Spokesman for the team and co-principal investigator Brent Mishler, a University of California, Berkeley, professor, said the five-year study upsets conventional notions.

"They're going to have to rewrite the textbooks,"Mishler said of the groundbreaking synthesis of recent genetic discoveries and new, computer-based analysis.

No "green plant Eve" has been found, but scientists have discovered that a single evolutionary line of plants led to today's green plants. "They all had a common ancestor, an 'Eve' back in fresh water, maybe a billion years ago," Mishler said.

However, the plant with the oldest lineage known to humans was recently discovered in New Caledonia in the South Pacific in a search unrelated to the study.

"It's the amborella, a little shrubby tree with nondescript flowers, but it's the most primitive plant on the planet," Mishler said.

The species goes back more than 500 million years.

Finding it,Mishler said, was the equivalent of biologists discovering that the Coelacanth, the prehistoric fish species long thought to be extinct, still lives in at least two places.

The plant scientists presented their results Wednesday at the International Botanical Congress in St. Louis, a meeting of more than 5,000 experts from around the world.

The task force's voluminous research is expected to have far-reaching benefits to scientists researching new and better crops and for those looking for new medicines in the green plant kingdom.

Internet endeavor

The study -- coordinated from Berkeley -- involved 200 scientists from 12 countries linked by the Internet. Their effort provides the most detailed look ever at a group of living things on the planet.

Science students have long been taught there are two major groups of multi-celled life, plants and animals, and that both originated in the ocean. The study, dubbed "Deep Green" by botanists, shows there are five distinct groups, long separated by time and evolution, Mishler said.

The groups are green plants, red plants, brown plants, fungi and animals. In fact, fungi, including the mushrooms you eat, are more closely related to animals than they are to plants, he said.

DNA analysis shows that fungi branched off the tree of life long after green plants, the scientists said.

The study began in 1994 at a Berkeley conference, Mishler said. Plant scientists realized there had been numerous discoveries about green plants and their relationships to each other. But research was spotty and uncoordinated. This was a deliberate effort to examine green plants in great depth, Mishler said.

Green plants comprise about one-quarter to one-fifth of all living things, Mishler said, and they originated in fresh water, not the ocean.

Life originated in the ocean, but as rain began to fall and fresh water lakes appeared, life migrated to fresh water and green plants developed. From fresh water, green plants migrated to land and gradually evolved, learning how to reproduce and thrive.

Fresh water link

Some green plant species returned to fresh water and then to the sea, he said. For example, ulva, a black-green seaweed popularly known as sea lettuce, came back to the sea from fresh water. Brown and red plants mostly remained in the sea.

Among the earliest green plants to migrate from fresh water to land is the liverwort, a flat, liverish-looking plant that can still be found at the edges of streams and lakes. From the waters' edge, plants evolved, each type struggling to reproduce without the benefit of water.

In water, plants dumped their reproductive cells and they find each other, he said. "Everything swims."

There were ferns, the cicads, then flowering plants. Flowering plants use the wind and insects, sending out pollen -- male plants -- to find females.

Peter Hoch, curator at the Missouri Botanical Gardens and secretary general of the International Botanical Congress, said the study shows the exciting things that are going on in plant biology.

"Right now, this is the century of physics," Hoch said. "The next century is going to be the life sciences, molecular biology -- how organisms function."

David Brower, founder of Friends of the Earth, welcomed the study, saying it shows the importance of green plants. He recalled climbing down a glacier when he was a young man.

"When we reached the first green plant, it was so wonderful," he said. "It reminded me how special they are and how important."

The study was funded by grants from the U.S. Department of Agriculture, National Science Foundation and the Department of Energy. Next step for the group is to secure new funding,Mishler said. "It's not an easy process."