178 
Ohio Biological Survey 
2. Clearing associations 
Most of the clearings are occupied by a dry meadow association 
different from that found in any other location. Wire grass fPoa com- 
pressa) is the most common grass, except in some of the older clearings, 
where Kentucky blue grass fPoa pratensis) almost supersedes it. Sap¬ 
lings are usually scarce, and represented only by a few red elms, locusts, 
and red cedars. It is among the herbaceous vegetation that the charac¬ 
teristic plants are found. Kuhnia eupatorioides, Verbena stricta, Arabia 
drummondi, Pentstemon hirsutus are the most characteristic. With these, 
some other widespread herbs occur. 
These cleared fields are covered with the layer of soil which has 
accumulated since the deposition of the gravels. Although xerophytic, 
they do not present the extreme condition of dryness of exposed gravels. 
Gravel pits are very artificial habitats, but possibly they present con¬ 
ditions somewhat parallel to those existing before the accumulation of 
the soil cover. The material is so coarse and loose, that almost no water 
is retained near the surface. In no place, except on under-cut gravel 
bluffs or on bare rock, are conditions of ecpial dryness found. Only the 
most extreme xerophytes can exist. Even these are not abundant. The 
association is an open one. The ordinary xerophytes of the region, which 
usually occur in dry situations are stunted. Verbena stricta, occasional 
plants of Pentstemon hirsutiis, Oenothera laciniata, Croton monanthogy- 
nus, and stunted Oenothera biennis make up the open gravel association. 
In a few places, the prickly pear cactus, Opnntia Rahnesquii, is the facies 
of the association, and Yucca iilamentosa or Andropogon virginicus, pri¬ 
mary species (hg. 40 ). 
On long-abandoned gravel pits, the association is less open, and 
comes to resemble the dry meadow association of clearings. 
The facies of sun plant formations of gravel terraces is not the same 
everywhere. In some localities, a usually common species may be absent, 
and others so restricted in range that they are not even mentioned here, 
may be dominant. Of all the herbaceous plants, Verbena stricta is by 
far the most widespread and characteristic plant of gravel terraces, dr 
other gravel deposits. It is, as far as known, restricted to such habitats. 
JArbena angnstifolia, which occurs frequently in upland meadows, never 
occurs in the fields on the terraces. The two plants are entirelv distinct 
in range, the former species (V. stricta) never occurring on uplands, 
except on the gravel roadbeds of some of the railroads. Furthermore, 
the species are sharply defined, and intermediate forms, such as are found 
