244 PENNYP ACKER— ON THE BEACH PLUM 



anthers are two lobed and bear numerous triangular-shaped pollen grains. 

 The flowers are apparently proterogynous, since the stigma matures 

 before the flower is fuUy open and may easily be seen protruding between 

 the petals of a partly opened flower bud, but homogamy is probably 

 not uncommon. The style projects in the middle of the flower beyond 

 the obUquely diverging stamens, and is 10 to 20 mm. long. The ovary 

 is one celled and characterized by two pendulous ovules. Frequently 

 the flowers are andro-dioecious which would account for the profusely 

 abundant blooms matured on every bush during April and May, and 

 also for the total lack of fruits on some bushes, the rarity on others, and 

 the extreme abundance on still others. The last noted would naturally 

 be those that developed stamens and a well formed pistil with swollen 

 ovary and elongated style. At Hainesport, N. J. the writer has observed 

 bushes for three years, during which time they have never set fruit, yet 

 have constantly bloomed in great profusion. The same condition pre- 

 vails in other locahties. The flowers are insect pollinated as is indicated 

 by the vast horde of Hymenoptera which frequent them during the warm 

 part of the day. The showy white corolla and the nectary are the 

 chief attractions for insects as the flowers are practically odorless. Cross 

 pollination is favored by most writers, and such a view seems Ukely 

 from the fact that the bee in order to obtain the nectar must get far 

 into the interior of the flower. In so doing it seems hardly possible 

 for it to miss touching the stigma. 



Knuth states that automatic self-pollination appears regularly to 

 take place in hermaphroditic flowers of the Pruneae should insect visits 

 fail. Whether this is effective or not seems doubtful, as Kirchner states 

 that numerous bushes observed by him rarely set fruit. The true ex- 

 planation, however, seems to be found in the andro-dioecism as described 

 above by the writer. 



4. Fruit 

 The fruits exhibit by far the most striking variation to the eye, 

 and it was this variation which caused Dr. Macfarlane (18) to first 

 make a preliminary study of the Beach Plum. As I have inferred under 

 materials and method, I began making observations and collecting 

 material when the bushes were in fruit as the variation at that time 

 was the most easily recognized. The fruit, which is usually produced 

 in large quantities, is borne on the younger branches mostly of the 

 previous year's growth. They begin to ripen about the first of August 

 in the earlier varieties and continue to produce an abundance of fruit 



