THE FLOWER AND THE BEE 



to its own and the pollen of the other two. Napoleon when 

 planted extensively yielded little fruit although interplanted 

 with Lambert and Bing. But each of these varieties is effec- 

 tively pollinated by Black Republican, Tartarian, and Water- 

 house. Thus without cross-pollination no sweet cherries can 

 be raised. (Fig. 88, page 181.) 



The early settlers in the prairie States sometimes found 

 native plums growing along the rivers, which were well-flavored; 

 but when they transplanted the trees to their gardens they be- 

 came unproductive. All the varieties of American plums are 

 self -sterile, except the Robinson, and this is not wholly reliable. 

 In the woodlands the different varieties pollinate each other. 

 The Japanese plums are also generally self-sterile. Of the 

 European plums a part appear to be self-sterile, and a part 

 self -fertile; but no satisfactory experiments have been made. 

 According to Waugh, who gave five years or more to the investi- 

 gation of plum-pollination, all the species hybridize, and all the 

 hybrids are self-sterile. The majority of plums do not bear 

 well, and most of them set no fruit at all unless there are two 

 or three varieties. Cross-pollination by insects is here again 

 a necessity. 



Nowhere in the world are there so many wild species of 

 grapes as in the Eastern United States. Foreign grapes do not 

 succeed well in this country when planted outdoors, and com- 

 mercial grape-growing is, therefore, dependent on our native 

 species. Many varieties are self-sterile. Of 169 cultivated 

 varieties investigated by Beach in New York, 37 were wholly 

 self -sterile, as Oneida, Eaton, Salem, and Wilder; 28 were so 

 nearly self-sterile that the clusters were unmarketable, as 

 Brighton, Geneva, Vergennes, and W'oodruff ; 104 varieties pro- 

 duced marketable clusters when self-fertilized, but of this 

 number 66 had the clusters loose and only 38 yielded compact, 



270 



