218 
PRUNING AND THINNING. 
[Part IV. 
Example. 
rate the whole sap sent up by the root, the whole 
tree receives a check, not only in the increase of 
bulk in girthing, but in the growth of the root, 
on account of the diminished supply of elabo¬ 
rated descending sap. Thus bad pruning may 
diminish the quantity of timber grown ; but I 
can by no means concur in Loudon’s idea that 
pruning, by increasing the quantity of timber, 
deteriorates its quality. No pruning increases 
the quantity of wood made by a tree, but only 
alters the location of it ; but the actual bulk 
of all the side-branches which are gradually 
taken off, or rather the bulk to which all those 
branches collectively would have attained, may 
be considered as laid on to that part of the stem 
which is above them, without detracting from 
the bulk of that part of the stem which is below 
them. This is the great merit which good 
pruning lays claim to. 
Suppose a nursery plant with two equal 
leaders; both are weak in comparison to the 
stem below, because each has only half the sap 
which ascends through the stem, and also each 
has only its own descending sap, while the de¬ 
scending sap of both deposits on the stem below. 
If one leader is taken off, new vigour is given to 
the other. The growth which would have been 
