874 
Journal of Agricultural Research vo 1 .xxj.no. h 
(5) The lateral arising from the distal end of an upright mother shoot 
exerts a well-marked dominance over those arising from buds beneath it. 
The mother shoots which were most reduced in length by pruning usually 
produced longer distal laterals. 
(6) There is a well-marked positive correlation in the length of neigh¬ 
boring laterals on the same mother shoot, but the correlation diminishes 
as the distance between the points of origin of the laterals increases; 
that is to say, the longer the distal lateral becomes the more will the 
subtending laterals fall short of the size which they might be expected 
to attain from the general size relations in the population under con¬ 
sideration. In harmony with such a relationship, it was found that the 
capacity of any lateral to reach the length of a lateral situated higher 
on the mother shoot is expressed by a relatively large negative coefficient. 
(7) Fruit spurs were commonly more abundant upon unpruned 
mother shoots than upon those receiving pruning in the previous winter. 
(8) The growth response indicates that increased growth following 
pruning is due to the removal of regions containing, or producing, sub¬ 
stances which would otherwise tend to inhibit growth of other members 
of the system. Each mature bud on the mother shoot seems capable of 
developing into a lateral provided it be sufficiently free from growth- 
inhibiting substances. 
(9) On the assumption that the pear branches produce a gro w th-inhibi ting 
substance which flows in a basipetal direction, it is logical to find a 
gradient in the formation of laterals such as that existing here. The 
inhibitor would be more concentrated as the distance from the apex of 
the shoot increased. The effect of the increasing concentration would be 
to retard increasingly the growth of the lower laterals until finally such a 
concentration would be reached as to inhibit growth entirely. In this 
way the dominance of the apical shoots would be not only established but 
perpetuated. 
LITERATURE CITED 
(1) BrenchlEy, Winifred E. 
1919. some factors in plant competition. In Ann. Appl. Biol., v. 6, no. 2/3, 
p. 142-170, 10 fig., pi. 5. 
(2) Child, Charles Manning. 
1915. individuality in organisms. 213 p., 102 fig. Chicago. 
(3) Harris, J. Arthur. 
1909. THE CORRELATION BETWEEN A VARIABLE AND THE DEVIATION OP A 
dependent variable from its probable value. In Biometrika, 
v. 6, pt. 4, p. 438-443- 
(4) Johnson, Myrtle Elizabeth. 
1910. A QUANTITATIVE STUDY OF THE DEVELOPMENT OF THE SALPA CHAIN IN 
salpa fusiFormis runcinaTA. In Univ. Calif. Publ. Zool., v. 6, no. 7, 
p. 145-176, 15 fig., 2 tab. Literature cited, p. 176. 
(5) LoEb, Jacques. 
1917. the chemical basis of axial polarity in regeneration. In Science, 
n. s. V. 46, no. 1179, p. 547 _ 55 i 2 3 4 5 - 
