NICHOLS: THE VEGETATION OF CONNECTICUT 263 
Fraxinus americana Fraxinus pennsylvanica 
Fraxinus nigra 
The Temporary Nature of Flood Plain Forests——It has been 
shown in the preceding pages that during the development of a 
flood plain the vegetation becomes less hydrophytic and more 
mesophytic, culminating in the formation of a mesophytic forest. 
Such a forest is to be regarded as the climax association of flood 
plains. But it can easily be seen that, owing to the activity of 
the river, this forest may be relatively short lived; in other words, 
it may represent only a temporary climax. For as the river 
meanders about on its flood plain in serpentine curves, it is con- 
stantly wearing away its banks on the outer, concave side of each 
bend, while at the same time deposition is meee, taking place 
on the opposite, convex shores. In this way ‘‘a river may swing 
quite across its flood plain, destroying all that it has built, including 
the mesophytic forest.’’* Changes of this sort take place with 
appreciable speed and may be observed along almost any 
depositing stream. . 
Ox-bow Ponds.—In this connection should also be mentioned 
the crescent-shaped curves, or ox-bows, which are a characteristic 
feature of old-age streams. Frequently the meandering river 
shifts its course, abandoning a loop-like channel for a more direct 
route. The loop then becomes an ox-bow pond (Fic. 1, D), and 
as such its vegetation can best be treated with that of ponds and 
swamps.} 
The Subsequent History of Flood Plains—One other phase of 
river activity may be briefly sketched. It has already been shown 
that while deposition is the main feature of old-age streams, 
erosion is not wholly absent. In the course of time, for various 
causes, downward cutting may be renewed, the flood plains become 
terraces, and new flood plains may ultimately be formed at lower 
levels. The resultant topography is well illustrated along the 
Connecticut and others of the larger streams. The low flood 
Plains of today are comparatively recent in origin. 
ancient flood plains are represented by sandy terraces, of which 
The more 
* * Cowles, H. C., 1901, op. cit., p. 107. | ; F 
7 See Bull. Torrey Club 42: 171. 1015. Fig. © of this paper pictures a 
typical ox-bow pond 
