238 Mr. Witham on the Lepidodendron Harcourtii. 



bears a considerable resemblance to one of Lycopodium clavatum, Fig. 

 9, PI. V. Fig. 6, PI. V. represents an oblique section in which the 

 meshes are more entire than usual. 



From certain indications presented by some of the transverse sec- 

 tions of the stem, it would seem that bundles of vessels exist round 

 the axis or pith, as seen in Fig. 4, a, a, and Fig 2, e, PI. VI. 



The above is the ordinary structure of the stems as usually observed 

 in specimens ; but in a stem of somewhat greater diameter, of which a 

 transverse section is represented by Fig. 1, PL VI. (much altered), the 

 cellular or parenchymatous tissue is, at the surface of the stem, sur- 

 rounded by a very thin layer of tissue which assumes a remarkable de- 

 gree of regularity, b b. It is seen magnified in Fig 2, d d, which is a 

 portion of a transverse section including the pith, b b., and the other 

 parts to the surface. Fig. 3 shews it more highly magnified. The tis- 

 sue of this superficial layer has a remarkable resemblance to that of the 

 coniferae, the cellules being arranged in parallel series, and of a form 

 approaching to the hexagonal, but without indications of medullary 

 rays. In this more regular portion of the cellular tissue circular vacu- 

 ities are observed, which are probably vasa propria, 



The Lepidodendra are generally supposed to be Lycopodia, or plants 

 allied to them, and there is nothing in the structure of the present 

 species that might tend to invalidate the opinion A transverse section 

 of Lycopodium clavatum is represented by Fig. 8, PI. V., but as I have 

 had no opportunity of examining the structure of any large recent spe- 

 cies, and as no figures of such exist, it does not become me to institute 

 any comparison. Whatever light may be thrown on the nature of the 

 Lepidodendron by the anatomy of the present species, I must leave to 

 others better qualified than myself to point out ; but, I trust, the figures 

 which I have given, will be useful for comparison, should other species 

 occur, in which the structure may be found to have remained. This 

 much is certain, that the plant here described, evidently belongs to the 

 vascular cryptogamic class, and that in its structure there is nothing to 

 invalidate the opinion derived from the external configuration of the 

 Lepidodendra, that they are Lycopodiacias. 



