Electron Microscope Studies on the Mitotic Figure

II. Phragmoplast and cell plate

Abstract

1. The fine structure of the phragmoplast, that of the cell plate, and its formation in meiosis has been examined by means of the electron microscope in pollen mother cells of Lilium lancifolium fixed with CdC1₂ alcohol solution.
2. The barrel-shaped phragmoplast is consisted of innumerable parallel fibrils lying vertically to its equatorial plane, and of the fluid substances with lower density to the electron beam, which fill up the interfibrillar space.
3. The cell plate appears from its initiation as two parallel layers composed of unit fibrils which are different from those of the phragmoplast. The unit fibrils of the cell plate lie crossing vertically crosswise to the unit fibrils of the phragmoplast.
4. The cell plate develops centrifugally in the phragmoplast along its equatorial plane.
5. After the cell plate reaches the mother cell wall, cell-wall forming substances from this mother cell wall are diffused into the space between the two lamellae thus making one cell plate. The hardening of the daughter cell wall develops centripetally.
The author wishes to express his appreciation to Professor B. Wada for his encouragement and suggestion. The author is also indebted to Dr. N. Tanaka and Mr. S. Sakata for criticism and technical help in carrying out this work. This work was supported in part by a grant from the Science Research Fund, Ministry of Education, and in part by a research grant from the Fuju-Kai Research Encouragement Fund.