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The walls of Building 9 on The Ridges at Ohio University are cracked and peeling, revealingthick layers of paint and plaster that resemble the skinof a cave. Gar Rothwell walks toward the stairwell tothe basement, passing a sign that reads “Caution! Lead Paint.”

“You’ll be okay as long as you don’t lick the walls,” says Rothwell, a distinguished paleobotanist who on this warm day is sporting a short-sleeved shirt patterned with green ferns — one of his areas of study. Down the narrow staircase, he descends to the basement of the Victorian-era building, which once was among the state’s largest asylums for the mentally ill. As he enters the low-ceiling room, a musty odor fills the air. A thumbsized cockroach skitters across the concrete floor. Rothwell strolls through the passages unperturbed. It’s clear from the odd desk and chair that people — perhaps a graduate student fearless to solitude and bugs — sometimes work down here.

He stops in front of a door and unlocks it, revealing the treasures stored in this unlikely museum: One of the nation’s largest collections of plant fossils, including those that document some of the earliest green life on our planet. Rothwell opens metal lockers and narrow drawers stuffed with shards of ancient plant remains from digs around the country. Thick, stumpy hunks of rock — the likes of which Rothwell has discovered in his own back yard in rural Athens County — fill the basement. Their weight is too great to sit on the first floor. Near the back of another room, giant wooden crates hold piles of rocks about 4 feet high. A child would itch to crawl on top for a better look at the prize. So would a scientist who has turned a fascination from youth into a successful research career.

“Fossils are just as interesting to us,” Rothwell later says with a smile, “as any other 8-year-old kid.”

The fossils in the Ohio University Paleobotanical Herbarium, the third largest collection in the United States after the Smithsonian Institution and the Field Museum in Chicago, aren’t just neat to look at. They offer scientists such as Rothwell clues to the origins of plant life on our planet and how they evolved over time. The herbarium boasts the world’s largest collection of “coal balls,” fist-sized hunks of calcium carbonate formed in the ancient oceans that show the first evidence for land plants, seed plants, conifers, ferns, and more. In the last few years, the Ohio University paleobotanists have bolstered the collection with evidence of what may have been the first plants to establish life on land. The new plant fossil specimens can aid researchers in better reconstructing a time line of life on Earth.

Natural History

About 4 billion years ago, the oceans first came alive with microscopic bits of algae. Almost 2.5 billion years after that, primitive animals such as cephalopods, ancestors to the modernsquid, swam the seas. It wasn’t until sometime later — about430 million years ago — that early plant life emerged from thewater and began to populate the land. Humans, of course, arerelative newcomers. The flowering plants we tend, the leafy treesthat offer shelter and inspire poetry, pre-date us by hundreds ofmillions of years in the history of the planet.

Scientists still debate exactly when and how life first crept out of the salty waters of the seas and onto dry land. “It’s one of the most fundamental problems in plant evolution, the change from the water to the land,” says Rothwell, a professor and chair of environmental and plant biology at Ohio University. “What were the first communities like? How did the ecosystem change over time?”

Rothwell and fellow paleobotanists have spent their careers studying the origins and evolution of land plants such as conifers and ferns. Recently, they reported that they may have found new fossil evidence for plants that are at least 15 million years older than anything biologists have discovered to date. Impressions of this early green life may have been lurking under scientists’ noses for years. The trick, Rothwell says, was to stop searching for fossilized twigs, leaves, and seeds and to seek signs of life that didn’t look anything like the plants we know today.

“They were looking for the wrong thing — for a certain kind of fossil that wasn’t there,” says Rothwell. “We went looking for a certain kind of fossil that was there.”

A Rock And A Hard Place

The evidence of early life is saved in yesterday’s news. Unwrapping the stiff pages of the local newspaper, doctoral scholar Mihai Tomescu produces palm-size gray chunks of shale hammered from a rock formation in rural Virginia. He points to areas on the sample, unremarkable splotches of black to anyone not trained in the science of stones. Tomescu and Rothwell believe they are the fossilized remains of some of the earliest land plant life in the world. Their jagged shape suggests something organic, something that once lived. “The only other thing it could be is oxidation, but you wouldn’t have the well-defined edges and you wouldn’t see cracks like that,” Tomescu says.

The black splotches don’t look like anything that we would call a “land plant” today, which may be why many paleobotanists have overlooked these in the field. Paleobotany largely has been a descriptive science, and researchers have sought out specimens with identifiable plant remains — branches, leaves — for study, Tomescu notes. But the earliest land plants were probably more like today’s mosses and liverworts, small plants that live in damp environments on rocks, soil, and trees.

Before plants entered the picture, the only thing on land was soil, bacteria, and blue-green algae. At some point, the land underwent a dramatic transformation, becoming home to a complex world of organisms. Botanists aren’t exactly sure how this occurred, but sediment from 420 million to 460 million years ago shows evidence of a major transformation.

During that long-ago era, the world looked very different geologically: The land mass was one continent, surrounded by an expanse of ocean. Given its location at the time, Appalachia became a resting ground for sediment, and today the areas here — especially Ohio, Virginia, West Virginia, Pennsylvania — are some of the best places in the world to search for fossil evidence of land plants, says Rothwell, author of more than 180 journal articles and coauthor of Paleobotany and the Evolution of Plants, one ofthe most widely used textbooks in college botany classes.

Tomescu found the original samples with the telltale black marks on an expedition to Strasburg, Virginia, in 2001. Now, back in the laboratory, he tries to examine the specimens in more detail to learn about their physical structure. But the material is fairly brittle and fractured. Tomescu places small fragments under a scanning electron microscope to help reconstruct the surface features of the organism. He also bleaches fragments to better view the structure under a standard microscope. “It’s hard to see the cells because they’ve been so badly squashed,” Tomescu says. “Were these lichens, fungi? It’s hard to tell — even after all these procedures.”

But dating of the rocks that contain the fossils suggests one pertinent fact: The specimens are about 15 million years older than any land plants found previously. “People are able to very accurately predict (the age of) rocks — sometimes because of the fossils in them, such as invertebrate animals, that have changed enough over time,” Rothwell says.

The scientists have spotted the evidence in other scientists’ rock collections, too — now that they know what they’re seeking. They havepresented the resultsof the research,which is funded bythe National ScienceFoundation, at theannual meetings ofthe Botanical Societyof America andGeological Societyof America and theMid-ContinentPaleobotanicalColloquium. Other paleobotanists have been surprised by the find but are eagerfor more information about these early plants and theenvironment they lived in, Rothwell says. “It’s difficult,”Rothwell concedes, “because all of these things look similarafter being squashed for 400 million years. They do not giveup their secrets willingly.”

Tomescu, who graduates with a doctoral degree in June, is willing to put in the detective work. He’s traveled to Wisconsin to consult with an algae expert, compared notes with a researcher in Switzerland about lichens, and examined other collections in Boston.

“This is a hot topic, as people have tried to understand the origin of plants ever since evolution was understood,” says Tomescu, who has had a passion for geology and biology since his childhood in Romania. “I’m attracted to these big questions.”

Green Survivors

Another big question for scientists is how our planet’s past may offer clues to its future. Earth’s history has been marked by cycles of catastrophe: Shifts in the planet’s climate and chemistry have triggered massive changes on a global scale, Rothwell says. The best-known example is the rise of dinosaurs and their extinction in the Mesozoic era, which many scientists believe was caused by a meteorite striking Earth. At other points in history, 90 percent of all ocean life went extinct. Volcanoes made landscapestremble; continents broke apart and collided. Today,scientists fear that our introduction of new chemicals andsubstances into the environment will speed global warming.What might be our legacy?

“Life responds — often by dying,” Rothwell says of these major global changes. But life also can adapt — and even thrive — under adverse conditions. About 320 million years ago, Earth underwent a global climate shift. Glaciers in the southern hemisphere melted. Ocean patterns and rainfall changed, and the climate overall became drier, Rothwell says. This doesn’t sound like an optimal time for a land plant to thrive, but conifers — the cone-bearing evergreens such as pines and yews — adapted a way to do it, becoming some of the earliest plants to dominate the planet. The conifers were able to conserve water during dry times and live outside of wetlands.

Rothwell and fellow paleobotanist Gene Mapes also discovered that the trees employed a clever reproductive strategy to ensure survival during hard times. In the late 1980s, the researchers found fossils of intact conifer pollen cones that boasted the world’s oldest seeds with embryos. This was significant because most fossils are compressive remains, which only show the shape of the fossilized plant, says Mapes, director of Ohio University’s environmental studies program and an adjunct professor in environmental and plant biology and in biological sciences. One specimen now in the university’s fossil collection shows a wispy branch with short, pointy leaves; another details the overall anatomy of a pollen cone, suggesting more about the ecology and evolution of the plant. The dark, oblong shapes in the rocks of this collection clearly show leafy branches, pollen, and pollen sacs, as well as other details, according to the scientists.

Though the seeds had developed into embryos, the conifer had never released them. This was the first evidence of plants developing a biological mechanism to reserve their seeds during bad ecological times. They strategically waited for optimal conditions to disperse their seedlings, argued the scientists, who published their results in the journal Nature. After pollination, conifers may have tucked their seeds inward for more successful reproduction, Mapes says. “It’s groundbreaking work, really, because they have collections of conifers where they can reconstruct the whole plant,” says Ruth Stockey, a professor of biological sciences at the University of Alberta in Canada who has collaborated with Rothwell and Mapes on other paleobotany research. Though biologists once believed that all ancient conifers were related, and most likely relatives of today’s trees, the Ohio University research has shown a more complicated picture of ancient land plants. Ancient conifers may not be related to their modern counterparts after all, the studies suggest. And some fossils that appeared to be conifers actually were conifer-like plants.

It’s hard to imagine the barren landscape conifers and those similar plants once faced. Today, most of the Earth’s surface is covered in vegetation, except for extreme places such as deserts and acid mine drainage pits, Rothwell notes. The most aggressive modern land plants — invasive organisms such as Japanese honeysuckle and kudzu — are displacing other plants. When conifers arrived, they had no competition. Conifers dominated the Earth for more than 250 million years, Rothwell says. Though flowering plants now prevail, conifers still thrive today in mountainous, dry, and boreal climates. In the grasslands of Montana, Idaho, and Wyoming, the only trees are Ponderosa pines. Theybeat the evolutionary odds, Rothwell notes. About 75 percentof the Earth’s land plants have gone extinct over time.

Rothwell and Mapes continue to investigate the early conifers, including whether their similarities can be attributed to genetics or environmental adaptations. The best evidence for these ancient trees comes from a dusty corner of southwest Kansas at a farm with a small limestone quarry. “It’s got to be one of the most monumentally unimpressive places you can imagine,” Rothwell says, noting that he and his colleagues often have worked there in 110-degree heat, 95 percent humidity, and no shade.

But the Hamilton, Kansas, site is a geological jackpot, as it provides a snapshot of life more than 300 million years ago, he says. Scientists believe this place once was an ancient estuary home to a rich range of life. Rothwell, Mapes, and Ohio University geologist Royal Mapes, who studies an ancient squidlike creature called the cephalopod, have found fossil evidence of plants, clams, snails, fish, pollen, spores, and microorganisms.

The search for early plant fossils doesn’t end in Kansas. The researchers have discovered that one of the best places to search for signs of early land life is — surprisingly — near the ocean. Plant debris once floated into the water and traveled far from shore, where it was nibbled on by ancient invertebrates such as cephalopods before finally settling at the bottom of the ocean and becoming fossilized. Specimens were well preserved becausethese deep marine environments had little or no oxygen, whichwould have degraded the plant material. Encapsulated in calciumcarbonate, these “coal balls” have washed up on beaches inmodern times. In the past 25 years, Mapes and her colleagueshave found more than 40,000 well-preserved land plants frommid-continent North America in open marine environments.This year, the scientists have planned expeditions with geologiststo Vancouver, Canada, and Papua New Guinea to beach combfor these unique specimens, which are small, compact, and eitherround or cylindrical in shape. Because the Earth has changed somuch geologically over time, the researchers have found coalballs at nonmarine sites as well: rock quarries, stream beds, andeven a motorcycle dirt track, where balls were churned up by thetires of the bikes, Rothwell says.

Treasure Trove

Ohio University’s paleobotanists have collected plant fossils from locations ranging from Virginia and Kansas to the tropics of the Pacific. Today, these and other specimens can be found in the same ZIP code. Established in 1984 as a recognized repository for fossil plants, the Ohio University Paleobotanical Herbarium now includes about 250,000 specimens from the Midwestern and south central United States and western North America, as well as smaller collections from Europe, Japan, India, Australia, and Antarctica.

The collection not only represents a treasure trove of fossils for decades of future Ohio University research, but a resource for scientists around the country. About 10 researchers from institutions such as the University of Alberta and Arizona State University visit Ohio University each year to use the collections in research, Rothwell says.

Weaving through the musty low-ceiling rooms that are home to this collection, it’s easy to wonder if or when these fossils might get a more visible display for amateur fossil enthusiasts, school kids, and other curious folks. While the university explored the idea, Rothwell says, developing a museum for collection would require substantial funding and the manpower to put it together. Funding agencies tend to grant money existing collections rather than new facilities, he notes.

And there’s also the issue of priorities. Rothwell and his colleagues are scientists at heart — not curators, he points With thousands of specimens filling the rooms of the basement of Building 9, it’s clear that there is plenty to discover right here in the herbarium. And with so many questions about the origin and evolution of plant life still to answer, the science of the collection will keep them busy for years.

For more information about the Department of Environmental and Plant Biology,
visit the Web at http://www.plantbio.ohiou.edu/.