X.] "CANKER^'- THE LARCH DISEASE 213 



even in more favoured valleys experience points to 

 the advantage of mixing it with other trees : large 

 areas of pure larch are planted at enormous usk 

 in the lowlands. 



As to the treatment of trees already diseased, it 

 is possible (when it is worth while) to iemo\e diseased 

 branches from trees of which the trunk and ciown 

 are healthy, but it hardly needs mention that such 

 diseased branches must be burnt at once As regards 

 trees with the stems diseased — in those cases where 

 the patches are large, and much resin is flowing from 

 the wounds, experience points to the advisability 

 of cutting them down. In those cases where the 

 tree is already very large, and the diseased wound 

 but small, it may be expedient to let them alone : 

 theoretically they ought to go, or at any rate the 

 diseased tissues be excised and burnt : but it seems 

 to be proved that such a tree may go on forming 

 timber for many years before the wound will spread 

 far enough to reduce the annual increment below 

 the limits of profit, and we all know the view a 

 practical forester will take of such a case. At the 

 same time, it is the duty of the man of science to 

 point out that even such a tree is a source of danger 

 to its neighbours. 



R 2 



