870 
Journal of Agricultural Research 
Vol. XXI, No. II 
the value of k was the same, but that of a differed in the two equations. 
The rate of growth in such a case is expressed by the differential equation 
or, 
The rate of growth of the shoot appears, therefore, to be dependent 
upon its final length. The rate may be affected by (1) a variation in the 
activity of the catalyst or (2) a variation in the supply of potential growth 
materials. The case of the apricot shoots is believed to be applicable to 
the pear shoots. 
It is difficult to understand how the amputation of a greater or less 
portion of a mother shoot can increase the supply of potential growth 
material for the same except as it decreases the number of meristematic 
centers. Two arguments against the validity of such an assumption at 
once arise. In the first place, mother shoots which had been pruned pro¬ 
duced more new material than unpruned mother shoots possessing the 
same number of buds (Table III). In that case the number of competing 
growth centers was the same, but the results were different. In the 
second place it has already been shown that the number of buds left on 
a pruned mother shoot had very little effect upon the total amount of 
new shoot wood produced. The deviation of the values from their mean 
was less than 10 per cent of the mean. 
We, therefore, seem to have reason to assume that the cause of the 
increased growth is to be referred to an increased activity of the growth 
catalyst. The reason for this increased activity will be discussed in con¬ 
nection with the difference in growth of the several laterals. 
If no opposing factors were operative we should expect that each 
mature bud on the mother shoot would develop into a lateral shoot. The 
size of the laterals would be largely determined by the amount of energy 
which they were able to obtain from the parent tree supplemented by 
what they could obtain from outside sources. To state it somewhat more 
specifically, the size of a young lateral at the outset would depend upon 
the amount of growth-promoting material which the parent tree could 
furnish it. In course of time, however, the assimilatory system of the 
new shoot would be able to furnish additional supplies of material, a part 
of which could be used to further the growth of that shoot. The amounts 
of growth-promoting materials obtained in the latter, as well as in the 
former, case would largely be determined by the position of the shoot, 
which would in turn determine the conditions of competition for water, 
light, and other factors. The buds near the base of the mother shoot 
might, therefore, be expected to grow first into shoots and subsequently 
to develop as their access to light should give them opportunity. 
