SIGILLARIA. 



103 



specimens. But all these have lost their piths, and fail to give us any information as to 

 what they were composed of. 



Some years since I found a specimen in the " Bullion " seam of coal at Clough Head, 

 near Burnley, having every part of the medulla beautifully preserved ; and, although 

 showing little trace of the exterior of a Stipnaria, it affords undoubted evidence, in its 

 transverse section, of several bell-shaped cavities, from which the rootlets proceeded. In 

 every portion this plant resembles in structure the specimens of SipUaria vascularis, 

 formerly described by me in the ' Quarterly Journal of the Geological Society ' and the 

 ' Philosophical Transactions and, if perfect identity of structure is to be taken as 

 proving the connection of root and stem, this must be held to be the root of that plant. 

 It also shows the occurrence of barred tubes or utricles of very large size, almost as large 

 as those found in my Staffordshire specimen, on which so much doubt had been thrown. 



Another specimen of 8ti(jmaria was found by me in the same locality as the last, 

 having the open spaces between the wedge-shaped masses of wood freely communicating 

 with the medulla, and not bounded by the dark line so marked in my Staffordshire 

 specimen, and the one showing structure from Clough Head. Both specimens exhibit 

 vascular bundles and medullary rays, traversing the woody cylinder alike; but the 

 last-mentioned specimen has lost nearly all its medulla. It is now described for the 

 purpose of showing its difference in structure from the first-mentioned specimen. In my 

 paper on Sigillaria and Biploxylon in the 'Philosophical Transactions,' 1865, it is stated 

 (p. 585) that " the lunette-shaped extremities of the inner radiating cylinder of Bijdoxi/lon 

 cycadoideum, as well as those in my specimen, remind us of a similar arrangement shown 

 to occur in Stigmaria by Dr. Hooker, Plate 2, fig. 14, ' Memoirs of the Geological Survey 

 of Great Britain,' vol. ii, Part I; and they appear to differ from those found in Sigillaria 

 vascularis in not being divided from the central axis by a distinct line of demarcation, 

 just as the same author's Stigmaria, fig. 5, differs from fig. 14. The interior of the 

 inner radiating cylinder of the former plant is more free and open, and not so sharp and 

 compact as that of the latter plant. Indeed, from structure alone it would appear 

 probable that the first-named Stigmaria was the root of Diploxglon, whilst the last one 

 was the root of Sigillaria vascularis." 



In the memoirs published on the structure of fossil plants it has always been slated 

 by me that Lepidodendron was closely allied to Sigillaria; but, as previously mentioned 

 in this Monograph, L. Harcourtii contains a medulla of orthosenchymous tissue, and no 

 inner radiating cylinder ; and, on the other hand, Sigillaria vascularis has a medulla 

 composed of large and small vascular tubes, and an inner radiating woody cylinder. 

 My opinion has been formed from an examination of my own specimens ; and other 

 authors may have reasons, unknown to m.e, for classing Sigillaria vascularis as a Lepido- 

 dendron. 



M. Bronguiart, who has given to the world nearly all the knowledge we possess of 

 the structure of Sigillaria elegans, never supposed that his plant was a Lepidodendron, 



