196 BOTANICAL GAZETTE [September 



mountains of less elevation and Permian beds of red clay. Ten 

 miles east of the Sandia Mountains the Ortiz and San Pedro 

 mountains rise to an altitude of 8000 ft., followed by the fertile 

 prairies of the Estancia Valley. 



Climate 



The most important factor in the climate is aridity. The 

 precipitation at Albuquerque averages 7.43 in. per year; that of 

 the mountains is much greater, but unfortunately has never been 

 measured. Perhaps 20-24 in. would be a fair approximation for 

 the higher parts of the range. The distribution of the rainfall is 

 also an important factor. At Albuquerque the average for ten 

 years was as follows: 3 



Jan. Feb. March April May June July Aug. Sept. Oct. Nov. Dec. 

 0.48 0.33 0.22 0.26 0.69 0.35 1.43 1.07 1.7 0.77 0.46 0.31 



It will be noticed that there is a rainy season beginning in July 

 and one of less intensity in May. This is valuable to vegetation, 

 as the bulk of the precipitation comes during the warm season. 



It would appear from observation that a precipitation of less 

 than 0.25 in. has no effect on vegetation, with the possible excep- 



some 



Jiirsty soil to a sufficient depth to reach the roots. On the 

 r hand, much of the summer rain comes down in such a deluge 

 a goodly percentage runs off the mesa and especially its foot- 

 The distribution and the amount are both highly variable 

 and materially influence the aspect of the vegetation from year to 

 year. The May rains especially often fail altogether, and it is 

 said that during a recent drought Albuquerque received not a drop 



hills 



months 



mountains 



cally different. Judging from observation, the summer rains are 

 about 50 per cent in excess of those at Albuquerque. But while 



higher parts of the mountains 



inter 



storms 



down some distance on the mesa. This snow, slowly melting 



sMagxusson, C. Edw., Bull. Univ. N.M. no. 5. 



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