﻿Nichols: The vegetation of Connecticut 175 



below the general level of the water table at all seasons, as they 

 usually do, the surface of the ground is kept constantly wet by 

 springs and seepage water, but the surplus is continually being 

 carried away by the small streams which drain these areas. A 

 cross section of one of these glacial-drainage-valley swamps is 

 shown by Fig. 2, C. (4) Periodic Swamps. — These bear much 

 the same relationship to permanent swamps that intermittent 

 ponds bear to permanent ponds. In other words, in an area 

 where the relations between topography and ground water level 

 are such as to preclude pond formation at any season of the year, 

 but where the ground is saturated with water at certain seasons and 

 dry at others, a periodic swamp may be said to exist. Swamps 

 of this sort are common on every hand — in low grounds, in shallow 

 depressions of any description (as in Fig. 2, D), and on side hills. 

 Between the four types of lake, pond, and swamp above de- 

 scribed, all intergradations exist, so that it is not always easy to 

 assign a given lowland area to a definite category. But while this 

 classification is necessarily elastic, and while improvements can 

 doubtless be suggested, the scheme here proposed, it is believed 

 by the writer, will prove serviceable in the study of the vegetation 

 of lowlands, not only in Connecticut but elsewhere as well. 



The Role of Vegetation in the Conversion of Lakes into 

 Swamps 

 The important r61e commonly played by plants in the conver- 

 sion of lakes into swamps has long been recognized, and the manner 

 in which this transformation is brought about may appropriately 

 be outlined at this point. When the plants in a lake die, their 

 remains sink to the bottom where, because of insufificient oxidation, 

 the vegetable debris is only partially decomposed. In this way 

 there collects on the floor of the lake a layer of vegetable muck, 

 or peat; and through the continued addition of fresh layers the 

 deposit is gradually thickened and built upward. This con- 

 structive process may go on until ultimately the surface of the 

 deposit reaches the level of the water, when the lake gives way to a 

 swamp (see Fig. 3). But the rate at which the substratum is 

 built up and the length of time which elapses before it reaches the 

 water level varies greatly in different parts of a lake. As will 



