Observations on Behaviour of Turgescent Tissue. 6i 
for this strength indicates that a relatively stable condition of 
equilibrium was soon reached which could persist for at least 20 
hours. It would appear that the protoplasm maintained itself in a 
condition approaching closely to perfect semipermeability as regards 
both the sucrose and the solutes of the sap. 
Toxic Substances. 
Mercuric chloride. These results (Fig. 2) are curious in that 
the solutions entered at first apparently faster than distilled water— 
Hours of immersion. 
Fig. 2. Mercuric chloride. 
a quantitative result which was fully confirmed for the M/100 
solution by other experiments. The curves given in Fig. 3, for 
example, represent in each case the average of four sets of 
observations, the pieces used being taken from the same tuber. 
The most rapid entry occurred in the case of the M/100 solution. 
Slices cut from a piece at the end of 7 hours in this solution, tested 
with ammonium sulphide, showed that mercuric chloride had 
penetrated to a depth of 3 or 4 mm. In another experiment, after 
half-an-hour the depth of penetration was only about one millimetre ; 
yet the gain in weight in this short period was 4% as against 2% in 
distilled water. It is unlikely, therefore, that the weight of absorbed 
mercuric chloride accounts for more than a fraction of the difference. 
Another possibility remains to be excluded before the result 
can be interpreted as truly an effect of the mercuric chloride on the 
entry of water into the cells—namely, the injection of the air¬ 
spaces, which has already been mentioned as a source of error. 
No data appear to be available on the effect of this salt in solution 
