CHAPTER XXXV 



GENERAL REVIEW OF THE PRIMITIVE FERNS 



In Chapters xviii — XXV the Ferns styled collectively the Simplices have 

 been examined and compared according to the criteria laid down in Volume I 

 of this work. In Chapter xxvi a general survey of the Simplices was given, 

 and their relation to thepalaeontological record discussed, which demonstrates 

 the correctness of the view that in those having a simple sorus we see the most 

 primitive types of Ferns. They are strongly represented in the Palaeozoic 

 Age, though representatives of some of them persist to the present day. 

 Their comparison showed further that according to the position of the sorus 

 two types might be distinguished as represented among them: First, those 

 where the sporangia are borne in close relation to the tip or margin of the 

 leaf, or segment. This feature is held on comparative grounds to be primitive, 

 and the Ferns that show it have been styled the Marginales. Secondly, there 

 have been recognised those in which the sporangia are borne upon the surface 

 of the expanded blade, a feature that is held to be relatively derivative: and 

 these were styled the Superficiales. In the Schizaeaceae a pronounced 

 marginal type is seen: in the Gleicheniaceae a pronounced type of the 

 Superficial Ferns. 



In Chapters xxvil — XXXIV certain Families have been examined which 

 comparison indicates as more advanced than the Simplices, in respect 

 of the sum of their characters, as judged along the lines adopted in Volume I. 

 But since they possess features reminiscent of those seen in the Simplices, 

 though still falling short of the full development seen in the Leptosporangiate 

 Ferns, they have been accorded an intermediate place in the system. Many 

 of them are characterised by having a Gradate sorus, which may be either 

 marginal or superficial. Their sporangia tend towards a smaller size, and 

 the spore-output from each is as a rule smaller than in the more primitive 

 Ferns. They belong for the most part to types which were represented in 

 the Mesozoic Period, while some of the living species correspond very closely 

 with the fossils of Jurassic or even Triassic age. Phyletically they may be 

 regarded as the probable predecessors of the bulk of the modern Leptospor- 

 angiate Ferns, a view which detailed comparative study amply confirms. 



These Ferns of the Mesozoic types fall into several distinct Families, and 

 these again segregate themselves naturally into two groups, the one suggesting 

 relationship to the Schizaeaceae, especially on the ground of their marginal 

 sori, the others suggesting relationship to the Gleicheniaceae, and having 

 superficial sori. It has already been recognised that as the evolution of the 

 Ferns proceeded there has probably been a general tendency to a phyletic 



