246 PENNYP ACKER— ON THE BEACH PLUM 



Color. The red, purple, and blue colors seem to be due to one or 

 more pigments added to the yellow color. This became apparent when 

 I added a dilute solution of NaOH to the skin of the red variety. The 

 red dissolved pigment was readily attacked by the alkali and quickly 

 changed its color to purple, to green and finally to yellow. Small yellow 

 chromatophores were easily distinguished after the disappearance of 

 the dissolved pigment, and the pulp, which was treated in a simi- 

 lar manner, though containing only a small amount of pigment, 

 had the same general appearance as the yellow variety. This seems 

 to prove, as far as color goes, that the yellow is the more primitive t>^e 

 and that the red has taken on an added pigment. In the purple and in 

 the blue varieties there appears a sub-epidermal layer which in addition 

 to the red dissolved pigment (same as in the red varieties) gives to the 

 fruits their respective colors. This pigment is contained in small oval 

 or rod shaped bodies which are considerably smaller than the cells which 

 contain the red dissolved pigment. The skin of the purple and of the 

 blue varieties resembles the skin of the red after the inner pigmented 

 layer has been removed. This further emphasizes the fact that the 

 yellow is the more primitive type, since the purples and the blues have 

 evolved from the reds by the increasing alkalinity of a dissolved red 

 pigment, and again the reds have evolved from the yellows by the for- 

 mation of a dissolved acid pigment, and the disappearance of the yellow 

 color from the chromatophore. To say that these varieties overlap, 

 and that the colors grade into each other i.e., that the purples grade 

 into the reds on one side, and into the blues on the other, may appear 

 to weaken the value of the varietal characters given later. But when one 

 considers the sum total of varietal characters typical of each fruiting type, 

 the distinctions above indicated for the fruit seem to hold fairly well 

 for other parts, and to constitute sufficiently stable diagnostic differences. 



The majority of the fruits in any one locality are of the dark blue 

 variety, and comprise about 75% of all the plants. The yellow is the 

 least common and forms about 1%, the reds about 5% and the purples 

 not over 20%. The only locality where I have seen the yellow variety 

 growing was at Cape May Point, although it has been reported as grow- 

 ing at Island Heights Junction, N. J., and at Falmouth, Mass. The other 

 varieties are quite common and can be found in almost any locality 

 where the Beach Plum grows. 



The earliest ones to ripen are the small blue var. praecox, which are 

 fully matured by August first. These, as I have noted earlier in this 

 paper, blossom about ten days earlier than any of the other varieties. 



