1915] OSTERHOUT—PERMEABILITY 323 
produce sufficient rise to overcome the effect of the increase in the 
conductivity of the solution which is contained in the intercellular 
substance. 
The addition of MnSO, in solid form produced a decided rise 
as shown in table V and fig. 5. The amount added was sufficient 
to make the concentration 0.005 M. 
TABLE V 
ELECTRICAL RESISTANCE OF Laminaria saccharina 
: In sea water 1000 cc. 
Time in hours +MnSO, 1.39 gm. In sea water 
(=0.005 M) 
fe) 890 2 890 
22 gI0: 830 
40 
All readings were taken at 18°C. 
It is evident that the addition (to sea water) of a salt in solid 
form is the severest possible test of its ability to produce a rise in 
resistance. In subsequent tests of other bivalent kations this 
method was exclusively employed. 
In table VI and fig. 6 are shown the results of two experiments 
with CaCl, +6 H,O which was added to sea water in sufficient 
amount to make the concentration 0.005 M (1.19 gm. to 1000 cc. 
sea water). The course of the curves is not quite the same, 
the lower curve falling more rapidly than the upper. This differ- 
ence is too great to be the result of experimental error and must 
be attributed to laboratory conditions and to differences in the 
material itself, which shows some variation in this respect unless 
gathered and cut at the same time. It will be noticed that the 
resistance of the control falls off more rapidly in the lower 
curve, which must be attributed largely to laboratory conditions. 
Dead tissue under the same conditions showed no rise in 
resistance. 
