128 



DUDLEY MEMORIAL VOLUME 



Atriplex canescens 

 Atriplex poly car pa 

 Atriplex nuttallii 



ELECTRIC RESISTANCE 



70.0 ohms 

 29 . ohms 

 16.5 ohms 



FREEZING POINT 



-0.2 C. 

 -0.3 C. 

 -0.4 C. 



SOME INFERENCES AND CONCLUSIONS, AND SUMMARY. 



The most important findings of the present study, together with sugges- 

 tions as to their possible significance, may be briefly presented. 



Chemical analyses of three species of halophytes, which occur naturally 

 in a certain salt-spot, or area, where there is a large amount of "white alkali," 

 near Tucson, show, among other features, that the amount of salts, as well 

 as the kind, is unlike and is characteristic for the species. It is found also 

 that certain elements, especially sodium and calcium, are present in unlike 

 amounts in the ash of these plants. The relation of sodium and calcium in 

 the salt plants, and in mesophytes, based on data already presented, is given 

 in the following table: 



Table 6. 



Calcium and sodium in plants, in per cent, with the 

 Ca 



ratio 



Na" 



Electric resistance tests were carried out on the same species of halo- 

 phytes as were subjected to analysis. These showed in general that the re- 

 sistances were characteristic for any given species. Atriplex canescens had 

 the highest and A. nuttallii had the lowest resistance. 



Physical and chemical studies of the alkali soil were also made. Sodium 

 salts were found especially abundant and calcium salts were present as a trace 

 only. The salts were found to be most abundant at the center of the salt- 

 spot and to become less gradually as the periphery of the spot was ap- 

 proached. 



Combining the observations on both plants and soil we find, therefore, 

 that the center of the salt-spot, where the soil solution is most dense and 



