90 HISTORY or BRITISH FERNS. 



auricle, while the lower side of the base is, as it were, cut 

 away. The margin is set with spinous teeth. The veins 

 are twice branched, the branches extendino; to the marf>in 

 without joining with others. The clusters of spore-cases 

 form a line parallel with, and on each side of the midrib, 

 and are covered each by a membranous circular scale, 

 which is attached by a short central stalk. 



This is a true Rock Fern, occurring on the bleak moun- 

 tains of Scotland and in the milder climate of Ireland, as 

 well as, rarely, in the north of England and Wales. It is 

 very distinct, and, when vigorous and healthy, not inele- 

 gant, but is exceedingly difficult of cultivation, and is 

 seldom seen thriving under artificial treatment. 



The Holly Fern has been at different times called Aspi- 

 dium Lonchitis and Pohipodium LoncJdtis. 



Polystichum acnleatum, Roth. 



The Common Prickly Shield Fern. 



This species is almost evergreen in a sheltered situation, 

 and is one of those which are well suited by boldness of 

 character for the decoration of rocky scenery. It is a stout 

 plant, having the fronds a couple of feet or more long, and 

 springing from a stout tufted stem or crown, whence they 



