. 



LECT. II.] VITAL FUNCTIONS OF PLANTS. 65 



dustry and ingenuity to diffuse more generally the 

 productions of every quarter of the globe over its 

 surface ; for, had this not been the case, the plants 

 of every climate must have always remained the 

 same as they were at the creation of the world. 



As the vital energy of vegetables is supported 

 by the application of external agents, particularly 

 heat, the abstraction of these in part must neces- 

 sarily diminish the activity of the vegetable func- 

 tions. This is the case in winter, during which 

 season, plants, like some animals, remain in a 

 torpid state ; and, although they still live, yet the 

 powers of vegetation are at a stand ; and even in 

 those that retain their foliage and verdure, no vi- 

 sible increase of their parts takes place. That their 

 preservation during this period depends on an in- 

 herent living principle is obvious ; for, when the 

 severity of the season is sufficient to overcome its 

 preservative power, no renewal of their active func- 

 tions takes place at its termination : but, in general, 

 as soon as the animal creation begins to feel the 

 warmth of spring, the buds of trees swell, and pro- 

 trude their leaves, and the plant rapidly advances 

 in growth ; with the increasing warmth of the 

 summer sun the flowers are expanded^ and the fruit 

 arrives at perfection ; till, as it declines in autumn, 

 the leaves fall, and the state of torpidity is again 

 resumed with the cold of winter. 



Thus I have endeavoured to prove that vege- 

 VOL. i. F 



