IRRIGA TIOX A GE. 30 1 



the fact that plants indigenous to humid regions are in most instances 

 ill suited to grow in our most arid regions, no matter how much 

 water be supplied in irrigation. 



It is imperative that dwellers in arid America give more attention 

 to the source of the seeds and plants which they undertake to grow. 

 With grains and vegetables, i. e. plants which require but a few years 

 from seed to maturity the question of the environment under which 

 the seeds planted were grown, is not so important as it is for plants 

 that survive for a greater period than a single season. With plants 

 quick to mature, the question of humidity and temperature can be 

 largely modified by season of planting. Perennials, on the other 

 hand, must continue in growth during a considerable portion of the 

 year. They must be able to withstand an exceedingly hot and dry 

 atmosphere during the summer and from five to fifteen degrees of 

 frost during the winter. They must be able to stand a daily range in 

 temperature varying from thirty to fifty degrees, not only without 

 injury to the plants but without harm to the fruit which they must 

 bear in order to be of value. 



The natural environment of the date-palm makes it well suited to 

 the more arid portions of Southwestern America. It is the most 

 characteristic and wide- spread economic tree of the Old World 

 deserts. It is indigenous to the desert and is not injured by extreme 

 heat and aridity and a moderate degree of cold, neither is it affected 

 by wide variations in the daily range in temperature. 



Although the date has rarely prospered as an economic tree when 

 taken from its home and gro.wn in similar latitudes, the explanation 

 lies in the fact that it has usually been taken from its desert environ- 

 ment and planted in humid regions. Centuries of experience has 

 demonstrated that the countries where the date does best are char- 

 acterized by intense summer heat and an almost total absence of rain. 

 However, its roots must be well watered. 



In the date regions of Northern Africa and Southwestern Asia 

 the mean annual precipitation varies in different localities from fifteen 

 inches to less than one inch. In Southern Arizona the average 

 annual precipitation for a period of eighteen years is as follows: 

 Phoenix, 7.08; Tucson, 11.63; Yurna, 3.05. 



The average precipitation for the year practically coincides in 

 the two countries and the excessive dryness of the atmosphere in 

 Northern Africa finds almost its parallel in Southern Arizona. So 

 also the temperature of the date regions of Northern Africa is very 

 similar to that of Southern Arizona. The following are a few of the 

 many comparisons that might be given. The mean maximum annual 

 temperature of El Golea, Algeria, 88 degrees F. ; Phoenix, Arizona, 

 88.1 degrees F.; Gardaia, Algeria, 83 degrees F.; Yuma, Arizona, 

 85.9 degrees F.; Laghouat, Algeria, 78 degrees F. ; Tucson, Arizona, 

 81.1 degrees F. 



