30 HATCH EXPERIMENT STATION. [Jan. 



tyls, as well) of plants there exist opposite predominant 

 charges, — the root carr^dng predominant negative charges, 

 the stem predominant positive charges. When roots arp 

 stimulated with positive charges, acceleration results ; and 

 when stimulated with negative charges, acceleration is less 

 marked. In other words, stimulation may arise by chang- 

 ing the predominant charge of the organ, and those organs 

 respond most favorably to electrical stimuli in which oppo- 

 site charges predominate. In subjecting roots to a positive 

 charge, the predominant negative charges are overpowered 

 or neutralized by the charges, and stinmlation results ; like- 

 wise, in subjecting stems to negative charges, the predomi- 

 nant positive charges are overpowered or neutralized by the 

 negative charges, and stimulation likewise results ; but rein- 

 forcing predominant positive or negative charges by electrical 

 stimulation causes only a slight stimulus or retardation. 



From these experiments it would appear that direct cur- 

 rents appear to stimulate most organs which possess predomi- 

 nant positive charges (radish tops) , while interrupted induced 

 currents appear to stimulate most organs which possess pre- 

 dominant nejrative charo^es. There is known to exist a dif- 

 ference between the "make" and "break." In the latter 

 current, which is capable of giving rise to a modified physio- 

 logical reaction, the effects of the opening are alwaJ^s more 

 marked. The effects of the direct current noted above are 

 not so readily accounted for on the basis of this theory. 



These experiments have suggested other lines of investi- 

 gation, and a further report will be made concerning them. 

 It is possible that prolonged stinmlation gives rise to difler- 

 ent effects than brief stimuli. In prolonged stinmlation with 

 direct currents the positive electrode may have a toxic effect, 

 causing inhibition, as is the case with solutions with positive 

 ions. Physiologists have noted that the negative stimulates 

 where the positive current prevents stimulation, although 

 such does not hold in the case of plants, at least when charges 

 of a brief duration are employed. 



