The induction of CFUs from Lin⁻CD34⁻ cells in vitro. Lin⁻CD34⁻ cells were isolated from 5 individual samples and cultured for 7 days on HESS-5 stroma cells. One thousand cells were plated in methylcellulose medium before and after culture. The colonies were counted 14 days after plating. *The percentages of CD34⁺ cells in the Lin⁻CD34⁻ cultured cells at day 7, when the 1,000 cells were plated in the methylcellulose.