vi.] AGARICUS MELLEUS. 161 



name rhizomorph. The presence of the rhizomorphs 

 and (in the case of the resinous pines) the outflow of 

 resin and sticking together of soil and roots are good 

 distinctive features. No less evident are the differences 

 to be found on examining the diseased timber, as 

 exemplified by Prof. Hartig's magnificent specimens. 

 The wood attacked assumes brown and bright yellow 

 colours, and is marked by sharp brown or nearly black 

 lines, bounding areas of one colour and separating 

 them from areas of another colour. In some cases 

 the yellow colour is quite bright canary yellow, or 

 nearly so. The white areas scattered in this yellow 

 matrix have no black specks in them, and can thus be 

 distinguished from those due to the Trametes. In 

 advanced stages the purple-black rhizomorphs will be 

 found in the soft, spongy wood. 



The great danger of Agaricus melleus is its power 

 of extending itself beneath the soil by means of the 

 spreading rhizomorphs : these are known to reach 

 lengths of several feet, and to pass from root to root, 

 keeping a more or less horizontal course at a depth of 

 6 or 8 inches or so in the ground. On reaching the 

 root of another tree, the tips of the branched rhizo- 

 morph penetrate the living cortex, and grow forward 

 in the plane of the cambium, sending off smaller 

 ramifications into the medullary rays and (in the case 



M 



