Hill: Penobscot Vegetation 415 



lower h< oit than those in open swamps (Figure 42). The 

 common species in these wet meadows include: 



Dryopteris Thcly pterin Carex flava 



Dryopteris noveboracense Juncus balticus var. 

 Agrostis alba littoralis 



Agrostis alba var. vulgaris Luzula campestris var. 

 Calamagrostis canadensis multi-flora 



Glyceria nervata Habenaria psycodes 



Eriophorum tenellum Liparis Loeselii 



Carex scoparia Geum rivale 



Carex echinata Hypericum virginicum 



Carex rosea Hydrocotyle americana 



Veronica scutellata 



The character and the succession of the vegetation in 

 meadows is often altered owing to the fact that they are us- 

 ually cut over for hay each year. If left to themselves 

 both the above types of swamp become colonized by shrubs. 

 These, indeed, may be present from the very first and areas 

 with a mixture of shrubs and grasses and sedges are very 

 frequent (Figure 43). The most important shrub is the 

 alder (Alnus incana), while other common species are: 



Salix discolor Rosa virginiana 



Salix humilis Ilex verticillata 



Amelanchier laevis Cornus stolonifera 



Spiraea latifolia Vaccinium corymbosum 



Eventually the swamp is invaded by trees and a swamp 

 forest results of the same character as that already describ- 

 ed as the culminating association-type in lake-swamps. 



e. Association-types of poorly drained swamps 

 The conditions thus far described for the formation of 

 the hydrarch series apply only to the clearly marked ex- 

 tremes of pond and swamp vegetation. It must not be as- 

 sumed that every locality in the lowlands can be assigned 

 to one or another of these types. Wherever there are in- 



