FILICES. 49 



counties it has been reported from "Worcestershire, Carnarvon, and 

 Cumberland. It grows in the Isle of "Wight, at Swainston, and 

 Carisbrooke Castle, but not wild. It has been found in an old quarry 

 near Aberfeldy : concerning this station, Dr. Buchanan White says 

 it is now nearly eradicated, but was once abundant ; he adds that 

 he once suggested, half in jest, that the spores might have been 

 accidentally carried with workmen's tools from some limestone quarry 

 in England. Mr. "Watson also gives No. 93, i.e. North Aberdeen, 

 as a Scotch station, which is insufficiently vouched for, but possibly 

 correct. ('Top. Bot.,' p. 489.) It seems remarkable that it should 

 be absent from the limestone hills of Ireland. 



England, Scotland ? Perennial. Summer. 



Rootstock pitchy black, about the thickness of a straw or more. 

 Fronds several, -^ to f inch apart. Stipes 4 to 10 inches long. 

 Lamina 3^ to 9 inches long, by 3 to 8 inches broad. Lower pair of 

 pinna? much larger than the succeeding ones, and more remote from 

 them than any of the other pairs or than the portion of their 

 partial rachis which is between its junction with the main rachis and 

 its first pair of pinnae ; they are, however, not so much larger than 

 the other pairs of pinna? as to give the frond a ternate appearance, 

 and they are not rolled up into little balls separate from the one into 

 which the rest of the lamina is coiled in bud. The fronds appear 

 in May and perish with the first frost. I have not seen any fully 

 developed barren fronds of this species analogous to those mentioned 

 under P. Dryopteris. 



P. Pobertiana has been often confounded with P. Dryopteris, and 

 indeed even now some botanists regard them as varieties of a single 

 species. To me they appear abundantly distinct, and it is surprising 

 that any one who has seen the tw 7 o plants alive could combine them. 

 P. Robertiana differs from P. Dryopteris in having the caudex con- 

 siderably thicker, more woody, and more tortuous, the younger por- 

 tions more thickly clothed with scales and with brownish tomentum, 

 which comes off in flakes, leaving the old portions of the rootstock 

 glabrous ; the root-fibres are also stronger and more tomentose. The 

 fronds are more numerous, much closer together, and (when young) 

 with many more scales. The stipes is much thicker, and firmer, and 

 glandular, at least when young. The lamina is not suddenly bent 

 back at its junction with the stipes as in P. Dryopteris, but curves back- 

 wards gradually ; it is longer in proportion to its breadth, much more 

 acute, rather less compound, with the pinnules less approximate and 

 more of them separated ; it is of a dull greyish tint — very different 

 from the vivid green of P. Dryopteris. The very minute stalked- 

 glands with w T hich it is clothed, give it a somewhat dusty appearance, 

 and furnish a character by which it may be distinguished in the dried 



VOL. XII. H 



