224 



LEPIDODENDREA E. 



from the comparison of the two types by Renault 1 himself. It might 

 indeed be supposed from this comparison that there were important 

 differences in connection with the vascular bundle-trace; but it has been 

 already pointed out, that in Lepidodendron also, exactly as in Sigillaria, 

 the lateral points are most probably not to be taken as belonging to 

 the bundle-trace. From Renault's objections on this point we should 

 expect that the surface of the specimens, the structure of which corresponds 

 to that of the vasculare-type, would bear on it the characteristic marks 

 of Lepidophloiae, since these are the forms in the series of Lepidodendreae 

 which are more like Sigillaria. But exactly the contrary is the case. We 

 find elongated rhombic cushions with the bundle-trace in the normal 

 position, though they do not show the scar of separation, because the 

 epidermis has disappeared in every case which has been observed. I myself 

 possess several specimens of the kind ; others have been figured by Binney 2 , 

 and these are all the more instructive because, having exactly the same 

 surface, they are distinguished anatomically only by the presence or absence 

 of the secondary growth, and were accordingly named Lepidodendron 

 vasculare and Sigillaria vascularis. In this case the surface shows not the 

 least trace of any resemblance to Sigillaria. There is yet another distinction 

 which Renault establishes between the two families, and which rests on the 

 structure of the leaf-trace-bundle ; but this too will have to be noticed 

 again in discussing Sigillariae, and we shall therefore only say what is 

 absolutely necessary about it in this place. Renault states that in Sigil- 

 lariae the bundle is diploxylous, that is, is constructed after the manner of 

 the leaf-traces of Cycadeae, while in the type before us it is monoxylous. 

 Upon this it is to be observed that in this respect there is not the slightest 

 difference between the stems of Lepidodendron vasculare with and without 

 growth in thickness, and of this I have fully satisfied myself from numerous 

 preparations, both transverse and tangential sections. Whether they are 

 diploxylous or not cannot be certainly ascertained until we know whether 

 they belong to the collateral or the concentric type. Nothing at all can be 

 gathered on this point from Renault's 3 figure of his Diploxylon (Anabathra 

 pulcherrima, Witham). It appears then that Williamson 4 is again right in 

 maintaining that Binney's and Renault's Sigillaria vascularis in the young 

 state, before the formation of secondary xylem, would not be distinguishable 

 from a Lepidodendron vasculare. And since we found that the surface of 

 the two forms was the same, and there is therefore an absence of all 

 differential characters, they form together one and the same species. It 

 may be remarked in conclusion that Renault's objections in this matter 

 are the less cogent, because he can have examined little more of the 



1 Renault (2), vol. iii, Introd. p. 4. * Binney (2), tt. 5, 6. * Renault (2\ vol. i, t. 19, f. 2. 

 Williamson (1), XI. 



