Hill: Penobscot Vegetation 317 



may be in part unique, ecologically at least it is doubtful 

 whether this area should be considered as a distinct climatic 

 formation. As Nichols (23) has pointed out it should 

 rather be regarded as an extension of one or the other of 

 the great forest areas mentioned above. As will be seen 

 later, evidence from both the historical and developmental 

 view-points indicate that it is a northern extension of the 

 eastern deciduous forest. A study of the sequence of the 

 post-glacial migrations, and the noteworthy fact that 

 throughout the region the deciduous climax trees are able 

 to supercede the coniferous in all physiographically favor- 

 able situations bear out this statement. 



Combining as it does both northern and southern ele- 

 ments, the Transition Forest region presents a varied rather 

 than a uniform type of vegetation. There are in the main, 

 however, two readily recognizable subdivisions, each charac- 

 terized by the nature of the climax forest which it supports. 

 In the southern and western portions of the Transition re- 

 gion the climax forest consists primarily of sugar maple, 

 beech, yellow birch (Betula lutea), white pine (Pinus Stro- 

 bus), and hemlock (Tsuga canadensis), while in the north- 

 eastern portion, in addition to these trees, there also occur 

 balsam fir, black spruce, paper birch and red spruce (Picea 

 rubra). 



In the opinion of the writer the proper interpretation 

 of the forest areas of eastern North America necessitates 

 the recognition of these two zones in the Transition re- 

 gion, and a modification of our ideas regarding the extent 

 of the deciduous forest proper. 



While the sugar maple and beech may be prominent mem- 

 bers of the deciduous forest at the center of its best devel- 

 opment, the most striking feature of such forests is the 

 presence of trees like the chestnut, tulip, sycamore, black 

 walnut (Juglans nigra), butternut (Juglans cinerea), and 

 numerous hickories (Carya sp.) and oaks. This is the Al- 

 leghanian forest as defined by Bray (2) and it is this forest 



