In the present investigation, the minute structure of the motor cells of
Mimosa pudica L. was studied from the cytophysiological and microchemi-cal view-point. The results obtained are summarized below.
1) Each motor cell of the main pulvinus has thin cytoplasm at the periphery of the cell. It can be differentiated by eosin in the living condition. The inside of this cytoplasmic layer is occupied by a colorless central vacuole in which a tannin vacuole is found. Such a structure was analyzable by the application of the plasmolysis and of the centrifugal force.
2) The tannin vacuoles were stained with chrysoidin, methylene blue, neutral red, and brilliant cresyl blue. If the cells previously stained with crysoidin are treated with caffeine solution the several modes of precipitation in the vacuole are found. These modes are mentioned as follows:
A-
type. Vacuoles stained simply with chrysoidin and free from precipitation.
B-
type. Vacuoles stained with chrysoidin, having precipitation by caffeine in the centre.
C-
type. Vacuoles stained with chrysoidin, having diffuse precipitation by caffeine.
D-
type. Vacuoles indifferent to chrysoidin, having a dense precipitation by caffeine.
3)
B-
type and
C-
type vacuoles usually appear in the cells beneath the vascular bundle. The cells in the upper portion contain but little of them. The distribution of these vacuoles is not modified by the stimulus.
4) By vital staining with chrysoidin, methylene blue, neutral red etc. the tannin vacuoles are observable in the living condition. Through these techniques tannin vacuoles after receiving a stimulus seemed to be smaller than those in the anesthetized pulvinus. In the material fixed by chromic acid or potassium bichromate, the tannin substance is detected as brown colour. By this reaction, when a stimulus is given, the tannin was observed to have infiltrated in the cytoplasm.
5) There are many tannin vacuoles in the motor tissue cells of pulvinule in the closed condition. They appear more markedly inside these motor tissue than outside.
6) These vacuoles are stained with chrysoidin, methylene blue, neutral red and brilliant cresil blue, and the precipitation appears when they are treated with caffeine solution.
7) In the motor cells, especially at the inner part of the pulvinule, their thin cytoplasm found at the periphery of the cells is stained by eosin solution like the motor cells of main pulvinus.
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