INSTEAD OF throwing spitballs and stink bombs at life, "Foxfire" finds wonder and marvels in living. Can such unfashionable drama weather Broadway's brassy blasts?

Little so confounds theater critics as life beyond the Hudson, the Potomac, the Susquehanna or the Charles. In "Foxfire" we have an old Appalachian woman who talks to her dead husband and hesitates to join their son in some far-off city. The trend setters assume she should be off like a shot for her crack at urbanity and escape from slicing up pigs on her front porch.

It hurts to admit it, but it has taken non-Americans to see the "Foxfire" books as inspiration for a play. Canadian-born Hume Cronyn joined forces with English novelist Susan Cooper to create a plausible, affirmative story as a framework for the mountain customs detailed in their collective reportage by Georgia schoolchildren. There is extraordinary beauty in the language and subtlety of relationships here.

The performances by Cronyn and Jessica Tandy climax the dozen plays they've been acting together since "The Fourposter" of 31 years back on through "The Gin Game." In "Foxfire," Tandy has a marvelous instant, wherein her 78-year-old character suddenly becomes a dancing teen-ager--as magical a moment as I've seen since Marilyn Miller played Peter Pan on 42nd Street in the '20s. And Cronyn's own mercurial flashes, regretful memories, are the most resourceful of a career that has gone from Hamlet to Hadrian VII.

A great deal of work has been done on "Foxfire" in the two months since its Baltimore run and, for that matter, its first version in Stratford, Ont., three summers ago.

"It's still the same play," says Cronyn, "and we've done the best we can, which should, of course, always be better but it's on on on on on and we made our deadline. It's also a darn sight better than when Baltimore saw it."

Now the question is: Will "Foxfire" catch on? I've a hunch that it will, for here is the philosophy and human dignity theatergoers have been missing.

When Alan Hewitt, of the Eisenhower-bound "Outrage," has leisure to look across the Kennedy Center's Hall of States, he'll have every reason to think he's living in a 46-year time warp, for at the Opera House will be "On Your Toes."

Not long out of Dartmouth, Hewitt hit it lucky, hired by Alfred Lunt and Lynn Fontanne for a company that would be with them for some years. In April 1936, Hewitt was with them at the 44th Street Shubert Theater in "Idiot's Delight." Just down the street at the Imperial was "On Your Toes," its billing boasting "choreography by George Balanchine." That's what it says for the revival of this Richard Rodgers musical to a book by Rodgers, Lorenz Hart and George Abbott.

The Kennedy Center is boasting that director Abbott also directed the original production. But Worthington "Tony" Miner was the original's director of record. He's still resident in 57th Street and has been too genteel to comment.

"Cymbeline" probably has not been seen here since the mid-19th century, when it played at Grover's, now the National. But Arena Stage is dusting off this treacherous Shakespeare, distinguished by having an alternate Act V by none other than Bernard Shaw, who called his "Cymbeline Refinished."

Only Oregon's Shakespeare Festival has had much American playing time for this British variation on Roman history, a play to which Samuel Johnson referred in his warning not to waste "criticism upon unresisting imbecility."