1899] DUNE FLORAS OF LAKE MICHIGAN 189 
to adapt itself to a mild type of dune existence. Another 
swamp plant, Cephalanthus occidentalis, occurs near the same 
beach and in asimilar way helps to build these low slow-growing 
dunes. The conversion of swamp plants to dune plants will be 
discussed more at length in another place. 
The most extensive area of dune formation on the beach 
was seen on the west shore of Beaver island. Fig. 6 shows a 
Fic. 6,— i fore 
dunes j Embryonic beach dunes at Beaver island. Primary Prunus and Salix 
In the foreground. 
Smal] : ; : 
Portion of this area. This place is of peculiar interest 
midly Be is a perfect series of gradations between the 
towing wing dunes first described and those of the slower 
there a ae Toward the beach proper (foreground, fig: 6) 
dune-builg ofS formed by Salix, Prunus, and other high-grade 
‘ts. Farther back, toward the taller and older dunes 
