1 BULLETIN 367, U. S. DEPARTMENT OF AGRICULTURE. 
clder stockmen of the region, claims that have seemed to the writer 
at times very hard to believe and very easy to discount at a high rate. 
It is not intended to imply by what has been said that the black 
grama is the dominant plant of the area here called by itsname. The 
area in question is largely covered by large shrubs, such as mesquite, 
cat’s-claw, palo verde, and cacti of various kinds. Besides these, there 
are the spring and summer annuals occurring in greater or less pro- 
fusion according to the season. The writer has not seen the abun- 
dance of Atriplex elegans mentioned by Griffiths? in the region, 
nor some of the other species referred to, but the amount of grass in 
that region has increased considerably. Besides the annuals, crow- 
foot grama has spread as far north as the north fence and is pushing 
westward. 
Along the west fence, on the broken, gravelly ridges, considerable 
wire grama (Bouteloua eriopoda), some Dasychloa pulchella, and 
less six-weeks grass occur associated with the black grama. The wire 
grama is very much like the black grama in its habits as a plant and 
its value as forage, and the treatment which would suit the one would 
satisfy the other. The two together, if given a chance, would doubt- 
less put a crop of forage on much of southeastern Arizona that is 
now quite barren, but a number of years of protection would be 
necessary to produce this result. This grass association now fur- 
nishes the most of the available forage over approximately seven 
sections of the reserve, an area on which it was very unimportant i1 
years ago. 
THE CROWFOOT-GRAMA ASSOCIATION. 
The crowfoot-grama association is the most important association 
now occupying any part of the area studied, mainly because it occu- 
pies more than half of it (No. 3 in fig. 3). It now covers about 31 
of the 58 sections under fence and is still slowly extending its borders 
west and north. It is also important as furnishing an amount of 
forage that is about an average of the production of all the different 
forage-producing belts or zones of the region. It thus becomes an 
approximate measuring rod for the estimation of carrying capacity 
fer the region. 
The association consists mainly of grasses, of which crowfoot 
grama (Louteloua rothrock) is the most conspicuous and certainly 
the most abundant, though by no means the only one (PI. II], fig. 1). 
At all levels except the very lowest may be found more or less of 
Bouteloua filiformis, which is also an important component of the 
needle-grass association; and three of the needle grasses (Aristida 
divaricata, A. scabra, and A. californica) also occur in greater or 
less abundance in this association. Along the upper side of the 
1 See Bureau of Plant Industry Bulletin 67, p. 26, plats A and B; p. 28, plats A’, B’, 
and C’, 
