Nov. 1, 1925 
Fruit-hud Formation of Pear and Apricot 
879 
was the case. Both the heavily and lightly pruned and irrigated trees 
were slightly ahead of the nonirrigated tree on November 1, but there 
was no apparent difference December 1. 
In Sonoma County the buds from the nonirrigated tree seemed to 
have a lead over those from the irrigated one throughout the season; 
both trees were heavily pruned (fig. 2). The lead was slight on July 
11, but by September the buds from the nonirrigated tree were about 
30 days in advance. These buds were noticeably ahead when the 
last samples were taken. Buds grown with the combined influence 
of nonirrigation and light pruning were slightly farther ahead of the 
heavily pruned and irrigated than of the heavily pruned and non¬ 
irrigated. 
Regions Compared 
Comparison of pear buds taken from Eldorado (Sierra-foothill con¬ 
ditions) and Yolo Counties (interior-valley conditions) under the 
same cultural treatment (fig. 2) showed that the buds grown under 
foothill conditions were, on July 20, slightly behind those from the 
interior valley and developed at a slower rate until the middle of 
August. Later collections, however, showed a rapid development in 
the buds from Eldorado County, which were leading October 1. By 
November these buds had reached a stage of development that buds, 
grown under interior-valley conditions required from two to four 
additional weeks to reach. 
Although pear fruit buds in the coastal valley and in the foothills 
apparently differentiated at about the same date, those in the cooler 
and more humid section developed more rapidly than those at the 
high elevation. The buds from the coastal valley were at least 30 
days ahead by the middle of August. However, the buds grown under 
foothill conditions made such advance during September that the 
stages of development were equal October 1 and the Eldorado buds 
even slightly in the lead by November 1. 
DIFFERENTIATION AND DEVELOPMENT OF FRUIT BUDS OF THE APRICOT GROWN 
UNDER THE VARIOUS CONDITIONS 
Light and Heavy Pruning Compared 
Pruning and irrigation treatments of apricot trees could not be 
compared in respect to fruit-bud formation, except at the university 
farm. The lightly and heavily pruned trees were irrigated. Both 
showed the initial signs of fruit-bud formation about August 10, 
and buds from each developed equally until the middle of September 
(fig. 3). Collections made September 15 and October 1 indicated 
the heavily pruned tree to be considerably ahead in floral develop¬ 
ment. This lead was not maintained, however, and the lightly 
pruned tree had buds showing the ovule primordia December 1, 
while none were found in buds taken from the heavily pruned trees. 
Irrigation and Nonirrigat:on Compared 
Fruit buds taken September 15 from the nonirrigated apricot tree 
in the university orchard showed a slight lead over those from irri¬ 
gated trees, and they maintained it as long as collections were made 
(fig. 3). Prior to September 15, no difference in degree of develop¬ 
ment was observed. 
