Jennings: A Boi'anical Survey of Presque Isle. 367 



a more complete examination would reveal the presence of a Chara 



formation in the deepest water and more or less mixed with the 



Potamogetotis. 



In Lake St. Clair Pieters'^ found that wherever the bottom was of 



clay or of alluvial origin, the " Charace/um'^ covered the bottom 



from the line of the zone of rushes {Scirpus^ to a depth of two to 



seven meters. Where the bottom was sandy the Charas were scarce 



or entirely absent. Although there is every reason to believe that the 



bottom of Cranberry Pond is sandy, it is probably covered with a 



considerable deposit of humus, and it is certain that at least some 



Chara grows there \ where hunters had poled a small boat back and 



forth from the shore a number of good sized fragments of Chara were 



obtained. 



The Castalia-NyviphcBa Formation. 



This formation in places has become a closely packed zone oi Nym- 

 phcBa advena, often twenty-five to thirty feet wide, but more often it 

 consists of a rather weak zone of rather scattering individuals, contain- 

 ing also a few species from the Potamogeton formation, Myriophyl- 

 liim sptcatum, Potatnogeton natans, and Potamogeto7t peciinaUis. In the 

 deeper parts of the zone are a few plants of Castalia tuberosa. 



The Cephalanthtis-Cornus Formation. 



One of the most striking features of distinction between the vegeta- 

 tion of Cranberry Pond and the lagoons to the north and east of Long 

 Ridge is the complete supplanting of the Scirpiis- Typha formation by 

 a zone composed almost entirely of shrubs. The structure of this 

 zone is essentially as follows : 



Fades. — 



Cephalaiiihus occidentalis, Cornus stolonifera, 



Rosa Carolina. 

 Principal Species. — 



Salix cor data, Salix lucida, 



Bidens cernua, Triadenum virginicum, 



Persic aria laurina, Persicaria incarnata, 



Dryopteris thelypteris. 

 Secondary Species. — 



Salix nigra, Salix discolor, 



Nymphcea advetia, Dulichitan arundinaceum, 



'spieters, A. J. "The Plants of Lake St. Clair." Michigan Fish Commission, 

 Bull. 2 : 6, 9, 1894. 



