872 
Journal of Agricultural Research 
Vol. XXI, No. n 
of the inhibiting substance, which, in turn, tends to keep the buds 
below them dormant. The successively smaller size—diminishing 
length— of the lower shoots appears to be due to the effect of the growth- 
inhibiting substance produced in those above, an effect to which each 
shoot contributes, with the result that the lowest buds are entirely 
prevented from developing. 
We may proceed to examine the plausibility of these theories as applied 
to the formation of laterals. On the supposition that a reduction in the 
length of the mother shoots so reduces the demands on the resources at 
the disposal of the tree that each growing point acquires a larger supply 
of these resources we should expect that the shorter mother shoots would 
produce more lateral growth than the longer mother shoots. Reference 
to the total lateral growth of the different mother shoots shows that this 
was not the case. If any difference existed it was in favor of the longer 
mother shoots. If we compare two classes of mother shoots originally 
possessing approximately the same number of buds, one of which was 
pruned and the other unpruned, we shall see that the pruned mother 
shoots produced considerably more total growth than the unpruned. A 
possible objection to this comparison may be mentioned—the shoots 
which were pruned were constitutionally more vigorous, because after 
removing a portion they were still as long as a certain class of unpruned 
mother shoots. An examination of Table III shows, however, that there 
is no ground for this objection, because the longest unpruned mother 
shoots failed to produce as much lateral growth as the shortest pruned 
shoots. The objection may, therefore, be dismissed. 
An inspection of the trees in the orchard would convince any impartial 
observer that the pruned trees were in no way inferior in size to the 
unpruned, although the shape of the tree naturally differs. After three 
years the trees receiving heavy pruning each winter—the trees on which 
the pruned mother shoots were selected for measurement—had an aver¬ 
age trunk girth of 16.2 ±0.3 cm., and the unpruned trees had a girth of 
16.6 ±0.2 cm. Obviously the difference between the two is negligible. 
Passing to the second possible explanation, that of an inhibitor, we 
should expect to find that the removal of the apical bud of a shoot, or of 
the zone in which the inhibitor was principally produced, would be 
shown by greater growth of laterals from the shoot remaining. So long 
as the principal source of the inhibitor were removed the total amount of 
new growth would have little, if any, relation to the length of the mother 
shoot until new supplies were produced. The data give strong evidence 
in favor of such an assumption. As soon as growth of the new lateral 
got underway more of the chalone would be produced and would inhibit 
growth in the subapical laterals so that total lateral growth would be 
limited and would diminish with the distance of the laterals from the 
apex of the mother shoot. 
