FALSE TINDER FUNGUS 189 



stage of attack, and afterwards white, or with a shght tinge 

 of yellow, and quite soft. The inner layers of the walls of 

 the cells are first absorbed by the mycelium, the middle 

 lamellae being afterwards converted into cellulose and 

 used as food by the fungus. In this way the whole of the 

 heart-wood is absorbed. 



Preventive Means. — The parasite gains an entrance 

 into the host through wounds, broken branches, holes 

 made by woodpeckers, etc. If the sporophores are cut 

 out on their first appearance, and the wounds protected by 

 tar, the life of the tree may be considerably prolonged ; but 

 it must be remembered that the mycelium having gained 

 access to the living tissues of the host, it continues to 

 spread, and the most certain method is to reduce the possi- 

 bility of infection to a minimum by destroying the fungus 

 wherever and whenever it appears, and also to remove old 

 and useless trees, which favour its growth. 



Hartig, ZersetzKngserscheinwigen des Holzes, p. 114, 

 pi. XV. and xvi. 



Prillieux, Malad. des Plantes Agric, vol. i. p. 359. 



BIRCH POLYPORUS 



{^Polyporus hetulinus^ Fries.) 



This fungus is unfortunately too common on the trunks 

 of birch trees, and has such marked features that it cannot 

 be confounded with any other species. The general shape 

 is that of a horse's hoof. The upper surface is perfectly 

 smooth, white, or often brownish, the brown skin often 

 cracking and peeling off. The margin is thick and in- 



