38 MR ROBERT KTDSTON ON 



more or less the prominent projections of the suberous meshes. To these projections, 

 not wholly obscured by the epiderm, are due the stria; on the cortical surface of the 

 stem. It also extends over the leaf-scars, and blends with the cells which form the 

 cushions. 



The foliar bundles, which spring from the outer surface of the primary bundles, at 

 first rise up vertically in the parenchymatous inner layer of the bark, but at a certain 

 height they bend outwards and penetrate the suberous layer, following the course of 

 the cellular tissue which fills the meshes of the Dictyoxyloid tissue. 



The foliar bundles, at first circular, become enlarged and lunate in form as they 

 approach the surface of the stem. The foliar bundle is always accompanied by two 

 lunate lacunae parallel to its direction, of which their vertical section is an ellipse, 

 limited by a cellular envelope. These two organs, of which it is difficult to ascertain 

 their function, were each penetrated longitudinally by a tolerably large canal, of which 

 it has been impossible to study" the structure. Perhaps they originally contained some 

 gummy substance. It is these lacunae which give rise to the lateral arcs that are seen, 

 one on each side of the foliar bundles of the leaf-scar.* 



The authors of this memoir arrive at a conclusion very similar to that propounded 

 by Broxgxiart, that "by the most essential characters the Sigillaria have the 

 organisation of Dicotyledonous stems, and particularly of gymnosperms, and, above all, to 

 the Cycadacese" an opinion they have since seen grounds to modify, though apparently 

 not entirely to resign ; for in a communication, " Sur les fructification des sigillaires," t 

 after giving the description of a cone which Renault refers to the Clathrarian section 

 of Sigillaria, ami in which he describes the occurrence of pollen sacs on the under 

 surface of the basal portion of the bracts on each side of the medial nerve, he arrives at 

 the conclusion that the Clathrarian and Leiodermarian Sigillaria are Phanerogamous 

 gymnosperms allied to the Cycads, and that the Sigillaria with ribbed stems are 

 cryptogams. \ am not aware that this interesting specimen has yet been figured, nor 



* Note. — In the earlier part of this paper (p. 34) I have remarked that the Sigillaria elegans, whose internal 

 structure was described by Broxgniart in 1839, was now recognised as his Siy. Menardi (in part), Hist. d. 

 ve'ge't. foss., pi. clviii. fig. 6. This again is considered to be only a young condition of Sig. Brardii, Brongt., and 

 to this last mentioned species the Sigillaria .yrinulosa, Germar, must be united as only representing a different 

 state or condition of growth. See Weiss and Sterzel, Die Sigilla/rien </</ preusmchen Steinkohlen-und Rothliegenden- 

 Gebiete, II. "Die Gruppe del Sub-sigillarien," Abhomd der Kiinig J'reuss. geol. Landesanstalt, Neue Folge, Heft. 

 2, Berlin, 1893, p. 84 et seq. Kidston "On Sigillaria Brardii, Brongt., and its Variations," Proc. Roy. Phya. 

 Hoe. Edin., vol. .xiii. p. 233, pi. vii., 1896. But there are great structural differences in the bark of the specimen 

 described l>y BbonOHIABT and that described by Renault and Grand 'Eury, differences which preclude the 



iiility of these two forms of cortex belonging to the same species. 



Two questions therefore arise : — (First) Are the specimens figured by Renault and Grand 'Eury in their 

 memoir on the internal structure of Sigillaria spvaulosa, pi. i. figs. 2-3, really referable to that plant or one 

 of the forms of Sig. lirnrdiil and (.wuiidly) -ranted they do belong to this species, is it proved beyond doubt 

 that the vascular axis described under the name of Sigillaria spmulosa really belongs to the bark found associated 

 with it ' From the crashed and broken condition of the axis and bark shown in their fig. 1, pi. i., the 

 absolute proof thai all these parts belong to the same stem appears to be wanting, and their relative position 

 might In: only accidental. These remarks are made from an examination of the figures and descriptions which 

 accompany them only, as I have not had an opportunity of studying the original specimens. 



t >'nnijiU, rendu . 7th Dec. 188. r >. 



