BRITISH FERNS. 29 



WOODSIA. 



WOODSIA ILVENSIS and "W. HYPERBOREA. Brown, Smith, 



Sprengel, Hooker, Sadler, Francis. 

 Acrostichum Ilvense. Linneus, Berkenhout, Hudson. 

 Acrostichum alpinum and Ilvense. Bolton. 

 Polypodium Ilvense, hyperboreum. Swartz. 

 Polypodium Arwnicum. Withering. 

 Polypodium fontanum, of the Linnean Herbarium, is identical 



with Woodsia hyperborea, Brown. 



LOCALITIES. 



ENGLAND. . Unknown. 



WALES. . . . Caernarvonshire, Llyn-y-coon; on Glyder Vawr"andClogwyn-y-Garnedd; on Snowdon. 



SCOTLAND. . Perthshire, Ben Lawers ; Forfarshire, Clova Mountains. 



IRELAND. . Unknown. 



THE genus Woodsia was established by Mr. Brown, in the 

 Transactions of the Linnean Society of London, vol. xi. p. 170, 

 and has been adopted by Smith, Hooker, Sprengel, and Sadler. 

 The genus is founded on certain membranous scales attached 

 below the thecae, which Mr. Brown considers as analogous to the 

 indusium of indusiate ferns. This membrane is somewhat cup- 

 shaped, and its margin is divided into capillary segments, which 

 appear scattered among the mass of thecse, or sometimes 

 incurved over them. Presl has returned the species of Woodsia 

 to the genus Polypodium. I must confess my opinion that bota- 

 nists generally will be unable to detect any analogy between the 

 bristle-like appendages among the thecae of Woodsia and the 

 indusium so obvious in Asplenium and Polystichum, and will 

 consider these bristles as identical with those which are scattered 

 over the entire under surface of the frond. Nevertheless it 

 seems so desirable to break into minor sections the hetero- 

 geneous mass of Polypodia, as they now stand, that it is with 

 pleasure I avail myself of Mr. Brown's labours in the present 

 instance. 



There are said to be two species of the genus in this country : 

 W. Ilvensis, represented by the upper plant in the figure, and 

 W. hyperborea by the lower. The. middle plant of the three is 

 from a rock above Llyn-y-coon, on the Dog's Lake, a small pool 



