68 VITAL FUNCTIONS OF PLANTS. [LECT. II. 



leaves and flowers when touched ; the turning of 

 leaves to the light; the opening and closing of 

 flowers at a certain hour of the day, or, as it has 

 been termed, vigiliee florum ; and the sleep of 

 plants * ; each of which we shall minutely inves- 

 tigate in its proper place. 



Plants, like animals, are destined to perform 

 their functions for a limited period only ; some live 

 for one season, others twice that period: the 

 Apple-tree flourishes through a century ; and the 

 Cedar is supposed to brave the tempests of a thou- 

 sand years : but the hand of Time sooner or later 

 presses upon all of them ; and without the aid of 

 external injury, their vegetative powers cease ; 

 and, sharing the fate of all organized beings, they 

 submit to decomposition, and crumble into their 

 primeval elements. 



* Darwin (Phytologia, sect. viii. 4) ascribes these circum- 

 stances to volition ; an opinion which I shall have an opportunity 

 of combating in another place. 



