April, 1908.] The Vegetation of Cedar Point. 3^7 



cussed. The final decision as to the influences determining 

 whether the one or the other phytogeographical element shall 

 predominate must be deferred until exact instrumental deter- 

 minations may have been made of the various environmental 

 factors in the different parts of the Sand Plain, but, if an opinion 

 mav be here ventured, it seems probable that the ecological con- 

 ditions are so nearly equally suitable for the two elements that 

 historical considerations become of prime importance, and that 

 a very slight fluctuation of the ensemble of ecological factors 

 from one direction to the other may be sufficient to determine 

 which vegetation shall gain the ascendency. 



The vegetation of the Bar Section, as so well described by 

 Moseley consists almost entirely of the Artemisia-Panicuni Sand 

 Plain Formation, there being on the Bay side a narrow strip of 

 more hydrophytic vegetation just at the edge of the marsh. 

 The whole bar is shifting over onto the marsh and it appears 

 likely that the conditions do not reach such a stace of stability 

 as to permit the development of a well market thicket stage. 

 Instead of an outward growth of che land form towards the Lake 

 there is here exactly the opposite taking place and the real suc- 

 cession of habitats is abnormal, being from marsh through sand 

 plain to beach. 



At the south end of the small peninsula between Biemiller's 

 Cove and the Bay there is a small area of the Artemisia-Panicniu 

 Formation, but there is no very well marked area of sand plain 

 of anv considerable size in the Dune Section, small areas being 

 scattered here and there between the dunes and blow-outs and 

 in the oak forest. Between the Dune Section and the Ridge 

 Section are limited areas of a thicket stage which may be called 

 the 



Rh^s-Prunus-Toxicodendron Thicket Formation. 



The apparent facies being: 

 Rhus aromatica, 

 Prunus virginiana, 

 Toxicodendron puhescens. 



This thicket formation is soon followed by the 



Quercus velutina-imhricaria Forest Formation, 



this having here essentially the same structure as described for 

 the Ridge Succession. The thicket formation succeeding the 

 Artemisia -Pant cum Formation on Cedar Point is not nearly so 

 prominent or vigorous a structure as is the corresponding Myrica 

 Thicket Formation of Presque Isle. 



Taking up now the succession of northern phytogeographic^ 

 affinities we have, as follows: 



