1052 A. F. Vass . 
on the precipitation of the proteids when the solutions were frozen. He 
assumed that killing from cold may be due to the precipitation of the 
proteids resulting from the concentration of salts in the sap as the water 
is removed to form the ice crystals within the intercellular spaces. 
Heckel (1909) noted that anesthetics and freezing liberated coumarin 
very rapidly from certain plants, and that the characteristic odor was 
apparent from green plants in a few moments after freezing, whereas 
ordinarily it is not apparent until after the plants have become more or less 
dried. This seemed to indicate that freezing and drying affected the plant 
in much the same way. 
In studying the relation between the density of cell saps and the freezing 
points of leaves, Ohlweiler (1912) noted that the extreme differences in 
sap density are generally accompanied by corresponding resistance to 
freezing. He found that when the cell structure was essentially the 
same, the density of the cell sap of the species would indicate its relative 
hardness. 
Lepeschkin (1912) concludes that death in plant cells is preceded by 
a decomposition of the less stable protein compounds and later their 
coagulation. Capillary forces may play an important part in their 
coagulation, which in turn sets free energy that leads to the breaking down 
of the weaker compounds. 
Maximow (1914), in his very excellent work in freezing sections of 
plants in solutions of various strengths of both erganic and inorganic 
substances, found a remarkable protection to be exerted whenever the 
eutectic point of the substances did not lie too near the freezing point and 
whenever the substance was not exceedingly. toxic. When the sections 
were immersed in these solutions and immediately frozen, as much pro- 
tection was noted as when they were permitted to remain in the solution 
for several hours. The protective action was not in direct proportion to 
the osmotic pressure and the lowering of the freezing point, for it was 
considerably more rapid than the latter changes. Since the protective 
action did not depend on the time the plant was in the solution nor on 
the permeability of the protoplasm, Maximow concluded that the action is 
on the outer layer of the protoplasm, and that the withdrawal of water 
seems to be limited to the plasma membrane. 
Chandler (1913) was able to reduce the killing temperature of plant 
tissue by increasing the sap density of the tissue. In the case of unripe 
