Jennings : A Botanical Survey of Presque Isle. 327 



Collybia radicata, Mycena acicula, 



Boletus sp. , Scleroderma vulgare, 



Cortinarius sp. 



The reaction of the Querciis velutina formation upon its habitat 

 consists mainly in the addition of more humus to the surface layers, 

 and by means of the roots to the soil for some distance below the 

 surface. Along the lake-front there is now a recession of the shore, so 

 that the waves of the ordinary summer storms reach to the base of a 

 perpendicular cliff of sand which is continually being washed out be- 

 low and thus undermining the oak forest and causing the trees to topple 

 over into the lake. The side of the cliff shows the trees to be very 

 profusely but shallowly rooted, practically the entire root-system being 

 usually in the upper three feet of soil. The soil, however, is visibly 

 stained with humus to a depth of a foot or more below this. 



That the Quercus velutina formation is the climax-stage in the 

 Beach-Sand Plain-Heath-Forest Succession is probably not the case, 

 but it does appear that the Quercus velutina formation would persist as 

 such for a long period. Owing to the physiographic changes in the 

 northwestern shore of the peninsula, in which the land has been con- 

 tinually worn away by the lake, it appears that none of the Quercus 

 velutina formation which can be definitely said to have followed the 

 heath through the pine stage has attained any great age, it having been 

 washed away. Probably in the course of time the conditions of mois- 

 ture and available plant-food might become so changed through agen- 

 cies of disintegration and the accumulation of humus that other more 

 mesophytic trees might be able to compete successfully with the oaks, 

 or to replace them altogether. 



In various parts of the northeastern United States there are to be 

 found sandy soils resembling quite closely the soil of the Quercus 

 veluti?ia habitat at Presque Isle. At Cedar Point, Sandusky, Ohio, the 

 buildings of the Cedar Point Resort Company occupy a portion of the 

 peninsula which is almost an exact counterpart of the Quercus velutina 

 habitat at Presque Isle and the close similarity extends also to the 

 formation. In the North Haven Sand-plains, in Connecticut, the black 

 oak, although scattering, is yet the predominant tree.®" Brown desig- 

 nates the formation occurring on the comparatively arid upper slopes 

 of a sandy bluff at Ypsilanti, Michigan, as the "Black Oak Society," 



«OBriUen, VV. E. /. c, pp. 578-579. 



