THE VOICE OF THE DESERT ] 5^ 



the coarser detritus from the mountains. But when a rain 

 falls on this porous ground, it soaks in, providing abundant 

 v^ater for at least a fev^ hours, or long enough for it to be 

 snatched by shallow, wide-spreading roots. Certain birds, 

 including especially the beautiful gilded flicker, like it bet- 

 ter than the creosote flats and so does the Harris ground 

 squirrel who looks rather like a chipmunk with an unusu- 

 ally fluffy tail and who puts in a frequent appearance. 

 Within a mile or two after the first saguaro one is defi- 

 nitely mounting the talus slope and one is definitely in the 

 midst of what is called the succulent desert. 



Soon the road is climbing steeply, the ancient walls of 

 the not-yet-eroded mountain on one side, on the other a 

 sheer drop of several hundred feet into the canyon cut by 

 a stream which may now be dry but whose bed is followed 

 by a serpentine line of cottonwoods, perhaps even of wil- 

 lows. Toward the upper limit of this zone ocotillos, which 

 wave in spring their blood-red flowers, begin to appear. 

 Then, somewhere about forty-five hundred feet, again on 

 a line as sharp as that of the tree limit in colder climes, 

 the saguaros stop. 



Through at least the lower portions of the zone we have 

 just passed, frost is less common than on the valley floor 

 because the cold air from the heights flows off and collects 

 in the valley below. Now, however, the influence of alti- 

 tude begins to overweigh that of slope and the air grows 

 cooler. The characteristic tree is now the evergreen oak, of 

 which there is a bewildering number of species. Yuccas and 

 agaves, or century plants, have taken over as the most 

 conspicuous of smaller perennials. The Harris ground 

 squirrel is seen no more. In his place is the rich brown 

 cliff chipmunk — a very good "indicator" animal because he 



