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

A Closer Look at a Fern

.....specifically, the Sori and Sporangia.

I spent some time photographing a fern today for the purpose of learning more about these pteridophytic plants. I particularly wanted to have a closer look at the little spore containing receptacles that are found on on the underside of fertile fronds.

Fronds of the Kangaroo Fern -  Microsorum pustulatum

The Kangaroo Fern, Microsorum pustulatum, in the above photo is growing on the trunk of a Tree Fern, Dicksonia antarctica. If you look closely at the enlarged photo you can see the rhizomes working their way through the fibrous trunk of the Tree Fern. On the upper surface of the fronds you can see little dimples marking the locations of the reproductive structures which are on the underside. These are the spore containing structures that I wanted to have a closer look at.

Turning the frond over we can see these raised spots arranged along the underside. These are known as sori, or in the singular, a sorus. On this specimen the sori are about 4mm in diameter. . So where are the actual spores? Let's look closer!

Each sorus is tightly packed with sporangia

This photo shows that the sorus is actually tightly packed with little capsules known as sporangia (singular, sporangium). Notice that the sporangia are open to the air. In some ferns there is a little cap that covers them until they are mature. The cap is known as an indusium. The presence or absence of an idusium can be a useful feature in identifying ferns. Another useful feature for identifying ferns is the shape and position of the sori.

Closer view of the sporangia

Getting up close you can see that each sporangium is a little capsule. These capsules open when mature. The microscopic spores are then released to be spread by the wind.

Ferns Along Seabrook Creek

...at the Frenchs Road Nature Reserve.

Anyone interested in ferns would thoroughly enjoy visiting the Frenchs Road Nature Reserve. The site consists of 34  hectares of remnant forest along Seabrook Creek, not far from Somerset and Wynyard in Tasmania.

Quoting from the sites information brochure:

The native vegetation of the Reserve is predominately of two types:

•  Dry Stringybark (Eucalyptus obliqua) forest on the drier and low nutrient slopes with Tea Tree and Wattle.  
• Wet (Stringybark ) forest in the lower areas and along the creek (riparian zone). This wet forest understorey consists of majestic tree ferns with epiphytic ferns, tall blackwoods (Acacia melanoxylon) Tasmanian Pepper and the occasional Sassafras and Myrtle-Beach.

The purpose of my visit was simple. No, not ferns. Birds! I was particularly looking for Pink Robin and Scrubtit.  Unfortunately the birds had other plans for the day. There were plenty to be heard but very few to be seen aside from a Grey Fantail, a Superb Fairy-wren, and a Brown Thornbill. Honestly, that was it! I see a greater variety of birds in the town centre. Next time I'll have to go a little  earlier in the day, when the birds are more active.

Watch the video and listen to the invisible birds :-)

Despite the lack of avian accompaniment I still enjoyed my short walk along the damp and ferny banks of Seabrook Creek. Since the birds refused to co-operate, my attention soon moved on to the ferns  (they can't hide). I came home with several photographs needing to be identified. While reading Gouldiae's Blog recently I was motivated to learn a little more about our local ferns and this was an opportunity to get started. Currently my only reference on the subject is a small book with black and white photos from 1975. Unfortunately that book is temporarily packed away in storage so I resorted to the Internet to identify them. Feel free to offer corrections :-)

Kangaroo Fern - Microsorum pustulatum

Fishbone Water-Fern - Blechnum nudum

Scrambling Coral Fern - Gleichenia microphylla

Bat's wing fern - Histiopteris incisa

Manfern or Soft Tree Fern  lining the bank - Dicksonia antarctica

For a "A Closer Look at at a Fern", click here.

Linked to Our World Tuesday