36 PERNS OP GREAT BRITAIN. 



quarters of an inch from the point at which it joins the 

 rhizome — a character belonging to all the species of 

 Woodsia. The rhizome is tufted, and the roots black 

 and wiry. 



This fern is of a dull green colour, and dies down to 

 the ground at the approach of winter. The frond is 

 lanceolate in form, and pinnate. The pinnae, which are 

 usually in pairs, are oblong, with obtuse ends, and a 

 deeply-lobed margin, sometimes cut down almost to the 

 mid- vein. The mid-vein of the segments of the pinnae is 

 not very distinct ; and the lateral veins, which are either 

 simple or branched, issue from it towards the margin, 

 near to which the clusters of seed-cases are seated. This 

 fern is often not more than an inch high, and very rarely 

 more than three inches. It has been termed Achrosti- 

 cum ilvense, and is now by some writers called Polypo- 

 dium ilvense, or Polypodium arvonicum. 



3. W. alpina (Round-leaved or Alpine Woodsia). — 

 Fronds pinnate; the pinnm pinnatifid, hairy beneath; 

 clusters of spore-cases solitary at first, afterwards min- 

 gling in one mass. This little fern grows in tufts ; its 

 fronds never more than two or three inches in height, 

 and more commonly about an inch high. It is a very 

 rare species, found in fissures of Alpine rocks, mostly 

 in places rarely visited. It has been seen on Snowdon 

 and Ben Lawers, and also in the Glen of the Dole, 

 Clova, and other places of the eastern Highlands. Its 

 stalk is very slender and smooth, only that a few small 

 scattered hairs and scales may be seen upon it at an 

 early period of its growth. The frond is long, narrow, 

 almost linear, and pinnate. The pinn^ are perfectly 



