vil.] THE "DRY-ROT" OF TIMBER. 183 



quantities of water 50 to 60 per cent, of its weight at 

 least together with much smaller quantities of nitro- 

 genous and fatty substances and cellulose, and minute 

 but absolutely essential traces of mineral matters, the 

 chief of which are potassium and phosphorus. It is 

 not necessary to dwell at length on the exact quantities 

 of these matters found by analysis, nor to mention 

 a few other bodies of which traces exist in such fungi. 

 The point just now is that all these materials are formed 

 by the fungus at the expense of the substance of the 

 wood, and for a long time there was considerable diffi- 

 culty in understanding how this could come about. 



The first difficulty was that although the " dry-rot 

 fungus " could always be found, and the mycelium 

 was easily transferred from a piece of diseased wood 

 to a piece of healthy wood provided they were in a 

 suitable warm, damp, still atmosphere, no one had as 

 yet succeeded in causing the spores of the Merulius to 

 germinate, or in following the earliest stages of the 

 disease. Up to about the end of the year 1884 it was 

 known that the spores refused to germinate either in 

 water or in decoctions of fruit ; and repeated trials 

 were made, but in vain, to see them actually germinate 

 on damp wood, until two observers, Poleck and 

 Hartig, discovered about the same time the necessary 

 conditions for germination. It should be noted here 



