ELECTRIC RESISTANCE OF PLANTS. I3 



Canescens zone. 

 Atriplex Canescens 65 ohms. 

 Bigelovia Hartwegii 1 1 5 ohms. 

 Prosopis veliitina 650 ohms. 



Poly car pa zone. 

 Atriplex polycarpa 35 ohms. 

 Suaeda sufrutescens 25 ohms. 

 Bigelovia Hartwegii"^ 1 10 ohms. 

 Prosposis veluntia* 70 ohms. 

 Lyciiim Andersonii (?) 67 ohms. 



Ntittallii zone. 

 Atriplex Nuttallii 25 ohms. 

 Suaeda siiffrutescens 42 ohms. 

 Prosopis velutina 280 ohms. 



The averages of five series of tests made during the 

 summer of 1905 are as follows: A. canescens, 41 ohms; A. 

 polycarpa, 23.9 ohms; A. Nuttallii, 18.2 ohms. As gener- 

 ally speaking the electric resistance is inversely as the salt 

 content A. canescens would from these tests have least salts 

 (electrolytes) and A. Nuttallii would be richest in salts, 

 while A. polycarpa would hold an intermediate position in 

 this regard. In other words the variation of salts in the soil 

 finds its counterpart in the variation of salts in salt plants 

 typical of the soil. The results thus derived by the use of 

 the bridge was apparently substantiated by the results of 

 analytic work of Prof. Gies who found the total soluble 

 matter in the ash of the three species to be as follows : A. 

 canescens, 62.27 per cent.; A. polycarpa, 66.99 P^^ cent.; A. 

 Nuttallii, 79.20 per cent. 



Unsuccessful attempts were made to express plant juices 

 in suflScient quantities for the electric resistance tests so that 

 dilution would not be necessary. Could this have been done 

 and could the juices also have been frozen, the relative resist- 

 ances taken together with the freezing points would have 



* * Bigelovia and Prosopis were growing along one of the washes that 

 traverse the salt spot. 



