1910] STOCK BERGER—TOXIC SOLUTIONS AND MITOSIS 413 
marked discrepancies in nuclear behavior, it was believed, could 
safely be regarded as a result of toxic action. 
Root tips which were exposed to #/12 copper sulfate solution for 
three minutes and then transferred to distilled water for three hours 
showed the effect of strong toxic action in the peripheral cell layers. 
Here the cells were dead, but in the inner periblem occasional nuclei 
were in division, but frequently the cell plate had failed to form (fg. 
3). In the majority of the uninjured cells the nuclei were in the 
typical resting stage. In no case did nuclei which were in the spireme 
Stage show the hyaline polar caps, frequently figured as characteristic 
of the development of the normal achromatic figure in Vicia Faba, 
and occurring in the controls grown in sphagnum in these experi- 
ments (jig. 6). The nucleoli were usually large and frequently 
occupied a clear area surrounded by the linin network, as seen in 
fig. 3. Many nuclei contained two large nucleoli, each lying within 
a distinct clear area. In the degenerating nuclei of the injured cells 
the persistent nucleolus was generally of very large size, and the form 
of the nucleus was usually outlined only by the Jinin network, all 
chromatic substances other than the nucleolus having lost their 
usual staining properties. In some cells the cytoplasm showed 
modifications apparently due to the action of the copper sulfate, 
although these were usually not sharply defined, but in some cases 
numerous large vacuoles occurred distributed through the cytoplasm, 
in others huge vacuoles had formed at the sides of the nucleolus, 
presenting much the appearance of the older cells in which large 
Sap cavities had formed. 
In root tips which had been exposed for three minutes to /12 
copper sulfate solution and then placed in water for seven hours, 
the cells presented much the same general appearance as those 
examined at the end of the three-hour period. The greater part of 
the nuclei were in the resting stage, though a few cells of the inner 
periblem showed spiremes forming. Occasional nuclei were farther 
advanced in division, but no stage later than middle anaphase was 
seen. In the distribution of the chromosomes, and in their manner 
of passing from the nuclear plate, no deviation from the typical 
process occurring in the controls in sphagnum was observed. After 
22 hours a decided change in the appearance of the cells of the root 
