496 FUNDAMENTALS OF FRUIT PRODUCTION 



The relation of number or proportion of seeds to the holding of the fruit 

 is discussed in another connection. 



Impotence of Pollen. — It has long been known that many apparently 

 perfect flowered plants produce only small amounts of pollen and that 

 occasionally a considerable portion of that which is borne is non-viable. 

 In fact it is unusual to find pollen that is 100 per cent viable. However, 

 few data have been available as to the proportion of the pollen produced 

 by ordinary fruits under varying conditions that is defective and until 

 recently there has been little realization of the importance of this factor 

 in determining fruit setting and fruitfulness. 



Beach, ^> ^> * was one of the first to investigate this subject carefully 

 as it pertains to deciduous fruits. He found that varieties of American 

 grapes fall readily into three classes in respect to fruitfulness when de- 

 pendent on their own pollen for fertilization. These he called self 

 fertile, self sterile and partly self sterile. The varieties of the partly 

 self sterile group varied from vineyard to vineyard and from season to 

 season in their degree of self sterility, but those of the self fertile group 

 remained completely self fertile; likewise those of the self sterile group 

 remained completely self sterile. Controlled cross pollination experi- 

 ments led to the conclusion that the partial or complete self sterility of 

 those two groups was not due to any defect in the pistils but to impotence 

 in their pollen, though an abundance of it was formed. The stamens of 

 the self fertile varieties were erect, while those of the self sterile sorts were 

 reflexed. A detailed study of the pollen of these different classes showed 

 marked differences in the shape and appearance of the grains.^ Those 

 of the self fertile varieties were oblong, blunt at the ends and quite sym- 

 metrical and they germinated well ; those of self sterile sorts were irregular 

 in shape and did not germinate well. Stamens of the partly self sterile 

 varieties were found to contain some good and some poor pollen. 



A little later Reimer and Detjen^'" reported that all the varieties of 

 the Muscadine grape bear reflexed stamens only and that all their pollen 

 is defective. Their flowers are pseudo-hermaphrodites rather than true 

 hermaphrodites. For fruit to set the pistils must receive pollen from 

 male or staminate vines. The plants of this species are essentially dioe- 

 cious. Failure to recognize this fact has been responsible for much of 

 the unfruitfulness previously encountered in the culture of this group of 

 grapes. Among the plants growing wild about three-fourths are stami- 

 nate and one-fourth pseudo-hermaphroditic with functional pistils.^* 

 More recently there have been found ^^ ' '^^ several plants of this species 

 producing true hermaphrodite flowers; these have afforded a starting 

 point for the breeding of a new and perfect flowered race of Muscadine 

 grapes. 



Apparently the failure properly to set and mature fruit occasionally 

 found in European varieties of grapes is likewise due at least partly to 



