78 TREE WOUNDS AND DISEASES 



and extension to separate. Both star- and cup- 

 shake occur in perfectly sound and healthy trees, 

 and their presence cannot be detected till the 

 tree is felled. Usually cup-shake is local, and 

 on sandy soil on the Woburn estate, in Bedford- 

 shire, the Spanish chestnut trees over certain 

 defined areas were badly affected, and the 

 timber rendered quite useless for constructive 

 purposes. The timber of the Scotch and other 

 species of pines, particularly when attacked by 

 fungus, is apt to suffer from star- or cup-shake. 



Twisted fibre is common in the sweet or 

 Spanish chestnut, oak, sycamore, horse-chest- 

 nut, and other trees. The twist usually goes 

 from left to right, and renders the timber of 

 trees that are so affected comparatively worth- 

 less for converting. 



Rind galls are surface wounds that form 

 blemishes in the timber, which becomes dis- 

 united from the older wood. 



Atmospheric impurities arc frequently the 

 direct cause of the death of trees. The injury 

 is most often due to sulphurous acid contained 

 in smoke, the emanations of smelting and 

 chemical works, coal mines, factories, or town 



