Jennings : A Botanical Survey of Presque Isle. 335 



depauperate shrubs — ATyrica carolinensis, Quercus virginiana mari- 

 tima, Rhus copallina. The higher sand-hills are often occupied by 

 dense thickets oi Myrica carolinensis usually i^ to 2 meters (5 to 6 

 feet), but frequently 3 meters (9 feet) high, often unaccompanied by 

 other woody species. This plant, which is more or less at home in the 

 drier portions of the forested plain, is, however, most characteristic as 

 a dune-plant and is noteworthy as the shrub which usually occurs 

 nearest the beach." 



At Presque Isle Myrica never assumes the role of a dune-plant. 

 It rarely seems able to extend itself, even by vegetative dissemination, 

 up to the tops of the ridges and neither do the drupes seem to be 

 capable of successful growth in the drier portions of the sand-plain. 

 Although structurally a xerophyte,®' and usually occupying quite 

 xerophytic habitats along the Atlantic sea-board, it must be regarded 

 at Presque Isle as being much less xerophytic in habit. 



In the advanced stages of the Myrica thicket-formation other 

 plants than Myrica become more and more prominent, until finally a 

 transitional stage is attained, representing the advanced guard of the 

 coming forest. At this stage the thicket consists typically of the fol- 

 lowing species : 



Riibiis allegheniensis, Vitis znilpina, 



Riibus occidentalis, Celastrus scandens, 



Prunus seroiina, Fnnius pennsylvanica. 



The Prunus Forest -formation. 



A forest-formation soon displaces the transitional thicket following 

 the Myrica thicket-formation. This forest-formation is at present 

 best seen immediately to the west and south of Long Ridge, where 

 it alternates with a formation derived from the RJius-Almis thicket, 

 to be described in connection with another succession. 



Typically the structure of the Prunus forest-formation is as follows : 



Fades. — 



Prunus serotina, Prunus pemisylvanica. 



Principal Species. — 



Rubus allegheniensis, Celastrus scandens, 



Riibus occidentalis, Vitis vulpina. 



*' Kearney, T. H. " Plant-Covering of Ocracoke Island." /. c, p. 294. 



