148 HISTORY OF BRITISH FERNS. 



drawn out at the point, the lower pair always lonp;er than 

 the next above them. The pinnules, especially those on 

 the larger pinnae, are again pinnate ; the alternate pinnules 

 being deeply lobed, and the margins sharply serrate. 



The fronds are of a thick leathery texture, with nume- 

 rous veins. To each pinnule there is a distinct midvein 

 midrib or costa, bearing simple or branched veins, on 

 which the sori are produced. All the ultimate divisions 

 of the fronds, as well as all the larger lobes, have midveins 

 producing these simple or branched veins, and these bear 

 the sori near their junction with the midvein, so that the 

 sori are placed near the centre of every pinnule or lobe. 

 At first the sori are distinct, and have the elono-ate narrow 

 form common to this genus ; but as they become older, 

 they often spread and become confl.uent, so that almost 

 the entire under-surface of the frond is covered with the 

 spore-cases. The indusium is narrow, with its free margin 

 entire : this soon becomes pushed away by the growing 

 sori, and is lost. 



This species is very variable. In dry and exposed places 

 it is small, and obtuse in its parts, whilst in sheltered, 

 shady places it is much drawn out or elongated. Tlie 

 extreme states have been considered as varieties ; that in 



