20 HATCH EXPERIMENT STATION. [Jan. 



many points of the leaves, and living plants will readily 

 take chai'Ofes from a static machine. It has also been main- 

 tained that trees modify the electrical potential of the atmos- 

 phere of their immediate surroundings. 



Grandeau^ and other experimenters have shown that when 

 plants are grown under wire netting they develop less in a 

 given space of time than do plants grown under similar 

 conditions in ever}^ respect as regards light, etc., in the free 

 atmosphere. The interpretation of this phenomenon is, 

 that wire screens modify the atmospheric electrical potential, 

 or absorb the electricity, as it were, to the detriment of the 

 plant. This method of experimenting with wire nets we 

 have employed only to a limited extent, and at present have 

 not a sufficient number of results on which to report. Unfor- 

 tunately, most of the experiments previously made in this 

 line are open to severe criticism, from the fact that too few 

 plants were employed, and different methods of surrounding 

 the plants with ^vire netting prevailed, which accounts for 

 occasional conflicting results. Grandeau obtained similar 

 results by growing plants under a chestnut tree, as under a 

 wire netting ; and he concluded that it is probable that trees 

 modify to a large extent the electrical potential of the atmos- 

 phere in their immediate neighborhood. The object we had 

 in view in these experiments was to ascertain, among other 

 things, whether trees did modify in any way the electrical 

 potential of the atmosphere in their immediate vicinity. In 

 order to ascertain whether there is any discernible diflerence 

 between the atmospheric electrical potential in trees and in 

 the free air, at corresponding height and location, we made 

 a series of three readings daily from April to July, and daily 

 readings during the remainder of the experiment, with col- 

 lectors and a Thompson quadrant electrometer. These, 

 observations were started early in the spring, before any 

 foliage had developed, and continued until after the leaves 

 had fallen. A collector was placed in an elm tree, at a 

 heiofht of 40 feet above the ground, at a fork between two 

 limbs from which it was insulated. The collector was sit- 

 uated about on a level with, or slightly above, the spread of 



1 "Comptes rendus," T. LXXXVII., 1878, pp. 60, 285, 939. "Chimie et Physiologic 

 appliquecs a I'Agriculture et a la Sylviculture par L. Grandeau," Paris, 1879, p. 279. 



