1 9 



Li ~ 



earlier experiments in which the samples were taken as the seed left 

 the machine and placed in small sample bags. In these bags the seed 

 on the outside cooled rapidly, and the result is exactly what one would 

 expect, namely, that, as in the case of the sacked seed, very nearly 

 complete mortality is obtained at 51 C., but that odd worms survive 

 even at 55 C. Finally, the figures in the last column show the 

 results of cooling the seed rapidly after treatment. In this case a 

 sample of seed was taken as it left the machine and immediately 

 spread out on the ground. In this way its temperature fell below 

 45 C. in less than half a minute. The result of this treatment is very 

 marked indeed, nothing approaching complete mortality being reached 

 till 60 C. and odd worms surviving at temperatures even of 65 C. 



We can now perhaps attempt an answer to our original question. 

 If the seed is maintained for five minutes or more at the temperature 

 in question, the worms are killed at temperatures from about 52 C. 

 upwards. If, however, the seed is immediately cooled after reaching 

 its maximum, a temperature of at least 60 C. is necessary. The 

 temperature in both these cases is the maximum temperature actually 

 reached by the seed containing the worms. 



From this question we can now turn to the correlated question, 

 ' What is the minimum temperature that damages the seed ? ' 

 The same difficulties are met with in answering this question as in 

 answering the former. Table II gives a similar set of figures for 

 the germination of treated cotton seed as Table I gave for the mortality 

 of the worms. In order to make it possible to compare the figures 

 from different experiments in which widely different qualities of seed 

 were used, the figures given are not the actual percentage germinations 

 of the treated seed, but are these percentage germinations compared 

 to the percentage germination of the untreated seed of the same 

 sample, the latter being taken as 100. Black lines have been placed 

 to the right of each column where the seed has undoubtedly been 

 damaged. It must be borne in mind that as the seed used in these 

 experiments was mostly of poor quality its germination was, very 

 variable, and it is therefore difficult to be certain whether any 

 individual sample has actually been damaged or not. In general, 

 seed giving a germination of 85 per cent or less, calculated as explained 

 above, has been considered as damaged ; but in view.of the fact that one 

 sample gave a germination 42 per cent better than the untreated seed , 

 one cannot be absolutely certain that the seed is damaged, even when 



