Page:Life Movements in Plants.djvu/169

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.

TABLE IX.—PERIODS OF TRANSMISSION OF POSITIVE AND NEGATIVE IMPULSES IN THE PETIOLE OF AVERRHOA AND STEM OF MIMOSA.

No.	Specimen.	Distance in mm.	Stimulus.	Transmission period for positive impulse.	Transmission period for negative impulse.
1	Averrhoa …	70	Thermal …	22.522 secs.	22.565 secs.
2	Averrhoa„ …	130	Thermal„ …	22.540 secs.„	22.595 secs.„
3	Averrhoa„ …	10	Induction-shock	22.5  6 secs.„	22.520 secs.„
4	Averrhoa„ …	20	Induction-shock„ …	22.514 secs.„	22.548 secs.„
5	Averrhoa„ …	35	Chemical …	22.521 secs.„	22.550 secs.„
6	AverrhoaMimosa …	5	Induction-shock	22.50.5 secs.„	22.512 secs.„
7	Averrhoa„ …	10	Induction-shock„ …	22.50.6 secs.„	22.59.4 secs.„
8	Averrhoa„ …	20	Induction-shock„ …	22.51.1 secs.„	22.510 secs.„
9	Averrhoa„ …	60	Induction-shock„ …	22.52 secs.„	22.529 secs.„
10	Averrhoa„ …	35	Chemical …	22.55 secs.„	22.517 secs.„

EFFECTS OF DIRECT AND INDIRECT STIMULUS.

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:—

1. Effect of all forms of Direct stimulus is a diminution of turgor, a contraction and a negative mechanical response.
2. Effect of Indirect stimulus is an increase of turgor, an expansion and a positive mechanical response.