Protoplasm to some Reagents. 493 
(0*9 M) ethyl alcohol half of the cells will be killed in forty hours, and 
half survive. 
It must be remembered, however, that no cell probably escapes without 
considerable ill effect when the time of treatment is sufficient to kill 50 per 
cent, of them. For concentrations below 4 per cent, the curve can be 
regarded as only approximate, since in weak solutions the time required to 
1 25456789 10 
Days' oF treatment 
Fig. 3. The curve is based on the time required to kill half of the total number of cells on an 
Elodea leaf in solutions of ethyl alcohol of concentrations of I to io per cent. The ordinates are 
percentages of alcohol in solution. The abscissae are days of treatment. The curve shows, for example, 
that a cell will stand an even chance of surviving after being twenty-eight minutes in io percent, 
alcohol, eighteen hours in 7 per cent, alcohol, &c. 
kill varies greatly. Thus, in material subsequently worked upon in London 1 
all cells in an Elodea leaf, including the more resistant basal ones, were 
killed in a 2 per cent. (0-3 M) alcohol solution in two days. Furthermore, 
the cells may become much deteriorated in a few days apparently with¬ 
out actually dying. 
From the curve it will be seen that a concentration of about 9 per cent. 
1 Some of the experiments here recorded were repeated on Elodea collected near London with 
the purpose of ascertaining if different specimens growing in different localities reacted differently to 
the reagents. These duplicate experiments were carried out in the Huxley Laboratory of the 
Department of Botany of the Imperial College of Science and Technology, London. The writer wishes 
to express to Professor V. H. Blackman his appreciation of the courteous and helpful treatment 
which was accorded him while working in the Huxley Laboratory. 
K k 
