20 Nebraska Ackht lti ral Exp. Station Research Bul. 16 
death, the effect of such ice formation upon the cell structure of 
the kernel embryo was studied. It was thought that such micro- 
scopic studies of frozen embryos might give some clue concern- 
ing the cause of death by freezing. 
Figures 10 and 11 are microphotographs of cross sections of 
the primary root of frozen and unfrozen corn embryos respec- 
tively. The grain represented by Figure 10 had been frozen for 
48 hours at a temperature of 5° F. below zero, and had a 
moisture content of 35 per cent. Figure 11 represents grain 
from the same ear which had not been frozen. A large number 
of frozen and unfrozen grains were sectioned and examined 
microscopically. No rupture of cell walls or other cvtological 
effect of freezing and ice-formation within the kernels was 
apparent. 
CHEMICAL EFFECTS OF FREEZING 
Opportunity did not offer for an exhaustive study of chemi- 
cal changes involved in freezing injury. However, an ordinary 
fodder analysis was made in triplicate of both frozen and un- 
frozen immature grain. A composite sample of shelled corn 
containing 37 per cent moisture was divided into two parts. 
One portion was dried immediately. The other was frozen for 
three days at a temperature of 0° F. At the end of three more 
days the embryos of the frozen grain had turned dark. This 
grain was dried and both samples anajized. The results are 
given in Table 4. The differences recorded are probably within 
the limits of experimental error. Doubtless some chemical 
change has taken place, otherwise the tissues would not have 
darkened in color. A germination test of the frozen and un- 
frozen seed showed 0 and 100 per cent viability. 
Table 4 — Composition of frozen a .in unfrozen seed com 
Character of grain 
Composition of moisture-free grain 
Crude 
protein 
Nitrogen- 
free extract! 
Fat 
Crude 
fibre 
Ash 
Per cent 
Per cent 
Per cent 
Per cent 
Per cent 
Unfrozen 
13.13 
78.65 
4.54 
2.30 
1.38 
Frozen 
12.94 
78.61 
4.63 
2.37 
1.45 
Ratio of unfrozen to frozen 
.985 
.999 
1.02 
1.03 
1.05 
These analyses were made under the direction of F. W. Upson. Station 
Chemist. 
