I9I3-1 STEVENSON— FORMATION OF COAL BEDS. 47 



foot coal into the underclay. D, White, in a letter, says that, during 

 his studies in Kansas and Missouri during 1912, he failed at only 

 one mine to find satisfactory evidence of roots in situ in the under- 

 clay. At one locality in Kansas, the sandy fireclay contains beauti- 

 fully preserved interlaced vertical roots while at others in both 

 states absolutely good roots are present. 



Bennie and Kidston^'' found spores abundant in underclays, espe- 

 cially within the first 2 or 3 inches below the coal ; they cite two 

 localities in which the lower part of the thin clay is barren while the 

 upper portion contains the forms abundantly. 



Underclay without coal is by no means rare. Sometimes it 

 underlies black shale with plants in situ; in some cases it alone marks 

 the horizon which elsewhere shows a coal bed. In other cases, it is a 

 " forest bed," marking a locality where conditions did not favor 

 accumulation of plant material or where the coal was removed by 

 erosion. Dawson has described many of these and Grand'Eury says 

 that the phenomenon of vegetable soils is as familiar in the Loire 

 basin as it is in Canada. Strahan^^ has given a recent illustration. 

 In the new South Dock excavation at Cardiff, 11 feet of gravel 

 underlies 19 feet of brown and blue clay with some sand. In this 

 gravel were found several upright stumps, about 2 feet high, " rooted 

 in a black clay with stems, the roots extending down into the 

 red marl." 



Boulders have been found in the underclay. Ashley^- states that 

 the underclay of Coal IV. is soft and fine but, in places, full of 

 bowlders. This is the only American record, aside from an incidental 

 note by Gresley, that the writer has discovered, but he has been 

 assured that waterworn fragments do occur in the underclay. Ap- 

 parently they are not numerous enough at most places to attract 

 attention and the occurrence may be regarded as infrequent. Most 

 probably, the pebbles were laid down on the river plain prior to 



^^ J. Bennie and R. Kidston, "On the Occurrence of Spores in the Car- 

 boniferous Formation of Scotland," Proc. Roy. Phys. Soc. Edinh., Vol. IX., 

 1888, pp. 102, 103. 



^^A. Strahan, "Geology of South Wales Coal-Field, " III., 1902, p. 94. 



" G. H. Ashley, " The Coal Deposits of Indiana," 23d Ann. Rep. Geol. 

 Surv. Ind., 1899, p. 543. 



