20 BULLETIN 1379, U. S. DEPARTMENT OF AGRICULTURE 



kinds of seeds, it was found that in every case the seeds grew much 

 quicker in the boxes containing the plate. Hemp seed was fully an 

 inch above the surface before controls showed any plants. The 

 observation was made also that plants in the zones nearest the plates 

 were the first to come up. Watering with dilute acetic acid was 

 found to cause quicker growth for treated plants — possibly because 

 of increased current resulting from the acid-metal reaction. Upon 

 repeating these experiments, Leicester decided that the only action 

 of the current was to stimulate the plant until the initial store of 

 food was used up. No data were recorded in cither of his reports. 



Berthelot (3) conducted some tests with soil currents to determine 

 whether electricity aided in the fixation of nitrogen by plants. Suit- 

 able control plats were provided. He reported that the treated 

 plants grew much more rapidly, being nearly twice the weight of 

 the control plants at the end of four to six weeks. Although not 

 complete or definite, the experiments were abandoned for various 

 reasons. 



Kinney (27) made an extensive series of experiments to determine 

 the influence of electrical currents on germination. Seeds were sub- 

 jected to different current strengths for different periods of time and 

 then put in suitable germination apparatus and the subsequent 

 growth noted. An intermittent treatment of 30 seconds per hour 

 was given in some cases, arranged by clock contacts. Two different 

 arrangements were used for the treatments. In one a glass cylinder 

 containing the seeds was equipped at each end with electrodes. 

 These were pressed against the seeds through which the current was 

 thus directly passed. In the other, the seeds were placed in wet 

 sand held between perforated metal disks, which were used for the 

 electrodes. The entire layer was held in a glass funned in which the 

 growth of tiie radicle could be measured without removal. Eight 

 seta of 25 seeds each were used in each test, one set being the control 

 and the other seven receiving different strengths of current. Experi- 

 ments with barley showed that the growth of treated seeds increased 

 as the current strength increased up to a certain optimum value, 

 above which the growth decreased with increase in current strength. 

 With white mustard, rape, and red clover the optimum treatment 

 for both roots and stems was identical. 



Plowman (40, 4-0 has recorded the results of experiments con- 

 ducted at the Harvard Botanical Gardens on the iniluence of soil- 

 conducted currents on plant life. Platinum or carbon electrodes 

 were used, with potentials ranging from 5 to 500 volts. The regu- 

 lation of temperature was a serious difficulty — a fact mentioned for 

 the first time in connection with such experiments and one that may 

 have been ignored in earlier reports. Plowman found that seeds 

 near the anode were always killed by a current of 0.003 ampere or 

 more if continued for 20 hours. Seeds at the cathode were little 

 affected by currents less than 0.08 ampere. 



Gerlach and Erlwein (19, 20), at Bromberg, investigated the 

 effect of weak soil currents on germination and growth. The field 

 was made up of seven plats of 200 square meters each. Current 

 was taken from a car line and led to the three treated plats, which 

 were provided with iron plates 20 meters long by 30 centimeters 

 wide and 2 millimeters thick sunk into the soil at both ends. Each 

 of the seven plats was seeded hah with barley and half with potatoes. 



