CHAPTER XXVIII. 



CYCADALES (rbceni). 



Among the fossil genera described in the last chapter of the 

 second volume some were spoken of as true Ferns though most 

 of them, it was added, 'may safely be regarded as plants which 

 will ultimately be shown to belong to some other group, in most 

 cases that of the Pteridosperms.' Since this, was written additional 

 evidence has been obtained in favour of the inclusion of certain 

 genera in the Pteridosperms. In the case of Taeniopteris, one 

 of the genera already described, there is reason to believe that 

 at least one species is a member of the Cycadales and not a true 

 Fern as formerly supposed. 



The Pteridosperms so far described are represented for the 

 most part by sterile leaves preserved as impressions, the genera 

 founded on more satisfactory material having been reserved for 

 treatment in this volume. As these genera are founded to a 

 large extent on anatomical characters oscillating in their essential 

 features between recent Ferns and Cycads, it is important that 

 the student should be in possession of the anatomical character- 

 istics of both of these classes ; and for this reason a general account 

 of recent Cycads is intercalated between the Pteridosperms 

 already described and those reserved for treatment in this volume. 



The section of the Gymnosperms known as the Cycadales, 

 represented by nine recent genera and less than 100 species, is of 

 exceptional importance phylogenetically and demands special 

 attention from palaeobotanical students. Familiarity with the 

 morphology of recent forms is essential not only in relation to extinct 

 cycadean plants but also to types which, though not sufficiently close 



