284 BIOLOGY. [BOOK m 



refuge and renews itself on the surface, and these two regiom 

 are bound together by a graduated succession of layers, more 

 vitalized in proportion as they approach the bark, more dead ic 

 proportion as they approach the centre. 



NOTE. 



The French, word aulier expresses better than any English word the white, 

 fresh tender wood between the body of the tree and the bark. Translator. 



