SECT. IV. INSTINCT. 



If their motion is temporarily suspended by grasping 

 them in the hand, they quicken it when the hand 

 is removed, as if to make up for lost time, and by 

 and by resume their original velocity. This move- 

 ment does not depend upon the application of any' 

 external stimulus, because it takes place alike by 

 night and by day, in the dark and in the light, and 

 requires only a very warm and fine day to be effected 

 in the best style ; the leaves exhibiting then a sort 

 of tremulous motion in addition to that already de- 

 scribed. Such is a phenomenon that puzzles and 

 astonishes every beholder, and still remains inexpli- 

 cable ; but which participates more of the character 

 of animal spontaneity than any other movement 

 hitherto observed in vegetables. 



SECTION IV. 

 Instinct. 



THERE is also a variety of phenomena exhibited Difficulty 

 throughout the extent of the vegetable kingdom, goodTJl- 3 

 some of which are common to plants in general, niuon - 

 and some peculiar to certain species, that have been 

 thought by several botanical writers to exhibit indi- 

 cations, not merely of sensation, but of instinct. 

 The tendency of plants to incline their stem and to 

 turn the upper surface of the leaves to the light, tire 

 direction which the extreme fibres of the root will 

 often take to reach the best nourishment, the fold- 



VOL. II. 2 H 



