162 



LYCOPODIALES 



[CH. 



Fig. 179, C, X, shows the characteristic form of the primary 

 xylem edge, beyond which are seen oval or circular leaf-traces 

 with a mesarch protoxylem, It, px. It is possible that this 

 specimen may not be specifically identical with Witham's species, 

 but it represents a very similar if not identical type ; it may on 

 the other hand be referable to L.fidiginosum. The importance 

 of the specimen, apart from its precise specific position, is that 



Fig. 179. A — D. Lepidodendron Harcourtii, Witham. 



E. Lepidodendron fuliginosum, Shore, Lancashire. 



A, B. From a specimen in the Williamson Collection, British 



Museum (No. 380), from Airdrie, Scotland. 

 C, D. From sections in the Collection of Dr Kidston, from Shore, 



Lancashire. 



it serves to illustrate the general appearance of the xylem 

 surface met with in both species, L. Harcourtii and L. fuligino- 

 A tangential longitudinal section, taken through the 



simi. 



line ab in fig. C, is represented in fig. 179, D. The xylem of 

 the leaf-traces It, consisting chiefly of scalariform tracheae, 

 alternates with patches of crushed and delicate parenchyma which 



