22 BOTANICAL GAZETTE [JULY 
that resulted in such climatic conditions (4) with their change 
and with the progressive northeastward movement of the ice, an 
increasing land area became exposed, the topography of which is 
even now largely the inheritance of that time. While yet the 
entire surface of northern Ohio and the land north of it was buried 
under the ice sheet, the region about Columbus and Buckeye 
Lake was among the first to be laid bare by the retreating ice and 
water. The receding of the ice sheet was paralleled by the north- 
eastward movement of more favorable weather conditions which 
initiated a migration northward of plants and animals along the 
glacial drainage channels, the earliest highways for the dispersal 
of many forms of life (1). As the ice and water continued to 
recede and the processes of erosion brought about better drainage 
and lower water levels, the flora and fauna followed down the 
slopes and began to encroach upon the ponds and lakes. The 
bog plants and their associates slowly had passed northward close 
to the base of the retreating ice, and hence were among the first 
to take possession of the new territory. 
As has been stated, the test borings make it evident that the 
bog vegetation grew out from the shores, forming a floating mat; 
that sphagnum and cranberry appeared after the sedges and rushes 
had built up the surface mat; that filling in of débris from the 
sides continued slowly until the water had become shallow enough 
in places to enable shrubs and trees to occupy the area. The later 
phases of mature bog forests the writer has met very frequently 
in Ohio, and several interesting localities have been studied in 
connection with an inquiry on the peat deposits made for the 
Ohio Geological Survey. 
ile it is not clear how the preservation of the local bog 
island has come about, the present investigation has led to the 
conclusion that a well marked relationship existed between the 
type of peat soil considered with regard to its degree of disinte- 
gration, and the succession of plant associations covering it. As 
elsewhere in Ohio today, the firmer and well decomposed peat 
strata were covered sooner with forests, and were built up rapidly 
by an attendant sinking and shrinkage of the mat under the added 
weight of the growth and fall of trees and the vegetation of suc- 
