400 Million Years of Ferns

Ferns are all leaf, all the time—no celebrated flower, no seduction of the insect. At the tips of green sprouts, curled fiddleheads unroll while leaflets widen behind them like the wakes behind boats. My store-bought Boston fern, tended for years with no expertise, is a fountain of green, its dazzling fans of leaves arching up, out, and over.

Before ferns, plants were creatures of the water, with no need for roots or stems. But about 450 million years ago, Earth passed through the first of its five mass extinctions (so far). The climate cooled, water froze, glaciers grew, the sea level fell, coastal and ocean habitats disappeared. But new land was exposed, and when the climate warmed again, plants grew there.

The first of these land plants were mosses. Carpets of moss sprang up along lakes and streams. But without deep roots or firm stems, mosses grew no higher than a few inches. Thriving on land requires tubes that can carry liquids up and throughout an organism. Ferns were among the earliest plants with roots to dig deep for water, and with stalks and stems to transport it throughout the plant. Vascular tissue changed everything. Ferns reached the height of trees.

Devonian ferns wikimedia

wikimedia

And ferns grew very efficient leaves. They needed them to capture carbon dioxide whose levels fluctuated widely over the millennia. Whenever the atmosphere’s declining carbon dioxide led to cooling temperatures, the hundreds of leaves on even a small fern could soak up enough to keep it going. Today, healthy ferns withstand cold weather better than most plants.

Ferns have multiplied the world over in part because of how they propagate. They were and are old-fashioned and deliberate about sex. Instead of reproducing through miniaturized plants embodied in seeds, ferns spread through spores, single cells released from the underside of the fronds. When the spores settle on moist soil, they grow into a tiny intermediate plant that will create the male and female components for the start for a new fern. Spore propagation seems an overly complicated, two-step process, but the lightness of the spores lets them disperse on the wind and germinate on distant moist soil.

Some days I stare at a plant whose distinctive features date back nearly 400 million years. No other plant or animal that I see every day goes back almost to the beginning of life on land. A fern’s ancestors invented leaves and roots and the old method of reproducing.  They survived four mass extinctions, as well as the flowering plants that burst on the planet 125 million years ago and came to dominate the plant kingdom. Ferns watched the dinosaurs come and go. Today they regale us with tales of ancient climates and their ingenious survival skills.

 

 

6 thoughts on “400 Million Years of Ferns

  1. We have some ferns that volunteered in our front yard. I’m used to thinking of ferns as touchy and hard to nurture. But these sprouted on their own, both in full sun and in the darkness under our porch. You’re telling me that they are to their ancestors what birds are to the T-Rex. Thank you for that. I’ve admired their tenacity and it’s good to know their history.

  2. Douglas, sorry for the delay in responding. Yup, I was a city boy. Any volunteer plant that tried to put down roots in Central Park in the 60s would have had my admiration if I’d known about it.
    I’ve been trying to find out more about the word “volunteer,” plants and other types. The early uses of the term in the U.S. were in military contexts like the conflicts in the south and southwest–the war with Mexico, the volunteers from states like Tennessee (“The Volunteer State”) to fight the War of 1812. Farm country. There’s something about the organization required in using troops to fight wars that reminds me of the planning that goes into growing corn and bean crops. In both cases, at least, the volunteer soldiers and volunteer plants don’t conform in some way. Their “behavior” is different–young men willing to risk death, seeds ‘willing’ to take root in unusual places. That’s vague, I know. But “volunteer” is such an interesting label for a plant.
    Thanks.

    Brock

    • Interesting. We grew up with several uses of volunteer. First was related to community service, giving of one’s time and talents for the benefit and betterment of the community. O gre up in the Mennonite church and service is a primary focus. Second, in the context of the American war in Viet Man, my cohort was either drafted or volunteered; not many of the latter. The the volunteer plants, especially corn coming up where it was not supposed to be. If beans were planted in a field that had been corn the previous year, there were always a few volunteer corn stalks that had to be pulled out. 😁

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