132 
Ohio Biological Survey 
Where white oak becomes the dominant tree, the ground is usually 
less swampy, though still very wet; the herbaceous vegetation is more 
abundant, but made up largely of the same species as are found in the 
other parts of the forest. Kentucky blue grass (Poa pratensis) often 
forms a close sod in the more open parts, and other grasses, Poa sylvestris, 
Cinna anindinacea, and Agrostis perennans, are not infrequent. 
Fig. 12. Opening in a hydrophytic forest. 
White oak. —The general occurrence of white oak (Qucrcus alba), 
which is so well known everywhere as a xerophyte or xero-mesophyte, 
in the hydrophytic forests of the uplands, is of special interest. Mixed 
with pin oak, sweet gum, and red maple, and surrounded by hydrophytic 
herbs and mosses, its hydrophytic propensities can not be doubted 
(hg. ig). Neither does it seem to mark any decided advance in the 
hydrarch succession in which it is here found. Where mixed with pin 
oak, it is subjected to the same conditions as the latter — an undrained 
clay soil where water may stand in puddles for several months. Where 
white oak becomes the dominant tree, the ground is not so wet, and water 
