THE OTHER BRITISH FERNS 



to science, for, without being a weed of cultivation, it is nevertheless to be found in 

 every continent in the world. I am fortunate in having been able to compare a tropical 

 and a temperate individual, fixed material of a specimen from Malay having been sent 

 to me in 1938 by my friend Dr Chapman. The Malay material proved indistinguishable 

 at meiosis from a British plant from Lancashire, both having n = 52 (Fig. 12'^d). 



Of the Gymnogrammoid affinity we have the Parsley Fern Cryptogramma crispa (L.) 

 R.Br. { = Allosorus crispus (L.) Bernh.), and the Maiden Hair, Adiantum capillus-veneris L. 

 The little annual Anogramme leptophylla (L.) Link, though present on the island of Jersey, 

 may perhaps be omitted from the present survey since it does not touch the mainland 

 of Great Britain. Owing to the war it has in any case been impossible to obtain it. 



Taking the Maiden Hair [Adiantum) first, this is a rare British plant though exceed- 

 ingly common in many of the warmer parts of Europe. I have examined it cytologically 

 in wild specimens from Italy and from Spain and in one British example brought back 

 from the limestone pavement of Galway Bay in Ireland. All three specimens gave 

 approximate root-tip counts of 2n = c. 60, and they seemed indistinguishable. The 

 Irish specimen unfortunately perished in an air raid before meiosis had been examined. 

 Both the continental specimens, however, give n = 30 without any ambiguity (Figs. 

 123^, 125). This may therefore be accepted for the British plant also. 



The Parsley Fern Cryptogramma (or Allosorus) is exceedingly abundant as a scree 

 plant on siliceous rocks in many of our mountain regions, such as the Lake District and 

 Wales. I have investigated it from the Lake District and, as shown in Fig. 123c, 

 n = 60. The resemblance between this and the preceding is clearly of the sort which 

 may be expected to be of use for taxonomic purposes when a greater number of species 

 of the Gymnogrammoid affinity have been studied. 



Reviewing this chapter we may note the rather wide range of different chromosome 

 numbers to be met with in Britain as soon as we leave the relative uniformity of the 

 Dryopteroid affinity behind. This may perhaps suggest that in the Pteridophyta as in 

 the Cruciferae the aneuploid numerical changes, though rare, are actually concerned 

 with the formation of larger evolutionary units than those which result with almost 

 monotonous frequency from polyploidy. This conclusion is of some importance and 

 should if possible be pursued outside the rather narrow confines of the European flora. 



125 



