CHAPTER XIIL 



DURABILITY OF WOOD. 



Decay in Wood is due to the breaking down of the tissues 

 by fungi. In some cases the fungus destroys the woody cells;, 

 in others it uses upMhe starch found in the cells and merely leaves 

 a blue stain (bluing of lumber). Some kinds of fungi attack 

 only conifers, others only hard woods; some are confined to one 

 species while others may affect several species, but probably no 

 one of them attacks all kinds of wood. Figure 46 shows the dis- 

 coloration of wood by a shelf fungus. The wood contains the 

 fungus plant, which, when ready to produce its spores, sends out 

 a shelf-like body on the side of the wood. These shelves contain 



the spores and may be found 

 on many old decayed trees or 

 stumps. Various odors are 

 produced in the wood by some 

 of these fungi; they may be 

 pleasant, as those found some- 

 times in the Oak, or unpleas- 

 ant, as those infesting some 

 of the Poplars. By studying 

 both the favorable and the 

 unfavorable conditions for the 

 growth of the rot-producing 

 fungi we may learn the best 

 methods of increasing the 

 durability of our woods, and 

 thus avoid unnecessary waste. 

 The soil and conditions 

 under which wood is grown 

 affect its durability. Conifer- 



Figure 46. "Shelf" fungus on 

 the stem of a Pine (Hartig). 

 (a) Sound wood; (b) resinous wood; 



(c) partly decayed wood or punk; 



(d) layer of living spore tubes; 



(e) old spore tubes filled up; 



(/) fluted upper surface of the fruit- 



ous woods with narrow annual 

 rings are most durable, espe- 

 cially when grown on compar- 

 atively poor soils, in dense 

 forests, and at high altitudes. On the contrary, the hard woods 



ing body of the fungus which gets 

 its food through a .great number of 

 fine threads (the mycelium), its 

 vegetative tissues penetrating the 

 wood and causing it to decay. 



