192 BOTAXICAL GAZETTE [march 



is inadequate for reaching substantial conclusions, and therefore 

 it becomes necessary to seek some other means of attack, such as the 

 microscopical study of the material itself. It is evident that the 

 anatomy of coal and peat must be determined before the process 

 whereby they have been formed can be demonstrated clearly. 



Studies of the formation of peat, and consequently coal, may be 

 divided into 3 main .classes: (1) topographical, 2 (2) ecological, 

 and (3) anatomical. 



Topographical features have been considered sufficiently to 

 show that they, especially in relation to coal, are not entirely reli- 

 able as a final factor in determining the origin of all classes of 

 organic deposits. The ecology of peat forming plants likewise is 

 limited in its application, and accordingly will receive only a brief 

 consideration, for two reasons. In the first place, literature is 

 quite complete in its descriptions of the usual zones of growth 

 in sw^amps, including careful enumerations of all species of plants 

 characteristic of them (2, 6, 10, 11). In the second place, these 

 plants as such enter but little into the formation of the major 

 part of our peat deposits. Even in swamps only a very small 

 proportion (4-6 per cent) has been derived directly from this flora 

 growing in situ. As will be shown later, by far the greater portion 

 of our peat deposits represents a sedimentation of macerated 

 plant material in open bodies of water, and as such is not dependent 

 upon any one zone of growth, but rather upon all indiscriminately. 

 For this reason, the two first named branches of the discussion will 

 not be considered further, except for an occasional reference in 

 connection with the microscopical studies of several characteristic 

 peat beds. 



Before discussing any special bog, however, it may be well to 

 introduce a brief description of allocthonous and autocthonous 

 peats as they appear under the microscope. It is possible, of 

 course, to discern with reasonable certainty the methods by which 

 any of our present peat deposits have been accumulated, since 

 one has but to choose his material from clearly defined areas; that 

 is, samples selected from modern lakes present detritus which 



3 Forsaith, C. C, A report on some allocthonous peat deposits of Florida. Part I : 

 Topographical. Bot. Gaz. 62:32-52. 19 16. 



