Muhlenbergia xanthodas Soderst., Contr. U.S. Natl. Herb. 34: 173. 1967.

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

38. Muhlenbergia xanthodas Soderst., Contr. U.S. Natl. Herb. 34: 173. 1967.

Fig. 2F-H

Type.

México, Chiapas, collected on rock on Mt. Ovando , 2300 m, 14-18 Nov 1939, E. Matuda 4003 (holotype: US-1817864!; isotypes: F-64101, F-64108!, GH-00024052 [image!], NY-00381481 [image!], NY-00381482 [image!], US-2075810!) .

Description.

Densely caespitose perennials. Culms 50-100 cm tall, glabrous. Leaf sheaths compressed-keeled, glabrous, minutely scabrillose near the collar; sheath auricles absent; ligules (3-) 6-13 mm long, delicate, hyaline, frayed with age, scarcely decurrent, becoming somewhat firm at base; blades 30-50(-70) cm long, 2-4 mm wide, conduplicate, becoming involute towards the apex, scabrous, apically long attenuate, the margins scabrous. Panicles 20-45(-55) cm long, 2-3(-4) cm wide, erect, golden yellow to yellowish-brown; primary branches 4-6 (-7) cm long, tightly appressed with spikelets to the base; pedicels shorter than the spikelets, thin, usually straight, scaberulous and often with a few hairs near the apex. Spikelets 2-3 mm long; glumes 2-2.5(-3) mm long, about equal in length, mostly smooth, somewhat lustrous and shining, translucent, unveined, apex acute; lemmas (2-)2.5-2.9 mm long, as long as the glumes or shorter, mostly glabrous or with a few appressed and very short trichomes at the base of the central vein, the awns (5-)6-20 mm long, golden; callus short-pilose; paleas as long as the lemma or a little longer, glabrous; anthers 1.5-2 mm long. Caryopses not seen.

Distribution.

Muhlenbergia xanthodas is known from Guatemala and Chiapas, México ( Sanchez-Ken 2018).

Ecology.

This species is found on rocky limestone slopes in deciduous tropical forests; 1500-2300 m.

Comments.

Morphologically, M. xanthodas is similar to M. aurea but differs in having longer spikelets 2-3 mm long (1.7-2.2 mm long in M. aurea ) and veinless glumes (1-veined in M. aurea ) with the upper mucronate.

Specimens examined.

Guatemala. Huehuetenango. Clearings and mixed forest in mountains near El Reposo, about 8 km from Mexican frontier, L.O. Williams et al.41241 (MEXU); Canyon of Río Seligua, in "El Tapón” near Monos bridge, 40 km, NW of Huehuetenango, L.O. Williams et al.41263 (MEXU). Mexico. Chiapas. Altamirano: 15 km Norte a colonia Puebla Nueva, A. Pérez M. 221 (MEXU); Ixtapa: Intersection of the Tuxtla Gutiérrez-San Cristóbal de las Casas and the Villahermosa highways, G. Davidse et al. 30101 (MEXU); San Fernando: Parque Nacional del Sumidero, 222 km NW of Tuxtla Gutiérrez, along the road to the canyon outlook, G. Davidse et al. 29764 (MEXU); Tenejapa: Ojo del Río Yash zanal, Alush Méndez Ton 5322 (MEXU); Tuxtla Gutiérrez: 18 km NE de Tuxtla Gutiérrez, carr al cañón del Sumidero, A.J. Zenón, Ruíz y Valle # 2 (CIIDIR); Between Escuiplas and Cañada Honda, Hernández X. & Sharp X-311 ( US).

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).