2o6 REINHARDT THIESSEN 



EXPLANATION OF PLATES 



PLATE III 



Fig. I.— a block of Illinois coal from vein No. 6. The black bands a repre- 

 sent anthraxylon, the grayish bands d represent the layers of "dull coal." 

 The area described by the intersections of the lines x-x' , y-^' and n-n, m-^m' 

 is the same area shown in Figure 2, and bands a-i, d-2, 0-3, J- 4, a-5, d-6, 

 a-7, and (f-8 of the one are correspondent to the other. The lenticular band 

 "CO" represents a cone of Lepidodendron. Natural size. 



PLATE IV 



Fig. 2. — The area described by the lines x-x' , y-y' and n-fi', m-m' in 

 the block of coal shown in Figure i, and enlarged 10 times. The bands a-i, 

 d-2, d-4., a-5, d-6, 0-7, and d-8, representing alternate layers of anthraxylon and 

 "dull coal," of the one being correspondent to the other. Xio. 



PLATE V 



Fig. 3. — A part of a thin cross-section of "bright coal," or anthraxylon, 

 showing more or less well-preserved structure of wood. X 200. 



Fig. 4. — A horizontal cleavage surface of compact coal from the Vandalia 

 mine near Terre Haute, Indiana, showing patches with woody structure or 

 anthraxylon chips, more or less surrounded by structureless areas representing 

 the attritus. "Needles" are also shown. X200. 



Fig. 5. — A part of a thin cross-section of "bright coal," or anthraxylon, 

 with resinous inclusions. X 200. 



Fig. 6. — Part of a thin cross-section of coal from the Pittsburgh seam, con- 

 sisting of a constituent that may be bark. The tissue is large-celled, irregularly 

 preserved, including a considerable amount of resinous matter. X 200. 



PLATE VI 



Fig. 7.— Part of a thin cross-section of coal from Royalton, Illinois, at a 

 low magnification, showing numerous thin chips of anthraxylon, more or less 

 separated by thin layers of attritus. X 10. 



Fig. 8. — A part of the thin section shown in Figure i, at a higher magnifi- 

 cation. Some of the anthraxylon chips have retained their cell structure to a 

 remarkable degree, a comjnon occurrence in most coals. X 200. 



Fig. 9. — A part of a thin horizontal section of the coal from Ziegler, Ilhnois. 

 A random section; the plant structure shown is of common occurrence in any 

 horizontal section. Anthraxylon chips are seen on either side. The circular 

 to oval spots in the attritus in the center represent spore-exines. X 150. 



Fig. 10. — Part of a thin cross-section of the coal from Terre Haute, Indiana, 

 at a low magnification. The numerous grayish bands or strips represent 

 anthraxylon chips; the darker mottled matter between these represents the 

 attritus. X 10. 



