AND ANIMAL LIFE. 147 



tion, tends also to promote an excitation of the 

 animal frame, and both equally suffer from the 

 same cause. The circulation of the sap in plants 

 acquires greater motion, and more invigorating 

 properties from the application of the sun's rays : 

 these conditions form what is called its vitality, 

 the energy of which is displayed in the evolution 

 of the bud, leaf, and flower ; but it is probable 

 that these are put forth at a time when the con- 

 tinuance of the weather is little to be depended 

 upon ; and if to a few warm days succeed nights 

 more severe than is compatible with their pro- 

 gress, we observe that they soon languish and die. 



To say that they suffer from their extreme 

 sensibility, is no explanation of the laws which 

 regulate their economy. The capillary system 

 of plants changes with the seasons, as well as that 

 of animals. The minute vessels of its organiza- 

 tion are charged with a peculiar fluid, and the 

 qualities of this contribute to create others still 

 less cognizable by microscopic means, presenting 

 an enlarged surface of circulation to the influence 

 of cold. The leaves of plants may be considered 

 to compose their surface, and, from the number 

 of these in spring, we may estimate the proba- 

 bilities of danger. 



The dread of the agriculturist is the too early 

 appearance of vegetation. His fears are not ex- 

 cited by the mere symptom of germination, but 



