GENERAL DESCRIPTION 5 



down to the rib or midrib the pinnule (or small pinna), 

 the pinna, or the frond, is called pinnatifid. 



The TRUE FERNS are developed in a peculiar man- 

 ner, coming up in a crozier-like form, having the rachis 

 rolled in from the point to the base. In the more com- 

 pound ferns the frond-divisions are each again rolled in 

 after the same fashion. This is called being circinate. 

 All the British species are circinate (and therefore True 

 Ferns) except two the Adder's Tongue and the 

 Moonwort, in both of which the fronds are what is 

 called plicate, or folded straight, like the folding of a 

 lady's fan. 



The order in which the veins, or ribs, of the fronds 

 are disposed is called the venation ; and deserves atten- 

 tion as affording one of the means of distinguishing the 

 groups. It is from some determinate part of the veins 

 that the spore-cases proceed. This part is called the 

 receptacle. In some few native kinds the receptacle is 

 projected beyond the margin of the frond, and the 

 spore-cases are collected round its free extremity. 

 More commonly, however, the veins stop within the 

 margin, and the spore-cases grow in round or elongated 

 clusters, situated sometimes at their ends, sometimes 

 at their sides, and protruded through the skin of the 

 lower surface of the fronds. 



The seeds (it has already been said) are called spores, 

 tho seed-vessels spore-eases, the clusters of spore-cases 

 sori. These sori, generally placed on the back or mar- 

 gins of the fronds, are in the great majority of British 

 species surrounded or girt by an elastic ring or band, 

 sometimes vertical and burst by an irregular trans- 



