10 BULLETIN 802, U. S. DEPARTMENT OE AGRICULTURE. 



immaterial; one is as important as the other, for each is correlated 

 with the other. Any attempt toward clarity of terms and state- 

 ments, any definite determination of criteria for the classification or 

 selection of peat deposits and their materials for agricultural or 

 manufacturing purposes depends upon and includes a twofold qualifi- 

 cation: (1) The botanical composition and stage of disintegration of 

 the peat materials in a deposit and (2) the controlling basic factors in 

 field conditions. These constitute an effectual limitation to the de- 

 gree of success obtainable. The numerous abortive attempts at 

 utilization have invariably followed from neglect of one or the other 

 of these essential qualifying factors. Upon the recognition of these 

 depends whether the farmer and the technician are to work by chance 

 or on scientific lines. 



It is not within the scope of this paper to deal with an ecological 

 account of peat-forming vegetation units, of the character of initial 

 stages, or of series of developmental stages arising in an area of a 

 particular region. These have been discussed elsewhere in consider- 

 able detail (4; 5, p. 220-262). 



Tlie object of these notes is to call attention to the following terms 

 and definitions: 



Peat is an accumulation of plant remains in various stages of disintegration 

 or maceration, laid down in a definite manner according to imposed modifying 

 field conditions. For statistical purposes and for reasons of common scientific 

 interest tlie use of the term " peat deposit '" should be limited to an accumula- 

 tion of plant remains of at least 8 to 10 inches (20 to 25 centimeters) in thick- 

 ness when compact and well shrunk. In this accumulation the surface layer 

 of living native vegetation or deposits containing more than 40 per cent of 

 mineral matter must not be included. 



Muck is a phase of surface i>eat material which occurs under topographic con- 

 ditions permitting extensive weathering and the accumulation of large amounts 

 of silt and clay. 



Humiis. — No definition can be given at present, since the well-known defects 

 in the usual methods of humus determination have made it clear that the use 

 of the term in its present meaning is not advisable either in statements relat- 

 ing to soils or fertilizers. 



Marsh (fen), bog, heath, and swamp are terms used largely on account of 

 the well-marked physiognomy of vegetation which they represent and because 

 they are common names in many languages. The plant remains of each group 

 accumulating as peat are among the most distinctive of peat materials, and the 

 field conditions of each have a more or less difi:erentiating character. The de- 

 posits are quite variable in origin and structure, but their structure is primarily 

 dependent on the form of the land surface on which they are found and upon 

 the height of the water table while they are formed. They are dealt with later. 



The words " marsh *' and " swamp," on the one hand, and " bog " and 

 "heath," on the other, correspond in a' very general way with the terms 

 "Flachmoor" and " Hochmoor " used by most European writers. The line of 

 distinction and the transition betAveen them is, of course, nothing like as sharp 

 as the terms would seem to indicate except in regions having climatic condi- 

 tions where they reacli their best development. " Hochmoor " is applied, as a 

 rule, to a class of peat land which rises from the edges toward the middle and 



