484 FUNDAMENTALS OF FRUIT PRODUCTION 



The set that the grower would call perfect varies greatly with species, 

 variety and with conditions. In 1899, Fletcher'*'' counted 4725 blossoms 

 of the apple, pear, plum and apricot; from these 617 fruits developed what 

 was considered a full crop for the branches on which they were borne. 

 It would be called a perfect set by the grower, yet the percentage actually 

 setting was 13. The setting of 20 to 30 per cent of the blossoms of the 

 Muscadine grape would give a full crop.^* If, however, the setting of 10 

 per cent of the blossoms provides for a full crop, a 5 per cent set will 

 provide only half a crop, though proportionally but a few more blossoms 

 drop. In terms of the percentage of blossoms setting, then, a difference 

 of a few per cent may have a great effect on the size of the crop so that 

 it becomes important to ascertain the causes of these slight differences and 

 the methods of controlling them. 



The usual failure of many blossoms to set and mature fruit is due to 

 many factors, the more important of which are discussed later. It 

 should be understood, however, that many cultivated varieties char- 

 acteristically produce more blossoms than possibly can mature into fruits 

 and that consequently a certain amount of dropping is to be expected. 

 This may be regarded in the same light as the nearly universal abortion 

 of one of the two ovules in the ovaries of most stone fruit varieties 

 or two of the three ovaries in the flower of the date palm — phenomena 

 due to deep-seated hereditary causes that are quite beyond control by 

 any cultural means. 



The June Drop and Other Drops. — All of the flowers that fail to 

 mature fruit do not drop at one time and a continuous dropping from 

 the flowering stage up to the time of maturity is not common. Instead 

 there are more or less definite periods or stages when extensive dropping 

 occurs. The loss comes in a series of waves, varying with the different 

 fruits in number and in the length of time between them. There appear 

 to be certain "sticking points," critical periods, through which each 

 fruit must proceed to reach full maturity. When one of these stick- 

 ing points is safely passed there is comparatively little danger of the fruit 

 falling before the next critical period arrives. Apparently these sticking 

 points for fruit setting are closely correlated with definite changes in 

 the development taking place in the embryo and in the endosperm of the 



Dorsey^^ has made a careful study of dropping of blossoms and newly-set 

 fruits in the plum and the following account, adapted from his report, illustrates 

 the phenomenon as it occurs in fruits in general : 



The First Drop. — The first drop takes place very soon after blossoming. 

 Examination of the pistils of the flowers dropping at this time shows that they 

 are defective. In some, pistil abortion has occurred at an earlier stage than in 

 others though the stage at which it occurs is quite constant for each variety. 

 Pistils show all degrees of development, ranging from mere rudiments up to those 



