55 HISTORY OF BRITISH FERNS. 



is lanceolate, more or less broad ; and they are supported 

 On stipes which are scaly at the base, and usually about a 

 third of the entire length of the fronds. The division of the 

 fronds is what is called bipinnate; the pinnae are always 

 lanceolate, more or less drawn out at the point, and they are 

 always again pinnate, though sometimes with the bases of 

 the pinnules connected by a narrow leafy wing, but not so 

 much so as to render them merely pinnatifid. The pinnules, 

 however, are more or less lobed or pinnatifid, the lobes being 

 sharply toothed in a varying manner. 



Prom the delicate herbaceous texture of the fronds the 

 venation is very distinct; and is seen to consist, in each 

 pinnule, of a wavy midvein, from which proceed alternate 

 venules, which again produce alternate veinlets, and on the 

 anterior side of this series of veins, at some distance from 

 the margin, is borne an oblong sorus ; in the larger and 

 more divided pinnules the veining is more compound, and 

 more than one sorus is produced from each primary venule, 

 which thus becomes a midvein, with branches on a smaller 

 scale. The sori are themselves oblong, a little curved, and 

 they are covered by indusia of the same form. Both the 

 sorus and the indusium, on the development of the spore- 

 cases, become bulged in the centre and contracted at the 



