Jean Harris' two grown sons took the stand in her murder trial today, one in his Marine uniform, the other in his banker's gray suit. They said little of consequence. But saying, in this sort of tableau, is probably less important than seeing, and the jury was able to see two well-spoken young men who would do anyone proud.

The Marine called the defense lawyer "sir" and carried himself with superb Marinely carriage. The banker wore a fine tie and a handsome blue and-white shirt and beautiful posture as well. Best of all, both used the word by which every defense lawyer likes to hear his client described: "Mother."

Fomer headmistress of the Madeira School in McLean, Va., Harris has been charged with second-degree murder in the shooting death of her lover, Dr. Herman Tarnower. The defense, claiming the shooting was accidental, has brought forth dozens of witnesses, coworkers from Maderia, former employers, a host of forensic specialists, including three pathologists alone, so far. They have come to praise Harris as teacher, neighbor, headmistress, devoted best girl.

But the defense had yet to portary Harris in her most heartrending role -- Mom. Today, they addressed that Lt. James Harris, stationed in California, arranged a one-week leave to come to court. Older brother David, who lives in Westchester, also took the stand.

The most assiduous court analyst would have been hard-pressed to find meaning in the few things they said. James, a compact young man with his mother's fair hair and upturned nose, identified for the injury two vials of pills which Harris had received in the mail -- something also done earlier by another defense witness. As had happened previously, however, the mysterious pills were never named. James Harris also spoke of having found, in his mother's medicine cabinet, an empty bottle of the same unnamed drug.

David Harris, the eldest son, told the jury of the party Tarnowner had given him the evening before his wedding in the Tarowner home. The party had been Tarnower's idea, according to Harris, not, as a servant of the doctor had earlier testified, the instigation of Jean Harris.

Other witnesses included Madeira staffer Sandra Sisson Santi, director of the Cocurriculum Program, and her husband, Robert, both of whom live at the school.

The Santis had seen Harris the weekend before the Scarsdale shooting, a week in which Harris had expelled four girls. Both described Harris as upset.

"She spoke about the last week at the school, how hard it was . . . how parents wanted discipline until it was their own daughter that was involved," said Robert Santi, adding this was "probably the most upset" he had ever seen Harris.

His wife, to whom Harris had offered use of her car for the conming week, echoed his remarks. Harris, according to Mrs. Santi, had addressed the student body the Friday before the Scarsdale shooting, although that was not her usual practice. She also seemed to Mrs. Santi to be upset.

"She seemed to be in control, very controlled, but very tense underneath, very tired."