238 
PRUNING AND THINNING. 
[Part IV. 
deeply and more firmly imbeds and builds in all 
its predecessors in the stem of the tree. It is 
only such an arrangement as this which would 
support the enormous weight on the enormously 
long levers which wide-spreading branches offer. 
When the growth of the stem had arrived at 
D D, the branch died; that is, when the cen¬ 
tral part of this board below the branch was six 
years old, and when the central part of the 
branch and of the board above it was five years 
old. From D D to E E, during a period of 
eleven years at the upper side of the branch, 
and of twenty-two years at the more projecting 
lower side of it, the dead branch has been gra¬ 
dually and annually inclosed by the growths of 
the stem, forming a disunited knot; that is, 
the branch may be seen to be disunited from 
these growths of the stem. At E E the growths 
of the stem curve over the cut end of the 
branch. After covering the cut end, the growths 
would have again become continuous and straight 
had the board been wide enough to show it. 
Indeed, in Plate II., which is the contrary side 
of the same board and branch, the growth has 
already become continuous. 
If the branch had been cut off close to the 
stem at D D when it died, it would have healed 
