90 FORESTRY 



and a gap in the forest crop results. This gap always tends 

 to .increase in size owing to surrounding healthy trees being 

 contaminated by the diseased ones. The roots become com- 

 pletejy decayed. Under the bark scales at the " collar " of 

 the tree the delicate white mycelium may be seen, and there 

 often below a mossy covering the snow-white polyporous 

 fructifications are borne. The latter also appear upon diseased 

 roots that have been laid bare ; the spores from them are 

 apt to be distributed upon the fur of rabbits and other 

 burrowing animals, thus starting new centres of infection. 



In North Germany it is found that Scots Pine upon land 

 previously under tillage seldom escapes the ravages of this 

 fungus. In this country also the pest is of very frequent 

 occurrence. 



Trametes pirn produces a form of " ring-shake " and de- 

 composition of the wood. As its specific name implies, the 

 fungus assails Pines principally ; but it is not confined to them 

 Spruce, Larch, and Silver Fir also being subject to its 

 attack. The oldest class of trees are the chief sufferers, 

 and those under forty or fifty years old are practically free 

 from it. It is a "wound-parasite," i.e. it can effect an entrance 

 only through a wound or abrasion, such as that left by a 

 broken branch, which exposes the unprotected wood. In the 

 case of the Pine, it is only at those parts on the stem where 

 dead branches have left a way through the sap-wood that 

 the woody, bracket-like fructifications make their appearance. 

 In the heart-wood the mycelium delights to spread circularly 

 in an annual ring, causing the separation known as ring- or 

 cup-shake. But it may break down the woody tissue through- 

 out the whole duramen, spreading both upward and downward 

 in the stem from the place of entrance. 



Prevention : As the fungus is distributed only by spores, 

 felling the infected trees puts an end to the trouble, and also 

 saves further deterioration of the timber. The breaking or 

 pruning away of green branches should be avoided, as wounds 

 thus caused provide the necessary germinating bed for the 

 spores. If artificial pruning be necessary, the larger wound 



