FORMER DEMOCRATIC Rep. Emanuel Celler of New York served in the House for 49 years and 10 months, four months short of the all-time record. He is 90 now, a widower living in Brooklyn and working at his law offices on Park Avenue.

Recently he was found behind his desk, poised to light a long cigar, impeccably attired, somewhat hard of hearing and as impish as ever.

"I still have all my marbles," he said. "But I still have qualms . . . I often repeat this story: the three qualms of old age. The first is lapse of memory. And . . . really . . . I can't remember the other two."

Reading from notes prepared the night before on the 10 presidents he has known, Celler recalled one visit to Calvin Coolidge. "And he said, 'Do you smoke, congressman?' I said, 'Yes.' So he opened the drawer to his right, and there's a box of cigars.

"He carefully opens the box . . . takes out a cigar, closes the cigar box, slams the door, bites off the end of the cigar, lights the cigar. Then he says [to an aide] 'Jim, over there on the shelf is a box of White Owls. Give the congressman one.'"

As a New Dealer, Celler admired most of what Franklin D. Roosevelt did, particularly in fighting the Depression. But, he said, "FDR did not exert himself to rescue Jews fleeing Hitler's cruelty. He was fearful of the appellation 'Jew Deal' . . . afraid [that his enemies] would accuse him of being partial to Jews."

Celler said he had begged Roosevelt to induce Winston Churchill to ease the restrictions the British were then imposing on Jewish immigration to Palestine. "Out of insincerity he [FDR] vouchsafed that he had a secret arrangement with Churchill whereby unlimited Jews would go into Palestine. This was untrue, but he wanted to placate me with this outrageous ploy."

Meanwhile, the State Department was "rigidly" interpreting American immigration law, "especially the words 'likely to become a public charge,' so as to deny entry to thousands of German-Jewish refugees. I appealed to Roosevelt, but to no avail.

"Thousands of Jews perished because of the inactivity of [Undersecretary of State] Breckinridge Long, Secretary of State Cordell Hull and President Roosevelt. Yet I do not denigrate FDR. One must judge a character whole. He had his warts and pimples, but he also had his virtures as well as his failings." "Very Close" to LBJ

CELLER THEN characterized other White House tenants he has seen close up.

Harry S. Truman: "He was unpretenious, wise and courageous. . . he played the piano, but badly. . . "

Dwight D. Eisenhower: "He was quiet and elite, a great commander of heroic armies, an idol who unfortunately allowed himself in the beginning to be controlled by [White House aide] Sherman Adams," and later by Secretary of State John Foster Dulles.

John F. Kennedy: He "was resourceful, had hubris, highest integrity, and he was wise. He had charm and charisma. . . He was compassionate. One day upon his invitation I brought my daughter Judith, who was a victim of cerebral palsy and in a wheelchair, to the White House. The President spoke for a full hour with her in the Rose Garden.

"I think he listened too closely to his brother Robert, who had extreme views and who did some good how he used his power as long as he got convictions."

(On hearing that, Mary Dougherty, who had run Celler's local congressional district office and now works in the law firm, interrupted. "I think you're wrong," she said. Celler softened his appraisal: ". . . he used his power in a rather abrupt and unusual fashion.")

Lyndon B. Johnson: He and Celler were "very close," partly because both fought for civil rights. Once Celler went to LBJ to plead Israel's need for spare parts for fighter planes. The president ordered an aide to act at once. "He then leaned toward me," Celler recalled, "placed a hand on my knee, and said, 'I'm 100 percent for Israel.' And then he placed his other hand on my other knee and said, 'I'm 101 percent for Mannie.'"

Celler then resurrected the episode in which LBJ, released from a hospital after a gall bladder operation, pulled up his shirt to show his scar to news photographers. "That gesture gave him some sort of lift," the former congressman said. "But the comedian Alan King said, 'Suppose he had hemmorhoids?'"

Richard M. Nixon: "He could lie like an epitaph. . . He's like the mean guy who tells hiw wife he's impotent when she tells him she's pregnant."

Gerald R. Ford: "Affable, kind, likeable chap. A good golfer, not a good manager, not . . . great depth of intellect. A good congressman. His pardon of Nixon is unforgivable."

CELLER ALSO commented on a wide array of issues.

The Equal Rights Amendment: "As long as there is a fallopian tube, I will oppose it."

The Celler-Kefauver Act of 1950, which was intended to halt anticompetitive asset acquisitions:

"I think there ought to be an amendment. . . that provides that where a corporation does a business of $10 million it should be precluded from buying another corporation that does $1 million," because conglomerates "have become tremendously powerful. . . and they can do a lot of things which are just within the legal limits but which are immoral. . .

"White it is true we're a big nation, we have big business and big unions-and I'm not opposed to bigness-it's what bigness does which is detrimental. When they keep growing and growing, there must be a stop somewhere. There must be some brakes put on them."

But, he added, "I don't think" Democratic Rep. Peter W. Rodino Jr. of New Jersey, who succeeded Celler as chairman of the House Judiciary Committee, "thinks that way." Carter's "Raw. Deal"

WHAT ABOUT the House's current leadership, Speaker Thomas P. O'Neill and Majority Leader Jim Wright? "I think Tip O'Neill and Wright are doing a pretty good job, except that they are unable to control the situation themselves because of the fragmentation of these committees."

Will the president's power eventually reassert itself? "Yes, sir. . . I think the president will prevail. . . He's learning his lessons every day. . .

"Carter is in sort of a funk. . . It's not unusual for presidents. . . to incur the ire and irony of criticism during their first year or two years. . . But after that, people get acquainted with the abilities of these incumbents, and conditions change. And I think the situation will be the same with Carter. . .

"People are now cranky-that's good word, I think-because of Nixon, because of Watergate, because of the national scandals. And they're taking it out on Carter. . .

"He has been receiving rather a raw deal. . . the pundits and some of the columnists [he named Anthony Lewis, Evans and Novak, William F. Buckley Jr. and "some of the special writers in Newsweek and Time"] look upon him as a simpleton, which is outrageously false. He has his pimples and warts of character. . . But by and large I am convinced that underlying there is a spirit of integrity. There is perseverance, there's undoubted courage. And I think there is an underlying strata of intelligence.

"All of which will come to the fore in due course. And he will come into his own. He will be renominated by the Democratic Party. There's no Republican on the horizon who could beat him. And he'll be re-elected. . .

"Now, I say he has courage. He's taken on labor. He's taken on the Congress. . .

"The President has shown that he is master of the situation in a number of respects; in some respects, he's not the master. But he has won out on Panama. He won out on the question of the arms embargo to Turkey. He won on the question of refusal to invoke sanctions against Rhodesia. He won on the question of arms to Saudi Arabia.

"Those are the victories for which the columnists fail to give him credit. They castigate him constantly, and I don't think it's fair. They exaggerate his faults, and they minimize his virtues. . . They're very casutic, very intolerant, and very short-sighted. They remind me too often of bed-wetters."