.1 



THE OTHER BRITISH FERNS— POLl^STICHUM, ATHTRIUM, CETERACH 



extends from the Himalayas on one side to Greenland and eastern North America on 

 the other. Both the other British species are commoner than the Holly Fern in our flora. 

 P. angular e Presl [P. setiferum (Forsk.) Woynar),* the Soft Prickly Shield Fern, is a 

 woodland plant more frequent in Ireland and the south of Great Britain than in the 

 north and lacking the preference for limestone shown by the other two species. When 

 growing luxuriantly as it often does in parts of Devon it exceeds the Male Fern in size, 



Dai/o//jo/ds 



D/cksoniacece 



Pteroids 



Osmundaceoe 



P/sg/opuriaceoe Gymnogrammoids 



B/echnoids 



eoe 



\ 



\ 



\ 



DryopZ-ero/ds 



Dipf-eroids 



{ 



No British 

 representative 



{ 



Ptendium 



Cryptogrsmme 



Adiantum 



Anogramme 



Blechnum 

 Scolopendrium 



( Dryopteris 

 Po/ysticham 

 Athyrium 



< Asptenium 

 Ceteracti 

 mods/a (n 

 Cystopterts (?) 



Pofgpodium (?) 



Fig. 74. Phylogenetic affinities of the principal genera of British ferns (right-hand column) 



redrawn after Bower (1929, 1935). 



and as in that species the fronds die down in winter except in a very mild climate. 

 P. aculeatum (L.)Roth, the Prickly Shield Fern, is of a much tougher texture and, like the 

 Holly Fern, is normally evergreen in all climates in which it occurs. It is commoner in 

 the north of Great Britain than the south, and is characteristically a plant of rocky 

 ground though it does not usually occur as high on mountains as the Holly Fern. The 

 geographical ranges of the last two species outside Great Britain and Europe are not 

 clearly known owing to their confusion with each other and with non-European species. 



* According to the International Rules the valid name for this species should now be P. setiferum. 

 The retension of the older name of P. angulare for the purposes of this chapter and again in Chapter 9 

 is merely a temporary expedient for the sake of consistency with the principles of nomenclature explained 

 in the Preface. 



89 



