i88 TIMBER AND SOME OF ITS DISEASES, [chap. 



was discovered by Hartig : the older parts of the hyph^e 

 pass their protoplasmic contents on to the younger 

 growing portions, and so economize the nitrogenous 

 substances. Other food-substances are not so sparse ; 

 the lignified walls inclose water and air, and contain 

 mineral salts, and such organic substances as coniferin, 

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

 employed by the fungus. Coniferin especially appears 

 to be destroyed by the hyphse. 



The structure of the walls of the ti'acheides and 

 cells of the wood is completely destroyed as the 

 fungus hyphse extract the minerals, cellulose, and 

 other substances from them. The minerals are 

 absorbed at points of contact between the hyphae and 

 the walls, reminding us of the action of roots on a 

 marble plate : the coniferin and other organic 

 substances are no doubt first rendered soluble by a 

 ferment, and then absorbed by the hyph^. This 

 excretion of ferment has nothing to do with the 

 excretion of water in the Hquid 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. 



