Ecology of the Cincinnati Region 
121 
tant factor, as the vegetation must be able to withstand prolonged periods 
of complete submergence. 
The four topographic forms previously mentioned present different 
conditions of soil and ground-water. Each possesses its own general 
vegetational types, dependent for their existence upon the cumulative 
effects of past and present conditions; but constantly changing in accord 
with the constructional and destructional processes tending toward the 
ultimate mesophytic base level. 
My thanks are due to Prof. H. M. Benedict of the University of 
Cincinnati and to Prof. Henry C. Cowles of the University of Chicago 
for their suggestions during the course of my work. 
To Prof. N. M. Eenneman, I am under obligations for the use of the 
surficial geology maps of the Cincinnati, Hamilton, and Mason quad¬ 
rangles. 
^ 11. UPLAND SERIES. 
The upland is the oldest habitat presented, as well as temporarily the 
most stable. On many parts, no indications of erosive work are seen. 
Wherever undissected, the till plains and loess-covered areas are still 
essentially as they were at the close of the glacial epoch. Since that time, 
a forest cover has appeared—by what steps it is now impossible to say. 
Conditions somewhat similar have been noted by Cowles (1901) in the 
Chicago region. 
A. EOREST ASSOCIATIONS 
1. Depressions 
The till plains are not everywhere even, but sometimes have shallow 
depressions upon them a few feet in depth, and a hundred or several 
hundred feet in diameter. Depressions in the Illinoian drift sheet are 
almost imperceptible, and would be passed by unnoticed, were it not for 
the character of their vegetation. In central and northern Ohio, and 
elsewhere, in regions having a distinctly glacial topography, depressions 
of a more pronounced character and containing a very decided swamp 
or bog vegetation, are not uncommon. These have been described or 
mentioned by a number of authors,—those in Ohio by Bonser (1903), 
Dachnowski (1910, 1912, 1912a), Detmers (1912), and Schaffner, Jen¬ 
nings, and Tyler (1904) ; at Woods Hole by Shaw (1902) ; and in north¬ 
ern Michigan by Whitford (1901). 
One of the most pronounced of the depressions in the Illinoian till 
plain of this region, and one which may be considered as typical, is located 
