1905.] PUBLIC DOCUMENT — No. 33. 15 



of further experiments along similar lines, and present some 

 results relating to differences of electrical potential which 

 exist between locations in trees and corresponding situations 

 more or less removed from them. 



In the first scries of experiments we will consider the 

 influence of electrical potential upon growth. In subjecting 

 plants to an atmospheric charge of a certain potential we used 

 a glass case such as is described in our preceding report, 

 being, briefly, a glass case 3 feet 4 inches long, 2 feet 9 

 inches wide and 2 feet 11 inches high, with shellacked wooden 

 frames and bottom. Another case, for comparison, and 

 similar in structure but slightly larger, was also employed. 

 Both cases were tolerably tight when closed, and were placed 

 on movable trucks, from which they were well insulated, in a 

 larixe oTcenhouse. The jyreenhouse screened out, as it were, 

 the atmospheric electricity. At no time have we ever been 

 able to detect any electrical potential in the air in green- 

 houses. The soil used in growing the plants was of uniform 

 type, very carefully mixed ; in fact, every precaution was 

 taken to have the soil conditions the same in each case, and 

 all its various constituents were thoroughly incorporated. 



In the case which was to be treated was placed a small 

 water-dripping apparatus, which served as a collector, and 

 which indicated the degree of charging. The air Avas charged 

 by means of a wire projecting into the case from a Topler- 

 Holtz influence machine. All electrical readino;s were meas- 

 urcd by a Thompson quadrant electrometer. 



In the two experiments now described radish plants were 

 employed, as they seemed to be most suitable for the con- 

 dition under which they were grown. The seeds were of a 

 uniform grade, and were sown in rows 3 inches apart and 1 

 inch apart in the rows. It was the intention to charge the 

 case each morning to a potential of 150 volts ; but this was 

 impossible, as exactly 150 volts could not always be obtained, 

 and at times, on account of the dampness of the air, no charge 

 could be procured from the machine. The doors of both 

 cases were kept closed for four hours after the charge had 

 been induced into the treated case, and at the end of that 

 time they were opened ; th(>refore, for twenty out of every 



