McLeod. — Effect of Electricity on Plant-growth. 481 



other. By testing with solution of iodide of potassium and 

 litmus-paper, traces of a passing current were obtained. At 

 the end of further six weeks' time the electrified seed had 

 outgrown the other by one-half. 



Experiment No. 2 : A glass vessel was taken and filled 

 with soil. In the centre a coil of wire consisting of seven 

 spirals, four of which were stripped of insulation, was placed. 

 A current of electricity, which was interrupted at times, was 

 kept circulating, losing little or no force in the passage. Close 

 to the uncovered wires of the spiral three mustard-seeds were 

 planted so as to be in the range of the electricity induced in 

 the surrounding earth (Ferguson's "Electricity," pars. 248, 

 249) . Three other seeds were planted in the surrounding earth : 

 these seeds were as nearly alike in size as possible, and were 

 about an inch from the spiral. The glass vessel was placed 

 in the open, and so exposed to even conditions of weather. 

 At the end of seven days the seeds were separated from 

 the soil, put end to end, and measured. Those planted 

 near the coil measured ^in. longer than the ones removed 

 from it. 



Experiment No. 3 : Ten seeds of mustard were taken, and 

 planted each lin. apart in the garden, in soil mixed with 

 guano. In ten days the seeds were all above ground, some 

 ■lin., some^in. All these were exposed to the same conditions 

 of weather, and were watered equally. As time went on it 

 was noted that the plants preserved their relative size until 

 they reached maturity, save in the case of the two experi- 

 mented upon. The same was the rule with seeds planted in 

 soil mixed with bone-dust, and in ordinary loam. Two out of 

 the ten seeds were selected, each one-sixth smaller than several 

 which were noted, and equal in size to the rest. The soil in 

 which these two grew was included in the circuit of an electric 

 current which deflected the galvanometer-needle 65° when the 

 earth was not included in the circuit, and scarcely at all 

 when the earth was included. On either side of the plants, 

 in the ground, silver plates, eachi-in. by 3in., were placed, and 

 these were connected to the cell by wires. In fourteen days 

 the two mustard-plants had grown equal in size to the larger 

 plants, and in another two weeks had increased more rapidly, 

 and when they reached maturity were one-sixth larger than 

 the largest of the others. 



Experiment No. 4 : A fourteen-cell battery was connected 

 with two small plates which were put in the ground lin. 

 apart, a current of electricity was circulated round the roots 

 of two mustard-plants for the space of two weeks, but scarcely 

 any advantageous effect was noted. The anodes in the 

 ground w r ere worn, or, rather, eaten into, very little, which 

 would show that there had been little chemical action, 

 31 



