Chap. IV.] 
MISCELLANEOUS. 
137 
the gardeners say, callous over immediately. 
These callouses are a prolific source of new 
shoots for the root, which besides, from having 
been shortened, makes a profusion of lateral 
shoots that same season. These shoots become 
woody, and the root is consequently in a state 
to supply the great upward demand next spring. 
We may convince ourselves by experiment, 
that the downward is after the upward growth 
of trees. If notches are cut on the stem of a 
tree from the root to the setting on of the first 
branches, the new growth over the scars will be 
when the tree is ceasing to shoot. The upper 
notches will heal first, in the form of a horse¬ 
shoe, with the heels downwards; that is, the 
growth will be on the upper part and the sides of 
the notches, without any growth from the lower 
parts of the notches. This fact also strongly 
corroborates the opinion that the new growth in 
girthing is from the downward sap ; for if it 
were a side-deposit from the upward sap, the 
lowest notches should heal first, and the healing 
would be from their lower sides. I have found 
that, if stems thus notched are inverted, the new 
growth comes only from the sides, of the notches, 
and neither from the upper nor lower parts of 
them, which I am unable to account for. But 
