80 



THE DATE PALM. 



It is difficult to say how much of the beneficial effect observed in Fougala from 

 surface irrigation is due to the better aeration of the subsoil thereby brought about. 

 There can, however, be little doubt that the date palm is distinctly favored by a 

 proper aeration of the soil in which it grows, since the palms at Fougala when irri- 

 gated from the shallow wells did better than those nearby which have their roots in 

 contact with the very same layer of water which fills these wells. Of course the 

 identity of the water supply in the case in question does not exclude the probability 

 of the alkali being washed out from the surface soil by abundant irrigation, even if 

 the water used is rather brackish. Unfortunately no tests were made of the water 

 in these surface wells, but it is undoubtedly much more alkaline than the water of the 

 deep artesian wells. Other observations made at Ourlana in the Oued Eirh region 

 went far to show that proper aeration of the subsoil is even more important than 

 absence of alkali for the proper growth and fruiting of the date palm. For instance, 

 the extremely brackish water which, flows from the drainage ditches is nevertheless 

 used in some instances to irrigate palms planted at lower levels and without apparent 

 injury, although such palms do not show a rapid growth (see p. 98). 



Station No. 1 at Fougala represents the undisturbed desert conditions (PI. XV, 

 fig. 1). It was situated where no culture, drainage, or irrigation had been practiced, 

 or at least not in modern times/' The samples were taken a short distance to the 

 northeast of the ruins of an old Roman fort. The natural vegetation consisted of 

 a scanty growth of saltbushes, samphires, and other plants able to stand much alkali. 

 A date palm, yellow and evidently not in a thriving condition, was growing near by. 



The amount of alkali present in the surface crust and at various depths is shown 

 in the following table: 



TABLE 14. Per cent of alkali in undisturbed Saharan soil at Station No. 1, Fougala, 



Algeria. 1 



1 Mr. Seidell's original analyses of the samples from this station are as follows: 



Similar conditions near this station are shown in Yearbook, 1900, PL LXI, fig. 4, 

 in the background. 



