No. 2. 
HILARIA RIGIDA (Thurb.) Serib. (Pleuraphis riqida, 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, 1 to 2 feet tall, woolly 
below. : 
Leaves of rootstock appressed, scarious scales; of culm often 2-ranked and 4 
rather crowded; sheaths longer than internodes, close, woolly; blades involute, — 
pungent, rigid, | to 3 inches long; ligule a dense white, woolly collar. ‘i 
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. 4 
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, 5-to 6-nerved, with 
1 or 2 dorsal awns; floral glumes obiong 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 24 ions 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, equall 
2-lobed, ciliate, 2 to 3 lines long, 3-nerved, lateral nerves equal and slightly excur- 
rent, midnerve excurrent in an awn 4 to 1 line long; palet lance-oblong, obtuse, 
ciliate or lacerate at apex, 2-nerved, 2 to 3 lines long; stigmas 2, long, plumose. 
rains; no mature grains found. 
PuateE II; a to d, parts of staminate flower; a, first empty glume; b, second 
empty glume; ¢, floral glume; d, palet; e, perfect flower with its two empty 
glumes; f to h, parts of perfect flower; f, floral glume; g, palet; hk, 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, 
