PHILOSOPHY OF DR. ERASMUS DARWIN. 209 



day. For this cannot be ascribed to irritation, because 

 cold means a defect of the stimulus of heat ; but as the 

 want of accustomed stimuli produces pain, as in coldness, 

 hunger, and thirst of animals, these motions of Tege- 

 tables in closing up their flowers must be ascribed to 

 the disagreeable sensation, and not to the irritation of 

 cold. Others close up their leaves during darkness, 

 which, like the former, cannot be owing to irritation, as 

 the irritating material is withdrawn. 



" The approach of the anthers in many flowers to the 

 stigmas, and of the pistils of some flowers to the anthers, 

 must be ascribed to the pa^ion of Jpye, and hence 

 belongs to sensation, not to irritation. 



" III. That the vegetable world possesses some degree 

 of voluntary powers appears from their necessity to 

 sleep, which we have shown in Section XVIII. to 

 consist in the temporary abolition of voluntary power. 

 This voluntary power seems to be exerted in the 

 circuleir movement of the tendrils of the vines, and 

 other climbing vegetables ; or in the efforts to turn the 

 upper surfaces of their leaves, or their flowers, to the 

 light. 



" IV. The associations of fibrous motions are observ- 

 able in the vegetable world as well as in the animal. 

 The divisions of the leaves of the sensitive plant have 

 been accustomed to contract at the same time from the 

 absence of light ; hence, if by any other circumstance, 

 as a slight stroke or injury, one division is irritated 

 into contraction, the neighbouring ones contract also 

 from their motions being associated with those of the 

 irritated part. So the various stamina of the class of 



p 



