Public hearings, any self-respecting legislator will tell you, often become monotonous. Usually, by the time the 20th witness on the same bill comes forward, mind--and--sometimes bodies--begin to wander.

Such was the case a few weeks ago in the House Ways and Means Committee. Listening to a seemingly endless parade of witnesses, Del. Henry R. (Bobby) Hergenroeder Jr. (D-Baltimore) found himself doodling with a list of the 141 members of the House of Delegates.

"I found myself underlining the names of the people you would call movers and shakers in the House," Hergenroeder said. "Once, you could list three or four people who controlled the House. But under (House Speaker Benjamin L.) Cardin the tentacles have expanded. More people influence policy now." Expanding the circle of power in the House of Delegates is something that Cardin says he set out to do when he became speaker.

Hergenroeder came up with a list of 20 people who, he says, dominate the House. These are the people, the four-term delegate said, who ultimately decide what legislation will get out of committee and reach the floor of the House. And, unlike the Senate, most of the important decisions in the House are made in committee.

Not everyone agrees with the list but most people presented with it conceded that, at the very least, Hergenroeder was on the right track. This is Hergenroeder's list, with his explanation of each person's signficance:

Cardin (D-Baltimore): "He's the master of organization and knows when to delegate authority and when to invoke it himself."

Donald B. Robertson (D-Montgomery), the House Majority Leader: "Don's a technician, a great parliamentarian. He's the mortar that holds the bricks together. It's not a glamorous role but he's very important to Ben."

Paul E. Weisengoff (D-Baltimore): "The master vote trader. He collects votes, trades off on issues. His strength is generating a consensus." (He is also Cardin's best friend in the legislature.)

Raymond E. Beck (R-Carroll): "A fiscal whiz, an advocate on issues. Respected by everyone, including the Democratic leadership, which makes him an influential factor. He's built a lot of good bridges. A genuine intellectual."

Torrey C. Brown (D-Baltimore), chairman of the Environmental Matters Committee: "An environmentalist, knows his issues. A very strong committee chairman." (Also the only M.D. in the House).

Kay G. Bienen (D-Prince George's): "One of the nonleadership movers. She's very strong on environmental matters and gets things done. People respect her."

Tyras S. Athey (D-Anne Arundel), chairman, Ways and Means Committee: "A good chairman on an important committee."

Gerard F. Devlin (D-Prince George's): "Articulate, respected, one of the leaders of the P.G. delegation. And Athey delegates a lot of his authority on Ways and Means to Gerry."

Dennis C. McCoy (D-Baltimore): "Chairman of the (Baltimore) city delegation. That puts him in charge of the largest delegation (33 members) here."

Thomas B. Cumiskey (D-Allegeny): "Bright, well-liked and respected. Nonleadership but still an important guy."

John R. Hargreaves (D-Caroline), chairman, Appropriations Committee: "Chairman of the committee that deals with a lot of the budget."

Thomas B. Kernan (D-Baltimore), assistant majority leader: "He's at least as important for his role on Ways and Means (he is generally regarded as Cardin's man on the committee) as for his leadership role."

Nancy K. Kopp (D-Montgomery): "Another intellectual, very capable. She is the mastermind when it comes to studying the budget."

R. Clayton Mitchell Jr. (D-Kent): "He's been around, he's well-liked. Urban-oriented. He gets along very well with the leadership." (In fact, Cardin almost chose him as majority leader four years ago).

Helen L. Koss (D-Montgomery), chairman of the Constitutional and Administrative Law Committee: "She has done a good job as chairman. Another intellect. A lot like Robertson, a technician."

O. James Lighthizer (D-Anne Arundel): "This may reflect my Ways and Means bias. Jim's very visible though. You always see him around." (He also is leaving the legislature to run for Anne Arundel county executive.)

Robert R. Neall (R-Anne Arundel), assistant minority leader: "Well-liked, works well with Beck. Influential on appropriations."

Frank C. Robey Jr. (D-Baltimore): "He's very smart and he's intellectual on appropriations just as Neall is." (Also chairman of a key appropriations subcommittee, the Law Enforcement and Transportation Subcommittee).

Joseph E. Owens (D-Montgomery), chairman of the Judiciary Committee, and Frederick C. Rummage (D-Prince George's), chairman of the Economic Matters Committee: "Their power is not the same as some of the others because it's strictly limited to their committees."

Cardin, too much the politician to delete any names when presented with the Hergenroeder list, added a couple. Of Lucille Maurer (D-Montgomery), he said, "You don't deal with any education issue without talking to her," and of Thomas A. Rymer (D-Calvert), "People like Tom and he gets votes in committee. He just does it more quietly than some others."

The only freshman on the list is Lighthizer. Hergenroeder and Cardin agreed that Timothy F. Maloney (D-Prince George's) might qualify for the list for the same reasons Lighthizer does: He's visible and well-known among the delegates.

Hergenroeder admitted to one gaping hole on his list: Not one of his so-called movers is black.

"The problem is they're pretty divided right now," he said. "There isn't any one person among the black delegates who you would automatically think of approaching about an issue."

Additionally, the black caucus was rocked recently when it was revealed that its chairman, Frank M. Conaway (D-Baltimore), is being investigated by the state insurance commission for misuse of funds connected with his insurance company.

What does the list mean? Not much, except, according to Hergenroeder, "There are a handful of people who Cardin sends out all his feelers through. If you know who they are you know just who you talk to if you want to be sure your thinking is being heard by the people who count."