﻿182 Nichols: The vegetation of Connecticut 



phyllous pondweeds, grow in company with the water-lilies. The 

 duckweeds {Spirodela and Lemna) and other free-floating forms 

 also commonly occur here, but these, as might be expected, are 

 not definitely restricted to any particular association. 



With the continued shoaling of the water it becomes possible 

 for plants to develop which root at the bottom and are partly sub- 

 merged but whose foliage is raised above the surface of the water. 

 As these increase in number, and as more and more light is inter- 

 cepted by their aerial photosynthetic organs, species with floating 

 leaves become scarcer and may be completely crowded out. This 

 stage, because of the widespread prominence of the lake bulrush 

 {Scirpus validtis), the pickerel-weed (Pontederia cordata), and the 

 cat- tail (Typha latifolia), may be referred to in a general way as the 

 Bulrush — Pickerel-weed — Cat-tail Stage. But quite as often 

 as not only one or at the most two of the character species will be 

 conspicuous in a given lake or pond. Furthermore, where more 

 than one is present, there is a marked tendency for one or another 

 form to dominate locally. It would frequently seem as though the 

 one first to arrive on the scene gained control. For these and other 

 reasons it is convenient to divide this stage into the Bulrush, the 

 Pickerel- WEED, and the Cat- tail Substages. Roughly speak- 

 ing, these three substages may be regarded as parallels. Thus in 

 a given pond the pickerel-weed may fill the place occupied by the 

 bulrush in another. Yet these substages cannot be regarded as 

 absolute ecological equivalents. This is evidenced by the fre- 

 quently observed zonal arrangement of the species concerned where 

 two or three are present in the same pond. The cat-tail grows best 

 in water only a few inches deep ; the pickerel-weed thrives in water 

 from six inches to nearly two feet deep; while the bulrush, although 

 it develops best in shallow water, can grow in water more than five 

 feet deep. Of the three species, the pickerel-weed (Fig. 7) is the 

 most widely distributed and from an ecological standpoint the most 

 important in Connecticut lakes and ponds. Scarcely a pond is 

 encountered from which this plant is absent, and more often than 

 not it forms a conspicuous fringe in the shoal water along the shore. 

 The bulrush is abundant in many lakes, as at Twin Lakes, Salis- 

 bury (Fig. 6), but quite as often as not it is absent or else too poorly 

 developed to be of any ecological significance. The cat-tails are 



