Morphology of factor-dependent and -independent fetal liver cells at day 21 of liquid suspension culture. (A) Cells infected with RufNeo-hβc grown in IL-3, GM-CSF, and Epo. (B) Cells infected with RufNeo-FIΔ grown in the absence of growth factors. (C) Cells infected with RufNeo-V449E grown in the absence of growth factors. (D) Cells infected with RufNeo-I374N grown in the absence of growth factors. Photographs are at 780× original magnification.