Hill: Penobscot Vegetation 427 



Dryopteris Thelypteris Rosa virginiana 



F est uca rubra Spiraea latifolia 



Carex seoparia Lathy rus palustris var. pilosus 



Iris versicolor Heraeleum lanatum 



Myrica Gale Vaccinia m macrocarpon 



In one locality, the so-called "Cranberry Marsh", lo- 

 cated at North Point on Swans Island there is an interest- 

 ing transition between a salt marsh and ordinary uplands. 

 This area is situated behind a barrier-beach and its vegeta- 

 tion occurs in several well-marked zones. Directly adjacent 

 to the beach is a small pond filled with Ruppia, Potamoge- 

 ton and various green algae. Adjoining this is an exten- 

 sive, extremely muddy and slimy portion of the marsh with 

 an almost solid carpet of Suaeda maritima and occasional 

 clumps of Plantago decipiens and Triglochin maritima. 

 Directly bordering on this zone is an extensive thicket of 

 Myrica Gale which in turn is followed by a boggy meadow 

 consisting of various Carices with Eriophorum virginicum, 

 Rynchospora alba, Vaccinium macrocarpon and such 

 shrubs as Spiraea latifolia, Myrica carolinensis. Ilex vcrti- 

 cillata, Rosa virginiana and Alnus crispa var. mollis. Trees 

 are also present, chiefly larches and red maples and numer- 

 ous specimens of Picea rubra have invaded the area from 

 the adjacent upland. These have increased noticeably dur- 

 ing the last twelve years and are reproducing readily. The 

 whole area apparently represents a former barrier-beach 

 pond which has been gradually filled in by vegetation. This 

 process has been facilitated by the fact that there is no 

 seepage through the beach, the surface of the marsh, being 

 well above the mean high tide level. Only at the edge of the 

 beach where it is exposed to spray do salt marsh conditions 

 exist. Vegetation has advanced up to the point where sa- 

 linity is too great and one stage has succeeded another on 

 this area until now it is dominated by shrubs. These have 

 been able to invade the ground ordinarily covered by the salt 

 marsh grasses and are kept out of the remainder of the 



