﻿Nichols: The vegetation of Connecticut 213 



ception: "Where the habitat dates back to Pleistocene times and 

 has remained undisturbed, we find today the bog flora. Where 

 the habitat is of recent origin or has been recently disturbed, we 

 find the swamp flora, or mixtures of swamp and bog species." 

 The plausibility of some such explanation for the presence of 

 northern plants in bogs was re-impressed on the writer during the 

 past summer in the course of ecological investigations conducted 

 on Cape Breton Island. There the bog is the common swamp type, 

 and its vegetation seems wholly in harmony with the forests of 

 fir and spruce that clothe the surrounding uplands; the transition 

 from one to the other is gradual ; bog vegetation there is much less 

 restricted than here, as is evidenced by the fact that species which 

 in Connecticut are confined to bogs commonly occur there in 

 shallow depressions along streams, while a much larger proportion 

 of bog species grow on the uplands. Yet notwithstanding the 

 marked contrast in the upland vegetation there and here, the 

 resemblance of bog vegetation in the two regions, not only in 

 general aspect but in specific composition, particularly with ref- 

 erence to sedges, ericaceous shrubs, and trees, is remarkable. 

 Here in Connecticut, however, in contrast to the conditions farther 

 north, the bog is a comparatively rare swamp type, and its vege- 

 tation seems utterly out of harmony with the deciduous forests of 

 the surrounding uplands; the transition from one to the other is 

 abrupt, while the characteristic northern bog plants for the most 

 part are restricted to bogs. 



In the first paper of the present series* the writer suggested 

 the probability that subsequent upon the final retreat of the con- 

 tinental ice sheet, this region for a long time was populated by 

 northern types of vegetation which, having originally been forced 

 southward by the advance of the glaciers, once more migrated 

 northward in the wake of the retreating ice-front. During the 

 time that has elapsed since the recession of the ice, variously 

 estimated at from 20,000 to more than 50,000 years, there un- 

 doubtedly has been a gradual readjustment of the climate, and as 

 a result of this, coupled with the invasion of plants from the south 

 and west, our present vegetation has been evolved. In the his- 

 torical sequence of vegetative formations which have occup ied 



*Torreya 13; 93. 1913- 



