8 BULLETIN" 271, U. S. DEPARTMENT OF AGRICULTURE. 



Table 9 [Sujingle]. — Sum of daily mean temperatures above 18° C. (64.4° F.) for fruit- 

 ing period of date palm from May 1 to October 31, at the stations named. 



Locality. 



Sum of daily mean 

 temDeratures above 

 18° C. (64.4T.Mrom 

 May 1 to Oct. 31. 



Remarks. 





Degrees 

 centigrade. 



Degrees 

 Fahrenheit. 







652 



788 



1,054 



1,409 



1,593 

 1,677 



1,836 



1,816 



1,906 



2,091 

 2,049 



2,356 



2,237 



2,348 

 2,585 



2,074 



2,679 

 3,392 

 2,749 

 2,106 



1,174 

 1,418 

 1,897 



2,538 



2,868 

 3,019 



3,304 



3,269 



3, 431 



3,764 

 3,689 



4,242 



4,027 

 4,227 

 4,652 



3,734 



4,823 

 6,106 

 4,948 

 3,791 







Very early sorts mature. 







sorts grown usually fail to ripen. 



Average of 6 years' observations. Dates of the 

 sorts now grown usually fail to ripen. 



Dates ripen regularly. 



Average of many years' observations. Many 

 sorts of dates ripen regularly. 



Average of 10 years' observations. Many sorts 

 of dates ripen regularly; date culture the lead- 

 ing industry. Deglet Noor dates ripen but 

 are not of the best quality. 



Deglet Noor dates ripened very imperfectly. 



Deglet Noor dates ripened very slowly and im- 

 perfectly. 

 Derlet Noor dates ripened well. 

 Do. 



Average of 5 years' observations. Many excel- 

 lent varieties ripen. 

 Average of several years' observations. 





Phoenix, Ariz. (Salt River 



Valley). 

 Biskra, Algeria (Northern 



Sahara). 



Ayata, Algeria, 1890 (Oued 



Rirh region), Sahara. 

 Ayata, 1891 



Ayata, 1889 



Tougourt, Algeria (Oued 



Rirh region). 

 Bagdad , Mesopotamia 



Indio, Cal. (Salton Basin) 



Indio, 1903 



Mammoth Tank, Cal. (Salton 



Basin). 

 Salton, Cal., 1903 (Salton 



Basin). 



Average of 23 years' observations. 



The coolest summer recorded. Observations 

 taken for the first time with standard Weather 

 Bureau thermometers in the regulation shel- 

 ters. 



Salton, 1897 





Salton 1902 :.. 





Imperial, Cal., 1902 (Salton 

 Basin). 





In those calculations 64.4° F. is assumed as the zero point of 

 activity of the date tree as far as flowering and fruiting functions 

 are concerned, any number of degrees of daily mean temperature 

 above that point being available to the tree in forwarding its fruiting 

 functions, though growth of leaves and stem may go on at tempera- 

 tures considerably lower. 



By multiplying the number of degrees above 64.4 in any monthly 

 mean by the number of days of that month the number of available 

 heat units (1 degree 1 day) is arrived at. The summations for the 

 months of May to October, inclusive, in column 5 of Table I have 

 been arranged for comparison with those of the table quoted from 

 Swingle. 



The summations of 2,049 heat units for Alexandria and 2,179 units 

 for Gizeh must be fairly representative of the conditions under which 

 the greater number of the date trees of the five varieties mentioned 

 make their growth. (PL II.) By comparison with table 9 of Bulletin 

 No. 53, referred to, it will be seen that localities having such low sum- 

 mations are not counted in the possible date-growing territory, except 



