142 EXPERIMENT STATION. [Jan. 



tivelj, the leaves were stiimilatcd least and tiie roots most; that 

 is, the roots, which are normal to an environment negatively 

 charged, were stimulated most by the positive charges. In the 

 case of galvanic stimulation of roots it is known that weak cur- 

 rents induce negative bendings ; that is, towards the cathode, 

 while strong currents induce positive landings, or towards the 

 anode. In the negative reactions, which are induced by weak 

 cuiTcnts, there is a greater growth on the side of the root towards 

 the positive pole or anode than towards the negative pole or 

 cathode, but there is some doubt as to whether the reverse holds 

 true for positive galvanotropic bendings. In the case of posi- 

 tive galvanotropic bendings Brunchorst has pointed out that the 

 reaction is the result of pathological conditions, and it is main- 

 tained that bendings towards the anode are due to injury of the 

 delicate root tip by the strong currents employed. This inter- 

 pretation of the phenomena appears to harmonize with the re- 

 sults which we have obtained with positive and negative electrical 

 charges on plants. The positive charges give the greatest and 

 the negative the least accelerated growth. Since the positive 

 charges stimulate mostly those cells on the surface of the root 

 nearest to the anode, those cells would grow more rapidly and 

 the normal downward direction of the root would be directed 

 towards the negative pole or cathode. The burning effect on 

 trees from positive and negative electrodes is similar, the posi- 

 tive producing the greater injury, and this coincides with our 

 results obtained by using strong positive static charges on plants, 

 viz., strong positive static charges cause a greater degree of 

 retardation and injury than negative charges. The use of 

 strong positive currents would result in the cells on the anode 

 side of the root being retarded, hence bendings towards the anode 

 would result. 



To summarize we might state that the effect of positive and 

 negative stinnilation on plants offers a mechanical explanation 

 of the positive and negative galvanotropism in roots. When 

 plants are grown between positive and negative electrodes, each 

 electrode exerts a characteristic influence on the root, and that 

 surface of the root nearest to the anode will be affected according 

 to the nature of the stimulus on that side ; and conversely, that 

 part of the root adjacent to the cathode will be affected accord- 



