48 THE ADIRONDACK SPRUCE 
GROWTH IN DIFFERENT PARTS OF A TREE. 
An exceedingly interesting question is the rate of growth in dif- 
ferent parts of the same tree. It must be borne in mind that the 
material for growth is elaborated within the crown from material 
derived from the air and the roots, and that this elaborated sap 
comes down in the inside of the bark. It is not difficult to see that 
within the crown the rate of growth must be more rapid at the 
lower part than near the top, because each branch adds a certain 
amount of material for the growth below which the stem above did 
not have. In general, except close to the ground, the growth falls 
off below the crown. In the case of trees very much suppressed it 
may happen that not enough material for growth is formed in the 
crown to reach the lower part of the stem, and in some cases the 
number of annual rings on the stump will not represent accurately 
the age of the tree, because for some years there may have been no 
growth whatever in the lower part of the stem. This happens, 
however, usually only in the case of dying trees. The width of the 
annual rings is smaller at the lower part of the stem than above, 
even if the same amount of material is brought down, because it 
has to extend over a larger surface. The results of the measure- 
ments taken on about 2,000 Spruces show the largest growth in the 
crown, the smallest at the top of the first log, and a medium growth 
on the stump. Where the trees had an increased growth after 
thinning, the largest growth was at the stump. The fact that the 
increased growth at this part of the stem is out of proportion to 
that above has led some observers to believe that it is not necessary 
for all the food materials to be digested in the crown before they 
can be usedin growth. This theory is the result of the phenome- 
non just mentioned, and of the fact that those roots of a tree which 
are in the richest soil grow to the largest size. In order to present 
more clearly the relation of the rate of growth at the different 
parts of the tree under the new influences of light and space after 
thinning, the following table has been made from fifty-nine trees, 
all of which showed accelerated growth on the stump: 
