THE PTERIDOSPERMS 229 



times, but that in subsequent ages it gradually dwindled 

 until now it has tailed off into the few modern tropical 

 species. 



Ferns seem to be as important in the world's vegeta- 

 tion to-day as they have ever been in the past. As a 

 group they have persisted from the Palaeozoic through 

 the Mesozoic Eras to the present time, maintaining a 

 fairly even importance, extinct forms, if not giving rise 

 to, at least being replaced by, new Orders. Efforts have 

 been made, with some show of success, to trace the 

 modern Osmundacese, represented by the well-known 

 Royal Fern (Osmunda regalis) back through Mesozoic 

 relations to the Botryopteridese.* It is surmised that 

 the latter may be a sort of ancient womb from which, 

 after ages of development, a multifarious Fern-progeny 

 has been delivered. 



The Mesozoic Era embraced the Triassic, Jurassic, 

 and Cretaceous Periods, and it appears that nearly 

 all the modern groups of Ferns came into being in 

 the course of the ages involved. The Gleicheniacese 

 (p. 154) have been traced back to ancient Jurassic 

 times — perhaps to the Trias; the Cyatheacese (p. 154) 

 first appeared early in Jurassic times; the Schizseacese 

 (p. 154) are also represented by Jurassic fossils. The 

 Polypodiacese, which are dominant now, seem to have 

 arisen in the Jurassic Period. 



The Pteridosperms, to which some allusion has 

 already been made, and which until quite recently, from 

 the nature of their Fernlike foliage, used to be classed 



* See The Evolution of Plants, chapter on Ferns, by Dr. D. H. 

 Scott. 



