92 



moraine which now forms a part of the "backbone" of Long Island, 

 reaching thence westward through Staten Island and northern 

 New Jersey. The entire state of Connecticut was buried beneath 

 an immense accumulation of ice and snow and its vegetation 

 completely annihilated. 



As shown by the terminal moraines on Long Island there were 

 at least two distinct glacial epochs in this region. It was during 

 the first of these, when practically the entire northern half of the 

 island was ice-bound, that the southernmost (Ronkokoma) 

 moraine was formed and the broad outwash-plain which today 

 obscures most of the Cretaceous substructure of the southern 

 half of the island was largely developed. At the time of maxi- 

 mum glaciation, when the building up process must have been 

 most actively progressing, it is doubtful whether vegetation 

 could have maintained any appreciable foothold on the shifting 

 surface of southern Long Island. But with the stability that 

 ensued upon the temporary withdrawal of the ice the soil doubt- 

 less became populated rapidly by plants which pressed in from 

 the unglaciated regions farther south and, although it is im- 

 possible to determine accurately just what conditions obtained 

 in the period which intervened between the temporary retreat 

 and the subsequent reencroachment of the ice sheet, it seems 

 not unlikely that the vegetation came to assume much the same 

 aspect that it exhibits today. If so, upon the readvancement 

 of the ice temperate plants were once more superseded by arctic 

 forms and it may safely be assumed that in the southern part 

 -of the island these persisted throughout the reign of cold that 

 followed. With this latter hypothesis in mind one can picture, 

 in the imagination, the floristic aspect of Long Island during 

 this last period of glaciation. The northern edge of the island 

 is buried under a vast sea of ice which stretches monotonously 

 poleward. Between the glacier's margin and the old Ronkokoma 

 moraine to the south there is scant opportunity for plant life 

 to become established on account of the instability of the rapidly 

 upbuilding outwash-plain. But south of the Ronkokoma mor- 

 aine the surface of the plain is clothed with a low, dense carpet 

 of vegetation similar to that found in the Alaskan tundra of 



