158 



THE OAK 



the wood by excreting soluble ferments which dissolve 

 the substance of their walls, and feed on the products of 

 solution. Hence they damage the timber in two ways 

 they riddle it through and through by myriads of 

 minute apertures, and thus ruin its structure, and they 



FIG. 42. Piece of oak destroyed by Thelephora Perdix, 

 showing the characteristic markings due to the action 

 of the fungus. (R. Hartig.) 



reduce its substance by dissolving it and converting it 

 to their own uses. The wood, therefore, loses in strength 

 and in weight, and becomes ' rotten.' There are differ- 

 ences in detail as to the mode of destroying the elements 

 of the wood, but the final result is much the same, in all 



