v.] TRAMETES RADICIPERDA. 149 



Here it spreads in the form of thin flattened bands, 

 with a silky lustre, making its way up the root to the 

 base of the stem, whence it goes on spreading further 

 up into the trunk (Fig. 12). 



Even if the mycelium confined its ravages to the 

 cambial region, it is obvious, from what was described 

 in Chapters I. and II., that it would be disastrous to 

 the tree ; but its destructive influence extends much 

 further than this. In the first place, it can spread to 

 another root belonging to another tree, if the latter 

 comes in contact in the moist soil with a root already 

 infected ; in the second place, the mycelium sends 

 fine filaments in all directions into the wood itself, and 

 the destructive action of these filaments called hyphae 

 soon reduces the timber, for several yards up the 

 trunk, to a rotting, useless mass. After thus destroy- 

 ing the roots and lower parts of the tree, the mycel- 

 ium may then begin to break through the dead bark, 

 and again form the fructifications referred to. 



Since, as we shall see, Trametes radiciperda is not 

 the only fungus which brings about the destruction of 

 standing timber from the roots upwards, it may be 

 well to see what characters enable us to distinguish 

 the disease thus induced, in the absence of the 

 fructification. 



The most obvious external symptoms of the disease 



