12 BULLETIlSr 802, U. S. DEPAETMENT OF AGRICULTUKE. 



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. 

 "Wlierever peat deposits arise, whether in the conversion of wet fiat- 

 land surfaces or of basins and kettle holes, on uplands, along river 

 channels, or at the coast, the essential nature of the process is readil^^ 

 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 tox)ographic 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 Eussia 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 an}^ unstable stage in the devedopment of x)eat 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 



