26 



DATE VARIETIES AND DATE CULTURE IN TUNIS. 



as if the sum of the daily means, which in 1904 was more than 150 

 degrees higher than the normal, were a more satisfactory basis for 

 comparing one season with another at the same locality than the 

 sum of the daily maxima, which was about 200 degrees lower than 

 the normal. Furthermore, in 1905, when the ripening of the dates 

 was late and imperfect, the sum of the daily means was nearly nor- 

 mal, while that of the daily maxima was again nearly 200 degrees 

 lower than the normal. In 1903, w T hen the crop was much smaller 

 than in 1904, the sum of the daily maxima was only 25 degrees lower 

 than the normal, while the sum of the daily means was nearly 250 

 degrees below the normal. Still more conclusive are the data for 

 1902, a year when the crop was unusually large. The sum of the 

 daily maxima of that season was only 100 degrees higher, while that 

 of the daily means was 350 degrees higher than the normal. 



TABLE 5. Mean maximum and minimum temperatures at Tozer during the 

 months of May to October, 1904 and 1905. 



Comparing further the good year 1904 with the poor year 1905 at 

 Tozer, we find that while the mean maximum was much higher in 

 June and slightly higher in July in the latter year, the August and 

 October maxima were considerably higher in 1904, while those for 

 May and September differed little in the two years. The mean 

 minima during the first four months of the season were considerably 

 higher in 1904 than in 1905. 



ATMOSPHERIC HUMIDITY. 



The amount of moisture in the air is an important factor in date 

 culture. At Gabes, in Tunis, one of the few localities in the world 

 where the date palm is extensively grown on the seacoast, the qual- 

 ity of the fruit is often seriously impaired by this cause (see p. 19). 

 In the following table the mean relative humidity for each of the 

 four seasons and for the year is given for several localities in North 

 Africa, where date culture exists, and for localities in the south- 

 western United States, where it can probably be successfully intro- 

 duced. 



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