40 
Walter Stiles and Ingvar Jorgensen. 
ON THE RELATION OF PLASMOLYS1S TO THE 
SHRINKAGE OF PLANT TISSUE IN SALT SOLUTIONS. 
By Walter Stiles and Ingvar Jorgensen. 
[With Two Figures in the Text] 
I N the March-April number of this journal, 1 D. Thoday fired the 
maroon, as it were, for a warning of the bomb lie intended to 
drop on us in the May-June number. Now that the attack has 
been delivered, 2 we think it was brought about by a complete 
misrepresentation of our views in regard to a very elementary and 
generally understood matter, in which our opinions do not differ 
from those of anyone else who has interested himself in the subject 
of the osmotic relations and permeability properties of the 
plant cell. 
The essence of the business is that Thoday represents us as 
supposing that the sap of a cell which neither gains nor loses in 
weight when placed in a solution of a salt is of the same osmotic 
concentration as the solution. This is manifestly absurd. On 
page 420 of the paper, 3 which, according to Thoday, moved him to 
call attention to the existence of turgor pressure in plants, will be 
found a passage in which we give the explanation usually advanced 
to explain how plant tissue can remain in equilibrium, as regards 
water exchange, with a solution of lower osmotic concentration than 
the cell sap. Thoday merely gives the same explanation. 
It should have been clear to anyone who had read the part of 
our paper dealing with the swelling of tissue in distilled water, and 
the maintenance of an equilibrium condition between distilled water 
and the cell sap in regard to water exchange, that we did not con¬ 
sider a cell which neither gained nor lost in weight when placed in 
a solution as necessarily isotonic with the cell sap. In regard to 
the one case in which we spoke of a solution as isotonic with the 
cell sap of tissue which altered only slightly in weight after immersion 
in the solution, it should thus have been obvious that we regarded the 
hydrostatic pressure of the solution in the cells as small in com¬ 
parison with the osmotic pressure of the sap. It would have been 
a legitimate ground for criticism if Thoday could have produced 
evidence that the hydrostatic pressure of the water in the cells of 
potato normally possessed a value approaching that of the osmotic 
1 New Phyt., 17, p. 60, 19 L8. 
* New Phyt., 17, p. 108, 1918. 
* Ann. of Bot., 31, pp. 415-434, 1917. 
