Fig. 7. Cells with the pI^-/II^-/scar^- triple mutation contain mainly small acidic endosomes. To examine the morphology of the endo-lysosomal system of pI^-/II^- and pI^-/II^-/scar^- mutants, cells were incubated with FITC-dextran for 1 hour, spotted on coverslips and prepared for phase contrast (A,C,E) or fluorescence (B,D,F) microscopy. Control cells (A,B) contained vesicles of many different sizes, representing pinosomes, macropinosomes, lysosomes and post-lysosomes. By contrast, pI^-/II^- and pI^-/II^-/scar^- cells (C-F) contained only smaller vesicles that are presumed to be lysosomes, because they stained with an acidic fluorophore (data not shown). Bar, 5 µm.