SALT PLANTS AND SALT-SPOTS CANNON 



127 



treated in a similar manner. As a control, a portion of air-dry material, 

 which had been boiled, was left one-half hour in cool water, after which the 

 solution was expressed as usual. The method usually followed was to bring 

 the plant to the laboratory and allow it to become air-dry. A 10% solution 

 was then prepared, which was boiled five minutes. The fluid was expressed 

 and allowed to cool. 



Very many tests were made mainly on the salt plants named, and also 

 on other non-salt forms. The results were so consistent that it will not be 

 necessary to give more than a single representative experiment. 



Table 5. Electric resistance of plant solutions. 

 Canescens Zone. 



Nuttallii Zone. 



Atriplex nuttallii 

 Sumda suffrutescens 

 Prosopis velutina ® 



The averages of five resistance tests of solutions of salt plants, made at 

 various times during the summer, are as follows: Atriplex canescens, 41 

 ohms; Atriplex polycarpa, 23.9 ohms; Atriplex nuttallii, 18.2 ohms^. 



8 These plants were situated in some of the small washes which traversed the 

 salt-spot. 



'' A verification of the relative results obtained by the use of the bridge was 

 obtained by freezing plant solutions previously tested electrically. The following 

 were some of the results: 



