154 EXPERIMENT STATION. [Jan. 



The resistances given on the south side of the same maple 

 tree as in Table V. are given here ; in this case, however, the 

 electrodes were attached differently, being driven through the 

 bark into the wood, and none of the tissue around them was cut 

 away. 



The resistances given here run considerably lower than those 

 shown in Table V. for the same tree for the same period, due 

 to the fact that the electrodes were inserted differently into the 

 tree. If we compare the average resistances obtained from the 

 two experiments, those in Table VIII. and those in Table V., we 

 obtain the following for the same period, with the same tree. 

 The average resistances on the south side of the tree shown in 

 Table V. are as follows for the three different periods: 8 a.m., 

 62,130; 12 m., 44,610; 4 p.m., 39,580, while those given in 

 Table VIII. are 29,610, 20,462 and 18,318 ohms. 



The higher resistance shown in Table V. represents not only 

 that of the cambium, but of some of the wood as well. 



The highest resistance readings were obtained at 8 A.:\r., while 

 the lowest were obtained at 4 p.im. The midday temperatures 

 were highest, as might be expected, with little difference in the 

 morning and afternoon. 



The after effects of the higher temperatures influenced the 

 resistances taken at 4 p.m., since the tree, being generally ex- 

 posed to the sun's rays for a considerable period in the day, 

 would become warmer, and the heat would be retained for some 

 time. It was thought desirable to make one experiment when 

 the observations could be recorded hourly. The results of these 

 observations are shown in Table IX. 



