Part IV.] 
PRUNING AND THINNING. 
241 
those denuded poles of which the growth of our 
unthinned plantations in general consists. But 
if room is given for these poles to increase the 
size of their heads, they will in the same propor¬ 
tion increase the size of their annual rings of 
timber. 
The centre of the lower part of the tree was, 
doubtless, much older than any part of this 
board. I imagine that the sort of wavy cross¬ 
grain, which may be observed along the upper 
edge of all branches which are cut like this spe¬ 
cimen, to be the result of the mechanical diffi¬ 
culty which the new growth has to raise and 
eject the bark from the acute angle formed by 
the upper side of the branch and the stem. 
The wavy cross-grain ceases when the bark 
ceases to be raised. 
Plate II. shows the contrary side of the board. 
Owing to the distance from the pith at which 
the saw has passed, the growths of the branch 
are not visible on this side, as they are in 
Plate I. 
On the left, the fifth annual growth of the 
younger shoot of the stem above the branch, 
joins the beginning of the upper side of the 
branch ; the sixth annual growth of the older 
shoot of the stem below the branch, joins the 
R 
