CHAPTER XXXII 



PROTOCYATHEACEAE 



In Chapter xxvi a general review of the SimpHces has led naturally to the 

 distinction of two main sequences, or ascending series of Ferns. The first 

 includes those Ferns which retain the originally marginal position of their 

 sori (Marginales): of these the Schizaeaceae are a primitive example and 

 the preceding chapters have shown advances while retaining for the most 

 part a strictly marginal position of the sorus. The second comprises those 

 which bear their sori superficially (Superficiales) : of these the Gleicheniaceae 

 are a primitive example. It was further recognised that the distinction by 

 soral position is not absolute, for it is based upon an adaptive change that 

 appears to have followed, earlier or later in descent and probably polyphy- 

 letically, as a consequence of the progressive broadening of leaf-surfaces. It 

 was further indicated that the relatively late and derivative Leptosporangiate 

 Ferns may be laid off as continuations of those two main sequences, being 

 related for the most part more or less directly either to the Schizaeaceae or 

 to the Gleicheniaceae. In Chapters xxvii to xxxi the earlier examples of 

 the derivative Marginales have been described, and reasons have been given 

 for ranking Plagiogyria with them, notwithstanding its superficial sori. All 

 of the Ferns treated in those Chapters may be held as related to such 

 primitive stocks as the Schizaeaceae and Osmundaceae, the latter showing 

 a peculiarly interesting divergence of its two genera in respect of the soral 

 position: for 6>j-;«w^<^rt retains the marginal position, while r^-f^t^r foreshadows 

 the Superficiales. 



Turning now to the Superficiales themselves we shall examine those 

 earlier derivative Ferns which appear consistently to have superficial sori. 

 They may be held as included in or related to the primitive stocks of the 

 Gleicheniaceae and Matoniaceae, Ferns in which we may believe that the 

 sori were established relatively early in a superficial position. The reality 

 of such sequences will depend upon the demonstration of the closeness of the 

 ndividual links. In the present instance a careful comparison will first have 

 to be made between the most advanced Gleicheniaceae, and any outstanding 

 and apparently primitive forms usually classed with the Cyatheaceae. Later 

 a similar comparison will have to be made between the Matoniaceae and 

 certain more advanced types which suggest relation with them, and also 

 share the superficial sorus: viz. the Dipterids. 



It will be remembered that two species of Gleickenia, separated from the 

 rest as the sub-genus Eii-Dicranopteris, are characterised primarily by bearing 



