26 Nebraska Agricultural Exp. Station Researc h Bul. 16 
been placed in the killing and fixing solution while still in a 
frozen condition. It is probable, therefore, that killing took 
place before there could be any material readjustment of the 
living matter. It was thought, however, that the change in 
color of embryonic tissues and other plant tissues and the soft 
watery condition characteristic of all tissues which have been 
frozen to death indicates that some physical or chemical change 
has been brought about. Even tho the change in color of the 
embryo of a corn kernel after freezing may be due to the 
action of some enzyme or of bacteria, the fact remains that a 
change has been effected which makes possible such action. The 
instance cited by Detmer (1893) of pieces of frozen red beet 
giving up their coloring matter and sugar when placed in 
water, while these substances are tenaciously retained by the 
unfrozen material, adds some evidence of a physical or chemical 
change. The soft, watery condition of plant tissues after freez- 
ing also appears to be the result, at least in part, of disorganiza- 
tion of the cellular material, and not entirely to a withdrawal of 
the water from the cells. That this is true is drawn from the 
observations of Miiller-Thurgau (1886) and Mez (19051 re- 
garding the formation of ice within the cells when the tissues 
are supercooled or frozen rapidly. If the extraction of water 
from the cells was the only cause of the watery condition in 
question, tissues which are frozen rapidly or supercooled, so 
that crystalization takes place largely in the cells, should not 
exhibit this condition. But this water-soaked condition is 
characteristic of frozen tissues whether the freezing has been 
done rapidly or slowly. 
Altho chemical changes have not been established by 
chemical analysis, it seems certain that changes take place 
within the protoplasmic and nuclear contents as a result of 
freezing and that these changes make it impossible for the 
processes of life to continue. 
The withdrawal of water from the cells bv freezing has 
been considered by many as the cause of death. It was noted 
that in moist corn kernels, water was withdrawn from the 
tissues and ice formed in masses and sheets in space surrounding 
or separating different tissues, and that death usually accom- 
panied such ice formation. It was also noted that air-dry corn, 
which contains from 10 to T2 per cent of moisture, was not 
frozen, at least its vitality was not injured, and according to 
the observations of Brown and Escombe (189T-8), Adams (1905), 
Thiselton-I)yer (1S99), and others it was not injured even when 
exposed for several hours to the temperature of liquid air or 
