Nov. 1, 1925 
Fruit-bud Formation of Pear and Apricot 
873 
in later stages of the pear as Kraus ( 10 ) described for the apple. 
Small swellings on the bottom of the receptacle cup indicated the 
beginnings of carpels. Buds collected in December showed petals 
differentiated further and almost inclosing the stamens and carpels 
below. The stamens showed some differentiation into anthers and 
filaments, and styles were projecting upward from the carpels. In 
some cases cavities could be seen in the carpels. 
Mother cells (pi. 3) were clearly seen in the anthers of the buds 
gathered January 1. The mother cells were somewhat larger than 
the surrounding cells. They were located in the centers of the four 
lobes of the anthers and contained very large nuclei, staining dark 
red with safranin. The buds made little advance, except in size 
of anther, until about February 28. The mother cells had enlarged 
and become rounded, surrounding cells had differentiated into anther 
walls, and by the expansion of the anthers the mother cells had 
become more or less loosely associated. The five carpels had pushed 
up through the center of the bud into a well-defined pistil and two 
ovules could be seen as small knobs protruding from the enfolding 
placenta of the ovary. The petals completely covered over the 
other parts of the flower and appeared lanceolate in longitudinal 
section. Growth expansion was taking place in all parts and swelling 
of the buds could be observed by external examination in the field. 
Well-defined tetrads, or clusters of the four granddaughter cells, were 
in evidence in material gathered March 8. This four-cell stage must 
be of short duration, because six days later each unit of the tetrad had 
broken away and was differentiated into a nearly, if not entirely, 
mature pollen grain. 
On March 6 the stage of development of the anthers was much in 
advance of that of the carpels. The pollen grains were matured, 
whereas the ovules were at very early stages. One might be led to 
believe from this that the condition would result in a clear case of 
protandry. On the contrary, development in all parts of the pistil 
progressed from this date at an exceedingly rapid rate. From the 
small protuberances marking the start of tie ovules on February 28, 
outer and inner integuments were well defined and inclosed the 
embryo sacs. Development in the remainder of the pistil was as 
rapid. The styles elongated greatly, and stigmas were differentiated, 
while enlargements of all parts took place. 
DIFFERENTIATION AND DEVELOPMENT OF FRUIT BUDS OF THE APRICOT 
The first collection of heavily pruned and irrigated Royal apricots 
on the university farm ^interior-valley conditions) was made July 7. 
When these buds were sectioned it was found that the growing point 
was perfectly smooth, rounded slightly, and giving rise to bua scales 
from all sides. In this condition it was impossible to distinguish 
between future leaf buds and fruit buds. The same was true of all 
collections until July 31. At this date no definite signs of the initial 
fruit-bud stage were found, but the crown was giving rise to no more 
bud scales. On August 10 (pi. 4) the crown or growing point had 
become slightly elevated and flattened on top, while very small pro¬ 
tuberances were observed at each side in longitudinal section, showing 
definite differentiation into fruiting buds. The sepal primordia were 
