HEART-ROT 99 
If the rotted wood remains wet (and it is often saturated 
with water), it may become sodden and still more decom- 
posed. It is very probable that bacteria assist in this final 
stage, and the large amount of cellulose present would be 
suited to bacterial action if cnough moisture were present. 
The mycelium grows up the trunks much more rapidly 
than it spreads transversely, since the gum layer limits 
lateralexpansion. The affected part of the wood may be less 
than half an inch in diameter, but up to 4 or 5 ft. in 
length. If the rotted portion could be dissected out it would 
then appear as a long spike. Later the fungus grows up 
from other basal points, making fresh spikes, and when 
a number of these are cut across in a transverse section, 
a beautiful pattern is often produced. Fig. 36 is a photo. 
graph of such a section, cut somewhat obliquely with an 
axe. Jn the rotted portions the white cellulose patches can 
be seen, and the dark gum layers round the individual 
‘ spikes ’ of rotted wood are also visible. Another common 
type of rot is shown in fig. 31. Here an annular portion 
is rotted and a central peg of sound wood remains, which 
is of course protected by a layer of insoluble gum. This 
central peg is often present, and may be no thicker than 
a pencil, though as much as 5 ft. long. 
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