April, 1908.] The Vegetation of Cedar Point. 3°7 



Proceeding to the next oldest lagoon on Cedar Point we have 

 the Lily Pond just to the west of the highest portion of Ridge 

 No. G. The present status of the vegetation around the pond is 

 about that termed, for the succession on Presque Isle, stages 

 "H" and "I". About the Lily Pond on Cedar Point the fol- 

 lowing general vegetational structure appears: 



a. The Potamogeton Formation. 



b. The Castalia-Nymphaea Formation. 



c. The Decodon-Persicaria Formation. 



d. The Cephalanthus-Cornus Thicket Formation. 



e. The Rhus hirta Thicket Formation. 



f. The Ul'.nus-Acer Forest Formation. 



There should be in the deepest part of the pond a Chara 

 Formation, but, for lack of the proper faciHties for studying this 

 vegetation this point was not determined. In similar ponds on 

 Presque Isle there was evidence of a central Chara formation, 

 although Pieters found in Lake St. Clair that this formation was 

 usually scanty or entirely absent on a sandy bottom but present 

 on a clay or alluvial bottom. ^^ 



The Potamogeton Formation. 



This formation has here the following structure: 



Facies: Potamogeton pectinatits, 

 Potamogeton natans. 



Principal Species: Utricularia vulgaris. 



Secondary Species: 



Naias flexilis, Vallisneria s-piralis, 



Philotria canadensis , Potamogeton sp. 



The Castalia-Nymphaea Formation. 

 This formation is perhaps relatively of more importance in 

 the vegetational structure here than is the preceding formation:. 

 Its structure is essentially as follows: , 



Facies: Castalia tuberosa, 



Nymphaea advena. 

 Secondary Species: 



Potamogeton natans, Philotria canadensis, 



Utricularia vulgaris, Potamogeton sp., , ; 



Scirpus validus, Decodon verticillatus . 



This formation, relatively among its competitors, is a rapid 

 soil-former. The plants of the formation typically exhibit large 

 rootstocks, which upon their decay contribute considerably to 

 the accumulation of humus, while the tangled mass of petioles 

 and leaves in and on the water not only catch much floating 

 debris, but, upon their decay, also add to the humus beneath. 



11. Pieters, A. J. TVie Plants of Lake St. Clair. Michigan Fish 

 Commission Bull. 2 : 6 and 9. 1S94. 



