A STUDY IN PLANT VARIATION 267 



given a definite varietal name, and all of these tend to appear in regions 

 where the Beach Plum grows from Cape May Point to Cape Cod pen- 

 insula. 



11. The primitive color was probably greenish yellow or greenish red. 

 Through increasing transformation of the chlgroplasts into bright 

 chromoplasts pure yellow fruits were secured along one evolutionary 

 Une; through development of a red, purple and eventually blue color the 

 chloroplasts became concealed, and so the climax of combined size and 

 color evolution was reached in the large blue black. 



12. Many bushes belonging to several varieties, particularly the 

 small blue black and the small purple, are often destructively punctured 

 by a weevil during the early stages of fruit maturation, or about two 

 weeks after the flowering period. This produces a hardened protective 

 secretion rich in tannin but which causes deteriotation in the quaUty 

 of the fruit. 



13. While the purple and the blue black fruits are often rich in tannin, 

 the yellow fruits are comparatively poor in this. 



14. The Beach Plum, like the cultivated plum, {P. insititia) and the 

 Sand Cherry {P. Besseyi), is a mutational species, which through the 

 agency of environmental factors, that are still hard to determine accur- 

 ately, is undergoing change in individual plants, not along one but along 

 several lines of variation. 



15. The author agrees with the views put forth by Macfarlane as to 

 the possible high economic value of the shrub for the future in its dif- 

 ferent varieties. He also records the interesting hybridizing experi- 

 ments of Burbank with the present species and the Japanese Plum {P. 

 triflora), as holding out hopes for origin of many new forms by hybridi- 

 zation. 



