Abstract
Each stage of nuclear division inMicrasterias americana was investigated by electron microscopy. Some chromosomes in metaphase had two or more centromeres on them, that is, they were polycentric. The centromere was roundish, moderately dense, and partially embedded in the chromosomes. Many microtubules of the spindle fibers were attached to the centromere. Abundant granules of high electron density, derived from dictyosomes in the cytoplasm, were seen in the metaphase spindle. Only the chromosomes moved towards the poles in anaphase, while these granules remained at the equatorial plate. Many nucleoli appeared in early telophase in one or more regions in almost all chromosomes. These nucleoli fused and enlarged during telophase.
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Ueda, K. Electron microscopical observations on nuclear division inMicrasterias americana . Bot Mag Tokyo 85, 263–271 (1972). https://doi.org/10.1007/BF02490172
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DOI: https://doi.org/10.1007/BF02490172