374 



DISEASES OF CULTIVATED PLANTS 



fungi attacking conifers ; it occurs on Finns, Abies, Picea, 

 Ju/iiperus, and Larix. In this country the larch undoubtedly 

 suffers most. This fungus differs from the majority of the 

 polypores in not being a wound-parasite, but a true parasite, 

 the germinating spores entering into the living tissues of the 

 root, where a delicate white sheet of mycelium is formed 



t 











Fig. 115. Fotnes annosus. i, portion of fungus ; 2, sec- 

 tion of same, show ing stratified tubes in three layers ; \. por- 

 tion of hymemum, showing tubes and their openings, slightly 

 mag. 



between the bark and the wood. Soon after the mycelium 

 has extended in the wood the latter changes to a lilac or 

 violet colour, and afterwards to a yellowish brown, and 

 becomes light and spongy. The mycelium simultaneously 

 extends up the trunk and towards the tips of the roots. 

 When the roots have become thoroughly infested with 

 mycelium, flattened, biscuit-like, pure white fruiting bodies or 

 sporophores are produced on the surface of the underground 



