1905] BROWN—THE PLANT SOCIETIES AT YPSILANTI 267 
bluffs. As the waters had now subsided only about 50 feet, the 
base of the cemetery bluff was as yet under water; but the part 
exposed was free for the first vegetation to come in. It was not 
until the Lake Warren stage that the river, through the fall of waters 
at its mouth, cut still deeper in its channel and exposed the base of 
the cemetery bluff. The land area which was for a time submerged 
F ee) : 
IG. 2.—Carex stricta, the deepest water sedge here, appears on the advance of 
the line of sedges, and forms tufts of great compactness and strength. 
ane’ then exposed by degrees forms the large relatively level portion 
of southeast Michigan, extending for thirty miles or more west from 
ake Erie and the Detroit River, and nearly the same distance 
etal into Ohio. Westward from the basin area the surface 
gh we into countless hills, ridges, and kettle-holes, characteristic 
—.. regions. It has been known for some time that the 
that of “ oi en of the Huron-Erie basin is distinct from 
limits of . morainal Brea, with a line of tension in sight of the og 
been off € city of Ypsilanti; but an explanation of this has not yet 
offered, and does not fall within the limits of the work in hand. 
