THE VEGETATION OF CRANBERRY ISLAND (OHIO) 
AND ITS RELATIONS TO THE SUBSTRATUM, 
TEMPERATURE, AND EVAPORATION. II 
ALFRED DACHNOWSKI 
(WITH ONE FIGURE) 
The atmospheric influences as ecological conditions for growth 
Various theories have been suggested to account for the presence 
and the relative persistence of this northern boreal flora under 
present climatic conditions. Some of these theories have been 
referred to earlier in the paper. Although widely separated from 
the central region of active bog formation with which the local 
bog is now only historically connected, its persistence and exist- 
ence in spite of the climatic changes and animal and plant migra- 
tion and invasion since the last glacial period, and the fact also 
that many peat deposits are reported to occur beyond the margin 
of the Wisconsin ice sheet, suggest that the most significant 
ecological factors are not to be looked for in the continuation of 
limiting conditions similar to those which prevailed when a 
colder climate existed than at present. That bog plants are 
related functionally as well as morphologically, and that they are 
grouped and localized with reference to more or less definite con- 
ditions of their environment is now a fact no longer questioned. 
It is also well known that no formation or plant society is likely 
to be relatively permanent and stationary, for there are changes 
constantly taking place in the environment as well as among 
the dominant plants and their associates. In the bog, however, 
but few successions of plants are in evidence, and the treatment 
of the vegetational societies from the standpoint of floristics and 
succession is therefore relatively free from complications. On 
the other hand, the determination of the factors in bog habitats, 
and the more detailed study of the dynamics of the process, that 
is, how some factors are related, their influence and duration— 
this phase of the problem is still in a state of uncertainty, and the 
methods of study have been all but satisfactory. When one con- 
Botanical Gazette, vol. 52] [126 
