312 BOTANICAL GAZETTE [OCTOBER 
chloride. It is necessary, therefore, to draw our conclusions from 
the results of periods of equal length only. The relative permeabil- 
ity to different salts will then be represented by the following 
figures: calcium chloride 2.2, sea water 2.2, lanthanum nitrate 
2.1, sodium chloride 2.1. | 
TABLE I 
PERMEABILITY OF DEAD TISSUE OF Laminaria 
: f con 
Solution in upper cell| Solution in lower cell | a _suctiviy . pers 
Half sea water...| Sea water...... ‘5 1.8 
CaCh, 0.14 CaCl, 0.28 M. 4.5 2.2 
lf sea water Sea water...... I2 ee 
‘ Basra eewOumaeeee, Vee rs *.2 
NaCl, 0.26 M...| NaCl, o. ot 5 2.0 
alf sea water...| Sea water...... 12 1.2 
La,Cl, 0.05 M..| La,Cle, o ae 4.5 2.1 
NaCl, 0.26 M...| NaCl, 5 OE, 4.5 2.1 
It appears probable that the slightly lower rate of diffusion of 
sodium chloride may have been due to a slight irreversible decrease 
in the permeability of the intercellular substance caused by the 
lanthanum nitrate, by which the tissue had been bathed imme- 
diately previous to the experiment with sodium chloride. This 
would be in accord with unpublished data secured by OSTERHOUT 
by determination of the conductivity of the tissue. 
The differences which might be expected to arise as an expres- 
sion of the diffusion coefficients of the salts are evidently of so 
small an order as to fail to influence appreciably the rate of diffusion 
through dead tissue. In view of the very imperfect state of our 
knowledge of diffusion coefficients, it would be unprofitable at the 
present time to attempt any further explanation of the influence 
of that factor in our experiments. 
It will be seen from the data given in table II that the presence 
of living protoplasm greatly decreases the permeability of the tissue 
as a whole. Living protoplasm offers, therefore, a very consider- 
able resistance to the passage of salts. That it is not normally 
(in sea water) impermeable to salts will appear from the following 
considerations. The permeability of the protoplasm for conven- 
