120 



l^OSSIL PLANTS. 



" In the middle of the large cylinder last described is a smaller one, about jt\\ of an 

 inch in diameter. This is composed of large hexagonal vessels, of irregular sizes [a, a), 

 placed one beside the other, without order, but becoming smaller as they approach the 

 circumference, all having their sides barred with transverse strise, and some of the smaller 

 ones {a, a] being divided at short intervals by horizontal and oblique partitions. The 

 outside of this inner cylinder^ {b, b) is composed of hexagonal cells, barred with trans- 

 verse striae, about -^-th of the diameter of those contained in the centre, arranged in 

 radiating series of a wedge shape, and divided by medullary rays or vessels very finely 

 barred (c, c) as in the vascular cjdinders of Sigillaria and Stipnaria, respectively 

 described by Brongniart and Hooker. Around and placed next to the cylinder are .a 

 number of round bundles of fine vascular tissue {d, d), some of which are opposite to the 

 medullary rays or vessels, and others apparently away from them, near the wedges of the 

 wood. These bundles seem to be connected with the vessels Avhich supply the leaves, 

 but cannot be well traced to the medullary rays in all cases. It is probable that they 

 may be sections of vessels passing from the meduhary rays, or vessels, to the leaves. 

 They are evidently the same vessels as are figured by Messrs. Lindley and Hutton 

 ('Fossil Flora,' vol. ii, PL 99, fig. 1), and also resemble the vessels described by Bron- 

 gniart as occurring on the outside of the woody cylinder in Si(jiUaria elegans. On the 

 external portion of the outer radiating cylinder of the specimen similar vessels can be 

 distinctly traced into the projecting scars from whence the leaves arise. 



" Next occurs a space of about i-j-ths of an inch (e, <?), in which the tissue has for the 

 most part disappeared and been replaced by mineral matter ; but it seems to have been 

 composed of delicate cellular tissue, which was traversed by bundles of vessels leading 

 from the axis to the leaves. Then comes a zone of coarse cellular tissue (/, f) which 

 gradually passes into small elongated utricles, of hexagonal form, and arranged in 

 radiating series, which probably formed the inner bark. These in their turn pass into a 

 black carbonaceous matter Qi, h), the remains of the outer bark of the tree. The vessels 

 traversing the external cylinder are of the same character as those traversing the internal 

 one, except that they are of much greater size, each of the latter being probably com- 

 posed of two or more of the former, as Dr. Hooker describes in Sicjillaria?' A transverse 

 section of the specimen ' No. 1 ' is similar to the same section of Sifjillaria elecjans, with 

 this exception, namely, that the inner lunette-shaped bundles of vessels found within 

 and next to the woody cylinder in M. Brongniart's specimen fill the whole of the central 

 axis in mine. At first sight it might have been supposed that the specimen of Sigillaria 

 elegans beforenamed had some of its middle portion destroyed, and that the lunette- 

 shaped bundles once occupied the whole of the central axis ; but having by the kindness 

 of M. Brongniart been permitted to examine the original specimen preserved in the 



^ " In this specimen by some cause a portion of the inner cylinder has been destroyed, either by the 

 section not being cut true or by a part of the woody cylinder having been destroyed in calcification." 

 2 " ' Memoirs of the Geological Survey of Great Britain,' vol. i, part ii, p. 436." 



