1905.] PUBLIC DOCUMENT — No. 33. 19 



petioles and leaves in general was much less marked. The 

 length of the blade, petiole and whole leaf in general was 

 longer for identical periods of development in the electrically 

 treated plants than in the normal or untreated, although the 

 width of the blade was more generally marked in its devel- 

 opment in the normal than in the plants in the electrically 

 charged case. The morphological diflerentiation due to elec- 

 trical stimulation is shown in these experiments. 



The plants in the electrically charged case were of a lighter- 

 green color, and they showed a greater tendency to leaf burn 

 than did the normal plants. They also appeared to be more 

 succulent, but moisture determinations made of the leaves at 

 the close of the experiment showed no difference in this re- 

 spect. The roots in the treated case were relatively more 

 elongated than those in the untreated case. Whether tliis 

 form of electrical treatment stimulates plants more than cur- 

 rent electricity cannot definitely be determined, from the 

 lack of a suHicient number of comparative results. How- 

 ever, these two experiments would indicate, both from naked- 

 eye observations and from weights and measurements, that 

 static charges act as more pronounced stimuli than current 

 electricity when applied to soils. Electrical stinmlation 

 gives rise to effects similar to those caused b}^ lack of light, 

 or such as result from partial etiolation. The light-green 

 color of the foliage and the elongated organs were similar to 

 those noticed in plants grown in poorly lighted greenhouses 

 in winter, and in shaded plants grown in the forest. Other 

 kinds of electrical stinmlation appear to have the same gen- 

 eral effects on the plant. 



Comparison of Afmosjihei'ic Electrical Potential in Trees 

 and in the Free Air. 

 The idea has been advanced that trees, shrubs, and in fact 

 all growing ])lants, must form a means b}^ which the poten- 

 tial of the air and the earth is held in equilibrium. A living 

 tree does not offer such an enormous resistance to the jiassage 

 of electricity as dead wood does. We have charged small 

 plants in the labomtory to a sufliciently high potential so 

 that, when placed in the dark, sparks were emitted from 



