Permeability 205 
These numbers indicate clearly that the artificial cell membranes 
take up less water from solutions of calcium chloride than from 
equimolecular solutions of potassium and sodium chlorides. The 
absorption of water from a 0-2 M solution of calcium nitrate was 
also less than that from an equimolecular solution of potassium 
nitrate. Conversely, the water taken up by the membrane in calcium 
salts appears more easily lost by evaporation than that taken up by 
the membranes immersed in potassium and sodium salts. AsHansteen 
found exactly the same relation to hold between the uptake of water 
and loss of water by evaporation by whole plants with their roots in 
solutions of salts of the same metals, he concludes that living cell 
walls are responsible for this difference in water uptake from different 
salts. The numbers given in Table XXVI, compared with those in 
the previous table, indicate the similarity in the behaviour of whole 
plants and artificial membranes. 
Table XXVI 
Uptake of water by oat plants growing in culture solutions 
of different salts. (Data from Hansteen-Cranner) 
Relative water 
Relative water loss 
uptake per gm. 
per gm. of 
Solution 
of roots 
transpiring part 
N/ioo KN0 3 
100 
100 
N/ioo NaNO s 
86-34 
100-24 
0-177 % Ca(N0 3 ) 2 
82-01 
100-90 
(isosmotic with 
N/100 KNO s ) 
N/ioo KN0 3 
100 
100 
N/100 NaN0 3 
82-48 
77-64 
NI100 Ca(NO a ) 2 
76-43 
103-91 
0-177 % Ca(N0 3 ) 2 
82-05 
113-89 
It is to be noted that parchment paper membranes do not behave 
in the same way as the artificial cell wall membranes, for the uptake 
of water by parchment paper was almost the same whatever the salt 
dissolved in the water. Obviously parchment paper membranes can¬ 
not be compared physiologically with cell walls. On the other hand, 
lipoid-free artificial cell wall membranes behave in a similar fashion 
to the lipoid-containing membranes as regards uptake of water 
from solutions, even absorbing more water than the untreated 
membranes, while the parchment paper membranes take up con¬ 
siderably less. 
These results suggest strongly that the uptake of water by the 
cell wall is influenced by the nature of the solutes in the external 
medium, so that the cell wall cannot be neglected in a complete view 
