﻿Nichols: The vegetation of Connecticut 177 



each one of which, by helping to raise the bottom of the lake to a 

 higher level, prepares the way for less hydrophytic societies, but 

 at the same time, by so doing, brings about its own extermination. 

 It is a familiar fact that the plants which fringe the edges of so 

 many lakes are commonly massed in more or less definite bands 

 or zones that tend to be concentric with respect to the deeper 

 parts of the lake. The floristic composition of these zones in 

 any given lake is determined largely by the ecological requirements 

 of the various species of plants which happen to be present, in 

 relation to the depth and clearness of the water, 

 from the deeper parts of a lake toward the shore (Fig. 3) the 2 



encountered, as characterized by the dominant plants, are usually: 

 (i) the PoNDWEED (Potamogeton) Zone, (2) the Water-lily 

 {Castalia, Nymphaea) Zone, (3) the Bulrush (Scirpus)— 

 Pickerel-weed (Pontederia)— Cat-tail (Typha) Zone (or Zones), 

 (4) the Sedge {Carex, etc.) Zone. Modifications of this arrange- 

 ment are frequent, but in a general way the sequence is the same 

 throughout the northern United States. 



