98 Proceedings of the Royal Physical Society, 



described by Witham in 1832,* numerous articles have ap- 

 peared from time to time, chiefly in the publications of 

 scientific societies, elucidating more fully its structure. 



Among the authors who have contributed to our knowledge 

 of the structure of Lepidodendron since Witham's time are 

 Brongniart, Binney, Dr Dawson,*!" Professor Williamson,^ 

 Carruthers, and Lindley and Hutton.§ 



The study of the organisation of fossil plants is a most dif- 

 ficult one, owing to the imperfect manner in which, in most 

 cases, it has been preserved. 



The greater number of specimens of Lepidodendron that 

 have been described are merely the central portions of the 

 stem, which have become denuded of whole or portion of the 

 bark, by destruction of one or both of two zones of delicate 

 tissue. 



I mention these difficulties, which beset this branch of 

 botany, as some explanation for the unsatisfactory state of 

 our knowledge of the subject. 



The species, Lepidodendron selaginoides, to which the fol- 

 lowing notes refer, has already been described by Professor 

 Williamson in the Philosophical Transactions, in his paper 

 " On the Organisation of the Fossil Plants of the Coal 

 Measures," II and by Mr Binney in the Quart. Jour, of the Geol. 

 Soc.,^ under the name of Lepidodendron vasculare. Mr Car- 

 ruthers has also described a plant under the former designa- 

 tion, " belonging to the type described by Mr Binney under 

 the name of Sigillaria vascularis ;"** but as I agree with Mr 

 Binney in regarding these as different species, there being 

 certain points in their structure which show important dif- 

 ferences, the following remarks do not apply in all points to 

 Mr Carruthers' plant. 



A re-description of this Lepidodendron requires an apology, 

 which must be found in the belief that there are some im- 

 portant points which these authors have failed to observe. 



* Witham, " Fossil Vegetables. " 

 t " Acadian Geology. " Dr Dawson. 2d ed., 1868. 



% Various contributions to the Phil. Trans., entitled, " On the Organisa- 

 tion of the Fossil Plants of the Coal Measures," commencing 1871. 



§ " Fossil Flora of Great Britain," vol. ii. || Phil. Trans., inne 1871, 



H May 1862. ** Trans, of Roy. Mic. Soc, Oct. 1869, p. 179. 



