"A very singular and very pretty plant ... [leaflets] are rounded and hollowed, and thence its name came of Moonwort" Sir John Hill, 1770. (image from Atlas der Alenflora 1882).

About 2075 years ago, during the first century BCE, Roman philosopher Cicero wrote of introductions—their importance and how they should be constructed (1):

"one's opening remarks, though they should always be carefully framed and pointed and epigrammatic and suitably expressed, must at the same time be appropriate to the case in hand; for the opening passage contains the first impression ... and this ought to charm and attract the [reader] straight away."

After looking up "epigrammatic" (relating to a short saying or poem that expresses an idea in a clever, funny way), I sat down to construct an introduction "appropriate to the case in hand" — Moonworts.

First the epigram, from Botrychium lunaria by Giles Watson.

Hear the latch click in the gloom,

Thus gain admittance to the room.
By fern and stealth, no guile nor wealth
Can buy a lock to hinder me. 

Now the charm, of which there's no shortage!

After an unknown number of years underground, Botrychium simplex grows a leaf (J. Hollinger).

Moonworts (Botrychium species) are attractive little ferns, and it's unfortunate they're rarely seen. They live mostly underground in the intimate company of Glomus—a fungus that forms mutually beneficial subterranean relationships with nearly 80% of vascular plants. Typically Glomus supplies nutrients to the plant, and the plant supplies Glomus with carbohydrates via photosynthesis. But photosynthesis requires sunlight, so how can a Moonwort make carbohydrates if it lives underground? Maybe it's a parasite rather than a partner. This is just one of Moonworts' mysteries.

When conditions are right (another mystery), or perhaps when the stars align, a Moonwort sends up a single leaf. Though distinctive it's difficult to spot, being small, short-lived, and often hidden in vegetation or duff. But lucky is the finder of a Moonwort! If collected by the light of a full moon, the fertile part can be used to pick locks, unshoe horses, and turn mercury to silver.

Moonwort leaf with a sterile leaflike trophophore and a fertile (magical) sporophore; closeup shows sporangia have opened and released spores (Britton & Brown 1913).

Mingan's Moonwort releasing spores; soon it will wither and be gone (R&N Crawford).

The first known scientific description of Moonwort appeared in 1542, in a revolutionary herbal by physician and botanist Leonhart Fuchs: De Historia Stirpium Commentarii Insignes, Notable Commentaries on the History of Plants. It contained 500 high quality and largely accurate illustrations to help with identification—a novel approach which Fuchs felt obliged to explain: "a picture expresses things more surely and fixes them more deeply in the mind than the bare words of the text."

Lunaria minor, from Fuchs's 1542 herbal. BHL

Leonhart Fuchs c. 1543 (source).

Descriptions in Fuchs's herbal were brief and often "borrowed" from earlier works, an accepted practice. Lunaria minor was said to have a round stem, with a single leaf divided into seven parts and with a stem atop which were seeds (fern reproduction was assumed to involve seeds, though none had been found).

Lunaria minor (the name) and Moonwort seeds would persist for several centuries. Then in 1753, pioneering plant taxonomist Carl Linnaeus put Moonworts in the genus Osmunda (but he too referred to seeds; spores weren't accepted until the mid 1800s). In 1845, Czech botanist Carl Presl moved Moonworts to the genus Botrychium, where they mostly reside today (2), and recognized 17 species. But in the first "modern" treatment of Moonworts, Jens Clausen (1938) reduced this to just six, all of which occurred in both Europe and North America.

We look back on Clausen's classification as much too simplistic. But nearly 50 years would pass before someone took enough interest in North American Moonworts to do something about it—specifically Warren and Florence Wagner, who upped the number to 22. Study and discovery have accelerated since. Currently 38 Moonworts are known for North America (Farrar 2024), with several more species in the pipeline.

A recently-described North American Moonwort—Botrychium farrarii (Legler & Popovich 2024). Note variation.

With so many species and such small plants, Moonwort identification is notoriously difficult (3). Characters are often minute (10x magnification helpful). Differences can be subtle, relative, and variable. No wonder we're regularly referred to experts for confident id. And the experts may resort to molecular techniques (e.g. DNA, enzymes) for verification.

Be there dragons here?

It's November and The Monthly Fern series is winding down. Looking back, I realized that most of the ferns I chose are distinctive—they're aquatic or have dimorphic leaves or are primitive lycophytes or grow large enough to inveil a romantic tryst! So this month's post will feature the ferny ferns (my term)—the ones we immediately recognize as ferns. However, figuring out which specific kind isn't guaranteed. If only ferns had flowers—so showy and diverse! Instead we must rely on leaves (1).

Prairie Quillwort is 50 centimeters tall (© 2015 Robbin Moran); Scale Tree is 50 meters tall (source). Both are lycophytes—formerly "Fern Allies".

This episode of The Monthly Fern was going to feature Isoetes melanopoda, the Prairie Quillwort, mentioned last month in the wildly popular Prairie Spikemoss post (1). But in my search for information I fell down a rabbit hole and landed with a splash in an ancient Wonderland—a wet lush forest 350 million years ago near the start of the Carboniferous Period (2). After extricating myself from the muck I looked around. Tree ferns, horsetails and dragonflies looked familiar, though a bit large. But the trees were very strange.

It was during the Carboniferous that wetland forests with tall trees first appeared in the fossil record. These were hot humid riotous tangles of vegetation growing in shallow water and muddy peat that reeked of decay. Dense stands of curious trees rose high above the understory. The most common (or best preserved) was Lepidodendron, the Scale Tree. "Scale" refers to the distinctive bark—a network of diamond-shaped leaf scars (Halliday 2022).

Wetland forest of the Carboniferous; large Lepidodendron on left (Meyers Konversationslexikon 1885–1890).

Though they've been gone for 300 million years, we know a lot about these trees. Their fossilized remains are among the most extensive for any plant from any geological period, and for good reason. Not only was Lepidodendron large and ecologically dominant, it lived in waterlogged conditions conducive to preservation. Paleontologists have been able to describe features ranging from spores to leaves to trees, and even stands of trees (Hetherington et al. 2016).

Lepidodendron differed in many ways from the trees we know. Stems of young trees were covered in long ascending needle-like leaves. These fell off as the tree grew taller and wider, leaving a spiraling network of diamond-shaped scars on the trunk. With age the trunk developed a thick tough outer layer—bark of sorts—but underneath was soft spongy tissue instead of wood. At maturity the stem branched dichotomously (repeatedly forked), forming a high crown as much as 50 meters above the ground. The final branchlets were tipped with strobili (cones) filled with spores, to be dispersed by wind (source). This so-called "tree" was an arborescent lycophyte, a fern relative.

Juvenile and mature Lepidodendron on left; trees to right are related lycophytes. Reconstruction from fossils, by Falconaumanni.

Given Lepidodendron's massive build, its lack of internal wood and the waterlogged habitat, it seems it would fall before reaching such heights. What kept it upright? Some credit the thick tough bark. But others argue convincingly for the robust root system. From very long rhizomes grew a profusion of highly-branched rootlets covered in root hairs—on the order of 26,000 rootlets per meter of rhizome! They intertwined with those of adjacent trees, forming a strong anchoring network—"trees holding onto one another for stability" (Hetherington et al. 2016; Halliday 2022).

Lepidodendron truly was an arboreal superstar, dominating the wetland forests and producing immense amounts of biomass for tens of millions of years (3). But it was doomed. By 300 million years ago, the Carboniferous rainforests and arborescent lycophytes were gone, destroyed by widespread drought. Lepidodendron's only surviving relatives are little herbaceous plants—Isoetes, the quillworts.

Bolander's Quillworts in a lake in the Wasatch Mountains, Utah. Andrey Zharkikh photo.

Now we return to the present—to a roadside waterhole along highway #44 in Mellette County, South Dakota, where W. H. Over (4) made his 15,878-th plant collection on July 10, 1924. Isoetes has not been collected in the state since.

Over correctly identified his collection to genus—Isoetes. Four months later, TC Palmer called it I. melanopoda, and Daniel F. Brunton agreed in 1995. The specimen resides at the Academy of Natural Sciences, where it has been digitized for all to enjoy (cropped here).

Like all quillworts, the Prairie Quillwort has no stem. Instead a cluster of leaves develops from the rhizome. From a distance these look like clumps of grass, but up close the leaves are distinctive—long, slender, quill-like, and bright green. The leaf bases are broad and pale, forming a swollen rootstock. These usually become black with age, hence the alternative common name—Black-foot Quillwort (plants with leaf bases that remain pale have been called I. melanopoda f. pallida).

Isoetes melanopoda; MWI photo.

Being a lycophyte, Prairie Quillwort produces no seeds. Nor does it have rows of spore-bearing sori on the undersides of its leaves as do most true ferns. Instead, spores are produced in a sac on the inner side of leaf bases.

Isoetes melanopoda; MWI photo.

Surely some readers are wondering ... how is little Isoetes like immense Lepidodendron? Why do botanists think they're related? Answer: It's the roots, especially the way they branch.

"this architecture is conserved among [Lepidodendron's] only extant relatives, herbaceous plants in the Isoetes genus. Therefore, despite the difference in stature and the time that has elapsed, we conclude that both ... have the same rootlet system architecture." (Hetherington et al. 2016)

Lepidodendron and Isoetes rootlets branch dichotomously, narrowing in a stepwise manner. A is a diagram of a rootlet with 4 levels of branching. B and C show rootlets of Isoetes and Lepidodendron (scale bars are 5 mm). Hetherington et al. 2015, Fig. 1 in part.

A final question: Is Prairie Quillwort gone from South Dakota? Has it suffered its own extinction? Maybe so. Skilled botanists have searched for it with no luck. But perhaps they were limiting themselves, looking only in "roadside waterholes" and such. Of great interest to me is its occurrence nearby in Minnesota where it's a state Endangered species. It's distribution there is quite limited—rainwater and seepage pools in quartzite rock outcrops, in the southwest corner of the state.

MWI photo.

This rock—Sioux quartzite—also crops out in the southeast corner of South Dakota. I visited several locations a few years ago, and am tempted to go back now that I have a such a vivid search image for Prairie Quillwort in my head!

Sign at Palisades State Park, SD. Pink marks exposures of Sioux Quartzite in southwest MN and southeast SD.

See any habitat?

Notes

Selaginella densa—moss, fern, fern ally, or none of the above? Coin is 19 mm across.

This month the South Dakota fern series features another oddity—a spikemoss, genus Selaginella. It's even more unusual than last month's Water Clover, for while water clovers are ferns, spikemosses are not, at least not anymore. So where in the greater scheme of plant classification do they belong?

The Prairie or Dense Spikemoss, Selaginella densa, is the more common of South Dakota's two spikemosses. It occurs in the Black Hills and scattered across the west half of the state. If you live in or have wandered across the Great Plains or Rocky Mountains, you may have seen it, for it grows on a wide range of sites—prairies, alpine meadows, dry rocky slopes, rock crevices, sandstone, quartzite or granite rock, and dry gravelly, clayey or sandy soil (Flora North America). Or maybe you overlooked it, as I used to do. After all, it looks very much like a moss (1).

Spikemosses were first classified—given a name and assigned to a plant group—by the great Swedish botanist Carl Linnaeus, founder of today's system of naming organisms. In his Species plantarum (1754) he placed them in the CRYPTOGAMIA MUSCI section—the mosses. That was a big mistake, but at the time it was a reasonable decision. Like mosses, Selaginella produces spores (2). But unlike mosses, it has vascular tissue—plumbing for transporting water and nutrients.