56 



THE DATE PALM. 



Valley, in extreme southwestern Arizona, and especially Salton and 

 Mammoth Tank, in the Salton Basin, in southeastern California, show 

 decidedly less rainfall than occurs at Ayata, in the Oued Rirh country 

 in the Sahara, where date culture is almost the sole industry and 

 where the Deglet Noor variety is grown successfully. Even the maxi- 

 mum rainfall in exceptionally wet years in the Salton Basin does not 

 equal a the average rainfall for these critical months at Biskra. 



The number of rainy days, which is a matter of considerable import- 

 ance in determining the suitabilit}^ of climate to date culture, runs 

 closely parallel to the amount of precipitation, as may be seen by com- 

 paring the following records for Biskra and Tucson with those given 

 above for the rainfall: 



TABLE 5. Number of rainy days at desert stations (Biskra, Algeria, and Tucson, Ariz.) 

 during flowering and ripening seasons of the date palm. 



The ideal climate for the date palm would be one that was rainless 

 during the critical months. It is a matter of some interest to see how 

 often this condition has been recorded for the Salton Basin stations. 



Rainfall records are available for twelve years (1889-1900) for Salton 

 in the lowest part of the Salton Basin (263 feet below the sea level), 

 and they show that the critical months were frequently rainless; at 

 Mammoth Tank, in the eastern border of the Salton Basin (altitude 

 257 feet above sea level), the record for twenty-three years, from 1878 

 to 1900, is still more favorable, as is shown by the following table: 



TABLE 6. Number of years in which no rain (or trace only) fell at Salton and at Mam- 

 moth Tank, in the Salton Basin, California, during the months named. 



Except for one year of the twelve recorded at Salton, the rainfall in October, 1896, 

 was 0.93 inch, exceeding the average at Biskra (0.64 inch), though not being more 

 than half the maximum rainfall for the month ( 1.73 inches) at the latter station. 



