These are robust ferns with fronds averaging over three to four feet long (1-1.3 m). If you were with me this time last year in the woods near Natchez, Mississippi, you might remember our seeing the Southern Shield-Fern, Thelypteris kunthii, still shown at http://www.backyardnature.net/n/h/shield-f.htm.

These two species belong to the same genus, and are closely related within the genus. One of the most conspicuous features separating them is that our Roughhairy species is -- rough and hairy, as shown below:

In that picture the dark, spherical items are the "fruit dots" or sori. Each sorus consists of many sporangia, which are the blackish, spherical little things in clusters in the picture. Inside each sporangium many spores are formed. Clearly, then, spores are very small. You can get an idea of how many spores must be produced from the fern's very many sporangia by looking at a small section of one frond below:

In the center of each sorus there's what looks like a more or less circular piece of brown paper. That's what remains of the indusium, which is the cellophane-like covering found on many sori. In the picture it looks like the indusia are attached at their centers, thus constitution the top part of an umbrella-shaped structure. Actually indusia in the genus Thelypteris are C-shaped, but often with the ends of the C almost touching, so that at first glance they can look like Os. Thelypteris's C-shaped indusia are attached to the frond along their sides. These seemingly unimportant details are very important to nail down when identifying ferns. You can see a Roughhairy Maiden Fern's frond with freshly developed indusia covering immature sori, better showing their C-shaped nature, below:

Roughhairy Maiden Ferns occur in the southeastern US, Mexico and the West Indies south through tropical South America, plus tropical Africa, Australia and southern Asia. The species is divided into four subspecies, and ours is not the same subspecies as in the US. One feature worth noting of our plants is that the fronds arise from exceptionally thick stems that creep along the cistern's mossy surface, as shown below:

That stem is about 15 mm thick, over half an inch.

The Flora of North America describes its habitat as "Woodlands and limestone sinks, especially in seepage areas and along streams." That doesn't mention cistern walls, but with our cistern walls composed of cemented limestone rocks long saturated with water, I'd say that the fern must feel at home here, anyway.