2("2 ON THE IRRITABILITY OF VEGETABLES. 



" tile power, by which the elementary fibres are drawn to- 

 " ward each other*," 

 Many consider Many authors, as Gmelin, Smith, Darwin, &c.,have a long 

 time since used the word irritability, when speaking of the 

 . motions of the parts of vegetables; and in the present time 

 it is nearly as common to talk of the irritability of the ve- 

 getable as of that of the animal kingdom. When I began 

 this paper, it was my intention, to have taken a compendi- 

 ous view of all that had been said on vegetable irritability ; 

 but the subject having now become so extensive, I found 

 time would not permit me to make those experiments, which 

 would have been requisite either to have proved that the ve- 

 getable kingdom in general was endowed with irritability, 

 or to have disproved it. I have therefore contented myself 

 at present with detailing sofne experiments made on parti- 

 cular plants : and even from these I hope to prove, that, if 

 we do not admit that vegetables possess irritability, at least 

 that they are possessed of something which is adequate to 

 the muscular power in the animal body ; and I am convinced, 

 that without admitting this, many beautiful phenomena 

 must perhaps for ever baffle the attempts of physiologists 

 to explain them. 

 Sennebier un- One of the most celebrated vegetable physiologists, Sen- 

 willing to allow neLier b . ls already treated extensively on this subject. He 

 related almost every thing then known concerning the mo>- 

 tions of vegetables, but has always been unwilling to allow, 

 that an irritable principle had any share in these motions, 

 and has tried to explain every phenomenon (which was be- 

 fore thought a proof of irritability)on mechanical principles. 

 In the following pages 1 intend to quote some of his opinions, 

 and endeavour to overturn them. 



As confusion might arise from the word irritability not 

 being well defined, it become* first necessary, to have Sen- 

 nebier's opinion on this point, and then to fix what we un- 

 lit; definition derstand by it at present. " Sennebier says : " Irritability 

 * l :t - " is that property, which forces a body to contract itself 



"-when it is acted upon in a manner proper to produce this 

 " effect; animals manifest this contraction in their mus- 

 " cles in consequence of burning, pricking, or the contact 



* Elem. Pbys, vol. 4, p. 410. 



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