866 
Journal of Agricultural Research v 0 i. xxi, n 0 . n 
Further light on these questions may be obtained if we inquire con¬ 
cerning the possibility that any lateral may grow to the length of the 
lateral immediately above it. By use of a formula given by Harris (j) 
we may obtain a quantitative expression of this capacity of subapical 
laterals to come to development. The capacity of the second lateral to 
develop with respect to the first might be expressed as 
where r xy is the coefficient of correlation between the two characters 
and V x and V y are their coefficients of variability. 
Determination of these constants gives the following: 
Lateral II with respect to lateral I -0.883 ±0.009. 
Lateral III with respect to lateral II -0.876 ±0.010. 
Lateral IV with respect to lateral III -o.83o±o.oi3. 
Lateral III with respect to lateral I —0.973 ±0.002. 
Lateral IV with respect to lateral II -0.958 ±0.003. 
Lateral IV with respect to lateral I —0.991 ±0.001. 
These coefficients measuring the correlation between the length of the 
subtending lateral and the deviation of the variables from their probable 
values are all negative and relatively large. Their values have a tendency 
to increase as the distance between the laterals increased. 
The results show that the subtending laterals fail to attain the size 
we should expect when the more distal laterals have a larger size. In 
short, there is the clearest evidence of a competition, or of an inhibition 
of growth, associated with the development of the higher laterals. 
III. PRODUCTION OF FRUIT SPURS 
The short, spur-like branches on the limbs of the pear and other trees 
call for special consideration. They differ from the longer pliable shoots 
of the same tree in being primarily fruit-bearing shoots and, in the 
parlance of the horticulturist, are called "fruit spurs.” As is well 
known, they grow slowly in length, have short intemodes, and charac¬ 
teristically bear a flower bud at the apex instead of a vegetative bud. 
The fundamental physiological and morphological differences between 
the two classes of shoots have been clearly set forth by Vochting (14) 
and others. 
If we grant that the production of fruit spurs, as well as that of the 
longer laterals, is a function of the growth process of the tree, we may 
proceed to inquire concerning their distribution and the laws of their 
characteristic growth. The difference between fruit spurs and purely 
vegetative shoots, as mentioned above, is primarily one of degree and 
not of kind. Consequently it is necessary to fix, arbitrarily, the length 
