Distribution of the size of clones generated by single CD34⁺CD38^low (3 experiments) and CD34⁺CD38^neg (5 experiments) cells at day 10. Single-cell cultures were established from CD34⁺CD38^low (A,B) or CD38^neg(C,D) in the presence or the absence of MS-5 cells and in low GF (A,C) or high GF (B,D) as indicated. Nucleated cells were counted in each well at day 10 and the clones classified according to their size, as indicated. Each histogram represents the proportion of the (n) proliferating wells containing the indicated number of nucleated cells.