Ecology of the Cincinnati Region 
155 
Fifth stage. —Soon the valley widens out and the slopes become gen¬ 
tle. Its bed is full of broken pieces of limestone; its valley floor built up 
with rubble, into which the stream cuts during freshets. The flat lime¬ 
stone reaches, with their groups of hydrophytic plants, are gone. Scat¬ 
tered sycamores and willows mark the course of the stream. 
The valley sides are gently sloping, except near the top, where the 
limestone of the Maysville still retains much of the steepness character¬ 
istic of a younger part of the ravine. 
Sixth stage. —The stream emerges into the flood plain of the river. 
Its valley, now but a few feet deep, is cut in silt. The stream is sluggish, 
and meanders across the flood plain. It is bordered by a typical marginal 
vegetation composed of willows (Salix nigra and S. alba vitellina), syca- 
B 
Fig. 27. Profiles of streams:—A, a normal valley; B, the typical ravine of the 
region. 
more (Platanus occidentalis), silver maple (Acer saccharinum), white elm 
(Ulmus americana), and, in sunny spots, Helianthus strumosus, Ambrosia 
triiida, and Silphium perfoliatum (hg. 26 ). Nothing but the marginal 
vegetation belongs to the small stream. The rest is a part of the flood 
plain of the river. Here upon the flood plain, the vegetation of the small 
stream merges with that of the river. 
Because many of our valleys present the features above described, 
they are considered as typical of the region. The ^profile of the stream of 
this typical ravine (hg. 2 y, B) \s not the normal stream profile (hg. 2 ^, A). 
Streams commencing near the margin of the upland, and lacking the 
sluggish upland course, have profiles more nearly resembling the normal. 
