1912.] PUBLIC DOCUMENT — No. 31. 175 



thej were placed in hot water, although trees and various potted 

 plants with an intact root system all showed the iniiuence of 

 temperature on resistance. 



Conclusions. 



1. The electrical resistance of trees shows a close relationship 

 to temperature, their higher resistance corresponding with the 

 low temperature, and the low resistance corresponding with the 

 higher temperature. 



2. The electrical resistance of trees is lower during warm 

 than cold days, and less during warm than cold seasons. It is 

 usually less during afternoons than mornings; in other words, 

 it corresponds to changes in the temperature. 



3. The average electrical resistance of trees is highest on the 

 north side, followed by the west, south and east sides respec- 

 tively. 



4. The temperature of trees given by our experiments, which 

 were of limited duration, is less on the north side, followed by 

 the west, east and south sides, and coincides in a general way 

 with the variation in the resistance of the different sides of the 

 tree. Extensive observations regarding temperature and resist- 

 ance would undoubtedly show very close relationship between 

 these two factors. 



5. The average electrical resistance for the east side of the 

 tree is about 8 per cent, lower than the west side,, due, undoubt- 

 edly, to differences in temperature existing between the east 

 and west exposures. The difference, however, in the light in- 

 tensity of morning and afternoon is variable from day to day 

 and from year to year, and may range from 1 or 2 per cent, to 

 30 per cent, or more per month, but averages between 10 per 

 cent, and 17 per cent, per annum. 



6. The difference in the average electrical resistance of the 

 north and south sides of the tree is about 5 per cent., the average 

 difference in the temperature being about the same. 



7. The cambium layer offers the least electrical resistance, 

 as shown by lightning discharges and by our experiments. This 

 is followed by the phloem and sapwood. 



8. Small plants and branches of trees in general give higher 

 electrical resistances than trees, probably due to the greater 



