This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
The vagaries of evolution can launch species on startling trajectories. Stringy Spanish moss – draped from trees like party streamers across the South -- is actually in the same family as pineapple. Duckweed, an adorable little plant that casual observers often refer to as pond scum, is actually in the same family as the peace lily and taro (Polynesian power plant and source of everyone’s favorite bland purple food).
And then there's this. Would you guess that this plant is a fern?
In spite of its suave flowering plant looks, this plant is indeed a fern -- a kidney fern.Ferns are primitive plants that lack flowers (extravagant, fragrant plant genitalia evolved to turn plant sex into a menage à trois with a second species) and seeds (plant embryos pre-stocked with food for the baby plant). Instead, they make microscopic, single-celled reproductive units called spores and have a schizophrenic life cycle in which two plants that look nothing alike take turns existing, a phenomenon called the Alternation of Generations. And unlike flowering plants and conifers, but like animals, ferns still make sperm that must swim to an egg as part of that life cycle, part of the reason they prefer steamier habitats.
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The kidney fern wears its own reproductive structures like an elegant crown, as you can see in the seventh, eighth, and ninth photos in this collection. The blackberry-like clusters set in the reproductive tiara are sporangia containing many spores, each with a ridged annulus like the bristles on a Roman helmet.
But filmy ferns possess some quirks unto themselves. That translucence, for instance; the juvenile frond of a kidney fern is only one cell thick. There aren’t many land plants you can manhandle to experience what the width of a single cell feels like. But in New Zealand – where I recently spent some time -- it’s far from the only.
The deliciously-named Filmy Fern Family contains 600 species rarely found outside the tropics, but soggy New Zealand is one such place and is home to 31, many of which, like the kidney fern, sport fronds only a single cell thick. That is one reason I was so delighted to see them; having spent little time in the tropics and living in a place where unattended brown sugar becomes sandstone within hours, I’ve had little opportunity. After a while, I had to suppress the urge to touch every one I saw to keep my hiking partners from killing me.
Yet another filmy fern quirk springs from their lack of waxy cuticles that most plants use to seal in water. As a result, filmy ferns dessicate easily. But because they are poikilohydric like mosses -- another primitive, or ancestral, trait -- and thereby adapted to survive complete water loss, they spring back to life upon rewetting. If you’ve ever tried this with a flowering plant (and many, many people have run this experiment), you will find the results considerably less satisfactory.
Flowers? Well, no. Superpowers? Hell, yeah. Primitive doesn't mean powerless -- or inferior. Just first.
