900 I. FILICES. 



PRINCIPAL GENERA. 

 Acrostichura. Olfersia. Platycerium. Ilemioiiitia. Niphobolus. 



TRIBE II. CYATHEACEJE. 



Elastic ring usually oblique, and completely surrounding the sporangium ; 

 sporangium often compressed, sessile, or shortly pedicelled, not continuous with 



the ring. 



PRINCIPAL GENERA. 



Ilemitelia. Matonia. Alsophila. Cyathea. 



TRIBE III. HYMENOFHYLLEjE. 



Elastic ring nearly as in Cyatheacece, but the sporangia are nearly globose, and 

 the elastic ring is situated on a plane nearly perpendicular to the point of attach- 

 ment of the sporangium. 



PRINCIPAL GENERA. 



Ilymenophyllum. Trichomanes. Loxsomn. 



TRIBE IV. CERATOPTERIDEJE. 



Elastic ring large, formed of vertical cells, not completely surrounding the 



sporangium, which is sessile. 



GENERA. 



Ceratopteris. Parkeria. 



TRIBE V. GLEICHENIE&. 



Sporangia solitary or grouped in definite numbers (2-3), sessile, globose ; 

 elastic ring perfect, but not corresponding to the point of attachment of the 



sporangium. 



PRINCIPAL GENERA. 



Gleichenia. Mertensia. Platysoma. 



TRIBE VI. LYGODIE&. 



Sporangia sessile, ovoid or turbinate ; elastic ring replaced by a sort of cap 

 with radiating striae, occupying the end of the sporangium, opposite to the point of 



attachment. 



PRINCIPAL GENERA. 



Aneimia. Scbizaea. Lygodium. Mohria. 



