rgtt] DACHNOWSKI—CRANBERRY ISLAND oF 
efficiency of the soil as a habitat. The soil processes involved 
are an efficient natural process for the maintenance of relative 
productivity. Differences in the mineral components are — 
compared with the biological processes. 
The sum total of the reactions in any stage of the process 
exercises a physiologically selective function upon invading plants, 
furthering the growth of such plants whose roots are not merely 
absorbing organs, and excluding and eliminating all others in 
which the power to make extracellular changes in the soil is ineffi- 
cient. 
The significance of the data calls, however, for still further 
experimentation to be of sufficient evidence to assume a specific 
metabolism in bog plants, or to disclose the chemical nature of 
bog toxins. 
Origin of the habitat 
Initially the bog island was formed as are all bogs occurring 
in glacial moraines, or in depressions which form frequently in 
the gravel plains along the lines of drainage from the front of the 
glacial ice. Extensive acquaintance with peat bogs or a com- 
parative study of the lists of plants from different regions will 
convince any careful observer that bogs are very different in char- 
acter, and that not all of them have been formed in the same way. 
There may be a number of possible ways by which such accumu- 
lations of vegetable matter came about. Various such points of 
view and methods of classification have been suggested in a com- 
prehensive study by Davis (11). As the process of bog develop- 
ment here seems similar to that of the peat deposits which the 
writer has observed at Michigan, the following brief account is 
given. 
During the glacial period, most species common to bogs skirted 
the border of the ice sheet. Whatever plant or animal life existed 
“was confined to the highlands east of the Scioto Valley, south of 
the Ohio River, ‘and in the southern portion of this continent. At 
the margin of the ice sheet the conditions must have been quite 
circumpolar in character, similar to those of the barren grounds 
of the far north, that is, there prevailed short summers and long 
winters with frequent winds and storms. Whatever the causes 
