18 INTRODUCTION 



their present extra-pine-barren distribution, of having spread 

 from the pine-barrens since the last release of the Beacon Hill 

 formation may be mentioned Lycopodium carolinianum, Panicum 

 oligosanthes, Amphicarpon Amphicarpon, Panicum ensifolium, 

 Eriocaitlon decangular e, J uncus caesariensis, Xerophyllum asphode- 

 loides, and Agalinis Holmiana. 



30. At the advance of the ice there must have been a great 

 invasion of this region by northern species, many of which are 

 still to be found within our area. Just what the character of these 

 plants was it is impossible to say with any degree of definiteness, 

 although specimens of Canadian inter-glacial fossils indicate many 

 genera, perhaps even species that exist in the north today. In the 

 absence of any definite information, as to what this pre-glacial 

 flora consisted of, it seems best to append a list of plants that while 

 not certainly referable to pre-glacial conditions, are now known 

 only from the north, reaching their southerly distribution point, 

 at the present time, within the area covered by this work. 



Northern Species Whose Southerly Distribution Outposts, in the 

 East, Are Within Our Area 



Botrychium lanceolatiim, Potamogeton nutans, 



Botrychium silaifolium, Potamogeton Oakesianus , 



Polystichum Braunii, Potamogeton lateralis, 



Eqnisetum pratense, Potamogeton compressus, 



Equisetum littorale, Trighlochin maritima, 



Equisetum variegatum, Scheuchzeria palustris, 



Lycopodium inundatum, Sagittaria Engelmaniana, 



Lycopodium alopecuroides, Poa debilis, 



Lycopodium adpressum, Panicularia laxa, 



Lycopodium annotinum, Panicularia canadensis, 



Isoetes macrospora, Panicularia grandis, 



Isoetes ambigua, Panicularia borealis, 



Isoetes Eatoni, Bromus Kalmii, 



Isoetes canadensis, Agropyron biflorum, 



Isoetes Tuckermani, Panicum spretum, 



Pinus resinosa, Panicum boreale, 



Sparganium angustifolium, Panicum languidum, 



Sparganium fluctuans, Panicum xanthophysum, 



