INTxRODUCTION TO VOLUME III 



Noch immer gleicht die Syslematik der Polypodiaceen einem nur teilweise gelicheteten 



Urwald, in welchem sich zurecht zu finden sehr schwer, das Verirren aber sehr leicht ist. 



Von Goebel, A>m. dujardin Botanique de Btiitenzorg, Vol. xxxvi (1926), p. 107. 



The publication of a book that is liable to break off short as questions 

 of special difficulty are approached requires some justification. This Third 

 Volume on the Ferns is a case in point. Of the two preceding Volumes the 

 first has laid the foundation upon which one may proceed in the phyletic 

 study of the Class. In the second the method explained in the first has been 

 applied to those Ferns which comparison has indicated as the more primitive 

 in character, and are actually shown to have been of early existence by 

 evidence drawn from the Earth's crust. But there remains for treatment 

 that vast mass of genera and species which are collectively designated the 

 Leptosporangiate Ferns, or in an older terminology the Polypodiaceae. 

 These are essentially the Ferns of the Present Day. Not only are they 

 more advanced in their organisation, but they are also much more numerous 

 as living individuals, and as genera and species, than those previously 

 treated; moreover they are more definitely standardised in their characters. 

 Consequently they present a much more difficult problem to the mor- 

 phologist who would attempt to group them along phyletic lines. A lifetime 

 is too short a period in which to bring such a study to completion : and the 

 first impulse may be to avoid any general statement that might be received 

 as purporting to have done this. But the obligation that follows from 

 intensive study provides some excuse for a volume, however incomplete, 

 that aims at nothing more than the suggestion of lines for others to follow 

 up by more exact enquiry: and so to complete, to amend, or even to negative. 

 At the close of the Second Volume the relations of the more primitive 

 Ferns, including all those designated the Eusporangiatae, were suggested by 

 a phyletic scheme which is here repeated. This scheme further includes an 

 indication by dotted lines of the affinities of those more primitive types to 

 the main body of the Leptosporangiate Ferns. The natural grouping of the 

 latter will form the main subject of this Third Volume. It is indicated in 

 the scheme that they fall into six large groups, which may probably be 

 regarded from the phyletic point of view as distinct lines of descent. Each 

 centres round some large and well-known genus, upon which its name has 

 been based. The justification of this suggested grouping is to be found in 

 the comparative examination of each phylum. All that is to be attempted 

 here will be to range these large and comprehensive groups along the main 

 lines of natural affinity. It must remain for those who come after, and 



