14 
(a) Cluster not hairy at the base. 
1. H. cenchroides H. B. K. var. Texana Vasey Contr. Nat. Herb. 1.53, Perennial, 
low, tufted, multiplying by shoots or runners from the base, forming new tufts at 
intervals of 3 toGinches. Flowering culms 6 ‘to 12 inches high, slender, nodes ciliate ; 
leaves small, rigid, 1 to 3inches long, becoming involute, ciliate on the margins; 
spike of 5 to 8 joints, slender, clusters loosely, imbricated ; spikelets about 3 lines 
Jong, connate at base, the male ones each 2-flowered, the fertile one pistillate only ; 
glumes of the fertile flower awned on the back above the middle, the male ones 
unawned.—Texas to Arizona, 
Differs from the type in the taller and more slender culm, longer leaves, longer and 
more slender spike, with more numerous, looser clusters. 
(b) Clusters densely hairy at the base. 
2. H. mutica Benth. (Buckl. Proc. Acad. Phil. 1862, p. 95.) Rhizoma creeping, 
strongly rooted ; culmstufted, ascending at the base, 1 to 2 feet high, leafy; leaves 
rigid, erect, 2 to 3 inches long, acuminate, scabrous, lower sheaths longer than the 
internodes, ciliate at the throat; spike cylindrical, 2 to 3 inches long; clusters 3 to 
4 lines long; two lateral spikelets, each 2- to 3-flowered, the empty glumes cuneate, 
ciliate ou margins and fimbriate at apex, unawned ; empty glumes of central spikelet 
shorter than its flower, narrowly cuneate, laciniate at apex, with a short spreading 
awn near the apex; the thin glumes of the male spikelets spreading or often re- 
flexed at maturity.—Texas and Arizona. 
3. H. Jamesii Benth. (Coult. Rocky Mt. FI. p. 405.) Rhizome creeping, 
strongly rooted ; culms tufted, 6 to 18 inches high, leafy below; leaves rigid, 2 to 
4 inches long, the lowest with loose, large sheaths; spike about 2 inches long, wider 
than the preceding ; clusters 4 to 5 lines long; male spikelets 2-flowered, the empty 
glumes linear-lanceolate, 5-nerved, ciliate on the margins, the outer with an awn 
from the back about the middle, longer than the spikelet, the inner one unawned; 
the female spikelet with the empty glumes ciliate on the margin, cuneate below, 
above 2-lobed and laciniate into 5 to 7 slender teeth, and awned between the lobes.— 
Texas, New Mexico and Colorado, 
4. H. rigida Scribn. (Pleuraphis rigida Thurber Bot. Cal. 11. p. 293.) Perennial ; 
culms 2 to 3 feet high, solid, and almost woody below, much branched, clothed 
within the sheaths with a dense matted tomentum; the lower leaves pubescent, par- 
ticularly on the lower surface, 4 to 5 inches long, the uppermost about 1 inch, 
very rigid, becoming involute, setaceously pointed ; sheaths crowded below, loose, 
pubescent; panicle 3 to 4 inches long, dense, pale or purplish; outer glumes cun- 
eate at base, bitid above, woolly-fringed, 3- to 5-nerved, the central nerves excurrent 
just below the middle as a stout divergent awn a little exceeding the glume, the two 
or three lateral nerves produced as sete" between the lobes and about equalling 
them; the floret stipitate; the flowering glume broad, oblong, 3-nerved, irregularly 
toothed and fringed above, with a short central awn, palet equalling or slightly 
exceeding its glume; outer glumes of the lateral spikelets similar to those of the 
central one; one or more of the nerves excurrent as awns, the flowering glume and 
palets of the two male flowers similar to those of the fertile one-—The most valuable 
grass of the desert regions in Arizona and Southern California, 
This description is, with little alteration, from Prof. Thurber, in Bot. California. 
ZIGOPOGON H. & B, 
Inflorescence in loose, one-sided terminal and lateral spikes or 
racemes; the spikelets 1-flowered, in clusters of two or three, one 
usually sterile or male only. The outer glumes are cuneate, emarginate 
