18 BULLETIN 1379, U. S. DEPARTMENT OF AGRICULTURE 



In 1881, F. Elfving (15) undertook an interesting series of experi- 

 ments with different seedlings growing in culture solutions through 

 which lie passed battery currents of different strengths. After 

 germination the seedlings were mounted on corks which were floated 

 in the solution between electrodes 6 by 4 centimeters in size. He 

 found that in nearly every case the root would turn and grow in a 

 direction against that of the electric current. Plates of carbon, 

 zinc, and platinum were used, and all gave the same effect. Elfving 

 attributes this phenomenon of orientation to the slowing up of the 

 growth on the side of the root toward the positive pole. This same 

 phenomenon was noticed by Plowman (40, 41) in 1902-03. 



Holdefleiss (23) in 1884 selected several rows of sugar beets in a 

 field which showed a good stand and uniform conditions. In this 

 field copper plates 50 centimeters square were sunk perpendicularly 

 in the ground 50 centimeters deep, so that the plates included two 

 rows of beets. At the other end of the rows, 56 meters distant, 

 other plates were sunk, and between the two a 14-eell Meidinger 

 battery was connected. This same arrangement was used on a potato 

 field. Further experiments were conducted with copper and zinc 

 plates 33 meters apart connected by a solid copper wire. The report 

 of the experiments stated, in substance: 



(1) That an electric current was present on all treated plats throughout the 

 season, its presence being determined by a sensitive electrometer; (2) that the 

 rows of beets and potatoes between plates which were connected to the battery 

 showed no difference in growth at any stage of their development; (3) that the 

 beets and potatoes in rows between the zinc-copper combinations assumed a 

 somewhat fresher and stronger appearance about 10 days after the beginning of 

 the experiment, and the harvest showed an increased yield ranging from 15 to 

 24 per cent. 



It should be remembered, however, that in experiments with soil 

 currents the path of the current is not wholly by the most direct 

 route from one electrode to the other, but that the lines of flow 

 spread out through the soil in a way similar to the spreading of the 

 lines of force between the poles of a bar magnet. 



Experiments conducted by Wollny (48) included five plats 4 by 1 

 meter each in size separated by a path 1.2 meters wide and by boards 

 sunk 25 centimeters in the ground. On plats 1 to 3 a zinc plate 

 was sunk at both of the narrow sides, and these were connected as 

 follows: Plat 1, induction coil operated by three Meidinger elements; 

 plat 2, a battery of six Meidinger elements; plat 3, a battery of 

 three Meidinger elements. On plat 4 a zinc plate was sunk on one 

 end and a copper plate at the other, the two being connected above 

 ground by a copper wire. Plat 5 constituted a check or control plat. 

 Each plat was divided into four equal parts 1 square meter each 

 in area and seeded. Numbers of plants up on different dates showed 

 practically no effect for any of the different treatments. The yields 

 recorded at harvest time, based on an equal number of plants per 

 square meter, are shown in Table 20. 



