146 
Ohio Biological Survey 
graphy, that they are deserving of separate treatment. The ravine, as 
here described, includes blufifs and flood plains of small size only. 
A. RAVINES 
The smaller streams of the region cut through a number of different 
materials, which to some extent, modify the character of the valley, and 
with it, the plant successions. Usually, these are met with, in definite parts 
of the course. A typical valley (Hg. 2 j) with its attendant plant associa¬ 
tions is here traced. 
Fig. 19. Patches of Acorus calamus, and scattered willow trees (Salix nigra) 
mark the source of a stream on the cleared uplands. 
1. The TYPICAL RAVINE 
The ravine begins almost imperceptibly in the beech woods of the 
upland. Its head is broad and rounded, serving to collect the surface 
waters from different directions. Upon a cleared upland, a stream often 
commences in an Acorns Calamus swamp, around which are a few wil¬ 
lows (Salix nigra). Such a stream source is shown in fig. zp. 
