Ku Klux Klan-owned clothing and cigarette companies, sterility-causing sodas, a military conspiracy to infect Africans with AIDS.All are rumors or contemporary legends, told over and over by African Americans, says Patricia Turner, a UC Davis associate professor of African-American and African studies who examines the evolution and meaning of such legends in her new book, "I Heard It Through the Grapevine." Such rumors are spread partly to cope with racial tensions, reflecting ambivalence about government and predominantly white-owned businesses, Turner says. In some cases, those in which the rumors concern consumer goods targeted specifically to African Americans, such rumors serve as reminders that marketing perceived as "for blacks only" should be scrutinized thoroughly. In other cases, rumors such as those about health are a vehicle for individuals to translate their concern for the fate of the group as a whole into more personal, concrete terms, Turner says. Her book will be published this fall by the University of California Press.