SECTION V 

 FRUIT SETTING 



It is customary to speak of the reproductive activities of the plant 

 as distinct from its vegetative activities. That use of terms is accepted 

 and followed here, though it is not always an easy matter to define the 

 two. The woody tissues of the shoot and spur may by common consent 

 be considered vegetative in character. Likewise, it is generally agreed 

 that the ovarian tissues of the fruit may be classed as reproductive, 

 being more intimately associated with reproduction than with vegetative 

 growth. On the other hand, there might easily be some difference in 

 opinion regarding the tissues composing the peduncle or central axis of the 

 inflorescence. In many plants these structures differ but little from 

 other stem structures and they are vegetative in character. On the 

 other hand, when these tissues become fleshy and form an integral part 

 of the developing fruit, as they do in the pineapple, fig and many other 

 fruits, they would as naturally be considered along with the ovarian 

 tissues with which they are so closely associated. Mention is made of 

 these points to emphasize the fact that the problem of fruit setting is not 

 necessarily limited to a consideration of strictly reproductive tissues 

 and reproductive activities. Indeed, the formation of an abscission layer 

 at the base of the ovary, the pedicel or the peduncle is a function of the 

 sporophytic tissue at that point. Consequently it is subject to the same 

 influences, though perhaps not to the same extent or in exactly the same 

 way, as abscission layers developed in other places. However, fruit 

 setting and fruit formation depend on the initiation and successful 

 completion of at least some of the reproductory processes. Therefore, 

 the more important of the processes more or less directly concerned with 

 the setting of fruit are outlined briefly. 



In the great majority of higher plants, fruit and seed formation are 

 conditioned on the bringing together and fusion of two specialized cells 

 known as gametes. The larger of these cells is called the egg and is 

 borne in the embryo sac. The smaller gametes are formed by a divi- 

 sion of the generative nucleus of the pollen grain. The flower is the 

 special organ of the plant for the production of these gametes. More 

 specifically the stamen or microsporangium is the organ for the pro- 

 duction of the male gametes and the ovule or macrosporangium the 

 organ for the production of the female gametes. The great diversity 



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