PERMEABILITY OF THE CELL WALLS OF ALLIUM 
5: C. BReoors 
Many investigators have reported that the tissues of higher 
plants are almost if not quite impermeable to inorganic salts. 
They have usually attributed this phenomenon to the imperme- 
ability of the protoplasm to the salts used. It is quite probable, 
however, that the cell walls themselves may exert an important 
influence on the permeability of tissues.. It is of interest, therefore, 
to point out a striking example of the impermeability of the cell 
wall, which was found when it was attempted to investigate, by the 
diffusion method recently described by the writer,’ the perme- 
ability of epidermis from the inner surface of bulb scales of the onion. 
The principle of the experiment and the apparatus used were the 
same as in the writer’s experiments on Laminaria, as recorded in 
the paper cited. .Certain modifications were necessary, however. 
In order to avoid injury due to drying out of the epidermis 
(which consists of a single layer of cells), it was necessary to reduce 
as much as possible the time intervening between the act of stripping 
the epidermis from the scale and that of filling the cells with solu- 
tions. The whole operation usually occupied about 30 seconds, a 
time which caused no observable injury to the cells. 
Dead material was prepared by exposing freshly sa ee 
sheets of tissue to chloroform vapor for a period of one hour, then 
immediately immersing them in a large volume of distilled water, 
which was several times renewed. After 15 days in distilled water 
the dead tissue was used in the usual manner. 
The salt solutions used in the lower cells were always 0.05 M, 
a concentration hypotonic to the living cells of the onion epidermis. 
In the upper cells there was placed distilled water having a specific 
conductivity of about 2xX10~° mhos. Extreme precautions were 
‘used to prevent access of dust, acid vapors, or any other soluble 
material to the distilled water in the upper cells. In all the 
* Brooks, S. C., A new method of studying permeability. Bor. Gaz. 64: 306-317. 
Sigs. 2. 1917. 
599] [Botanical Gazette, vol. 64 
