CHAPTER 7 



THE OTHER BRITISH FERNS (CONTINUED) 



Two genera which should perhaps be considered with the Dryopteroids are Woodsia 



and Cystopteris, but both are somewhat more doubtful in position than those dealt with 



in the previous chapter, and for this reason discussion of them was deferred. As will be 



seen by reference back to the diagram on p. 89, the phyletic affinities of both are 



marked as questionable by Bower. With regard 



to Woodsia the general consensus of opinion seems 



to be that it is probably a primitive genus related 



to Dryopteris, either directly by way of certain tree 



ferns known as the Cyatheaceae (Bower's view) 



or indirectly (view of Christensen, Copeland, 



etc.). Cystopteris, according to Bower, is frankly 



'incertae sedis', but other authors (e.g. Newman, 



1 854) place it with confidence near Woodsia. 



Taking Woodsia first, this is represented in 

 Europe by three species, only two of which are 

 British. W. ilvensis (L.) R.Br, and W. alpina (Bol- 

 ton) S. F. Gray [W. hyperborea R.Br.) are among 

 our rarest ferns, being confined to a few localities 

 in the mountains of Scotland and Wales, in most 

 of which their numbers, unhappily, appear to be 

 diminishing. W. ilvensis, originally the commoner 

 and somewhat the larger of the two, is now quite 

 extinct in many of its classic haunts, though 

 fortunately it still lingers on a few unfrequented 

 and inaccessible crags. For precise instructions 

 as to how to reach one of these I am greatly 

 indebted to my friend, Dr H. F. Dovaston. Thanks to this, and with the help of Professor 

 D. Thoday of Bangor, I was able in July 1945 to collect a living fertile frond from an 

 authentic wild Welsh plant and to bring one small offset, from a group proliferating 

 from the base of a dead stock, into cultivation. Both the frond and the offset yielded 

 cytological information. For the other species I am indebted to Mr G. Roger of Manchester 

 Museum and to Dr B. T. Cromwell of Hull, each of whom has lent me one living plant 

 collected wild in Scotland. Silhouettes of fronds of the plants examined are given in 

 Fig. 107a and b. 



The chromosomes of the two species are shown in Fig. 108 a and b (explanatory dia- 

 grams in Fig. 109 a and b). It is obvious at a glance that they are not identical and that 

 one species {W. alpina. Fig. 108^) has about twice as many chromosomes as the other 

 {W. ilvensis, Fig. io8fl). As nearly as can be determined the exact numbers are n = 41 



Fig. 107. British H'ooi^^fa from living leaves 

 grown in cultivation. Natural size. a. 

 W. ilvensis (L.) R.Br, from Wales, b. W. 

 alpina (Bolton) S. F. Gray from Scotland. 



I 10 



