Sept, i, 1921 
Growth in Branches of Young Pear Trees 
867 
limit which shall define a fruit spur. In this investigation of young 
branches the limit has been set at 5 cm., and, in accordance, all shoots 
having a length of 5 cm. or less are designated as fruit spurs. 
The number of fruit spurs on the pruned mother shoots ranged from 
o to 13. The larger number were naturally found on the longer mother 
shoots. The energy of the shorter mother shoots appears to have been 
used mainly for the production of vegetative shoots. The number of 
fruit spurs on the unpruned mother shoots ranged from 1 to 20, but only 
two shoots had fewer than 4 fruit spurs. 
The data given in Table VII show the mean number of fruit spurs pro¬ 
duced on mother shoots of various classes. The mean spur production 
of the shorter pruned mother shoots is very low, but increases, somewhat 
irregularly, until the largest number is found on the mother shoots having 
more than 28 buds. There is a well-marked tendency, however, to less 
variability in spur formation on the longer mother shoots. The last two 
classes of mother shoots on the pruned trees seem to be in a class somewhat 
different from the others in respect both to the mean number of fruit spurs 
formed and in having much less variability with respect to the mean. 
It would seem that these pruned mother shoots failed to produce more 
than a minimum of fruit spurs except when they possessed more than 
25 buds per mother shoot. 
The mother shoots on the unpruned trees produced considerably more 
fruit spurs than their pruned neighbors. The lowest average in this 
group was practically equivalent to the highest average among the 
pruned trees. The variability in the number of fruit spurs with respect 
to their mean was less in the longest mother shoots than in those of any 
other class. Clearly there is a manifest tendency for decreased varia¬ 
bility to be associated with increased production of fruit spurs. This 
characteristic may also be discerned in the growth of vegetative laterals 
at least so far as their length is concerned. The greatest output of 
growth material leads to the production of the longest laterals and to 
the lowest variability. 
Tabl3 VII .—Variability in the production offruit spurs on mother shoots 
Number of original buds on mother 
shoot. 
Treatment of mother 
shoot. 
Mean number of 
fruit spurs per 
mother shoot. 
Coefficient of 
variability. 
4 to 6. 
Pruned 
0. 75 ±0. 20 
• • 13 
2. 53^ . 18 
2 - 2 3 ± -37 
3 - 6 o± -34 
2. 52 dr . 29 
2. 6 j ± . 41 
5 -° 7 ± • 5 i 
7. 88± .69 
7 - 33 ± 1. 5 2 
12. 15 dr .64 
15. 86dr 1. 14 
135- 71 ±40-38 
142. 3i±27. 00 
78. 26 ±10. 82 
163. 23^29. 82 
93- 89 ± 11. 07 
98. 41 d: 13* 97 
119. iodz21. 42 
57 - 79 ± 9-24 
38.83 d: 7.47 
141. 4 o±32. 83 
40. 00dr 4. 32 
28. 32 dr 5.48 
7 to 9. 
IO to 12. 
13 to 15. 
16 to 18. 
19 to 21. 
22 to 24. 
25 to 27. 
28 and more. 
12 to 19. 
Ilnnnined 
20 to 27. 
V/ 11 U 1 UilCU. 
28 to 36. 
----- 
