236 



Journal of Agricultural Research 



Vol. XX, No. 3 



well-spread seed. Throughout subsequent tests, continued almost daily 

 for two weeks, the dried samples gave stronger reactions than the damp 

 ones, which, after about six days, showed no more than the extract from 

 the untreated control. The dried samples soon gave about equal reac- 

 tions. The results of the first two tests, which showed that there was 

 more formaldehyde on the seed dried in the open bottle than on that 

 spread on towels, confirm the conclusion already drawn from the germi- 

 nation data — that is, that more paraformaldehyde remained on the seed 

 dried without aeration because the formaldehyde gas could not escape 

 readily from around the seed. Gradually, however, this gas escaped 

 and the quantity present, as shown by the reaction, decreased to that 

 of the aerated sample. 



Table XII. — Percentage of germination of Coast barley treated with 4.5 per cent formalde- 

 hyde solution and dried under different conditions and for varying periods of time 



"These increased germinations after 42 days, though they apparently indicate recovery, are probably 

 due to more favorable germination conditions. 



From these data it appears that any prediction or explanation of post- 

 treatment injury must be based on the humidity of the atmosphere 

 immediately surrounding the seed and on the manner of drying the seed 

 as affected by its aeration. Temperature may also be an important 

 factor, but its relation to the problem has not yet been determined. 

 Temperature or some other variable must account for the fact that, 

 with all the foregoing conditions controlled, repetitions of experiments 

 do not always give the same results. For instance, in Table XI injury 

 is shown to thinly spread wheat after a subjection to a 0.2 per cent 

 solution of formaldehyde, while less injury is shown in the data in 

 Table X. In these cases the differences may possibly be chargeable to 

 the fact that different samples of different varieties of wheat were used. 

 In one experiment no greater injury occurred to seed dried in an open 

 bottle than to that thinly spread on the table beside it. Such excep- 

 tions are only occasional, but they indicate that certain apparently 

 minor factors have not yet been ascertained. 



