198 
Ohio Biological Survey 
2. Meadow associations ; clearings. 
In its natural condition, almost the whole of the large flood plain was 
forested. Now most of it is cleared and cultivated, and only a few nat¬ 
ural woodlands and uncultivated clearings remain. 
The pond-swamp associations are usually followed by forest asso¬ 
ciations. In places, however, an herbaceous association composed of 
sedges, grasses, and field plants (Helianthus strumosus, Vernonia fascicu- 
lata. Ambrosia trifida, and Solidago canadensis) follows the amphibious 
herbs. This condition is only temporary, and if undisturbed, trees begin 
to appear in the meadow—willows, poplar, honey locust, and elm. 
Clearings on the flood plain, which are uncultivated for a number 
of years, are usually occupied by a rank growth of tall weeds, only a few 
of which are in any way characteristic of flood plains. Most abundant 
among these, is the giant ragweed (Ambrosia trifida) which, though com¬ 
mon in moist soil in clearings everywhere in the region, reaches its highest 
development in these situations. Where this is not abundant, the vege¬ 
tation is sometimes quite varied, consisting of such plants as Helianthus 
strumosus, Silphium perfoliatuni, Echinochloa Crusgalli, Lycopus ameri- 
caniis, Sicyos angulatus, Lippia lanceolata. Polygonum pennsylvani- 
cum, etc. 
In some places the fields are grassy instead of being filled with tall 
weeds. The aspect of these clearings changes with the season, for they 
always contain a number of plants other than grasses and sedges. Miami 
mist (Phacelia Purshii), lamb’s lettuce (Valcrianella radiata), field sorrel 
(Rumex acetosella), cinquefoil (Potentilla monspeliensis) and mist-flower 
(Eupatorium coelestinum) are perhaps the most noticeable. 
3. Forest associations. 
The forests of the flood plain are of two types, belonging to different 
successions. One of these, the depression forest, is uncommon, occur¬ 
ring in undrained situations on the flood plain. The other, which is best 
known as the flood plain forest, is almost universal. It occupies the wet 
but well drained margins of streams, and the lower flood plains. 
Depression forest. —The depression forest of the flood plain is very 
similar to the depression forest of the upland. The trees are those most 
typical of undrained situations, namely, pin oak, swamp white oak, and 
red maple. Only three such areas are known, two on the flood plain of 
the Ohio, and one in Mill creek bottoms. They lie on broad plains, and 
as on the uplands, the depressions are so slight, that they are not easily 
