THE MALE FERN DRYOPTERIS FILIX-MAS 



branched as in that species. No viable spores have so far been obtained from it, though 

 sowings have been made several times. 



It may be mentioned in passing at this point that almost all attempts at defining the 

 species concept include recognition of the necessity of some measure of morphological 



d e 



Fig. 34. Samples of meiosis in the Male Fern complex from sections stained in haematoxylin. x 1000 

 a. Dryopteris abbreviata Newm. Compare with Fig. 36 for details, b. Triploid hybrid between 

 D. abbreviata and D. Filix-mas showing lagging unpaired chromosomes, but also numerous pairs. 

 Compare with Fig. 37 for details, c. D. Filix-mas sens. strict. emend. Compare with Fig. 35 for 

 details, d. Diploid D. Borreri Newm. Note the large size of the spore mother cells which compares 

 with that of D. Filix-mas rather than with D. abbreviata. For explanation of this see p. 58. 

 e. Pentaploid D. Borreri x D. Filix-mas, a wild hybrid. Note much larger cells than in d and very 

 densely crowded metaphase plate. 



distinctness in the species and, usually, of some element of sterility in crosses with 

 other, even though related, species. On the evidence already presented therefore 

 D. abbreviata is almost certainly a species. 



Additional information is obtained by study of meiosis in this hybrid. As already 

 made clear in previous chapters, the numerical details of chromosome pairing at 



51 . 4-2 



