Jennings : A Botanical Survey of Presque Isle. 347 



The Mixed Pntnus-Smilax Dune-formation. 



Along the lake-shore near Jetty No. 3, where the shore-line is reced- 

 ing and is faced with a sea-cliff, the wind striking the perpendicular 

 face of the cliff is deflected upwards with sufficient force to carry sand 

 over the brow of the cliff. There the sand is deposited in the form 

 of a fringing ridge upon the plants constituting the lower layers of the 

 Quercus velutina forest-formation, Most of these plants quickly 

 perish under the changed conditions, but a few species survive, and 

 these, together with certain invaders from other formations, constitute 

 a secondary mixed shrub-formation which may be termed the Mixed 

 Priinus-Sinilax dune-formation. 



The structure of this formation is typically as follows : 



Fades. — 



Primus virginiaiia, Smilax herbacea. 



Principal Species. — 



V^itis vulpina, Myrica carolinensis, 



Toxicodendron piibescens. 



Secondary Species. — 



Arctostaphylos Uva- Ursi, Lonicera glaucescens, 



Solidago canadensis, Celastrus scandens, 



Riibus aliegheniensis, Rubus occidentalis. 



The thicket produced by this formation is almost impassable, the 

 shrubs being bound together by the luxuriant growth of lianes, par- 

 ticularly the Smilax. The oaks here are gradually dying and falling, 

 mostly into the lake, but a few are blown backwards into the thicket 

 and contribute to its impenetrability. 



Locally, along the bay-side of the peninsula, are to be seen a i^w 

 small fringing dune-formations of this character ; as about three-fourths 

 of a mile east of Big Bend, at Crystal Point, and near the U. S. L. H. 

 Boat House. 



Between the Chimney ponds and the Head there has been within 

 comparatively recent years considerable washing away and reconstruc- 

 tion of the peninsula and the larger part of this area is now a sand- 

 plain in various phases of the Panicum-Artetnisia formation. During 

 the various changes in the shore-line many Populus ridges have likely 

 been formed, or at least begun, and subsequently wholly, or in part, 

 again washed away. There are cottonwoods scattered about rather 



