32 DESCRIPTION OF FOSSIL TREES DISCOVERED 



from the fragment of trie stem. The latter has been sliced, and shews 

 the concentric rings in a perfection almost approaching to the fossils of the 

 Lias. 



Fig. 5. represents a thin transverse slice, viewed by transmitted light, 

 and of the natural size. The pith is seen to be very large, and there are 

 decided indications of five concentric layers. 



Fig. 6. represents the pith highly magnified. Besides the large aper- 

 tures of the circular cells, there are others of much smaller size, presenting 

 somewhat of the appearance of vessels. 



Fig. 7. represents a portion of a transverse slice, in which are seen the 

 margin of the pith, several medullary rays proceeding from it, and the ordi- 

 nary reticulated appearance of the elongated cellules. 



Fig. 8. represents the breadth of the two inner woody layers, with part 

 of the third. The lines of separation are distinct ; and the medullary rays, 

 together with the series of cellules, are flexuous, probably from accidental 

 distortion. 



The texture is much better preserved, in the branch of which the above 

 figures are representations, than in either of the great stems ; but in all it 

 is similar. 



The analysis of the fragment and branch is as follows : — 



Lime, 37.5 



Peroxide of Iron, 24.2 



Coal, 38.1 



99.8 



It is singular that the composition of these stems should differ so much 

 from that of the enclosing rock. When we find in beds of sandstone and 

 shale, vegetable trunks transmuted into substances of a similar nature, the 

 presence of the sand or mud, and the decay of the vegetable matter, afford 

 an easy explanation of the manner in which the transmutation has been ef- 

 fected ; but when the petrifying substance is different in nature from that 

 forming the matrix of the fossil, difficulties occur. Yet, if we take the 

 whole mass or group of substances constituting a formation, we may find 



