SIGILLAIIIA AND STIGMAEIjE. 



201 



Mr. Brown remarks, that these short thick tap-roots were evidently adapted only to a soft 

 wet soil, such as we may conceive was the nature of the first layer of mud deposited upon a bed 

 of peat which had settled down slightly below the level 

 of the water. He supposes, from the presence of a 

 layer of shale without fossil plants immediately over 

 the coal, that the prostrate stems and leaves which 

 occur in such large quantities in the next superincum- 

 bent bed, fell from trees growing on the spot, and were 

 entombed in layers of mud held in suspension in the 

 water, which at short intervals inundated the low 

 marshy ground on which they grew ; for had the 

 plants been drifted from a distance, he conceives they 

 would also occur in the first layer of shale, as well as 

 in those higher up. 



Having thus shown that the Sigillaria alternans 

 was provided with roots adapted for a soft muddy soil, 

 Mr. Brown next describes the specimen represented in 

 Fig. 6, which is the stem of the same species of tree 

 broken off near the roots ; the hollow cylinder of bark (a) having been bent down and doubled 

 over by the pressure of the surrounding mud, so as effectually to close up the aperture, leaving 



irface of Fig. 3, showing the c 

 of the tree, -ys natural size. 



Fig. 6. 



STEM OF A SIGILLARIA BROKEN OFF CLOSE TO THE ROOTS, 



only a few irregular cicatrices, of three or four inches in length, converging at the apex ; tlie 

 structure, arrangement, and number of the tap-roots, as well as the horizontal ramifications, are 

 similar to those in Fig. 5. This fossil clearly explains the nature of the " dom(;-t:/iaped" plant 

 figured in the " Fossil Flora of Great Britain." ' 



" The roots of the preceding fossils repeatedly ramify as their distance from tlie stem 

 increases, and ultimately terminate in broad flattened points. The whole of the spreading roots 

 of these trees (the Sigillarics) cover only an area of thirty square feet each; whilst those of the 

 Lepidodendron (Fig. 1), whose stem is only two or three inches larger in diameter, covered 

 a space of two hundred square feet. Since it is well known, from numerous examples, that the 



' The figures 3, 4, 5, 6, and the descriptions, are from the paper of Richard Brown, Esq., published in the Journal of flie 

 Geological Society of London, fbr March, 1849, entitled, "Description of erect SigillariEe, with conical tap-roots, found iu 

 the roof of the Sydney Main Coal, in the Island of Cape Breton." 



