14 



Woods, a British botanist. Chiefly remarkable on account of the 

 singular character of the so-called involucre, which is however only 

 a modification of an indusium, opening in the centre, and splitting 

 more or less regularly into the conferva-like filaments accompanying 

 the magnified sorus in our figure of W. Ilvensis. Its true nature 

 is very obvious on examination of the immature sori. The two 

 British species are among the rarest of our indigenous plants: 

 notwithstanding a considerable difference in habit, and in the 

 divisions of the frond, many modem botanists regard them only as 

 varieties. 



WOODSIA ILVENSIS. Oblong Woodsia. TAB. V. 



Fronds lanceolate, pinnate; pinnse oblong, deeply pinnatifid, 

 chaffy beneath. Rachis chaffy. 



Woodsia Ilvensis, R. Brown. Acrostichum Ilvense, Linnaus. 

 Polypodium arvonicum, Withering. Polypodium Ilvense, 

 Swartz. 



Only found growing in the crevices of moist rocks about the 

 summits of our higher mountains, and so sparingly distributed in 

 these localities as to be regarded exceedingly rare. The recorded 

 habitats are few, viz. Falcon Glints, Teesdale, Durham; Clogwynn-y- 

 Garnedd, Snowdon, and Llynn-y-cwn, on Glyder Vawr, Wales ; and 

 the Clova mountains, Scotland. A careful explorer of the bleak 

 regions over which many other rarities of our alpine flora are 

 distributed, would however probably find reason to conclude that 

 its extension is far less limited. This remark is not one at ran- 

 dom ; but the wanton appropriation, or it might rather be styled 

 depredation, exercised by certain wholesale collectors, not of spe- 

 cimens only, but of entire plants, has rendered the true botanist, 

 in cases like the present, averse to the promulgation of his dis- 

 coveries. 



The fronds grow in a tuft at the extremity of a very short 

 rhizoma, seldom exceed two or three inches in height, and in 

 very dry or exposed situations are sometimes not above one inch. 

 In general outline they are lanceolate and pinnate, with mostly 

 opposite, oblong, deeply-lobed pinna?. The under surface is more 

 or less covered with glossy, jointed hairs, accompanied, especially 

 about the mid-veins, by long, attenuated scales, which, with the 

 capillary segments of the indusium, often nearly conceal the sori. 

 The sori are produced at or near the extremities of the lateral 

 veins of the lobes, a crenation of the margin of the latter generally 

 attending their development. They attain maturity in August 

 and September. 



