lO Weiss, XenopJiyton radiadosum (Hick). 



be seen that I support strongly Williamson's opinion of 

 the stigmarian nature of Xenophyton radiculosum, and, 

 briefly, on the following grounds: — 



(i) The general appearance of the fossil, with quin- 

 cuncially arranged rootlets. 



(2) The character of the stele, with its centrifugal 



xylem and broad medullary rays corresponding 

 with rootlet-bundles. 



(3) The organisation of the monarch rootlets differing 



in no particular from stigmarian rootlets. 



(4) The structure of the rootlet-cushion. 



Some of the differences of XenopJiyton from the 

 ordinary StigmaricB will, I think, on second considera- 

 tion, be found to present no difficulties in the way of this 

 identification. 



In connection with the presence of a well-preserved 

 pith, I have already pointed out that this cannot be 

 considered as more than a specific difference at most. 



A more pronounced characteristic of Xenophyton is 

 the small development of secondary wood. If this 

 character was shared by the stem with which Xenophyton 

 was connected, a not unwarrantable assumption, it would 

 point to an association of Xenophyton with a stem such 

 as that of LepidopJdoios, in which genus we have a similar 

 reduction, or at all events retardation, in the formation of 

 secondary wood. 



A more typical feature still is the massiveness of 

 the middle cortex of Xenophyton and its excellent pre- 

 servation. In no known member of the SigillaricE or 

 LepidodendtecE do we find anything so nearly resembling 

 this development as in Lepidophloios fiUiginosus, in which 

 we have both a massive middle cortex and also one which 

 is generally exceedingly well-preserved. The character 

 of its cells, too, though varying slightly in different 



