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the usually poorly developed Artei)iisia-Paniciiin association lies a 

 more or less gravelly or pebbly area, whose vegetative appearance is 

 characterized by the stools of Andropogon scoparius. The physio- 

 graphic appearance gives every indication that the area was at one 

 time part of the beach. Later it was covered with drifting sand, and 

 it is now being gradually uncovered by the very slow movement of the 

 fringing dune towards the lake. Because of its past history it is 

 given the name, "fossil beach," in allusion to the corresponding geo- 

 logical term. The pebbles and the gravel of which its surface is com- 

 posed are all well-rounded and flattened, clearly indicating the former 

 presence of surf. The largest of these pebbles are about 15 cm. in di- 

 ameter and 2-3 cm. in thickness. Almost all of them are made up of 

 granites, quartz, and, less frecjuently, shales and sandstones. From 

 between them the wind has gradually removed the mobile sand, which 

 is taken to the lakeward side of the fringing dune. So much sand has 

 been removed that now the pebbles are very frequently perched upon 

 little hills a few millimeters in bight. Investigation has shown that 

 the sand in these little "tees," to use a golfing term, is virtually damp 

 clear to the surface. The pebble itself affords the tee protection from 

 the drying effects of the direct rays of the sun. In the protection thus 

 afforded, spiders as well as some small insects spend the hotter part 

 of the day. Rain drains very rapidly through this soil. 



Ecological Characteristics. — \\'hat has been said of the ecological 

 characteristics of the Artoiiisia-Panicum association will apply here 

 also. The habitat is dissophytic, but the above-ground part is not 

 quite so xerophytic as in the other association. Humification — rather 

 than eremacausis, which is the rule in the Artcuiisia-Panicum associa- 

 tion — is beginning to take place. Lack of sufficient food material 

 seemed to be the most potent cause for the openness of the vegeta- 

 tion. 



The Association. — The bunch-grass association is a typical prai- 

 rie one, and, of course, is better represented in areas farther west. 

 The bunch-grass association of the prairie vegetation is the pioneer 

 both of the prairie and the forest type of vegetation. It can maintain 

 itself on fossil beaches and readily invades the upper beach. Mean- 

 while it adds humus to the soil and prepares the way for successions 

 to a more advanced type of prairie or to a heath or to a forest. 

 Which succeeds, depends upon several factors, among which are 

 proximity, means of dispersal of the invaders, and the ability of the 

 invaders to effect ecesis. The association itself has for its dominant 

 species a grass which grows in tufts or bunches. According to the 

 specific identity of the bunch-grass, the association is divided into 



