264 Nichols: The vegetation of Connecticut 



there may be one or more. These have attained their present 

 condition through the downcutting of the rivers into the deep 

 fill of glacial drift and outwash,* The effect of the changed 

 topographic relations on these former flood plains as habitats for 

 plants is readily comprehended. With the lowering of the river 

 they must gradually have become more and more xerophytic and 

 thus less and less tenable for the flood plain mesophytes. The 

 actual effect of these changes on vegetation can only be con- 

 jectured. For, just as has been pointed out in the case of rock 

 ravines, the period of time involved has been so great that oscilla- 

 tions in climate as well as changes in topography must presumably 

 be taken into account. At the present day the vegetation of river 

 and stream terraces is perhaps best treated with that of uplands, 

 since the river has long since ceased to act as a dynamic factor in 

 its development. 



Acknowledgments 



For suggestions in connection with the preparation of this 

 paper, the writer is greatly indebted to Professor Joseph Barrell, 

 of the Geological Faculty, and Professor A. W. Evans, of the 

 Botanical Faculty of Yale University, and to Mr. C. A. Weatherby, 

 of East Hartford. 



Sheffield Scientific School of Yale University 



* In this connection, see Rice, W. N., & Gregory, H. E., Manual of the Geology 

 of Connecticut. Conn. State Geol. and Nat. Hist. Surv. Bull. 6: 35, 36. 1906. 



