12 INDEX TO THE GENERA. 



Sori contained in little two-valved vessels, 

 springing from the pinna, and adjoining 

 the stem. 



HYMENOPHYLLUM. 



Sori contained in entire cups, springing from 

 the pinna, dispersed. 

 TRICHOMANES. 



Sori naked, on a fertile, compoundly-branched, 

 spike, surmounting a succession of barren, 

 leafy, pinnae. 



OSMUNDA. 



Sori naked, on a fertile, compoundly-branched, 

 spike, rising above a single, barren, leafy, 

 pinna. 



BOTRYCHIUM. 



Sori naked, on a fertile, simple, spike. 

 OPHIOGLOSSUM. 



