203 



PLANT DISEASES 



forms a frill or ring round the stem ; the spores are white, 

 and are produced in great profusion, settling on objects 

 near in the form of a dense white powder. 







Fig. 47. Armillaria mellea. Group of plants about one-quarter 

 nat. size. 



The roots of trees are attacked first, the mycelium of the 

 fungus gradually passing up into the base of the trunk. 

 The wood is not penetrated to any great depth ; but as the 



