12 BULLETIN 802, U. S. DEPARTMENT OF AGRICULTURE. 
series of different vegetation stages, each initiated, continuing, or 
terminated and replaced in response to changes of basic past and 
present modifying factors or field conditions. They indicate that of 
the many plants which occupied the area as an association, only the 
few forms or species that were dominant and of rather wide geo- 
graphic distribution contributed to the formation of peat layers. 
The course of the development of a peat deposit may have been 
complete or interrupted, complicated or recurring, according to the 
conditions which prevailed : the resulting layers of peat material are 
certain to be correspondingly continuous or fragmentary and isolated. 
TTherever peat deposits arise, whether in the conversion of wet flat- 
land surfaces or of basins and kettle holes, on uplands, along river 
channels, or at the coast, the essential nature of the process is readily 
established by a comparison of the serial and contemporaneous strata 
of a deposit. The record is indicated by the profile structure and can 
be ascertained and reconstructed only by actually probing the layers 
of plant remains and examining microscopically the more disinte- 
grated materials. 
The stratification of a deposit points therefore to changed life rela- 
tions for the plants which formed peat; to disturbances which 
ensued through altered conditions of rainfall, of soil moisture 
and its content of mineral salts, or in the relation of precipitation to 
evaporation. Unfavorable topographic or soil conditions may even 
arrest the succession of vegetation and keep it stationary at a point 
far short of the possible development within the area, but significant 
is the fact that with further accumulation of plant remains the in- 
fluence of local vegetational or topographic conditions becomes less 
marked, while that of the region or climate gradually increases in 
effectiveness. It is probably for this reason that the older or lower 
layers of peat deposits of the Scandinavian countries, of Holland, 
Germany, Austria, Switzerland, Finland, and Russia appear to have 
a surprising number of features in common with many of the peat 
deposits of the northern portion of the United States. 
There is the possibility of using the present native vegetation to- 
gether with plants characteristic of corresponding types of peat 
material as an indicator and criterion of conditions which may 
serve for a basis of estimating the agricultural and other possibili- 
ties of a peat deposit, provided the relation between the surface vege- 
tation cover, the character of the profile structure, and the nature 
of the field conditions of the deposit is correctly interpreted. It is 
necessary to bear in mind, however, that by itself the surface vegeta- 
tion of any unstable stage in the deveclopment of peat deposits can 
not be regarded as being wholly significant in the determination of 
the latent possibilities of a peat-land area. Much more importance, 
especially from the standpoint of interests combining agricultural 
