128 
Ohio Biological Survey 
common upland type. This will be described later in connection with 
the forests of imdrained flats. Often the depression, though small, is 
decided enough to produce a pond. Such ponds, however, are temporary, 
and dry up during the summer. They are bordered by sedges and but- 
tonbush (Cephalanthiis occidentalis), or overgrown by a rank growth of 
poison ivy (fig. 8). 
Depressions of all sizes occur on the till plain of the upland, from the 
small ones just described, to those so large that they are scarcely distin¬ 
guishable from the undrained flats. 
Fig. 9. Forest of pin oak, near Bethel. 
2. UXDRAINED FLATS 
Wherever the uplands are broad and undrained, a hydrophytic forest 
similar to that of depressions is found. In the immediate vicinity of 
Cincinnati, such areas rarely occur, as stream dissection has progressed 
too far. The hydrophytic forest of the undrained flat is never extensive 
here. But eastward, in Clermont and Brown counties, where the old 
peneplain is uncut for many miles, except for shallow valleys, the swamp 
