266 PENNIT ACKER— ON THE BEACH PLUM 



V. Summary 



The following summarizes the body of new facts obtained by the 

 writer during the present investigation. 



1. While P. maritima is typically a seaside plant that grows in loose 

 sandy soil, there are inland localized areas along the eastern sea board 

 where it occurs. These probably represent isolated, and stranded patches 

 of individuals, left from shore lines that once existed in previous geologi- 

 cal periods. 



2. While the average blossoming period has been determined to be 

 the 2d of May, varieties are observed along shore lines where they are 

 exposed to sweeping sea breezes and which do not open until May 15th. 



3. The most noteworthy characteristics of P. maritima are shown by 

 the writer to be its marked variation in size, in mode of branching, and 

 in vigor of the shoots; in time of appearance, in size and in hairiness of 

 the leaves; in size and in color of the petals, as well as in their blossoming 

 before, during, or after the commencing expansion of the foliage leaves. 

 The above is in line with the extreme variability of the fruits as already 

 noted by previous observers, and would suggest that the species is under- 

 going marked mutational variations. 



4. The flowers are shown to be andro-dioecious and this evidently 

 affords a key to the conditions seen in autumn when some bushes are 

 fruitless, others sparsely fruitful, and still others bear abundantly. The 

 practical value of this observation in connection with possible future 

 cultivation by man is evident. 



5. As a rule, those bushes which bear the darker or deeper colored 

 fruits of purple and blue tint have a general purplish color that extends 

 even to the petals and stamens. 



6. Interesting petiolar glands have been found to occur near the 

 junction of the petiole with the lamina as well as laminar tooth-glands. 



7. A concave nectary lines the interior of the receptacular cup that 

 surrounds the pistil and this excretes a large amount of nectar. 



8. The writer confirms the views previously expressed regarding the 

 striking variability and resulting types of the fruit. 



9. The extreme variation in size, shape, and weight of the stones in 

 the different varieties has been determined and compared. 



10. The variation forms in this highly variable plant recognized by 

 the writer have been grouped under nine heads, each of which has been 



