76 Bulletin 393 



because they have a greater diameter of conducting tissue and hence can 

 obtain more sap. 



It has been seen that the leaf area for spurs which have a conducting 

 tissue of a given diameter and which were taken from Hmbs producing 

 many flowers, is less than that for spurs with the same diameter of con- 

 ducting tissue but taken from limbs producing few flowers. If the size of 

 the leaves is an indication of the supply of sap that reaches the spur, it 

 must be assumed that the former spurs are not so abundantly supphed 

 as the latter even tho they have conducting tissue of the same diameter. 

 It probably requires greater sap pressure to expand mixed buds, which 

 contain both flowers and leaves, than is needed to push leaf buds. More- 

 over, the petals of the flowers will transpire considerable moisture. It 

 seems reasonable, therefore, to assume that limbs producing a heavy 

 bloom will supply less sap to the individual spur than similar limbs which 

 produce a light bloom. The spurs from the former limbs are not so likely 

 to set fruit as those from the latter limbs. Can this be due to an inade- 

 quate supply of sap ? 



RELATION BETWEEN AMOUNT OF LATERAL GROWTH FROM THE FLOWER- 

 BEARING SPUR, AND FRUITFULNESS OF THE SPUR 



The elongation of a spur that is producing flowers is dependent on the 

 pushing of at least one lateral bud found on the current season's spur 

 growth (fig. I , page 51). In a few spurs the setting of a fruit inhibits the for- 

 mation of a lateral bud. In some cases lateral buds are formed, but they 

 do not push until the following year; in other cases, as much as twenty- 

 five centimeters lateral growth is produced by the fruiting spur. All 

 gradations between these extremes are found. The lateral growth may 

 begin even before the flowers have opened, and by the time the fruit 

 sets such growth may be several centimeters long. Observations here 

 showed that fruit-setting on spurs that had made from five to ten centi- 

 meters of lateral growth was not uncommon. In fact it appeared that 

 only a relativel}^ small proportion of such spurs lost their fruit. 



The amount of lateral growth produced by setting and by non-setting 

 spurs derived from the same limb was recorded in several cases. Data 

 for a Baldwin limb are given in table 29. It is seen that fruit is borne on 

 spurs that produce much lateral growth as well as on those that produce 

 little growth. The average weight of the lateral growth is greater in the 

 spurs that bear fruit than in those that lose their fruit. 



In other cases, the lateral growth produced by spurs taken from limbs 

 that bore many fruits and from similar limbs that bore few fruits, was 



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