Liverworts (Marchantiophyta)
Photo by Jean PonziTiny green structures, low on the surface of our driveway gravel, have taken root in my mind. Or—since liverworts have no actual roots—they’ve embedded their hair-like rhizoids in my imagination. Who are these odd, miniscule plants? Where do they come from? How do they thrive?
I first “asked” Robin Wall Kimmerer, a PhD botanist and indigenous scientist, best-selling author, storyteller, MacArthur “genius grant” recipient, and my Green Hero. Her award-winning first book, Gathering Moss, focused on their plant group, the bryophytes. She calls out conventional science for labelling liverworts as primitive plants, for verbally reducing them to inferior status.
Dr. Kimmerer, from her global respect and fame, honors these humble plants as Ancients.
Studies of their mitochondrial DNA say that liverworts (phylum Marchantiophyta) were the first living beings to make the BIG leap onto land. The journal Nature reported in 1998 that liverworts are the oldest known land plants, who began, about 476 million years ago, to transform early Earth’s toxic CO2 terrestrial soup into a literal atmosphere of life-friendly oxygen.
BiologyDictionary.net says this drastic changing of global chemistry would later lead to “climate change and massive extinction events.” We know from contemporary climate science that change-at-scale has happened before, though never with the speed and intensity ramped up through our Homo sapiens actions.
Our venerable institution Smithsonian says, “The world of mosses, liverworts and hornworts, collectively known as bryophytes, form a beautiful miniature forest; nonetheless they are often overlooked, due to their small size and lack of colorful flowers.”
Indeed! Moss is well established along our driveway edge, but these liverworts? No idea how long they’ve been growing in community below our cars. Given my husband’s gravel weed-pulling vigilance, they may be new neighbors.
When I used my magnifying glass to genuinely meet them, I saw dark green, smooth surfaces and ruffly-edged leaf-like shapes, called thallae. Many of these have tiny cups (gemmae) budding from their surface. They also have Horton-Hears-A-Who structures sproinging up on tiny “stems”—some resembling umbrellas (archegonia), some looking like fans (antheridia)—which are the female and male reproductive parts, respectively.
Wee worlds on the gravel between our pick-up truck and car.
Like ferns, whose bio-lineage liverworts were long thought to share, these simple plants reproduce by distributing spores. Cells and wind! The drifter romance is one of Earth’s greatest hits.
Bryophytes are non-vascular plants: no roots or water-conducting tissue. They absorb water and nutrients from the air through their leaf-like surface. Most of them are only a few centimeters high. Without roots, they can grow where other plants can’t, on the surface of rocks, walls, and pavement.
They thrive in damp, shady environments, but we find these adaptable beings in the most extreme places, from deserts to the arctic. From Dr. Kimmerer’s viewpoint, what can we learn from beings who bring plant life-giving, life-supporting capabilities to places otherwise hostile to life? Everywhere on Earth!
Globally there are 7–8,000 species of liverworts, about 11,000 species of their moss relatives and 220-ish species of hornworts. Big-time diversity in small-scale spaces.
Reading about them buzzed my brain: sporophytes and gametophytes; haploid and diploid; mitosis and meiosis. I dodged fundamental science classes in my youth, but Indigenous Science perspective on these vivid little lives prompts me to learn both about and from these Ancestors in my driveway.
—Jean Ponzi
Green Resources Specialist, EarthWays Center