142 HEART-ROT CAUSED BY OTHER FUNGI 



and are usually the entire width of an annual ring. The 

 subsequent stages of rot are somewhat variable. The 

 delignified walls of the white flecks may crumble away, 

 owing to the digestion of the middle lamellae, leaving holes 

 arranged in layers associated with definite annual rings, 

 and if manj^ adjacent annual rings are attacked the wood 

 becomes honeycombed. This is general in the pine and 

 spruce and sometimes occurs in the larch. In the Tamarack 

 {Larix americana) it generally happens that the flecks become 

 joined, first longitudinally and later tangentially, so that 

 entire tangential sheets become rotted and intermediate 

 plates can readily be separated out. In the larch and pine 

 the mycelium is said not to destroy the sap-wood, so that the 

 water-supply of the ujjper part of the tree is not materially 

 reduced ; if a tree is killed by the fungus it is generally 

 through wind-break at the weakened portion. For the 

 same reason fructifications are not borne except on or near 

 the branch stubs. In the spruce and silver fir, which are 

 poorer in resin, the mycelium can penetrate to the cortex, 

 and where this occurs brackets may grow from the bark 

 without any special relation to the branches. 



The only remedial measure is to cut down the trees and 

 destroy infected portions. As the rot is generally confined 

 to the upper portions of nearly mature trees, the lower part 

 of the trunk can be utilized, and it is to the forester's interest 

 to secure this timber at the earliest possible moment, as the 

 longer he leaves the tree the greater will be his loss through 

 the downward spread of the rot. But what is much more 

 important than his own interest is his clear duty to British 

 foresti-y. The fungus is as yet uncommon in Britain, and 

 we should do all in our power to prevent it from spreading. 

 Wherever any sign of its presence becomes apparent, 

 infected trees should bo immediately cut down, and every 

 part of a tree that shows the least trace of rot should be burnt. 

 To remove the brackets and incrustations is not enough, as 

 they grow again even from felled logs in the forest, and it 

 is impossible to maintain a sufficiently careful scrutiny to 

 prevent the dissemination of the fungus. 



