Nov. 1, 1925 
Fruit-bud Formation o f Pear and Apricot 
881 
fornia, might be explained by the relatively early beginning of the 
growing season in the latter State. Whether this or something else 
is the right explanation, it is clear that there are differences between 
localities. The writer knows of no data on the time of fruit-bud 
differentiation of the apricot except in California. 
The development of fruit buds under interior-valley conditions is 
characterized by a slow but steady development of the floral parts 
through the summer and winder, with a rapid growth, of ovules 
especially, in the spring just before blossoming. Winter seems not 
to have any appreciable checking influence, although buds in Cali¬ 
fornia, even though blossoming earlier, are at a less advanced stage 
in December than are buds at the same time in the Eastern States. 
Apricot buds differentiate a month or more later than pear buds, 
but develop at a much more rapid rate, and come into blossom earlier. 
It would seem from the data collected that the differentiation 
both of the pear and apricot fruit buds, respectively, takes place 
at approximately the same time in all regions from which samples 
were taken. It is interesting, however, to note the more rapid 
development under coastal-valley influences. Development of fruit 
buds from the foothill sections, though slow at first, was only slightly 
less rapid than under coastal-valley conditions, while the stages of 
development of buds collected under interior-valley conditions were 
the least advanced November 1. In the case of the pear fruit buds, 
the lead of those from near the coast was maintained from the start, 
and this lead increased steadily until in October when they were 
about a month ahead of those grown at the higher altitudes. Devel¬ 
opment of fruit bjads under foothill conditions was almost at a stand¬ 
still following differentiation until September, when it progressed 
rapidly, due perhaps to the cooler weather there. 
Gardner, Bradford, and Hooker (< 5 ) state that the rather restricted 
period of fruit-bud formation can be varied somewhat by cultural 
treatment, including, perhaps, any practice that modifies the rate of 
growth. As summer pruning has an influence on the time of fruit-bud 
differentiation ( 4 ), and since light and heavy pruning, popularly 
known as “long” and “short” pruning, cause very different reactions 
in other respects, why, then, should not light and heavy dormant 
pruning operate differently in respect to fruit-bud differentiation? 
wSince heavy pruning induces much shoot growth, one might expect 
it to cause growth later in the season and thereby bring about later 
differentiation. This was found to be rather strikingly the case with 
the two pear trees under coastal influences. These trees grew on 
two types of soils, which may have caused the difference. When 
pruning methods were compared in the interior valley, the heavily 
pruned pear tree differentiated fruit buds a few days in advance, the 
reverse of the observation at the other location; however, the lightly 
pruned tree developed somewhat faster through July and August. 
With the exception of the collections made September 15 and October 
1, the heavily and lightly pruned apricot trees on the university 
farm showed the same rate of development. It would seem from the 
data available, at least in the case of the pear, that light pruning as 
practiced in California tends to hasten development. 
Contrary to Goffs findings (7), and coinciding well with Kirby's 
conclusions ( 9 ), the lack of moisture apparently tends to hasten fruit- 
bud differentiation and subsequent development. The retarding 
