198 TIMBER AND SOME OF ITS DISEASES. [CH.VII. 



quite dry, and are cut into beams and used in building ; 

 but they have spores or young mycelium trapped in 

 the cracks at various places. If, from contact 

 with damp brick-work or other sources of moisture, 

 these dormant spores or mycelia are enabled to spread 

 subsequently, we may have " dry-rot" in the building ; 

 but this " dry-rot " is due to Polyporus vaporarius and 

 not to the well-known Merulius lacrymans. 



There can probably be no question of the advantage 

 of creosoting the ends of such rafters, beams, &c. ; 

 since the creosote will act long enough to enable the 

 timber to dry, if it is ever to dry at all. But the 

 mycelium of Polyporus vaporarius makes its way into 

 the still standing timber of pines and firs ; for it is a 

 wound-parasite, and its mycelium can obtain a hold 

 at places which have been injured by the bites of 

 animals, &c.: it thus happens that this form of " dry- 

 rot " is an extremely dangerous and insidious one, 

 and I have little doubt that it costs our English timber- 

 merchants something, as well as Continental ones. 

 Nor are the above the only kinds of " dry-rot " we 

 know. A disease of pine-wood is caused by Polyporus 

 mollis, which is very similar to the last in many 

 respects, and the suspicion may well gain ground 

 that this important subject has by no means been 

 exhausted yet. 



