356 



DISEASES OF CULTIVATED PLANTS 



wood and the bark, or pass out through the bark and form 

 rhizomorphs on its surface, which in the case of roots pass 

 into the soil. After the death of the tree the shrinkage of 

 the bark affords space for the further development of these 



FlG. 109. Armillaria mellea. 2, section of fungus, a, pileus ; 

 b, gills ; c, ring ; d, black, cordlike strands of mycelium ; 3, 

 basidium, a, accompanied by paraphyses ; 4, portion of tree 

 root with branching strands of mycelium surrounding it ; a, a 

 cluster of young fungi springing from the mycelium ; 5, section 

 from outside to centre of rhizomorph or black strand of my- 

 celium. Figs. 3 and 5 mag. 



strands, which become blackish in colour and form a com- 

 plicated network. Such anastomosing black, cordlike strands, 

 are very frequently seen on removing the loose bark from a dead 

 trunk, and clearly indicate the cause of death. The dark- 



