438 BOTANICAL GAZETTE [NOVEMBER 
ating tool than did the tissues of those kept at room temperature. 
In the former, no hemicellulose remains after go-120 days. The 
drawings show the situation in the tissues of the room temperature 
potatoes and the ice box potatoes after a test of 140 days. 
The chemical reaction of the tissues taken from the ice box and 
room temperature potatoes indicates a greater acidity in the former 
than in the latter. Furthermore, it shows that the acidity is 
greatest in the eye region, and that it gradually diminishes until it 
quite disappears as the distance from the eye into the cortex 
increases.” 
Comparative tests of osmotic pressure in sap taken from the 
cortical part of the potatoes and from the vascular cylinder portions 
indicated that there was considerable difference in the sap taken 
from these regions in the same potatoes. There were minor varia- 
tions noted which were easily within the range of error incident 
to the instrument and the indirect method employed in determining 
the osmotic pressure. | 
Conclusions 
1. Heat is a limiting factor in controlling the processes which 
develop the substances that give rise to variation in osmotic pressure 
in potato sap. : 
2. Lowering temperature causes an increase in acidity, which 
in turn seems to be the controlling agent in the release of the 
enzymes which hydrolize starch and hemicellulose. : 
3. The carbohydrates hydrolized furnish the energy which 1s 
used by the potato while carrying on its metabolism during cold 
storage. 
This work was undertaken at the suggestion of Dr. WILLIAM 
Crocker to whom I am greatly indebted for much valuable 
assistance. 
Unrversity or Norto Daxora 
Granp Forks, N.D. 
* For the acid determinations I am indebted to Dr. SopHIA ECKERSON. 
