THE OTHER BRITISH FERNS 



no, in which the chromosomes at metaphase are present in layers. Only by the 

 squash method, details of which are explained in Appendix i, can success be 

 achieved, and although this has been used with effect in the work described 

 in several previous chapters the precise details of its application to the higher ferns 

 were in the first instance devised to meet a complete technical deadlock which had 

 descended on the genus with which we are now concerned. The introduction of the 

 squash method resolved the technical impasse at once, but thereby revealed a cyto- 



Fig. 112. Meiosis in 'Cj'j/o/^/fm aZ/ima' from the leaf of Fig. 1 1 1 i. Fresh acetocarmine. x looo. n= 126. 



For explanatory diagram see Fig. 113. 



genetic problem of quite unusual complexity, a circumstance which was nevertheless to 

 be expected in view of the well-known taxonomic confusion prevailing in the genus. 



The first squash preparation to give a satisfactory result was that of Figs. 112 and 113. 

 The leaf from which it was obtained is shown in Fig. \i\h, and its very finely cut pinna- 

 tion characteristic of 'C. alpina'' is clearly seen. This specimen, which was kindly given 

 to me by Dr Rowlands of Doncaster, was described by him as 'the most authentic form 

 of C alpina (C. regia) to be found in Switzerland', since it retains fully its distinctive 

 characters in cultivation.* This is by no means always the case with alpina-like forms 



*The origin of this particular material is discussed in several letters included in volume vi of the 

 British Fern Gazette (1931). The finely cut specimen of C. regia collected by Waltham is said to have come 

 from 'limestone above Geneva at about 4600 ft.' in 1926 (loc. cit. 1931, p. 37). My plant agrees exactly 

 with that figured on pp. 72 and 85 of this volume of the Fern Gazette. 



1 14 



