The phenomena underlying electrical stimulation are still imperfectly understood. There are many theories, however, in regard to its action. Nollet and Jallabert thought that the accelerated growth resulting from electrical stimulation was induced by the augmentation in the movements of the sap, and this view has been more recently held by Lemstrom. Fichtner, Sane and Tschinkel main tain that electricity renders soluble certain con stituents of the soil, as a result of which germina tion and growth are accelerated. On the other hand, Jodro attaches double significance to the action of soil currents, viz., a chemical and a mechanical action. Chemically it renders those constituents necessary for plant growth more soluble ; mechanically it sets the particles of soil into a state of vibration which results in an in creased rate of growth. It may be noted that both the chemical and mechanical theo ries fail to explain the results of stim ulation of seeds not sown in soil.
It is well known that feeble currents accelerate the movements of pro toplasm, and the augmentative cir culation theory has more to commend it than any of the others. Notwith standing the con siderable amount of accelerated growth manifesting itself as a result of elec trical stimulation, the time is not yet opportune to apply this force very largely to the growth of crops, since the application of current electricity to crops has not been sufficiently tested on a large scale ; neither has it been demonstrated that electrical stimulation would always prove advantageous to plants. There appears to be a tendency for electri
cally stimulated plants to develop a more spind ling growth than those grown under ordinary conditions.
Conclusions concerning the effect of current electricity on plants.
In conclusion, it may be stated that the application of electrical stimulation to crops is not as yet practicable, al though undoubtedly in the future electricity will be more exten sively employed in agriculture, and it is hoped that agricultur ists will be able to make use of the enormous amount of electri cal energy constantly stored in the atmosphere. From the work that has been done, the follow ing very general conclusions may be drawn : (1) Electricity exerts an ap preciable influence on plants.
(2) Ea ectrica stimulation gives rise to an accelerated ger mination and growth of plants, the foliage in some instances (radishes) being stimulated more than the roots.
(3) The strength of current inducing acceleration is confined to a narrow range.
(4) There is a minimum, opti mum and maximum stimulus. The minimum cur rent is equal to about .005 milliamperes, the opti mum to about .22, and the maximum is determined entirely by conditions.