THE MALE FERN DRYOPTERIS FILIX-MAS 



cytogenetics has been fully justified, and while it may be left to the reader to decide 

 whether or not 'the commonest and best known British fern' was really as simple as it 

 seemed, an answer in no uncertain terms has been received to our first general question. 

 By the time that we have diagnosed the existence of polyploid hybrids, of hybrids with 

 hybrids, it has become almost impertinent to ask for further evidence that polyploidy 

 and hybridity do at least exist in ferns. 



SUMMARY 



A brief morphological and cytological description is given of the three taxonomic 

 species into which the Male Fern complex should be split. One of these species, 

 D. abbreviata (Lam. & DC.) Newman, is a sexual diploid with a gametic chromosome 

 number of 41 ; it has various distinctive morphological characters, including small size and 

 an ecological preference for rocky localities in mountains. D. Filix-mas s.str. is a sexual 

 type with twice this chromosome number (i.e. a sporophytic number of 164 and a gametic 

 number of 82). It can be hybridized with D. abbreviata, and from the pairing behaviour 

 in such a hybrid it is deduced that the D. Filix-mas is itself an allopolyploid with half its 

 nucleus homologous with that of D. abbreviata and the other half of unknown origin. 

 D. Borreri Newman owes its specific distinctness to its very characteristic morphology, 

 in which it differs from both the others. It appears to be exclusively apogamous and 

 diploid, triploid, tetraploid and pentaploid strains are known, the last two being almost 

 certainly hybrids between the first two and D. Filix-mas. Further consideration of 

 D. Borreri will be found in Chapters 10 and 1 1. 



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