72 STEVENSON— FORMATION OF COAL BEDS. [April i8, 



stump as mineral charcoal, while, in another, a trunk was seen, re- 

 duced to little more than coaly fragments, surrounded by a broken, 

 partly crushed cylinder of bark. His study convinced him that the 

 bark of Sigillaria and allied plants gave the bright coal, while wood 

 and bast tissues yield mineral charcoal, the dull coal coming from 

 herbaceous plants and mold. 



Goeppert^^ found in the coal itself not only the plants which char- 

 acterize the accompanying shale, but also many other species, espe- 

 cially of Sigillaria. The coal contains, in areas studied by him, 

 Stigniaria, Sigillaria, Caulopteris, Calamites and other types forming 

 stratified beds, 30 to 40 feet thick. Of the stems, only the rind re- 

 mains and that is pressed flat. Where the chemical change was long 

 continued, the features of the rind disappeared and the coal became 

 structureless ; but he often saw structureless coal pass into that with 

 well-defined structure. At some localities the coal is composed of 

 Araucarian stems and Stigniaria, while at others Lepidodendron is 

 so abundant that one can hardly find a piece not containing that plant. 



Grand'Eury*^^ says that Stigniaria is very abundant in the coal of 

 Rive-de-Gier ; that Cordaites forms the greatest part of the coal in 

 mines near Saint-Chaumond and in those of the Chazotte ; it seems 

 to be almost the only form in the coal of Tartaras, but is associated 

 with ferns at Peron Midi and at Gandillon. At some places near 

 S'aint-Etienne, Sigillaria makes up practically whole beds of coal. 

 Conditions are similar in other parts of Europe. He cites von 

 Ettinghausen, who states that, at Radnitz, the coal- forming plants 

 are Sigillaria and Stigniaria, with Lepidodendron and Calamites, but 

 the latter two as well as the ferns are unimportant. Grand'Eury 

 found similar conditions at Eschweiler, Wurm, Essen and Saar- 

 bruck ; Geinitz called the Plauen deposit, Calamites coal. But 

 Grand'Eury emphasizes the fact that a coal bed has not been formed 

 by any single kind of plant. He remarks that occasional specimens 

 of stems are found, converted into carbonized wood, showing the 



*" H. R. Goeppert, " Prize Essay," 1848, pp. 6g, 70, 72-75, 276, 277, PI., 

 Fig. XVI. 



*" C Grand'Eury, " Flore carbonifere du Departement de la Loire et du 

 Centre de la France," Paris, 1877, pp. 153, 168, 212, 213, 259, 396-398. 



