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Ohio Biological Survey 
gressive, for it initiates a long and varied xerarch* succession, which 
must intervene between the early hydrophytic stages, and ultimate 
mesophytism (iig. 6). The end of this succession is much more distant 
than that of the hydrarch succession, which has already advanced so near 
to mesophytic conditions. And given time enough, this ravine is destined 
to destroy the mesophytic forest already established around the depres¬ 
sion. 
Fig. 7. An upland hydrophytic forest in spring (Terra Alta). 
Abundance of depressions .—Many other such depressions have been 
found upon the uplands near Cincinnati, some larger and some smaller, 
but all similar to the one here described. Few, however, show so com¬ 
pletely the remarkable succession above described; for they are often more 
irregular, and have no definite center around which the zones are arranged. 
The amount and character of the undergrowth in the scattered depression 
* The terms xerarch and hydrarch were first used by Cooper in 1913. The following is his 
footnote defining them: “The terms xerarch and hydrarch are here used for the first time, for 
the purpose of indicating a natural and important classification of plant successions. The 
former is applied to those successions which, having their origin in xerophytic habitats, such 
as rock shores, beaches, and cliffs, become more and more mesophytic in their successive stages; 
the latter to those which, originating in hydrophytic habitats such as lakes and ponds, also 
progress toward mesophytism.” 
