30 



Genus 4. POLYSTICHUM. 



GEN. CHAR. Sori circular, seated upon the upper branch of the 

 lateral veins -, covered by a circular peltate indusium attached 

 by its centre. 



This genus, separated from Lastrea in consequence of the dif- 

 ference of the form and attachment of the indusium, is farther 

 characterized by the rigidity of its foliage, and of the sharp spinous 

 processes by which all the ultimate divisions of the frond are ter- 

 minated, while the upper basal lobe or pinnule is always larger 

 than the others. The British species are very nearly allied, and 

 present a series of varieties between the simpler and more compli- 

 cated forms that renders their determination difficult. The name, 

 not well chosen, is compounded from the Greek TroXu?, many, and 

 ?, series, in allusion to the regular linear arrangement of the 



son. 



POLYSTICHUM LOXCHITIS. Holly Fern. Rough Alpine Shield- 

 Fern. TAB. XV. 



Fronds rigid, linear-lanceolate, pinnate : pinna5 spinose-serrate, 

 auricled at the base above, oblique below. 



Polystichum Lonchitis, Roth. Babington. Moore. Newman. 

 Aspidium Lonchitis, Swartz. Smith. Hooker and Arnott. 

 E. B. Polypodium, Linnaeus. 



Its exclusively alpine habitats have caused this beautiful fern to 

 be generally described as among our botanical rarities : in England 

 and Wales it seems to be confined to the mountains of Yorkshire 

 and the Snowdon district ; but, in the mountainous parts of Scot- 

 land, it is widely and abundantly distributed, and in the north 

 and west of Ireland. It is generally found springing from the 

 clefts of the rocks in the highest and most exposed situations ; but 

 occasionally lower down, in the glens and mountain-passes, espe- 

 cially in the crevices and on the ledges of their most precipitous 

 sides. The fronds grow in a tuft from the extremity of a very 

 slowly lengthening rhizoma, varying from a few inches to a foot 

 and a half in height : they are generally of a rigid texture and 

 erect growth, but in some situations thinner and spreading, or 

 even almost pendulous ; the latter character, it has been remarked, 

 belongs almost exclusively to English and Welsh specimens. The 

 colour is of a deep glossy green. The general outline of the 

 frond is linear, more or less acuminated at the upper part, and 

 simply pinnate. The pinna? are short, arranged alternately and 



