CLASSIFICATION. 35 
I. (v.)-Pterldeae. 
Sori forming a continuous marginal 
line covered by the reflexed edge 
of the ultimate divisions of the 
frond altered in texture 13. Pteris. 
Sori transverse, growing on the re- 
flexed apices of the lobes of the frond, 
which are altered in texture 14. Adiantum. 
I (vl.) Hymenophylleae. 
Rec> ptacles exserted, surrounded at 
the base by urn-shaped involucres 
of the same texture as the frond ... 15. Trichomanes. 
Keceptacles included, surrounded by 
two-vaived involucres of the same [lum. 
texture as the frond 1(5. Hymenophyl- 
II. Osmundaceae. 
Fructification forming irregular, 
densely-branched panicles at the 
apex of the fronds 17. Ostnunda. 
III.- Ophioslossaccse. 
Fructification forming irregularly- 
branched panicles terminating a 
separate branch of frond 18. Botrychium. 
Fructification forming two-ranked 
simple spikes terminating a separate 
branch of frond 19. Ophiogiossum. 
