Regional variation of poleward microtubule flux in spindles assembled around plasmid DNA-coated beads. (A) X-rhodamine tubulin speckles and autofluorescent beads. (B and C) Speckle trajectories color coded according to the velocity histogram (C); the flux rate of the spindle shown is mean ± SD = 2.69 ± 0.74 μm/min (N = 2,128 trajectories). (D and E) Mean and SD (error bars) of speckle velocities within regions in D. (F) Spatial distributions of normalized microtubule velocities of nine bead spindles. Bar, 10 μm.