218 BRITISH FERNS 



gether with intermediate . types, which have raised in some 

 minds a little doubt as to their absolute distinctness. P. 

 aculeatum, however, frequents mountain glens to a great elevation, 

 so that the possibility of wind-borne spores must be admitted. 

 The Holly Fern, too, is open to variation, and, obviously, if it 

 " sported," as both its relatives do, in the direction of increased 

 subdivision, its main difference from P. aculeatum would disappear. 

 A bipinnate " sport " of P. lonchitis would infallibly be ranked as 

 P. aculeatum unless its pedigree could be certainly determined. 

 The writer, indeed, found on Ben Lawers, near the top, amongst a 

 numerous group of the Holly Fern, an apparent plant of P. aculea- 

 tum, which, however, failed to survive removal, though that species 

 is usually very easy to re-establish. These points we merely 

 record for the guidance of future students, who may observe similar 

 cases and follow them up. P. lonchitis has not varied very much ; 

 we can only mention two instances. 



Cristatum. — This is a very good crested variety, found on Ben 

 Qui, in Scotland, by Dr. Craig, and we believe by others elsewhere. 



P. lonchitis imbricatum. 



Imbricatum (Fig. 254). — An imbricate, dense form recorded as 

 the Irish type of the species, but which we have found on Ben 

 Lawers, in Scotland ; Mr. Boyd has also found it in both countries. 



PSEUDATHYRIUM ALPESTRE (The Mountain I.ady 



Fern) 

 (Plate XXXIII) 



This Fern with numerous botanists ranks as a member of the 

 Polypodium family on account of its dot-like fructification and the 

 apparent absence of any cover. No one, however, who is acquainted 

 with the Fern in its growing state can accept this classification, 

 since it agrees in size, make, and general character so closely with 

 Athyrium filix-fcemina, the Lady Fern, as to compel the belief 

 that it is really a mountain form, if not of that identical species, 

 at any rate of the same genus. It is only found at high levels on 

 our Scottish mountains, above the levels at which the Lady Fern 



