36 
TIMBER AND TIMBER TREES. [chap. 
decay, owing to the rain and the moisture of the 
atmosphere having entered by the wound, before it 
became hermetically sealed ; and, as it generally takes 
a long time, even many years, to completely heal it 
over, it would during all that while be steadily pro¬ 
ducing decay in the fibres, running from the knot to 
the centre of the tree ; the diseased or affected part, 
when opened, being 
often found spread 
to a very great ex¬ 
tent, and in bad cases 
emitting an unplea¬ 
sant odour. 
The disease thus 
occasioned first at¬ 
tacks the alburnum, 
and the fibres imme¬ 
diately surrounding 
the centre of the 
knot, and then passes 
downwards, following 
the direction of the 
wounded branch to¬ 
wards the pith of the 
bole or stem, after 
which it rises with 
the sap, and is often 
communicated to other parts of the tree, and does very 
great mischief. 
It will sometimes happen that this disease is con¬ 
centrated, or confined to the root end of the branch, 
producing there what is technically termed a “druxy 
knot/'’ This defect, if prevented from spreading by 
the otherwise healthy and vigorous state of the tree 
fig. 13 . 
