INTRODUCTION 21 



there mingling with the then native flora, which in the case of the 

 pine-barrens was isolated upon the Beacon Hill formation. 



32. If, as seems probable, no very great refrigeration took place 

 in this area,* it is within the realm of probability that the pine- 

 barren vegetation existing then on the Beacon Hill formation 

 was not very seriously disturbed climatically. We have geological 

 evidence that this area was never subjected to any deposition 

 of glacial material or over- wash; it contains no glacial terraces, 

 for its elevation, perhaps greater then than now, precluded this. 

 But the region surrounding Beacon Hill was in no such fortunate 

 position. Having only recently emerged, comparatively, and 

 boasting only a meager altitude it was more or less overrun with 

 the material from the ice. The glacial terraces of the lower 

 Delaware, the nature of the material deposited near Cape May and 

 in Cumberland County all point to a local, or widespread subsi- 

 dence of the region, which, however, did not affect the Beacon Hill 

 formation as far as possible glacial influence is concerned. Fur- 

 thermore, there is evidence in the sunken forests at Cape May 

 mentioned above, and in the character of the present vegetation, 

 of the effects of the encroachment of glacial material from the 

 north, by way of the Delaware Valley. 



33. In the region of these glacial terraces of the lower Delaware 

 Valley and near Cape May, a few northern plants have been 

 collected that seem to argue their glacial or at any rate northern, 

 origin. Among the following list it is doubtful if any of the species 

 are truly wild in the pine-barrens, but they have all been detected 

 by Dr. Stone at Cape May. 



Botrychium virginianum, Veratrum viride, 



Calamagrostis canadensis, Uvularia perfoliata, 



Trisetum pennsylvanicum, Allium canadense, 



Poa brachyphylla, Blephariglottis lacera, 



Panicularia septentrionalis, Blephariglottis peramoena, 



Carex Buxbaumii, Corallorhiza odontorhiza, 



Arisaema Dracontium, Peramium pubescens, 



* This is a conclusion warranted by our knowledge of modern glaciers. While the 

 refrigeration must be very great near the source of glaciers, it is a well-known fact that 

 at the edges, refrigeration diminishes greatly, particularly where the ice is thin, as it was 

 in all probability near the moraine in New Jersey. It is a common characteristic of 

 glaciers that plants are found almost up to the edge of the ice and sometimes on it. See 

 Muhlenbergia 7: 103, III, 121. 1912. 



