Jennings : A Botanical Survev of Presque Isle. 379 



is an occasional black oak in the habitat and, although they are as yet 

 merely saplings, they appear healthy and vigorous. 



At the " Head " there is a pond Z (see Plate LI) which constitutes 

 an ecological habitat considerably different from the ponds and lagoons 

 described above. This pond is fed by springs issuing from the lake 

 bluff and it also receives a considerable run-off from the land above 

 — a couple of small streams debouching at this point. As a conse- 

 quence, there is a considerable outward current flowing through the 

 outlet into Presque Isle Bay, and the water in the pond was found on 

 several visits to be several degrees colder than in the ponds out on the 

 peninsula. 



The banks and bottom of this pond are not entirely composed of 

 the clean white sand, which constitutes the basins of the ponds and 

 lagoons on the peninsula, but have a considerable mixture, especially 

 on the landward side, of fluvial material ; around most of the basin 

 there is enough silt and clay mixed with the sand to form a quite com- 

 pact and firm soil. Formerly, the stream now emptying into the lake 

 west of the head of the peninsula, emptied into the bay just inside of 

 the neck of the peninsula, and doubtless much of the soil now com- 

 posing the more landward parts of the head was deposited as a sort of 

 alluvial fan inside of the peninsula. 



The vegetation of the basin of the pond is in many respects quite 

 dissimilar to the vegetation of the ponds and lagoons of the peninsula 

 proper. The sequence of formations on the lakeward side of this pond 

 is as follows : 



(a) Chara Formation, 



((^) Potamogeton Formation, 



(<:) Casialia-NyinphcEa Formation, 



(<-/) Decodon-Persicaria Formation, 



(f) Typha-Scirpiis Formation, 



(/) Carex-Phragmites Formation, 



(^'■) Alnus-Salix Yoxva^XAOXi. 



The Chara Formation. 



As may be seen from the ^V'aldameer Park bridge, which crosses the 

 pond at about its middle, the Chara formation occupies a considerable 

 portion of the deeper part of the pond. The growth is quite dense 

 and quite completely covers the bottom of the pond. 



