The man politely informed Sheppard that the board would not send a black man without a white supervisor.

"I remember seeing a group of 25 or 30 men working on the railroad, with a white supervisor," she recalled.

Mr. Wills said black agents in his office were constantly being undermined by white supervisors.

They were more isolated than ever; their white supervisors would not even say, "Good morning," they said.

"Diversity training has created a lot of friction," said Bradley Wells, a white supervisor.

Economic studies indicate that fewer than 30 percent of planters employed white supervisors for their slave labor.

The conflict reaches such a level that the white supervisors describes it as a "'tribal-war situation.'"

Ms. Morgan said she had asked her white supervisors for a promotion in December.

In most cases, the suit charged, blacks were evaluated by white supervisors.

However, they say, white supervisors may oppose or fail to understand their ideas.