In a similar case land in Peru cleared for tea crops immediately fell victim to the green menace, Rolla Tryon says. During World War 11, he adds, the ubiquitous bracken quickly sprang up in bomb craters throughout England.

The force

Ferns, however, are not a purely dark force, the Tryons say.

For oilmen, they mean hefty savings in exploration costs, since fern fossils will indicate at what depths oil is likely to be found. Fern spores, very common in fossil records, are used to date the age of rocks below the earth's surface. Since scientists know that rocks of a certain age-or depth-are more likely to contain oil than others, fern-spore dating can help them decide whether to drill deeper to find the oil.

While ferns are a valuable asset to oilmen, coal producers use them to judge the quality of coal deposits.

Since a higher grade coal will contain different fern spores than a lower grade coal, identifying the type of spore will indicate to coalmen the quality of their deposit.

Fern leaves are even used in come areas to preserve cheese, and certain ferns have a medicinal use as diuretics.

The Tryon, however have found a more domestic purpose for the scientifically vital fern. In the spring they scan the New England woodlands for fiddlehead ferns, which the couple then eat fresh in soups and salads or freeze to enjoy year round.

One of Alice Tryon's favorite recipes, she says, is "fiddlehead ferns in cheese sauce," a recipe which she recently donated to a cookbook. "Cooking with a Harvard Accent"- a collection of recipes donated by members of the Harvard community.

On a more scientific level, Rollo Tryon's work concentrates on classifying various branches of the plant. Recently he and his wife completed the most comprehensive classification and analysis of the plant ever assembled. Other botanists have heralded the project-six years in the making and roughly 900 pages long-a scientific masterpiece.

"The book allows scientists to have unified concepts about the plant. It's a model that people in field aspire to," says Director of the Harvard University Herberia Donald H. Pfister.

While Rollo Tryon concentrates on the plant's visible characteristics, his wife concentrates on the tiny fern spores, on which she is a renowned expert. "I work on the little parts, while he does the big stuff," she says.

"It's not just postage stamp collecting." Knoll says, adding that "their work has had a critical impact in basic biology."

The pair also leads their Biology 247 class on an annual "class trip" to Mexico to give aspiring botanists hands-on experience with some of the tropical fern species.

In fact, the Tryons have tracked ferns all over the world, boasting of more than 20 international treks through Europe, Latin America and Africa.