Structure of Plant Cells with Special References to Lower Plants I

Mitosis in Spirogyra setiformis

Abstract

Somatic mitosis of Spirogyra setiformis was studied with special attention to the behaviour of a “nucleolus”.
In the prophase, a “nucleolus” is transformed into fine chromonemata. Both chromonemata derived from the “nucleolus” and derived from the “Außenkern” or the nuclear part outside of the nucleolus, shift together toward the nuclear plate of the spindle.
In the anaphase, about ten chromosomes are pulled out from the daughter chromosome-group toward the mitotic pole. A membrane surrounding the main daughter chromosome-group and the poleward proceeded chromosome-group, develops into nuclear membrane.
The main chromosome-group swells and becomes a spherical body or a “nucleolus”.
Most of the poleward proceeded chromosomes, are unravelled to fine chromonemata which exist in the “Außenkern” at resting stage. Part of the chromosome which remains without unravelling throughout the resting stage, is designated as a “Nebenkörper”.