746 EXPEEIMENT STATION RECORD. [Vol.38 



and ability of the spur to set fruit; relation between length of spur growth 

 made during the preceding season and fruitf ulness of the spur ; relation between 

 weight of flower-bearing spur and its fruitfulness ; relation between weight of 

 spur to the number of flowers and to the length of the previous season's 

 growth ; relation between the weight of the new spur growth and the diameter 

 of the conducting tissue ; relation between diameter of conducting tissue and 

 weight of spurs, from limbs having a light bloom and from those having a fuU 

 bloom ; relation between water supply, leaf area, and pushing of buds ; relation 

 between amount of lateral growth from the flower-bearing spur and fruitful- 

 ness of the spur ; relation between sap supply and fruit setting ; fruit setting 

 as influenced by varying amounts of leaf surface on the flower-bearing spur ; 

 influence of sunlight on the setting of fruit ; relation between seed formation 

 and fruit development ; observations concerning some of the physiological 

 effects of seeds ; i-elations to be considered in choosing fruits borne under simi- 

 lar conditions ; and experiments concerning the formation of the absciss layer, 

 showing the effect of removing fruit and leaving varying lengths of stem, effect 

 of coating fruit with vaseline to inhibit transpiration and exchange of gases, 

 effect of slow and rapid drying of leaves on detached spurs with uncoated 

 fruit and on detached spurs with vaseline-coated fruit, and the effect of a satu- 

 rated and of a dry atmosphere on abscission of fruit on detached spurs. 



The author found that from two-fifths to four-fifths of the total number of 

 flowers are lost during the early drop, or within from one to four weeks after 

 the petals fall, only 3 to 7 per cent of the total number of flowers finally 

 develop into fruits, and from one-sixth to one-third of the flower-bearing spurs 

 finally set fruit. The proportion of spurs that set fruit after the first drop and 

 that hold fruit after the June drop varies with the variety, with individual trees 

 of the same variety and on different limbs of the same tree. 



Summing up the evidence as a whole, the author concludes that " the results 

 presented . . . emphasize the importance of vigor, more especially the vigor 

 of the individual spur, as a factor in fruit setting. As compared to weak spurs, 

 the previous season's growth of vigorous spurs is longer, the new spur growth 

 Is heavier, the leaves are larger and more numerous, there are more flowers to 

 the spur, the diameter of the conducting tissue is greater, and the weight of the 

 lateral spur growth is greater. 



" The vigorous spurs seem to favor fruit setting because they can supply the 

 developing fruits with an abundance of water and food. Seeds appear to be 

 valuable because they supplement the forces that bring sap to the fruit. 

 Strong seeds are of primary importance for the setting of fruit on relatively 

 weak spurs ; they are of lesser importance for the setting of fruit on strong 

 spurs. 



" The number of strong seeds is dependent on effective fertilization, which in 

 turn presupposes cross-pollination. Even though the grower may plant several 

 varieties of the same fruit which bloom during the same time, nevertheless 

 cross-pollination is frequently prevented by unfavorable weather during bloom- 

 ing time. Man has little control over the weather. On the other hand, man may 

 influence the vigor of the tree by cultural methods. Trees in sod, for example, 

 are usually less vigorous than trees in a tilled orchard. The latter, as a rule, 

 produce heavier crops of fruit. . . . 



" The application of a quick-acting nitrogenous fertilizer, such as sodium 

 nitrate, early in spring may have a decided effect in stimulating early and 

 rapid spur growth that would be likely to set fruit the following year. Some 

 evidence for this suggestion is contained in the paper by Lewis and Allen 

 [E. S. R., 35, p. 540] received by the writer while the present report was in 

 the course of preparation. . . . 



