THE PLUMS OF NEW YORK. 9 



The reproductive organs of plums afford several characters and would 

 seem to ofifer means of distinguishing botanical and horticultural groups, 

 but they are so variable in both cultivated and wild plants as to be very 

 misleading. Not only do these organs dififer very often in structure but 

 also in ability to perform their functions. Bailey ' has called attention 

 to the remarkable self-sterility of some varieties of the native species of 

 plums, due to the impotency of the pollen upon flowers of the same variety. 

 C. W. H. Heideman' made some very interesting observations on what 

 he considers distinct forms of the flowers of the Americana plums, de- 

 scribing for this species all of the six possible variations of flowers entime- 

 rated by Darwin in his Different Forms of Flowers in Plants of the Same 

 Species. Heideman thinks that other species of Prunus exhibit similar 

 variations. Waugh' made the pollination of plums a subject of careful 

 and extended study and found much variation in the ])istils of plants of 

 the same species, insufficient pollen in some plants, pollen impotent on the 

 stigma of the same flower, and considerable difference in the time of maturity 

 of pollen and stigma in some plums, especially the Americana plums. 

 These variations, most important to the plum-grower, are of more or less 

 use in identifying plums. 



After the discussion of the characters of plums we may pass to a de- 

 tailed description and discussion of the species of plums which now con- 

 tribute or may contribute cultivated forms to the pomology of the country- 

 cither for their fruits or as stocks upon which to grow other plums. The 

 following conspectus shows as well as may be the relations of the species 

 of plums to each other. 



CONSPECTUS OF SPECIES OF PLUMS. 

 A. Flowers in clusters of i or 2. (Three in P. triflora.) Old World plums 

 B. Leaves drooping. 



C. Shoots and pedicels pubescent. 

 D. Flowers mostly in twos. 



E. Fruits large, more than i inch in diameter, 

 variable in shape, often compressed ; tree 



large; stamens about 30 i- P- domestica. 



E.E. Fruit small, less than i inch in diameter, 

 uniformly oval or ovoid; stamens about 25; 

 tree small, compact 2- P- insititia. 



' Bailey, L. H. Cornell Sta. Bui. 38:43. 1892. 

 'Heideman, C. W'. H. Minn. Ilort. Soc. Rpl. 187. 1895. 

 •'Waugh, F. A. Vt. Sta. But. 53. 1896. 



