POLYPODIUM VULGARE 



with the words 'Polypodium latine, grece Dipteris . . .'. It is perhaps for this reason 

 that the popular name of 'Polypody' is still based on the Latin rather than on a folk 

 name in the vernacular as in other ferns, but it is probably only a coincidence that it is 

 still bracketed with Dipteris in the phyletic view of Bower (cf p. 89) as a somewhat 

 doubtful member of the 'Dipteroid' affinity, since Dipteris at present denotes a very 

 restricted genus confined to the Malay Peninsula and almost certainly unknown to the 



herbalists. 



The European Polypodium vulgare L., although the type species of the type genus of the 

 family Polypodiaceae to which all the ferns hitherto discussed except Osmunda have 

 until recently been held to belong, has no well-authenticated near relatives. The genus 

 is, in Bower's words, a comprehensive but phyletically confused one in which, owing to 

 the loss of the morphological characters of the indusium, derivatives of widely different 

 origin have been grouped together. Some of these have already been separated out and 

 discussed in the context of their nearest indusiate relatives {Phegopteris, Gymnocarpium, 

 Chapter 5; Athyrium alpestre and flexile, Chapter 6), but even without these we are left 

 with a large and almost exclusively tropical genus in which it is by no means clear where 

 exactly the one temperate species should be placed. Doubts about this have been 

 repeatedly expressed, and it is only by invoking a resemblance to the tropical Gonio- 

 phlebium that Bower has classified Polypodium vulgare at all. On the other hand, the idea 

 that there could be doubts about the specific integrity* of P. vulgare is one which only 

 a few specialists and no European writers of Floras appear ever to have entertained, 

 and therefore the surprise with which the unequivocal fact was revealed by the cytology 

 was very considerable. 



'P. vulgare' is in fact a comprehensive name for a group of well-defined if closely 

 related species possessing an aggregate range which extends right round the northern 

 hemisphere together with South Africa, Kerguelen Island and perhaps Hawaii, to the 

 first two of which it could, however, have been introduced from Europe. Each species 

 within this range has a characteristic ecological or geographical area which only in 

 certain cases overlaps that of others. Moreover, the cytological differences are such as 

 to indicate quite clearly that populations of different ages are represented. 



As was announced in a preliminary communication (Manton, 1947) there are three 

 distinct cytological types in Britain and the nearer parts of the continent of Europe. 

 The gametic chromosome numbers are 37, 74 and 1 1 1, which correspond therefore to 

 sporophytes of diploid, tetraploid and hexaploid constitution in a polyploid series on 

 37. The monoploid number itself has already been illustrated for a horticuhural variety 

 oi Polypodium known as P. vulgare var. semilacerum Hort. in Fig. 123a, p. 123, and it will 

 be seen again in Fig. 143 on p. 141. The gametic number of the tetraploid {n = 74) 

 may be seen in a specimen from Norway in Fig. 136, and that of the hexaploid (n= 1 1 1) 

 in Figs. 1 27-1 29. The first of the hexaploid figures is that reproduced in the prehminary 

 note in which an approximate count of c. 112 had been recorded earlier. That the 

 gametic number is 1 1 1 without any equivocation is, however, clear, among other thmgs, 

 from Fig. 128, in which the whole array of chromosomes is dispersed with such spec- 

 * Compare, for example, the views of Christensen (1928), which summarized excellently the prevailing 

 opinion with which this work began. 



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