GRIFFITHS—-THE GRAMA GRASSES. 397 
unfavorable conditions sometimes reduced, in stunted plants, to 2 to 4; spikes pedun- 
culate, the peduncles about 1 mm. long, these, together with the rachis densely white- 
hairy over the entire surface or only on the angles, the pubescence diminishing in quan- 
tity distally to only scattering hairs upon the distal prolongation of the rachis; spikelets 
2 to4, the lowermost more or less aborted, loosely arranged, about 2 mm. apart, consisting 
of a perfect floret and a rudiment, this reduced or usually absent in the lower spikelet; 
first glume 1.5 to 2 mm., the second 5 to 6 mm, long, minutely scabrous-keeled, both 
narrow, acuminate; lemma with three, very short, nearly equal, minutely scabrous 
awns, pubescent, mostly on the 3 nerves, 6 to 8 mm, long; palet smooth, with two 
very short, very minutely scabrous awns, about 5 to 6.5 mm. long; rudiment consisting 
of 3 long, scabrous awns upon a 
hairy stipe, 1 mm. long, bearing a 
tuft of longer hairs at its apex, the 
central awn slightly glumaceous 
at base and about 2 mm. shorter 
than the lateral, the whole rudi- 
ment being about 7 mm. long; 
caryopsis cylindrical-oblong, 3 
mm. long, 0.4mm, wide, grooved 
on the dorsal surface, the scutel- 
lum about three-fourths the 
length of the ventral surface. 
(Puate 77, A, B. Ficure 49.) 
The species inhabits the drier 
desert. mesas and foothills from 
western Texas to the Pacific coast 
and is as variable as the seasons 
and conditions in this most vari- 
able region, Often it will mature 
its seed upon a single culm | or 
2 cm. high, or it may produce 
plants with 50 culms 70 cm. in 
height. Often the spikes are not 
over 3 or 4 mm. in length and 
produce but a single seed, while 
in Palmer 51 some spikes are fully 
2.5 em. in length. The habits 
of growth of this species particu- 
larly fit it for a desert habitat. Fic. 49.—Boutcloua aristidoides. a, Spikelet; 6, c, lemma and 
It is an annual, producing an palet of first floret; d, rudiment; ¢, two views and cross sec- 
. tion of caryopsis. a, Scale 7.5; b-e, scale 10. From Griffiths 
abundance of seeds which have jag. yor , , ffi 
their special methods of dis- 
semination by burrowing into the ground and thus enable it to persist where 1ess 
aggressive plants fail, When mature the spike, together with the short, sharp-pointed 
peduncle, drops off entire. This callus-like peduncle is thickly beset with short, 
stiff, retrosely arranged hairs, which, together with the awns of the spikelets and the 
recurved awn-like prolongation of the rachis, assist in the burial of the seed or its 
adhesion to anything with which it may come in contact. 
This is doubtless one of the least valuable of the abundant species of this genus. 
Usually no grazing is done upon it during the time that it is ripening, and, where very 
EXPLANATION OF PLATE 77.—A. A very large plant of Bouteloua aristidoides from a favorable depression 
in desert mesas east of Tucson, Arizona. B. A nearly pure stand of the same upon the desert mesas north 
ofthe Santa Rita Mountains of Arizona, in a very favorable season, 
