THE HONEY FUNGUS 157 
are delignified from the outside towards the middle lamella, 
leaving a layer of cellulose. Then the cellulose also is 
digested so that often whole walls disappear. The walls of 
the bordered pits are digested gradually and they often 
Fic. 68.—Armillaria mellea. Transverse section of larch wood showing 
the ‘ black line’ ( x 450). 
crack through shrinkage in the process, and present various 
curious figures, some of which Hartig has drawn (1879). 
The wood never becomes honeycombed as it does with 
Fomes annosus or as crumbly as with Polyporus Schweinitzit, 
but it is much too weak to be of any use for structural 
purposes. 
The significance of the black line is obscure. It seems 
