320 



The Ohio Naturalist. 



[Vol. VIII, No. 6, 



The successor to the Andropogon Dune Formation mav be 

 one of several different structures. In the formation are often 

 to be found invaders, of the following species: Prunus virginiana, 

 Juniperus virginiana, Parthenocissus quinquejolia, Arctostaphylos 

 uva-ttrsi, Ptelea trifoliata, Toxicodendron pubescens, Tecoma 

 radicans, so that the succeeding stage may be expected to be 

 either a heath or a thicket. The larger part of the vegetation in 

 the middle of the Dune Section corresponds closely to the vege- 

 tation of Cowles' "Dune Complex" of the Lake Michigan dune 



Fig. S. a miniature dune formed about a clump of Panicum virgatnin, 

 in a large blowout to the north of the Lake Laboratory. 



region, and the instability of the sand is here stich that a genetic 

 series of the formations is a very difficult problem. However, it 

 appears to the writer that the following formation would nor- 

 mally succeed the grass dune formations in the vicinity of the 

 Lake Laboratory: 



The Prunus-Rhus Dune-Thicket Formation. 



Facies: Prunus virginiana, 

 Rhus aromatica, 

 Ptelea trifoliata. 



Principal Species: Tecoma radicans. 



