Abscission of Flowers and Fruits of the Apple 95 



that the apples which dropped from the trees in the sod orchard con- 

 tained more seeds to the fruit than the drops from the well-cared-for trees. 

 In other words, the former trees required the stimulus of many seeds to 

 set fruit, while the latter set fruit even tho few seeds were developed. 



observations concerning some of the physiological effects of 



SEEDS 



It has been shown that the size of the fruits borne on a given branch 

 under certain external conditions is dependent on the vigor of the spur 

 and the seed value. The higher the seed value, the larger is the apple 

 under conditions otherwise similar. This suggests that the seeds exert 

 some influence which increases the supply of sap to the fruit in which 

 they are borne. 



The heavier and more vigorous spurs, as previously shown, are pro- 

 vided with a large diameter of conducting tissue, which permits of more 

 abundant sap flow. Large spurs that have good conducting tissue are 

 able to set fruit with a low seed value, whereas the fruits on the smaller 

 spurs must have a high seed value if they are to continue development. 

 One might assimie that the handicap of poor conducting tissue in the 

 small spur is overcome by the pull on the sap flow exerted by the seeds. 

 Small spurs require considerable help in order to provide an adequate 

 supply of sap for a developing fruit, while large spurs need relatively 

 little help. The following direct evidence is presented to show that many- 

 seeded fruits actually do exert a greater pull on the sap flow than do 

 few-seeded fruits. 



Withdrawal of water by leaves from fruits with varying numbers of seeds 



A ntmiber of spurs, each bearing one fruit, were taken from a branch 

 of a Tompkins King tree in July, 191 5. All but three of the leaves were 

 removed from each spur, the leaves remaining being approximately of 

 the same size and therefore the leaf surface on one spur being equal to 

 that on any other. The fruits were coated with melted paraffin to pre- 

 vent transpiration, and the spurs were then exposed in the laboratory. 

 Some spurs without fruit and some detached fruits were exposed at the 

 same time. 



In conformity with the observations of Chandler (19 14), the leaves on 

 spurs that bore fruit remained turgid for several days, while the fruits 

 on such spurs wilted and became shriveled. The leaves on spurs without 

 fruit soon became dry and crisp. The detached fruits remained firm. That 

 the leaves on the spurs bearing apples obtained their moisture from the 

 fruit, is obvious. The point which is of special interest in this connection, 

 14 209 



