4to BOTANICAL GAZETTE [ DECEMBER 
alge should die in a concentration less in osmotic value than the 
cell sap, z. ¢., at a concentration weaker than the plasmolyzing 
strength, death could hardly be attributed to the water-extract- 
ing properties of the molecules or ions. 
EXPERIMENTAL RESULTS. 
I have studied, according to the method just described, those 
substances which have been most used by biologists as plasmo- 
lyzing agents, cane sugar, glycerin, sodium chlorid, and potas- 
sium nitrate. 
The numerical data obtained are brought together for more 
ready reference in the following table. Three important points 
determined for each substance are presented: (1) the concen- 
tration of the solution in which plasmolysis begins in the Spiro- 
gyra studied stated in gram-molecules of the substance per liter 
of water; (2) the calculated boundary concentration, assuming 
a purely osmotic action of a type not more injurious than that 
seen in cane sugar; (3) the boundary concentration found by 
experiment. 
The temperature varied between 22° and 30° C. as limits. 
Although the significance of relationships is lost when the con- 
centrations are so stated, I have added percentage values to 
facilitate comparison with results obtained by other investigators. 
As an “antidote” for the percentage values, the molecular 
weights of the substances under study are also added. 
Plasmolyzingconcen- | Calculated boundary Experimental boundary 
tration concentration concentration 
Substance ny 
Per Per ipelebee 
gm. mol. per |. cont, | o™- mol. perl. | cont, | 8: MO pet then 
Cane sugar..... 342.0] 0.33(%) |11.4 0.75 (34) [25-7 
Gayeerm . 5c, . 92.0] 0.33 (1%) 3.1 0.75 (34) 6.9 | 0.50 (4) npr 
Sodium chlorid..| 58.5] 0.25 (14) 1.5 | 0.46 2.7 | 0.10 (zo) se 
Potassium nitrate|101.0| 0.25 (1%) 2.5 0.47 4.5 | 0.06 (zx) | 03 
Po 
As appears in this table, Spirogyra just begins to plasmolyze 
in a cane sugar solution having a concentration of 4% gm. mol: 
