THE OTHER BRITISH FERKS—POLTSTICHUM, ATHYRIUM, CETERACH 



the indusium and therefore, as in the comparable case of Gymnocarpium and Phegopteris 

 (Chapter 5), formerly classed as Polypodium. 



Athyrium alpestre (Fig. 83) is superficially very similar to the Lady Fern proper when 

 well developed, though it is generally somewhat smaller and in cultivation matures its 

 fronds much earher. In Scotland it occurs at an altitude shared by the Holly Fern, 

 and like that species it is less restricted in range on the Continent than with us, being 

 locally abundant, at suitable altitudes, in most of the mountain ranges of Europe and 



Fig. 83. Pinnae of Athyrium alpestre (Hoppe) Rylands, from two different plants to show range of 

 morphology in this species on Ben Alder, locality o^ A. flexile. The left-hand plant is probably the 

 variety obtusatum Syme. Natural size. 



in parts of America. Cytologically it appears to resemble the Lady Fern, although my 

 study of it is imperfect. I have had several Scottish plants in cultivation for many years, 

 but they are fertile so infrequently that I have not yet seen 

 meiosis. From a root-tip count represented by Figs. 82^ and 

 84 the somatic number, however, appears to be 2n = 80. 



The third species o{ Athyrium, A. flexile (Newm.) Syme, is a 

 very remarkable and interesting little plant which would well 

 repay genetical investigation. Its claim to specific rather 

 than to varietal status can only finally be settled after 

 breeding experiments with its nearest relatives have been 

 carried out, but on morphology alone it would probably 

 long ago have been accepted as a species but for the circum- 

 stance that the only known locality in which it now occurs in 

 any quantity is so remote and difficult of access that very few 

 botanists have ever visited it. The locality in question is the 

 great corrie on the north face of Ben Alder in west Inverness- 

 shire, where it was said to be abundant by Professor 

 J. H. Balfour in 1867 and where in 1946 it was still plentiful. 

 The only other station in which it has ever been recorded 

 in quantity is Glen Prosen, Forfarshire, where the t>'pe 

 specimens (cf. Fig. 85) were first found by Backhouse in 



1853. A. flexile may still exist in Glen Prosen, but it has not recently been seen there. 

 The following notes have, however, been supplied from Ben Alder by my colleague, 

 Dr Sledge, who in August 1946 camped at the foot of the mountain (which is 12 miles 

 away from the nearest house) in order to search for the plant and who succeeded in 

 bringing back a number of living specimens (cf. Fig. 86) in excellent condition which 

 have since been maintained in cultivation. 



95 



• • • • 



•• :'• 



2/1' 80 

 /I. a/pestre 



Fig. 84. Explanatory 

 . diagram to Fig. 82 h. 

 X 2000. 



