I 



Abscission of Flowers and Fruits of the Apple 103 



TABLE 51. Weight of Spur, Number of Seeds, and Weight of Fruit, 

 ON One-fruited and on Two-fruited Spurs 



the spurs bearing one fruit produce apples nearly as heavy as the more 

 vigorous spurs with two fruits, even tho the latter have more seeds. 



Relation between aphid work and fruit development 



Number of seeds in normal apples and in apples stung by aphids. — 

 Another influence causing unequal conditions among fruits otherwise 

 similar is that exerted by the sting of the aphid. Apples severely injured 

 by aphids are easily recognized by their malformed condition (Parrott, 

 Hodgkiss, and Lathrop, igi6). Such fruits will not drop even tho few 

 or no seeds have been formed. Data regarding this point are given in 

 table 5 2 : 



TABLE 52. Average Number of Seeds in Normal Apples and in Apples 



Stung by Aphids 



Condition of fruit 



Normal 



Stung by aphids , 



Number 

 of 



fruits 



50 

 100 



Average 

 number 

 of seeds 



6.94 

 2 93 



Percentage 



having 



less than 



four seeds 



22 



87 



Percentage 



having 



no seeds 



o 

 20 



In many cases the injury caused by aphids is not very noticeable, 

 especially after the fruit has attained a diameter of several centimeters. 

 There is no conspicuous malformation of the apple, and the spurs are 

 apparently free from the pest. On close examination, however, many 

 fruits apparently normal show the effects of aphid work. Such fruits 

 are frequently found on weak spurs in spite of a low seed value. The 

 stimulation resulting from the attacks of the aphid may be held account- 

 able for such apparent discrepancies. 



Water-core as affected by aphid work and water supply. — An observation 

 regarding another influence of aphid work may be recorded at this time, 

 since it shows that the aphid actually does influence the physiological 



21' 



