﻿178 Nichols: The vegetation of Connecticut 



Reference has already been made to the succession of plant 

 societies which accompanies the building up of the lake bottom. 

 It has been found that this dynamic Vertical Succession corre- 

 sponds closely with the apparently static Horizontal Zonation 

 just outlined. Thus, in a hypothetical case, it may safely be 

 assumed that the pondweeds now growing in a given locality 

 are destined to be succeeded by water-lilies, the water- 

 lilies by pickerel- weed, and these in turn by sedges. Conversely, 

 sedges growing on a mucky shore have very likely been preceded 

 by pickerel -weed, etc. This general coordination between 

 the contemporaneous horizontal sequence of zones and the his- 

 torical or vertical order of succession has been verified repeatedly 

 by the stratification of plant remains observed in peat deposits, 

 and is of great assistance in reconstructing the past or predicting 

 the future course of events in any specific locality. 



As has been pointed out by C. A. Davis in his comprehensive 

 essays on the ecology of peat formation in Michigan,* there are 

 relatively few of the highly organized vascular plants which can 

 grow when entirely submerged in water. Thus, out of the more 

 than 1,900 seed plants known to occur in Connecticut, scarcely 

 ninety, or less than five per cent., have this ability. "Of these 

 plants which will grow in water, only a few, mainly Potamogetons or 

 pondweeds, can establish themselves at a depth greater than ten 

 feet from the surface, while the majority of submerged plants 

 grow In less than six feet of water, unless it is unusually clear. "f 

 The maximum depth at which seed plants can grow rarely exceeds 

 fifteen to eighteen feet, so that the deeper parts of many lakes, 

 owing to insufficient light, heat, and aeration, are practically 

 destitute of vegetation. The first stage In the succession of plant 

 associations which accompanies the filling in of a lake is the Pond- 

 weed Stage, characterized by the predominance of submersed 

 aquatic plants, especially of species of Potamogeton. This genus 

 is represented in Connecticut by no fewer than twenty-eight 

 species, the commonest submersed forms of which are P. Rob- 

 binsii, P. Richardsonii, P. pusillus, P. amplifolius, and P. 

 heterophyllus. The two species last named are capable of develop- 



* Geol. Surv. Michigan 1906: 97-286. 1907. 



