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BOTANICAL GAZETTE 



[march 



the coefficient is small and compares in magnitude with the value 



* 



found by other workers on plant tissue. The range in the value of 

 the coefficients is small, as indicated by the fact that the data fall 

 on comparatively smooth curves. The coefficient Q I0 as calcu- 

 lated from the data (for 12 per cent moisture) in table II by the 

 method of least squares is 10.14. When the temperature and 

 time-differences in formula 2 are so small that they are comparable 

 with the errors of observation then the numerical evaluation of 

 Q I0 becomes highly inaccurate. But when the time and tempera- 

 ture differences are large enough to render ineffective the errors 

 of observation, then the calculated coefficient Qi is comparable 

 with the value obtained by the method of least squares. 



The coefficient Q J0 for 9 per cent moisture content was found to 

 be 9.23 as calculated by the method of least squares from the 

 data in table III. Similarly, the coefficient for 17.5 per cent mois- 

 ture content was found to be 16.45 when calculated by the same 

 method, using the 4 highest time observations in table IV. The 

 4 lowest time observations were ignored on account of the inaccu- 

 racy introduced by the time required for the seeds to attain the 

 temperature of the bath, as previously explained. 



A number of longevities have been calculated by formula 3 

 for the low temperatures at different moisture contents. With 

 the relatively short range of temperatures used in these experi- 

 ments, considerable error may appear in predicted longevities, 

 especially at low temperatures. When such calculated longevities 

 are compared with observed values, they are found usually to be 

 considerably too large, indicating that other processes may also 

 be effective in causing loss of viability. Since hard-coated seeds 

 have long vitality records, it seems quite possible that this is 

 related to the absence of oxygen and low water content. 



Much more work is needed to determine how nearly one can 

 thus approximate longevities from measurements made at high 

 temperatures. Determinations should be made on the life duration 

 of seeds with low moisture content. Also similar determinations 

 should be made for a long-lived seed, such as sweet clover, for 

 which we have reliable records of longevity, as well as short-lived 







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