It is tucked away in one of the shabbiest corners of UC Davis, inside a vintage campus building with faulty air conditioning, boxes piled to the ceiling and cabinets spilling out into the hallway. A storage room serves as the library. The air is permeated with the scent of mothballs used decades ago to preserve the treasures now hidden inside 1940s-era metal cabinets. Several years ago, this space was even considered condemned.

Judging by its appearance, visitors might never imagine that this little-known campus museum contains clues to solving major global ecological problems as well as mysteries in our own backyards. From Belize to Africa to Yolo County, evidence culled from these troves is helping scientists determine how to regenerate rain forests, trace climate change, identify invasive species and assist farmers in limiting the use of herbicides.

The more than 250,000 dried, preserved plant samples contained in the UC Davis Herbarium, in the bowels of Robbins Hall, soon may even help solve a murder in Eureka.

On more than one occasion, they have helped poison control centers save the lives of curious plant-eating toddlers. They have helped researchers document and classify endangered and extinct species, and verify plant lineage through DNA sequencing.

A broad array of interested visitors

A welcoming vase of wildflowers often sits at the herbarium sign-in table, where a book bears the signatures of all who have come to study the dried-plant resources.

Landscape designers. Fisheries biologists. Farmers. Wildlife managers. Pharmacologists. Geneticists. Vintners. Conservationists. Urban planners. Ethnobotanists. Backyard gardeners. Wildflower enthusiasts. Entomologists. Botany students. Social science students. Environmental policy students. The list seems endless.

Most visitors are from California, a state with more than 5,000 plant species. UC Davis' herbarium is a key laboratory for one of the most diverse landscapes in the world.

"Hundreds of people come to the herbarium each year with real scientific questions, and they get them answered," said plant geneticist Leslie Gottlieb, one of dozens of UC Davis scientists who rely on the herbarium resources to conduct their research.

"It is one of the greatest public services we provide in terms of its reach and impact."

It will also outlive most scientists using the herbarium today. The UC Davis plant collection is a resource that, if treated carefully, will last for centuries.

"We have these specimens for perpetuity; they are a reference for the future, with a useful lifetime of 100 years or more," Gottlieb said. "In contrast, the useful lifetime of most research papers produced on the campus is probably less than a decade."

Herbarium Director Ellen Dean describes the collection as "the center of the wheel of everything that's going on in plant science at UC Davis. It isn't everybody who gets excited about dead, dried plants, but when somebody suddenly needs to know something, we're here. We don't always get credit, but we were the resource."

Every day the mail brings more samples that need identification, in envelopes, boxes and cartons sent by people throughout California and even across the country. Dean and her longtime volunteer, Kate Mawdsley, become plant sleuths, prowling their stacks to find answers.

One afternoon, they were sorting through some samples of lupine, the common spiked, purple wildflower, sent in from the Asilomar conference facility in Monterey. It appeared to be a hybrid of a rare species, and Dean and Mawdsley set out to prove it was. Also needing identification were stomach contents from a dead cow, sent by the state Department of Food and Agriculture. And then there were some samples of endangered "Solano grass" to examine, accidentally mowed by someone not realizing their value. Also known as Crampton's tuctoria, this state- and federally-listed endangered species exists in just two small patches, one off Mace Boulevard in south Davis and another on private land near Jepson Prairie in Solano County. "If it disappears, our specimens will be the only proof that it ever existed," said Dean.

A labor of love

The field of taxonomy -- the practice of describing, naming and classifying species -- is labor intensive. Each plant is first identified by comparing characteristics like root structure, flower type, leaf and stem shape, and, in some cases, through its DNA. Specimens are carefully mounted on paper, tagged and then stored in the catacombs of cabinets that make up the main herbarium collection. Each specimen is archived according to its classification and the geographical area in which the sample was collected.

The hallway space was requisitioned for more cabinets when the herbarium added additional campus collections: a grass collection from the agronomy and range science department (critical to a national project to catalog grasses of the United States); an old viticulture herbarium that contains wine grape cultivars from the late 1880s to the present; and the environmental horticulture herbarium -- 30 years worth of plants desperately in need of restoration.

The herbarium survives with only 1.5 paid employees, Dean and Shepard, as well as part-time student help. The rest of the work is accomplished by volunteers like Mawdsley, a retired campus librarian whose casual interest in plants intensified during a two-week field expedition in 1989. "I took a field trip with the eminent plant geneticist Ledyard Stebbins, and he said that within 200 miles of Davis there is more ecological diversity than anywhere else in the United States. I was hooked."

Mawdsley has been helping the herbarium ever since her retirement a decade ago, putting in 10 to 15 hours a week. She serves as librarian, public service representative and resident docent. She also leads field trips conducted by the Davis Botanical Society -- a group of about 200 plant lovers organized by the herbarium.

One of Mawdsley's favorite projects has been preserving the natural history of the Stebbins Cold Canyon Reserve, a biologically diverse sliver of coastal range west of Winters that is part of the UC Davis Natural Reserve System. She revised and extended the plant list for the site. "California is a great place to study plants," Mawdsley said. "Once I knew how useful the herbarium was to so many people, I had a vested interest in doing what I could to see that it would survive and thrive. It's very rewarding to see the research value -- and also the value to amateurs -- of flattened flora."

Mawdsley and others lament the fact that the herbarium still battles insect infestations that regularly threaten to decimate the collections. The situation is aggravated by the taxing summer heat, which can't be well-controlled by the aging air conditioning system in the 40-year-old building. The humble herbarium space has never even had a permanent name.

Humble beginnings

The botany herbarium began as a small collection of weeds and poisonous plants on what was then the University Farm in 1922, the year W.W. Robbins founded the botany department. Renowned botanist Katherine Esau was hired to teach plant taxonomy in 1928 and added native plants from the Sacramento Valley and nearby coastal ranges to the collection.

The first true steward of the herbarium was John Tucker, a specialist in oak trees who essentially directed the herbarium as a volunteer from 1949 to 1986 -- in addition to his duties as a botany professor. Tucker did his first research in the 1940s while a student at UC Berkeley. He inherited a collection of some 9,400 specimens in wooden cases and built the herbarium rapidly through exchange programs. He created what is said to be the most extensive collections of the genus Quercus (oaks) in the world.

"John never received a penny for directing the herbarium. It wasn't until he quit that he was able to get a stipend for the next person," said environmental horticulturist Michael Barbour, one of a group of faculty who unilaterally decided to name the herbarium for Tucker and erected a carved wood sign above the door. "We thought, let's put a sign up and call it the John M. Tucker Herbarium. If we start referring to it that way, perhaps the name will stick."

Now 87, Tucker is still giving to the herbarium, having recently provided $250,000 to help fund new space for collections. He has donated another $200,000 to the UC Davis Arboretum, where he was director from 1972 to 1984.

Grady Webster assumed the directorship of the herbarium from Tucker. A botanist who has amassed specimens from Texas, Cuba, Mexico and Central America since the 1950s. Now 76 and an emeritus faculty member, Webster still spends most of his days in a corner of the herbarium, cataloging his life's work, flora from Ecuador's Maquipucuna region. This rain forest and cloud forest collection includes 200 species of orchids.

The arboretum, a living plant museum, is frequently confused with the herbarium. So is the UC Davis plant conservatory, which resides inside greenhouses on the north end of the campus. "It's sometimes harder to show the value of an herbarium versus the arboretum or botanical garden that people can visit, touch, see and experience firsthand," said Mawdsley. "It's a lot harder to get people excited about squashed, brown dead plants. But in many ways they are much more important."

June McCaskill was one of the first to prove the value of the herbarium to the world. Over nearly four decades as curator of the herbarium under John Tucker, McCaskill came to be known far and wide as "The Weed Lady of Davis." In the early 1970s, she was credited with helping solve the Juan Corona mass-murder case in Yuba County. By studying the different weeds in the graves of 25 slain farmworkers, she determined the order in which they'd been buried. Detectives still come to call, the most recent bringing plant samples they hope will solve a North Coast murder case.

McCaskill also helped eradicate poisonous weeds and saved the lives of many children, as well as countless cattle and horses, with her ability to identify nearly 90 percent of all weeds on sight.

McCaskill began working in the herbarium in 1953 and was the founder of the Davis Herbaria Society, now called the Davis Botanical Society. Before she retired in 1991, McCaskill had authored the Grower's Weed Identification Handbook, still in wide use today.

The name "UC Davis Herbar-ium" has been the primary nomenclature for the museum. For fund-raising purposes, the herbarium wants to officially change its name to the UC Davis Center for Plant Diversity but is still looking for a $1 million donor to name the new center and allow the collection to move to more spacious, climate-controlled campus accommodations. Funds are also being raised to name a plant identification laboratory for June McCaskill, who died in 2001. Additional support will also allow the plants to be photographed and the images made available on the Web. And thanks to a $350,000 grant from the National Science Foundation, the collection will have an improved storage system. "Grants for equipment of this nature are very hard to get, but it is a sign of how important the nation thinks these collections are," Director Dean said.

An invaluable research resource

Molecular botanist Gottlieb is one of many scientists now using the herbarium as a genetic library, extracting DNA from the specimens in order to track the codes for thousands of species in his specialty: wild native plants of California. "Preservation of the dried plants is vital to our work," Gottlieb said. "It is fundamental to understanding the origins of plant species, and preservation of my specimens tells future scientists exactly what I studied."

Gottlieb also used the museum as a repository for more than 8,000 loan specimens he borrowed from herbaria nationwide that he used to prepare taxonomic treatments for the Flora of North America project, a 30-volume series describing every plant north of Mexico.

Gottlieb classified the large Asteraceae family, which includes sunflowers, daisies, artichokes and lettuce. "Using herbarium specimens, we can study the variability of plants growing in nature, where they grow and how they are related." Gottlieb's project even turned up a previously unrecognized species of Stephanomeria, which he called fluminea, growing between granite cobbles near Grand Teton National Park.

McCaskill's groundbreaking book is now being superseded by Weeds of California, due to be published in the spring of 2005, that will contain 3,000 photographs of 725 weed species most commonly found in the state. "More than 80 percent of our weeds are not native to California, and they can cause serious problems," said the book's co-author, Joe DiTomaso, a weed scientist with UC's Agriculture and Natural Resources program. "You can't be effective in advising anyone about weeds without the herbarium," DiTomaso said. "Farmers need to see what weeds look like in the seed and flowering stages, so they can make decisions about control early on. Hospital emergency rooms need to be able to quickly identify the plants to know what a child has eaten."

Barbour has also extensively used the museum for his work documenting native California species for major projects in the Lake Tahoe basin and vernal pool regions of the Sacramento and San Joaquin valleys. "Vernal pools contain highly variable species that are good indicators of ecological health," Barbour said. "They can tell us about hydrology and what we might need to do for conservation. How much water do they need? And if they disappear from one pool, what does that mean?

"The landscape that we look at in California isn't static," Barbour said. "It might look as if oaks and other vegetation have always been there. But in fact it is constantly changing. The herbarium is the place that will document these changes."

So far in California, 29 plant species are currently known to have gone extinct. "We have also had some population 'wink-outs,' where they are gone and then somehow come back," Barbour said.

Benefiting the world

The herbarium's benefits have stretched far beyond Yolo County and even California.

Plant ecologist Marcel Rejmánek is trying to save Central American rain forests and find ways to help regenerate tropical trees in Belize and Costa Rica. He took 700 herbarium samples collected by his student Steven Brewer, Grady Webster and himself, created color copies, laminated them to protect them from humidity and created a mini-herbarium in Belize where none had existed before.

"We are also simply creating an inventory. No one had ever made an inventory of the Mayan mountains in Belize," said Rejmánek.

Rejmánek's work is also likely to influence hunting policy in Central American forests. He has learned that a large rodent, the Central American agouti, is important to the forest's growth. In areas where the agouti population has been reduced through hunting, trees with large seeds don't grow back. But where healthy populations of agouti forage and bury seeds, the forests regenerate and flourish.

Another scientist, Jason Bradford, is working to predict global climate change by studying the cloud forests on the steep eastern slope of the Peruvian Andes -- an area that contains 15 percent of the world's biological diversity. Deforestation in the Amazon basin and rising sea temperatures may be changing centuries of stable weather patterns in the Andes, according to Bradford, who uses the herbarium specimens to track patterns. "They want to know if the parks will be able to preserve species even as the climate changes, and if not, then what are the options?" Bradford said.

"People are totally dependent on plant diversity for the food we eat, the fiber we use, the way our air and water is cleansed," he said. "The UC Davis herbarium and herbaria everywhere are the places that tell us what we might be losing and what the cost might be of losing something that is irreplaceable."