Delicately, oh so delicately, the pretty teeth of Mrs. Gladstone Williams (never, ever Helene) nip into a tender artichoke leaf. They hit gently, at a spot precisely halfway down, scraping the meat from teeth to tongue for an elegant nibble.

An elegant but rather meager nibble. No matter. This is art, not lunch.

"Artichokes make the table look so pretty, don't you think?" asks Mrs. Williams sweetly. Her students, who eye this nibble with absorption, say but oh yes, certainly. Some scribble in notebooks. "The artichoke -- nip midleaf and nibble slowly" perhaps?

This vegetable-eating lesson occurs in a cozy, 22-room townhouse stuffed with chandeliers and enameled eggs on R Street, the site of class No. 2 in Executive Protocol. On this night and three others, Mrs. Williams leads her slightly frightened students through the complexities of artichokes, calling cards, seven-course dinners, servant training, tea pouring and oh dear, even the inevitable faux pas.

They will learn, for $100, to say "dinner jacket," not "tux." "A man who calls what he wears a 'tux' is not accustomed to wearing one," Mrs. Williams says pointedly.) They will also learn to avoid mashing the pea ("Kind of messy, don't you think?"), where to seat the Irish ambassador, and how to say hello to Jimmy Carter.

And what to do, good heavens, if a meat slice can't be wrestled from the roast -- a dinner diaster usually the fault of some still-attached tendon or other anatomical atrocity. The solution: Let the waiter do it. "Don't struggle," advises Mrs. Williams. "Otherwise, it'll end up in your lap." Horrors.

But back to the artichoke. Now it is naked, with leaves lying tooth-scraped around its base. Mrs. Williams is about to demonstrate the attack, with grace, on the delectable heart.

"First, let me show you what you wouldn't eat," she says, pointing with her knife. "Never all these nasty little spines." Never.

Behind her is a giant diagram of your average American artichoke, and behind that is a marble fireplace, a gilt-edged mirror, and shelves and shelves of books. George Washington, in oil, watches from a wall. Did he ever need to know this stuff?

Irrelevant. A good many of us, Mrs. Williams believes, certainly need to know it now. And so she slices diagnally into the base of the artichoke, cuts the gray meat into neat little pieces, then passes them graciously, with toothpicks and napkins (paper -- acceptable at lunch) to the rest of the class.

And now, a mass nibble. The elegance will come later.

"It takes a long time to eat," smiles Mrs. Williams, "which gives the help enough time to get the second course on the table. A wonderful food." Bygones & Blue Jeans

Mrs. Williams, who says caaaaviar for caviar and saumon for salmon, has taught her protocol course from the days of Camelot through the Vietnam War, past radical feminism, and now, into the inflation of the '70s. Through it all, her twice-a-year course has barely changed.

But then, says Mrs. Williams, neither have good manners. And neither has protocol in a city where whom you seat next to the visiting prime minister's wife is still as important as, say, who plays first base in Cincinnati. "I just felt there was a need for this sort of thing -- in Washington, especially," she says.

Others, however, regard Mrs. Williams as a charming anachronism. "She teaches the etiquette of days gone by," says Pauline Innis, co-author of the book "Protocol," which was published last year. "but her point of view is that we have to keep up some standards, so that's a good thing."

If Mrs. Williams' students question the worth of learning to eat an artichoke or the 1979 worth of calling cards, it's not apparent in the enrollment. She has taught hundreds, from 50 states and almost 60 countries. Included are congressmen, diplomats, Lynda Bird Robb and the late Marvella Bayh.

"I don't know if she's with the current times," says a recent student who was enamored of the elegant old house and chatty anecdotes, "but overall, it was a great experience in my life."

"It gave me a general feeling of confidence in situations I hadn't been exposed to before," says a former congressman who took the course.

"It taught us about life in this country," says an ambassador's wife.

All applicants, be they Army chiefs of staff or diplomats' wives, must be scrutinized in an interview before admission. This is to insure that they have a professional or personal need for the course, as well as some base level of etiquette proficiency. A solid handshake helps; a clammy, fishlike one hurts. Wearing blue jeans to the interview is sure to eliminate you.

That's because Mrs. Williams probably hasn't come within a pant's length of them in her 50- or 60-odd years. (Asking her age during the interview will certainly eliminate you.)

Instead, she wears yards of a rustling black sari, pinned at the hip with a fat, gold medallion. Her hair is raven, her face white and smooth. The nails, flaming red, finger her pearls and the chain of her glasses. She was once very beautiful.

Now she seems a memento of another time, a time of sherry and calling cards, tea at 4 and dinner at 8. A time, long ago, of white gloves and fingerbowls, satin pillows and servants -- a dozen, preferably, of each.

She was born in Oxfordshire, England, then meticulously bred in Maryland by European parents who instructed her, among a great many other things, to speak only when spoken to. And to keep her hands in her lap at dinner. And to kiss her grandmother's hand. Carefully.

"I must say," she says, "I think we were all very polite children. But I don't think we had any fun."

In 1944, she married Gladstone Williams, the Washington bureau chief of both The Atlanta Constitution and the McClatchy papers in California. Between the two of them, they achieved the rank of mid-level socialites in a then-small town where restaurants, for what they were, closed at 8.

As she puts it: "We entertained quite a bit -- and were entertained in return."

There's this old yellow newspaper society clipping, for instance, dated Christmas 1958. "Hot buttered rum, conversation piece decorations and do-it-yourself entertainment," it begins, "were the delightful party fare served by Gladstone and Helene Williams last night at their annual Christmas Eve party . . ."

"She was not a Perle Mesta, by any means," says a women who has been active socially in Washington for 20 years. "but she was one of the hostesses of Washington."

During the '50s, Mrs. Williams taught literally thousands of young women in a finishing school she directed at Southeastern University. "Enormously popular," the Southeastern people remember today. In 1962, she began her protocol course as part of the school's noncredit continuing education program. In 1968, her husband died.

Over the years, the Williamses turned up at parties at the White House, from the Roosevelets to the Trumans to the Eisenhowers and Johnsons. But oh, Mrs. Williams feels so absolutely dreadful when you bring them up. "It just sounds like I'm name-dropping, you know," she says.

Which is a terrible, terrible faux pas. Nonetheless, it brings us to The Lessons, in which the faux pas and other introductory matters of etiquette are most properly examined. 'Firings' & the Faux Pas

Annie Belle, the maid whose name is really Annie Belle, opens the grand door with enough ceremony to make you say "Good evening" rather than "Hi." And may she take your coat?

There are Oriental rugs on the floors, oils on the walls, a fuchsia pin-cushion in the bathroom. And a pink jeweled hand mirror near some tiny pink soap balls that smell like your grandmother's dresser drawer.

Upstairs, Mrs. Williams begins extending her hand, solidly, to greet her students. "We shake hands like this," she whispers to one student who offers something similar to a clammy cod. And to a young woman in wool slacks: "Next time," she says quietly, "don't wear pants."

Never mind that this is 1979, a good decade beyond the pantsuit revolution. The pants end up more or less crawling, with a great deal of embarrassment, to one of a dozen gold wicker chairs that hold the dozen or so students. On another chair is the wife of the Venezuelan ambassador to the OAS. Nearby are two women who do entertaining for accountants.

On other nights, students include a former congressman from Texas, an executive secretary at Comsat, the chief of protocol for the chief of staff of the Army, a White House fellow, a Georgetown international school student and an official from the Federal Railway Administration.

Their names are not for publication because Mrs. Williams, who also interviews reporters before they may write about her course, insists. Preservation of privacy, she says. For the same reason, she refuses to be photographed.

At precisely 6:30 p.m., the class begins. Mrs. Williams faces her students behind a small wooden desk and a briefcase of papers. Among the first few lessons this evening: One invites people "at" dinner, not "for."

"Only cannibals have people for dinner," she smiles. "You might remember it that way."

She then whizzes though an order of precedence chart that ranks officials from Jimmy Carter down to brigadier generals. When she gets to the Cabinet, she stops here and there to mention recent, er, changes. No one has been fired, messily or otherwise; instead, a certain official "has decided to leave the government" and another "has been replaced by" Patricia Harris.

Students next learn to serve chilled water, never water with ice cubes. And what to include in their "notepaper wardrobes." How to write regrets and thank yous. And finally, the faux pas lecture.

"You know," counsels Mrs. Williams, "I don't think there's a person alive who has never made a faux pas. The secret is never to make the same faux pas twice."

But here are a few she says you shouldn't make once:

Name-dropping. Turning over a glass of wine at dinner. Wiping silverware at the table. Serving the hostess first.

And too much honest criticism for friends in plays and recitals. (Especially if the performance was not the best.) "They really don't want to know the truth," says Mrs. Williams.

But how do you answer "So what did you think?" without lying? Two suggestions: "I'm glad I had the opportunity to hear you" or "You're incredible."

And now, the rich smell of brewing coffee drifts from a kitchen tucked discreetly away somewhere.

The wonderful smell reaches the room of students, warm and softly lit. It has become a quiet refuge for daydreams of turn-of-the-century parties, of women in silk, of men in mustaches, of butlers who bowed. And tonight, even though it's just coffee and cookies, the silver service and lace doilies nurture and daydream. The former congressman sips his coffee and becomes a dashing rogue; the ambassador's wife evolves into a mysterious foreign beauty.

But then a nervous student brings the real world crashing back. He throws a cautionary glance around, then leans over his empty coffee cup and whispers. "Do you know how we go about asking for seconds?"

After the coffee break comes a lecture about how on earth to handle servants.

"Never, ever," begins Mrs. Williams, "scold or criticize a servant in front of anyone. And that's even if it's something you think is a disaster at that moment." Her students scribble away. Tea & Turkish Towels

"Now before the holidays," says Mrs. Williams, "I would like each of you who are not in the habit of it to give a little tea."

She is demonstrating the pouring of the tea, the serving of the bread and butter, the dropping of one lump or two. In between she relates tea party anecdotes and general party hints.

Here's one: When new in town, drink tea instead of gin.

"Somehow, says Mrs. Williams, "when you have two hands occupied, you don't look as lonely as you do when you have a drink in one hand and the other just hanging there. A cup of tea can be a wonderful friend."

A student has a question."Are paper napkins acceptable at tea?" she asks.

"At this sort of function," says Mrs. Williams, "yes." More scribbling.

She begins to rise from her spot behind the tea. "Oh," she says. "I almost forgot. You must have a tea strainer to use when you're pouring it in the cup. Otherwise, it'll not be very . . . (here she pauses to search for a polite word) . . . ah, appetizing." She smiles sweetly.

And then it's downstairs for one of Executive Protocol's highlights. Which is: How to Serve a Sit-Down Dinner for Six Without a Servant.

How, how? Well, it's a secret. Mrs. Williams refuses to divulge it for publication. It's a method she has devised herself.

It takes a good hour to describe, so in between the instruction, Mrs. Williams amuses her students with more stories of the old days.

There once was "a marvelous older woman," she begins. "She told fortunes and everyone called her Gypsy." She had no help, but plenty of gumption, so when she held a dinner party, she got through in smoothly.

So smoothly, in fact, that when the dinner guests passed their used plates to Gypsy, she would pass them graciously under the table. They disappeared soundlessly and miraculously.

Well, Mrs. Williams, who was a guest, watched this for some time until she could absolutely stand it no longer. Finally, she asked Gypsy what was happening.

The answer: A washtub, lined with Turkish towels and full of hot soapy water, sat at Gypsy's feet. It served as a quiet, on-the-spot dishwasher. No need for servants.

"I thought that was the most original thing," says Mrs. Williams. "I think one can do anything if one does it with an air." Fingerbowls & Feuds

"You don't chomp into an apple," says Mrs. Williams, who probably doesn't even do so in the privacy of her own home. "And you don't peel a banana. You must learn to use a knife and fork."

This is the beginning of the formal dinner lecture, a lecture that comes with tips on how to handle oysters, servants and feuding guests.

On the oysters: "Some people can't look an oyster in the eye. Now if you can't you can at least take an oyster fork and just play with it. Pretend you're eating."

On servants: "A woman I knew had 17 servants. Now you think it would be wonderful to have 17 servants. But it wasn't. It was a terrible headache. She had to have two dinners in the servants' quarters, because the butler wouldn't eat with the scullery maid.

On feuding guests: Be careful. And if there's really a feud, invite one or the other, but not both. "It's important that you don't spoil a dinner for someone else," says Mrs. Williams.

Then there's a lesson on turning the tables, which means that when a hostess stops talking to the dinner guest on her right and switches to the one on the left, everyone must follow suit. This rule comes with a story about the mean old Washington dowager who used to terrorize unsuspecting debutantes.

"She would invite the girl, after she'd made her debut, and sit her between a doddering old man and a charming young man," Mrs. Williams relates. The dowager would wait to turn the tables until she saw the debutante deeply engrossed with the charming young man. With that, she'd send the butler over to remind the girl of the neglected senior citizen.

"Of course, the debutante never forgot that," says Mrs. Williams. "She learned her lesson."

And now, a few odds and ends.

Doilies, for instance. Don't eat them by mistake. "I have a friend who swears she ate a paper doily once," giggles Mrs. Williams. "But I don't believe her."

Fingerbowls. "You don't take a bath," says Mrs. Williams. "you just do it as unobtrusively as possible."

Limousines. Always, the woman sits on her host's right. "But if it has a lump in the floor, like most cars do, just slide over," she advises.

Hard-boiled eggs. "Wonderful blotters," she says, explaining that they can be served to guests just before they drive home. Alcohol absorbers. Grace & Grads

Suddenly, Mrs. Williams glances at her watch. "Oh, my," she says, "it's 10 o'clock." She looks out over her protocol students, who are now protocol graduates, with motherly pride.

"Remember," she says in closing, "only a lightbulb can go out every night and still be bright the next morning."

Her students close their notebooks, gather their belongings, and line up to bid Mrs. Williams goodbye. They shake hands, firm and sure. They smile graciously and chitchat with courage.

Downstairs, they collect their coats and say good evening to Annie Belle. And then, off they go into the darkness of R Street, ready to fend for themselves among the oysters and artichokes.