9-1. FILICES. 
407 
10. Cetekacii. Lateral veins anastomosing, sori attached 
to their middle t>n the side nci;t the midrib, except in the 
lowest. Indusium (?) a narrow nearly erect membrane on 
the back of the vein. Whole back of the frond covered 
with chaffy scales. 
Tr. IV. ADIANTARI^. Thecae covered by a marginal or 
submarginal elongated j)art of the frond, or by a separated 
portion of the cuticle resembling an indusium. 
11. IIlechnum. Thecae in a continuous line parallel to the 
michib upon a longitudinal anastomosing part of the trans- 
verse veins, and covered by a continuous scarious indusium . 
12. Pteris. Thecae in a continuous marginal line covered by 
a continuous indusium formed of the reflexed margin. 
13. Adiantum. Sori marginal, oblong or roundish, covered 
by distinct reflexed portions of the margin of the frond. 
Suborder II. HYMENOPHYLLACE^. 
Thecae opening irregularly ; ring oblique, excentric, transverse, 
complete; receptacle terminating a vein at the margin of the 
frond. 
Tr. V. HYMENOPHYLLEjE. 
14. Trichomanes. Thecae on an elongated filiform receptacle 
within a cupshaped involucre of the same texture with the 
frond. 
15. Hymenophyllum. Thecae on a narrow subclavate re- 
ceptacle within a two-valved involucre of the same texture 
mth the frond. 
** Theca without an elastic ring. 
Suborder III. OSMUNDACEiE. 
Vernation circinate. Rachis woody. Thecae regularly 2-valved, 
stalked, in clusters at the extremity of the frond. 
Tr. VI. OSMUNDEjE. 
16. OsMUNDA. Thecae clustered, arranged in a branched 
spike terminating the frond. 
