Filmy Ferns

...  Family Hymenophyllaceae

While at Fern Glade recently I took some time to photograph a small epiphytic fern which I often see growing on the trunks of Tree ferns. They are known as Filmy ferns because in most species the leaf is only one cell thick, giving them a filmy appearance. As always, there are exceptions such as Sphaerocionium applanatum, where the leaf appears to be thicker due to a covering of tiny hairs.  One characteristic of the Filmy Ferns is that they lack any stomata. Stomata are small openings on the leaf that allow the exchange of gasses, including water vapour. They close when dry to prevent dessication.  Not having this ability, the filmy Ferns can only survive in very moist areas.

Tasmania has three genera of Filmy Ferns with a total of eight species. They are found in wet forests on rocks or as epiphytes.  Using the Key to Tasmanian Vascular Plants I was able to identify the fern in my photographs as Hymenophyllum flabellatums. However, in the background of some of my other photos there appear to be other species of Filmy Fern growing on the same trunk. I’ll have to look a little closer next time around.

(Click any photo to enlarge)

Hymenophyllum flabellatums

Detail showing the sori and the sporangia

Filmy Ferns covering the trunk of a Tree Fern