Mr. Witham on the Lepidodendro?i Harcourtii. 237 



the longitudinal section, Fig. 2. PI. V., in the latter of which it is en- 

 tirely rilled by calcareous spar, and a tube of carbonaceous matter. This 

 axis consists of a central portion, which in the transverse section, pre- 

 sents rather an irregular cellular texture, around which is a layer of 

 cellular tissue, of large irregular polygonal cells, and lastly, a layer with 

 very small meshes. These appearances are seen in Fig. % a, b ; Figs. 

 4 and 5, PI. VI. In Fig. 2, a, the central part of the axis is destroyed. 



From the central column or axis, emanate on all sides cylindrical 

 bodies, consisting of cellular tissue, with central fasciculi of vessels. 

 They proceed obliquely upwards and outwards, as is seen in Fig. 2, b, b, 

 PI. V., and terminate in the papillary eminences of the surface of the 

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

 stem, Fig. 3, PI. V. where they constitute the white oblong markings 

 dispersed in the brown parenchymatous substance. 



Fig. 4, PI. V. represents a longitudinal section of the stem, in which 

 these bodies are seen, as regularly arranged as the papilla? of the sur- 

 face, to which they proceed. 



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

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

 section of the stem, it presents the appearance of pretty regular meshes, 

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

 The cellular tissue is more condensed towards the surface of the stem, as 

 is represented at c of the same figure, which, also shews at a, the appear- 

 ance of one of the processes, in which the cellular substance and vessels 

 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 

 general appearance as may be seen in Fig. J, PI. V., in which there is 

 also 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, PI. VI., which, though 

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

 cellular tissue in the other parts (in the surrounding parts the regular 

 texture of the parenchyma is altered). The oblique section, Fig. 7» 

 PI. VI. shews one of these processes near its insertion into the leaf, an 



