CHAPTER XXXII. 
FILICALES. 
INTRODUCTION. 
Or 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.! 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 ; 
1Strasburger, Bot. Zezt., 1873, No. 6. 
