177 



this wide range because of any perfection of seed dissemination, nor 

 because of occasional means of transportation. It has more probably been 

 brought about by a former connection of these separate regions, making 

 them practically continuous. Such practical continuity may have been 

 secured by means of the flooded rivers and swollen lakes of tbe Champlain 

 period. This is not offered as a solution of all of the problems of plant 

 distribution, but in tbe firm belief that in many of these problems the 

 solution is to be sought in former physical conditions. 



It was the original intention that the present paper should also include 

 a discussion of the species restricted to the soutbern tiers of counties, bul 

 tbe time required to work our former shore lines and water-levels for flint 

 region was too great. The preliminary work, however, seemed to indicate 

 confirmation of the conclusions indicated in this paper. 



12 — 496« 



