A STUDY IX PLAXT VARIATION 237 



Cod, Mass. to Lincoln County, N. C. The collections include the 

 following places: — Falmouth and Nantucket, Mass., Oyster Bay, Long 

 Island, and in New Jersey, at Island Heights Junction, Sea Side Park, 

 Barnegat, Manasquan, Manahawkin, Brigantine Beach, Pleasantville, 

 Ocean City, North Wildwood, Manumuskin, Maurice River and Cape 

 May Point. The latter place was the most favorable for collection 

 and study, as all the different varieties grow there, thus enabling me to 

 compare them all in a single day. 



Just across the bay from Cape May in Delaware, Pnuius maritima 

 var. pygmaea is reported; specimens of w^hich can be seen at the Academy 

 of Natural Sciences, Philadelphia, and which were collected at Rehoboth 

 and Lewes, Delaware. It is characterized by smaller and more narrow 



leaves. 



Pruniis pygtnaea, a specimen of which can also be seen at the Acad- 

 emy, and which resembles Prumis maritima var. pygmaea from Delaware, 

 has been collected in Lincoln County, N. C. The specimen at the 

 Academy is very old and shows only a few leaves. 



(2) Inland 



About forty miles inland and running almost parallel with the present 

 shore line of New Jersey, beginning at a point near Salem, and extending 

 in a northeasterly direction to near Brown's Mills, occur local isolated 

 patches of Prunus maritima. Along this line, I have collected material 

 at Hainesport, Medford, Clementon and Atco. While I have not col- 

 lected any material, nor on my numerous excursions to the shore have 

 I seen it growing in the Pine Barren region, yet it is reported by others, 

 e.g. Stone (27), as growdng there. This distribution is quite unusual 

 as it is the only region, as far as I have been able to learn, where it is 

 found growing so far from the sea. The question naturally arises why 

 this distribution. 



It has been suggested that birds or Indians may have carried them 

 there. But the distribution of plants is now generally regarded as 

 being connected with climatic or ecologic factors, it occurred to me there- 

 fore that a geologic explanation or suggestion at least was possible. 

 The soil at Clementon and at Atco, where these plants grow, is composed 

 of a light colored loose sand resembling in every respect our present 

 beach sand. The rounded surfaces of the grains indicate that it is water 

 worn. Occasionally the soil may be firm where strata of clay approach 

 and form the surface. Most geologists regard this formation as Miocene. 

 A few miles to the west is found the green sand marl or glauconite of 

 the Upper Cretaceous. The marked character in the color of the sand 



