TgoI | PHYSIOLOGY OF POLYMORPHISM IN ALGAE 301 
between the degree of dissociation at 0° C. and at 25°C. is so 
small as to be neglible for our present purpose. 
The data obtained by these tests of the actual molecular 
conditions within these solutions are given in Table V. This 
is a supplement to the table given in the author’s previous 
paper on this subject. In the first column are given the 
so-called percentage strengths of the solutions employed. 
In the second the solutions are designated by the letters 
previously used for that purpose (Joc. cit., p. 599). The next two 
columns contain the depressions of the freezing point and the 
elevations of the boiling point as directly observed. Then fol- 
low the two columns containing the osmotic pressures at the 
freezing and boiling points given in atmospheres. These num- 
bers were obtained from A; and A, by the formulae given above. 
In the next two columns are given the pressures at 25° C., meas- 
ured in centimeters of mercury, I being found from P; by direct 
application of the law of Gay-Lussac, 2 by interpolation between 
P, and P;. The last column contains the pressures originally 
calculated by the assumption of complete ionization. They are 
introduced here for comparison. 
It will be noted that there is a considerable range in the 
actual osmotic pressures of the different solutions whose calcu- 
lated pressures are the same. This would be expected and is 
partially due to variations in the degree of ionization of the dif- 
ferent salts according to their influence upon one another. It 
is also in part brought about by the fact that K,HPO, dissociates 
completely only in very weak solutions. But this range of pres- 
sures lies entirely within the range of the pressure limits found 
for the several responses of the plant (Joc. cit., pp. 301, 306, 313). 
That is, the errors of calculation, while very large from a physi- 
cal point of view, are not large enough to affect the physiologi- 
cal conclusions already expressed. This is on account of the 
comparatively low degree of sensitiveness of the organism with 
which we are dealing. 
Discussion of the reasons for the curious variations from the 
calculated pressure manifested by these tests will be reserved 
