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WM. CROCKER 
for foods and enzymes are present in almost full force for some years 
after viability is lost. 
Ewart^ says "Longevity . . . depends upon how long the inert 
proteid molecules into which the living protoplast disintegrates when 
drying, retain the molecular grouping which permits of their re- 
combination to form the active protoplasmic molecules when the seed 
is moistened and supplied with oxygen." In this form of statement 
Ewart's theory is quite beyond experimental investigation. Groves^ 
and I have suggested that loss of viability in seeds approaching 
the air-dry condition is due to the slow denaturing, or coagulation, of 
certain protoplasmic proteins of the embryo — a statement resembling 
Ewart's in some ways but one capable of experimental study. The 
extreme lability of protoplasmic proteins as shown by Lepeschkin^** 
would suggest their being denatured far sooner than such proteins 
as make up or at least are associated in the main with the rather 
stable oxidizing and digestive enzymes. 
The evidence for this hypothesis was gained by studying the rela- 
tion between temperature and life duration of wheat seeds at tem- 
peratures ranging from 50° to 100° C, since this range of temperature 
gives life durations convenient for experimental purposes. 
The following results of this work show the likeness between life 
duration of wheat grains (Triticum sativum) at temperatures above 
50° C. and the coagulation time of proteins. At given temperatures 
the life duration fell with increased water content. When the log- 
arithms of the life duration in minutes was plotted on the abscissae 
and the temperatures in degrees centigrade on the ordinates a straight- 
line curve resulted showing that life duration is a logarithmic function 
of the temperature. The formula applied by Lepeschkin as a time- 
temperature formula for the coagulation of proteins as well as a 
temperature-life duration formula for imbibed cells applies also as 
a temperature-life duration formula for wheat grains (T ~ a — b logZ, 
in which T = degrees centigrade, a and b are constants and Z is time 
in minutes). For rise in temperature the rate of loss of longevity rises 
much faster than assumed by the van't Hoff law — a law applying 
rather generally to the rate of chemical reactions in vitro as well as to 
many processes in the living organism. While this law assumes 
increased speed of two to three fold for a rise of 10° C, wheat containing 
3 Ewart. On the Longevity of Seeds. 210 pp. Victoria, Australia, 1908. 
10 Lepeschkin. Ber. Deutsch. Ges. Bot. 30: 703. 1913. 
