Filices.] • filices. 439 



No indusium. Spore-cases very crowded 2. Osmunda. 



Indusium of the recurved margins of the segment. Spore- 

 cases loosely scattered 5. Ceratopteris. 



Spore-cases very small, dotted, few together over the under surface 



of the pinnate- segments of dichotomously -branched fronds . . 4. Gleichenia. 

 Spore-cases (helmet-shaped, with a vertical or oblique ring, and usually 

 pedicellate) very small and numerous, in sori with or without an 

 indusium or involucre. 

 Sori longitudinal (elongated and parallel to the midrib), or cover- 

 ing the vjhole tinder surface of the fertile segments. 

 Sori continuous along the whole, or nearly the whole, length of 

 the segment. 

 Sori occupying the whole under surface. 



No indusium. Spore-cases densely crowded 6. Acrostichum. 



Indusium of the recurved margins of the frond. Spore- 

 cases loosely scattered 5. Ceratopteris. 



Sori in two distinct lines, at least when young. 



Sori between the midrib and margin (covering the surface 



when old). No indusium . . 7. Drymoglossum. 



Sori next the midrib, with an indusium . ...'... 8. Blechnum. 

 Sori interrupted (at least when young) along the midrih. 



Indusium longitudinal 9. Woodwardta. 



No indusium^ ., , . . 20. Brainea. 



Sori marginal, more or less continuous along the margin or ends 

 of the segments or their lobes. 

 Indusium longitudinal, parallel to the margin or formed by 

 the margin. 



Indusium opening along the outer edge 10. Linds^ea. 



Indusium opening along the inner edge. 



Spore-cases fixed to the inside of the indusium. Frond- 

 segments usually reniform or fan-shaped . . . .11. Adiantum. 

 Spore-cases fixed to the frond under the indusium. Seg- 

 ments lanceolate-oblong or obovate. 



Sori continuous along the margin 12. Pteris. 



Sori short, terminating the lobes 13. Cheilanthes. 



Indusium cup-shaped. 



Small creeping Ferns, with half-pellucid fronds . . . .24. Trichomanes. 



Fronds erect, firm, pinnate or decumbent 23. Davallta. 



Indusium coriaceous, 2-valved 22. Cibotium. 



No indusium (see below, Polypodies). 

 Sori globular or oblong, variously arranged over the swface or, if 

 linear, not parallel to the margin or midrib. 

 Sori indusiate. 



Indusium straight or slightly curved. Sori linear or ob- 

 long, oblique 15. Asplenium. 



Indusium peltate or reniform. Sori circular 16. Aspidium. 



Indusium cup-shaped or 2-valved. (See above, Sori mar- 

 ginal.) 

 No indusium (Polypodies). 



Sori along the margin 14. Notiiol^na. 



Sori linear, oblique . . . . 17. Grammitis. 



Sori short, parallel to the midrib. 



Sori in several rows 18- Meniscium. 



Sori in a single row near the midrib 20. Brainea. 



Sori round, or rarely slightly oval. 



Herbaceous Ferns. Sori circular or slightly oval, on a 



flat or slightly convex receptacle 19. Polypodium* 



Tree-ferns. Sori globular on a raised receptacle . . . .21. Alsophila. 



