In that humid, shadowy, pretty little valley with many big-leafed magnolias, in the moistest, most shadowy corners where white limestone rocks jutted from moss-encrusted soil, a seldom-seen fern was common. You can see it, still wet at midday from the night's rain,below:
The fern is LlAVEA CORDIFOLIA, and I can't find a common name for it. It's found in Mexico, Guatemala and Costa Rica.
Average ferns have their spore-producing "fruit dots," or sori, on the undersides of their fronds' leaflets, or pinnae. This fern has segregated its sori onto very slender, cordlike pinnae at its fronds' tips. On older fronds the fertile parts were dark brown, giving the appearance of being diseased.
Some other ferns also produce different-looking spore- producing pinnae on their fronds -- such as the Interrupted Fern, Osmunda claytoniana -- but I can't think of any who do it quite like this. In fact, this unusual placement of the fertile pinnae helps explain why there is only this single species in the entire genus Llavea -- and sometimes the genus Llavea has resided alone in its own family, the Llaveaceae.
When a genus is represented by only one species, it's said to be "monotypic." Often with monotypic species it's a good guess that once several species existed, but all but that one went extinct. That's the way it is with Ginkgos, for instance. Once many ginkgo species existed but now there's only one, Ginkgo biloba.
So, already I was feeling as if I had stepped back in time when I entered that secluded little valley. When I found Llavea so well established in its refuge, the feeling only grew.