Andrews. — The Effect of Gases on Nuclear Division. 525 
time hydrogen reaches the cell enclosing the material for investigation, 
removed all other gases and impurities, leaving pure hydrogen. 
In the first experiment a cell of Trade scantia virginica was placed 
in pure hydrogen and in ten minutes the movement of the protoplasm 
ceased. To ascertain just when the protoplasm stops moving requires 
great care and accurate observation, since a very slight movement is 
easily overlooked. One hour and four minutes afterwards oxygen was 
introduced and the movement began again in five minutes. This 
experiment is verified by the action of hydrogen on the cells of Momordica 
E later him , for when the cells of this plant were subjected to pure hydrogen 
the movement of the protoplasm ceased in ten minutes and began again 
in five minutes as before. When, however, the cells of Momordica Elaterium 
were left in pure hydrogen for six hours they were not killed, but the 
time of recovery and recommencement of movement was thirty minutes. 
That a longer time should be required when left in pure hydrogen is 
not surprising, but shows that if all other conditions were perfect in every 
way a very long time would be required to kill these plant-cells in 
pure hydrogen. 
The three preceding experiments on non-chlorophyll cells of Trades - 
cantia virginica and Momordica Elaterium were carried on in light ; but 
others exactly the same, except that they were kept in darkness, were 
performed with no appreciable difference in the results. 
2. Influence of Hydrogen on Nuclear Divisions. 
When a nucleus in the resting stage is left in pure hydrogen it 
cannot begin division. This was verified by bringing resting nuclei of 
Tradescantia virginica into pure hydrogen for four and one-half hours, 
at the end of which time they still remained in the resting stage and not 
the slightest advance toward division had taken place. At the end 
of this time (four and one-half hours), when air was admitted, the nuclear 
division commenced and was completed. 
When a nucleus was near the close of the prophase stage and was 
brought under the influence of pure hydrogen, indirect division was 
completed and the formation of the daughter-nuclei occurred, but no 
cell-wall was ever formed. 
Such nuclei finished dividing in two hours. The nuclei which I used 
as controls showed that this is somewhat longer correspondingly than is 
required by nuclei of Tradescantia virginica under normal conditions to 
divide. It further shows that the cessation of protoplasmic activity and 
passage of the hydrogen through the protoplasm to the nucleus is 
comparatively slow for such a gas, and thus nuclear division is able to 
advance considerably before being checked by its influence. In all these ex- 
