Pollination 305 



The Domesticas and the Damsons. With respect to 

 the Domesticas, which have been pretty much ignored 

 in the foregoing discussion, a word or two more should 

 be said. The varieties of this group, including also 

 the Damsons, do not seem to be so generally self- 

 sterile as other plums. However, unless a given va- 

 riety is positively known to be self-fertile in the locality 

 where it is to be planted, it would be better to mix it 

 with some suitable pollenizer. In selecting polleniz- 

 ers for Domesticas and Damsons, it would probably be 

 best to choose from the same groups. In the northern 

 states, where alone (excepting in California) these va- 

 rieties are grown, nearly all the Domesticas and Dam- 

 sons blossom so closely together as to make this safe. 



Agencies of pollination. In the plum orchard pol- 

 lination is usually effected by insects, especially by 

 bees, and more particularly by the common honey bee. 

 This one species seems to be far more useful in dis- 

 tributing pollen than all other agencies combined. 

 The wind may do something in the way of carrying 

 pollen. Probably it does at times, though the experi- 

 ments which I have made on this subject have pointed 

 to the contrary conclusion. 



June drop. At this point attention should be 

 called to the phenomenon known among plum and 

 peach growers as the "June drop." It seems to be 

 always the case that a large proportion, from twenty- 

 five to one hundred per cent, of the fruit which appar- 

 ently sets falls off just as it should begin to grow. This 

 fall of young fruits usually occurs within a short space 

 of time, and comes, in medium latitudes, some time 

 in June. 



Various explanations of the June drop have been 

 suggested. The causes usually assigned are (i) non- 

 pollination, (2) curculio work, and (3) the struggle for 



