l] UPON THE RATE OF GROWTH 407 



have been of two general kinds. On the one hand the 

 seedling is electrified by passing a current through the soil in 

 which it is growing and after several days comparing it with 

 an untreated seedling. On the other hand the tension of the 

 atmospheric electricity is altered either by electrifying the air 

 of the chamber in which a plant is growing, or by isolating a 

 plant from the action of atmospheric electricity by means of a 

 cage made of fine wire and with meshes so wide that a minimum 

 amount of light is cut out (Fig. 115 A and B). 



The method of passing a current through the soil has been 

 employed by WARREN ('89), CHODAT ('92), McLsoD ('93 and 

 '94), and by other investigators with results favorable to the 

 plants. McLEOD passed the current transversely. He sunk 

 plates of metal on either side of the pea seeds employed in the 

 experiment and used a current from a single cell. While 

 the control seedlings germinated somewhat earlier than the 

 electrified ones, at the end of 45 days the latter had outstripped 

 the former. Again, a coil of wire, partly stripped of its insula- 

 tion, was imbedded in the ground, and from a lot of similar 

 mustard seeds some were placed next to the uncovered wire 

 and others about one inch away from the insulated part of the 

 wire. A constant current was sent through, and at the end of 

 seven days the seedlings planted near the uncovered wire were 

 one-third larger than the others. CHODAT used a current 

 passing lengthwise through the plant. Similar beans were di- 

 vided into two equal lots and each was reared in glass cylinders 

 under similar conditions, except that one was unelectrified 

 while the other was electrified by the following method. The 

 cylinder rested on one armature of tin-foil while the other was 

 suspended 1.8 meters over the first. The armatures were 

 connected with a Holtz machine and a current was passed 

 through the cylinder for about three hours each day. The 

 result was that on the fourth day leaves began to show on 

 the electrified seedlings but not on the control ones, and 

 on the seventh day all the electrified seedlings had attained 

 considerable size, whereas the control ones were just making 

 their appearance. The electrified seedlings were spindling, 

 however, much as if reared in the dark. WARREN'S experi- 

 ments are noteworthy in that he found the seedlings which 



