440 PROTECTION AGAINST FUNGI. 



in causing red or white rot in standing trees, the origin of 

 which may, however, be due to certain bad conditions of 

 the soil (pp. 673 and 679). 



In the case of red rot, the substance of the cell-wall is 

 dissolved by a ferment contained in the protoplasm of the 

 hyphae of the fungi, and a residual substance consisting of 

 gum, tannin, mineral matter, etc., remains, which, owing to 

 the oxidation of the tannin, assumes a reddish-brown colour. 



Red Rot is caused by the following fungi : 



a. Polyporus vaporarius, Fr. 



On spruce and Scots pine, and rarely on silver-fir, both 

 roots and wounds above ground being attacked. Wood 

 attacked by this fungus becomes dark-reddish brown, and full 

 of rectangular cracks, as in the case of Merulius lacrimans, Fr., 

 which causes dry rot in timber. When rubbed between the 

 fingers, the rotting wood falls as a yellowish dust. Snow- 

 white branching mycelia, several yards long, are formed ; the 

 sporocarps form white incrustations. The spores gain entrance 

 to the trees through wounds, and the fungus is also common 

 on beams in buildings. 



I. Polyporus Schtveinitzii, Hrtz. 



This is termed P. mollis, Pers., by Hess, but Hartig has 

 now given the correct name as above. It is found on Scots 

 pine, and also Weymouth pine and larch. Kesembles (a), but 

 no white branching mycelia occur. Sporocarps reddish -brown 

 brackets. 



c. Polyporus sulphureus, Fr. 



On the larch and silver-fir ; it is also a very common parasite 

 on several broadleaved trees, and will be described further on. 



White llot is produced when the ferment of the hyphae 

 decompose the lignine of the cell-walls, leaving the white 

 cellulose untouched, which accounts for the light colour of the 

 decomposed wood. Some of the causes of white rot are the 

 following : 



(d) Polyporus borealis, Fr. On the spruce ; the wood turns 

 brownish-yellow, and characteristic radial grooves appear in 



