Nov. i, 1920 



Effect of Drying Disinfected Seed Wheat 



239 



except to one trained to distinguish the weakened and injured seedlings, 

 the germination counts will not give an accurate measure of field results. 

 In soil, the percentage of germination of injured samples will be much 

 lower, of course, depending on the nature of the soil and the difficulty 

 encountered by the seedling in emerging from it. 



Table XIV. — Percentage of germination of Little Club wheat and Coast barley treated 

 with O.I per cent formaldehyde solution and sealed in bottles after drying for various 

 periods 



LITTLE CLUB WHEAT 



COAST BARLEY 



7... 

 7 a -. 



96 



a Germinated in soil; all others germinated on blotters. 



This second experiment also demonstrated that this phenomenon is 

 shown by barley as well as wheat. For barley, as for wheat, the maxi- 

 mum injury was to those samples dried for 5K an d 9 hours, with de- 

 creased injury to the samples dried longer before sealing. 



In subsequent experiments on wheat treated with both 0.1 per cent 

 and 0.2 per cent solution, then dried and sealed, there was always this 

 upward gradation in injury from a maximum below 24 hours of drying 

 to almost normal germination in samples dried for several days and then 

 sealed. However, in the experiment illustrated in Plate 40, there was 

 severe, though lessened, injury to the sample dried three days before 

 being sealed in the bottles. 



For a long time after the first results of this nature were obtained they 

 seemed inexplicable. After the later studies of the behavior of formalde- 

 hyde and the manner in which it injures seeds through the volatilizing 

 of its polymer, paraformaldehyde, an explanation suggested itself. 

 In the first place, it is obvious from what we know of paraformalde- 

 hyde that it did not form on the dampest seeds. Hence, those seeds 

 sealed after one hour showed no injury because at the end of that time 

 they were still damp. Paraformaldehyde formed on those dried more 

 thoroughly, and the gas resulting from its evaporation at once began to 

 diffuse away from around the seeds because they were thinly spread. 



