Fig. 2. Basal cells were plated onto type I collagen (open bars), type IV collagen (closed bars) and laminin-1 (grey bars) for 5 and 20 minutes and the nonadherent cells were washed off and plated onto fresh ECM-coated plates (marked as 20 min+ and 60 min+). Cells were counted before the addition of irradiated feeders and were then cultured for up to 21 days. Controls were plated with no pre-selection. Colonies containing 32 or more cells were scored. Colony forming efficiency (CFE) was calculated as the number of colonies formed per number of adherent cells x100%. CFEs are expressed as the ratio of the control CFE. Results shown are the means±s.e.m. of five experiments.