ON THE CLASSIFICATION OF FERNS. 93 



VI. PTERIDEyE. 



Beai'ing on the margins of fronds, sori, which, are 

 covered with a special iudusium. 



PTERIS. Sori in a continuous line at the edge of the 

 frond. 



VII. ADIANTE^E. 



The margins of the fronds re/iexed, forming indusia, 

 which bear the sori beneath. 



9. ADIANTUM. Sori dorsal, in patches, covered with 

 a reftexed indusium. 



VIII. CYSTOPTERIDE^E. 



Sori with special ovate indusia attached behind, and 

 inflected hood-like over them. 



10. CYSTOPTERIS. Sori dorsal, with a cucullate or 

 hood-like indusium. 



IX. WOODSIE^. 



Sori having a roundish indusium springing from the 

 back of the veins. 



11. WOODSIA. Sori dorsal, with an indusium at- 

 tached beneath them. 



X. HYMENOPHYLLE^E. 



Sori produced at the end of the veins, and project- 

 ing from the margin, and surrounded by urn-shaped 

 and 2-valved membranes. 



12. TBICHOMANES. Sori marginal, covered by urn- 

 shaped expansions of the frond. 



13. HYMENOPHYLLUM. Sori marginal, surrounded 

 by 2-valved expansions of the frond. 



