1 903] BOG PLANT SOCIETIES 4*5 



were encompassed by broad-leaved forests. The oaks, hickories, 

 maples, ash, and elm, following the lines of their specific habitat, 

 the stream valleys or uplands, the sandy stretches left by glacial 

 drainage, or the long lines of clay moraines, surrounded them in 

 their northward progression. 



Probably if the pines, spruce, and hemlock had ever been 

 dominant in Ohio, Indiana, and southern Michigan we should find 

 some evidences of their former occupation by way of isolated con- 

 ifer areas. Excepting the southern and eastern shore of Lake 

 Michigan and two small groups of pines in Ingham and Calhoun 

 counties, Michigan, no conifer areas occur south of the Grand 

 and Huron River valleys. When the early settlers moved into 

 the region of southern Michigan, its forests were of the type 

 commonly known as "oak openings." Probably no type of broad- 

 leaved forest would be more favorable for the preservation of 

 conifer areas had they been dominant for any great length of 

 time after the ice retreat. Where they have been planted within 

 this region, they flourish and attain their normal proportions. 

 Judging by the present distribution of Pinus Strobus and Pinus 

 resinosa, the character of the soil in the vicinity of lakes Michi- 

 gan, Huron, and Erie, and the meteorological conditions 

 associated with these lakes, it seems probable that the conifers 

 have reached their present distribution in the lower peninsula of 

 Michigan by way of the lake shores. Probably the great bulk 

 came by way of the southern end of Lake Michigan and from 

 Ontario. 



In the west, the north, and the east, then, the xerophytic bog 

 societies are still found with their natural associates, the coni- 

 fers (fig. 3] . But in the Ohio valley they have been surrounded 

 by a vegetation which bears no direct relation to them. Nat- 

 urally, therefore, we should not expect to find an order of 

 succession between them. This seems to be the answer to the 

 first question proposed. 



RELATION OF BOG SOCIETIES TO THE SWAMP SOCIETIES. 



This also gives us a new basis for answering the second ques- 

 tion, as to the presence of the bog societies and swamp societies 



