124 
Ohio Biological Survey 
Up to an elevation of five feet above the center of the depression, 
swamp trees—red maple, shell-bark hickory, sour gum (Nyssa sylvatica), 
pin oak (Qiiercus palustris), and white oak (Qiiercus alba) —are com¬ 
mon (^g. 5). 
Fig. 5. Shell-bark hickory (Carya ovata) and sour gum (Nyssa sylvatica) in zone 
around center of depression. 
Higher than this, more mesophytic trees appear, advancing into the 
depression, and finally becoming the facies of the forest. 
Along the top of the ravine slopes, drainage conditions are better 
and such trees as mulberry (Monts rubra), hackberry (Celtis occiden- 
talis), honey locust (Gleditsia triacantJios), and pignut (Carya glabra), 
are found. The close proximity of hydrophytic trees of the depression 
and xero-mesophytic trees of the ravine is one of the striking features 
of this bit of woodland, and illustrates plainly the impervious nature of 
the till. 
