IN THE STRATA OF THE CARBONIFEROUS SERIES. 52 



XII, and terminate in the papillary eminences of the surface of the stem. 

 They are seen cut obliquely in the transverse section of the stem, repre- 

 sented by Fig. 3. of Plate XII., where they constitute the white oblong 

 markings dispersed in the brown parenchymatous tissue. 



Fig. 4. Plate XII. Represents a longitudinal section of the stem, in 

 which these bodies are seen, as regularly arranged as the papillae of the sur- 

 face to which they proceed. 



These processes from the central axis or pith, are embedded in cellular 

 tissue, constituting the great mass of the stem. In the transverse section 

 of the stem, this cellular tissue presents the appearance of pretty regular 

 meshes, assuming more or less of a polygonal form, as seen in Fig. 5, b. 

 Plate XII. The cellular tissue is more condensed towards the surface of 

 the stem, as is represented at c in the same figure, which also shews at «, 

 the appearance of one of the processes, in which the cellular tissue and ves- 

 sels have been thrust aside, and the cavity filled by calcareous spar. 



The meshes of the general mass of cellular tissue are somewhat elon- 

 gated in the longitudinal direction of the stem, but present the same gene- 

 ral appearance, as may be seen in Fig. 7. Plate XII., in which there is al- 

 so one of the processes partially filled by calcareous spar. 



The cellular and vascular nature of these processes is pretty distinctly 

 seen in a transverse section of one of them, Fig. 6. Plate XIII., which, 

 though considerably altered, shews the appearance of vessels in the centre, 

 and cellular tissue in the other parts. In the surrounding dark portion, 

 the tissue is obliterated. The oblique section, Fig. 7. Plate XIII., shews 

 one of these processes near its insertion into the leaf, and bears a consider- 

 able resemblance to one of Lycopodium clavatum, Fig. 9. Plate XII. 

 Fig. 6. Plate XII. represents an oblique section, in which the meshes are 

 more entire than usual. 



From certain indications presented by some of the transverse sections 

 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, of Plate XIII. 



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 trans- 



