Phylum 1. PTERIDOPHYTA. 
Ferns. 
Key to the Genera of Ferns Mate 
Plants floating on still water or stranded on wet banks. 16. Azolla. --12 
Plants rooted in soil or in crevices of rocks. 
Fertile leaves each with a single axillary spore-case; aquatic or 
marsh plants with. grass-like leaves. 3. Isoetes. __10 
Fertile leaves with many spore-cases, these never axillary. 
Leaves with four leaflets, resembling four-leaved clover; spore- 
cases produced inside of hard bean-like structures (modified 
leaves?) called sporocarps. 15. Marsilea. __12 
Leaves various, but not as above. 
Spore-bearing leaves consisting of a blade and a fertile spike 
or panicle. , 
Leaf-blade simple, entire; spore-cases cohering in two rows 
on the simple spike. 1. Ophioglossum. --10 
Leaf-blade lobed or divided; spore-cases not cohering. 
2. Botrychium. __10 
Spore-bearing leaves not as above. 
Fertile leaflets rolled up into bead-like bodies. 14. Onoclea. __12 
Fertile leaflets contracted without green blades; spores 
green. 4. Osmunda. --10 
Fertile leaflets like the sterile, or differing only in size and 
form; spore-cases in clusters called sori, on the under 
surface of the blades. 
Sori covered by the inrolled edges of the leaflets. 
Plants growing in moist woods; leaflets without a dis- 
tinct midrib. 6. Adiantum. __11 
Plants growing on dry rocks; leaflets with a midrib. 
Leaf-stalks green or yellowish, fertile leaves quite 
different from the sterile. 7. Cryptogramma, __11 
Leaf-stalks dark, fertile leaves with narrower leaflets, 
otherwise like the sterile. 
Leaves smooth. 8. Pellzwa. __11 
Leaves tomentose. 9. Cheilanthes. __11 
Sori not covered by the edge of the leaflets; naked or 
covered by special indusia. 
Sori linear or oblong, twice as long as wide. 
Xerophytic rock fern with naked sori. 5. Notholena. __11 
Mesophytic plants, sori covered by indusia. 
10. Athyrium. __11 
Sori rounded, not twice as long as wide. 
Indusium rounded, with a notch at one side where it 
it is attached. 11. Dryopteris. __11 
Indusium not as above, often disappearing. 
Indusium hood-like; leaf-stalk with two  fibro- 
vascular bundles. 12, Pilix, . 31 
Indusium under the sorus; leaf-stalk with a single 
bundle, except at the base. 13. Woodsia. __12 
(9) 
