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 
Fie. 67.—Armillaria mellea. Radial longitudinal section of larch wood 
showing the ‘ black line ’, where it crosses a medullary ray (x00). 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 the 
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 
