158 THE OAK. 



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 T"h(l<j<li",- /'-/<//./. sliowinir the 

 characteristic markings due to the action of the fungus. (R. Ilartig.) 



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 



