18 



Overhead Electrical Discharges, [april, 



Perhaps it would be more correct to say that the assump- 

 tion is that an increase in the slight electric current passing 

 in a plant is beneficial, because it must be remembered that 

 in the ordinary way the atmosphere above a plant is usually 

 at a higher potential than the plant, and as a consequence 

 a slight current is probably leaking away to ground through 

 the vegetation, and Mr, Newman has followed Lemstrom in 

 usually having his overhead wires charged positively, and, 

 therefore, practically increasing this current to the earth but 

 not reversing its usual direction. 



That this physiological effect is produced is still a subject 

 open to controversy, and at present the most urgent need 

 in connection with this subject is further experimental 

 physiological work to decide the question. At present I 

 think it is fair to say that the practical man may get as 

 much guidance from the perusal of the results of field trials 

 given at the end of this paper as from a resume of the 

 experimental results reported by various workers, and this 

 is only another way of saying that the subject is still in the 

 experimental stage. It is sufficient to say that electric 

 currents are reported by many observers to have an optimal 

 value for the plant they are traversing, an optimum which 

 probably is variable for different plants and for the same 

 plant at different times ; and that up to this optimum, increase 

 in the strength of the currents leads to increased growth, 

 more rapid germination, increased storage of food and so 

 on, but beyond this strength the current rather inhibits vital 

 activities and tends to lower the resultant yield from the 

 plant. 



My own experiments upon the respiration of electrified 

 plants lead me to attach more importance than is usually 

 done to a possible accelerating action of the current. A 

 study of field experiments shows that often an acceleration 

 is reported, and this acceleration may have a very important 

 bearing upon the yield of the crop ; the results seem to me 

 to need analysis from this point of view. Thus, an increased 

 yield may in some cases be largely due to the fact that the 

 crop was spared bad weather owing to its more rapid 

 development, and was, therefore, harvested under better 

 conditions. 



