12 BULLETIN 367^ U. S. DEPARTMENT OF AGEICULTUEE. 



elder 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 net intended to imply by what has been said that the black 

 grama is the dominant plant of the area here called by its name. 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 vi'riter has not seen the abun- 

 dance of Atrlplex elegans mentioned hy Griffiths^ in the region, 

 ner some of the other species referred to, but the amount of grass in 

 that region has increased considerabh". 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 en much of southeastern Arizona that is 

 now quite barren, but a number of ^''ears 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 11 

 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 

 for the region. 



The association consists mainly of grasses, .of which crowfoot 

 grama {Bouteloua rofhrockii) is the most conspicuous and certainly 

 the most abundant, though b}^ no means the only one (PI. Ill, fig. 1). 

 At all levels except the very lowest may be found more or less of 

 Bouteloua fHiformis, which is also an important component of the 

 needle-grass association; and three of the needle grasses {Aristlda 

 divaricata, A. scahra, and A. calif arnica) 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. 20, plats A and B ; p. 28, plats A', B', 

 and C. 



