1. The development of the male gametophyte in
Tradescantia canaliculata the cult. No. 88, 14, 1, a descendant of the plant bombed at Hiroshima 1945, was investigated. Most of the studies were performed
in vivo.
2. The shape of the M.S. is a quarter of a sphere, having two semicircle plain side walls and one spherical dorsal wall. The nucleus generally occupied the center of the cell. Two large vacuoles are found on both sides of the nucleus in the cell mentioned above, the a-case M.S., but in some rare cases the nucleus occupies one corner of the cell and a large vacuole the other corner, the b-case M. S.
3. The 1st cell division in the a-case M. S. results in a large V.C. and a small G. C., the latter penetrating later into the cytoplasm of the former, but in the b-case such special development was not shown. The data show that the divided sister cells have no specialities by themselves.
4. The substance forming the phragmoplast was traced. It secreted the wall substance and the remnant contains lecithin which plays an impor-tant role in the vacuole formation
. 5. The nuclear granules appear in the nuclei and are secreted out into the cytoplasm, where they develop into vacuoles, absorbing water.
6. The maturation of the P.G.s was followed and it was found there are several grades in the development in the grains in one and the same anther which reached the last stage of development.
7. The germination of the P. G.s was traced
in vivo. The development of the vacuoles in the grains and their position in the grain play some role in the development of the pollen tube, especially in the determination of the point from where the tube comes out from the grain and also of the number of the tubes.
8. In the most germinated P.G.s the G.C. and the N.V.C. stayed in the grain proper, and did not move into the elongated pollen tube.
9. The growth of the C.S.H. was described.
10. The role that vacuole formation plays in the growth of the cells in plants was discussed. The vacuoles originating from the nuclear granules cause the cell growth and the expansion of the surface area of the cell, but the growth of the vacuoles is not the result of cell growth.
11. Non-transportation into the pollen tube of the G.C.s and of the N.V.C., especially of the former, must be the cause of the absence of the embryo in the seeds ; while the penetration of the pollen tube into the style, even when not accompanied by any nuclear mass may give the stimulation for the execution of the growth of the ovary and also of the ovules which are parts of the body of the mother plant, and would be withered off if certain stimuli to regain the vital energy were not given.
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