Nov. i, 1920 



Effect of Drying Disinfected Seed Wheat 



229 



HUMIDITY PERCENTAGE 

 IOO 90 80 70 60 SO 40 30 ZO /O O 



cators having humidities varying from 40 per cent to dryness, being very 

 faint in the former and increasing to a considerable quantity in the 

 latter. The next day a faint opaqueness showed in the dishes of solution 

 in the 50 per cent, and on the day following in those in the 60 per cent 

 humidity, at which time all those in the drier chambers were entirely 

 dry. It is indeed interesting that although no solid ever formed in the 

 70 per cent humidity, this dish, as in the preceding experiment, evap- 

 orated to dryness but left no residue. The volume of liquid left unevap- 

 orated in the dishes in the damper atmospheres was greater the higher 

 the humidity (Table IX). 



When the residue of paraformaldehyde left after the evaporation of 

 the solutions in the drier desiccators was weighed, it was found in both 

 experiments that, in general, 

 the quantity formed varied in- 

 versely with the humidity of 

 the atmosphere (Table IX). & 

 Since the degree of injury to y^tg 

 the stored treated wheat was 

 in the opposite order, it was at 

 once evident that the factor 

 causing the progressive varia- 

 tion in seed injury in the des- 

 iccators was not the quantity 

 of paraformaldehyde formed on 

 the seeds. Before this point is 

 considered further, however, 

 the results of a contempora- 

 neous experiment should be 

 presented. When the dishes 

 of formaldehyde solution were 

 placed in the desiccators to be evaporated , small quantities of untreated 

 seed were inserted at the same time to determine if formaldehyde 

 gas would evaporate in each humidity to produce sufficient concen- 

 trations in the different atmospheres to kill the wheat exposed to them. 

 When samples of this wheat were germinated at the end of the 

 experiment, surprising results were obtained. It was found after both 

 experiments that there was no germination of this seed from desiccators 

 of 70 per cent humidity and above and that the germination percentages 

 of seed from the drier atmospheres varied inversely with the moisture 

 percentage, the seed being least injured by the formaldehyde fumes from 

 the solution over concentrated acid. All these secondary experiments 

 on the dependence of the behavior of formaldehyde and its solutions on 

 atmospheric humidity are summarized in Table IX. 



In brief, then, the facts are these: The seed injury resulting after 

 treatment with a 0.1 per cent solution, which occurs as the result of drying 



to 



2D 



I.S 



Fig. 4. — Graph showing the relation between humidity 

 of the air and seed injury as indicated by rate of growth 

 of germinated seedlings. 



