374 BOTANY OF CROP PLANTS 



Parthenocarpy. — ^As a general rule, lack of fertilization of 

 the ovules in the ovary is followed by the shedding of the 

 blossoms; the ovary fails to develop completely if a good 

 number of its ovules are not fertiUzed. However, develop- 

 ment of the ovary does sometimes occur although fertiliza- 

 tion fails. Such an unusual development of carpels is called 

 parthenocarpy. This phenomenon is not unknown in the 

 apple. With certain sorts of both apples and pears, fruits 

 weighing loo grams have been developed without fertiliza- 

 tion. Of course, parthenocarpic fruit is seedless. There are 

 among cultivated plants many which bear seedless fruit. 

 We noted that in the common Mission figs the fruit matures 

 normally without fertilization of the ovules. Seedless to- 

 matoes, egg plants, English forcing cucumbers, oranges, 

 grapes, and bananas are quite common. 



The Fruit and Its Development. — Morphology. — There 

 are two common opinions as to the nature of pomaceous 

 fruits: 



1 . Flesh is thickened calyx tube. 



2. Flesh is receptacle or torus closely connected with the 

 carpels. 



The recent work of Kraus appears to establish the latter. 

 In following through the development of the flower (Fig. 

 155), it is seen that the receptacle, by more rapid growth at 

 the sides than toward the center, becomes urn-shaped and 

 bears on the rim and inside face, calyx lobes, petals, and 

 stamens. In the development of the fruit, there is a con- 

 tinuation of the enlargement of the receptacle ; the throat of 

 the receptacle becomes narrow, and through it the styles pro- 

 trude; and the connection between receptacle and carpel 

 tissues becomes a very close one; hence receptacle makes up 

 the greater portion of the flesh of the apple. 



Ripening Process. — Important chemical changes take place 



