ON THE DIONiEA MUStJPULA. f^JJ, 



thejoii'.tHvTillslightly bend ; thenanother pause; then aslmt- 

 tijjg up of tlicpair of piunulos, II, and so on with the other piii- 

 nulie, till the wholepinnais closed. The mt>tion3 however wiii 

 not be so regular in this pinna, as they were in the other, for us 

 the pinnulae II approach they press forwards the next pair, 

 and so on with all the rest. If we take another leaf si- 

 milar to that of which I have given a sketch, aud cut the 

 pinnulaof the pinna A, B,C, or D, fig. G, in the same man- 

 ner, a variety of beautiful experiments may be made; whicli 

 will strike the experimenter with amazemeut, and excite an 

 anxiety in his mind to ascertain the cause of this motion. 



The above related experiment 1 think sufficient for my xhe motion 



present purpose; which is to endeavour to show, that these "f*^ to beex- 



,. ^, 1 • 1 I • 1 • • 1 plained on rne- 



motions caniiot be explamed on any mechanical principles, clmnical pdn- 



and that they very probably depend ou the irritability of tlie ciples. 



plant. 



It does not appear, that the motion is occasioned by im- 

 pulse ; for a bit of the pinnula may be cut off almost with- 

 out producing any motion. But allowing that a little mo- 

 tion were produced in the injured pinnula, it comes natur- 

 ally, as a question why does the motion become so exten- 

 sive? how is the impulse communicated to the origin of the 

 petiole? These questions I believe will never be satisfacto- 

 fily answered upon the principle mentioned. 



Campuretti's theory will be liable to nearly the same ob. Exaniinau»« 



Actions as that of Mrs. Ibbetson noticed below. I do not "^^ [^^^f '^'"*' 



•'• • • 1 , c ^'^"•^ theory. 



here intend to deny, tr.at a structure similar to what Mrb. 

 Ibbetson describes is to be found in the niiuiosa scnsitiva ; 

 although I confess my doubts have increased of late. I asa ' 



willing to allow, that ail is accurate, and ^hali proceed now 

 -to inquire, whether by such a structure, acted upon by 

 fceat, light, or moisture, we could possibly ex})!aii-! the mo- 

 tions of th-e mimosa pudica. In the experiments relate^i^-jnjg motion 

 »bove, I presume no one would say, that moisture was the ""^ produced 

 I- I ^- ^1 • -.1 ij • by moisture, 



cause or the motion ; as the scissars were quite dry. it is 



to be remembered also, that this plant will perform its mo- 

 tions uiuler water. As there was no change of light, cou- t; \^ 

 SLqii<M)tly this had no share in the cflcct. Besides, whin 

 moisture is produced in consequence of the ubstraclion oi j3.,j.]r,jps?, 

 lijiht, all tlic pinnule? shut up at tlio-samc time; Jiot in the 



