n = 40 (Reeder 1967).