8 INTRODUCTION TO VOLUME II 



But after considering these carefully Seward concludes {I.e. p. 365) that 

 "there is no evidence which can be adduced in favour of regarding the 

 Hymenophyllaceae as Ferns of great antiquity which played a prominent 

 part in the Floras of the past." 



With regard to the Polypodiaceae Seward remarks {I.e. p. 375) that " we 

 have as yet no satisfactory evidence of the existence of true Polypodiaceae 

 in the Palaeozoic Era." As regards their Mesozoic existence, however, he 

 quotes a probable example in O^iyehiopsis -inantelli (Brongn.) from the 

 Wealden. Various Ferns referred to the Polypodiaceae have been derived 

 from the British Tertiary strata, and these lead on naturally to those Ferns 

 which constitute the large majority of the living species. " It is noteworthy 

 that apart from the absence of Ferns which can reasonably be included in 

 this family, the anatomical features of the Botryopterideae (Coenopterideae) 

 and of the Cycadofilices or Pteridosperms do not foreshadow those of Poly- 

 podiaceous Ferns. On the other hand, as we have already noticed, anato- 

 mical characters of such families as the Gleicheniaceae, Hymenophyllaceae, 

 and Schizaeaceae are met with in certain generalised Palaeozoic types. 

 These facts are perhaps of some importance as supplying collateral evidence 

 in favour of the relatively more recent origin of the dominant family of ferns 

 in modern floras" (Seward, I.e. p. 376). 



From this brief summary, drawn from a reliable source, it will be gathered 

 that the general trend of the results of Palaeontological enquiry runs parallel 

 with that of Comparative Morphology. Together the two methods justify 

 the recognition of certain Families as the most ancient. They are the 

 Coenopteridaceae and Osmundaceae, which have had undoubted Palaeo- 

 zoic existence, and with them may perhaps be associated the Marattiaceae. 

 With the first of these the Ophioglossaceae may be ranked on comparative 

 grounds, though they have not yet been definitely recognised as early fossils. 

 These four Families include all the Eusporangiate Ferns now living. 



The remainder of the Ferns, though prefigured in some measure by fossils 

 of the Palaeozoic Period, first began to assume their ordinal characters in 

 the Mesozoic Period, or later. They will be found to show more or less 

 clear relationship to two relatively primitive Families, viz. the Schizaeaceae 

 and the Gleicheniaceae, both of which became firmly established in early 

 Jurassic times: one, the Schizaeaceae, is characterised by bearing its sori on 

 the margins of the leaves; the other, the Gleicheniaceae, bears them super- 

 ficially. The two series thus consistently defined have been designated 

 respectively the Marginales, and the Superficiales. Both are regarded as 

 having not improbably originated from some common earlier source. The 

 order of treatment of the several Families will follow the lines thus indicated, 

 the most ancient fossil types being taken first. But since the Class of the 

 Filicales shows many indications of polyphylesis, the descriptions cannot 



