308 



MANUAL OF TREE DISEASES 



bark are invaded by the mycelium and the living tissues are 

 killed. 



Fruiting-bodies of two kinds are formed by the causal fungus. 

 They are sometimes considered as two separate species. One 

 form is distinctly hoof-shaped with a jet-black and ex- 

 tremely checked, charcoal-like upper surface (type of Forms 

 igniarius, Fig. 59), while the other is more shelf-like, with 

 the gray to black upper surface marked with concentric arched 



Fig. 60. — Fruiting-body of Fames igniarius. This form 

 is sometimes called Ftymes nigricans. 



ridges and is slightly checked (type of Forties nigricans, 

 Fig. 60). The under surfaces of both types of fruiting-bodies 

 are identical, being reddish brown and velvety. The open 

 ends of the spore-bearing tubes show as minute circular open- 

 ings, barely visible to the unaided eye. The fruiting-bodies 

 form at branch stubs which have not healed over. A new 

 layer of tubes is added each year and large fruiting-bodies of 

 this fungus have been found which showed eighty layers of 

 tubes. When the fruiting-body is broken, the layer of tubes 

 is seen to be stuffed with white material (Fig. 61). 



