http://cfern.bio.utk.edu/resource/resource.html

Dilute 1 part stock solution with 9 parts distilled water.
To one liter of diluted solution add 1 mL 1% ferric chloride solution just before use. Then add 16 grams plain agar per liter, boil until agar is dissolved and sterilze in autoclave. Pour petri dishes at least half full to delay drying out.

My beginning botany classes have had excellent results growing C fern spores from Carolina Biological with this medium. We sometimes get some fungi in the plates, but it doesn't seem to affect the ferns. We also tried spores from a Boston fern and found that almost every one of them grew. Next time I will know to make a dilute suspension of the spores to spread them more thinly.
I have also grown C fern spores easily in potting soil, covered to prevent the surface from drying. Using agar and petri dishes gives students a little experience with scientific equipment.

Anna