NOTES ON THE PHYTOGEOGRAPHY OF THE ARIZONA 



DESERT 



J. C. BLUMER 



Saskatoon, Saskatchewan 



In the winter of 1911 the writer made a trip, through the kind- 

 ness of Mr. S. G. McWade, of the Cababi Mining Company, into 

 the Cababi, Comobabi, and Quijotoa mountains and the surround- 

 ing country, including the Qui-i-to-woc hills. This region is sit- 

 uated from 75 to 100 miles west of Tucson, and lies in the heart 

 of one of the most unique and remarkable floral empires of the 

 earth, the Lower Sonoran region of southern Arizona. It is about 

 these rocky desert ranges and immensely broad plains, or valleys, 

 that some of the greatest extremes of heat and drought obtain 

 that are known within the boundaries of our country. However, 

 during February, the month in which the trip was made, the 

 weather was cool, clear and windy. Three or four cloudy days 

 culminated in a light rain on February 12, and in a succession of 

 flurries of frozen rain on the 16th, resulting in a hoar frost the next 

 morning, with the thermometer at 28°F. It is almost needless to 

 state that none of the desert vegetation appeared to take the slight- 

 est harm from this moderate extreme. At the same time at Tucson 

 a protracted rainy period and rather low temperatures prevailed, 

 showing that climatic extremes may vary greatly between places 

 of equal elevation and less than 100 miles apart. If this difference 

 is typical it indicates that the gentle protracted rains of winter 

 and also the copious summer showers center about the high moun- 

 tains near Tucson and eastward, leaving a rapidly diminishing 

 rainfall to the Westward. On a side trip to the Qui-i-to-woc hills 

 on the 16th even such a desert range as the Baboquivari was seen 

 on the eastern horizon wrapped in a mantle of snow. 



Chief among the constituents of the desert forest — for a forest 

 it is, although more strictly known to phytogeographers as bush- 



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