THE ECOLOGICAL RELATIONS OF THE VEGETATION 
ON THE SAND DUNES OF LAKE MICHIGAN. 
HENRY CHANDLER COWLES, 
[Continued from p. 117.| 
3. The upper beach. 
In the strictest sense the upper beach is not a portion of the 
beach at all, since it is beyond the reach of the waves; it might 
pethaps be called a fossil beach, but the fact that it is contin- 
tous with the beach proper seems to exclude that term, as does 
the recency of its fossilization. The expression fossil beach will be 
reserved for a formation of greater geological age and separated 
from the present beach by other topographic forms. Where 
ea are superposed upon the beach, the upper limits of this 
third beach zone are quite vague, though the theoretical line of 
demarcation is where the sand is first accumulated by the wind. 
Where clay bluffs are present at the water’s edge, the beach is 
a ‘arrow and the upper limit fairly well defined, though at 
mes obscured by alluvial fans. Occasionally the upper beach 
ay ese very close to the water’s edge; this is the case 
ae ~ lower and middle beaches are very narrow because of 
mee Sometimes the lower or middle beach zone is 
approach ya tiny cliff; in such a case the upper beach may 
beach, as to the edge of this cliff. The limits of ane upper 
1 aap other beach zones, are constantly shifting. The 
winter st MS @re Carried lakeward or landward by the waves of 
More arene but on the whole the lower limits are pushed out 
lower eg lakeward, keeping pace with the advance of the 
Upper limits, } The shifting of the wind causes variations in = 
formed iow ut on the whole the dunes likewise are common y 
The three 5 more lakeward, as will be shown further on. 
imegularity tins es, then, shift from year to year with apparent 
1899] Out there appears to be as a resultant a general pro- 
167 
