' 9i 



ON THI?. DIOX.EA MUSCIPULA. 



nhich of course would be governed by light, heat, or mois- 

 ture) ; that I shall not endeavour to refute it. 

 The contrac- We have now seen, that the contraction of the leaf of the 

 tion IS owing cliona?a muscipula takes place in conseciuenceof the anplica- 

 toastiniulus,. . ,. . '^, J , • , , , , , 



tion ol a stinuilus; una that it does not seem probable, that 



this action can be explained on mechanical principles. 

 Wliat inference then must we draw ? In my opinion we must 

 again be forced to infer the same conclusion as we did with 

 respect to the species of drosera, namely, that this plant is 

 possessed of an iidierent power, by which, when stimulated, 

 it is enabled to contract; and if this inference be just, we 

 would say, that the leaves possess irritability. 



In considering the motions of this plant it must always 

 be remembered, that it seems to move purely in consequeuQc 

 of the application of a stimulus. 

 .Sensitii^e I shall uext i)roceed to the mimosa pudica. It is well known, 



gant. ^jj? ^,g i^i^g ,^ leaf of this plant similar to what is represented 



i?s leaves, PI. Ill, tig. 5, and then by means of a pair of scissars (com- 



pletely dry), cut off half the pinnula A, tiiis pinnula will 

 contract at its joint either immediately, or in a few seconds; 

 its neighbour, or opposite pinnula, B, closing at the same 

 time, or soon after. The pinnulre A and li having come 

 into contact, there will be a pause or a short cessation of 

 motion, but in the course of a few more seconds the next 

 pair of pinnulse, CC, will also shut up, and the sr.me will 

 liap{)en with every pair of pnmula^ of that piiuia succes- 

 sively; only with this difference, that the intervals bttweca 

 the shutting up of each pair of pinnulte will be shorter, the 

 farthtr they are from the pinnula that was cut. After the 

 whole of the pinnulae of this pinna have completely closed, 

 and a little interval, then the joint D will become affected 

 i. e. it will bend so as to allov>- the pinna to dioj) considera- 

 bly. Nevertheless, the motion is often not so obvious in 

 this joint as in that to be mentioned. A longer pause will 

 now intervCi\e, in pome cases so long as to make iis suppose 

 ♦liat all motion is at an end ; but at length, the joint E sud- 

 denly bends, and astonishes the beholder. The petiole F 

 now instead of fo'-niing an acute angle with the stem 

 above the joint, forms a very obtuse angle with it. M'e 

 sh;dl BOW havi' anotlicr cwsution of mvtion, and then 



tliQ 



