A film to remember – the bordered filmy fern, Hymenophyllum marginatum

Hymenophyllum marginatum, the bordered filmy fern growing on an old log

Botanists like myself delight in simple pleasures, and seeing a plant that I have been wanting to see for quite a long time is one such simple pleasure.

Tasmania has 8 species of filmy ferns, and 6 of these hail from the well known filmy fern genus Hymenophyllum. Despite being a rather ancient fern genus among ferns, Tasmanian Hymenophyllums are easy to find and it is easy to see all of them in the course of a short walk, bar the elusive Hymenophyllum marginatum, the bordered filmy fern.

Of all the Hymenophyllums in Tasmania, this is the least collected (see link).

For years I pondered on the remote places I must venture to find this fern.

I imagined that it must grow in a hyper-wet rain forest environment and would require the eye of a connoiseur to pick out.

In any case, the chances of me seeing the bordered filmy fern was as slim as the filmy fern was filmy.

It was definitely not on mind on this rainy cold day at the Picton, the southern forested region of Tasmania.

I was navigating remote gravel roads looking for rain forest and I decided to survey a small patch by the side of the road and lo and behold, there it was, the bordered filmy fern, in it’s full bordered glory on a large rotting log.

The simple two lobing habit of the Bordered filmy fern

It would not be difficult to mistake for a liverwort, but because I had dreamed of seeing this exquisite fern for so long I recognized it the moment I saw it, even though it was the first time I had ever laid eyes on it.

This little filmy fern is unlike all the others in Tasmania in having typically only two lobes, thereby giving it the appearance of a large simple thalloid liverwort. It also has a bold black midrib. Upon closer inspection, one can see it’s namesake – the black border that lines the leaf margin. It is as if someone had used a very fine marker to outline the leaf!

A quick look around revealed also the spore-bearing structures (sporangia) at the tips of some of the leaves. These are basically flaps of tissue that enclose the spores.

Sporangia at the tips of the leaf

Five hours of driving and five hours of mucking in the rain is a small price to pay to have seen this “film”!

About David Tng

I am David Tng, a hedonistic botanizer who pursues plants with a fervour. I chase the opportunity to delve into various aspects of the study of plants. I have spent untold hours staring at mosses and allied plants, taking picture of pollen, culturing orchids in clean cabinets, counting tree rings, monitoring plant flowering times, etc. I am currently engrossed in the study of plant ecology (a grand excuse to see 'anything I can). Sometimes I think of myself as a shadow taxonomist, a sentimental ecologist, and a spiritual environmentalist - but at the very root of it all, a "plant whisperer"!
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