112 THE PLUMS OF NEW YORK. 



able, for several days and the pollen from all anthers is not shed at once 

 and is produced with such seeming prodigality as to almost insiire the 

 retaining of a sufficient amoimt to pollinate late-maturing stigmas. In 

 view of these considerations, premature or retarded ripening of either pistils 

 or stamens does not seem of great significance in the setting of fruit 



From the statements just made it may be seen that the main cause 

 of the failures to set fniit when trees bloom freely must be ascribed to the 

 faikrre of pollen to fertilize the pistils of the flowers of the same variety. 

 The solution of the problem of self -sterility in the main, then, is to so 

 plant that varieties will be mutually cross-fertilized. In the selection of 

 varieties for such cross-pollination two factors must be considered, simul- 

 taneity of blossoming and sexual affinity. 



It is evident, if cross-fertilization is to play an important part in 

 fruit-growing, in planting to secure it kinds must be chosen which come 

 into blossom at the same time as those they are expected to fertilize 

 The table on pages io6 to 109 shows the sorts that bloom together or 

 nearly enough so to make cross-pollination possible. It will be found 

 upon examining the table that, under normal conditions and during the 

 average season, varieties of any one species overlap siifficiently for the 

 above ptupose imless it be the very early and very late varieties. Varia- 

 tions due to locaHty and to season must be expected but within the boimds 

 of New York these will be slight. If the table is used for other regions 

 than New York it must be borne in mind that the farther south, the longer 

 the blossoming season; the farther north, the shorter the season. Prop- 

 erly interpreted the table of dates should be a useful guide as to the simul- 

 taneity of blooming. 



Varieties of pltims seem to have sexual affinities. That is, some varie- 

 ties will fertilize each other very well and some will not, even though they 

 belong to the same species. There seems to be Httle definite know^ledge 

 as to the sexual affimities of plums and it is not, therefore, possible to lay 

 down exact rules for the selection of poUinizers for individual varieties. 

 In the current discussions of cross-pollination it is probable that the im- 

 portance of " affinities " is over-rated, and yet the subject is worthy of 

 consideration. Waugh and Kerr have given this subject considerable 

 attention for native and Japanese plums and have recommended a list 

 of pollinizers for the several species.' The Domesticas and Insititias, the 



' Waugh, F. A. Plum Cult. 297-300. 1901. 



