Hill: Penobscot Vegetation 403 



Scirpus atrocinctus Galium Claytoni 



Erioplwrum tenellum Bidens ccrnua 



Usually a fringe of shrubs or even trees borders such a 

 periodic pond, forms like Alnus ineana, Ilex verticillata, 

 Rhododendron canadense, Kahnia angustifolia and the 

 larch being common. 



c. Association-types of permanent undrained lakes, 



ponds, and lake-swamps 



Association-types of ordinary bogs 



The succession of vegetation in undrained areas differs 

 from that in well-drained ponds chiefly in the ultimate de- 

 velopment of a bog, a swampy area characterized by the 

 predominance of ericaceous shrubs and the abundance of 

 sphagnum. Bogs are fairly common on the islands and the 

 eastern side of the Bay, but they are infrequent inland and 

 along the western border. 



The early stages in the filling up of an undrained pond 

 are similar to those outlined for well-drained areas, such 

 aquatic plants as Xymphaea odorata, Nuphar variegatum, 

 Utricularia vulgaris var. americana, Utricularia intermedia 

 and the various potamogetons being common. It is in the 

 sedge stage that differences are first evident. The most 

 striking feature in the development of a bog is the forma- 

 tion of a floating mat. This results from the vigorous 

 growth of plants along the margin of the pond, which tend 

 to push out from the shore and eventually produce a raft- 

 like mass of vegetation. In some cases sedges, chiefly Ca- 

 rex filtformis and Carex rostrata, are pioneers in this mat 

 formation, growing with their rhizomes so interlaced as to 

 afford considerable strength to the mat. Shrubs, however, 

 are of far greater importance in the Penobscot Bay region 

 in building up such a floating mat. The most conspicuous 

 pioneer species is the sweet gale (Myrica Gale) while other 

 frequent forms include the cassandra (Chamacdaphnc caly- 

 culata) and Pyrus melanocarpa (Figure 36). The root- 



