98 



LTCOPODIALES 



[CH. 



and slender acicular needles very similar to those of Firms 

 longifolium; in L, Stemhergii (fig. 141) they are much broader 

 and shorter. In external form as in internal structure it is often 

 impossible to distinguish between the leaves of Lepidodendron 

 and Sigillaria, The distinguishing features enumerated by the 

 late M. Kenault cannot be employed, with any great degree of 

 confidence, as diagnostic characters. In transverse section the 

 lamina of a Lepidodendron leaf presents the same appearance as 

 that of the Sigillarian leaves represented in fig. 142. Near the 



a 



Fig. 142. Leaves of Sigillaria in transverse section. 



A, A'. Section in the Manchester University Museum (Q. 631). 



B, C. Sections in Dr Kidston's Collection. 



base the free part of the leaf is usually subrhomboidal in section 

 with short lateral wings, a ventral keel and two stomatal 

 grooves (fig. 142, A, B, g). The form and arrangement of sto- 

 mata are shown in tig. 143, A, which was drawn from a piece of a 

 leaf shown in surface-view in a section lent to me by Professor 

 Weiss. It should, however, be pointed out that the leaf cannot 

 be certainly identified with Lepidodendron rather than with 



