CHAPTER III. 

 DEFECTS OF WOOD. 



IN every stage of their growth trees are liable to mischances, 

 from defects of soil or climate, from accident, or from the attacks 

 of fungi, of insects, or of other animals. Some of these mis- 

 chances have permanent and important effects upon their wood. 

 Although, in healthy surroundings and in the absence of external 

 injury, there is no very definite limit to the longevity of any 

 species of tree, after it has reached maturity a certain deteriora- 

 tion generally shows itself at the centre of the trunk, which will 

 subsequently manifest itself as decay. After felling, shrinkage 

 in the process of drying and the attacks of species of fungi, 

 mostly differing from those that injure growing trees, develop 

 further defects in timber of the very gravest practical import 

 to the consumer. 



The attacks of insects or of fungi upon the leaves of trees, 

 though they may prove fatal to seedlings, have generally in later 

 stages of growth merely the effect of injuring the nutrition of 

 the plant. They may thus diminish the amount of wood formed 

 in the season, and may, therefore, be of first-rate importance to 

 the forester or timber-grower, but do not in general concern the 

 timber-user. 



Cup-shake. When, however, the caterpillars of some moths, 

 such as Tdrtrix mriddna, entirely destroy the young leaves of the 

 Oak in June, though the tree may put out new leaves in July 



