THE OTHER BRITISH FERNS— POLTSTICHUM, ATHTRIUM, CETERACH 



confirmed, and confirmation from another source is very desirable, will not necessarily 



invalidate the suggestion of a derivation from Dryopteris sens.lat. (especially in view of 



the findings for Gymnocarpium in Chapter 5), but ^^ 



might merely indicate that the relationship to ^ ^Jt 



the Male Fern itself is less close than between W'^ *#^ ^ 



that species and Polystichum, a conclusion which ^^ 



few systematists would deny. Of more impor- ^^L ^%^ % ^ 



tance than this is the strong confirmation which ^|^ 



this chromosome number provides of a lack of *^ 



close affinity with the next genus Asplenium. 



iU ^^ 



Before discussing this aspect, however, it will ^^l ^'wk!^ 



first be necessary to complete our study of the ^ • i^ ^ ^ 



genus Athyrium by consideration of two other C^ J*^ 

 species which are generally, though not always, 



included in it. ^^ 



The other two species oi Athyrium present in f 

 Britain are far less familiar than is the Lady 



Fern, since both are confined to the Scottish ^^ ^_ 



mountains and one is so very limited even in n=^ ^ 



Scotland that few living botanists have ever Athurium F/7/x fem'ina 



collected it, and there is therefore still doubt ^. ^ ^ , ,. t^- r, 



rig. 01. Explanatory diagram to rig. 02a. 



as to whether it is really a species or only a ^ ^ 



local mutant. Assuming for the moment that 



they are both species, the two in question are A. alpestre (Hoppe) Rylands and A. fiexile 



(Newman) Syme, both differing from the Lady Fern by the absence or early abortion of 





^ w 





Fig. 82. The British species of Athyrium. x 1000. a. Meiosis in a permanent acetocarmine mount of 

 A. Filix-femina (L.) Roth. ^ = 40. For explanatory diagram see Fig. 81. b. Two focal levels of 

 a root section showing a somatic chromosome count, in A. alpestre (Hoppe) Rylands. 2« = 8o. 

 For explanatory diagram see Fig. 84. c. Fresh acetocarmine preparation of A. flexile (Newman) 

 Syme. ^ = 40. For explanatory diagram see Fig. 88. 



94 



