188 
Ohio Biological Survey 
absent, the upper shore association approaching close to the water’s edge. 
Vegetation is more abundant and more luxuriant than on the upper 
shore elsewhere, and some hydrophytes are included among the annuals. 
1. Gently sloping beach-like shores 
In many places the river shore is broad and rises gently from the 
water’s edge. Along the Ohio, such shores are of sand or silt. On the 
two Miamis, they are usually of gravel or cobblestones with more or less 
mud. There is not a great deal of difference in the vegetation of these 
two kinds of shores. 
Sandy shores. —On sandy shores, the density of the vegetation in¬ 
creases up-shore. The demarkation between lower and upper shore is 
indistinct, so that there sometimes appear to be no definite zones below 
the first tree zone. The wettest places are occupied by Eleocharis oliva- 
cea. On other parts of the shore, chiefly the second zone, may be found 
a variety of plants, among which are a number of grasses fEchinochloa 
Crusgalli, Panicunt dichotomiflonim, Cenchrus tribuloides, and Eragrostis 
hypnoides), knotweeds, (Polygonum pennsylvanicum and P. lapathifo- 
lium), Amaranthus hyhridus, Strophostyles helvola, Ambrosia trihda, and 
Bidens laevis. Here and there are seen a few small willows (Salix nigra 
and S. longifolia), and cotton-wood (Populus deltoides) advancing into 
the zone of annuals. These presage the advance of the marginal tree zone. 
The width of the zone of annuals is determined by the slope of the shore 
and the average summer fluctuation of the river. The plants of the 
shore are mainly transients. They are plants which come late, after the 
rivers have gone down to low summer heights. 
Cobblestone shores. —The shores of gravel or cobblestones are occu¬ 
pied by an association of herbaceous plants very similar to that found on 
sandy shores. The principal differences are that there is no definite 
advance of woody plants from a distinct tree zone, and that the upper 
shore association is more xerophytic. The willows are few and scattered. 
Along very flat bowlder shores, there is sometimes a marginal zone 
composed of Dianthera americana, advancing out into the river (hg. 44 ). 
This is usually found where the shore is narrow, and bordered by bluff¬ 
like banks of the flood plain. In such places the shore is shaded by the 
tall trees along the banks, and much of the vegetation characteristic of 
sunny shores is absent. 
The second zone of cobble shores is occupied by an open association, 
in which herbaceous plants have a prominent place. In contrast to the 
