FRUIT FORMATION 483 



important in determining whether or not the fruit shall matm-e or fall 

 prematurely. 



In the developing seeds of most species the tissues of the nucellus 

 disintegrate and their substance is used by the growing endosperm or 

 embryo. In some species, however, the nucellar tissues persist and develop 

 into a storage tissue that can hardly be distinguished from endosperm. 

 Storage tissue of such origin is known as pcrisperm. 



THE SETTING OF THE FRUIT 



The fertilization process and the following segmentation and growth of 

 the embryo and endosperm within the ovule are accompanied b}^ changes 

 in the surrounding ovary wall and often in the torus and other adjoining 

 tissues. Most noticeable among these changes is a thickening and an 

 increase in size, perhaps with some change in color, shape and position, 

 so that it is evident very soon after blossoming that the fruit has or has 

 not "set," or that there is or is not a possibihty of its maturing properly 

 in due time. 



However, some blossoms do not set fruit and sometimes the percentage 

 that sets is extremely small. Nothing is of greater importance to the 

 fruit grower than having a reasonable percentage of the blossoms set. 

 Yield, income and profits are all absolutely dependent on what the tree 

 does in this respect at and just after the time of blossoming. Of course 

 accidents or unfavorable conditions later in the season may injure or 

 destroy the crop, but they are contingencies with which the grower has 

 greater confidence in dealing than the accidents that may befall at the 

 time of fruit setting. 



The term "fruit setting" is used here to refer to the initial and appreciable 

 swelling of the ovary occurring shortly after the period of petal fall. It is gener- 

 ally accompanied by some thickening of the pedicel or of the peduncle. Meanwhile, 

 flowers that have not " set " are turning yellow or withering and faUing off. After 

 this stage is passed accidents may happen and the "June drop" or some other 

 "drop" or some environmental factor may cause abscission; nevertheless, at 

 least for the time being, it appears as though fertilization had taken place and 

 the chances are good for the fruit maturing. 



What Constitutes a Normal Set of Fruit. — It is not to be expected that 

 all the blossoms will set fruit, even though conditions are ideal. In most 

 species and varieties they are produced in such profusion that a total set 

 would be little short of calamitous for the grower. He is more interested 

 in obtaining a reasonable number of specimens of good marketable size 

 than a much larger number of a size for which there is little demand. 

 Furthermore, he prefers a crop such as the trees can mature without 

 undue exhaustion, for then he is surer of crops the following years. 



