

Ul] FOSSIL GXETALES 469 



of the true position of this puzzling group which, despite the 

 lack of palaeobotanical evidence, is probably a survival from a 

 remote past. 



II. GNETALES (FossiL). 



Arber and Parkin 1 and other authors have called attention to 

 the lack of any trustworthy records of Gnetalean plants in the 

 sedimentary strata of different periods. Several specimens have 

 been described either as generically identical with Ephedra or as 

 probable representatives of the two other members of the group, 

 but while some are incorrectly determined others are too im- 

 perfect to be accepted as evidence. In view of the morphological 

 features characteristic of the present members of the Gnetales and 

 the geographical distribution of the species of Ephedra, Gnetum, 

 and Welwitschia, it would seem safe to conclude that the absence 

 of fossil forms is not explicable on the hypothesis of a recent origin 

 of the group, but is rather the result of the imperfection of the 

 geological record and of the difficulty of distinguishing between 

 fragmentary remains of Gnetalean genera and vegetative or repro- 

 ductive organs of similar external form belonging to other plants. 

 Keference has already been made 2 to certain characters shared 

 by the seeds of Gnetum and Bennettites and in spite of the great 

 and obvious differences separating the Gnetales and Cycadales it 

 would seem probable that the striking similarity between the 

 seeds of Gnetum and those of the Bennettitales has some phylo- 

 genetic significance. But even granting a phylogenetic significance 

 to the evidence brought forward by Mrs Thoday and other authors, 

 we have still to admit that an indication of some former connexion 

 between the Gnetales and the Bennettitalean line is rather the 

 shadow of evidence with regard to the geological history of the 

 Gnetales and not a substantial contribution to our knowledge of 

 the antiquity of this section of the Gymnosperms. 



The specimens described by Unger 3 from Eocene beds in Styria 



as Ephedrites sotzkianus, though very similar to those of Ephedra 



Jragilis with which they are compared, are too fragmentary to be 



1 Arber and Parkin (08) p. 507. 2 See page 463. 



3 Unger (51) p. 159, PL xxvi. 



