McLeod. — Effect of Electricity on Plant-grotvth. 463 



Abt. lit. — The Effect of Current Electricity on Plant- 

 growth : Further Experiments. 



By H. N. McLeod. 



Communicated by the Secretary. 



[Read before the Hatvke's Bay Philosophical Institute, 9th October, 



1893.] 



Ik the "Transactions of the New Zealand Institute" for the 

 year 1892 other previous experiments are detailed at some 

 length/'' The results which I obtained then were favourable 

 to the growth of plants being accelerated by feeble and by 

 comparatively powerful currents of electricity. For poles or 

 plates to conduct the current through soil, silver and copper 

 had been used. In one case more silver than the amount 

 contained in a threepenny piece was incorporated in three- 

 quarters of a cubic inch of soil. Plates of a substance not 

 decomposable were substituted in two experiments, and, in a 

 third, small quantities of guano were made to take the place of 

 plates. 



Experiment A. — Continuing with the same kind of plant 

 as previously, two pieces of carbon were inserted in the 

 ground fin. apart. Wires connected them with the poles 

 of a Daniell cell of the common type, which gives a pres- 

 sure of one volt. This current was sufficient to overcome 

 the resistance of tlie soil between the carbons, and circulate 

 round two seeds placed there. Moistened litmus paper proved 

 the existence of not a small current, and, on reversal of the 

 paper, change of colour was produced at the opposite end. 

 The plants were subjected to the conditions of a hothouse, 

 and the current was reversed every twelve hours. In five days 

 from the time of sprouting one electrified shoot was lin. 

 higher than either of two ordinary plants which came up at the 

 same time ; the other electrified plant, appearing later, gained 

 ^in. Comparing this result with that of experiment 5 given 

 in my last paper, we are led to conclude that the silver dis- 

 solved in the earth in the course of the experiment retarded 

 the growth. 



Experiment B. — Again, small pieces of carbon were used 

 with a one-cell current, but they were put in the earth after 

 the plants appeared above the ground, and subjected to the 

 ordinary conditions under which plants grow. At the end of 

 two weeks these electrified plants were leading by ^in. 



Experiment C. — This time thirteen small cells, each giving 



* Trans. N.Z. Inst., vol. xxv., p. 479. 



