148 TIMBER AND SOME OF ITS DISEASES, [chap. 



animals as they pass over and under the spore- 

 bearing mass. 



When the mycelium obtains a hold in the root, it 



Fig. 12. — Piece of root of spruce-fir, with the mycelium of Trametes radkiperda 

 (after Hartig) enlarged about 3 times. The white mycelium spreads in a fan-like 

 manner over the surface beneath the cortex, as seen in the figure where the latter 

 has been lifted and removed {a). Here and there the mycelium bursts through 

 the cortex in the form of white protuberances {b\ to form the fructifications. 



soon spreads between the cortex and the wood, 

 feeding upon, and of course destroying, the cambium. 



