The processes of mitosis and cytokinesis in the multinucleate green alga Acrosiphonia have been examined in the light and electron microscopes . The course of events in division includes thickening of the chloroplast and migration of numerous nuclei and other cytoplasmic incusions to form a band in which mitosis occurs, while other nuclei in the same cell but not in the band do not divide . Centrioles and microtubules are associated with migrated and dividing nuclei but not with nonmigrated, nondividing nuclei . Cytokinesis is accomplished in the region of the band, by means of an annular furrow which is preceded by a hoop of microtubules . No other microtubules are associated with the furrow . Characteristics of nuclear and cell division in Acrosiphonia are compared with those of other multinucleate cells and with those of other green algae .

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