198 DISEASES OF TREES 



POLYPORUS VAPORARIUS- 1 * 



The decomposition produced by this and the following parasite, 

 P. Schweinitzii, bears a very strong resemblance to that caused 

 by the dry-rot fungus Merulius lacrymans. 



P. vaporarius is exceedingly common on spruces and pines, 

 both roots and wounds above ground being attacked. It very 

 frequently effects an entrance through a wound due to the 

 barking of red deer. The wood becomes reddish brown, dry, 

 and fissured, and as time goes on the resemblance to half- 

 charred timber becomes more and more apparent. When rubbed 

 between the fingers it crumbles into yellow dust. The my- 

 celium is specially liable to develop in cracks, or between 

 the dead wood and the bark, in the form of snow-white 

 much-branched woolly felted strands, similar to many of the 

 mycelial growths of Merulius lacrymans. Although I have 

 made no direct observations on the point, still I think it prob- 

 able that the mycelial strands which grow on dead roots and 

 stools may convey the disease subterraneously to adjoining trees. 

 The sporophores, which are pure white, form incrustations, 

 but never brackets. These originate on decayed wood or 

 dead bark, or on luxuriant mycelial growths or strands. This 

 fungus very frequently appears on the timber of buildings 

 where, on account of its luxuriant mycelial growths, which 

 have sometimes a fasciated, sometimes a strand-like appear- 

 ance, it is usually confounded with Merulius lacrymans^ whose 

 mycelial growths, however, always assume an ashy grey colour 

 shortly after being formed. As regards its importance as an 

 agent in inducing decay in buildings, I may refer to the remarks 

 which I shall have to offer when discussing M. lacrymans. 



POLYPORUS SCHWEINITZII f 



In describing this parasite in ZersetzungserscJieinungen des 

 Holzes* I have called it Polyporus mollis. This mistake was 



1 R. Hartig, Zersetzitngserscheinungen, pp. 45 et seq., and Table VIII. 



2 P. 49- 



* [Very common on dead wood, and I have found it on the decayed wood 

 of a green-house. ED.] 

 t [Quoted as British. ED.] 



