66 



The mycelium of the fungus almost always produces a very 

 characteristic mottled fan-like appearance in the bark, and ap- 

 pears to penetrate through the tissues of the bark but a short 

 distance, if at all, beyond this discolored area. The mycelium 

 also penetrates the sap wood very freely, when the disease reaches 

 as deep as the wood, as it generally does sooner or later; but, 

 unlike its effect in the bark, no pronounced discoloration is pro- 

 duced in the wood, and it is impossible to determine with the 

 unaided eye the approximate limits of the mycelium, as in the 

 case of the bark. 



In all efforts to control the disease without destroying the 

 tree, it is of course necessary to gouge out this disease infected 

 sapwood. The depth to which it is necessary to remove it can- 

 not at present be definitely stated, as insufficient time has 

 elapsed to demonstrate this point experimentally. Many cut- 

 tings, some with the sapwood partially removed from beneath 

 a lesion, and others with all of it removed, are now being watched 

 for results. IIoAvever, in a diseased spot from (hree to four 

 inches in diameter apparently at least three annual layers of 

 , wood in the centre of the diseased spot must be removed. 



Of course where sapAvood is cut, enormous numbers of minute 

 tubes, which conduct the crude sap from the roots through the 

 trunk and branches to the leaves, are severed, and, should the 

 cutting happen to have been done during warm, dry weather, 

 it often happens that one or more branches directly above the 

 cut-out area will show much wilted leaves within an hour or 

 two. This is a direct and inevitable result of the suppression, 

 from any cause whatsoever, of a considerable portion of the sup- 

 ply of water for the leaves. 



Considerable careful judgment may at times have to be used 

 when making cuts of this nature, and occasionally it may be 

 wise to remove one or more healthy limbs, or perhaps to strip the 

 foliage partially from a branch situated just above a place where 

 much sapwood has been removed. This will at least tend to pre- 

 vent wilting, which if excessive, may result in the subsequent 

 death of the branch. 



(3). Preservation of exposed wood from decay. 



If exposed surfaces of wood are left with no protective cover- 

 ing they soon become weathered, dried, checked, and easily in- 

 fected with fungi, causing decay of the wood. In the chestnut, 



