202 HISTORY OF BRITISH FERNS. 



side, bluntish at the apex, and finely saw-edged along the 

 margin. Some fronds are entirely barren, and these differ 

 from the fertile ones only in having the leafy pinnules 

 continued all the way to the apex, instead of having the 

 apex contracted, and bearing the spore-cases. It is not 

 always, however, that the spore-cases when present are 

 produced at the apex of the frond ; abnormal developments 

 are not uncommon, and in these cases any portion of the 

 pinnules may be seen converted into spore-cases — some- 

 times a few pinnae at the middle of the frond, while the 

 apex is leafy ; sometimes the base of a pinna, while its 

 apex retains the leafy form ; sometimes the base of a 

 pinnule here and there, just its apex too, being broad and 

 leafy ; but the usual condition is to find a few of the 

 shortened pinnae, which form the apex of the frond, con- 

 tracted and soriferous throughout. 



The venation, as seen in the barren fronds, consists of 

 a prominent midvein, bearing once- or twice-forked veins 

 proceeding to the margin in direct lines. In the fertile 

 parts of the frond, only the midrib of the pinnules is fully 

 developed, and the spore-cases are attached to a small 

 portion of the veins which becomes developed just to 

 serve as a receptacle. The spore-cases are subglobose, 



