Page:Life Movements in Plants.djvu/243



It has been shown that the direct application of stimulus gives rise, in dill‘erent organs to contraction, diminution of turgor, fall of motile leal', electro-motive change of galvano- metric negativity, and retardation of the rate of growth. I shall now inquire whether Indirect stimulus, that. is to say, application of stimulus at some distance from the i'c-spond5 ing organ, givcs rise to an ell'ect. dill'erent from that of direct application.

I have already (Iv-scribed the effect of Indirect stimulus on motile organs (p. 136). A feeble stimulus applied at a distance was found to imluCe an erectile movmm-nt or posi- tive response of the leaf of illi’lmmt or of the leallet of Arenlwu. This reaction is indicative. of increase of turgor, an effect which is diametrically opposite to the diminution of turgor induced by the effect of Direct stimulus. It was also shown that an increase in the intensity of Indirect stimulus or a diminution of the intervening distance