'No. 2. 

 HILARIA RIGIDA (Thurb.) Scrib, (Pleuraphis riaida. Thurb.) 



Plant perennial, rigid, woody throughout, except the young growth, with 

 hard creeping rootstock sending up scaly branches. 



Culms spreading or ascending, branching freely, solid. I to 2 feet tall, woolly 

 below. 



Leaves of rootstock appressed, scarious scales; of culm often 2-ranked and 

 rather crowded; sheaths longer than internodes. close, woolly; blades involute, 

 pungent, rigid. 1 to 3 inches long: ligule a dense white, woolly collar. 



Inflorescence a narrow, white or purplish spike. 2 to 3 inches long, formed 

 of obovate clusters of 3 sessile spikelets at each node of the rachis. 



Spikelets; lateral ones in the cluster staminate and 2- to 3-flowered, middle one 

 perfect and 1-flowered; empty glumes all about 3 lines long, forming an involucre 

 about the cluster; first glume of staminate spikelet oblong, wider above, oblique, 

 conspicuously ciliate, 5-nerved, 1 or 2 of the nerves on one side extended in short 

 dorsal awns, second glume obovate, 2-lobed and ciliate above, o-to 6-nerved, with 

 1 or 2 dorsal awns; floral glumes oblong or wedge-shaped, nearly equally 2-lobed 

 at apex or merely obtuse, ciliate, 3-nerved, midnerve slightly excurrent, and one 

 lateral nerve rather obscure, 2 to 2| lines long; palet oblong, truncate, slightly 

 scabrous on the two nerves above, 2 lines long; empty glumes of perfect 

 flower equal, at the back of the cluster, narrow, cuneate, oblique above, 4 to 

 6 awned, ciliate, 2 to 3. lines long including awns; floral glume oblong, equally 

 2-lobed, ciliate, 2 to 3 lines long, 3-nerved, lateral nerves equal and slightly excur- 

 rent, midnerve excurrent in an awn ^ to 1 line long; palet lance-oblong, obtuse, 

 ciliate or lacerate at apex, 2-nerved, 2 to 3 lines long; stigmas 2, long, plumose. 



Grains; no mature grains found. 



Pla.te II; a to d, parts of staminate flower; a, first empty glume; b, second 

 empty glume; c, floral glume; rf, palet; e, perfect flower with its two empty 

 glumes; /to h, parts of perfect flower; /, floral glume: f/. palet: h. empty glume. 



New Mexico and Arizona; almost the only grass on the driest desert land; 

 commonly called Gayetta grass. It is considered a valuable grass. 



