22 I. — FILICES. 



II. — Sori at the apex of a vein, just within the margin. 



Involucre a 2-valved cup ; large tree-ferns 5. Dicksonia. 



Tribe III. — HymenophyUaceaB. Sori on the extremity of a vein, and 

 hence on the margins or apices of the frond or its segm,ents. Capsule 

 sessile, rounded or pea/r-shaped, attached usually hy the centre to a 

 filiform receptacle, which is often exserted ; ring oblique or transverse 

 completely surrounding the capsule, which therefore dehisces longi- 

 tudinally ; involucre 2-valved, or tubular. Most ferns of this tribe 

 are small, and of a very thin, semi-transparent consistence, and m,any 

 a/re epiphytes. (PI. I. figs. 6-8.) 



Involucre tubular; mouth entire, con- 

 tracted ; capsules with a short, 

 incomplete ring. Fronds coriaceous, 

 opaque 6. Loxsoma. 



Involucres 2-lipped or 2-valved. Fronds 



thinly membranous 7. Hymenophyl- 



Involucre 2-lipped ; mouth more or less lum. 



2-lipped ; receptacle often considerably 

 exserted. Fronds usually membranous 8. Trichomanes. 



Tribe IV. — Polypodiacese. Sori on the margins or back of the frond, 

 with or without an involucre, amd destitute of a raised or elongated 

 receptacle. Capsules all stalked, furnished with an incomplete vertical 

 ring, and bursting tramsverseh). This is by far the largest fam/ily q/ 

 ferns, and is dioided into nv/merous groups. 



Section I. — Sorus with an involucre. 

 Family I. — Davalliese. Sori covered with a reniform or orbicular 

 scale-like involucre, which is always open at its apex. (PI. I. fig. 9 ; 

 and PI. II. fig. 1.) 



Involucre at the tip of a vein or segment, 



attached by its base and sides ... 9. Davallia. 



Involucre in the middle of a vein, at- 

 tached by its broad base only ... 10. Cystopteris. 



Family II. — Lindsayese. Sori in a line near the edge of the frond. 

 Involucre opening outwards, the inner 

 valve being membranous, the outer 

 formed of the margin of the frond. 

 (PI. II. fig. 2.) 11. Lindsaya. 



Family III. — Pteridese. Sori oblong or linear, on the margins ; 

 involucres opening inwards, of the same shape as the sori, and formed 

 of the more or less recurved maJrgin of the frond. (PI. II. figs. 3-8.) 

 Sori oblong or reniform ; involucre of a 

 difierent texture from the rest of the 

 frond. Segments' of the frond usually 

 1-sided .... 12. Adiantum. 



