Sensation in Plants. 143 



lower animals. With plants an astonishingly small stimulus 

 suffices ; and even with allied plants one may be highly 

 sensitive to the slightest continued pressure, and another 

 highly sensitive to a slight momentary touch. The habit 

 of moving at certain periods is inherited both by plants and 

 animals ; and several other points of similitude have been 

 specified. But the most striking resemblance is the localisa- 

 tion of their sensitiveness, and the transmission of an 

 influence from the excited part to another which conse- 

 quently moves. Yet plants do not of course possess nerves 

 or a central nervous system ; and we may infer that with 

 animals such structures serve only for the more perfect 

 transmission of impressions, and for the more complete 

 intercommunication of the several parts/ 



But as if to approach more nearly the feelings of Dr. 

 Percival, he says at the end : ' It is hardly an exaggeration 

 to say that the tip of the radicle thus endowed, and 

 having the power of directing the movements of the ad- 

 joining parts, acts like the brain of one of the lower animals ; 

 the brain being seated within the anterior end of the body, 

 receiving impressions from the sense-organs, and directing 

 the several movements.' 



After all, and even after reading Darwin's book on 

 the motion of plants, we cannot be held to be nearer than 

 Wordsworth, who says in ' Lines written in Early Spring ' : 



Through primrose tufts in that sweet bower, 



The periwinkle trails its wreaths ; 

 And 'tis my faith that every flower 



Enjoys the air it breathes. 



The budding twigs spread out their fan, 



To catch the breezy air ; 

 And I must think, do all I can, 



That there was pleasure there. 



