DATE VARIETIES AND DATE CULTURE IN TUNIS. 



TABLE 3. Sums of daily mean and daily maximum temperatures above 64-4 f- 

 from May 1 to October 31, at localities in the desert regions of Tunis, Algeria, 

 and the United States.** 



It would appear that for purposes of comparison of different 

 localities as to their suitability for the culture of fine varieties of 

 dates the sums of the daily maximum temperatures are more satis- 

 factory than those of the daily means. For at Biskra, Algeria, 

 where the Deglet Noor seldom ripens properly, the normal sum of the 

 daily means is higher than that given above for Nefta, and only 250 

 degrees lower than at Tozer, yet at both of these Tunis localities the 

 Deglet Noor rarely fails to mature, while the normal sums of the 

 daily maxima both at Tozer and at Nefta are considerably higher 

 than at Biskra. Furthermore, at Ayata, Algeria, in 1891, when 

 Deglet Noor dates ripened "very slowly and imperfectly," the sum 

 of the daily means was 3,431, or only 124 degrees lower than the 

 normal for Tozer as given in the table. But in favor of the sum 

 of the means rather than of the maxima is the fact that at Ayata, 

 where the Deglet Noor does not ripen well every season, the normal 

 sum of the maxima is nearly 100 degrees higher, while that of 

 the means is about 70 degrees lower than at Tozer. At Phoenix, 

 Ariz., where the Deglet Noor will probably not mature, the sums 

 of daily mean and daily maximum temperatures are several hun- 

 dred degrees lower than at Tozer. At Salton, Cal., however, both 



o The sums for Biskra and Ayata, Algeria, and for Phoenix and Salton, in the 

 United States, are those given by Swingle, Bui. 53, Bureau of Plant Industry, 

 pp. 66 and 68. As explained by Mr. Swingle, the method of observing tempera- 

 tures formerly used at Salton has probably made the sum for that point appear 

 to be higher than is actually the case. 

 92 



