Fig. 3 Cytoplasmic formation of free MTs. Time sequence shows free MTs which appear, grow and fill the nascent lamellum of a PtK1 cell. Almost no long MTs grew into the lamellum area from the central part of the cell. About 40 free MTs appeared in this series and their orientation seems nearly random. Time after first frame shown in lower left of each frame in seconds. Scale bar, 10 µm.