GENERA OF GRASSES OF THE UNITED STATES. 169 



mesquite. It is a low grass, forming wiry stolons that in favorable 

 soil produce a close, firm sod. The flowering culms are a few inches 

 high and terminate in a short spike. Curly mesquite is an important 

 grazing grass of the uplands of Texas. Our species has commonly 

 been referred to the related, H. cenchroides^ of Mexico. 



Hilaria jamesii (Torr.) Benth. (fig. 99), an erect grass about a 

 foot high, with glumes narrowed above, is found from Wyoming to 

 Texas and southern California. This is called galleta grass in New 

 Mexico. HUaria mutica (Buckl.) Benth., found from Texas to Ari- 

 zona, differs from the preceding in having some of the glumes broad- 

 ened above. This species is sometimes called tobosa grass. Hilaria 

 rigida (Thurb.) Benth., with felty pubescent branched culms, is 

 found from Utah to southern California. This also is called galleta 

 grass. All the species of Hilaria are important range grasses. The 

 last three species, with scaly rhizomes instead of stolons and with 

 glumes bearing an awn on one side, compose Pleuraphis, held by 

 some as a genus distinct from Hilaria. 



81. AEGOPOGON Humb. and Bonpl. 



Spikelets short-pedicellate, in groups of 3, the group short- 

 pedunculate, spreading, the peduncle disarticulating from the axis 

 and forming a pointed stipe below the group, this falling entire; 

 central spikelet shorter pedicellate, fertile, the 2 lateral ones longer 

 pedicellate and staminate or neuter; glumes membranaceous, notched 

 at the apex, the midnerve extending into a point or awn ; lemma and 

 palea thinner than the glumes, extending beyond them, the lemma 

 3-nerved, the central nerve and sometimes also the lateral ones extend- 

 ing into awns, the palea 2-awned. 



Annual low, lax grasses, with short, narrow, flat blades and loose 

 racemes of delicate flower clusters. Species three, Arizona to Bolivia, 

 one within the United States. 



Type species : Aegopogon cenchroides Humb. and Bonpl. 



Aegopogon Humb. and Bonpl. ; Willd. Sp. PI. 4 : 899. 1806. Only one species 

 is described. 



Hymenothecium Lag., Elench. PI. 7. 1816. In the Elenchus, a list of seeds, 

 occurs Hymenothecium tenellum Lag. based on Cynosurus tenellus Cav. The 

 genus was published as new by Lagasca in Genera et Species Plantarum, a 

 work appearing in the same year as the preceding but supposed to be some- 

 what later. In this work (p. 4) four species are given, H. unisetum, H. 

 tenellum, H. trisetum (Cynosurus gracilis Cav.), and H. quinquesetum. Cy- 

 nosurus tenellus Cav. is accepted as the type. 



Schellingia Steud., Flora 33: 231, pi. 1. 1850. -Type, 8. tenera Steud., the 

 only species described. This is Aegopogon cenchroides. 



The only species in the United States is Aegopogon tenellus (Cav.) 

 Trin. (fig. 100), a Mexican species extending into southern Arizona. 

 It is a pretty little grass, but is of no economic importance. 



