1. The amphithecium and the endothecium are derived from the cell of quadrant, and the amphithecium is divided further into the inner and outer peristomial layers by periclinal walls.
2. The inner peristomial layer arises from the inner amphithecial layer, undergoing cell division until it is composed of 20-24 cells in cross section by the formation of anticlinal walls.
3. The outer peristomial layer comes to have sixteen cells in cross section by the formation of anticlinal walls. These sixteen cells of the layer undergo no further division.
4. Both peristomial layers form eight groups, each of which is composed of 2 rows of the outer layer and 2 or 3 (mostly 3) rows of the inner layer, and gives rise to two teeth.
5. The ridges of thickening, corresponding to the peristome are laid upon the periclinal walls between the two (inner and outer) peristomial layers.
6. Before the thickenings are deposited, the nuclei in the cells of two layers taking part in the formation of the teeth, are enlarged. And then the protoplasm of both inner and outer peristomial cells moves towards the outer walls of the inner peristomial cells. Following the thickenings the vacuoles appear in cell cavity and both the cytoplasm and the nuclei gradually shrivel away and disappear.
Finally the writer expresses many thanks to Dr. Akira Noguchi, Prof. of the Kumamoto University for his kind abvices.
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