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



solution on the seed and the formation of paraformaldehyde — came from 

 the difference in the degrees of injury sustained by the original samples 

 of treated wheat dried in the greenhouse, laboratory, and refrigerator 

 (see Tables I and II and PI. 37). The dried seed from the greenhouse, 

 where the atmosphere was warmest and most humid, was the least 

 injured. From our knowledge of the unstable constitution of para- 

 formaldehyde it seemed probable that it would form but slowly if at all 

 in the presence of moisture. Work, therefore, was undertaken to deter- 

 mine whether the degree of this seed injury resulting from drying after 

 treatment depended on the humidity of the atmosphere at the time of 

 drying. 



The moisture content of the three dried samples of treated seed from the 

 greenhouse, laboratory, and refrigeratorw as determined after six weeks of 

 storage. By drying the seed to constant weight in an electric oven at a 

 temperature of 95 ° C. it was found that the seed dried in the laboratory 

 contained 13.28 per cent moisture, that from the refrigerator 15.35 P er 

 cent, and that from the greenhouse 16.63 per cent. Samples of each 

 lot were then tested qualitatively by means of Tollen's silver-mirror 

 aldehyde test for the presence of formaldehyde. A distinct difference 

 was obtained. The precipitate appeared most rapidly and was most 

 dense in the laboratory-stored seed which had the small moisture con- 

 tent, while it was decidedly least in the greenhouse-stored sample with 

 highest moisture percentage. These facts then suggested that the for- 

 mation of paraformaldehyde is dependent on the dryness of the atmos- 

 phere. Since all evidence points to the fact that seed injury upon dry- 

 ing after treatment is dependent on the formation of paraformaldehyde 

 on the seeds as the solution evaporates, it follows that seed injury may 

 vary inversely with the moisture content of the surrounding atmosphere. 

 So far as the three seed lots of this original experiment were concerned, 

 this was true, for the greenhouse where least injury occurred was most 

 humid and the laboratory where injury was most extreme was driest. 

 However, more evidence was necessary, and this could be obtained only 

 by storing treated seed under controlled and definitely known moisture 

 conditions. 



Atmospheric humidities varying by 10 per cent intervals from satura- 

 tion over water to dryness over concentrated acid were produced in 

 desiccators by the use of sulphuric acid dilutions. 1 Given the specific 

 gravity of the solutions necessary to produce the desired atmospheres 

 (PI. 38, B), they are easily made up in quantity by means of specific 

 gravity spindles and kept in stock bottles (17, p. 114). 



'Since these experiments were completed, a paper written by Neil E. Stevens (is) has come to the 

 writer's attention in which a table is given showing the approximate humidities obtained in desiccators 

 containing aqueous solutions of sulphuric acid of various specific gravities. These differ somewhat 

 from those given by Woodworth (17, p. 114), and the method is described more fully and the data 

 given are more complete. 



