Page:Transactions of the Natural History Society of Northumberland, Durham, and Newcastle-upon-Tyne 1838 Vol.2.djvu/261

the longitudinal section, Fig. 2. Pl. V., in the latter of which it is eentirely filled by calcareous spar, and a tube of carbonaceous matter. This axis consists of a central portion, which in the transverse section, presents 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. 2 a, b; Figs. 4 and 5, Pl. 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, Pl. 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, Pl. V. where they constitute the white oblong markings dispersed in the brown parenchymatous substance.
Fig. 4, Pl. V. represents a longitudinal section of the stem, in which these bodies are seen, as regularly arranged as the papilla? of the surface, 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, it presents the appearance of pretty regular meshes, assuming more or less of a polygonal form, as seen in Fig. 5, b, Pl. 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 appearance 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 elongated in the longitudinal direction of the stem, but present the same general appearance as may be seen in Fig. J, Pl. 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, Pl. 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, Pl. VI. shews one of these processes near its insertion into the leaf, an