i)r. Bruce's Account of, &t, 3^57 



them move alternately, or, in fhort, m any ordef yoir pleafe './ 

 touching hi a proper manner the leaf you. wifh to put in mo- 

 tion. Bat if the impreilion, although made on a fnigle leaf,, 

 be flrong, all the leaves on that pinna, and femetimes on tlie 

 neighbouring ones, will be affected by it. 



What at firfl feemed furprifing was, that notwithftanding 

 this apparent feniibility of the leaf, I could with a pair of 

 fharp fciffars make large incifions in it, without occafioning the 

 fmaliefl motion ; nay, even cut it almoft entirely off, and the 

 remaining part flill continue unmoved;, and that then, by 

 touching the. wounded leaf with the finger or point of tlie 

 fciffars, motion would take place as if no injury had been 

 offered. But, on further examination, I found', that although 

 the leaf was the oftenfible part v/hich moved, it was in hCt 

 entirely paffive, and that the petiolus was the feat both of fcnfe 

 and adion : for although the leaf might be cut in pieces, or 

 fqueezed with great force, provided its diredion was not" 

 changed,, without any motion being occafioned; yet, if theim- 

 preflion on the leaf was made in fuch a way as to affcdl the 

 petiolus, the motion took place. When, therefore, I wanted; 

 to confine the motion to a fingle leaf, I either touched it fo as 

 only to affed its own petiolus, or, without meddling with the 

 leaf, touched the petiolus with any fmall-pointed body, as a p.ia 

 or knife. 



By comprefling the univerfal petiolus near fhe place where 

 a partial one comes out, the leaf moves in a few feconds, in the- 

 fame manner as if you had touched the partial petiolus. 



Whether the impreffion be made bypundure, percuflion, or • 

 compreffion, the motion does not inftantly follow ; generally 

 feveral feconds intervene, and then it is not by a jirk, but 



regular 



