10 
The process of covering a knot or the stub of a broken or sawed- 
off limb is similar in every particular to that just described. Here, 
too, a callus, most extensive on the sides and least on the lower side 
of the knot, covers the stub and, as in the blaze, enters faithfully 
atime oe Se LN 3S 
Bast’ 20 25 17 30 32 35 40 43 
Fig. 11.—Blaze twenty-three years after cut was made, the later annual rings having assumed 
the normal growth over the wound: cross section. 
into all depressions. Where the knot decays a cavity, of course, 
is formed behind the callus (see fig. 12), though such a cavity may 
not exist when the wound first covered. 
It is evident from what has been said, that the chip covering the 
. blaze itself does not furnish 
information as to what time a 
blaze was made in a given 
tree, since here all rings are 
not necessarily represented. 
To find how many years ago 
the cut was made, it is neces- 
sary to have a cross section of 
the stem, or at least a part of 
a cross section lying on both 
sides of the line A B, fig. 11. 
Then the number of rings 
may be counted from bark to 
pith and the particular ring 
leading to the edge of the 
oak wood: a, wood of the knot; b and c, wood F Bian 
callus of the stem covering the wound; shaded wound (ring No. 20 in figs. 6, 
portion, decayed wood; black part, a cavity fs 9, and 11) may be traced 
remaining. : 
from the wound to the radius 
along which the counting is done. 
Where the wood is decayed below the covering callus, this latter 
is commonly intact, and the innermost ring of the callus becomes the 
starting point. If the cut is made in winter, this innermost ring is 
