Stella Adler, one of the theater’s great actresses and teachers who coached such people as Marlon Brando and Shelley Winters, died in her sleep early yesterday at her Los Angeles home. She was 91.Cause of death was heart failure. Adler was still an active contributor to the two acting conservatories that bear her name, located in New York and Los Angeles. Although she taught her last formal master class in the summerof 1991, she lectured at least once a semester in each class. Born the daughter of actors Jacob and Sara Adler, Stella had her first stage role at the age of 4, working in Yiddish theater. She performed in both London and New York during the early part of her career , later touring on the Orpheum vaudeville circuit. In the mid-1920s, she enrolled at the American Laboratory Theater school, founded by former Moscow Art Theatre members Richard Boleslavsky and Maria Ouspenskaya. It was there she learned the acting concepts of Konstantin Stanislavsky. She came to prominence in the 1930s as a member of the Group Theater. There she honed her skills as a Stanislavsky idealist, working with such people as Lee Strasberg, Cheryl Crawford and Harold Clurman, whom she would later marry. The theater group was created as an alternative to New York’s commercial theater, and worked with then-new talents Clifford Odets and Robert Lewis. “I can remember hitchhiking from college to go see Stella star as ‘Bessie’ in Clifford Odets’ play ‘Awake and Sing,’ ” said playwright Jerome Lawrence yesterday. “She was a great life spirit in the theater.” Adler played several leading roles in Group Theater productions, but became increasingly disillusioned with Strasberg’s interpretation of Stanislavsky’s teachings. In 1934, she took a leave of absence from the company and went to Europe, where she was introduced to Stanislavsky himself. After studying with him daily, she returned to the Group Theater and helped them refocus the acting experience away from emphasis on the actors’ personal emotional experiences and more toward discovering the emotional experiences of the characters they portrayed. As a teacher, Adler said her job was to inspire students, not to teach. “The teacher has to inspire. The teacher has to agitate,” she told the New York Times in 1984. “You cannot teach acting. You can only stimulate what’s there.” In addition to Brando and Winters, her more famous students included Robert De Niro, Warren Beatty, Candice Bergen, Peter Bogdanovich and Elaine Stritch. Adler also directed several New York stage productions, and appeared in a few films, including “Love on Toast” (1938) and “Shadow of the Thin Man” (1941). “When she moved to the West Coast, she used to hold court at my house and people, not just actors but writers and directors, would flock to the sessions just to listen to her,” Lawrence noted. “She was amazing. She could tell a playwright what was in his play that he or she didn’t even know was there.” Adler was the subject of a 1989 PBS documentary titled “Stella Adler: Awake and Dream.” In 1991, the Equity Waiver theater adjacent to her L.A. conservatory burned down. The exec directors of the conservatory are in the process of finding a new home in Hollywood for the theater. She is survived by her daughter, Ellen; sister, Julia; granddaughter, Sarah Oppenheim; grandson, Tom Oppenheim; stepdaughter, Victoria Wilson; and niece, Lulla Rosenfeld. Funeral arrangements are pending. There will be memorial services in both New York and Los Angeles sometime in January.