1915] HARVEY—ETHYLENE 207 
to differ. On the foregoing assumption one may therefore say the 
nature of the fats in the treated and untreated tissues is the same 
as regards degree of saturation. 
B. ACIDITY 
For acidity determinations the epicotyls were collected as 
described for the chemical analysis. The wet weight of the sample 
was determined, but instead of being preserved in alcohol, the 
tissue was directly triturated with water in a mortar. More water 
was added to bring the mixture up to a definite volume, and finally 
the free acids present were titrated with N/1o NaOH, using 
phenolphthalein as indicator. The entire procedure, from the 
cutting of the seedlings to the end of the titration, required about 
one hour. The foregoing method is rather unsatisfactory; in 
addition to the fact that in this way one estimates only the surplus 
H-ions, other objections may be offered. However, any marked 
relative difference can be caught by this method. 
TABLE VII 
ACIDITY 
cc. of N/to NaOH to 
Wet. wt. of tissue in gm.|neutralize 1 gm. wet wt. 
of tissue 
’ .7241 
Untreated........ ‘e 87.25 ge 
0.5457 
25.65 { 0.8730 
0.77 
Ethylene treated. ... 79.65 e 7313 
0.8288 
29-55 0.8118 
The results obtained are found in table VII, expressed in terms 
of N/1o NaOH required to neutralize 1 gm. wet weight of the tissue. 
No consistent difference is evident between the treated and control 
tissues. 
C. OSMOTIC PRESSURE AND PERMEABILITY 
Osmotic pressure was estimated by two methods, freezing point 
and plasmolysis. For the former method, the juice was expressed 
