570 
BOTANY: S. C. BROOKS 
the same conductivity, and the open 'upper celF with a measured 
amount of a solution of the same salt as that in the lower cell but of 
one-half the concentration. The rate of increase in the conductivity 
of the solution in the upper cell served as a measure of the rate of pas- 
sage of salts through the tissues, and hence of the permeability of the 
tissue to that salt. The errors due to diffusion of salts from the tissue, 
to individual differences in the age and thickness of the fronds, and to 
variations in the area of tissue through which salt could pass, were elim- 
inated by suitable controls. 
The effect of the intercellular material was determined by experi- 
ments in which dead tissue took the place of living. The outcome of 
these experiments was independent of the method of killing. Sodium 
< t ) f 6 s t« 11 K<^ry 
FIG. 1. FIG. 2. 
FIG. 1. APPARATUS FOR THE DETERMINATION OF PERMEABILITY BY DIFFUSION 
THROUGH A DIAPHRAGM OF TISSUE. 
FIG. 2. PROGRESSIVE CHANGES IN THE PERMEABILITY OF LAMINARJA TISSUE CAUSED 
BY SOLUTIONS OF DIFFERENT SALTS. 
and calcium chlorides, lanthanum nitrate and the salts of sea water 
passed through the diaphragm of dead tissue at a very consider- 
able rate which did not differ materially in the case of the different 
salts; the rate of change of conductivity of the solution in the upper 
cells was between 2.1% and 2.2% per hour during successive four and 
one-half hour periods of diffusion of the different salts through the 
tissue. There was therefor no selective permeability of the intercellu- 
lar substance to the ions used, and no alteration of its permeability 
caused by these salts. 
Table 1, based on experiments with living tissue, shows that the rate 
of diffusion of different salts through the protoplasm was considerable, 
and that it was greatly increased by sodium chloride in pure solution; 
that it remained nearly normal in sea water (the increase in the rate of 
