HORTICULTURE. 



599 



and observations upon plums by Bailey^ and Heidemau indicate the 

 necessity of cross pollination for this fruit also. 



The author believes that each of the six modifications of the typical 

 flower by which cross pollination is insured and self-fertilization pre- 

 vented may exist in jjlum blossoms, particularly in varieties of the 

 Americana group, but does not consider any variation of great signifi- 

 cance except that of defective pistils. Figures are given showing 

 typical pistils of 12 varieties of plum and comparisons of sound and 

 defective pistils of Primus amerieana. About 2,000 plum blossoms 

 were examined and compared as to percentage of defective instils and 

 relative abundance of pollen production. The data are shown in the 

 following table: 



Percentage of defective pistils and abundance of pollen in plum hlossoma. 



^'From this it appears that about one-half of the pistils of the Marianna were 

 defective ; over one-fonrth in Primus amerieana (the common wild plum), only a little 

 less in Prunus hortulana (tlie Wild Goose grouji), about one-sixth in the Chicasaws 

 and Japanese plums, and only one-twentieth in the European varieties {Prunus 

 domestica). The great discrepancy between the wild forms of the typical Prunus 

 amerieana (mostly Western) and the variety nigra (mostly Eastern) is a point of 

 considerable interest. . . . 



"Different varieties vary greatly in the amount of pollen produced. This varia- 

 tion seems also to follow somewhat the specific parentage of the varieties. Thus 

 plums of the Americana group are generally more abundant pollen bearers, though 

 they seldom show serious deficiency. The Japanese plums are still weaker, while 

 the Marianna is distinctly lacking in quantity and perhaps also in the quality of 

 pollen produced." 



In connection with the estimates of pollinating efficiency the author 

 notes the facts that such estimates must be very rough, that there is a 

 very decided difference in the quality of pollen, and that pistils of 

 many varieties api)ear to have a pronounced selective ability for pollen; 

 so that care must be exercised in drawing conclusions. 



To gain some evidence as to the theory advanced by Goff^ that the 

 severity of Northern climates accounts for much of the defectiveness 

 of i)istils, a tabulation by sections is made of the varieties examined. 

 The results do not sustain the theory as, except at one location which 



'New York Cornell Bui. 38, p. 43 (E. S. R., 4, p. 164). 

 3 Minnesota Hort. Soc. \i\\t., 1895, p. 187. 

 3 Wisconsin Sta. Rpt. 1894, p. 350. 



