I9II.] STEVENSON— FORMATION OF COAL BEDS. 41 



though without mentioning Mohr in connection with it. Referring 

 to the current opinion that the material for formation of coal may be 

 wholly or at least in great part derived from land plants, he says 

 that this is evidently pure hypothesis, for remains of undoubted 

 land plants occur in coal only under exceptional conditions. As, at 

 the time when stone coal and anthracite were formed, the land was 

 sunken, it is doubtful if the then production of land plants could 

 yield the vast quantit}' required for the coal beds, he is led to look 

 elsewhere for suitable material — and that, the sea plants appear to 

 have produced. Remembering that the fauna of the Coal ^Measure 

 time was marine and that, for these vast numbers of genera and 

 species, the nourishment could come only from algse, he asks with 

 Bischoff, " where are the remains of the vast masses of sea plants, 

 which since the Plant Kingdom first appeared on earth, have grown 

 and then perished?" He replies that they have been consumed in 

 forming coal and anthracite beds ; and he is compelled to admit the 

 conclusion that algse, not land plants, produced the chief material for 

 coal-making. At the same time, he is careful to state that this is only 

 hypothesis, without direct proof, since remains of algse are as rare in 

 coal as are those of land plants. 



Mietzsch*^' devoted much space to discussion of this hypothesis. 

 which he regarded as baseless. His objections are those tabulated by 

 ]\Iuck in the work just cited. In the concluding part of his argu- 

 ment, he points out that the Challenger expedition crossed the ocean 

 along several lines and that the results of dredging leave uncertain 

 whether seaweeds, after death, reach the bottom, become decomposed 

 at the surface or become covered with animal remains. The Chal- 

 lenger expedition found no seaweed on the way to coal, though, 

 several times it crossed the area, where, if ever, such deposits might 

 be expected. Not only the petrography of coal but also the palseon- 

 tology opposes the hypothesis. Seaweeds have not been discovered 

 and the forms known in earlier days as fucoids have proved to be 

 land plants. 



Lesquereux"*' referred to ]\Iohr"s hypothesis only to reject it. 



■"^ H. Mietzsch, " Geologic der Kohlenlager," Leipzig, 1875, p. 244. 

 " L. Lesquereux, Ann. Rep. 2d Geo!. Survey of Penn. for 1885, p. 104. 

 Same for 1886, p. 465. 



41 



