vi.] EXCRESCENCES. 35 
character, but are nevertheless the early or first stage of 
incipient decay, and will be found less able to resist the 
action of water than the wood of the same log which 
is untainted. Although these spots can hardly be 
reckoned as defects, seeing that they do not penetrate 
deeply enough to affect in any appreciable degree the 
value of the timber, the surveyor would do well not to 
employ such logs in architectural works where it would 
be difficult to replace the piece should it at any time be 
found to be decayed. 
A swelling upon the exterior of a tree is generally a 
sign of some defect being hidden beneath ; it may be 
confined to the alburnum, but it may also conceal a 
serious fault that would be highly detrimental to its 
value. 
The excrescence should, therefore, be removed as soon 
as the tree is felled, in order to clear up the existing 
doubt. There are, however, some few exceptions to 
this ; for instance,*the burrs which are found upon the 
Oaks of some districts,* and the Austrian and Turkey 
Walnut tree burrs, which are. very finely mottled an 
figured, make good veneers, and have of themselves a 
special value for cabinet purposes. 
The removal of a branch of moderate size from a 
tree, close down upon the stem, will generally be con- 
cealed by a swelling of the kind first mentioned, 
particularly if it has been done while the tree was in 
a healthy state and annually forming new wood. Such 
hidden knots are frequently in a state of incipient 
* These peculiar excrescences are supposed to be caused by punctura- 
tions of the bark by insects, while the tree is growing ; but, so far as I am 
aware, the quality of the trunk of the tree is not often affected by it.— Vide 
Description of the Walaut Tree, page 111. 
