a multitude of others scattered over the New England States. If 

 we hold to the glacial relict theory to explain the Arctic affinity 

 of the sphagnum bog flora, we are frequently confronted with 

 this condition : that ponds presumably similar, i. e. glacial, and 

 synchronous in origin, in the same region and subjected to iden- 

 tical general influences, have passed through the natural meadow 

 on the one hand and the sphagnum bog on the other. It has 

 been shown above that a difference in the duration of the life 

 history may be called upon to explain this seeming contradiction. 

 We must presume, however, the initial stage in both classes of 

 ponds to have been similar if not quite identical to the condition 

 characteristic, to-day, of the shores of Sandy Stream pond. The 

 divergence was subsequent to the pioneer stage. 



A rapid development, a short life history, made possible by the 

 relatively quick distruction of a pond, favors the introduction of 

 forms, which, in the struggle for existence crowd out the glacial 

 relicts and result in a natural meadow. A slow succession, an 

 extended life history, for opposite reasons, supports the develop- 

 ment and extension of the glacial relicts and the consequential 

 formation of the sphagnum bog. 



VII. CONCLUSIONS. 



In the preceding discussion we have traced the origin and 

 genetic development of the Ktaadn flora and studied the various 

 factors operative in determining the present plant physiognomy. 

 An attempt has been made to show that the accepted principles 

 of physiographic ecology hold in general in Alpine as well as 

 in lowland regions. The discussion has necessarily been rather 

 general ; but it is hoped that it will lay the foundation for further 

 and more critical study along similar lines. While most of the 

 ideas presented are not new, some of them, perhaps, appear in a 

 new relation and others, so far as the writer is aware, have here 

 their first expression. The conclusions of the study may be 

 summarized as follows : 



1. The flora of Mt. Ktaadn is glacial in origin, adventive 

 from Arctic Eastern Europe, by way of a former land connec- 

 tion, through Iceland, Greenland, and Arctic Eastern America. 



2. The flora is determined by local climatic conditions repre- 



