If you like to watch grass grow, you would have loved the opening yesterday of the Senate select committee’s hearings on the Watergate and related campaign misdeeds.

Unhurried in the presence of network television cameras or the certain knowledge that America was missing its soap operas, Sen. Sam J. Ervin Jr. (D-N.C.) and his six Senate colleagues spent the first day resolutely making a single point.

That point, persuasively drummed and droned home in five hours of mostly colorless and snail’s-pace testimony from four secondary witnesses, is that the investigation doesn’t intend to sacrifice thoroughness -- or, when necessary, even boredom -- for sensationalism, just to hold the TV audience.

The old Senate Caucus Room, which has heard about skullduggery as far back as Teapot Dome 50 years ago, was decked out in its brightest TV lights and an anticipatory overflow crowd when Ervin gaveled the hearing to order at one minute after 10 a.m.

The first spectators had arrived outside the old Senate Office Building nearly five hours earlier and were now seated or standing at the rear of the chamber. The first two arrivals, Tom Ling, 24, and Spencer Turnipseed, 25, students at Wesley Seminary, fell asleep, lost their places in line, but got in anyway.

Ling and Turnipseed both said they were there to hear more evidence than what they had read about Watergate, and most others around them agreed.

Some talked loftily about wanting “to see the system work,” but Ronald Coleman, a 27-year-old recent graduate of Catholic University and blind, said: “We’ve all got a little sadistic streak in us -- like stopping on the highway to watch an accident.”

But there was little in this first day of the Watergate hearings to please the sadistic, except perhaps the sight of hundreds sitting stolidly through yawn-inspiring recountings or oft-told tales of how the whole business began.

Samuel Dash, the Georgetown University law professor who is chief counsel, led the witnesses methodically through their stories, with the minority counsel, Fred Thompson, taking over, and then the senators.

To make the record, they asked many obvious questions for which answers long have been public knowledge, and as they did, you could almost hear television channels being switched from Maine to California. At the outset, Ervin pledged “full and open public testimoney,” and that was what he started serving up yesterday.

The first witness, Robert C. Odle Jr., 29, described himself as director of administration for the Committee for the Re-election of the President, which in the Nixon administration means he was the office manager.

Odle, baby-faced, with an accountant’s manner and a dull gray-striped suit he will still look right in when he’s 60, came more in sorrow than in anger or repentence.

He opened with a little speech about “a million volunteers across the country” and most of the 400 in the re-election committee headquarters who had nothing to do with Watergate, including himself.

He praised President Nixon, who he said “ultimately will be regarded as one of the greatest Presidents the country has ever known,” and then he proceeded to illustrate, perhaps unwittingly, how things could go wrong at the Committee for the Re-election of the President in spite of such dedication and majority honesty.

The re-election committee, he made clear, was a place where they watched the small print with a magnifying glass but sometimes didn’t know when a truck was running over them.

And when he first heard that James W. McCord, the campaign committee’s security chief, had been arrested in the Watergate break-in, at the Democratic National Committee headquarters, his first concern was that he’d have to find a replacement.

He suddenly realized that as “director of administration” he was now responsible for security at the Committee for the Re-election of the President, and there was always the danger of “retaliation.”

In a telephone conversation with the deputy campaign director, Jeb S. Magruder, who was in California, Odle said: “My God, I’ve got to find a new guy.” And Magruder replied: “You sure do.”

That same day -- June 17, 1972 -- when G. Gordon Liddy came by and asked him where a paper-shredding machine could be found and how it worked. Odle said he told him, and when he saw Liddy later carrying a big pile of papers to the shredding room, “it didn’t seem very unusual at that time.” He never shredded one document himself, Odle said flatly.

And then there was the question from Sen. Joseph M. Montoya (D-N.M.) about how McCord was paid. McCord was on the regular payroll, and Odle said he didn’t know anything about cash payments to him.

“The way the system was set up,” Odle said, “those things [payments to staff members] would go through me.” Apparently it never dawned on him that the way the system was set up, some payments went through him, and others didn’t.

Odle was also at his believing, trusting best when asked about a file given to him by another re-election committee aide to take home for safekeeping the weekend of the Watergate break-in. He never asked what was in the file and never looked, he testified. It turned out, the line of questioning indicated, that it was the file on the committee’s clandestine operations.

Odle hardly qualified as a star witness, but it was that kind of day. The other three witnesses were there to make record, and they did, methodically.

Bruce Kehrli, who was a lieutenant to deposed presidential chief of staff H. R. (Bob) Haldeman and now assists his successor, Gen. Alexander M. Haig Jr., efficiently outlined who did what on the White House staff. Then came two of the police officers who made the Watergate arrests, Sgt. Paul W. Leeper and Officer John Barrett -- Leeper crew-cutted with an incongruent Fu Manchu beard and mustache, Barrett long-haired and heavily bearded.

Leeper stood before charts and a floor plan of the Democratic National Committee and told how his police team “responded” from one room to another until Barrett came upon the culprits and started the Watergate scandal on its way.

Those who had waited hours to get into the Caucus Room, as well as those who stayed home from work to watch on television or lingered in front of the office set, didn’t have anything to gasp at, and little to laugh about. But those in the hearing room sat attentively throughout.

When Odle said of McCord at the outset that “his job was office security,” and when he said finance committee chairman Maurice H. Stans in budget meetings “certainly kept an eye on where the money went,” there were ripples of laughter. But the spectators took the hearing as Ervin and Co. served it up -- as serious, if initially tedious business.

In the face of the network TV cameras, and presumably an audience of millions for the first day, the seven senators did very little showboating, mugging or playing to the cameras.

Ervin, looking for all the world like a big, courtly br’er rabbit, his eyebrows working up and down as he talked, presided benignly and deferentially, and none of his colleagues tried to run away with it, as has happened often in televised hearings.

But yesterday was just the first step down a long road that should run well into the summer. Today, with McCord expected to testify, there may be more sparks, and more elbowing by the interrogators to get at him. And the chances are that much of America, sore about pre-empted soap operas or not, will again be watching.