Muhlenbergia aurea Swallen, Contr. U.S. Natl. Herb. 29(9): 411. 1950.

Peterson, Paul M., Herrera Arrieta, Yolanda, Lobo Cabezas, Silvia & Romaschenko, Konstantin, 2023, Taxonomic revision of Muhlenbergia (Poaceae, Chloridoideae, Cynodonteae, Muhlenbergiinae) in Central America: phylogeny and classification, PhytoKeys 230, pp. 1-106 : 1

1. Muhlenbergia aurea Swallen, Contr. U.S. Natl. Herb. 29(9): 411. 1950.

Fig. 2A-E

Type.

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!) .

Description.

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.

Phenology.

Flowering December and January.

Distribution.

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).

Ecology.

Muhlenbergia aurea occurs on slopes between 1300 and 1500 meters.

Comments.

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 .

Specimens examined.

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) .

Figures

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).