ON THE IRRITABILITY OF VEGETABLES. QJ\ 



body, or toward the footstalk of the leaf*. This ivoulA 

 seem then to prove, that pressure alone can never be the 

 cause of the contraction of the leaves of the droserae, and 

 consequently, that the action is not owing to a cause purely- 

 mechanical. 



Having now seen, that the action of these leaves cannot The motion 

 be accounted for either by the theory of Brousonnet, or owin S t° . 



•> f 7 something lrn- 



that of Sennebier, to what must we ascribe them ? It ap- table and equi- 

 pears to me, that the motions of these leaves must be owing y * leat t0 U1US " 

 to some other cause, and this cause a moving onef, deno- 

 minate it what you will, for we must admit, that these leaves 

 contract in consequence of the application of a stimulus ; 

 and I conceive, that this action is performed, if not by 

 muscles, at least by something which is equivalent to mus- 

 cles in the animal body. 



I have seen no other attempts to prove,* that the contrac- The principle 

 tion of the leaves of the droserse is owing to any mechanical J'™™'^ 1 

 action ; and other authors seem disposed to admit it as a mitted by se- 

 proof of vegetable irritability. Among these authors we vera, « 

 have the illustrious Dr. Smith, who seems to think, that the 

 motions of the leaves are to be explained on the principle of 

 irritability^. We have also the no less celebrated Wilden- 

 ouw, who, immediately after mentioning the irritability of 

 the mimosa, dioncea, &c, says: " Less conspicuous, but 

 " easily demonstrable, is the irritability of the indigenous 

 " species of sundew, drosera rotundifolia and longifoiia§." 

 I will now conclude this part of the paper by quoting the 

 words of Dr. Smith, which he uses when speaking of the 

 mimosa, &c. : " it is vain to attempt any mechanical solu- 



* That this motion does not depend on pressure may be still better il- 

 lustrated, by placing a fly, or some other body, on the apex of a leaf of 

 the drosera longifolia. The hairs near the foreign body will contract 

 around it, and then the apex of the leaf will rise upwards, and turn in- 

 wards, until it touches the base. Or if the offending body is small, the 

 leaf will become convoluted around it. 



+ I mean a cause, which produces motion, 



{ Philos. Trans, abridged, vol. XXI, page 243. 



§ Puincip. Botany and Veg. Physiol. (Translation) p^ge 222, edt. 

 1805. 



tion" 



