SOIL AND CLIMATE. 



41 



rich soil, well supplied by irrigation water or water rising from 

 below as is often the case where date palms are grown, a 

 comparison of the heat factors is considered of importance. 

 This factor has therefore been considered. It should be noted, 

 however, that a weak point in comparisons made on those lines is 

 that no indication is given of the height of the temperature at 

 different stages of the plant's life cycle. In date culture, for 

 example, high temperatures are much more essential at the fruit 

 ripening period than early in the fruiting season, and where 

 such comparisons are being made it should also be seen that 

 there is no considerable discrepancy in this respect. 



The amount of heat necessary to ripen the fruits of the 

 date palm has generally been calculated by adding together 

 the daily mean temperatures during the months when the dates 

 are developing, the developing period being considered as extend- 

 ing from 1st May to Slsfc October. Following W. T. Swingle of 

 the United States of America, Department of Agriculture, I have, 

 for convenience, added only the degrees of temperature above 

 64'4F. The Deglet Noor date referred to below is supposed to 

 be the finest date known, and the most difficult date to ripen. 



TABLE XI. 



Data from Swingle, United States of America, Department of Agriculture, Bulletin No. 53, 

 except thot-c marked * which are from " Climate of the Continent of Africa," by A. Knox. 



