FUNGOID PESTS OF TIMBER 145 



Polyporus sulphureus, as its name implies, is 

 of a yellow colour, bright yellow below and 

 orange or almost red above. It grows at right 

 angles from the stem of its host in a series of 

 tiers or steps. AVhen young it is soft and cheesy, 

 but with age it becomes harder and woody. 

 The spores are borne in the countless pores with 

 which the lower surfaces of the brackets are 

 perforated. So much for the spore-bearing 

 organs of this destructive parasite. Let us 

 follow the fortunes of one of the spores from the 

 brackets of this fungus. Light as air the spore 

 is carried on the slightest breeze. Should it 

 ahght on a tree wound sufficiently severe to 

 have penetrated the bark it will germinate and 

 send out a long fine filament, the first stage of 

 its vegetative growth. This filament branches 

 rapidly and spreads through the tissues of its 

 host, especially in the medullary rays. Decay 

 sets in at once, and the wood soon assumes the 

 appearance of red-brown charcoal, hence its 

 American popular name. Later, the decayed 

 portions crack, and within the cracks may be 

 found the dense felt-Hke mycelium of the 

 causative fungus. " The ultimate filaments of 

 the fungus penetrate the walls of all the cells 

 and vessels, dissolve and destroy the starch in 

 the medullary rays and convert the hgnified 

 walls of the wood elements back again into 



