xii European Ferns. 
[Sub-Order Cyatheacece. — Sporangia sessile or stalked, surrounded by a vertical or rather 
oblique incomplete ring, splitting transversely, very numerous, and seated on a barrel- 
shaped receptacle to form dorsal globose sori. Indusium inferior, or none. Usually 
tree-ferns. No European genus.] 
Sub-Order II. POLYPODIACEAI. — Sporangia stalked, furnished with a usually incomplete vertical 
ring, splitting transversely, numerous, forming dorsal or marginal sori, with the receptacle 
not prominent. Indusium present or absent. 
* With an indusium, true or false. ( Involucratce .) Tribes I — 7. 
Tribe 1. Dicksoniecc. — Sori globose, situated on the back or apex of a vein. Indusium 
inferior, either covering the whole sorus, and bursting irregularly, or cup-shaped. 
Venation free or anastomosing. 
Genus 3. Onoclea. — Fronds dimorphic, the fertile ones contracted. Indusium 
semi-circular, becoming ragged and evanescent. Sori dorsal, confluent. 
Genus 4. Woodsia. — Fronds uniform. Indusium completely cup-shaped, with a 
fimbriated margin. Sori dorsal. 
Genus 5. Dicksonia. — Fronds uniform. Indusium forming with the segment a 
marginal two-lipped pouch. Sori terminal. 
Tribe 2. Davalliece. — Sori marginal or nearly roundish. Indusium scale-like, inferior, attached 
by a broad base, and free or attached to the frond at its sides. 
Genus 6. Davallia. — Indusium attached by a semi-circular base and sides, upper 
margin free. Sori marginal or terminal. 
Genus 7. Cystopteris. — Indusium attached by its base only. Sori dorsal. 
[Tribe Lindsayece. — Sori in a line at edge of the frond, and covered with its margin. Indusium 
membranaceous, short. No European genus.] 
Tribe 3. Pteridece. — Sori marginal, oblong or linear. False indusium, formed from the 
indexed margin of the segment, of the same shape as the sorus, opening inwardly. 
Genus 8. Pteris. — Sori occupying the intra-marginal arched nerve connecting the 
veins, and covered with a continuous false indusium ; a true indusium also 
present in one species. 
Genus 9. Adiantiun. — Sori occupying the upper part of the veins on separate lobules, 
and covered by distinct reflexed false indusiums. Fronds smooth. 
Genus 10. Cheilanthes. — Sori occupying the thickened apices of the veins, and 
covered by the reflexed false indusium. Fronds very hairy. 
Genus II. Cryptogr amine. — Sori occupying the unaltered apices of the veins, oblong, 
covered by the reflexed margin of the frond. Fronds dimorphic. 
Tribe 4. Blechncce. — Sori dorsal, parallel with the mid-rib and edge of the segments, but 
not close to the latter, oblong or linear. Indusium superior, opening towards the 
mid-rib. 
Genus 12. Bleclinum. — Fronds dimorphic. Sori in a continuous line, on longitudinal 
anastomosing veins. 
Genus 13. Woodwardia. — Fronds uniform. Sori in an interrupted line. 
Tribe 5. Aspleniecc. — Sori dorsal, attached to the veins, and oblique with respect to the 
mid-rib, linear or oblong. Indusium as in the last, sometimes double. 
Genus 14. Asplenium. — Sori linear, straight. Indusium nearly flat. Frond not 
scaly beneath. 
Genus 15. Athyrium . — Sori oblong-reniform. Indusium with a fringed margin 
