What exactly are filmy ferns?

Hallo,
This is how Professor Madhusoodanan describes them on the internet and I could not ad much more to it:

"The filmy ferns are a unique group of plants among pteridophytes characterized by sporangia aggregated on cylindrical receptacles enclosed in characteristically shaped indusia and the one cell thick, delicate lamina lacking stomata. Owing to their delicate plant body these plants are confined to the deeply shaded pristine evergreen forests, usually in the spray zones of waterfalls, on rocks and boulders of streamlets or attached to the bark and buttresses of shrubs and trees near the perennial water sources."

Here are some species of ferns that are filmy ferns:
-Trichomanes agasthianum
-Trichomanes indicum
-Trichomanes lunulatum
-Trichomanes malabaricum
-Trichomanes proliferum Blume var. minutum
-Trichomanes proliferum var. proliferum

If you look to this link:
http://images.google.be/images?q=filmy%20ferns&hl=nl&ie=UTF-8&oe=UTF-8&um=1&sa=N&tab=wi
you'll find lots of pictures of filmy ferns.

Interesting plants,look a bit like mosses, and a bit like seaweeds!
Thanks for the info!

Danny, do you post on www.baumfarn.at ?

Here is a link that might be useful: Tree Ferns etc

Yes, I do post on www.baumfarn.at and I'm also on a Dutch forum called Tuinadvies where I'm the moderator for the topic "ferns and tree ferns"