The vegetation of Connecticut 
V. Plant societies along rivers and streams* 
GEORGE E, NIcHOLS 
(WITH ELEVEN TEXT FIGURES) 
In the present series of papers on the vegetation of Con- 
necticut, the principle of succession has been adopted as the most 
satisfactory basis for classifying plant associations. This scheme 
of classification, it may here again be remarked, treats vegetation 
both from a genetic and a dynamic standpoint. It recognizes the 
fact that plant societies, or associations, as they exist today, are 
the product not alone of contemporaneous conditions, but of past 
conditions as well. It also emphasizes the fact that the plant 
associations of today are not necessarily permanent, but are liable 
to change through the influence of various factors. 
In the third and fourth papers of the series,t attention was 
directed to the plant associations of uplands and of lowlands. 
There the changes in vegetation, and therefore the succession of 
plant associations, are influenced primarily by plant and animal 
agencies—in other words, by biotic factors. There remain to be 
considered, then, successions which are associated not only with 
biotic factors but with topographic factors as well. Succession of 
this sort has been termed ToroGraPHIc SuccEssION. Topo- 
graphic succession is seen principally along rivers and streams 
and along the coast. The present paper deals with plant soci- 
eties along rivers and streams. Some of these societies might 
almost equally well have been treated along with the societies of 
uplands and of lowlands; yet, on the whole, so marked may be the 
impress of a stream on the vegetation at its margin, and so closely 
linked may be the development of the one with that of the other 
that the two cannot well be treated separately. 
* Contribution from the Osborn Botanical Laboratory. 
t Torreya 14: 167-194. 1914; Bull. Torrey Club 42: 169-217. I915- 
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