OSCAR WILDE'S witty dialogue is the only saving grace in the Boston Shakespeare Company's production of The Importance of Being Earnest. From Algernon Moncrief's description of the practice of "bunburrying" in the first scene to his statement in the last that "style, not sincerity, is the vital thing," all entertainment value comes from Wilde himself and not from the actors' plastic performances.

In this farce that mocks the English aristocratic culture of the 1890's, the central character Algernon (James Finnegan) has invented a sick younger brother, Bunburry, as an alibi for his many trips to the country. His friend, John Worthing (Henry Woronicz) has a similar stratagem: he is Ernest in town and Jack in the country. The drama focuses on the confusion engendered by these men's double identities when they meet their lovers-to-be--who both insist that their husbands be named Ernest.

Instead of drawing out the comic possibilities of this lovely scenario, the BSC actors tend to remain in pointed and stiff positions throughout the show, producing an artificial and amateurish effect--though they relax somewhat by the third act.

The only exception is Finnegan's convincing and zany portrayal of the gay, foppish Algernon, who devours cucumber sandwiches, bread and butter and muffins with dainty relish while seriously maintaining, "When I am in great trouble I refuse everything but food and drink." His candid approach makes the most of other similarly ridiculous lines.

Not as interesting or useful was Director Francis Cullinan's decision to cast a man, Bill Murphy, as the overbearing Lady Bracknell, Algernon's audacious and obnoxious aunt. If the aim was for some unusual dramatic effect, by the play's end this effect dissipates as Murphy becomes sufficiently convincing as a woman.

The farce reaches unbelievable extremes when Lady Bracknell terrorizes the obsequious John Worthing, who had hoped to marry her stylish daughter, Gwendolyn Fairfax (Jacqueline Riggs). As she grills him on his eligibility with questions like "Do you smoke?" his meager replies sound more and more unrealistic--"I'm afraid I do," he squeaks, and she answers dictatorially, "Good--a man should always have an occupation." Worthing says he has no parents and Bracknell responds, "To lose one parent may be regarded as a misfortune, to lose both is carelessness." In order to be considered for Miss Fairfax's husband he "must acquire some relations--at least one parent."

Dialogue like this provokes continuous laughter, but its empty and flat quality leaves little impression. Even if Cullinan wanted to stress Wilde's intent to write a superficial, light play, his emphasis on plasticity goes overboard.

Poor acting and stage directions are occasionally forgotten because of the extreme humor of the dialogue. But the actual women in The Importance of Being Earnest, Riggs and Worthing's "excessively pretty 18-year-old ward" Cecily Cardew (Melinda McNavy), act like two adolescents in love for the first time. After Cardew leaves Algernon, whom she has just met, she says deridingly that "a momentary separation from someone to whom one has just been introduced is almost unbearable." But their costumes are distasteful and their overly innocent manners crush Wilde's lines to triteness.

As the play hits rock bottom in Act H, the rest can only improve. In the more professional third act, the actors seemed to internalize their characters. Cecily and Gwendolyn, for example, argue seriously over trifles--lumps of sugar for their tea and cake--for the first time. Algernon declares with true earnestness about food, "One has to be serious about something in life to be amused." As the intricate plot unravels and the couples happily unite, the laughter subsides and Finnegan declares, "We have now realized the vital importance of being earnest." Maybe he has, but it would have helped had the BSC taken a more earnest stab at this drama. Wilde wrote a charming satire that, besides entertaining, might stimulate some thought on the excessive concern of the aristocratic class with manners and decorum. Random male-female substitution does not add anything to the effectiveness of this endeavor, and overacting never does.