﻿194 Nichols: The vegetation of Connecticut 



more humid climate, peat might develop on such sites; but in Con- 

 necticut the mineral soil is frequently covered by little more than 

 the thin mantle of living vegetation and there is little humus. 

 Humus, as is well known, possesses a very high capacity for 

 retaining water, so that a soil rich in humus dries out very slowly. 

 A soil poor in humus may be equally wet in spring, but with the 

 lowering of the water table it dries out much more quickly. Such 

 a swamp, in consequence of the better drainage and aeration of the 

 soil, must necessarily afford a habitat quite different from that in 

 a swamp underlain by a mucky soil. It seems probable, there- 

 fore, that the abundance or scarcity of humus may be an important 

 factor in restricting the distribution of the trees mentioned above 

 as characteristic of periodic swamps. 



Intermittent Ponds. — From an ecological standpoint these 

 should be classed as swamps rather than ponds, since the seasons 

 when their basins contain water coincide for the most part with 

 the period of vegetative inactivity. During the growing season, 

 except for a short time in spring and early summer, the bottom is 

 merely muddy, and very often in late summer it is quite dry. 

 With the exception of species having more or less amphibious pro- 

 clivities, like Proserpinaca palustris, Ludvigia palustris, Alisma 

 Planiago-aquatica, Sium cicutaefolium, and occasionally Nymphaea 

 advena, aquatic plants are absent. Those parts of the bottom which 

 remain longest submerged may be almost destitute of vascular 

 plants and frequently support a rich growth of algae, like Vauche- 

 ria and Botrydium, or of bryophytes, like Riccia, Fossombronia, and 

 Ephemerum, On parts of the bottom which are exposed during a 

 somewhat longer period commonly grow Eleocharis acicularis, 

 Hypericum virginicum, Lysimachia terrestris, etc. ; while very often 

 there is a rank growth of various species of Bidens and Polygonum, 

 together with other rapid-growing, fall-flowering annuals. Fringing 

 the margin of the "pond" may occur almost any of the herbs, 

 shrubs, or trees characteristic of swamps. It should be noted, per- 

 haps, that Cephalanthus is an almost omnipresent marginal shrub. 



Plants in Relation to the Formation of Marl 

 There is one other important phase of plant activity in con- 

 nection with the filling in of lakes and ponds to which no ref- 



