Pollination 285 



ough pollination, supposing the pollen to be efficient. 

 In the more usual cases in which the stigmas mature 

 first, it seems that an unpollinated stigma may remain 

 receptive for a considerable time. In the case ob- 

 served, where the stigmas were out five days ahead of 

 the anthers, they remained sticky to the end of the 

 time, were eventually pollinated, and bore an abundant 

 crop of fruit. Difference in time of maturity, there- 

 fore, does not seem to be the point of greatest practical 

 consequence. 



Impotcncy of pollen. — Here is where the trouble 

 lies. It is found that the pollen of Wildgoose, for ex- 

 ample, though perfectly capable of fertilizing almost 

 any other variety which it reaches, is absolutely 

 useless in fecundating its own blossoms. What is 

 true of Wildgoose is true of almost all the other 

 plums derived from native species, and of many 

 others. 



It has already been said above, in various connec- 

 tions, that the native plums are nearly all self-sterile. 

 Robinson is the only exception to this class which I 

 have found in extensive experiments carried on now 

 for five years. Even Robinson does no* seem to be 

 thoroughly reliable in self-pollination. The Japanese 

 plums seem to be generally self-sterile in the same way. 

 Several of the Domestica plums seem to be self-fertile, 

 and several seem to be self-sterile. No satisfactory 

 experiments with them are on record. Under the cir- 

 cumstances it is best to hold them all in doubt. All 

 the hybrid plums, so far as I know, — and I have tested 

 a number of them, — are also self-sterile. 



We are reduced to this conclusion, then, that, 

 while various plums may sometimes be capable of self- 

 fertilization, they are so nearly always self-sterile that 

 it is. the part of wisdom to act in all cases as though 

 self-sterility were certain. Plums should always be 



