112 



THE DATE PALM. 



Sample D is the most interesting, as it shows the ability of the roots 

 of the fan palm to grow in enormously alkaline soil. 



A recalculation of sample D in comparison with the surface soil of 

 Station No. 1 at Chegga, Algeria, the only sample obtained in the 

 Sahara with so high an alkaline content, is given herewith. 



TABLE 42. Per cent of alkali in soil at Palm Canyon, California, and at Chegga, Algeria. 



No subsoil in the Sahara or from the Salton Basin as yet reported 

 is so alkaline as the subsoil from Palm Canyon. There are no roots 

 very near the surface,, where the amount of alkali is greatest, at 

 Chegga (or at the other Saharan stations), whereas the layer in ques- 

 tion in Palm Canyon is full of roots. Prof. R. H. Forbes a has called 

 attention to the occurrence of roots of the date palm at 6 feet in depth 

 in "very alkaline subsoil" in the Salt River Valley, Arizona, where 

 they were forcing their way into the calichi hardpan. The date palm 

 doubtless can stand as much alkali as the fan palm, and it is probable 

 that it would grow where the fan palm is now found wild. 



The summer heat will doubtless be less than in the lower parts of 

 the Salton Basin, for these fan palms occur some 500 feet or more 

 above sea level. The winters are, on the other hand, warmer at such 

 altitudes, if there is a good drainage of cold air to lower levels (see 

 p. 61). 



CHEMICAL COMPOSITION OP THE ALKALI OP THE SALTON BASIN. 



An analysis of a mixture of eight surface crusts was reported in 1901 

 by Means and Holmes, which analysis is given below alongside that 

 of six surface crusts obtained in 1900 in the Algerian Sahara. 



TABLE 43. Percentage composition of alkali in surface crusts from the Algerian Sahara 

 and from the Salton Basin, California. 



a Arizona Experiment Station, llth Annual Report, p. 156. 

 b Wanting in some of the soils analyzed. 



