Hill: Penobscot Vegetation 323 



ern limit of the sugar maple (Figure 2). This region oc- 

 cupies the great Laurentian tableland of eastern Canada, a 

 country of sterile acid granites with poor drainage. The 

 climate may be judged from the rainfall evaporation ratios 

 as given by Transeau (28), the amount of rainfall being 

 equal to 150% and over of the evaporation. The climax 

 forest consists of white and black spruce, balsam fir and 

 paper birch. 



B. The Eastern Deciduous Forest Region. This area 

 centers in the Ohio basin and the southern Appalachians, 

 sending a tongue northward along the Piedmont region east 

 of the mountains. The northern limit of the area may be 

 said to coincide with the southern limit of the balsam fir. 

 The underlying rocks are for the most part Devonian and 

 Silurian in nature and yield a rich basic soil. The rainfall- 

 evaporation ratio is from 80%-110%. The climax forest of 

 the region is composed of chestnut, tulip, black walnut, 

 sycamore, beech, sugar maple, and several species of oak and 

 hickory, constituting the "southern hardwood" forest of the 

 lumbermen. 



C. The Transition Forest Region. This area lies be- 

 tween the two above regions and shows characteristics of 

 both. In extent it is situated between the northern limit of 

 the sugar maple and the southern limit of the balsam fir, an 

 area which about coincides with the distribution of one of 

 its character trees, the yellow birch. The rainfall-evapora- 

 tion ratio is from 110%-150%. The region shows a transi- 

 tion to the coniferous forest on the one hand ; and to the de- 

 ciduous forest on the other, although potentially the decid- 

 uous type must be considered as the regional climax. Two 

 subdivisions may be recognized depending on the proximity 

 of one or the other of the main forest regions 



1. THE CANADIAN-TRANSITION ZONE. this Zone OCCU- 



pies the northeastern portion of the Transition region, 

 characterized by the higher rainfall-evaporation ratios, and 

 comprises the Maritime Provinces, northern New England, 



