John Nelson is the curator of the Herbarium at the University of South Carolina, in the Department of Biological Sciences, Columbia SC 29208. As a public service, the Herbarium offers free plant identifications. For more information, visit www.herbarium.org or call 803-777-8196.
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Coal beds rich source of ancient plant remains

  • Thursday, November 15, 2012

This week’s mystery plant has a long, horizontal stem, flat on the ground, which is usually covered by the leaf litter.


Three hundred million years ago it looked a lot different outside. For one thing, it was a very damp, humid time over much of the earth. Don’t worry; there wouldn’t have been any dinosaurs to chase you around. (They came a LOT later, as did the cavemen.)
But there was plenty of vegetation, of course. Large forests dominated major portions of the earth's landscape, including much of what is now Europe and North America.
These forests didn't have any oak trees or elm trees, though. Oh, no. This was the age of the ferns, and I'm not talking those little old things you buy in a flower pot to grow in your parlor, I’m here to tell you. The ferns back then, and their relatives, were major-league plants, some attaining the size of very huge trees. Whoo-boy! Of course, then, just like today, the trees in forests eventually aged, died, and fell over. Over the several million years of the domination of these giant ferns and their “allies,” untold tons of rotting vegetation accumulated consistently, and a major result of this was the slow development of enormous subterranean strata of coal. In fact, modern coal beds tend to be an extraordinarily rich source of the remains of ancient plants. Coal really is, literally, a fossil fuel if there ever was one.
Nowadays, though, the ferns around the world are much smaller, only attaining tree-size in some groups. (Well, the “tree-ferns,” of course.) In North America, there are about 450 species of native ferns and fern-like plants. These are a fascinating group indeed, all reproducing by spores, none ever producing flowers or seeds.
Our Mystery Plant is a common evergreen, herbaceous species, usually thought of as one of the fern “allies.” It has a long, horizontal stem, flat on the ground, which is usually covered by the leaf litter. This stem sends up a number of fan-like branches along its length, and the effect is of a series of tiny pine trees (or maybe cedars) running in a line along the ground. The leaves on these branches are quite small, shiny and dark green. We say that these branches are sterile, in that they produce no spores. Now and then, though, when the mood strikes, the plant will indeed produce “fertile” branches, which look much different and bearing, at their tips, slender cones which eventually form the spores. The spores eventually fall or drift away from the cones, and eventually start up new plants. You can find this fern ally in shady woods and also open meadows, from eastern Canada through the upper Midwest, and south to Georgia. Here in the South, it is most often seen in the piedmont and mountains. There are a number of related species which look somewhat similar.
Over the years, this little plant has achieved quite a reputation. It's been used extensively as a Christmas decoration, commonly pulled up by the yard and sold to make wreaths. Move over, holly

[Answer: “Running cedar," "Ground pine," Diphasiastrum digitatum]

John Nelson is the curator of the Herbarium at the University of South Carolina, in the Department of Biological Sciences, Columbia SC 29208. As a public service, the Herbarium offers free plant identifications. For more information, visit www.herbarium.org or call 803-777-8196.

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