56 BASIS FOR SYSTEMATIC TREATMENT OF FERNS [CH. 



is ranked with the Acrosticheae (III. ix), and Acrostichum, in the Acros- 

 ticheae (ill, ix) far from Pteris in the Pterideae (ill. vi). The Schizaeaceae 

 are not placed in relation to the Hymenophyllaceae, Pterideae, or Marsili- 

 aceae: nor are the Gleicheniaceae placed near to the Cyatheaceae, though 

 there are certain species which seem to hover in their characters between 

 the two. Grounds will, however, be advanced in the course of this work 

 which will tend to support all of these relationships, though they are not in 

 any way suggested by the order of the families in the Engler-Prantl scheme. 



The fact has probably been that up to the present those who have written 

 on the systematic treatment of Ferns have not seriously attempted to trace 

 the relations of the larger groups by descent, or to suggest these by the 

 order of their arrangement. The interest of Pteridologists has been centred 

 in the relations of genera, species, and varieties rather than of families. That 

 this was so in the Synopsis Filicuin{2i) of Hooker and Baker appears evident 

 from the fact that that book was based upon the Species Filiami (26), and followed 

 the sequence of "sub-orders" and "tribes" as shown in it. But as the Osmun- 

 daceae, Schizaeaceae, Marattiaceae, and Ophioglossaceae were not included 

 in the Species Filicuin^ they were added at the end of the book. Convenience 

 in compilation probably dictated this position for them rather than design, 

 though they took a similar place in the sequence of Mettenius. In point of 

 fact the list of families as given in the later systematic works is little more 

 than a catalogue, and so far as their phyletic relations are concerned the 

 families might almost as well have been disposed in alphabetical order as 

 in the order in which they stand. That Sir William Hooker took some such 

 view as this of the succession of families is shown in the Introduction to the 

 Synopsis Filicuni where he speaks (p. xiv) of Presl's system as "the com- 

 pletest Catalogue that has yet appeared." The retention by Engler and Prantl, 

 and by Christensen, of a succession of the families so nearly the same as that 

 of Presl and of Hooker shows that, even up to the present, the results of 

 comparison have not fully found their place in the systematic works on Ferns. 



It may of course be argued that, as it is impossible to represent the 

 phylogeny of any complicated group of organisms in a linear sequence of 

 their names, it is best to take refuge in a mere catalogue. Nevertheless such 

 a catalogue, while it may fall far short of the complicated truth, may at least 

 be so constructed as not to violate those probable relations which comparison 

 and palaeontology together demonstrate. 



Methods of early Pteridologists 



It will be useful to take a backward glance at the methods of the earlier 

 Pteridologists, and to see how the bases of classification have gradually been 

 expanded (28). They first attempted to define species and genera by their 



