176 PLANT DISEASES 



colour. As a rule the plants are imbricated or growing in 

 tiers, often almost covering branches, stumps, etc. 



The fungus is exceedingly common as a saprophyte, 

 growing on dead wood ; but Hartig has proved that not 

 unfrequently it acts as a true and very destructive parasite, 

 attacking various broad-leaved trees. 



Being a wound-parasite, the spores germinate first on 

 a wounded surface, the mycelium gradually attacking the 

 sound wood, which it destroys. 



The mycelium is perennial, and, having once gained 

 access to a living tissue, continues to extend until the 

 whole is destroyed. 



The wood attacked becomes pale brown first, afterwards 

 yellowish white. 



The thickening of the cell-walls is first dissolved and 

 used by the fungus, the intercellular plates alone remaining, 

 and even these are eventually dissolved. 



Professor Marshall Ward has quite recently studied this 

 parasite, and added considerably to the previous account 

 given by Hartig ; and has furthermore succeeded in pro- 

 ducing sporophores as pure cultures, commencing with the 

 spore, and passing through all its phases, the first time this 

 has been accomplished for a Basidiomycete. 



Preventive Means. — Wherever the fungus is found 

 growing on living trees it should be cut away, the wound 

 washed with paraffin, or corrosive sublimate in water, and 

 afterwards painted with tar. As already stated, when the 

 mycelium has once entered the living wood it is very difficult 

 to eradicate. I have more than once seen the fruit of the 

 fungus emerge from such wood, and grow on a wound that 

 had been treated with paraffin and afterwards tarred. 



Decayed wood should not be allowed to accumulate, as 



