91 



XVII. — On the occurrence of Non-Gymnospermous Exogenous Wood 

 in the Lias, near Bristol. By Henry Clifton Sorby, Esq., 

 F.G.S. 



(Read May 15, 1850). 



It has usually been thought, that in rocks of the age of the lias, 

 non-gymnospermous exogenous wood does not occur. When I was 

 at Bristol a few years ago, I purchased of a fossil-dealer, at Clifton, 

 a piece of fossil wood, which he informed me was from the lias at 

 Keynsham : not having at that time paid any attention to the struc- 

 ture of woods, I did not specially remark its non-gymnospermous 

 structure, and therefore did not make such particular inquiries as to 

 its locality as would have been desirable ; and hence the fact of its 

 occurrence in the lias rests solely on the information which I ob- 

 tained from him. Its appearance and chemical composition, how- 

 ever, perfectly agree with those of the coniferous wood so common 

 in the lias, and I therefore think that there is good reason to believe 

 it to have come from that bed. The piece which I possess is only 

 a portion of the stem, and shows very distinctly the surface directly 

 below the bark, but does not extend to the pith ; and, judging from 

 the curvature, the diameter must have been somewhere near one 

 foot. The annual growths are moderately distinct, and about -|th 

 of an inch in thickness. 



The drawing will convey a much better idea of its structure than 

 can be given by description. PL XVI. fig. 1, which, as well as figs. 2 

 and 3, is magnified 100 diameters, is a transverse section, and shows 

 the medullary rays and variously-arranged ducts. Fig. 2 is a longitu- 

 dinal section, showing the structure of the interior of the ducts, and 

 a portion of a medullary ray. Fig. 3 is a tangential section, and also 

 shows two ducts, and the medullary rays cut across ; from which the 

 great proportionate size of the latter will be seen. The sides of the 

 ducts are marked, as shown in fig. 4, which is magnified 200 diame- 

 ters ; but it is only in some few places that this structure is well pre- 

 served, being in many cases much confused, no doubt by decomposi- 

 tion having partially occurred before it was perfectly mineralized. 



