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 "J une 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 (1) non- 

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

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