vi.] AGARICUS MELLEUS. 157 



lengths several feet, for instance. The interest of 

 all this is enhanced when we know that until the last 

 few years these long black cords were supposed to be 

 a peculiar form of fungus, and were known as 

 Rhizomorpha. They are, however, the subterranean 

 vegetative parts (mycelium) of the Agaric we are 

 concerned with, and they can be traced without break 

 of continuity from the base of the toadstool into the 

 soil and tree (Fig. 16). I have several times followed 

 these dark mycelial cords into the timber of old 

 beeches and spruce-fir stumps, but they are also to be 

 found in oaks, plums, various Conifers, and probably 

 may occur in most of our timber-trees if opportunity 

 offers. 



The most important point in this connection is that 

 Agaricus melleus becomes in these cases a true parasite, 

 producing fatal disease in the attacked timber-trees, 

 and, as Hartig has conclusively proved, spreading 

 from one tree to another by means of the rhizomorphs 

 underground. In the summer of 1887 I had an 

 opportunity of witnessing, on a large scale, the 

 damage that can be done to timber by this fungus. 

 Hundreds of spruce-firs with fine tall stems, growing 

 on the hill sides of a valley in the Bavarian Alps, were 

 shown to me as "victims to a kind of rot." In most 

 cases the trees (which at first sight appeared only 





