414 



PROTECTION AGAINST PLANTS. 



generally swells owing to a supply of carbohydrates being 

 absorbed by it, produced partly by the mistletoe. Where only a 

 branch is attacked, the damage done to forest trees is not worth 

 mention, but when this extends to the stem, the wood becomes 

 technically injured, being no longer suitable for timber, and is 

 liable to be broken by the wind. 



Fig. 201. Silver-fir (w) attacked by mistletoe (m). 



() Annual shoot (b) opposite leaves of latter. 



(Natural size.) 



Fig. 202. Silver-fir 

 wood perforated by 

 mistletoe, the haus- 

 toria of which have 

 been absorbed. 



Extensive damage is thus sometimes done in old Scots pine 

 and silver-fir forests, owing to neglect in removing infected 

 trees in the thinnings ; nearly every tree in a compartment 

 may then be attacked by mistletoe. 



As a remedial measure, pruning off the mistletoe is useless, 

 for the cortical root sends out new shoots, which break 

 through the bark of the host and develop into new plants. 

 The only effective plan is to prune off the whole infected branch 



