144 TIMBERS AND THEIR USES 



Erysiphm, which are common on the leaves of 

 Oak, Beech, Ash and Birch, though their myceha 

 are situated on the surface of their hosts, require 

 nourishment, and this they obtain by sending 

 down little root-hke organs into the tissues over 

 which they spread. 



Fungi causing direct injury to living 

 TREES. Wound fungi. The parasites which we 

 are about to consider are called wound parasites, 

 for the reason that they always gain admittance 

 to the healthy timber through wounds in the 

 bark. Such wounds may be caused in number- 

 less ways : by insect damage ; by bad pruning 

 of the branches and accidental injury ; by the 

 gnawing of rodents, rabbits and the like, and 

 even by shot-holes in certain cases. 



Among the commonest of these wound para- 

 sites are the bracket fungi. Several species may 

 be met with in the course of a short ramble, for 

 they abound everywhere. Polyporus sulphureus 

 attacks Oak, Poplar, Pear, Hazel, WiUow, Larch, 

 Walnut, Chestnut, Alder, Apple, Cherry, Maple 

 and the conifers generally. In America this 

 parasite is known as Red Heart Rot. 



Polyporus fulvus attacks conifers, as does P. 

 borealis ; on Oak we commonly find P. ignarius 

 and P. dryadens ; whilst P. vaporariics is now 

 commonly met with on the wood of felled 

 conifers. 



