222 LYCOPODIALES [CH. 



briefly described by Prof. Bertrand^ to whom my thanks are 

 due for the two photographs reproduced in fig. 202, B. C. His 

 specimen, from the Pas de Calais Coal-j&eld, shows a ribbed 

 Ehytidolepis form of surface (fig. 202, B). The stele (fig. 202, C) 

 agrees closely with that of S. elegans as described by Kidston, 

 but the ridges on the fluted surface of the primary xylem are 

 more pointed. " In the immediate neighbourhood of the origin 

 of a leaf-trace, the spiral elements form a median band in the 

 middle of a sinus " and from this the leaf-traces are given off. 

 No secondary xylem was found in the leaf-traces at any part of 

 their course. 



Bertrand compares the stele of 8. elongata with that of the 

 type of Lepidodendron represented by the Burntisland species 

 named by Williamson L. hrevifolium (fig. 186) and now usually 

 referred to L. Veltheimianum ; the chief distinguishing features 

 are the greater prominence in the French species of the surface- 

 ridges or teeth of the primary xylem, a feature which occurs in 

 L. Wunschianum, and the detachment of the leaf-traces from 

 the bottom of each sinus (fig. 202, C, It) instead of from the 

 sides of the sinus. It is, however, not clear how far this latter 

 distinction is a real one; in Lepidodendron Wunschianum the 

 leaf-traces appear to arise, as in Sigillaria, from the middle of 

 each sinus. 



Other types of ribbed Sigillaria stems have been briefly 

 described by Scott^, Kidston^ and more recently, by Arber 

 and Thomas^. 



The specimen described by Scott agrees in the main with 

 8. elegans of Kidston and with 8. elongata of Bertrand. 



Kidston's sections of 8. scutellata show a continuous primary 

 xylem cylinder with a slightly and irregularly crenulate outer 

 margin. It would seem that one important diagnostic character 

 in Sigillarian stems is afforded by the degree and form of the 

 crenulations on the outer surface of the primary xylem. 8. scu- 

 tellata has been described also by Arber and Thomas; these 

 authors were the first to demonstrate the presence of a ligule 

 and ligular pit on the leaf-base in a petrified stem, and they 



1 Bertrand (99). 2 g^ott (08) p. 227, fig. 93. 



8 Kidston (07^). < Arber and Thomas (07). 



