THE OTHER BRITISH FERNS— POLTSTICHUM, ATHTRIUM, CETERACH 



identity of chromosome numbers, as is the vaHdity of the specific distinctness of Poly- 

 stichum aculeatum from P. angulare. 



The second genus thought to be closely related to the Male Fern by Bower is Athyrium, 

 the Lady Fern. A. Filix-femina (L.) Roth, the Lady Fern itself, needs little if any intro- 

 duction. As its name implies it resembles the Male Fern in a number of ways, notably 

 in size and in general habit, but the more delicately cut up pinnules as well as the 

 elongated indusium will at once distinguish it. It is hardy and abundant throughout 

 the British Isles and has probably provided more of the monstrous and peculiar forms 

 beloved of collectors than has any other British species. For this reason it is a common- 

 place of gardens, though often it must be admitted in a bizarre condition which bears 

 little resemblance to the normal wild species, which is on the whole surprisingly con- 



/? dcu/<Z3/-um n = 82 

 Fig. 80. Explanatory diagram to Fig. I^h. x 1500. 



stant in appearance. A characteristic difference from the Male Fern is the very tender 

 foliage which dies down sooner in autumn than is usual in any of our other large hardy 

 ferns. 



One of the more important taxonomic characters for the classification of the Lady 

 Fern is the shape of the indusium which resembles so much that of the Spleenworts 

 [Asplenium) that the Lady Fern was for long included in that genus. This has, however, 

 often aroused protests in the handbooks for fern collectors, e.g. Newman. The justice 

 of these views has at last been recognized by the separation of Athyrium as a genus 

 distinct from Asplenium and with a closer connexion with Dryopteris (sens.lat.). 



The cytology of the Lady Fern has been examined in specimens from Scotland, the 

 Lake District and Yorkshire. At first the resemblance to some of the diploid species 

 previously studied is so close that identity could readily be assumed. Such an assump- 

 tion would, however, probably not be correct. After repeated study from which a 

 decision has been difficuh, my personal interpretation of Athyrium Filix-femina is that 

 the haploid chromosome number (see Figs. 81 and 82) is not 41 but 40. This, if 



93 



