44& Forestry Quarterly. 



trees, pruning" in the fall leads to browning of the wound, and a 

 retardation of the callusing process. While wounds made in 

 the spring 1906 were in 1908 already closed, those made in the 

 fall of 1905 were mostly still open three years later. The influ- 

 ence of .pruning on the increment of the cross-section area is of 

 special interest. In these investigations six to twenty trees were 

 treated for each season. 



By removing one-half of the crown the average increments 

 were as follows : 



1906. 1907. 



Spring, 372 sq. in. .341sq.m. 



Summer, 108 . 387 



Autumn, 542 .558 



Winter, 806 .682 



1.828 1.968 



Per tree, 450 .491 



By removing one-third of the crown the increments were : 



1906. 1907. 



Spring, 713 .852 



Summer, .713 .698 



Autumn, 883 1.162 



Winter, 729 . 760 



3.038 3.472 



Per tree, 760 .868 



When only dry branches were removed, i. e., when no influence 

 on the rate of growth was of course experienced, the increments 

 were : 



1906. 1907. 



Spring, 1 . 426 1 . 410 



Summer, . 992 2 . 092 



Autumn, 1.937 4-945 



Winter, 1.535 1.085 



5.890 9-532 



Per tree, 1 .472 2.382 



The loss then per tree due to the removal of half of the crown 

 was 1.022 and 1.891 sq. in., or 70 and 80 per cent, respectively 

 in the two years. 



The loss when one-third of the crown was removed was .712 

 and 1.5 14 sq. in., or 48 and 64 per cent, respectively. 



These figures show a very considerable influence of the prun- 



