INJURIOUS INFLUENCES 81 



while the ash and poplar suffer equally from 

 canker and insect pests. At a later stage 

 fungus puts in an appearance, and the tree that 

 three years before was sound and healthy is 

 reduced to a crumbling ruin. The unfortu- 

 nate part is, that little or nothing can be done 

 to stay the evil, the removal of the cause 

 being, in most cases, quite out of the question, 

 while after-treatment of affected trees is worse 

 than useless. 



Planting only suitable trees in such situations 

 has been recommended, but, with a wide 

 experience in this matter, we have come to 

 the conclusion that no tree is for long capable 

 of withstanding such smoke and fumes, par- 

 ticularly when brought in close contact with 

 the evil. The elder probably withstands 

 chemical fumes better than any other tree, and 

 has been largely planted in Newcastle-on-Tyne 

 on that account. 



When the air is still, smoke from tall shafts, 

 by getting spread over a wide area, does less 

 damage to trees than when it is carried for a 

 lengthened period of time in the same direc- 

 tion by the action of the wind. Last spring, 



6 



