THE GENUS DRTOPTERIS IN BRITAIN 



collectors of the last century, owing to which fortunate circumstance it is still possible 

 to obtain portions of it in the living state in old collections, and I was most fortunate in 

 being given access to a very large and ancient specimen of authentic Windermere 

 origin in the garden of the late Dr F. W. Stansfield of Reading. In Babington's Manual 

 (1922) 'L. remota Moore' is listed as a species, with the 

 possibility that it might be a hybrid indicated only in 

 brackets. The complete sterility of the plant when spores 

 are sown, however, has always been known to British 

 pteridologists, who have been unanimous in their opinion 

 that it is a hybrid, though the attribution of parentage 

 has varied somewhat. D. Filix-mas, D. spinulosa, D. dilatata 

 and D. rigida have all been named from time to time in 

 this connexion, though the general consensus of opinion 

 has been in favour of the combination D. Filix-mas x D. 

 spinulosa. Some of the reasons for this diagnosis may per- 

 haps be judged by examination of the pinna shown in 



Fig. 58. 



Cytological examination of the Windermere plant 

 has strongly confirmed the diagnosis of hybridity with- 

 out thereby throwing any further light on the nature of 

 the parental species, a fact which need cause no surprise, 

 since all those listed have identical chromosome numbers 

 and could therefore not be distinguished cytologically. 

 As expected, the chromosome number found in the 

 roots of the Windermere plant is of the order of 160 

 (Fig. 59^) (that of both putative parents being of the 

 same order, i.e. 2/2=164). Meiosis in the Windermere 

 plant is extremely irregular (Fig. 59 a), a circumstance 

 which fully explains the sterility of the spores. 



Since a single plant incapable of reproduction and 

 demonstrably a hybrid cannot possibly be accepted as a 

 species on any definition of that word, these findings at 



once indicate that ' Lastrea remota Moore' is not the same thing as the continental 

 material to which the specific epithet remotum was first applied. This* was a plant first 

 found by A. Braun near Geroldsau in Baden and described by him in 1 843 as Aspidium 

 rigidum j3 remotum, though subsequently raised to the rank of a species in 1850 under the 

 name of ^. remotum A. Braun. This 'species' is fertile from spores but apogamous, and 

 when investigated by Dopp in 1932 a chromosome number was found which approxi- 

 mates to the triploid condition in this circle of affinity (Dopp's actual number was 

 reported as c. 130; the triploid condition itself is now known to be 123). Morpho- 

 logically A. remotum A. Braun resembles the Windermere plant in that it looks like a 

 hybrid between the same two parent species, namely, Dryopteris Filix-mas and D. spinu- 

 losa, though its triploid nature makes its exact derivation more problematical, since 



* Cf. Praeger (igog). 



Fig. 58. Lowest pinna from a 

 large frond of an offset from the 

 original 'Lastrea remota Moore' 

 from Windermere. Natural size. 



72 



