TREE ROOT ROT 201 



white mycelium at the margin gradually encroaches on the 

 surrounding parts, being especially favoured by a damp, 

 stuffy locality. 



Hartig, Der dchte Hausschwamm (Merulius lacrymans), 

 1885. 



Hartig and Somerville, Diseases of Trees, p. 212. 



AGARICACEAE 



TREE ROOT ROT 

 (Armillaria mellea, Vahl.) 



This very destructive fungus is probably the commonest 

 and most generally distributed of British 'toadstools.' 

 In addition to attacking nearly all kinds of orchard trees, 

 it destroys various species of forest trees, including 

 conifers. 



The fungus commonly grows in dense clusters round 

 the roots of growing trees ; it also frequently occurs on 

 dead stumps and trunks. Sometimes it appears to be 

 growing in the naked ground, but in such instances it 

 originates from buried wood, roots, etc. 



The cap or pileus is two to three inches across when 

 expanded, of a pale honey-yellow or wax-yellow colour, 

 and is generally ornamented with minute, darker scales ; 

 the stem is three to six inches long, smooth, and coloured 

 like the cap, often deeper honey-colour near the base ; the 

 gills are white when young, becoming cream-colour, and 

 during the young stage are hidden by a membrane stretch- 

 ing from the stem to the edge of the cap; as the cap 

 expands, this membrane breaks away from its edge, and 



