, 



Plants. 180 



After the sap has thus ascended to the 

 eaves, it there undergoes certain altera- 

 tions, and is converted into another fluid, 

 called the succus proprhis, or peculiar 

 juice ; which, like the blood in animals^ 

 is afterwards employed in forming the- 

 various substances found in plants. The 

 leaves may therefore be considered as 

 the digesting organs of plants, and as 

 equivalent in some measure to the sto- 

 mach and lungs of animals. The leaves 

 consequently are not mere ornaments ; 

 they are the most important parts of the 

 plant. Accordingly we find, that when- 

 ever we strip a plant of its leaves, we 

 strip it entirely of its vegetating powers 

 till new leaves are formed ; for when the 

 leaves of plants are destroyed by insects, 

 they vegetate no longer, and their fruit 

 never makes any further progress in ri- 

 pening, but decays and dries up, 



Leaves on one side draw nutriment 

 from the air, and perspire on the other ; 

 for plants, as well as animals, perspire, 

 and, in both cases, this function is essen- 

 tial to health. The quantity they per- 

 spire varies, according to the extent of 

 the surface from which it is emitted, the 



