MOTION IN PLANTS. 357 



The third clay I kept it in the dark room all day, and it kept in the 

 flexed state ; about eight o'clock in the evening I threw a light upon 

 one leaf from a concave mirror, by means of two candles put close 

 together, which was continued three hours, but it had no effect. 



The fourth, fifth, and sixth days it was kept in the dark room, and 

 still continued flexed, but was beginning to decay. 



This process of expansion and collapsing does not arise from an 

 increase and decrease of heat between day and night ; for in the winter, 

 in the hothouse, where there is very little difference in the degrees of 

 internal and external heat, and less so in the house, where a pretty 

 regular heat is kept up, we find this plant performing the same 

 motion. 



If the stem of the Mimosa pudica be touched with a hot wire, the 

 leaves above collapse. 



If the top of a branch or pinnule is touched with the hot wire, the 

 whole leaf gradually collapses, then all the leaves above, while only 

 one or two at most collapse below. 



Stimulants, such as a strong solution of common salt, did not pro- 

 duce a collapse, excepting when put on the joint, and this uncertain. 



Ether applied to the layers of a pinnule will oblige the whole leaf 

 to collapse, as also other leaves on the stem, both above and below : a 

 cut into a strong stem will not produce a collapse ; but if into the 

 tender part, it will produce a collapse of all above, and commonly on 

 the same side ; but a deep cut may affect the other side. Tie a liga- 

 ture round the stem or stems of a branch, it may be cut below this 

 without affecting the petiole or pinnule above ; the branch may even be 

 cut off without a collapse. If a collapse be produced, they do not ex- 

 pand so freely. 



It is curious the not collapsing of the leaves upon being gradually 

 heated, so as to be burnt. It would seem that the presence of the 

 heat hindered collapsing. 



The Sensitive -plant has evidently parts fitted for motion. At the 

 setting on of the footstalk to the stem, and the joining of the folioles to 

 the rachis of the compound leaf, there is evidently a part in both dif- 

 ferent from the other parts of the same stalk, &C. 1 It is in these parts 

 that the flexion and the extension are performed : but when the leaf 

 jjerforms a rotatory motion, which it will do when the plant is inverted, 

 the whole of the footstalk appears to join in this motion, so that it is 

 simply a twist upon the axis of the footstalk. 



In the Dionea muscipula, or Tipitiwitchet, the whole of the lobed part 



1 [Hunt. Preps. Phys. Series, Nos. 29, 30.] 



