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 tufted, 
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 14 lines broad, reaching 6 inches 
long, flat or involute, usually slightly scabrous, otherwise smooth; ligule about 4 
line long, fimbriate. 
Inflorescence a close spike, pedunculate or scarcely exserted, 14 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, oblanceolate, 1-nerved at the base, with cili- 
ate membranaceous margins, the nerve splitting above into several branches, con- 
tinued into short ariste, or the lateral ones joined into a fimbriate membrane; 
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, saverinbeved: 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; tlowering —— harsowly 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 @ is not shown, nor are the 
stamens of the upper flowers of the lateral spikelets shown. In 3, 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. 
