188 TIMBER AND SOME OF ITS DISEASES. [CHAP. 



was discovered by Hartig : the older parts of the hyphae 

 pass their protoplasmic contents on to the younger 

 growing portions, and so economize the nitrogenoi 

 substances. Other food-substances are not so sparse 

 the lignified walls inclose water and air, and contaii 

 mineral salts, and such organic substances as coniferii 

 tannin, &c., and some of these are absorbed an< 

 employed by the fungus. Coniferin especially appeal 

 to be destroyed by the hyphae. 



The structure of the walls of the tracheides an< 

 cells of the wood is completely destroyed as th( 

 fungus hyphae extract the minerals, cellulose, am 

 other substances from them. The minerals ai 

 absorbed at points of contact between the hyphse an< 

 the walls, reminding us of the action of roots on 

 marble plate : the coniferin and other organi< 

 substances are no doubt first rendered soluble by 

 ferment, and then absorbed by the hyphse. This 

 excretion of ferment has nothing to do with the 

 excretion of water in the liquid state, which gives the 

 fungus its specific name : the " tears " themselves have 

 no solvent action on wood. 



It will be evident from what has been stated that 

 the practical application of botanical knowledge is 

 here not only possible, but much easier than is the 

 case in dealing with many other diseases. 



