G68 

 HILARIAS 



Hila'ria spp., syn. Pleura'phis spp. 



Individual names are applied to each species of Hilaria but the 

 genus as a whole has had no common name, so the scientific name 

 is usually employed. This genus was named in honor of Auguste de 

 Saint-Hilaire, an early French naturalist. There are four species of 

 Hilaria, all perennials, in the United States, distributed from Wy- 

 oming to Nevada, southern California, central Texas, and south 

 into Mexico. These grasses are all semidesert and desert plants, 

 growing principally on arid plains, mesas, and foothills, often in 

 association with gramas (Boutcloua spp.), three-awns (Aristida 

 spp.), dropseeds (Sporobolus spp'.), and mesquites (Prosopis spp.). 

 They occur on a wide variety of soils from clay adobe flats to 

 gravelly or rocky ridges. Some authors prefer to divide these grasses 

 into two genera, leaving only one species, curly-mesquite (H. belan- 

 geri y syn. "H. cenchroides" of United States authors), which has 

 stolons and glandular glumes, in Hilaria, and classing the others, 

 which have rootstocks and nonglandular glumes, in the genus 

 Pleuraphis. The best current botanical opinion, however, unites the 

 two groups into one genus. 



Because of their abundance, ability to withstand heavy grazing and 

 prolonged drought, and the fairly large volume of forage which 

 some species produce, the hilarias are important grasses on many 

 ranges of the Southwest. Their strong creeping rootstocks or 

 stolons make them invaluable as soil binders. 



Hilarias have narrow, flat, or inrolled leaves, and solid (pithy, as 

 cornstalks), tufted, somewhat wiry or woody stems which are usually 

 bent at the base and branched. The spikes are very distinctive, 

 resembling somewhat those of the wild- ryes (Elymus spp.) and 

 wheatgrasses (Agropyron spp.), but are readily recognized by their 

 broad, papery glumes, which make the entire spike appear somewhat 

 chaffy and papery. The spikelets are borne in close, stemless clusters 

 alternately arranged on a zigzag main stem (rachis). Each cluster 

 comprises three spikelets the center one seed-producing, one- 

 flowered, and the outer two not seed-producing and two-flowered. 

 The entire cluster falls at maturity, leaving the rachis naked. 



