1912.] PUBLIC DOCUMENT — No. 31. 159 



Experiment F. 

 The same branch was used here as in E, except the girdling 

 was increased to 3 inches. The following readings were 

 taken : — - 



Ohms. 



1.00 P.M., 128,000 



1.30 P.M., 130,000 



2.00 P.M., 127,000 



2.30 P.M., 130,000 



3.00 P.M., 129,000 



It will be noticed that these readings were slightly higher 

 than those in Experiment E, due to girdling. 



Experiment G. 

 The same branch under the same conditions was used for this 

 experiment, except that the branch was completely girdled 

 between the electrodes. The results follow : — 



Ohms. 



8.30 A.M., 150,000 



9.00 A.M., 151,000 



9.30 A.M., 150,000 



10.00 A.M., ■ 150,000 



10.30 A.M., 149,000 



It will be noticed that the readings obtained here are higher 

 than in F or E, due to the greater girdling. These experiments 

 demonstrate that the wood gives mucli higher resistance than 

 the cambium, and shows that the resistance increased as the 

 bark and cambium were removed. The highest resistances were 

 given where there was the greatest amount of girdling. Even 

 cutting away the bark for a distance of 1/2 ^^ inch or more in 

 each direction from the electrodes greatly increases the resist- 

 ance. This is what occurred in the experiment shown in Table 

 v., where the bark was cut away from the electrodes, whereas 

 in experiments shown in Table VIII. for the same distance, and 

 where no bark was removed, the resistances were much lower. 



Experiment TJ. 

 In this experiment a freshly cut branch about 1 inch in diam- 

 eter was used, and the bark cut away for a space of 1 inch 



