242 Journal of Agricultural Research vol. xx, No. 3 



SUMMARY 



(i) No seed injury was produced by treating wheat with either a o.i 

 per cent (i to 40) or a 0.2 per cent (1 to 20) solution of formaldehyde if 

 the seed was germinated immediately after treatment. 



(2) If treated seed is held several days or more before sowing, it is 

 severely injured if allowed to dry without thorough aeration during the 

 storage period. If, however, the seed remains damp, it suffers no injury 

 from a 0.1 per cent solution and can be so kept indefinitely or until 

 attacked by molds. 



(3) Post-treatment injury is usually cumulative, increasing in degree 

 the longer the seed is stored. 



(4) This seed injury upon drying apparently is due to a deposit of 

 paraformaldehyde on the seed, which forms as the formaldehyde solution 

 evaporates. The solid paraformaldehyde, being volatile, is constantly 

 breaking down into formaldehyde gas. This gas, being thus concentrated 

 and held so close to the seed, penetrates it slowly, probably going into 

 solution in the testa. 



(5) The degree of post-treatment injury depends primarily on atmos- 

 pheric humidity during the storage period. In atmospheres damper than 

 70 per cent humidity the treated seed can be kept indefinitely without 

 ill effects. In those of 70 per cent and less there is decided injury, which 

 is most severe in the intermediate humidities, gradually decreasing in the 

 lower ones until seed stored in an absolutely dry chamber is almost unin- 

 jured. 



(6) No paraformaldehyde formed upon the evaporation of formalde- 

 hyde solutions placed in these damper chambers in which no seed injury 

 occurred, but it did form in all solutions evaporated in desiccators of 60 

 per cent humidity and less, the quantities by weight increasing as the 

 atmosphere became drier. Therefore, seed injury in the desiccators was 

 not determined by the quantity of paraformaldehyde formed on the seeds 

 in each. 



(7) Untreated wheat, when placed in desiccators of varying atmos- 

 pheric humidities alongside of evaporating, undiluted 36.2 per cent 

 formaldehyde solutions, was least injured in the absolutely dry chamber 

 and was entirely killed by the formaldehyde vapor in all the chambers 

 damper than 30 per cent humidity. 



(8) In view of the facts that treated seed is less injured in very dry 

 atmospheres than in intermediate ones and that untreated seed is least 

 injured by formaldehyde fumes in the dry atmosphere of desiccators, it 

 is considered probable that formaldehyde does not enter seeds as a gas or 

 in the solid polymeric form but in solution in the seed coats. For the 

 maximum seed injury to occur as a result of drying after formaldehyde 

 treatment, therefore, there must be an optimum atmospheric humidity 



