B50 
Journal of Agricultural Research 
Vol. XXI, No. xi 
in illumination. None of the trees had produced any fruit up to the 
time these measurements were made. 
The two classes of mother shoots (pruned and unpruned) were on 
different trees. The 270 pruned mother shoots were on 91 trees which 
had received systematic “heading back”; the 54 unpruned mother 
shoots were on 25 trees which received no pruning. While this distri¬ 
bution does away with a certain closeness of spatial association, it pre¬ 
vents the possible transmission of influences from one class of mother 
shoots to the other. 
In the present paper the term “growth” is used to designate a per¬ 
manent increase in size. It is well recognized, however, that the same 
term may also be applied to phenomena in which there is little if any 
increase in size—for example, differentiation of organs and tissues. 
The length of the lateral was taken as a simple measure of its growth. 
The almost complete absence of secondary laterals of any consequence 
allows this kind of measurement to be taken with a comparatively small 
error. Even where secondary laterals were produced there was no 
evidence that they had limited the length-growth of the primary lateral. 
The shoots produced in a single season on a vigorous pear branch are 
usually of two kinds—“laterals” and “fruit spurs.” The general char¬ 
acteristics of these two types of shoots have been discussed by Vochting 
(14) and others. While it is convenient to consider the two types of 
shoots separately, it is necessary to remind the reader that their differ¬ 
ences are primarily quantitative and not qualitative. The fruit spurs 
ordinarily attain but a short length and produce fruit-bearing buds. 
Under various circumstances they may, however, be forced to make 
strong vegetative growth and become “laterals.” Such results often 
follow severe pruning or a change of position of the parent shoot whereby 
the dorsally placed “fruit spurs” will develop into vegetative “laterals” 
(jo). A true dimorphism does not seem to exist in the young branches 
of the pear tree. 
The “first” lateral is designated as the lateral at the distal end of the 
mother shoot, and the others follow in serial order toward the proximal 
end of the mother shoot. The “original” number of buds on a mother 
shoot was the number present before any laterals had grown—that is, 
at the beginning of the 1919 growing season. 
The mother shoots on the pruned trees had a mean length of 44.1 cm. 
and a coefficient of variability of 39.2 per cent. The original number of 
buds on these mother shoots had a mean of 15.5 buds with a coefficient 
of variability of 41.1, and so elsewhere. The mother shoots on the un¬ 
pruned trees had a mean length of 50.6 cm. with a coefficient of varia¬ 
bility of 29. The number of original buds they possessed was 21.5 with 
a coefficient of variability of 25.2. The frequency distributions of these 
variants are shown in figure 1. Both distributions are asymmetrical 
and have a skewness in the direction of the higher values. 
