^06 PROCEEDINGS OF THE ACADEMY OF [Sept., 



barren 'plants grow in the southern part of Staten Island, and that 

 forty-six of them have been detected in Suffolk county, Long Island. 



It would seem that these species have a tendency to follow the course 

 of the two more recent geologic formations throughout their whole 

 extent along the Atlantic coast. Another fact which stands out promi- 

 nently in this connection is that not a single one of the above-mentioned 

 plants, growing, as we have seen, along the edge of the glacial drift, 

 is native of Europe, but belong to a true American flora, which had its 

 origin in the southern part of the continent and migrated northward 

 into Staten Island and Long Island at the close of the great ice age. 

 In contrast to this fact we have another one, equally prominent, and 

 that is, that of the species of plants growing on the morainic material 

 about one-third are common to northern Europe and America, thus 

 pointing to a common origin of each in the territory now occupied by 

 the ice and snow of the Arctic regions. The flora north of the morainic 

 line in Staten Island and Long Island clearly antedates in point of 

 occupancy of the country the more southern and American pine barren 

 flora, wliich migrated northward at a date subsequent to the migration 

 of the flora with strong European affinity. 



Another interesting illustration of the historic factors instrumental 

 in plant distribution is afforded by the peculiar flora of the Kittatinny 

 or Shawangunk mountains of northwestern New Jersey, This moun- 

 tain chain forms a wall of almost constant altitude, averaging over 

 1,200 feet in height, along the eastern side of the Delaware river from 

 Port Jervis to the Delaware Water Gap. Its summits and western 

 slopes are composed of a coarse or fine, very hard silicious conglomerate 

 or sandstone, with little soil but that derived from the limited disin- 

 tegration of these rocks, and it is therefore highly silicious. While 

 the mountain sides are extensively glaciated there is very little glacial 

 drift on the ridge. 



On these mountains exist a number of plants which are also found 

 in great numbers in sandy soil along the Atlantic coast. Among the 

 species which are thus noteworthy, as discovered by N. L. Britton, are: 

 Juncus greenii Oakes and Tuckerm., Solidago puberula Nutt., Orontium 

 aquaticum L., Tephrosia virginiana Pers., Lespedeza hirta Ell., Lupinus 

 perennis L., Quercus ilicifolia Wang., Corema conradii Torrey. At 

 Culver's Gap were found by Britton : Polygala polygama Walt., Gerardia 

 pedicularia L., Lechea racemulosa Michx., all abundant in sandy soil 

 along the coast, and Prumis pumila L. At Sunfish Pond, northwest 

 of the Water Gap, occur Juncus militaris Bigel., Lycopodium inun- 

 datum L., Vibwnium nudum L. While all along the mountains grow 



