VEGETATION OF DESERT MOUNTAINS 



301 



The low dense forest found on the main ridge and at the summit 

 of Mt. Graham, from 9600 to 10,500 feet is made up of Picea 

 ( ngelmannii and Abies arizonica. Neither of these trees is found 

 elsewhere in the isolated mountains of southern Arizona except for 

 the occurrence of a small colony of the latter on the north slopes 

 of Mt. Lemmon in the Santa Catalina range. Other woody 

 plants characteristic of the Picea-Abies forest are Salix bon- 

 plandiana, Populus tremuloides, Alnus tenuifolia, Symphoricarpus 

 oreophilus, Lonicera involucrata, V actinium scoparium and Rubus 

 parviflorus. 



RAINFALL 



In the summer of 1917 the writer attempted to secure a series 

 of rainfall readings at 1000-foot intervals on the southwest face 

 of the Pinaleno Mountains, for comparison with a similar series 



TABLE 1 

 Rainfall for the summer of 1917 in inches 



Tucson (2400 feet) . . 

 Thatcher (2800 feet) 



3000 feet 



4000 feet 



Willcox (4190 feet) . . 

 Bonita (4916 feet)... 



5000 feet 



0000 feet: 



7000 feet 



8000 feet 



9000 feet 



SANTA CATALINAS, 

 JUNE 30 TO SEP- 

 TEMBER 30 



6.26 



6.1 

 8.0 



7.1 



9.2 



14.0 



15.0 



17.3 



PINAiENOS, JUNE 

 23 TO SEPTEMBER 23 



2.62 



6.07 

 5.73 



12.0 

 15.5 

 13.6 

 12.1 



in the Santa Catalinas. Five metal cans were installed from 

 6000 to 10,000 feet inclusive, with 8 liters capacity and 10 cc. 

 of kerosene to prevent evaporation. The gauges were installed 

 and read on both mountains at such time as to secure the summer 

 rainfall alone (July, August, September). The gauge at 10,000 

 feet was overturned during the summer and the record lost. 

 The readings for the other stations on the two mountains, 

 together with those for the Weather Bureau stations at adjacent 

 towns are shown in table 1. 





1*4 • 4 



