﻿176 Nichols: The vegetation of Connecticut 



be shown presently, plants grow most luxuriantly in shallow w^ater; 

 they may be practically absent from the deeper areas. It follows, 

 therefore, that the accumulation of muck or peat proceeds much 

 more rapidly in shallow than in deep water — so much so, in fact, 

 that the shoreward parts of a lake may have become completely 

 filled in before any appreciable accumulation has taken place in 

 the deeper areas. The filling in of deep lakes usually proceeds 

 centripetally. This is due to the fact that the shoreward zones of 

 vegetation, in consequence of their more vigorous growth, exhibit 

 a tendency to push outward into deeper water. Where this 

 tendency is pronounced, the shoal water zones may completely 

 override the deeper water zones, at the same time causing the 

 lakeward slope of the deposit to become much steeper.* The 

 filling in of the deeper parts of a lake may also be effected to a 

 varying degree by the accumulation of loose debris from the ad- 

 joining shallow^s or by the deposition of sediment in flood time, 

 while various plankton forms may contribute in a small measure 

 to the deposit. But as a rule, the encroachment of the shoal water 

 vegetation is the most important agency in bringing about the 

 filling in of the deeper parts of deep lakes. The most extreme 

 development of this method of filling is seen in connection with 

 floating mat formation (Fig. io), the discussion of which is reserved 

 for later paragraphs. 



The Succession of Plant Societies in Lakes and Swamps 

 Succession in Lakes. — Coincident with the upbuilding of the 

 substratum through deposition of muck or peat, as outlined in the 

 preceding paragraph, transformations occur in the character of 

 the vegetation growing on the lake's bottom. For, as the depth 

 of the water diminishes, it becomes possible for plants to develop 

 which were unable to grow in the deeper water. And as these 

 shallow water plants increase in number and abundance, they 

 may crowd out and eventually replace the deeper water species. 

 Thus there may follow one another a series of plant societies,! 



* For a more detailed description o 



