THE HORTICULTURAL SOCIETY OF NEW YORK 



Rhode Island Greening Apple and in many other varieties of these 

 fruits. Each of these has perfect flowers with stamens fully de- 

 veloped and with pollen highly potent. Each is known to be 

 capable of yielding heavy crops of fruit. There are no marked dif- 

 ferences in the time of the development of the pistils and stamens 

 of the individual flowers. The flower mechanism does not prohibit 

 self-pollination even without insect visitations, but with such visita- 

 tions close-pollination is amply provided for. And yet these self- 

 and close-pollinations are not effective in fruit setting. There is 

 what we may call an incompatibility in the processes of fertiliza- 

 tion which follow pollination. Interplanting is hence necessary 

 to provide for the pollinations which do result in fcrtilisati' u. 

 But there may also be cross-incompatibilities : twu well-known 

 varieties of sweet cherries, the Bing and the Napoleon, are re- 

 ported to be not only self -incompatible but cross-incompatible as 

 well. 



It is to be noted that incompatibilities are not to be deter- 

 mined by an examination of the flower, or by any laboratory tests 

 of the pollen, as pollen sterility in intersexes may often be de- 

 termined, but only by the results of properly controlled pollinations 

 combined with the results obtained in orchard plantings. 



It is now evident that many varieties of Apple, Pear, Cherry, 

 Plum, Blackberry, Almond, and Feijoa are self-incompatible to 

 some degree. Certain varieties of these fruits, of which the 

 Wealthy apple may be mentioned, appear to be rather highly self- 

 compatible, but in many cases even these varieties will produce 

 larger yields of better fruit when there is cross-fertilization. 



During the past ten years, especially, evidence has been accumu- 

 lating as to what varieties of our fruits are or are not self-fruitful. 

 The evidence is very often conflicting and this has been accepted 

 by most horticulturists as proof that "self-sterility is not a constant 

 factor in any variety." It is said that "the same tree may be self- 

 sterile at one time and self-fertile at another or the same variety 

 may be self-fertile in one locality and self-sterile in another." 

 Such behavior is credited to important varieties as the Kieffer and 

 Bartlett pears and the Yellow Newton and Rhode Island Greening 

 varieties of apples. No doubt in many instances other causes of 



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