406 



EFFECT OF ELECTRICITY 



[Ch. XVI 



Upon growing plants, on the other hand, numerous experi- 

 ments have been made. Nevertheless there is still a difference 

 of opinion even as to the occurrence of any effect. During the 

 middle of the last century much attention was paid to this 

 subject. Bbethelon (1783) and several others concluded 

 from extended researches that electricity favors plant growth ; 

 but their results, apparently having no practical value, were 

 largely forgotten. A century later Geandbau (79) revived 

 the idea of the beneficial effect for plants, not merely of cur- 

 rents of electricity, but also of those of the atmosphere. This 

 paper seems to have been the starting-point of the modern 

 discussion. 



The methods employed in studying the action of electricity 



Fig. 115. — The effect of atmospheric electricity upon the growth of plants. A, To- 

 hacco plant reared under normal conditions. B, Similar plant reared under a 

 wire cage, by means of which it is isolated from the action of atmospheric elec- 

 tricity. (From Grandeau, '79.) 



