Page:Life Movements in Plants.djvu/169

Rh diminution of distance gives rise to a resultant negative response, the positive being masked by the predominant negative.

From what has been said it will be understood that the exhibition of positive response is favoured by the conditions, that the transmitting tissue should be semi-conducting, and the stimulus feeble. It is thus easier to exhibit the positive effect with the feebly conducting petiole of Averrhoa than with the better conducting petiole of Mimosa. It is, however, possible to obtain positive response in the Mimosa by application of indirect stimulus to the stem in which conduction is less rapid than in the petioles.

From the results given in course of the Paper we are able to formulate the following laws about the effects of Direct and Indirect Stimulus on pulvinated organs:—

{{ol|item_style=padding-left: -10px; text-indent: 30px;|Effect of all forms of Direct stimulus is a diminution of

tlrgob, a contraction an'd a negative mechanical response.

2. Effect of Indirect stimulus is an increase of iurgor, an

expansion and a positive mechanical response.