1904.] PUBLIC DOCUMENT — No. 33. 29 



There is a minimum, ()i)timiiiu and maximum current 

 which gives rise to reactions similar to tliosc obtained from 

 other forms of stinudi. There is also a well-defined latent 

 period, such as Ave iiiid associatc^d with heliotropie and ge.o- 

 tropic stimuli, etc. Moreover, there exists a definite relation- 

 ship between current intensity and perception, or reaction 

 of the organism, as in chemotactic stinmlation. 



It was observed b}^ early experimenters that there existed 

 a difference in the growth of plants when subjected to what is 

 termed positive and negative charges. Our limited experi- 

 ments in this respect have shown that when seeds were treated 

 with a positive charge the growth of the roots was greatly 

 accelerated, while the stems were much less so ; and con- 

 versely, when treated with a negative charge, the stem 

 showed a greater accelerated growth than the roots. Ger- 

 , mination — that is, radical development — was greatly accel- 

 erated when seeds were charged positively, although Avhen 

 charged with a neo^ative charge o-ermination at first was nmcli 

 less accelerated than in untreated seed. Thus we have a 

 positive charge stimulating organs which react in a positive 

 manner, and a negative charge stimulating organs which 

 react in a negative manner ; also the effect of a positive 

 charge acting as a slight stimulus or retarding organs which 

 act in a negative manner, and the negative only slightly stim- 

 ulating or retarding positive reacting organs. 



It would also appear as if positive charges had a tendency 

 to produce attenuated or elongated root development. In 

 regard to this point, it would be interesting to ascertain 

 whether positive charges increase geotropic irritability. One 

 of the recent conceptions of solutions is that they contain 

 ions which are atoms or groups of atoms ]K)sitively or nega- 

 tively charged. It has been observed that solutions with a 

 predominant positive charge, such as acids, and those with a 

 predominant negative charge, bases and salts, have a certain 

 definite effect upon protoplasm which is identical with those 

 produced by positive and negative electrical stimulation. 

 There is also reason to believe that protoplasm consists of 

 particles which are charged positively and negatively. It is 

 possible that in the protoplasm of roots and stems (hypoco- 



