XIIl] PSILOPHYTON 29 



Dawson as Psilophyton princeps ; while the stem identified as 

 P. rohustius is most probably that of a Gymnosperm. It is 

 doubtful whether a useful purpose is served by retaining the 

 genus Psilophyton. It was in the first instance instituted on 

 the assumption, which cannot be upheld, that the abundant 

 material in the New Brunswick beds bore a sufficiently close 

 resemblance to the rhizome and aerial branches of Psilotum. 

 Psilophyton has served as a name for miscellaneous plant 

 fi-agments, many of which are indeterminable. Dr White 

 concludes his account of the genus with the following words* : 



" The examination of such so-called Psilophyton material as 

 I have seen shows the existence in America of two or more 

 groups, represented by several fairly well-marked species which 

 possess stratigraphical value, and which should be carefully 

 diagnosed and illustrated. It is probable also that additional 

 material throwing light on the structure and relationships of 

 these very remarkable early types of land-plants will be 

 discovered at some locality. The inspection of the material in 

 hand emphasises the need, as was pointed out by Solms- 

 liaubach, for the revision of the material referred by various 

 authors to Psilophyton, together with a thorough re-examination 

 and re-publication of the types." 



Until a thorough re-examination has been made of the 

 Canadian material, with a view to determine whether there 

 exist substantial reasons for the retention of Dawson's genus, 

 it is undesirable to continue to make use of this name for Pre- 

 Carboniferous fossils which are too incomplete to be assigned 

 with certainty to a definite group of plants. Dr White draws 

 attention to the similarity of some of the Perry basin specimens 

 to Nathorst's genus Cephalotheca" from Devonian rocks of Bear 

 Island in the Arctic regions, a comparison which might be 

 extended to other genera and which serves to illustrate the 

 possibility that many of the specimens labelled Psilophyton may 

 eventually be recognised as examples of well defined generic 

 types belonging to more than one group of plants. 



1 Smith and White (05) p. 63. 



2 Nathorst (02) p. 15, PI. i. figs. 18—35. 



