An Ecological Study of Buckeye Lake. 99 



The plankton or floating microscopic organisms have not yet 

 been studied. 



During periods of low water large areas of peat are exposed. 

 Such a mat is shown in Fig. 31, close to the margin of Cranberry 

 Island. The tree stumps indicate that it once was a part of the 

 forest zone of the island. The weight of living trees destroyed 

 the buoyancy of the mat and caused it to sink. The death and 

 removal of the timber released the load holding it down, then the 

 lowering of the water and the warming of the mat caused the gases 

 contained in the peat to expand and the peat to rise above the 

 water surface. Every summer during the past five years the 

 water has been lowered from a few to 6.85 feet. As it is late 

 summer when this has been done the peat in the shallower por- 

 tions of the lake, becomes warmed and rises to the surface. Very 

 soon after exposure the surface is covered with Bidens cernua, 

 B. discoidea and B. frondosa, with these are often associated 

 Cyperus strigosus and Echinochloa walteri. Such peat mats 

 bordering Cranberry Island are often veritable carpets of gold. 

 When the water level is restored the peat is submerged and the 

 vegetation disappears. 



Cranberry Island has a longer record. The bog-meadow is a 

 relic of the flora of the climatic conditions which prevailed at the 

 close of each ice invasion, or perhaps more correctly at the 

 beginning of each interglacial period. The vegetation may be 

 very old or it may be post- Wisconsin ; the position of the lake 

 basin on the Wisconsin drift sheet would indicate the latter. 



The meadow was undoubtedly much larger than it now is; 

 but the former extent of the Sphagnum-Oxycoccus mat cannot 

 now be determined. Soundings in the bog show that Sphagnum 

 peat extends to a depth of 14 feet, forming a coarse fibered, 

 loosely aggregated peat, with many water pockets. At 14 feet 

 the core contained fragments of Potamogeton and Scirpus 

 lacustris imbedded in a dark brown plastic peat. The stratum of 

 dark brown peat with sedge remains is approximately 8 feet 

 thick and is underlain by a more or less sandy marl containing 

 small shells ; beneath this varying from the 28-foot depth to the 



