138 The Plant World, 



below the range at this season is usually 40°-50°, and it there- 

 fore appears that the west side stands intermediate. The same 

 difference was reflected in the spring water, which latter may 

 be taken as slightly indicative of soil temperatures. That on 

 the west showed a distinct daily fluctuation of one or two de- 

 grees, while in the slightly colder water on the east, no such 

 change was measurable or even discernible. Nor did it show 

 any tendency toward seasonal change, for it remained constant 

 at 53° F. from August to the end of October. But while the east 

 side shows highly equable and temperate conditions, and while 

 the data may be slightly influenced by some degree of lateral 

 protection of their stations, the opposite side does not show any 

 such extremes as would seem decidedly harmful to the plant life 

 of these mountains. 



Neither can the contrast be explained on the ground of 

 rainfall. The total precipitation at the western station for the 

 rainy season beginning July 3rd and ending September 6th, 1909, 

 was 15.95 inches. * From, the eastern station records are avail- 

 able only from August 20th to the end of the season. For this 

 period the rainfall was 2.80 inches (7 cm.), falling on six days, 

 as against 4.75 inches (12 cm.) falling on 10 days at the western 

 station. While the comparative data are too meagre for draw- 

 ing conclusions, the figures, together with general weather ob- 

 servations made at the same time, point to a rainfall that is 

 actually less on the east side. If this proves true, it will furnish 

 an interesting local contradiction to Schimper's fundamental 

 law of causal relationship between rainfall and vegetation, so 

 strikingly shown in the Cascades and the Sierra Nevada. 



A very marked difference appeared in the run-off. The 

 east slope, being steeper, might be thought conducive to greater 

 run-off. In fact, however, the heaviest showers produced no 

 run-off whatever, except on trails, and not even a perceptible 

 rise in the springs at Miller's Cabin occurred. Any rivulet gath- 

 ering on a trail would be absorbed by the ground cover, usually 

 before descending ten or twenty feet. Even where gullies were 

 present, the pine needles and other material in their bottoms 

 were not washed aside. The west side just after heavy showers 

 presented quite different evidence to both eye and ear. The 



♦Recorded by Messrs. Fenner and Gunter, and Miss O'Connell, from a gauge furnished by 

 Professor Smith, of the Arizona Experiment Station. 



