348 Proceedings Portland Society Natural History 



12). The shrubby undergrowth in these latter woods is ex- 

 ceedingly dense and coarse, consisting of great mats of Ju- 

 niperus communis var. depressa, Myrica asplenifolia, Gay- 

 lussacia baccata, Vaccinia m pennsylvanicum and V. cana- 

 dense and clumps of Alnus crispa var. mollis. Corema may 

 persist for a while but soon dies out as the amount of shade 

 increases. Characteristic herbaceous species of these xero- 

 phytic pine forests include: 



Polytrichum commune Fragaria virginiana 



Pteridium aquilinum Aralia nudicaulis 



Oryzopsis asperifolia Gaulthcria procumbent 



Danthonia compressa Campanula rotundifolia 



Carex debilis var. Rudgei Solidago bicolor 



The pitch pine forest is the only one of these three types 

 which seems to have reached a state of equilibrium. It is 

 one of the most distinct and sharply delimited association- 

 types in the region and definitely constitutes a physiograph- 

 ic climax. In the other cases the xerophytic pine forest, as 

 indicated by the presence of spruce, probably represents a 

 pioneer stage and is destined to be replaced by the spruce- 

 fir forest. 



c. Association-types of uncompacted rocks 



The succession of vegetation on the uncompacted rocks of 

 the region — the glacial drift and marine clays — has pro- 

 ceeded much more rapidly than on the rock outcrops and 

 has reached the final stages in nearly every instance. Con- 

 sequently evidences of the initial stages are not at hand, 

 but in all probability the succession was not unlike that al- 

 ready described. In the case of the marine clays, which oc- 

 cupy the lowlands near the coast the spruce-fir forest rep- 

 resents a physiograjmic climax ; while on the deeper glacial 

 soils succession continues beyond the coniferous forest 

 stage. 



