I04 Bulletin 393 



activities of the fruit. In the early summer of 19 16, water-core was 

 noticeable on a number of apples, especially Fall Pippin and Tompkins 

 King. All the water-cored apples from several trees were closely examined, 

 and in every case observed such fruits had been stung by aphids. Not 

 all the fruits injured by the lice were water-cored, but water-cored apples 

 that had not been stung could not be found at that time. 



That water-core may, however, result from other conditions besides 

 aphid work is shown by the following observations: During the early 

 summer of 1915, when the fruits were about three centimeters in diameter, 

 a number of slender branches heavily laden with apples and leaves were 

 cut from a tree and taken to the laboratory. The cut ends of the branches 

 were placed in beakers containing water. Many of the fruits were removed, 

 weighed, and cut open that same evening; none of these were water- 

 logged. The next day all the apples from several different branches 

 showed a water-cored condition. On the following day some fruits were 

 again examined, all of which were found to be normal. Similar observa- 

 tions were subsequently made on twigs brought into the laboratory pri- 

 marily for this purpose. 



These facts can be accounted for by the following probable explanation : 

 The ends of the freshly cut twigs permitted the free passage of water 

 into the branch. Transpiration during the night was reduced to a mini- 

 mimi, which resulted in the accimitdation of water in the fruit, thereby 

 producing the water-logged condition. After some time the ends of the 

 twigs became clogged, due to bacterial development, and as a result water 

 entered less freely. The leaves transpired water more rapidly than it 

 could be supplied thru the cut end of the twigs. This produced con- 

 ditions favoring incipient drying, and hence the leaves began to with- 

 draw water from the fruit. After the withdrawal of water had been going 

 on for a time, the fruit regained its normal condition. 



The water-cored condition observed in connection with aphid work 

 cannot be changed by detaching the spur and allowing the leaves to with- 

 draw the water. The leaves on detached spurs with aphid-stung fruit 

 that was water-cored, dried up in all cases, while the fruit itself remained 

 firm. Do apples injured by lice develop a greater sap concentration than 

 they normally possess? Unfortunately no determinations were made 

 regarding this question. 



EXPERIMENTS CONCERNING THE ABSCISS-LAYER 



The shedding of flowers and immature fruits is brought about by the 

 formation of an absciss-layer similar to that which precedes leaf fall 



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