This Trichomanes has distinctive black stems, that extend into the individual leaflets of the fern. It is a shiny, beetle like black.
Recently spores have appeared in the form on a little lantern hanging off the tips of one frond. This was the first time I had seen this type of structure on a filmy fern. They are rather big and contain hundreds of spores, although when you look through the papery capsule, it looks more like a single black seed.