52 MORPHOLOGY OF GYMNOSPERMS 



ferns in a very uncertain state. It seems certain, at least, that no such 

 dominant Marattia plexus existed during the Paleozoic as has been 

 supposed; for an overwhelming number of the "ferns" constituting 

 it have been placed among the Cycadofilicales, either on direct or 

 on probable evidence. The character of paleozoic ferns, therefore, 

 has become a question bound up with the origin of Cycadofilicales. 



PALEOZOIC FERNS 



The present status of knowledge in reference to paleozoic ferns 

 has been presented recently by Arber (6o), Kidston (64), and 

 Scott (82). For a time, the existence of paleozoic ferns was called 

 in question. The increasing number of known and inferred Cycado- 

 filicales from the Carboniferous, and the fact that the earlier the period 

 the less the evidence of ferns, raised a question as to the presence of 

 ferns in the Lower Carboniferous and Devonian. There is general 

 consent now (59, 61, 82) that ferns existed during the Paleozoic, but 

 not as a dominant group and many of them not to be referred to exist- 

 ing groups of ferns. In fact, Scott (82) states that the evidence is 

 decidedly in favor of the view that a considerable group of Marattia- 

 like ferns existed during the Upper Coal-measures and Permian, 

 side by side with Cycadofilicales of similar habit, but not known to 

 extend to the Lower Carboniferous. When representatives of the 

 living eusporangiate and leptosporangiate ferns are sought among 

 paleozoic plants, they are not recognizable. There is an abundance 

 of annulate and exannulate sporangia; and in general the former have 

 been regarded as standing for leptosporangiate ferns, and the latter 

 for eusporangiate ferns. But some of the exannulate sporangia have 

 been discovered to be the microsporangia of Cycadofilicales; and 

 the annulate sporang'a are very different, both in the character of 

 the annulus and in the structure of the sporangium wall, from those 

 of the modern leptosporangiate ferns. Scott (69, 82) has estab- 

 lished the sporangium genus Pteridotheca to receive the unassigned, 

 petrified, paleozoic sporangia bearing an annulus or with other charac- 

 ters indicating their affinity with ferns; and he thinks that doubtless 

 some of the species belong to true ferns. The paleozoic ferns in 

 general, which were neither leptosporangiate nor eusporangiate 

 ferns in the modern sense, have been called Primofilices by Arber 



