G. W. Bulman — On TJnderclays. 355 



even when these are entirely distinct and separate from Coal-seams. 

 Thus examples of sandstone with Stigmarian roots, and separated 

 from Coal-seams by beds of underclay, occur in the following- 

 sections from the Survey Memoir of the Yorkshire Coal-field : 



FT. IN. 



(1). Coal ... ... ... ... ... 3 



Underclay ... ... ... ... 1 1 



Sandstone with Stigmaria rootlets ... ... 2 (p. 634.) 



(2). Coal 1 3 



Underclay 



Sandstone with Stigmaria rootlets. ... 



And examples of Stigmaria in limestone are not unknown. Thus 

 they are found abundantly in the well-known Burdie House lime- 

 stone of the Lower Carboniferous of Scotland. 



Supposing that in all three cases, in the underclay, in sandstone, 

 and in limestone, the Stigmaria are in situ, it is a little curious that 

 a plant which habitually grew in a swamp caused by an impervious 

 stratum of underclay should flourish equally well on a sandbank or 

 on a calcareous mud. It may, however, be suggested in explanation 

 that the Stigmaria roots represent more than one type, and were not 

 all marsh plants. And to suppose that Stigmaria in sandstone are 

 usually in situ is to increase the necessary number of old land 

 surfaces preserved in the Carboniferous period, already a serious 

 difficulty, reckoning Coal-seams and underclays alone. 



x\s regards the question of the position of Stigmaria in situ, and 

 their connection with the stems of the Carboniferous trees, it is to 

 be noted that the most striking examples that have been brought 

 forward are not in underclay but in sandstone. Thus the well- 

 known case quoted and figured by Prestwich (Geology, vol. ii. 

 p. 109), is in a sandstone. Moreover, the figure gives, on the 

 whole, rather the impression of drift than growth, in situ. And in 

 that remarkable fossil forest near Sheffield, described by Dr. Sorby 

 (Q.J.Gr.S., August, 1875), the roots of the trees ramify through a 

 soft shaly clay, while the stumps are enveloped in a bed of sand- 

 stone. In the South Joggins section, too, and in the Cape Breton 

 Coalfield, the more striking examples of stems with Stigmarian 

 roots are found in the shale above the Coal-seams. 



The occurrence of erect tree-stumps in connection with Coal- 

 seams is certainly suggestive that the underclays have played the 

 part of soils. And yet the very fact of the publication of papers 

 " On an erect tree in connection with a Coal-seam," etc., seems to 

 mark the rarity of the occurrence. But if the underclay really loas 

 the soil upon which was formed the coal by the growth of the 

 Carboniferous forest, afterwards lowered beneath the water and 

 enveloped in shale or sandstone, should we not expect such erect 

 tree-stumps to stand as thickly as the trees in a modern forest ? 



But although the occurrence of erect tree-stumps is rarer than 

 might be expected, Sir Charles Lyell mentions a portion of the 

 South Joggins section, containing nineteen Coal-seams in which he 

 observed seventeen trees at right angles to the planes of stratification. 



