144 



been mentioned, (p. 120,) and the method 

 of pruning to be recommended, will, if 

 adopted, go far to prevent the defect be- 

 ing produced by other means. 



Trees, tvy hound, may be considered as 

 in a sort of imprisonment, and deprived, 

 in some degree, of both bread and water. 

 If we properly undei'stand the manner in 

 which a tree is enlarged annually, and the 

 situation of the principal sap vessels, we 

 shall readily comprehend the nature and 

 extent of the damage done by Ivv. 



The situation of such vessels has been 

 explained, (p. 49 — ^2,) and the annual 

 circles have been mentioned, (p. 85,) but, 

 as some persons still doubt if trees add 

 one more annually, to the circles observed 

 upon their ends, on being cut crosswise, 

 it may here be well to explain how the 

 fact may be demonstrated. — ^The method 

 is this ; take a piece of bark from a free- 

 growing tree, in spring ; say three or four 



