314 BOTANICAL GAZETTE [ocTOBER 
the conductivity will be proportional to the concentration, and a 
change of 1 per cent in the conductivity of a 0.26 M solution may 
be assumed to indicate an increase of 0.0026 M in the concentra- 
tion. An increase of this size in 5.4 cc. of solution will necessitate 
the addition of 5 _— 
5 Oo: 0026, or 0.0000140 gm. molecules of salt. 
If we divide oe pane chisel: | in this manner for the various 
salts, by the area of tissue in sq. cm. through which salts can pass, 
we obtain the figures given in table III. The figure for sea water 
was obtained by assuming all of its conductivity to be due to 
sodium chloride; but since sea water contains about 12 per cent 
of its electrolyte as salts of bivalent elements, which have a higher 
molecular conductivity than sodium salts, its actual molecular 
content is less than that of a sodium chloride solution having the 
same conductivity, and the figure given in table U1i is thus slightly 
too high. 
TABLE III 
GRAM MOLS DIFFUSING PER SQ. CM. PER HOUR 
THROUGH LIVING Laminaria 
Upper solution Lower solution po Se ng 
sea water..... MELO ee a ©.0000425 
NaCl, o - = Wane ee o,53 Mo... 0.0000610 
CaCl, ort Mc: CaCl, 0.28 M..:... ©.0000150 
La (NOs, °. ee M..| La (NO,\«, 0.10M...| 0.0000034 
The data of tables II and III also show that there is a selective 
permeability to the salts used. Sodium chloride is allowed to 
pass through the tissue most rapidly, the salts of sea water next, 
calcium chloride considerably less rapidly than sea water, and 
lanthanum nitrate least of all. That the effect is produced in large 
part by the kations, as was to be expected, is shown by the fact 
that preliminary experiments with lanthanum chloride (lacking 
the preliminary comparison period in sea water) showed a per- 
meability comparable with that to lanthanum nitrate. Thus in 
one experiment with lanthanum chloride the change of conduc- 
tivity of the upper solution was 0.30 per cent per hour, while that 
quoted for lanthanum nitrate is 0.33 per cent per hour. Whether 
