Filmy ferns, or ferns belonging to the family Hymenophyllaceae, are in interesting group of plants.
They are among some of the earliest lineages of ferns, but at the same time, they has a very simple structure, as far as ferns are concerned, because they are usually only one cell thick in most parts of their frond lamina (and thus the appellation ‘filmy fern’).
Being one cell thick, they have also no need for stomata (the microscopic ‘organs’ on the leaves of practically all plants that allow plants to transpire), as they simply dehydrate for a while when conditions get to dry, and rehydrate when it gets wet again.
In this latter aspect, filmy ferns are like many mosses and allied plants.
In particular, there a a group of plants called liverworts that are allied to mosses, and the simplest of liverworts are flattish green ‘mats’ known as thalloid liverworts. These liverworts tend to form some sort of a flat plate against their substrate.
Interestingly, there are filmy ferns that do the same, and one such fern is Didymoglossum tahitense.
Being a aficionado of mosses and liverworts (bryophytes in general), small and green like filmy ferns pique my interest easily, and especially anything that appears flattish and formless.
Thus it was that on a tree in Cape Tribulation, Queensland, I spotted Didymoglossum tahitense.
It is one of the strangest filmy fern I have ever seen and has got to be witnessed to be believed.
More likely, it might be overlooked by most botanists as some algae, liverwort, lichen, or possibly a discoloration of tree bark!
But upon closer inspection, the exquisite roundish and innervated fronds are unmistakable.
It never fails to amaze me how plants “aspire” to “emulate” or “impersonate” (or in some cases perhaps more accurately “mimic”) one another. Thus we have mosses trying to “act” like trees, herbs that grow into the dimensions of trees, trees that better considered herbs, grasses that try to be trees.
I can tell you a story of the reverse, where a liverwort is “impersonating” a filmy fern, but that shall be in another post!