THE HONEY FUNGUS 155 



up a trunk more quickly than transversely. In this first 

 state of rot the wood is very little affected. 



The black line. The second state of rot is distinguished 

 by black layers in the wood. These layers start from the 

 cambium and gradually spread inwards, remaining very thin 



FIG. 67. Armillaria mellea. Radial longitudinal section of larch wood 

 showing the ' black line ', where it crosses a medullary ray ( x 100). For 

 description, see text. 



all the while, so that in a transverse section of the trunk 

 they appear as lines forming the sides of triangles with tjie 

 cambium as base (fig. 65). They also spread upwards 

 in the wood, forming cone-shaped surfaces, and a section 

 through a somewhat higher part of the trunk shows them 

 as irregular circles. 



A black layer, or black line as it appears in section, is 

 entirely made up of hyphae. For when the rot has reached 

 a certain stage in the wood, the hyphae become much more 

 frequently septate and bear special short branches. Both 



