CYCADOFILICALES 



55 



have given rise at least to the more modern leptosporangiate and 

 eusporangiate ferns. It is a type older than the paleozoic Marattia- 

 ceae described above, and it is interesting to note that the sporangia 

 were free, rather than in synangia; the conclusion having been drawn 

 (82) that "the fossil evidence, on the whole, supports the view that 

 free sporangia represent the original form of filicinean fructification. 



Figs. 52-54. — Zygopteris sp.: fig. 52, four sporangia on a common pedicel; Xio; 

 fig- S3> transverse section through the middle of a single sporangium, showing sections 

 of the multiseriate vertical annulus; X 20; fig. 54, longitudinal section of single spo- 

 rangium cut in plane of vertical annulus; X20. — ^After Renatjlt (10). 



and that their cohesion to form synangia was a secondary modificationj 

 though one which took place in certain groups at a very early period." 

 It must be remembered that Filicales are probably so ancient that 

 all of our evidence is relatively modern. 



Two main anatomical types of ferns, therefore, probably existed 

 during the Paleozoic: (i) the complex-polystelic, Marattia-like tree 

 ferns represented by the Psaronius stems, which Scott calls the Paleo- 

 Marattiaceae; and (2) the low, much simpler, monostelic forms, 

 represented by Botryopterideae, and constituting the very ancient 

 synthetic group Primofilices. 



ORIGIN OF CYCADOFILICALES 



Just as it was tempting at first to derive the Cycadofilicales from 

 the Marattia plexus of the Carboniferous, so it was tempting later 

 to derive them, along with modern ferns, from the Botryopterideae 

 (64). To search for the actual ancestral forms of the Cycadofilicales 

 seems to be futile (50), for remains of the group have been traced 



