THE FOSSIL FLORA OF THE YORKSHIRE COAL FIELD. 39 



have I had the pleasure of examining it, but as there is absolutely no evidence adduced 

 to show that the fructification under discussion belongs to Sigillaria, I cannot accept 

 the deductions drawn from it as throwing any light upon the affinities of that genus,* 

 especially when cones undoubtedly belonging to Sigillaria, which have been described 

 by Zeiller, and other specimens possessed by myself presently to be described, have an 

 entirely different structure. 



Mons. Grand 'Eury, in the introduction to his Geologie et Paleontologie du Bassin 

 Houiller du Gard, t after reviewing the evidence for and against the cryptogamic 

 position of Sigillaria, places them among the vascular cryptogams ; but this opinion is 

 scarcely upheld in the body of the work, for we find under Sigillariostrobus fastigiatus \ 

 the following remark : — " For me, in any case, there is not a doubt that the celebrated 

 silicified Sigillaria elegans from Autun, which is the Sigillaria Brardii with the 

 structure of a Dicotyledonous gymnosperm, has not been reproduced by spores." 



To sum up, it is seen then that those authors who regard Sigillaria, in whole or in 

 part, as Cycadaceous, and Lepidodendron as Lycopodiaceous, base their opinions largely, 

 if not entirely, on the presence of an exogenous zone in Sigillaria, and the absence of 

 such a zone in Lepidodendron. 



Within the last few years much has been done to elucidate the structure of Lepidoden- 

 dron, especially by the late Professor Williamson, who, from the rich material from the 

 beds containing plant structure in Yorkshire and Lancashire, in England, from Pettycur 

 and the Island of Arran, in Scotland, has described in detail the internal structure of 

 many species of Lepidodendron, in which he has proved beyond all doubt the presence 

 in this genus also of a secondary exogenously developed zone of vascular tissue. This 

 exogenous zone does not appear in all species at the same relative age ; in some it occurs 

 in comparatively small branches, as in Lepidodendron selaginoides, Carr. (? Sternb.), 

 while in others, like Lepidodendron Wunschianum, from Laggan Bay, Arran, it only 

 appears in advanced age. Lepidodendron Wunschianum may therefore be taken as 

 serving to point out the general structure of Lepidodendron when compared with that 

 of Sigillaria, especially as its anatomy, from very young twigs to old stems, is known. 



In the earliest condition the vascular cylinder of Lepidodendron Wunschianum 

 consists of a solid circular bundle devoid of any medulla. As growth proceeds a small 

 medulla appears in the centre of the vascular bundle, and as the medulla increases in 

 size, the vascular bundle is carried outwards, and eventually, when all increase of the 

 medulla has ceased, the primary vascular bundle appears as a zone of considerable size, 

 composed of scalariform tissue of tolerably equal diameter, the transverse bars of which 

 are again connected with fine transverse lines. 



* See also in regard to the affinities of Sigillaria : — Renault, Cours d. botan. foss. Premiere Anne'e, 1881, pp. 125, 

 151. Renault, " Structure comparee de quelques tiges de la flore carboniiere," Nouvelles Archives du Museum de 

 Paris, 2e. ser., vol. ii. p. 213, 1879. Dawson, " On New Plants from the Erian and Carboniferous, and on the 

 Characters and Affinities of Palaeozoic Gyranosperms," Peter Redpatli Museum, M'Gill University, Montreal — 

 Notes on Specimens, 1890, Canadian Record of Science, January 1890, p. 19 et seq. 



t St Etienne, 1890, pp. 196-197. + Grand 'Eury, loc. cit., p. 258. 



