﻿SIGILLARIA VASCULARIS. 



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radiating cylinder of woody tissue ; while lines radiating towards the circumference 

 indicate the outer radiating cylinder composing the inner bark, formed of thick-walled 

 utricles, or elongated cells, of a quadrangular form, arranged in wedge-shaped masses, 

 divided by very coarse cellular tissue, oblong in its transverse section, somewhat like that 

 described by me as occurring in Calamodendron commune, and containing a vascular 

 bundle, also wedge-shaped, but increasing in the direction opposite to that in which the first- 

 named wedge-shaped masses do : all figured of the natural size. The outer bark had been 

 converted into a mass of bright coal, about an inch in thickness. Fig. 2 shows the 

 outside appearance of the fossil in a decorticated state, marked with fine longitudinal 

 striae, irregular ribs and furrows, and some rather indistinct traces of the cicatrices of leaf- 

 scars, which would induce many collectors of coal-plants to class it with a decorticated 

 specimen of Sigillaria. The outer bark of the specimen remains attached to it, in the 

 form of coal, united to the matrix of the fossil. The reverse side of the specimen has the 

 same characters, with the exception of the oval protuberance shown in the plate. 



In Plate XX, fig. 1, is represented a transverse section of the light-coloured disk 

 previously alluded to and shown, of natural size, in Plate XIX, fig. 1, but here magnified 

 4| diameters, exhibiting the central axis composed of hexagonal tubes arranged without 

 order, and of several sizes, those in the middle being rather smaller, but becoming larger 

 towards the outside, where they come in contact with the internal radiating cylinder h, 

 and then again diminishing in size just at the point of junction. This was no doubt 

 originally cylindrical, like the stem of the plant; but both parts, in the process of 

 petrification, have been altered by pressure to their present forms. It consists of a broad 

 cylinder (b), about an inch in diameter, composed of parallel, elongated, tetragonal, or 

 hexagonal tubes, of equal diameter throughout for the greater part of their length, obtuse 

 or rounded at either extremity, and everywhere marked with crowded parallel lines,^which 

 are free or anastomosing all over the surface. The tubes towards the axis are of the 

 smallest diameter ; they gradually enlarge towards the circumference, where they are the 

 largest, though bundles of small tubes occasionally occur among the larger. This cylinder, 

 which may be called the internal woody system of the plant, is divided into elongated, 

 wedge-shaped masses, pointed at their posterior or inner extremities, and parted by- 

 vascular bundles and fine medullary rays, of various breadths, some much narrower than 

 the diameter of the tubes, others considerably broader, but none are conspicuous to the 

 naked eye, except towards the circumference in some few instances. The disarrangement 

 of the tubes of the central axis seems to be the result of the process of mineralization, as- 

 similar appearances have not been observed in many other specimens examined, which in 

 that part are in a more perfect state of preservation. The dark and sharp line separating 

 the vessels of the central axis from those of the internal radiating cylinder does not permit 

 us to clearly see the origin of the vascular bundles or medullary rays which undoubtedly 

 traverse the latter. 



Pig. 2 represents a longitudinal section through the specimen, extending across the 



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