THE WOOD 



231 



If kept dry or if kept under water, wood does not 

 decay. Charring the wood gives it a wrapper of charcoal, 

 which the fungus cannot pene- 

 trate ; painting and whitewashing 

 do the same. But if painted before 

 dry, the paint does harm by pre- 

 venting the timber from drying. 



Salts of zinc, copper, and mer- 

 cury, and heavy oils are used to 



FIG. 87 



FIG. 87. "Shelf" Fungus on the 

 Stem of a Pine 



a, sound wood; 6, resinous "light" 

 wood ; c, partly decayed wood or 

 punk ; d, layer of living spore tubes ; 

 e, old filled-up spore tubes ; /, fluted 

 upper surface of the fruiting body 

 of the fungus, which gets its food 

 through a great number of fine 

 threads (the mycelium), its vegeta- 

 tive tissue penetrating the wood and 

 causing its decay. (After Hartig) 



FIG. 88. Fungus Threads in Pine 

 Wood 



a, cell wall of the wood fibers; 6, 

 bordered pits of these fibers ; c, 

 thread of mycelium of the fungus; 

 d, holes in the cell walls made by the 

 fungus threads, which gradually dis- 

 solve the walls as shown at e, and 

 thus break down the wood structure. 

 (After Hartig) 



