THE OTHER BRITISH FERNS 



for specimens from both Scotland and England. Scolopendrium vulgar e^ on the other hand 

 (Figs. 123^, 124), has n = 36. This result has been obtained for plants from both the 

 south and the north of England and in some horticultural strains (cf. Chapter 11); 

 there seems, therefore, to be no doubt as to its accuracy. 



In so far as generic chromosome numbers based on single species mean anything, 

 these numbers, while supporting the general resemblance of both genera to Asplenium 

 (for which n = 36), also give some slight emphasis against Bower's interpretation of the 

 form of the relationship and in favour of the older view that Scolopendrium is closer to 

 Asplenium than is Blechnum. This view, it may be said in passing, is also that adopted by 

 Holttum (1947). 



Some additional information * about the genus Scolopendrium will be found in Chapters 

 8 and 1 1 , 



#V » 



Scolopendrium n-36 Adiantum n^SO 



Fig. 124. Explanatory diagram Fig. 125. Explanatoiy diagram 



to Fig. i23e. X 1500. to Fig. 1236. x 1500. 



All the remaining genera of British ferns are, like the last two, either monotypic in 

 this country or at least appear to be so at first sight. With one exception (see next 

 chapter) they need not detain us long. 



Of the Pteroid affinity (see diagram, p. 89) we have only the Common Bracken, 

 Pteridium aquilinum (L.) Kuhn. This species is one of the most widespread plants known 



* The establishment of « = 36 for Scolopendrium vulgare is also of interest in another connexion. This 

 species is one of the relatively few ferns for which a considerable body of genetical information exists. 

 It was the first member of the group for which simple Mendelian inheritance was demonstrated (Lang, 

 1923) and has since been the object of closer study by Andersson-Kotto. Of special interest in the latter 

 work was the strain known as 'peculiar' for which the peculiar characteristic was the tendency of the 

 edges of all the leaves to become prothalloid without special treatment to bring this about. As in other 

 cases of apospory (cf. Osmunda) such prothalli could become free living if laid on soil and could produce 

 new sporophytes from apparently normal sex organs. A sequence of such plants should give rise to a 

 polyploid series, as in Osmunda. In Scolopendrium, however, an anomalous relation of chromosome 

 numbers was described (Andersson-Kotto and Gairdner, 1938), but it is now evident that their analysis 

 of 'peculiar' Scolopendrium is somewhat vitiated by the fact that their initial estimate of the chromosome 

 number for the parent species was seriously in error. These authors had assumed that their material 

 must have started with « = 30 and 2« = 60. With the present demonstration that the correct numbers are 

 n = 36 and 2n — 72 it is clear that the cytology of 'peculiar ' Scolopendrium needs to be reinvestigated before 

 any interpretation is possible. 



124 



