THE DEVELOPMENT OF THE FRUIT 529 



Mention has been made of the relation of water deficiencies at blossoming 

 or shortly thereafter to dropping in the Washington Navel orange.'* 

 ]\Iany other agencies that Hmit fruit setting in non-parthenocarpic 

 varieties cause the dropping of those varieties that develop partheno- 

 carpically. In other words, the parthenocarpic condition is only a partial 

 and not a complete insurance against crop failure from premature 

 dropping. 



From a practical standpoint seedlessness and parthenocarpy are to be 

 considered more as varietal characteristics to be sought when breeding 

 or originating new varieties or strains, rather than as conditions to be 

 produced by cultural means. 



The Relation of Seed Formation to Fruit Development. — It has just 

 been pointed out that in some species or varieties ovarian and other 

 tissues of the fruit may develop independently of those of the enclosed 

 ovules. This condition, however, is by no means universal and such 

 parthenocarpic fruits are usually somewhat different in size, shape or 

 other characteristics frcm seed-containing specimens of the same kinds. 

 Furthermore, in the seed-containing specimens important differences in 

 development are often associated with varying seed number and 

 distribution. 



Structure of Fruit. — Evidence that certain tissues of the pear undergo 

 a proportionally greater development in seedless than in seed-containing 

 specimens is presented in Fig. 55. That this is very common in other 

 fruits is indicated by the work of many investigators. Thus in seedless 

 eggplants the outer portions of the fruit grow more rapidly than the inner 

 portions, "the placentae evidently requiring the stimulus of the growing 

 ovules to induce development."^^ In seedless fruits of the eggplant and 

 in those in which the development of the ovary is arrested at an early 

 stage there is sometimes a very marked and abnormal development of 

 the subtending calyx. "Usually the most prominent indication that 

 impregnation has taken place, in the eggplant, is the rapid growth 

 of the calyx. Many times, however, the calyx becomes much enlarged 

 while for some reason the ovary fails to develop. I have frequently 

 seen examples of this, in which the calyx was fully 6 inches long."** 

 Ewerf*2 studied the structure of seedless and seed-bearing gooseberry 

 fruits and found striking differences in their cell size and structure. The 

 cells of the placentae and inner ovarian wall of seed-containing fruits 

 averaged 45-90/i^ in diameter, while many of those in the seedless speci- 

 mens were seven or eight times as large. 



Form. — The pears sho^vn in Fig. 55 are illustrations of changes in form 

 accompanjdng changes in internal structure due to seedlessness. Mun- 

 son*^ observed that the parthenocarpic seedless fruits of English cucum- 

 bers were cylindrical in shape, but that when they were pollinated and 

 seeds developed the apical one-third of each fruit was much enlarged. 



