v.] 



DECAY. 



65 



hidden knots are frequently in a state of incipient 

 decay, owing to the rain and the moisture of the 

 atmosphere having entered by the wound, and fostered 

 the development of various rot-fungi, the spores of 

 which were washed in, before it became hermetically 

 sealed ; and, as it generally takes a long time, even 

 many years, to com- 

 pletely heal it over, it 

 would during all that 

 while be steadily pro- 

 ducing decay in the 

 fibres, etc., 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 

 extent, and in bad 

 cases emitting an un- 

 pleasant odour. 



The disease thus 

 occasioned first at- 

 tacks the alburnum, 

 and the wood-tissues 

 immediately sfir- 



rounding the centre of the knot, and then passes down- 

 wards, following the direction of the wounded branch 

 towards the pith of the bole or stem, after which it rises 

 in the various elements conveying 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, 



F 



FIG. 13. 



