THE 
NEW PHYTOLOGIST 
Vol. XXI, No. 4 November 7, 1922 
PERMEABILITY 
By WALTER STILES 
CHAPTER IX 
THE WATER RELATIONS OF THE PLANT CELL 
t ntimately connected with problems of cell permeability are the 
1 water relations of the cell. Already in the preceding chapter in 
considering the evidence for the existence of plasma-membranes it 
has been necessary to touch on this subject. It has there been indi¬ 
cated that the evidence for the existence of a semi-permeable mem¬ 
brane forming the limiting layer of the protoplasm is very conflicting. 
Hence in the case of the non-vacuolated cell it is not at all clear 
whether it is correct to think of the cell with regard to its relations 
to water simply as an osmotic cell, that is, as a solution of osmotically 
active substances enclosed in a semi-permeable membrane, or whether 
we are to compare it rather with a colloidal system such as a gelatine 
or agar-agar gel or blood fibrin. It is true that M. H. Fischer (1908, 
1910, 1915) has shown that certain animal tissues (frog’s muscle and 
sheep’s eyes) behave similarly to gelatine and blood fibrin with regard 
to the absorption of water, while MacDougal (1916 a, 1916 b, 1917, 
1918, 1920, 1921) and MacDougal and Spoehr (1917 a, 1917 b, 1917 c, 
1919, 1920) have succeeded in preparing colloidal mixtures of agar- 
agar with gelatine, albumin or other proteins, urea or amino-acids, 
in which agar-agar forms at least three quarters of the whole, the 
so-called bio-colloids, which are very similar to plants in their be¬ 
haviour towards water. Lloyd’s work indicating a similar conclusion 
has been referred to in the last chapter. But while we may be sure 
that living plant protoplasm will imbibe water in the same way as 
Phyt. XXI. IV. 
12 
