They gave Cecil and Ida Green a sit-down dinner for 180 the other night.

There was a string quartet, and some speeches, and a handsome silver tray with 30 names engraved on it: the names of universities, hospitals, museums and scientific institutions from here to Australia, all of them touched one way or another by the Greens' wand.

In fact, you almost had to be a university president just to get into the part, staged by the Massachusetts Institute of Technology at the National Academy of Science here.

Nobody knows exactly how much the Greens have given away. They refuse to tell. So far, it is something like: 15 major university or hospital buildings; 20 fully endowed professorships; an ocean-going research vessel, the Ida Green; an endowed master teaching chair held by a first grade teacher; fellowships to encourage women in science and engineering; an educational TV system; a global network of earthquake detectors . . .

The MIT Earth Sciences Building, a 20-story tower by I.M. Pei, alone is so huge that the couple gave a separate endowment for daily coffee breaks so the staff could see one another.

Someone said Thursday night that their gifts have directly affected 200,000 students and a million alumni around the world.

So who are Cecil and Ida Green? When you say they helped found Texas Instruments Inc., you haven't answered the question. A lot of rich executives give out money every day. What is it about the Greens that draws this glittering crowd from Vancouver and Oxford and Sydney, Australia, just for a dinner?

"The Greens are pollinators," said Jerome B. Wiesner, president of MIT. "They spend their time buzzing about, cross-fertilizing . . ." He had the dozen or so Cecil and Ida Green professors in the audience stand up, people representing a variety of disciplines, from oceanography to elementary school teaching.

"One can make a difference - and they have," said Frank Press, the presidential science adviser. "They've made the world a little wiser and better place in which to live . . . They get people together."

"They are two of the greatest patrons this country has ever known," said Allan Shivers, former governor of Texas and now chairman of the University of Texas system's board of regents. "They are generous, also thoughtful and enlightened . . ."

Perhaps the best answer has nothing to do with words. It's something in their faces.

He is 78, she's 75, and they came up the hard way, meeting in 1923 at General Electric in Schenectady, N.Y., where he was working on his MIT master's theads and she was a file clerk. It was the era of Steinmetz and Langmuir, and the couple married and worked there for three years before moving to the newly formed Raytheon firm in Cambridge.

For the next 15 years they drove back and forth across the country: to Vancouver, to Boston, to Palo Alto (where Green worked under the driven genius Charles V. Litton), to Dallas, back to Palo Alto, to Newark, and then Texas again. They crossed five times in their open car. More than once, they slept on a pull-down bed, ate off an orange crate, made do with $15 a month.

Basically an electrical engineer, Green in 1930 joined a new enterprise, Geophysical Service Inc. of Dallas, exploring for oil. By 1945 - to cover a lot of ground fast - the firm's research and development department, dealing with electronic means of detection, had grown so large that it dominated the whole operation.

In 1950 it was made the parent company, Texas Instruments, with GSI the geoghysical subsidiary. Riding the electronics boom, TI soon became a billion-dollar glamor industry. Green and his co-founders found themselves multimillionaires.

Childless, the Greens decided to devote their wealth to education and communication on the one hand and medicine and health on the other. The perfect alumni, they gave to all the institutions that they had passed through, including MIT and Southern Methodist University, where Ida Green completed her studies in sociology and industrial psychology.

Earth sciences dominate the lists of their donations, many of which went unpublicized by their fervest wish, but it should be noted that poet Reed Whittemore was one of their professors, and journalist Ben Bagdikian, and nursing dean Madeleine Leininger, and psychologist David Elkind, and composer Gian-Carlo Menotti, and writer Isaac B. Singer, three years before his Nobel prize. And pages of others.

Then there is Project IDA (International Deployment of Accelerometers), which studies world-wide effects of earth oscillations in hopes of learning more about earthquakes, deep-sea tides and the very structure of the planet. The project calls for 20 stations from Russia to Rarotonga, locally staffed and feeding data to a central bank at San Diego.

"We are very fortunate," said Ida Green, as she accepted the standing evation in the academy's dymaxion auditorium. "Many people work very hard and do not get the rewards . . . This is the crowning glory of our lives."

The pleasure of the tribute, said Cecil Green, "will last the rest of our lives, even if we live to be 100 years old. It's not so very far away at that."

He thanked the inevitable ad hoc committee which got up the party. He thanked his parents. He thanked "dear Ida." A shy man, he doesn't like to be interviewed because it just starts a new flood of begging letters.

(Even in the reception line, people tried to get him aside to mention this or that or the other pressing need at this or that or the other institution.)

After the speeches, videotapes were shown of old friends who couldn't make it to Washington. They were short appearances, a few comments and a smile. And nobody talked about the big things, the great buildings, the Calder stakiles, the new Green College at Oxford.

What they talked about was the early days, when TI was nothing but a one-story brick building out behind the Dallas airport, and as the Greens sat there watching, they squirmed just a bit, uncomfortable with all this applause.