GRAZING RANGES IN SOUTHERN ARIZONA. lig 
Griffiths! and Thornber?. Certain characteristics of this grass need 
further emphasis, however, since by virtue of them it offers possi- 
_ pilities not shown by many other grasses of the region. It endures 
great extremes of temperature and dryness; it grows upon some of 
the poorest and driest of the gravelly mesa soils; it occurs at alti- 
tudes ranging from about 2,000 to over 4,000 feet ; it is excellent feed ; 
its stems are perennial and die back but a short way at the tip each 
winter, thus furnishing feed at any time in the year. These are its 
good points. It must be remembered that its growth is very slow, 
dependent entirely upon the water supply of a very dry region; 
that its seeding habits are poor, and that conditions for germination 
are poor even when viable seeds are produced; that it is easy to over- 
estimate the carrying capacity of a previously unstocked range of this 
kind of grass, because the growth present is that of several seasons. 
These are the bad points. This grass usually occurs under the 
bushes and may be found sparsely scattered over all the mesa country 
in such protection. It certainly will not bear any degree of over- 
stocking, but it is at least doubtful if students of grazing conditions 
(the writer included) are warranted in treating this grass as not 
worthy of much consideration, as has been very largely their habit 
hitherto. 7 
The way that this grass (probably the best feed of its distribution 
area) has managed to persist in a region which has been thoroughly 
denuded of everything in the way of stock feed isof itself noteworthy. 
And observations in the reserve have demonstrated clearly that under 
protection from animals it 1s capable of dominating areas where it 
was thought to be almost a negligible factor. When the fence was 
first built 1t was hard to find any large plants of this species,? and 
they were always under bushes. After 11 years of protection it is 
fairly common all over the reserve below the 3,800-foot contour, 
and, while the old plants are more apt to occur in the bushes, their 
presence there is not universal nor due to the necessity of shade or 
protection, but probably because such situations are more favorable 
for the germination of the seeds. Within the past four years, since 
seed plants have become tolerably numerous, the species has spread 
quite rapidly in the northwestern quarter of the reserve and has put 
a considerable crop of good feed on an area that previously pro- 
duced a very small crop of poor feed. And there is lttle doubt that 
under protection this plant will come to gominate much of the re- 
serve, especially that part of it where the other perennial grasses 
grow but poorly. The spread and development of this plant under 
protection is strongly corroborative of the claims made for it by the 
1See Bureau of Plant Industry Bulletin 177, p. 17. 
2 See Arizona Experiment Station Bulletin 65, p. 279. 
3 See Bureau of Plant Industry Bulletin 177, Pl. IV, fig. 1. 
