THE HORTICULTURAL SOCIETY OF NEW YORK 



The recent advances in the knowledge of such diseases now make 

 it very doubtful if vegetative propagation of itself ever leads to 

 the "running out" of a clonal variety. The selection of healthy 

 stocks in the various plants in which there may be yellows or mosaic 

 disorders is becoming well recognized as a necessary procedure. 



Rather special studies are needed to determine the nature of 

 these diseases, the means of their transmission, and the methods of 

 eliminating them in practical culture. Thus at the beginning the 

 solution of these problems rests on the shoulders of the specialist 

 in plant pathology. It remains, however, for the nurseryman and 

 the grower to practice the means for control. 



FRUIT PRODUCTION IN CLONAL VARIETIES 



The horticulturist needs always to know when the growing of 

 a clonal variety in solid blocks will of itself reduce fruit produc- 

 tion through limiting the pollination required for the setting of 

 fruit. It is the rule among the fruit crops grown at the present 

 time that proper production of fruit depends on the development 

 nf seed. But the initiation of seed development depends (with 

 few exceptions) upon intricate processes of fertilization which in 

 turn depend upon a proper pollination. It happens that there 

 are frequently special conditions that are inherent characteristics 

 of certain clonal varieties which limit or prevent either pollination 

 or fertilization after pollination whenever a plant stands alone or 

 when there is a solid block of a single clonal variety. 



There are so many conditions influencing the production of fruit 

 that it is not always an easy matter to distinguish between those 

 th.at are incidental, or purely environmental or cultural, and those 

 which pertain to the needs of a variety for pollination. The for- 

 mer operate to limit production when all requirements for pollina- 

 tion are met. The latter operate to limit fruit bearing where all 

 environiriental conditions are fully favorable to high yields. The 

 manifold and complex influences of climate, weather, culture, 

 nurture, fungous diseases, insect pests, etc., are all of vital and im- 

 mediate effect. They have always been matters of much concern to 

 fruit growers. They always will be of much concern. But these 

 are not factors for unfruitfulness that develop or become promi- 



66 



