The deep limestone crevices along the escarpment provide perfect habitat for several ferns that like both the limestone and the cooler-than-normal microclimate, and survive in the sometimes dim light. Among these are the common maidenhair spleenwort, found all along the escarpment, and the much rarer green spleenwort, a more northerly species that specifically needs the cooler temperatures and shade.
The maidenhair spleenwort is often seen in its small clumps of fronds, growing directly out of the vertical rock face. Fronds are only a few inches long, and leaves might be a quarter inch.
This close-up taken looking up the cliff from beneath, shows both the characteristic black wiry stem down the middle, and the linear spore cases on the back of the leaves.
The green spleenwort has slightly more irregular shaped leaves, but is particularly characterized by a green stem down the middle. It was so shaded in this crevice that I had to use a flash at mid-day to get a clear picture, resulting in the slightly shiny leaves.
A closer look clearly shows the green stem of the green spleenwort. So take a closer look next time you're along the trail deep in a crevice, and see if you can find this one.