April, 1908.] 
The Vegetation of Cedar Point. 
3 1 9 
During certain damp periods the agaric appears quite abun¬ 
dantly and can quite appropriately be designated as a principal 
species characterizing the Psilocyhe ammophila Society and deter¬ 
mining a summer aspect of the formation. The secondary species 
as may be noticed, are all inyaders from the drift beach in front 
or from the habitat behind the fringing-dune. The secondary 
species are neyer very abundant in the dune. 
The successor to the fringing-dune is somewhat indefinite. 
The Ammophila apparently dies out as soon as depriyed of freshly 
drifting sand and, in case the beach grows outwards, the grass 
dies out and the sand is blown away by the wind, or, in some cases 
other dune plants may successfully inyade the dune and hold the 
sand in place. Among these latter may be mentioned Elymus 
and Andropogon and, to some extent, Arctostaphylos. 
The Elymus Dune Formation. 
Facies: Flymus canadensis, 
Elymus striatus. 
Secondary Species: 
Euphorbia polygonijolia, Artemisia caudata , 
Andropogon scoparius, Panicum virgatum, 
Tilia americana, Arctostaphylos uva-ursi. 
This formation is quite well represented along the Lake 
shore to the south of the bathing pavilion of the pleasure resort 
and it there apparently occupies an old Ammophila fringing- 
dune which has been left somewhat inland by the outward growth 
of the land form at this place, so that the Ammophila has been 
deprived of freshly drifting beach sand and has died out. 
The stage succeeding the Elymus Dune Formation is here a 
mixed formation in which Tilia americana 19 and Juniperus 
virginiana are prominent, this formation eventually giving way 
to the Quercus velutina-imbricaria Forest Formation. 
The Andropogon Dune Formation. 
Facies: Andropogon scoparius, 
{Andropogon furcatus also to a limited extent.) 
Secondary Species: The secondary species are here about 
the same as those in the Elymus Dune Formation and it is 
not improbable that these two so-called formations may repre¬ 
sent simply consocies of one and the same formation. Andro¬ 
pogon scoparius, as is also the case with Panicum virgatum, 
often forms about the separate clumps little dunes sometimes 
reaching a height of a couple of feet, but these miniature dunes 
disappear with the death of the grass and do not pass by succes¬ 
sion into other vegetational structures. 
19. Cowles, H. C. 1. c. Bot. Gaz. 27 : 361—367. The Tilia dunes 
are along parts of the Lake Michigan dune district an important feature. 
