34 Proceedings of the Ohio State Academy of Science. 



northeastern and southern parts of the lake are several islands 

 evidently formed in this way. 



There is evidence here and there of a sixth kind of island. 

 Duck hunters build screens for their boats by driving willow 

 stakes into the bed of the lake. These stakes sprout and if left 

 undisturbed, will develop into a clump of willows around whose 

 bases debris will collect and give rise to a composite vegetation. 

 There is one such clump of sprouting willows just off the shore 

 of the point. Evidently placed there to make a harbor for the 

 boats. 



I have made a detailed study of each one of these five 

 classes of islands and shall give them here in order. 



/. Cranberry Island. 



The island locally known as the Cranberry Marsh, the 

 Marsh, Cranberry Island or Cranberry Bog, lies in the eastern 

 part of the lake close to and parallel with the north shore. Fig. 

 (12). It is a long, irregularly shaped island, 3,250 feet long by 

 750 feet wide in its broadest part, and has an approximate area of 

 45 acres, according to the survey made in the winter of 1910 by 

 Professor Chamberlin of the Civil Engineering Department of 

 the Ohio State University. This is the only careful survey ever 

 made of the island. The outline is very irregular due to many 

 indentations and small fringing islands. This irregularity has 

 been caused more by submergence and death of the trees, shrubs 

 and other marginal plants, because of the frequent abrupt and 

 extreme changes in water level, than to the growth and expansion 

 of the island. Within recent years the island has been decreasing 

 in size. The storms of winter every year detach fragments often 

 of large size and sweep them away. 



This island is a Sphagnum-Cranberry bog, and is of pecu- 

 liar interest because, i, its dominant vegetation composed of 

 boreal species, is a relict of early post-glacial times left stranded 

 in the swamp ; 2, because Cranberry bogs are characteristic of 

 regions of higher latitudes and this one is near the southeastern 

 margin of the drift sheet ; 3, because the bog, which must be 



