Foxfire is a kind of lichen that glows in the dark. It is also the name of a quarterly magazine and of the series of Doubleday books that have sold more than 4 million copies since the first volume in 1972.
Today, ''Foxfire'' is a Broadway-bound play with songs, starring Hume Cronyn, Jessica Tandy, and Keith Carradine. Thereby hangs a history.
The history began in 1966, when Eliot Wigginton, primed with two Cornell University degrees, arrived to teach English and geography at the 240-pupil Rabun Gap-Nacoochee School in Rabun County, Ga. ''I thought I was a big deal - a force to be reckoned with,'' he wrote in retrospect.
But when his ninth-graders greeted ''Silas Marner'' and ''Julius Caesar'' with paper airplanes and other expressions of boredom, Mr. Wigginton looked for a better way to gain their attention. About six weeks into the term, he opened class by asking: ''How would you like to throw away the text and start a magazine?''
They liked, and Foxfire was born. Its contents consisted of material gathered by the youngsters in conversations with their grandparents and neighbors. They learned about things like log-cabin building, mountain crafts, hunting, recipes, folkways, and customs. The research became the contents of Foxfire magazine, which the students published themselves.
In 1977, when Mr. Cronyn was seeking a brief stretch of material for Miss Tandy for their joint program, ''The Many Faces of Love.'' He wrote explaining the need to their friend, Susan Cooper, a prize-winning British journalist and author who now lives in Cambridge, Mass. Miss Cooper responded with some reflections by Aunt Arie Carpenter from the first Foxfire volume. The excerpt wasn't used, but it inspired Cronyn to suggest that he and Miss Cooper collaborate on a whole ''Foxfire'' program. Ultimately, he concluded that ''we had to be braver. We had to try to write a play.''
Then came the 1977-78 season and the Cronyns' success in D. L. Coburn's Pulitzer Prize-winning ''The Gin Game,'' which also won Miss Tandy her second Tony acting award. Throughout the Broadway run and subsequent tour, Cronyn and Miss Cooper continued their long-distance collaboration - incorporating Foxfire material into the plot they were fashioning. ''Foxfire'' premiered successfully in 1980 at the Stratford Festival of Canada, but, said Cronyn, ''it needed work.''
A 1981 production at the Tyrone Guthrie Theater in Minneapolis garnered new plaudits and popularity. However, the project went through ''three managements and four directors,'' plus attendant disappointments, before the turnaround that eventuated in the rehearsals now in progress under director David Trainer. ''Foxfire'' is scheduled to open at the Ethel Barrymore Theater on Nov. 10, after playing the Morris Mechanic Theatre in Baltimore (Sept. 20-Oct.9), and the Colonial Theater in Boston (Oct. 12-30).
Although Cronyn has written short stories and screenplays for Alfred Hitchcock, this will be his first bow as a playwright. He and Miss Tandy, who are about to celebrate their 40th wedding anniversary, will be appearing together on Broadway for the 11th time since they costarred in ''The Fourposter'' in 1951. ''Foxfire'' marks the theatrical debut of popular-music composer Jonathan Holtzman as well as Mr. Carradine's first Broadway starring role.
As for Wigginton and his Rabun Gap ninth-graders, Cronyn says that, after being reassured Rabun Gap wasn't going to be turned into a Broadway Dogpatch, ''they became our greatest fans and sternest critics.'' Some of the students saw the play in Minneapolis and returned home to make a two-hour tape of comments and observations.
In a ''Foxfire'' program note, Cronyn and Miss Cooper write: ''Its people and its story are fictitious, but the predicament they present belongs to any region , in any country, where the values of the past are in danger of being obliterated by the demands of the present.
''Hector and Anie Nations [Cronyn and Miss Tandy] . . . have the strengths and vulnerability of yesterday. Their son, Dillard, [Carradine] like the rest of us, is beset by the problems of today. What chance have they - and we - of controlling the shape of tomorrow?''