1gto] STOCK BERGER—TOXIC SOLUTIONS AND MITOSIS 415 
the root tips examined after 30 hours, division still occurred in the 
periblem cells. The chromatic figure was regularly found, but only 
in the inmost layers of cells was the spindle unaffected. The nuclear 
plate had formed in the central spindle region of most cells, but 
usually failed to reach the walls. 
In the root tips placed in distilled water for three hours after seven 
minutes’ exposure to 2/12 copper sulfate, very few mitoses occurred 
in the periblem cells, but in these the chromatic figure presented a 
normal appearance. The cytoplasm of all the outer periblem cells 
exhibited large vacuoles, some of which had enlarged sufficiently to 
drive the nucleus to one side of the cell, and in the inner periblem 
frequent cells developed unusual vacuoles. In some cells in late 
anaphase vacuoles occurred between the cell plate and the daughter 
nuclei (fig. 5), a condition which occurred also in the distilled water 
controls, but division did not proceed farther in the copper solution. 
At one side of some cells the plate, failing to reach the lateral wall, 
ended in a fibrous plasma mass about half-way between the axis 
of the spindle and the wall of the cell. In the cells at the apex of 
the root tip occasional nuclei were in early prophase, anaphase was 
frequent, and a few nuclei were at telophase. © In the latter stage the 
cell plate had formed in the normal manner, but in practically all 
the nuclei at anaphase no trace of cell plate appeared. In some cells 
the spindle fibers were only faintly visible, in others a perceptible 
thickening of the fibers had occurred in the equator of the spindle, 
but no figure showed the line of granules characteristic of cell plate 
formation. In the resting nuclei, as usual, there occurred one or two 
large nucleoli. These were rarely circular as viewed in optical 
section, but were amoeboid in form. 
In radicles placed for ten minutes in 2/320 copper sulfate, then 
transferred to distilled water for three hours, the dermatogen ceils 
were dead and many of the outer periblem cells lacked nuclei. The 
nuclei present were in the resting stage. Numerous mitoses occurred in 
the cells of the plerome and inner periblem, but the larger number 
showed a tendency toward degeneration in the spindle fibers. After 
seven hours the general appearance of the cells was much the same, 
but there were very few mitoses. After 22 and 30 hours, respectively, 
- no division figures occurred in the outer cell layers, but a few cells 
