PART I Y 



SIGILLARIA AND STIGMARIA. 



I. Introductory Remarks. 



In this Part of my Monograph it is intended to give a summary of the present state 

 of our knowledge on the structure of Sigillaria and the alhed plants, rather than 

 descriptions of many new specimens. Further information, however, on Sigillaria 

 vascularis will be given ; and a Stigmaria, not only showing structure in the medulla, 

 but in every respect agreeing with Sigillaria vascularis, will be figured and described. 

 Some additional information on Stipnaria will also be furnished ; and the structure of 

 its rootlets, as well as the remarkable sutures dividing the base of the stem of Sigillaria, 

 will be treated more at length than they have been in my previous papers. 



Since the publication of my views, that large and small specimens of Sigillaria 

 vascularis, as well as Diploxylo7i cycadoideum, had piths formed of barred tubes, and not 

 parenchyma, several authors have doubted the correctness of the description given of 

 my specimens, and asserted that such plants, as well as Stigmaria, had piths of 

 parenchyma similar to those of the Lepidodendron Ilarcourtii described in this 

 Monograph. More evidence will be adduced in support of my views, and it is hoped 

 that it will be conclusively shown that at least one Stigmaria, and that the only specimen 

 of the kind ever described with a pith in a perfect state of preservation, had a pith 

 composed of barred tubes and cells. What was the structure of other Stigmaria, so far 

 as regards their piths, yet remains to be proved ; and Ave must wait patiently for the 

 discovery of specimens in such a state of preservation as to afford us the desired 

 information. This may come any day, now such diligent search is being made for the 

 discovery of Coal-measure Plants showing structure. 



In the present as well as in the former Parts of this Monograph it has been my 

 endeavour to describe the most perfect specimens that could be procured, showing the 

 appearance of the exterior of the plant as well as its internal structure; as I have 

 always found great difficulties in examining imperfect fragments of plants, however well 

 their structure may have been preserved. 



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