26 SANDUSKY FLORA. 



distributed on certain islaods should be altogether 

 wanting on others where the conditions for their 

 growth are just as suitable. Moreover we should 

 expect to find that some species not adapted to passing 

 over the water had failed to reach any of the islands. 

 But what we do find is the reverse. Every native 

 species that is well distributed in similar soil on the 

 mainland grows also on the islands and in no case, we 

 believe, is a native species common over one island and 

 lacking on others where similar conditions exist. 



The leading facts bearing on the origin of the island 

 flora may be summarized as follows : Within the 

 present century the waters of Lake Erie and of the 

 bays and marshes connected with it have encroached 

 upon the land in the vicinity of Sandusky, covering 

 many hundreds of acres of ^vhat was, at the time of the 

 first surveys, solid ground. Trees several centuries old 

 have been killed by high water in the present century. 

 Submerged forests have been found in different parts of 

 the region, submerged stalactites and stalagmites in 

 the caves of Put-in-Bay, and submerged river valleys 

 both east and "west of Sandusky- When the trees grew 

 and the stalagmites and valleys were formed, the land 

 must have been above the level of the lake. The valleys 

 are now deeper below the surface of the lake than is the 

 lake bottom between the islands and the mainland. At 

 the time they were formed, therefore, the lake did not 

 separate the islands from the mainland. The flora of 

 the islands is different from what we should expect to 

 find, if all the species growing there had reached them 

 by being transported across the water. It is probable 

 then that many species have been on the islands since a 

 time when these formed part of the mainland. 



We may picture to ourselves woods such as grow 

 at Lakeside now stretching north to Put-in-Bay and 

 Kelley's island, interspersed here and therewith prairies, 

 perhaps, like those on the Peninsula now. We may 



