104 



POSSIL PLANTS. 



however much he observed its resemblance in structure to Stigmaria, so as to induce him 

 to believe that the latter plant was the root of the former. As previously stated, Halonia- 

 regularis is most probably the root of Lepidodendron Harcourtii, if identity of structure- 

 can prove it. The vascular bundles and medullary rays can often be distinctly seen in 

 the transverse section of Biploxylon cycadoideum, and in the Stiymaria, with wide spaces 

 between the woody wedges ; but, so far as my knowledge extends, they have not yet been 

 found in Sif/illaria vascidaris and the close-wedged Stiymaria, communicating with the 

 outside of the woody cylinder next to the medullary sheath or the medulla itself. The 

 last-named kind of Sligmana has only been described by Dr. Hooker and myself ; 

 even so exhaustive an author as Professor Schimper does not figure nor allude to one.. 

 In my experience the one kind is nearly as common as the other. 



Up to the present time little information has been published on the organs of 

 fructification of Sigillaria with the exception of the cone described by me in the 

 'Philosophical Transactions,' 18G5, p. 595. That specimen was very imperfectly 

 figured in the woodcut (fig. 6) ; but from the form and arrangement of the bracts, and 

 their resemblance to the form and arrangement of the leaf-scars of Sigillaria organum, \ 

 am strongly inclined to believe that it belongs to some species of Sigillaria. 



The specimen described by Goldenberg does not appear to me to have belonged to a 

 large-ribbed-and- furrowed Sigillaria. It is to be hoped, however, that some cones will 

 soon be met with showing the structure of the central column to be the same as that of 

 8. elegans or S. vascularis, as Avas proved to be the case with Lejjidostrobus and 

 Lepidodendron previously shown in this Monograph. 



The specimen " No. 19 Cone," described at p. 49 of this Monograph, so far as 

 structure goes, is the nearest to that of the stem of Sigillaria vascularis of any that have 

 come under my observation ; but that does not go so far as to prove perfect identity 

 of structure. It affords little evidence of the characters of the spores ; indicating 

 microspores only. 



III. Bibliography. 



In giving a summary of what has been published on Sigillaria it is only possible to^ 

 quote the opinions of those authors who have written on the structure of the plant,. 

 without noticing the numerous writers who have described its external characters. The 

 only exception to this rule is the insertion, at length, of the Rev. Mr. Steinhatjr's 

 Memoir on Sligmaria. This is so full and true a description of the root, its author beings 

 too, the first to surmise that Sligmaria might be a root, that it appears desirable to give 

 the paper at length. The views of the authors are generally given in their own words. 



