INJURIOUS INFLUENCES 79 



buildings. Evergreens are more sensitive to 

 an impure atmosphere than deciduous trees, 

 the first sign being a sickly yellow look, 

 followed by discoloration of the leaves and 

 death of the upper branches. 



In the case of sulphuric acid, the leaves of 

 hard-wooded trees assume a mottled appearance, 



Rind gall. 



the spots gradually increasing till the whole 

 tissue of the leaf becomes poisoned. Gradually 

 the tree turns unhealthy, with much dead and 

 dying wood, and finally dies out altogether. 

 The only remedy is removal of the cause, 

 though planting coniferous trees such as the 

 Austrian and Corsican pine, instead of hard- 

 wooded species, in the vicinity of coal mines 

 and chemical works is to be recommended. 



Smoke from electric and other chimneys 

 does much damage to trees and shrubs growing 



