52 TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW. 



the stem, it seems very doubtful to me if it is possible to regard 

 this little cicatricule above the leaf-scar as indicating the 

 position of an homologous structure to the scale on the leaf of 

 Selaginella. 



If the figure given by Mr. Maslen, already referred to, is a 

 correct representation of the specimen, there appears to be no 

 room for doubt that the ligule there shown is homologous with 

 the ligule of Selaginella, but though in Sig Maria mamillaris, 

 Brongt., Sigillaria Brardii, Brongt., and other Sigillarice, the 

 leaves are placed on more or less prominent elevations, and in 

 Sigillaria MacMurtrei, Kidston, this elevation almost amounts to 

 a pedicel, still all these swellings to which the leaves are attached 

 have a different appearance and structure from the clearly- 

 defined Lepidodendron leaf-scar, and it makes one reluctant to 

 accept as proved beyond all further question the true homologue 

 of the little cicatricule under discussion. 



A similar little cicatricule occurs above the leaf-scar of Bothro- 

 dendron, and in Pinakodendron, Weiss, which is closely related 

 to Bothrodendron, there are two, frequently three, small 

 cicatricules, above the leaf-scar, 1 which it is difficult to regard as 

 different in significance or function from the single cicatricule 

 found in Bothrodendron and in many Sigillaria, and such a 

 plurality of ligules is entirely unknown amongst recent Lycopods. 



It would appear then that though Lepidodendron has some 

 points which accord more with Lycopodium than with Selaginella, 

 especially in regard to the arrangement of its leaves, it has others 

 which point to a closer relation with Selaginella. With Tmesipteris 

 the bundle of those species of Lepidodendron, which have a solid 

 axis devoid of a pith cavity, has a greater similarity than to that 

 of either Lycopodium or Selaginella. 



Like so many palaeozoic types, Lepidodendron embraces within 

 itself characters which we do not now find united in the 

 individual, but which occur in the group, and to attempt to 

 force a special relationship to any existing genus is a course which 

 cannot be advocated. 



1 Weiss and Sterzel, Bit Sigillarim d. Preuss. Sitink. u. Rothiugenden 

 Gcbiete. II. Die Gruppe der Subsigillarien, Abhandl. d. k. Preuss. Gtol. 

 Landesamtalt Xeue Folge., Heft. 2, p. 61, 1S93. {Pinakodendron Ohmanni, 

 Weiss, p. 62, PL III., figs. 17, IS.) 



