Pollination 307 



there immediately begins a strenuous struggle for ex- 

 istence. There is not room for all. The strongest 

 only can survive. The weakest are soon robbed of 

 their share of nourishment and are presently literally 

 crowded off the stems by their jostling brothers. This 

 struggle is severest in the latter part of May and the 

 early part of June, and the rejected weaklings figure 

 conspicuously in the June drops. The struggle is less 

 of course as the setting of plums is smaller and its in- 

 tensity is influenced more or less by other causes, as 

 food supply and the operation of the two causes of 

 drops already considered. 



Leaving aside the drops which immediately follow 

 the falling of the blossom and which are not June 

 drops, the three causes enumerated usually operate in 

 the following order: Non-pollination, struggle for ex- 

 istence, curculio work. The effects of the curculio 

 work are thus apt to occur after other causes have re- 

 duced the crop to what the trees could comfort- 

 ably carry. 



The plum grower may therefore leave out of con- 

 sideration the struggle for existence. He need not 

 worry about non-pollination except in those cases of 

 self-sterility and improper adjustment of varieties 

 which would come to his attention without reference 

 to the June drop. He should, however, give serious 

 attention to the curculio, for it is this factor which 

 may oftenest reduce a fair crop to none at all. 



