Mitotic apparatus is the set of aster fibers, radial structures around each centriole pair, plus the spindle fibers, fibers that extend across the cell between the two centriole pairs located in opposite cell poles. The mitotic apparatus appears in prophase and has important role in the orientation and gripping of chromosomes and other cellular elements causing them to separate and migrate to opposite cell poles.

Substances that disallow the formation of the mitotic apparatus, like colchicine, a molecule that binds to tubulin molecules and prevents the synthesis of microtubules, interrupt cell division.
Colchicine is used to study chromosomes since it paralyzes mitosis when chromosomes are condensed and so are more easily viewed under the microscope.   _{Your Comment}