240 ’ 
PRUNING AND THINNING. 
[Part IV. 
The sixteenth annual growth above the branch 
is the last whose descent was checked by the 
dead branch. Its distance from the centre of 
the pith of the stem, measured at the upper edge 
of the board, is four inches one sixteenth. The 
distance of the sixteenth annual growth from 
the centre of the pith below the branch, mea¬ 
sured at the lower edge of the board, is only 
three inches five sixteenths. I imagine that the 
dead branch acted like a ligature, and that, by 
checking the descent of the sap, it caused the 
swelling above it. Below the branch, the 
growths gradually and annually diminish after 
the sixth, which is the time of the death of the 
branch. I have no doubt that the reason of 
this is, that the branch was killed by the prox¬ 
imity of neighbouring trees, and that they at 
the same time killed, and afterwards continued 
to kill, an undue number of side-branches, which 
caused an unduly diminished return of descend¬ 
ing sap, and, consequently, a diminished annual 
ring or growth of timber. So that, notwith¬ 
standing the gradual diminishing after the sixth 
growth, the first fifteen growths of this board 
are nearly three times the size of the next fifteen 
growths; and from after the fifteenth growth 
of this board* the tree was doubtless one of 
