Hill: Penobscot Vegetation 313 



individual associations will be considered specifically and in 

 their successional relations. 



In an area occupied by a climatic formation, since the cli- 

 mate is essentially uniform, the nature of the vegetation is 

 controlled by the character of the physiography. Every- 

 where in such a region there is a tendency for the vegetation 

 to progress toward a uniform climax which represents a 

 permanent condition. 



Where the physiographic factors are favorable a perma- 

 nent climax can develop which represents the most advanced 

 type of vegetation that is capable of development on ordi- 

 nary uplands in the particular region. This is the regional 

 or climatic climax and associations of this kind, because 

 they resemble one another ecologically even though they may 

 differ slightly floristically, may be referred to a climatic 



CLIMAX ASSOCIATION-TYPE. 



Frequently, however, unfavorable physiographic factors 

 may have such a pronounced effect locally that the climatic 

 climax is unable to develop and a permanent climax is 

 reached lower down in the successional series. Associations 

 of this type represent physiographic climaces and they may 

 be referred to a physiographic climax association-type. 



II. PHYTOGEOGRAPHICAL RELATIONS OF THE 

 PENOBSCOT BAY REGION 



The Penobscot Bay region, which is merely a geograph- 

 ical unit, naturally is not distinct climatically, but rather 

 represents a small portion of a larger climatic unit area. 

 It should correspond, therefore in its climax vegetation to 

 the climatic formation as a whole. Just which of the sev- 

 eral formations of eastern North America the area under 

 discussion is a part of, however, is not easily determined, 

 owing to the peculiar characteristics of the general region 

 of which New England and Penobscot Bay are a part. More- 

 over the nature and limits of these formations are still open 

 to conjecture, as is evidenced by the varying treatment ac- 



