208 



PRUNING AND THINNING. 



PT. IV. 



out as the river becomes wider as it receives, each 

 tributary ; and each growth of the branch may be seen 

 to be attached to the stem by an increased, not a 

 decreased base. Besides this increase in bulk of each 

 annual growth of the branch where it joins the stem, 

 each growth in succession more 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 central 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 gradually 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 

 w^ould have again become continuous and straight had 

 the board been wide enough to show it. Indeed, in 

 Plate 11. , 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 over there. 



