A jagged, fissured promontory of conglomerate sandstone overlooks a gorge in Jackson County, Ohio. I have made a few trips to this scenic southeastern county in the last week or so, for various purposes, and on each visit took time to inspect some rocks.
The delicate little beauty above is mountain spleenwort, Asplenium montanum. You'll have to inspect craggy sandstone cliffs to find it. With a toughness belying its fragile appearance, mountain spleenwort lodges itself in the smallest of crannies, deriving sustenance from the meager soil that collects in such places.
The fern world is fraught with cross-breeding. At least 21 hybrid combinations have been documented in Ohio alone. The spleenworts are among the worst of the lot when it comes to fidelity to their species. The eight spleenwort species known from Ohio are augmented and confused by six different hybrid combinations.
But it's this rampant infidelity that adds another layer of interest to our most ancient lineages of plants.