ANALYSES OF SAHABAN SOILS. 



97 



PREVIOUS AND SUBSEQUENT ANALYSES OP ALKALINE SOILS FROM THE SAHARA. 



Two analyses of soil from the vicinity of Ourlana are reported by Holland. These 

 analyses were not complete, for all the more soluble constituents are lumped as salt, 

 which is here synonymous with alkali. The vegetable soil of a new garden (see analy- 

 sis No. 23, in Table 34) at Tala em Mouidi, very near Ourlana (Saharan formation) , 

 showed 6.8 per cent of alkali. Another soil (No. 24, Table 34) was from Mazer, 

 about a mile northeast of Ourlana. Here the sample was of washed soil of a salt flat 

 not yet under culture; it contained 3.4 per cent of alkali. The same work reports 7 

 per cent of alkali in the vegetable soil (No. 21, Table 34) of a garden at Tougourt, 20 

 miles south of Ourlana, and at Coudiat el Koda, very near Tougourt, no less than 

 29.5 per cent of the estimated weight of the soil (No. 19, Table 34) of an alkali flat 

 was composed of alkali (see analysis No. 19). The same soil (No. 20, Table 34) 

 washed for two years and put under culture contained only 0.5 per cent of alkali. 



TABLE 34. Composition (in percentage by weight) of Saharan soils, collected by Holland. 1 



1 Holland, G6ologie du Sahara, analyses by Ecole des Mines, Paris. 



2 All the readily soluble salts occurring in these samples are lumped as salt, which is here equivalent 

 to alkali. 



None of the soils analyzed for Holland was selected with any reference to date cul- 

 ture, and it is only from the samples secured by the writer and analyzed by the 

 Bureau of Soils, which have been described above, that any adequate idea can be 

 formed of the ability of the date palms to resist alkali. This power to withstand 

 alkali is one of the most striking among the life-history factors of this tree, since, in 

 this respect, it exceeds all other cultivated plants except possibly the cocoanut palm, 

 which latter is not killed by sea water containing 3.4 per cent of salts in solution. 6 



Mr. O. F. Cook informs the writer that on Cape Mesurado, in Liberia, a Phoenix, 

 perhaps P. redinata, grows on the sea beach nearer to the surf than any other upright 

 vegetation, among the stunted shrubs killed back by the salt spray. The fruit of 

 this palm, though of inferior quality, is eaten by the natives. Hybrids should be 



Holland, Georges. Geologic du Sahara. 



& Ehrenberg and Hempricht report that on the island of Farsan, in the Red Sea, 

 date palms grow directly out of the crevices in the coral rock, of which the whole 

 island is composed, and although said to be irrigated from springs it may be found 

 that the trees are subject to occasional inundation by sea water, 



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