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Bulletin 393 



It should also be pointed out that the lateral buds on many flower-bearing 

 spurs can be forced into growth by severe pruning of the branch that 

 produces the spurs. It seems reasonable, therefore, to assume that such 

 lateral spur growth is an indication of an abundant supply of sap. 



RELATION BETWEEN SAP SUPPLY AND FRUIT SETTING 



Several of the observations previously recorded have suggested that 

 an adequate supply of sap to the individual spur is an important factor 

 in the setting of fruit. The object of the following experiments was to 

 determine whether the percentage of spurs that set fruit could be increased 

 by increasing the sap supply, or decreased by reducing the sap supply, to 

 the individual spurs. 



In the spring of 191 6, large limbs, which were approximately five centi- 

 meters in diameter at their bases and which had a full bloom, were selected 

 in pairs. The members of such pairs either formed the arms of a Y or 

 arose within a foot of each other from the same parent branch. It was 

 necessary to have the limbs of a given pair as nearly alike as possible 

 in vigor, exposure, bloom, and size, and for this reason the selection of 

 suitable pairs was no easy task. 



In several cases one limb of a pair was sawed halfway thru near its 

 base, and the second limb was left untreated or was pruned lightly by 

 cutting out entire twigs containing both weak and vigorous buds. In 

 other cases one limb was left unpruned and not sawed at its base, while 

 the second limb had at least half the total number of branches removed. 

 The object of sawing the branches at the base was to diminish the normal 

 sap supply to the spurs on the limbs so treated. The aim of the severe 

 pruning was to increase the flow of sap to the individual buds. The 

 treatments were given just before the flowers opened. The results are 

 recorded in table 31: 



TABLE 31. Percentage of Flower-bearing Spurs Setting Fruit on Limbs with 

 Increased and on Those with Diminished Sap Supply 



♦Treatments: i, treated limb sawed at base; 2, treated limb severely pruned; 3, treated limb slightly 

 pruned; 4, limbs untreated. 



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