536 FUNDAMENTALS OF FRUIT PRODUCTION 



good seeds. In other words, it is crossing so as to secure a good comple- 

 ment of seeds, rather than crossing with some particular variety, that is 

 responsible for the difference in size and is consequently important in the 

 orchard. Investigations conducted with many fruits indicate that the 

 number or percentage of seeds developing in the fruits of different kinds 

 is to a considerable extent a varietal characteristic or at least it is 

 more dependent on the variety and the condition of the tree or plant 

 than on the kind of pollen, assuming that an adequate supply of good 

 pollen is available. 



Kraus^^ has pointed out that the occasional striping of self colored 

 fruits of the apple, so often cited as proof of an immediate influence of the 

 pollen on the character of the resulting fruit, is in reality a special form of 

 bud mutation. Bud mutations of this kind may in many cases be propa- 

 gated vegetatively and striped varieties obtained. 



What appears at first as an exception to some of the preceding statements 

 has been recorded for the developing fruits of the vanilla. McClelland'^ crossed 

 two types of this plant — Vanilla planifolia and the "vanillon" type. "The 

 typical well-developed fruit of V. planifolia from a close-fertilized blossom is a 

 long slender capsule tapering at the stem end but carrjdng its fullness well down 

 toward the blossom end. It contains thousands of tiny, oily, black seeds. 

 . . . The fruits [of the vanillon type] are much thicker and shorter . . . 

 and differ in being of a more uniform thickness near the two ends, the blossom 

 end frequently being rather tapering. Where to either the V. planifolia or the 

 vaniUon stigma pollen of the other has been applied a very marked modification in 

 the form of the fruit has resulted." These differences in shape apparently are 

 associated with the location within the capsule of the ovules that were fertilized 

 and develop into seeds. When V. pla^iifolia pollen is used on vanillon 

 stigmas, fertilization takes place mainly toward the apical end of the ovary and 

 not toward the basal end, while in self pollenized vanillon stigmas fertiliza- 

 tion occurs clear to the bottom of the ovarian cavity. On the other hand, the 

 pollen tubes of the vanillon type seek the basal ovules in the ovaries of the 

 V. planifolia type when that crossing is made. In reality, instead of being an 

 exception to the statement that crossing with a particular kind of pollen affords 

 no direct influence on the character of the resulting fruit, this is but another 

 instance of an indirect effect on shape, the direct relationship being between 

 kind of pollen and seed number in the one case and seed number and location 

 and shape of fruit in the other. 



Summary. — Ordinarily the development of the carpellary and other 

 tissues of the fruit depends on fertilization and the consequent develop- 

 ment of seeds from the ovules. In some cases, however, the development 

 of the fruit may proceed without an accompanying growth of seeds, or 

 even without the stimulus of fertilization. In still other cases develop- 

 ment may occur in the absen.ce of pollination. Parthenocarpy is a term 

 used to cove-r those cases of f-ruit development in the absence of fertiliza- 



