110 THE PLUMS OF NEW YORK. 



THE POLLINATION OF PLUMS. 



One of the discouragements in plum-growing is the uncertainty which 

 attends the setting of the fruit in some varieties even though the trees 

 bear an abundance of blossoms. Blooming, the prelude of fruiting, had 

 little significance to the fruit-grower until the discovery was made that 

 many varieties of several fruits were unable to fertilize themselves and 

 that failures of fruit crops were often due to the planting of infertile varie- 

 ties. Investigations as to the self -sterility of pears, plums and grapes have 

 shown blossoming-time to be one of the most important life periods of these 

 fruits. The knowledge obtained by workers in this field has to some degree 

 modified the planting of all orchard-fruits and of none more than of the 

 plums. Indeed, it is held by many that it is hardly safe to plant any 

 excepting the Domestica and Insititia plums without provision for cross- 

 pollination. 



A variety is in need of cross-pollination when the pollen from its own 

 blossoms does not fecundate the ovules of the variety. There is a delicate 

 and complicated procession during the process of fruit formation and 

 the life of the fruit may be jeopardized by any one of a number of external 

 or internal influences. These deleterious influences are most often unfav- 

 orable weather or defects in the reproductive organs of the plants them- 

 selves. Of the latter, in the plum there are several rather common ones 

 which cause self-sterility, as impotency of pollen, insufficiency of pollen, 

 defective pistils and difference in the time between the maturity of the 

 pollen and the receptiveness of the stigmas. 



It is held that the main cause of the infertility in plums is impotency 

 of pollen on the pistils of the same variety. The pollen may be produced 

 in abundance, be perfect as regards appearance, and potent on the pistils 

 of other varieties but wholly fail to fecundate the ovaries of the variety 

 from which it came. The most marked examples of such impotency are 

 to be found in the native plums though the Triflora sorts are generally 

 accredited with being largely self -sterile and the Domesticas somewhat so. 

 The proof offered to show the impotency of plums is for most part the 

 records of fruit setting under covered blossoms. In this method of testing 

 the impotency of pollen there are several sources of error and the figures 

 given by experimenters probably greatly exaggerate the infertility of 

 plums, but since the experience of plum-growers generally affirms the 

 results in some measure it is well to hold that the native plums at least 

 should be so planted as to secure cross -pollination. It is doubtful if the 



