CHAPTER XXXII. 



FILICALES. 



INTRODUCTION. 



OF the Pteridophytes only the Ferns now remain to be examined. They 

 constitute a larger and more varied series than any of those which have 

 gone before, and are especially prominent among those living at the 

 present day. This, together with the fact that in them the observation of 

 the complete life-cycle was first carried through, and is of all the 

 Pteridophytes most easily followed, has given to them a peculiar position. 

 The present-day Ferns have undoubtedly been appraised beyond their 

 deserts as factors in the story of descent. It will be well at the outset 

 to consider how they stand at the moment in the light of such knowledge 

 as we possess of the vegetation of the past, and to compare their present 

 position with the former estimates. 



We have seen that the recognition of the main incidents of the life- 

 cycle in a Leptosporangiate Fern was completed by Suminski in 1848, 

 and it was found shortly after by Hofmeister, that the same scheme 

 coincided in essentials with that of other Pteridophytes. Further com- 

 parison of the organs of propagation, and especially of the sporangia, 

 disclosed the fact that those of the Leptosporangiate Ferns were structurally 

 the simplest. In accordance with evolutionary views which became 

 prevalent about the same time, the general assumption was made that 

 the simplest organisms were those which were also earliest in descent, 

 and that from them all the more complex were derived. On this founda- 

 tion a superstructure of phylogeny was raised. In accordance with these 

 views it became necessary to express the large and complex sporangia 

 of the Lycopods or Ophioglossaceae in terms of those of the Leptosporangiate 

 Ferns: this was effected through the theory of the sporocyst. 1 It was 

 held that by fusion of numerous small sporangia, and elimination of their 

 individual identity the large sporangia of the Ophioglossaceae were 

 produced : by reduction of the whole spike the Lycopod sporangium ; 



1 Strasburger, Hot. Zeii., 1873, No. 6. 



