HEAT REQUIRED TO MATURE FRUIT. 69 



Noor may after all ripen in the Salt River Valley. By this method of 

 calculating, as well as by the summation of the mean temperatures, 

 Salton heads the list, being- the hottest desert station known. a There 

 can be no question that the Deglet Noor and other choice late sorts 

 will mature here and in the other parts of the Salton Basin. 



The advantages of excessively hot summer climates for date culture 

 are demonstrated in the Souf country in the Sahara, a region covered 

 with large dunes, sometimes 500 feet high, of wind-blown sand (PI. II, 

 p. TO), lying about 50 miles east of the Oued Rirh and probably having 

 about the same summer climate as Ayata and Tougourt. The best 

 Deglet Noor dates are said to come from the Souf and are grown in 

 peculiar sunken gardens excavated to a depth of from 25 to 30 or even 

 50 feet. These sunken gardens, called "Ghitan" or "Rhitan" (see 

 tig. s), are dug down to within a few feet of the level of the ground water 



*-* 



FIG. 8. Sunken date gardens in the sand dunes in the Oued Souf region, near El Souf, Algeria. 



and are large enough to contain from to 100 palms, usually from 25 

 to 50. The sides are sloping, and composed of sand which reflects the 

 sun's heat and light on the leaves from the sides and from below, thus 

 intensifying the heat to such a degree that even the Arabs can not 

 work in these gardens during the hottest weather.* In these torrid 

 gardens the space is so valuable that the palms are not allowed to pro- 



See footnote, p. 66. 



&No irrigation is necessary for the date palm in these gardens, as the roota reach 

 the moist sand near the water level. The chief labor is the carrying out of the sand 

 blown in by the wind. When the hot simoon winds of summer blow, the natives 

 do not attempt to work during the day but commence after midnight when the 

 temperature is lowest. So difficult is the struggle against the sand blown into the 

 gardens by every high wind that their labor has been likened to that of ants rather 

 than that of men. 



