Page:Life Movements in Plants.djvu/248

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LIFE MOVEMENTS IN PLANTS

tive reactions. Of these the positive is masked by the predominant negative.

So much for theory; is it possible to unmask the contained positive in the resulting negative response under Direct stimulus? This important aspect of the subject will be dealt with in the following Paper.

SUMMARY.

The application of Direct stimulus gives rise to an electric response of galvanometric negativity. The application of stimulus at a distance from the responding point, i.e., Indirect stimulus, gives rise to positive electric response.

The mechanical responses of sensitive plants also exhibit similar effects, i.e., a negative response under Direct, and positive response under Indirect stimulus.

In the responsive variation of growth, Direct stimulus induces a retardation, and Indirect stimulus an acceleration of the rate of growth.

The effects of Direct and Indirect stimulus on vegetable organs in general are as follows:

Direct stimulus induces negative variation of turgor, contraction, fall of leaf of Mimosa, electric change of galvanometric negativity, and retardation of the rate of growth.
Indirect stimulus induces positive variation of turgor, expansion, erection of leaf of Mimosa, electrical change of galvanometric positivity and acceleration of the rate of growth.
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