1940 Volume 54 Issue 639 Pages 89-96
The spindle figure of the somatic mitosis in the young prothallium cells of Osmunda japonica THUNB. was studied morphologically on living material.
In the late prophase the interior of the nuclear cavity is taken up by chromosomes and the atractoplasm, which is considered to be a derivative of the karyolymph, while outside the cavity, especially in the neighbourhoodof the poles, there is active cytoplasm. Upon development of the prophase nucleus into the metaphase spindle, the nuclear cavity changes progressively from a spherical to a fusiform shape, in such manner that an interface continues to separate the nuclear contents from the cytoplasm, thus preventing any mixture of the two. The disappearance of the nuclear membrane, and the consequent possibility that the nuclear contents may have become mixed with the cytoplasm in the fixed materials, may be considered a result of artefacts caused by fixatives
The interface of the metaphase spindle figure, which gradually changes its shape, exists even in the telophase, where it appears as the phragmoplast. Throughout the stages from the metaphase to the early telophase, the spindle figure acts in respect both of its form and its function as a system independent of the cytoplasm.
The cell-plate grows laterally in the phragmoplast and develops into a cell wall from the point of contact with the mother cell membrane. The cell wall, therefore, is built up progressively from one side to the other. After the formation of the cell wall the residue of the phragmoplastsubstance assumes a cytoplasmic nature and disappears into the cytoplasm.