CONTACT STIMULATION 
GEORGE E. STONE 
Amherst, Massachusetts 
The experiments presented here have been carried on since 1904, 
at which time the writer observed some rather remarkable stimulated 
growth responses induced in sunflowers when surrounded by wire 
netting. At the time these observations were made we were carrying 
on investigations relative to the effect of varying atmospheric electrical 
potentials on plant growth, and for this purpose we made use of sun- 
flowers established in large earthen pots or wooden boxes located at 
different elevations in the open air. In some of these experiments 
the plants were surrounded with wire netting and in contact with 
the same but not with the soil, while in others (normals) no wire 
netting was used. In some instances the wire netting was not only 
in contact with the plants, but with the soil in which the plants were 
growing; the soil being grounded by the use of copper plates in the 
bottom of the boxes and by insulated wire, which led to the earth. 
In other instances the plants were in contact with wire netting and 
the soil, but were not grounded. The problem under consideration 
at that time, however, more particularly concerned itself with the 
influences of atmospheric electricity on plant growth, for which 
purpose organisms of various kinds, including bacteria, were exposed 
to elevations varying from thirty to sixty feet. Some of the earlier 
experimenters have maintained that when plants were grown in the 
free atmosphere surrounded with wires, they failed to develop, and 
would eventually die in consequence of being deprived of the bene- 
ficial effects supposed to be derived from atmospheric electricity. 
In passing we may state that we have never observed any remarkable 
mortality among plants in consequence of their being surrounded with 
wires even when the experiments were performed at more or less high 
elevation above the ground, and under ideal conditions for determining 
the effects of atmospheric electricity on vegetation. Moreover the 
growing of plants in conservatories where the electrical conditions of 
the atmosphere are quite different from those out-of-doors demon- 
strates the fallacy of this idea. On the other hand, we found that 
plants were greatly stimulated by wire enclosures, especially when 
they came in contact with the plants, and also the same stimulation 
was noted when plants were grown thickly together and the leaves 
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