2 ATHYRIUM. 



Twenty-nine species belong to Athyrium, which are distin- 

 guished by short sori, and lax, convex, or arcuate involucres, 

 and with pinnato-pinnatifid or bi-tripinnate fronds. Amongst 

 these are Asplenium filix-fwmina of Great Britain, A. crenatum 

 of ISTorway, and A. tlielypter aides of North America. 



Fifty-one species belong to Eadiplazium, having double 

 involucres; none of which are European. Seven species belong 

 to Amsogotiium, having anastomosing veins; none of which are 

 European. Four species belong to Hemidictyum, having sori 

 very long, naked, asplenoid, with veins anastomosing towards 

 the margin. In this group Sir W. Hooker places Asplenium 

 ceterach of England, (the Ceterach ojficinaruni of Willdenow, 

 or Grammitis ceterach of Swartz.) 



Although I quite agree with Sir W. Hooker in the dubious 

 distinctness of the genus Athyrium from Asplenitan, still as 

 Mr. Moore retains the genus we shall keep the Lady Fern 

 distinct from the other Asjileniums. 



Athyrium has short, oblong-lunate, curved, or horse-shoe- 

 shaped indusiate sori; veins simple or forked from a central 

 costa: venules free. Caudex brief, erect, or creeping. Fronds 

 herbaceous, bi-tripinnate. 



Only one species inhabits Great Britain. 



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