882 
Journal of Agricultural Research 
Vol. XXXI, No. 9 
influence of irrigation on fruit-bud development of the pear was most 
strikingly shown under coastal-valley conditions. Only buds col¬ 
lected July 7 and 21 from nonirrigated trees on the university farm 
showed any lead over those taken from irrigated trees. No difference 
in development of fruit buds of irrigated and nonirrigated apricot 
trees under interior-valley conditions could be observed until Sep¬ 
tember 15. At this date the buds from the nonirrigated trees assumed 
a lead which they maintained as long as collections were made. 
SUMMARY AND CONCLUSIONS 
A study was made of the influence of certain cultural and environ¬ 
mental factors on the differentiation and development of Bartlett 
pear and Royal apricot fruit buds. In order to study the environ¬ 
mental influences upon fruit-bud formation and development, mate¬ 
rial was collected at short intervals between July 7 and November 1, 
1922, and from three typical fruit-growing regions of California, 
namely, Sierra foothills (Eldorado County;, interior valley (Yolo 
County), and coastal valley (Sonoma County). In addition, samples 
under interior-valley conditions were collected until blossoming time. 
To study the effect certain cultural practices might have, lightly 
pruned trees were compared with heavily pruned ones, and irrigated 
were compared with nonirrigated trees in respect to time of fruit-bud 
formation and the rate of development. The following conclusions 
seem justified: 
1. rear fruit"buds begin to differentiate at approximately the same 
date under coastal-valley, interior-valley, and foothill conditions. 
2. Apricot fruit buds begin to differentiate at approximately the 
same date under coastal-valley, interior-valley, and foothill condi¬ 
tions. 
3. The high altitude of the foothills seems to have a retarding in¬ 
fluence on fruit-bud development until the middle of September 
when development becomes more rapid. 
4. The humid coastal conditions apparently stimulate rapid 
development of pear buds after differentiation. This is not the case 
with apricots until October when development becomes extremely 
rapid and the buds go into the winter at a more advanced stage than 
is found under either interior-valley or foothill conditions. 
5. The dry, hot, interior valley seems to induce a steady uniform 
development of both pear and apricot fruit buds; however, these 
have not reached the advanced stage of development by early winter 
that buds from the coastal valley and foothills have attained. 
6. The inception of fruit-bud differentiation seemingly is not in¬ 
fluenced to any extent by either heavy or light dormant pruning. 
Light pruning perhaps, tends to induce a slightly more rapid develop¬ 
ment for six to eight weeks following fruit-bud differentiation of the 
pear. 
7. Irrigation seems to have a retarding influence on fruit-bud dif¬ 
ferentiation and development. 
8. Environmental conditions during winter, as found in the prin¬ 
cipal fruit-growing districts of California, do not seem to have any 
checking influence on fruit-bud development of the pear and apricot. 
