374 



DISEASES OF CULTIVATED PLANTS 



fungi attacking conifers; it occurs on Pinus, Abies, Picta, 

 Juniperus, 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 



FIG. 115. Fames annosus. i, portion of fungus; 2, sec- 

 tion of same, showing stratified tubes in three layers ; 3, por- 

 tion of hymenium, 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 



