1912] PEIRCE—RESPIRATION 109 
of heat given off. The flasks used in 1908 were inferior as insula- 
tors to those in use in 1911; hence the 1908 figures are not as high 
as they would have been if more efficient insulators had been 
employed. So far as these figures show, therefore, it appears that 
the amount of heat liberated by germinating peas decreases with 
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Fic. 7.—Heat yields of peas of different ages 
their age. If this be true, the amount of heat liberated may then 
be used as the index of the age or freshness of seeds. 
The accompanying diagram (fig. 7) represents the above figures 
in the form of curves. The difference between the curves of 1907 
peas in 1908 and 1o11 is even more striking than the figures on 
which they are based. 
It does not by any means follow that the other processes of the 
