April, 1908.] The Vegetation of Cedar Point. 309 



In the course of time the soil may have accumulated to such an 

 extent that the shallower water may offer conditions suitable 

 for other species than those of the resident formation and, by 

 invasion and ecesis, another formation may eventually occupy 

 the habitat. In the Lily Pond the formation next outside of the 

 lilv zone is the following: 



The Decodon-Persicaria Formation. 



Facies: Decodon verticillatus , 

 Pe rsica ria la u rin a . 



Secondary Species: 



Nmmihergia thyrsiflora, Alisma plantago-aquatica, 



Solanum didcaniara, Cephalanthus occidentalis , 



Pontederia cordata, Sagittaria latifolia, 



Nymphaea advena. 



Further study of this formation might, perhaps, result in the 

 placing of Persicaria laurina as a principal species, but it probably 

 is best regarded as one of the facies. The Decodon-Persicaria 

 Formation forms soil quite rapidly and upon the emergence of the 

 soil above the ordinary water level the following structure takes 

 possession: 



The Cephalanthus-Cornus Thicket Formation. 

 Facies: Cephalanthus occidentalis, 

 Rosa Carolina, 

 Cornus stolonifera. 

 Secondarv Species: 



Salix liicida, Persicaria laurina, 



Salix cordata, Alisma plantago-aquatica, 



Lathyrus palustris, Scirpus americana, 



Typha latifolia, Eleocharis intermedia, 



Calamagrostis canadensis, Lathyrus palustris. 



Towards the southern end of the pond there is a patch of wet 

 meadow constituting a remnant, probably, of a once somewhat 

 larger Calamagrostis Wet Meadow Formation. The latter for- 

 mation is represented on Presque Isle bv the strong Cladium- 

 Calamagrostis Wet Meadow Formation, which, on lagoon banks 

 with gentle slopes and correspondingly wide habitat zones, con- 

 stitutes an important formation following the rushes and preced- 

 ing the thicket stage . Cladium does not appear on Cedar Point 

 but the Calamagrostis canadensis Wet Meadow Formation, really 

 a consocies only of the northward-ranging Cladiutn-C alamagrostis 

 formation, is well developed in the Cedar Point marsh succession 

 and will be discussed further under that head. 



In the Cephalanthus-Cornus Thicket Formation there is 

 usually more or less of a mixture of the facies but sometimes a 

 more definite structure is evident. Where there is a segregation 



