THE OTHER BRITISH FERNS 



from high akitudes which often tend to revert to the more usual form ofC.fragilis when 

 grown at sea-level. The chromosome number of this specimen is not in doubt. As 

 comparison between the photograph and the explanatory diagram should prove there 

 are exactly 126 pairs of chromosomes in this cell. 



A gametic chromosome number of 126 was subsequently found many times in plants 

 of very diverse origin and appearance. A small array of relevant leaves is contained in 



DICKIE'S FERN, {natural size). 



Fig. 1 16. Newman's original figure of Cjstopteris Dickieana Sim 

 (after Newman, 1854). Natural size. 



Fig. Ill, plants of both Swiss and British origin being represented, and two further 

 samples of cytological preparations together with one additional explanatory diagram 

 are placed later in the chapter in Figs. 120 a and b and 121b. In spite of the considerable 

 range of morphology there appears to be no detectable cytological difference between 

 ^C. fragilis' types and 'C. alpina' or alpina-\ike types. The reality or otherwise of 

 C. alpina as a justifiable species can therefore only be further investigated by genetical 

 means. 



An extended search through European populations of Cystopteris has, however, shown 

 that some genuine cytological diflferences do exist within the C.fragilis complex, some of 



116 



