1914] _ VINSON—DATE PALMS 327 
several ranges of very low mountains, but the Djerid is exposed to 
the Sahara on the south. The result is that while the day tempera- 
tures at Gafsa are only 6 or Ae F. cooler than at Tozeur, the night 
temperatures vary by 300r35° F. Thus, high minimum temperature 
seems to be a more important factor in determining the maturation 
of the fruit than high maximum temperature. This observation is 
in perfect harmony with the curves for rate of growth obtained 
at Tempe, Arizona. 
ARIZONA AGRICULTURAL EXPERIMENT STATION 
Tucson, ARIZONA 
