92 Bulletin 393 



Relation between seed value, weight oj spur, and set oj fruit 



That the vigor, or weight, of the flower-bearing spur is an important 

 factor in determining whether the flowers will set fruit, has been suggested 

 by data previously recorded. Figures have likewise been presented which 

 show that the drop apples contain fewer seeds than the fruit that remains 

 on the tree. This indicates that the number of seeds, which presupposes 

 effective pollination, likewise plays a part in determining the set of fruit. 



Since, then, the smaller spurs are more likely to lose their fruit than 

 the larger, and since the average number of seeds is less in the drops 

 than in the setting fruit, it is apparent that most of the few-seeded drops 

 were borne on small spurs, ' 



But, as has been shown, there are many fruits that remain on the tree 

 even tho they have few seeds — less in some cases than are found in 

 the average fruit that has dropped. According to the statements in 

 the preceding paragraph, these few-seeded fruits would have fallen if 

 they had been borne on relatively light spurs. Therefore it must be 

 assumed that they were produced on vigorous spurs. Since relatively few 

 fruits with many seeds are found among the drops, and since there is no 

 basis for assuming that the flowers on less vigorous spurs will necessarily 

 be poorly pollinated and hence develop few seeds, one might expect to 

 find fruit with many seeds on relatively weak as well as on vigorous spurs. 

 To account for the drops with many seeds it must be asstmied, in order 

 to be consistent, that these came from very weak spurs. Then, too, 

 they might have a low seed value even tho their seed number is high. 



Stating this hypothesis in other words, few-seeded fruits, or, more 

 accurately, fruits with a low seed value, are borne only on the heavier 

 spurs, while many-seeded fruits, or those with a high seed value, may 

 be borne on relatively light as well as on vigorous spurs. 



In order to test this hypothesis, the weights of several hundred spurs, 

 together with the weights of the fruits borne on them and the number 

 of seeds in each fruit, were obtained during late July and early August. 

 The weight of spur includes all of the present season's growth minus the 

 lateral growth. The spurs were cut from the twig in the manner previously 

 described (page 67). The spurs obtained from each twig or branch were 

 divided into two lots, one containing the fruits with a high seed value 

 and the other including the fruits with a low seed value. The determina- 

 tion of the seed value of a fruit was based on the observations regarding 

 the relation between number of seeds, vigor of spur, and size of fruit. 

 These observations also afforded the suggestions for the study of the 

 relation between number of seeds, size of spur, and set of fruit. The 

 results are recorded in table 45 : 



2Q6 



