FUNCTION IN PLANT LIFE 39 



Had the experiment been carried out in a frame, so that 

 the soil could have received its charge from the negative 

 earth instead of from the positive air, the results obtained 

 would not have been so conclusive, as percolation of 

 moisture from below could not have been guarded against. 

 As it was, one could reasonably infer that the small per- 

 centage of conductive mineral in the soil of No. 2 acted, 

 in conjunction with the water, as an electrolyte, and so 

 relieved the latter of part of its duties. I say in conjunc- 

 tion with the water, because without moisture there can be 

 no conductive or inductive capacity in soil or in plant life. 



It would be interesting to learn whether in countries 

 subject to drought comparison has been made, under 

 similar climatic conditions, between districts where the 

 soil is and is not ferruginous. In Egypt the sand generally 

 contains some mineral salts, and a minimum of irrigation is, 

 more often than not, generously responded to. The 

 question is one of some importance, more especially in 

 relation to the Indian famine problem : the rice plant 

 requiring an excessive amount of water for its successful 

 cultivation. 



THE EFFECT OF ELECTRICAL STIMULATION UPON GROWTH. 



In A Text-book of Biology, by J. R. Ainsworth Davis, 

 B.A., it is said : " Electricity probably plays an im- 

 portant part in growth, as electric currents taking various 

 courses have been demonstrated in living plants. Currents 

 artificially sent through a root have been found to retard its 

 growth." 



The sentence in italics, taken without qualification, is 

 I think, incorrect. It depends, in my judgment, upon the 

 sign of current and the electromotive force employed. 

 A current of positive sign applied to the root of a plant 

 growing in the earth might exert a retarding influence, and, 

 similarly, one of negative sign to the soil of a pot plant. 



