194 BOTANICAL GAZETTE [march 





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Besides these plant remains there are certain animal derivatives 

 characteristic of allocthonous peat; for example, ejecta from fish and 

 small aquatic animals, often containing pollen, diatoms, and bac- 

 teria; chitinized portions of insects; spicules from fresh water 

 sponges; infusorial bodies; and shells of mollusks and protozoans. 



In contrast to the usual inclusions in allocthonous peat (pollen, 

 diatoms, spicules, idioblasts, etc.) there is the strictly autocthonous 

 peat composed of more or less disorganized plant debris. A 

 superficial examination of this material shows a light brown fibrous 

 or dark brown granular texture, depending upon whether or not 

 the included plants are herbaceous or woody. If the substance 

 is more completely decayed, owing to prolonged maceration and the 

 action of fungal enzymes (unhindered by a constant water covering 

 as is true of allocthonous layers) , the fallen plants may become so 

 structureless that they resemble humus rather than peat. Under 

 the microscope this form appears quite homogeneous in contrast 

 to the more fibrous and less decayed in situ peats, but seldom do 

 the distinguishing features of lacustrine peat appear, only a tangled 

 mass of roots, stems, and leaves in all stages of decay. 



Thus it is apparent that there are two distinct types of peat, 

 presenting structures each peculiar to itself, dependent upon the 

 mode of deposition. If a specimen of coal, therefore, can be 

 shown to present a structure analogous to either of these two more 

 recent formations, it is but natural to assume that its composition 



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is due to similar processes of deposition. Strangely enough, this 

 has not been the usual mode of reasoning. Although it is authori- 

 tatively asserted that by far the greater number of the peat deposits 

 in the United States are allocthonous in origin, a diametrically 

 opposite view is maintained in respect to the genesis of coal beds. 

 Consequently it will be the object of this paper to show (i) that 

 these two types of peat are microscopically distinct; (2) that some 

 of the bogs (especially swamps) are not, as is usually believed, of 

 in situ derivation, but filled lakes in which the peat mainly repre- 

 sents the lacustrine or open water phase; and (3) that coals in 

 general show clearly the organization of allocthonous peat. 



The methods used in carrying out these investigations were as 

 follows: Samples of different types of peat were carefully chosen 



