SHADE TREE AND TIMBER DESTROYING FUNGI. 219 



having healed over. A section of the 

 trunk shows that the heart rot had be- 

 gun. It is in the first stages of 

 the disease and confined to a limited 

 area, that directly at the centre of the 

 heart. There is present here only the 

 discolored area which is characteristic of 

 the other and younger area in older 

 stages of the disease, described above. 

 It is quite likely that the fungus enters 

 at these slow healing wounds where the 

 lower limbs have fallen, and that in some 

 cases the wounds might entirely heal over 

 and imprison the mycelium before the 

 fruit bodies had an opportunity to form. 

 That there was abundant opportunity for 

 the mycelium of the fungus to enter at 

 these wounds is shown by the evidence 

 of a large proportion of the young maple 

 trees in the mixed forest at Clearwater. 

 I have already called attention to the 

 deep shade in the spruce woods where the 

 tall spruces overtop the broad leaved 

 trees, and of the effect which this shade 

 has in checking foliage development on 

 the younger maples. Even on the young 

 and middle aged maples there are com- 

 paratively few branches and these near 

 the top of the tree, the lower branches 

 having died and dropped off. The same 

 can be said of the beeches, birches and 

 other broad leaved trees. Even on these 

 topmost branches there are compara- 

 tively few leaves, because of the low 

 light reaction. This means then that a 

 comparatively small amount of the car- 

 bohydrates necessary in the formation 



78. Ulcers on trunk of 

 mafile. 



