Abscission of Flowers and Fruits of the Apple 83 



TABLE 36. Number of Fruits to the Spur on Normal and on Defoliated Spurs 



These results are interesting because they show that a small leaf surface 

 in itself, such as is found on spurs on weak limbs or on those with a heavy 

 bloom, is not accountable for a poor set of fruit. The data at hand do 

 not afford an adequate explanation for the results obtained. On the 

 basis of observations and experiments presented later, however, it seems 

 reasonable to assume that the leaves favor fruit-setting on vigorous spurs 

 because they assist in drawing sap to the fruit. 



influence of sunlight on the setting of fruit 



In order to learn whether or not a variety is self-sterile, cross-pollination 

 is prevented by inclosing the flower spurs in sacks. According to Ewert 

 (1907), such treatment subjects the inclosed spurs to unnatural conditions 

 which may be unfavorable for the setting of fruit. The object of the 

 following experiments was to determine the effect of excluding sunlight 

 on the setting of fruit. 



Some vigorous spurs were inclosed in brown opaque paper bags, and 

 some in white translucent paper bags. Only the most vigorous spurs 

 were inclosed, and for each spur inclosed in a translucent sack a similar 

 spur arising from the same parent branch was inclosed in an opaque sack. 

 The spurs were sacked in the spring of 1916, before the clusters of flowers 

 had separated. The set of fruit was determined in late simimer. Unfor- 

 tunately a large number of the sacked spurs had to be discarded because 

 of aphid work. The data obtained, however, are very suggestive. They 

 are recorded in table 3 7 , in which it is seen that over twice as many spurs 

 set fruit in the translucent sacks as in the opaque sacks. 



The following notes may be of interest: On May 17, 19 16, the flowers 

 in the opaque bags had white petals, and all flowers in the cluster were 

 open; the flowers in the translucent bags had pink petals, and were some- 

 what further advanced than the flowers in exposed clusters. The stigmas 



197 



