PTERIDOLOGY 



Btj IRENE MANTON 



University of Leeds 



The Pteridophyta are a central group in the botanical system and their study 

 impinges at once on some of the most fundamental problems of morphology 

 and evolution which have yet been formulated. The interpretation of the situa- 

 tion within the group is profoundly affected by available knowledge of plants 

 of other types (gymnosperms, flowering plants, bryophytes, and algae) and they 

 contribute at least as much to students of other groups as they draw from them. 

 As the oldest known vascular plants on the earth's surface, the fossil Pterido- 

 phyta are indeed of unique importance to the whole of botany and more than 

 in any other group, except perhaps the gymnosperms, the study of fossils has 

 become inseparable from that of the living representatives and colors much of 

 our attitude towards them. 



In the pre-Darwinian period (n.b., Origin of Species, 1859) at the begin- 

 ning of our "century" this was naturally not apparent. It is true that a be- 

 ginning had been made by the pioneer researches of Brongniart (1828-1838) 

 and Goeppert (1841), but effective correlation of fossils with living plants was 

 scarcely possible on the basis of knowledge then available, as is clearly brought 

 out in a work such as that of Lindley and Hutton (1831-1837) in which Bron- 

 gniart 's coal -measure Lycopods {Lepidodendron, Sigillaria, etc.) are discussed 

 as possible dicotyledonous trees. There was indeed considerable uncertainty, in 

 spite of excellent work by great morphologists such as von Mohl, about the 

 fundamental characters for taxonomic separation of even major groups of land 

 plants. This is clearly displayed in standard publications of the textbook type 

 of which Lindley's much-used Vegetable Kingdom is a fair sample. In this 

 (3d ed., 1853) we find Equisetum grouped with the liverworts and before the 

 mosses, Lycopodiales is divided into Lycopodiaceae and Marsiliaceae, and 

 Filicales consist of three families, Ophioglossaceae, Polypodiaceae, and Da- 

 valliaceae. A confusion of this kind can obviously be reduced to order only by 

 a more detailed and accurate knowledge than was available at the time, of life 

 histories, structure (internal as well as external), development, and fossil his- 

 tory, all interpreted with the idea of evolution in mind. In the course of a 

 century much progress has been made in all these lines until one may think 

 that, short of the discovery of wholly new fossil groups, our modern classifica- 

 tion into the major subdivisions of Psilophytales, Psilotales, Sphenophyllales, 

 Equisetales, Lycopodiales, and Filicales (cf. Bower, 1935) is perhaps a true and 

 permanent one. Even this is, however, still subject to change of nomenclature 

 (cf., for example, fig. 2), and when one realizes that the definitive separation 

 of the Psilotales from the Lycopodiales, no less than the discovery of the Psilo- 

 phytales, is effectually the work of the twentieth century (although with pioneer 



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