No. 11. 



HILARIA MUTICA Bentham. 



Plants perennial. 



Roots thick, simple, with a cork-like covering. Rootstock creeping, woody, 

 scaly-sheathed. 



Culms erect or from an ascending base, 9 to 20 inches high, somewhat tnf ted, 

 usually with many sterile branches below, glabrous, sometimes hairy at the nodes. 



Leaves of the stem 4 to 10; sheaths imbricated below, distant above, glabrous, 

 the margins sometimes ciliate above; blade 1 to 1| lines broad, reaching 6 inches 

 long, flat or involute, usually slightly scabrous, otherwise smooth; ligule about \ 

 line long, fimbriate. 



Inflorescence a close spike, pedunculate or scarcely exserted, 1-J to 3 inches 

 long; spikelets arranged in clusters of 3 on opposite sides of the flat rachis, imbri- 

 cated. 



Spikelets 2 to 3 lines long, with a tuft of long hairs surrounding the cluster 

 at the base. 



(1) Middle Spikelets. 



Glumes 3; first and second alike, oblanceola,te, 1 -nerved at the base, with cili- 

 ate membranaceous margins, the nerve splitting above into several branches, con- 

 tinued into short aristse, or the lateral ones joined into a fimbriate membrane3 

 third (flowering) glume membranaceous, linear, obtuse, 3-nerved. 



Flower hermaphrodite. Stamens 3; anther narrow-linear, \ to 2 lines long, the 

 narrow cells free at the ends. Styles 2, long; stigmas long, narrow-cylindrical, 

 with thick bodies, exserted from the apex of the tube formed by the palet and 

 glume. 



(2) Lateral Spikelets. 



Glumes commonly 5 to 6; two lower empty, upper successively shorter, apices 

 of all even; first lanceolate, several-nerved, ciliate on the membranaceous margins 

 and apex, usually with a short lateral awn on the margin nearest the middle 

 spikelet; second similar, but linear and unawned; flowering glumes narrowly quad- 

 rangular-oblong, truncate, membranaceous, 3-nerved. 



Flowers staminate. Palet similar to the glume but narrower,' 2-nerved. 

 Stamens 3, similar to those of the middle spikelet, those of the upper flowers suc- 

 cessively shorter. 



Grain inclosed in the finally coriaceous and shining flowering glume and 

 palet, these remaining attached in the cluster of spikelets, the whole dropping off 

 together. 



Plate XI; a, two lateral spikelets of a cluster, and b, middle spikelet opened 

 to show the parts. The cluster is viewed from the side toward the rachis of the 

 spike. The lateral awn of the two glumes uppermost in a is not shown, nor are the 

 stamens of the upper flowers of the lateral spikelets shown. In b, the styles are 

 those of an unopened flower, and in all cases the cells of the anthers are repre- 

 sented as united even to their ends. 



This species and another similar one (H. Jamesii) are called gietta by the 

 Mexicans, and in some localities also called 'black grama.' In southern New 

 Mexico and Arizona they are the prevailing grama grasses, taking the place of the 

 white grama (Bouteloua oligostachya) which covers the plains of western Kansas 

 and Nebraska. The species here described is one of the most important forage 

 grasses of this region. 



