Hill: Penobscot Vegetation 343 



Hylocomium proliferum Hypnum Schreberi 



Hylocomium splendens Stereodon cupressiformis 



Rhytidiadelphus triquetrus Ptilium crista-castrensis 



Dicranum scoparium Bazzania trilobata 



Ptilidium ciliare Scapania nemorosa 



Characteristic herbaceous species are 



Dryopteris Linnaeana Pyrola secunda 



Dryopteris spinulosa vars. Moneses uniflora 



Lycopodium lucidulum Monotropa uniflora 



Maianthemum canadense Chiogenes hispidula 



Clintonia borealis Trientalis borealis 



Coptis trifolia Linnaea borealis var. 

 Ribes prostratum americana 



Oxalis americana Solid ago macrophyllus 



Aralia nudicaulis Aster acuminatus 

 Cornus canadensis 



Where this coniferous forest occurs in rocky localities, as 

 in the outer portions of the Penobscot Bay region, it seems 

 to have reached a state of equilibrium with its environment 

 and to be perpetuating itself. The new growth consists of 

 the same species as the old forest and no further succession- 

 al stages are in evidence. However we must consider it as 

 constituting merely a physiographic climax, rather than as 

 a distinct climax, as some authorities do, since in more fa- 

 vorable localities in the same region, such as the deeper soil 

 of the glacial drift, there is a further transition to the re- 

 gional deciduous climax. As reasons why the regional cli- 

 max fails to develop on these rocky areas there may be given 

 the following: 



(1) Shallowness of the soil. While favorable for the 

 superficial root systems of the spruce and fir, the thin layer 

 of duff, which rarely exceeds a foot in depth cannot support 

 such deeper rooted forms as the beech or sugar maple. The 

 duff also dries out quickly and so lacks the necessary mois- 

 ture for such a tree as the hemlock. 



