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AN INQUIRY INTO THE CAUSES OF THE DEATH OF 



striking example of this difference of colour. It also shows how 

 far the disease has travelled below the fork. Some of the 

 microscope sections show a dark coloured substance in the cells 

 of the medullary rays and also in the wood ducts. In the bark 

 of the specimens with dark-coloured wood, a micro-fungus is 

 always present : and if the wood is discoloured on one side only, 

 the fungus is always on the discoloured side, while the bark on 



Figs. 4 and 5. Sections of a branc.i showin.; discoloured, diseased wood and 



broken bark. 



the other side is quite normal. On the branches of all the trees 

 that I have examined, the fungus known as Melanconis stilhostotna. 

 Tub, has been found. There appears little on the face of this, 

 for the fungus has long been known to be quite common on dead 

 branches of Betula alba. Between the cortex and wood of the 



