DECAYS AND DISCOLORATIONS IN AIRPLANE WOODS. 43 
The discolorations resulting from incipient decay may be found 
in the sapwood or heartwood. Incipient decay extends for varying 
distances beyond the typical decay. In cutting out this defect it is 
advisable to leave a margin of safety of at least 2 feet in a longi- 
tudinal direction beyond the last visible evidences of the incipient 
decay, in order to remove all infected wood. This margin of safety 
is particularly important with brown or red-brown friable decays, 
since infected wood may be dangerously weakened by them while the 
incipient stage is still practically invisible. 
Many decays other than those described in this paper are found 
in living trees, in logs, and in manufactured timber, but the examples 
cited include both the most important decays and the principal types. 
For most purposes it is sufficient to recognize incipient decay as 
distinguished from other discolorations or defects without deter- 
mining the causal fungus. 
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